MXPA06008424A - Frame synchronization and initial symbol timing acquisition system and method - Google Patents

Abstract

A robust initial frame detection and symbol synchronization system and methodology are provided. In particular, a first pilot is employed in conjunction with three acquisition stages. In the first stage, an attempt is made to observe the leading edge of the correlation curve associated with the first pilot symbol. In the second stage, a determination is made as to whether a leading edge was detected in the first stage by attempting to observe a flat portion and/or trailing edge of the correlation curve. Furthermore, during this second stage, a frequency loop can be updated to account for frequency offset. The third stage is for observing the trailing edge of the curve if it was not already observed in stage two. Upon detection and confirmation of receipt of the first pilot, a second pilot can subsequently be employed to acquire fine symbol timing.

Description

SYSTEM OF SYNCHRONIZATION OF FRAME AND ACQUISITION OF TIMING OF INITIAL SYMBOL AND METHOD.

FIELD OF THE INVENTION The present invention relates, in a general way, to data communication, and more particularly, to the acquisition and synchronization of signals.

BACKGROUND OF THE INVENTION There is a growing demand for high capacity and reliable communication systems. Nowadays, data traffic originates mainly from mobile phones as well as desktop or laptop computers. As time passes and technology evolves, it is predictable that there will be an increase in the demand for other communication devices, some of which have not yet been developed. For example, devices currently not conceived as communication devices such as household appliances as well as other consumer devices, will generate large amounts of data for transmission. In addition, current devices such as mobile phones and personal digital assistants (PDA), among others, will not only be the most prevalent but will also demand an unprecedented bandwidth to support large and complex interactive and multimedia applications. Although data traffic can be transmitted in a wired manner, the demand for wireless communication is currently and will continue to take off. The increasing mobility of people in our society requires that the technology associated with it be portable as well. In this way, today many people use mobile phones and PDAs for the transmission of voice and data (for example, mobile network, email, instant messaging ...). In addition, a growing number of people are building wireless home and office networks and wireless hot spots are also expected to allow Internet connectivity in schools, cafeterias, airports and other public places. Moreover, there continues to be a large-scale movement towards the integration of computer and communication technology in transport vehicles such as cars, boats, airplanes, trains, etc. In essence, as computing and communication technologies continue to become increasingly ubiquitous, demand in the wireless realm in particular will continue to increase as this is often the most practical and convenient means of communication. In general, the wireless communication process includes an emitter and a receiver. The transmitter modulates data on a carrier signal and subsequently transmits that carrier signal on a transmission medium (eg 'radio frequency'). The receiver is then responsible for receiving the carrier signal on the transmission medium. More specifically, the receiver works by synchronizing the received signal to determine the start of a signal, JThe information contained in the signal, and whether or not the signal contains a message. However, synchronization is complicated by noise, interference and other factors. Despite these obstacles, the receiver must still detect or identify the signal and interpret the content to allow communication. Currently, there are many conventional extended frequency modulation technologies that are being used. With these technologies, the power of a broadband information signal is extended or enlarged through a large transmission frequency band. This extension or propagation is advantageous at least because those transmissions are generally immune to system noise due to the small spectral power density. However, a known problem with that conventional system is that the propagation of the multipath delay causes interference between a plurality of users. One of the standards that is rapidly gaining commercial acceptance is multiplexing by orthogonal frequency division (OFDM). The OFDM is a parallel transmission communication scheme where a high-speed data stream is divided over a large number of lower rate streams and transmitted simultaneously over multiple subcarriers separated at particular frequencies or tones. The precise separation of the frequencies provides the orthogonality between the tones. Orthogonal frequencies minimize or eliminate crosstalk or interference between communication signals. In addition to high transmission speeds and resistance to interference, a high spectral efficiency can be obtained since the frequencies can be superimposed without mutual interference. However, a problem with OFDM systems is that they are especially sensitive to receiver synchronization errors. This can lead to a degradation of system performance. In particular, the system may lose orthogonality between subcarriers and thus users of the network. To preserve the orthogonality, the transmitter and receiver must be synchronized. In sum, the synchronization of the receiver is of utmost importance for successful OFDM communications. Accordingly, there is a need for a novel system and method for fast and reliable initial frame synchronization.

SUMMARY * •: The following presents a simplified summary to provide a basic understanding of some aspects and modalities described hereinafter. This summary is not an exhaustive general list. Nor is it intended to identify key / critical elements. The sole purpose is to present some concepts or principles in a simplified form as a prelude to the more detailed description presented below. Briefly described, several systems and methods are presented here to facilitate the initial acquisition of timing of frames, frequency and symbols. Target systems and methods acquire initial frame synchronization by detecting a first pilot symbol (e.g., a TDM pilot symbol within an OFDM environment). To facilitate the detection of the pilot symbol, a delayed correlator may be employed. The delayed correlator receives a flow of input samples, correlates the input samples with delayed versions of them, and generates a thousand detection metrics or correlation outputs that can be used to detect the pilot's symbol. When the detection metrics or correlation values are observed within a period of time they produce what is known here as a correlation curve that includes a leading edge, a flat area, and a trailing edge, where • the correlation curve is an energy distribution output by the delayed correlator. The detection of the first pilot symbol can be divided into three stages: detection of the leading edge of the correlation curve, confirmation of the detection of the leading edge by detecting or observing a portion of the flat area of the correlation curve, and finally detection of the back edge of the correlation curve. In the first stage, an attempt is made to observe or detect the leading edge of a correlation curve. The magnitude of the correlator's metric output or some function of it (for example, the square of the output) is compared to a programmatic threshold. If the correlator output exceeds the threshold for a predetermined number of consecutive input samples (e.g., 64) the system or method can advance to the second stage. In the second stage, an attempt is made to confirm the detection of the leading edge and observe a flat area of the correlation curve. Several counts or counters can be used to facilitate this and other functionality. For example, a first count may be incremented each time a new sample is received and correlated, a second count may increase each time the correlator output exceeds the same threshold. Moreover, a third count can be used to track the number of consecutive times that the correlator output is below the threshold. Those counters can then be used to determine, among other things, whether a false front edge was detected due to noise, for example. If a false positive was detected, a new leading edge will have to be located in stage one. If a false front edge is not detected, the system or method remains in stage two for a predetermined period of time or until a consistent trailing edge is observed, for example if the leading edge was detected later. It should also be appreciated that at least one additional synchronization functionality may be provided during this second step. In particular, an accumulator of the cycle or frequency circuit (eg, cycle or synchronized circuit by frequency, cycle or automatic frequency control circuit) may be periodically updated to zero in or detect a deviation or change of frequency. In addition, if the trailing edge of the pilot correlation curve is detected here a case of time may be saved before detection thereof for use by a fine timing system or method. Stage three belongs to the detection of the back 'bordé' if it was not already observed in stage two: Here at least one counter can be used to follow the number of consecutive times that the output of the correlator is less than the threshold. If the value of the count is greater than a predetermined or programmed value (for example, 32), then the trailing edge has been detected. A case of time corresponding to the time just before the detection of the trailing edge can also be saved or saved. This time case can then be used by the next wireless symbol (for example an OFDM symbol), which in an exemplary mode is a second TDM pilot. According to a particular embodiment, this time case may correspond to the 256th sample of the second pilot symbol. However, if the count is less than the programmable threshold or a consistent back edge was not observed during the delay period (eg, 1024 input samples), then the system or method can readjust the counters and the accumulator. frequency and start looking for another leading edge in the first stage. In a particular example, after successful detection of the first TDM pilot 1, the .TDM pilot 2 can be used to acquire the timing of fine OFDM symbols. Subsequently, an attempt is made to decode the OFDM symbol data. The cycle or frequency circuit may operate in a tracking mode after detection of the first TDM symbol. If the decoding of the OFDM symbol data fails then it is assumed that the frequency control circuit failed coverage and the entire acquisition process is repeated with the next frame or superframe. In particular, a method for initial frame detection and synchronization is described herein. First, a flow of input signals is received at least some of which is associated with a pilot symbol. The correlation outputs are generated by forming a correlation curve from the signals and delayed copies thereof. A potential leading edge of the correlation curve is detected from the correlation outputs. Subsequently, the detection of the leading edge is confirmed and the trailing edge of the correlation outputs is detected. Similarly, a frame detection and synchronization system comprising a delayed correlator component, a leading edge detection component, a confirmation component and a rear edge component is described herein.The component of the delayed correlator receives a flow-of input samples, correlates the input samples with delayed versions thereof, and generates a plurality of outputs that form a correlation curve. The front edge detection component receives the outputs, compares the outputs with a threshold and generates a signal if it detects a potential leading edge of the correlation curve. The confirmation component compares the additional outputs with the threshold to confirm detection of the leading edge upon receipt of the signal from the leading edge detection component. The rear edge component receives a signal from the confirmation component and compares the additional outputs to locate the trailing edge of the correlation curve. To achieve the above and related goals, certain aspects and illustrative modalities are described herein in relation to the following description of the attached drawings.IT IS.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other aspects will become apparent from the following detailed description and the accompanying drawings briefly described herein below. Figure 1 is a block diagram of a common frame detection system. Figure 2a is a graph of a correlation curve in a single ideal trajectory environment. Figure 2b is a graph of a correlation curve in a real multipath environment, Figure 3 is a block diagram of a modality of a confirmation component. Figure 4 is a block diagram of one. modality of a component of the trailing edge. Figure 5 is a block diagram of a one-component mode of the delayed correlator. Figure 6 is a block diagram of one embodiment of a fine screen detection system. Figure 7 is a flow chart of an initial common frame detection methodology. Figure 8 is a flow diagram of a leading edge detection methodology. Figure 9 is a flow diagram of a flat zone detection and front edge confirmation methodology. Figure 10a is a flowchart of a flat zone detection and front edge confirmation methodology.

Figure 10b is a flow diagram of a flat zone detection and front edge confirmation methodology. Figure 11 is a flow diagram of a back edge detection methodology. Figure 12 is a flowchart of a frame synchronization methodology. Figure 13 is a schematic block diagram of an operating environment suitable for various aspects and modalities. Figure 14 is a diagram of one modality of a superframe structure for use in an OFDM system. Figure 15a is a diagram of a modality of a TDM pilot 1. Figure 15b is a diagram of a modality of a TDM pilot 2. Figure 16 is a block diagram of a fingernail mode of a TX data processor and pilot in a base station. Figure 17 is a block diagram of an embodiment of the OFDM modulator in a base station. Figure 18a is a diagram of a time domain representation of the TDM pilot 1. Figure 18b is a diagram of the time domain representation of the TDM pilot 2.

Figure 19 is a block diagram of a channel modeling and estimation unit mode in a wireless device. Fig. 20 is a block diagram-of the modality mode of the symbol timing detector that performs the timing synchronization based on e? -the OFDM symbol of the pilot 2. Fig. 21a is a timing diagram of the TDM pilot 2 process of the OFDM symbol Figure 21b is a timing diagram of a derivation channel impulse response L2 of the IDFT unit Figure 21c is a graph of the energy of the channel derivations at different window start positions Figure 22 is a diagram of a pilot transmission scheme with a combination of TDM and FDM pilots.

DETAILED DESCRIPTION Various aspects and modalities are described with reference to the accompanying drawings, where similar numbers refer to similar elements corresponding thereto. It should be understood, however, that the drawings and the detailed description thereof are not intended to limit the modalities to the particular forms described. Instead, it is intended to cover all modifications, equivalents and alternatives. As used in this application, the terms "component" and "system" are intended to refer to an entity related to a computer, whether it be physical computing components or hardware, with a combination of physical computing or hardware components and programs and programming systems or software, programs and systems of programming or software or programs and systems of programming or software in execution., a component can be, but not limited to, a process that runs on a processor, a processor, an object, an executable, an execution string, a program and / or a computer (for example, desktop, laptop, mini, hand ...). By way of illustration, both an application that runs on a computing device and the device itself can be a component. One or more components can reside within a process and / or the execution chain and a component can be located on a computer and / or distributed between two or more computers. In addition, the aspects can be implemented as a method, apparatus or article of manufacture using the techniques of programming and / or standard engineering to produce programs and systems of programming or software, fixed instructions, physical components of computation or hardware or any combination of them to control a computer to implement the described aspects. The term "article of manufacture" (or alternatively, "computer program product") as used herein is intended to encompass a computer program accessible from any device, media or computer-readable medium. For example, computer-readable media may include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips ...), optical discs (e.g., compact disc (CD), versatile disc). digital (DVD) ...), smart cards, and instant memory devices (for example, cards, bars-). Additionally, it should be appreciated that a carrier wave can be used to carry computer-readable electronic data such as those used in the transmission and. Receiving email or to access' a network such as the Internet or a local area network (LAN). According to the corresponding description, several aspects are described in relation to a subscriber station. A subscriber or subscriber station can also be called a system, a subscriber unit., Mobile station, mobile station, remote station, access point., Base station, remote terminal, access terminal, user terminal, user agent or user equipment. A subscriber station can be a cellular telephone, a wireless telephone, a Session Initiation Protocol (SIP) telephone, a wireless local circuit (WLL) station, a personal digital assistant (PDA), a handheld device having wireless connection capability, or other processing device connected to a wireless modem. Turning initially to Figure 1, a frame detection system 100 'is described. More specifically, system 100 is a receiver-side subsystem associated with the synchronization of wireless symbol transmissions (eg, OFDM symbols). Synchronization generally refers to the processing performed by a receiver to obtain the timing of frames and symbols. As will be described in more detail, in the following sections, frame detection is based on the identification of pilot or training symbols transmitted at the beginning of a frame or superframe. In one embodiment, the pilot symbols are multiplexed pilots by time division (TDM). In particular, a first pilot symbol may be used for the approximate estimation of a frame in a symbol limit, inter alia, while it may be used a second pilot symbol to improve that estimate. The system 100 is mainly related to the detection of the first pilot symbol for frame detection, although it can be used in conjunction with the detection of other training symbols. The system 100 includes the component of the delayed correlator 110-, the component of detection of the leading edge 120, the confirmation component 130, and the component of detection of the trailing edge 130. The component of the delayed correlator 110 receives a stream of digital input signals from a receiver of the wireless device (not shown). The component of the delayed correlator 110 processes the input signals and produces detection metrics or correlation outputs (Sn) associated therewith. A correlation detection or output metric is indicative of the energy associated with a pilot sequence. The calculation mechanisms that generate the detection metrics of the flows of the input signals will be presented in detail below. The detection metrics are provided to a leading edge component 120, a confirmation component 130, and a rear edge component 140 for further processing. Turning briefly to Figures 2a and 2b, two exemplary diagrams illustrating pilot correlation outputs for 18 'purposes are provided. .. ', clarity as well as to facilitate the appreciation of the problems identified and overcome. The correlation diagrams describe an output of the correlator captured by the magnitude of the detection metric over time. Figure 2a describes the output of the correlator in a channel without noise. The output of the correlator clearly has a leading edge, a flat portion, and subsequently a trailing edge. Figure 2b illustrates an exemplary correlation curve in a subject channel for multipath purposes (e.g., the noise resides in the channel). It can be seen that there is a pilot, however this is obscured by the channel noise and multipath delay. Conventionally, a single threshold is used to detect a pilot symbol. In particular, the threshold is used to determine the start of a symbol when the correlation values are greater than the fixed or predetermined threshold In the ideal case of Figure 2a, the threshold would be set close to the value of the flat area and a symbol would be detected when it crosses that value, then a count would be started to determine the trailing edge, alternatively, the trailing edge could simply be detected when the curve values fall below the threshold. conventional methods and techniques are not effective in the real multipath environment As can be determined from Figure 2b, the leading edge can not be easily determined from the correlation values since multipath effects can cause values to propagate and noise It can darken the leading edge even further, which can result in a large number of false positive detections. Signal oparation is not conducive to counting samples to detect a trailing edge and noise will prohibit detection of a trailing edge when values fall below the threshold. The techniques described herein provide a robust pilot and frame detection system and method that is effective at least in a real-world multipath environment. Turning again to Figure 1, the leading edge component 120 can be employed to detect a potential leading edge of a correlation curve (for example, where the correlation curve represents a distribution of energy over time). The leading edge component 120 receives a series of values of the detection metric (Sn) of the component of the delayed correlator 120. Upon reception, the value is compared with a fixed or programmable threshold (T). In particular, a determination is made to see if Sn > = T If so, then the count of a counter- (eg, continuous count) is increased. Alternatively, if Sn < Then the counter is readjusted to zero, the counter therefore stores the number of consecutive correlation output values that are above the threshold, the leading edge component 120 checks this counter to ensure that it has been analyzed. A predetermined or programmed number of samples According to one modality, this may correspond to when the continuous count = 64. However, it should be appreciated that this value must be modified to optimize detection in a particular system in a specific environment. This technique is advantageous because it makes it less likely that a leading edge will be falsely detected as a result of initial noise or propagation, because the samples must remain consecutively above a threshold for a period of time. conditions, the leading edge component can declare the detection of a potential leading edge. a signal is provided to the confirmation component 130 indicating that. As the name suggests, the confirmation component 130 operates to confirm that the leading edge was actually detected by the leading edge component 120. After a leading edge, .. a long flat period is expected. Accordingly, if the flat portion is detected then this increases the confidence that the leading edge of the pilot symbol was detected by the leading edge component 120. However, then a new leading edge will be detected. Upon receipt of a signal from the leading edge component 120, the confirmation component 130 may begin to receive and analyze additional detection metric values (Sn). Turning to Figure 3, a block diagram of an exemplary implementation of the confirmation component 130 is described to facilitate clarity of understanding. The confirmation component 130 may include or be associated with a processor 310, a threshold value 320, an interval count 130, and a hit count 340, an execution count 350 and a frequency accumulator 360. The processor 310 is communicatively coupled with the threshold 320, the interval counter 330, the hit counter 340, the execution counter 350 and the frequency accumulator 360. In addition, the processor 310 can be operated to receive and / or recover correlation values Sn as well as to interact (e.g., receive and transmit signals) with the leading edge component 120 (Figure 1) and the trailing edge component 140 (Figure 1). The value . of the threshold 320 may be the same threshold that was used by the leading edge component 120 (Figure 1). Furthermore, it should be noted that although the threshold value is illustrated as part of the confirmation component 130 as a permanently encoded value, for example, the value of the threshold 320 can be received and / or retrieved outside the component to, among other things, facilitate the programming of that value. In brief, the interval corpuscle 330 can be used to determine when to update a frequency phase circuit to determine the frequency deviation using the frequency accumulator 360 as well as to detect the trailing edge. The hit count 340 can be used to detect the flat area of the symbol and the run count 350 is used to identify the trailing edge. Before the initial processing of the correlation values, the processor 310 can initialize each of the counters 330, 340 and 350, as well as the frequency accumulator 360 to zero, for example. The processor 310 may then receive or retrieve a correlation output Sn and the threshold 420. The interval count 430 may then be incremented to note that a new sample has been received. Each time a new correlation sample is retrieved at the count of 23 • • -... • 430 intervals can be increased. The processor 3.10 s can then compare the correlation value "with • the threshold 320. If Sn is greater than or equal to the threshold, then the hit count can be increased." As for the execution count, this can be increased if. is less than the threshold 320, otherwise it is set to 0. Similarly to the leading edge, the execution count can thus indicate the number of consecutive samples below the threshold.The counting values can be analyzed to determine that a leading edge has been detected, if there was a false positive, or if the leading edge was lost in another way (eg obtained later), among other things. " In one embodiment, the confirmation component 130 can determine that the leading edge component 120 detected a false leading edge by examining the execution count and the hit count. Since the confirmation component should detect a flat area of the correlation curve where the values are greater than or equal to the threshold, if the count of hits is sufficiently low and the execution count is greater than a fixed value or the count of The correct answers and the execution count are substantially the same, so it can be determined that the noise may have caused an incorrect detection of the leading edge. In particular, it can be noted that the correlation values received are not consistent with what was expected. According to one modality, the determination of a false front edge can be made when the execution count is greater than or equal to 128 and the hit count is less than 400. '. A determination can be made by means of the confirmation component 130 so that the leading edge was lost or otherwise detected too late for the appropriate timing by again comparing the values of execution count and count of hits. In particular, if the count of hits and the count of execution are sufficiently large, that determination can be made. In a modality, it can be decided when the execution count is greater than or equal to 786 and the hit count is greater than or equal to 400. Of course, and as with all the specific values provided here, the values can be optimized or adjusted for a particular frame structure and / or environment. It should be appreciated that the confirmation component 130 can begin to detect the trailing edge of the curve while analyzing the planar zone to decide whether an appropriate leading edge was detected. If the trailing edge is detected, the confirmation component can be successfully completed. To detect the trailing edge, the interval count and the execution count can be used. As noted above, the interval count includes the number of input samples received and correlated. It is known that the length of the flat area has to be within a particular count. Accordingly, if after detecting a potential leading edge and receiving an appropriate number of samples from the flat area there is some evidence of a trailing edge, then the confirming component can declare the detection of the trailing edge. The evidence of a trailing edge can be provided by the execution count, which counts a number of consecutive times that the correlation value is below the threshold. In one embodiment, the confirmation component 130 can declare the detection of the trailing edge when the interval count is greater than or equal to 34 * 128 (4352) and the execution count is greater than zero. If the confirmation component fails to detect any of the three conditions above, then you can simply continue to receive correlation values and update the counters. If one of the conditions is detected, the processor can provide one or more additional checks on the counters to increase the confidence with which one of the conditions has actually occurred. In particular, the processor 310 can insist on a minimum number of hits in the p-wool area as what was expected to be observed after the detection of the leading edge. For example, the processor can test whether the hit count is greater than a "fixed" value such as 2000. According to a frame structure mode described here, the expected number of hits in the flat area should be 34 * 128, which is greater than 4000. However, the noise will adjust the current results so that the value obtained can be somewhat less than 4000. If the additional conditions are satisfied, the confirmation component 130 can provide a signal to the edge component. Alternatively, the confirmation component can point to the front edge component locating a new leading edge.It should also be appreciated that the confirmation component 130 can also provide additional functionality such as saving time in cases and updating frequencies. frame detection 100 of Figure 1 is to provide the ongoing detection of the frame and symbol boundaries. However, it will be necessary to perform some fine tuning some time later to obtain a more precise synchronization. Therefore, at least one time reference must be stored for later use by a system and / or fine timing method. According to one modality, each time the execution count is equal to zero, a time case can be saved as an estimate of the last time for the flat area of the correlation curve or the time just before the detection of the correlation. back edge. In addition, proper synchronization requires synchronization at the appropriate frequency. Accordingly, the processor 310 can update a cycle synchronized by frequency using the frequency accumulator 360 at particular times as when the input is periodic. According to one modality, the frequency-synchronized circuit can be updated every 128 input samples. according to what is followed by the interval counter. Returning to Figure 1, the rear edge component 140 can be used to detect the trailing edge if it is not detected by the confirmation component 130. In short, the trailing edge component 130 is operated to detect the trailing edge or simply the trailing edge. delay, so that another leading edge can be detected by the leading edge component 120. Turning to Figure 4 a modality of a rear edge component 140 is illustrated. The trailing edge component 140 may include or be associated with the processor 410, a threshold 420, an interval count 430 and an execution count 440. Similar to the other detection components, the rear edge component 140 may receive a plurality of correlation values of the delayed correlator component. 110 and increase the appropriate counts to facilitate detection of a trailing edge of the correlation curve associated with a first pilot symbol (e.g. ie, a TDM pilot symbol). In particular, the processor 410 can compare the value of the correlation with the threshold 420 and populate either or both of the interval count 430 and the execution count 440. It should be noted that although the threshold 420 was illustrated as part of the edge component Rear can also be received or retrieved from outside the component as from the central problematic location. It should also be appreciated of course that the processor 410 can, before its first comparison, initialize the interval count "430 and the execution count 440 to zero.The interval count 430 stores the number of correlation outputs received. this mode, with each value of the correlation received or retrieved, the processor 410 can increment the interval count 430. The run count stores the consecutive number of times the value or output of the correlation is less than the threshold 420. If the value of the correlation is less than a threshold then the processor 410 can increase the execution count 440, otherwise the execution count 440 can be set to zero. The trailing edge component 140 by means of the processor 410, for example, can test whether a value of the interval count or a value of the execution count has been satisfied using the interval count 430 or the execution count 440. For example, if a run count 440 reaches a certain value the rear edge component can declare the detection of a trailing edge. Otherwise, the trailing edge component 140 can continue to receive values from the correlation and update the counts. If, however, the interval count 430 becomes sufficiently large this may indicate that the trailing edge will not be detected and a new leading edge needs to be located. In a modality, this value can be 8 * 128 (1024). On the other hand, if the execution count 440 hits or exceeds a value this may indicate that the trailing edge has been detected. According to one embodiment, this value can be 32. Additionally, it should be appreciated that the rear edge component 140 can also save time cases for use in acquiring a fine timing. According to one embodiment, the rear edge component 140 can save the case of time when the execution count is equal to zero, thus providing a case of time just before the detection of the trailing edge. According to a modality in the frame structure described infra, the saved time case may correspond to the 256th sample in the following OFDM symbol (pilot 2 TDM) •. A fine screen detection system can subsequently improve the value as discussed in later sections. Figure 5 illustrates a component of the delayed correlator 110 in greater detail according to one embodiment. The component of the delayed correlator 110 exploits the periodic nature of the OFDM symbol of the pilot 1 for the detection of the frame. In one embodiment, the correlator 110 uses the following detection metric to facilitate the detection of the frame: where Sn is the detection metric for the sample period n; "*" denotes a complex conjugate; and | x | 2 denotes the magnitude squared of x. Equation (1) calculates a delayed correlation between two input samples r ± and r ^. L in two consecutive pilot 1 sequences, or c¡ = r¡_L -r¡. This delayed correlation removes the effect of the communication channel without it being necessary to estimate the channel gain and also coherently combines the energy received through the communication channel. Equation (1) then accumulates the results of the correlation 'of all samples Li of a sequence of pilot 1 to obtain a result of cumulative correlation Cn, which is a complex value. Equation (1) then derives the decision or exit metric of the correlation Sn for the sampling period n as the squared magnitude of Cn. The decision metric Sn is indicative of the energy of a sequence of the pilot 1 received from length Li, if there is similarity between the two sequences used for the delayed correlation. Within the component of the delayed correlator 110, a deviation register 512 (of length Li) receives, stores and diverts or changes the input samples. { rp} and provide the input samples. { rn_L} that have been delayed in Li sampling periods. A buffer, of samples may also be used in place of the deviation register 512 '.' A unit 516 also receives the input samples and provides the complex conjugate input samples. { r *} . For each sample period n, the multiplier 514 multiplies the delayed entry sample rn_b - of the deviation register 512 with the complex conjugate entry sample rn of the unit 516 and provides a result of the correlation cn to a deviation record 522 ( of length Lj.) and an adder 524. The lowercase cn denotes the result of the correlation for a sample of. entry, the capital Cn denotes the result of the. Cumulative correlation for Li input samples. The deviation register 522 receives, stores and delays the results of the correlation. { cn} of multiplier 514, and provides the results of the correlation. { cn_L} that have been delayed in Li sampling periods. For each sampling period n, the adder 524 receives and adds the output Cn- ± of the register 526 with the result of cn '. Of the multiplier 514, also subtracts the delayed result, of cn_L of the deviation register 522, and provides its output Cn to register 526. Adder 524 and register 526 form an accumulator that performs the addition operation in Equation (1). The deviation register 522 and the adder 524 are also configured to perform a sum of execution or slip of the x results of the most recent correlation cn to cn_L +]. This is achieved by adding the result of the most recent correlation cn of the multiplier 514 and subtracting the result of the correlation cn_L of i initial sampling periods, lo. which is provided by the deviation register 522. A unit 532 calculates the squared magnitude of the accumulated output Cn of the adder 524 and provides the detection metric Sn. Figure 6 describes the fine screen detection system 600. The system 600 includes a fine timing component 610 and a data decoding component 620. The fine timing component 610 can receive the case of time saved by the time detection system. plot 100 (Figure 1). As mentioned above, this time case may correspond to the 256th sample of the next OFDM symbol, which may be the TDM pilot 2. It is somewhat arbitrary to optimize even channels subject to multipath effects. The fine timing component 610 can then use the symbol of the TDM pilot 2 to improve after this estimate of approximate timing (Tc). There are many mechanisms to facilitate fine timing, including those known in the art. According to one embodiment here, a frequency-synchronized circuit or automatic frequency control circuit can be connected from acquisition mode to tracking, which uses a different algorithm to calculate errors and a different tracking circuit bandwidth. The data decoding component 620 may attempt to decode one or more data OFDM symbols. This is an extra step 'that provides additional confidence that synchronization has been done. If the data is not decoded, a new leading edge will have to be detected again by the leading edge component 120 (Figure 1). Additional details related to fine timing are provided inf xa. In view of the exemplary systems described above, the methodologies that can be implemented will be better appreciated with reference to the following flow diagrams of Figures 7-12. Although for simplicity and explanation purposes, the methodologies are shown and described as a series of blocks, the objective methodologies must not be limited by the order of the blocks, since some blocks may occur in different order and / or concurrently. with other 'blocks a l'o described and exemplified here. In addition, not all illustrated blocks may be required to implement the methodologies provided. Additionally, it should be further appreciated that the methodologies described hereinafter and through this specification can be stored in the article of manufacture to facilitate transportation and "transfer of those methodologies to computing devices." The term article of manufacture, as used herein, It is intended to encompass a computer program accessible from any device, support or computer-readable medium, and a robust initial frame detection method is illustrated in Figure 7. The method essentially contains three stages: in 710, the first stage, an attempt is made to observe a leading edge of the pilot symbol.The leading edge can be detected by analyzing a plurality of detection metrics or correlation output values produced by a delayed correlator.In particular, the detection or detection metrics (Sn) or some function of them (for example, Sn2 ...) can be compared with A threshold value The potential detection of the leading edge can then be predicted on the number of times the metric is greater than or equal to the threshold. At 720, the detected leading edge is confirmed by observing additional correlation values and comparing them with the threshold. Here, the output of the correlator is compared again with the threshold and observations are made with respect to the number of times that the output of the correlator exceeds the threshold.

The process may remain at this stage and for more than or equal to a predetermined time period (corresponding to the flat area) or upon detection of a consistent trailing edge. It should also be noted that the frequency deviation can be obtained here by updating a frequency accumulator periodically. If the confirmation conditions are not satisfied, then there will be a false detection of the leading edge 'and the procedure can be initialized and start again at 710. At 730, an attempt is made -or- to observe the trailing edge if not previously observed. If the output of the correlator remains below the threshold for a number of consecutive samples, for example 32, the detection of the TDM pilot can be declared and it is assumed that the acquisition of the initial frequency was completed. If this condition is not satisfied then the process can be initialized and start again at 710. The time estimate of the initial OFDM symbol is based on the trailing edge. The time case when the correlator output is below the threshold for the first time during observation of the trailing edge can be seen as an index (for example, the 256th sample) in the following symbol OFDM, and, for example, the pilot 2 of TDM. Figure 8 is a flow chart describing a leading edge detection methodology 800. At 810, the transmitted input samples are received. A delayed correlation is made. in 820, on the received entry, and a delayed version of it. A correlation output is then provided to the decision block 830. At 830, the correlation output is compared to a fixed or programmable threshold value. If the value of the correlation is greater than or equal to the threshold, a count or execution counter is increased by 840. If the value of the correlation is less than the threshold then the execution count is set to zero, at 850. The The execution count is then compared, at 860, with a predetermined value that is optimized for the detection of a leading edge in a multipath environment. In one mode, the value can be 64 input samples. If the execution count is equal to the default value it ends. the process. If the execution count is not equal to the value then additional input values are received in 810 and the process is repeated. Figure 9 is a flow diagram of the front edge confirmation methodology 900. Method 900 represents the second stage in an approximate or initial frame detection methodology, in which detection is confirmed (or rejected) of a leading edge by means of detecting additional expected results, namely a flat area and / or a trailing edge. In 910, a thousand input samples are received. A delayed correlation is made on the input sample and a version of it, at 920, to produce a correlation output. A plurality of outputs of the correlator is then analyzed with respect to a programmable threshold to make further determinations. At 930, a determination is made to see if a false front edge was detected, which may result from channel noise, amother things. This determination can be made if sufficient correlation output values are not above the threshold. At 940, a determination is made to see if a leading edge was detected too late. In other words, the leading edge was not detected until it was in the region of the pilot's flat area. At 950, a determination is made to see if the trailing edge was observed. If none of these conditions are true, based on the correlation outputs received since then, the process continues at 910 where more input samples are received. If none of the conditions is true, the process may continue at '960, where an additional determination is made as to whether a flat area lenough to provide confidence that it was detected has been observed. Yes Yes, ": you can finish the process, otherwise the process can proceed with another method, such as method 800 (Figure 8), to detect a new leading edge, in a mode, a new pilot symbol will be transmitted a second after the previous pilot symbol Figure 10 describes a more detailed method 1000 for detecting the flat area and confirming the detection of the leading edge according to a particular mode In this particular process, three counts or counters are used: an interval count, a count of hits and a count of execution In 1010, the counters are initialized to zero In 1012, the input samples are received The interval count is increased, in 1014, to indicate the reception of the input sample. It should be appreciated that although it is not specifically denoted in the block diagram, a frequency cycle can be updated every 128 samples as followed by the interval count. e performs the delayed correlation using the input sample and a delayed version of the same to produce a correlation output (Sn). Then a determination is made, at 1018, to see if Sn is greater than or equal to a threshold (T). 'Yes Sn >; = T, then the count of hits is increased by 1020 and the method can proceed by 1028. If not, then a determination is made at 1022 to see if Sn < T. S. if yes, then the execution count is increased by 1024. If not, then the execution count is initialized to zero and the time is saved. The saved time therefore provides the case of time before the observation of a trailing edge. It should be appreciated that decision block 1022 is not strictly necessary here but is provided for clarity as well as to further emphasize that the order of the processes of that method need not be fixed as shown. The method continues at 1028 where the count of hits and the count of execution are scrutinized to determine if a false front edge was detected. In one modality, this may correspond to the execution count being greater than or equal to 128 and the hit count is less than 400. If it is decided that a false positive was detected the process proceeds to 1036 where a new edge is located Forward. If a false -positive could not be determined then the process continues in decision block 1030. At 1030, the count of execution and the count of hits are analyzed to determine if the leading edge was detected later. According to a specific modality, this may correspond to when the execution count is greater than or equal to 768 and the hit count is greater than or equal to 400. If this is the case, the process may continue at 1034. If the leading edge was not detected late, then the process proceeds to 1032 where the interval count and the execution cbriteum are analyzed to determine if. 'is, being observed the back edge. In a modality of this it can be where the interval count is greater than or equal to 4352 (34 * 128) and the execution count is greater than zero. In other words, the full length of the planar zone has been detected and a fall below the threshold has been observed. But, then all three conditions have failed and the process proceeds to 1012 where more input samples are received. Yes, a determination is made at 1034 that enough values above the threshold have been obscured to allow the methodology to confidently determine that the flat zone has been detected. More specifically, the hit count is greater than some programmable value. In one mode, the value can be 2000. However, this is somewhat arbitrary. Ideally, the process should observe 34 * 128 (4352) samples over the threshold, but the noise may shorten the count. In this way, a programmable value can be set at an optimum level that provides a particular level of confidence that the flat area has been detected. If the hit count is greater than the value provided, then the process ends. If not, the process proceeds to 1036, where a new border needs to be detected. Figure 11 illustrates one modality of the trailing edge detection methodology 1100. The trailing edge methodology can be employed to detect the trailing edge of the correlation curve associated with a pilot symbol, if not previously detected. At 1110, counters that include an interval counter and one counter are initialized to zero. In 1112, the input samples are received. The interval count is increased correspondingly to a received sample, at 1114. Each input sample is used by a delayed correlator to produce a correlation output Sn, 1116. A decision is made at 1118 with respect to the correlation output Sn if it is less than a programmable threshold (T). Yes Sj < T, then the count. Execution is increased and the process proceeds to 1126. If the correlator output is not less than the threshold, then the execution counter is set to zero in 1122 and the time case can be saved in 1124. In 1126, it is done a determination to see if enough correlation outputs have been observed consecutively to declare with confidence the successful identification of the. same. In one modality, this corresponds to an execution time greater than or equal to 32. If the execution time is large enough, the process can be successfully completed.If the execution time is not large enough, the process proceeds to decision block 1128. At 1128, the interval counter can be used to determine whether detection method 1100 should be delayed, in one mode if the interval count equals 8 * 128 (1024) the detection method 1100 back edge is delayed, if the method is not delayed by 1128, then additional samples can be received and analyzed starting again at 1112. If the method is not delayed 1128, then the new leading edge of the pilot will need to be detected since the method 1100 could not see a trailing edge • Figure 12 illustrates a 1200 frame synchronization methodology. In 1210, the process first waits for the auto gain control to settle. Automatic Gain Control (AGC) The automatic gain control adjusts the input signal to provide a consistent signal strength or level, so that the signal can be processed-appropriately. At 1220, a cycle accumulator or frequency synchronized circuit (FLL) is initialized. In 1214, a potential leading edge is detected. At 1216, the leading edge can be formed by the detection of a flat area and / or a trailing edge. If it is determined that a valid leading edge 1218 was not detected, then the. method returns to 1212. It should also be appreciated that this is a point where the circuit or cycle synchronized by frequency can be periodically updated using the frequency accumulator, for example to acquire the initial frequency deviation. At 1220, the trailing edge can be detected if it was not previously observed. If there is only one initial fall of the trailing edge so that it can be saved in time to be used later for fine timing. If the trailing edge is not detected 1222 and was not previously detected, then the method returns to 1212. If the trailing edge was detected then the initial approximate detection has been completed. The procedure continues at 1224 where the cycle or circuit synchronized by frequency is switched to a tracking mode. Fine timing is acquired using a second TDM pilot symbol and information provided by the previous rough estimate. In particular, the case of time saved or saved (Jc) may correspond to a particular sample deviation, within the second pilot symbol. According to one embodiment, the stored time sample may correspond to the 256th sample in the second pilot symbol. Then specific algorithms can be used to improve the estimation of the timing as described in later sections. After the completion of the fine timing acquisition, one or more data symbols can be recovered and an attempt is made to decide which symbols can be attempted in 1228. If, in 1230, the decoding was successful, then the process ends . However, if the process was not successful then the methodology returns to 1212. The following is a discussion of a plurality of suitable operating environments to provide the context for the particular inventive aspects described above. In addition, with the interest of being clear and understandable, a detailed description of a pilot mode multiplexed by time division - pilot 1 TDM and pilot 2 TDM is provided. The synchronization techniques described below and through the specification can be used by several multi-carrier systems and by the downlink as well as the uplink. The downlink (or outbound link) refers to the communication link of the base stations to the wireless devices, and the uplink (or back link) refers to the communication link of the wireless device to the base stations. For clarity, those techniques are described later by the downlink in an OFDM system. Figure 13 shows a block diagram of a base station 1310 and a wireless device 1350 in an OFDM system 1300. The base station 1310 is generally a fixed station and can also be referred to as a base transceiver system (BTS), a point of access or some other terminology. The wireless device 1350 may be fixed or mobile and may also be referred to as a user terminal, a mobile station, or some other terminology. The wireless device 1350 can also be a portable unit, cell phone, a handheld device, a wireless module, a personal digital assistant (PDA) and the like. In the base station 1310, a data processor and. TX pilot 1320 receives different types of data (for example, traffic / packet data and complementary / control data) and processes (for example, encodes, tags and maps symbols) received data to generate data symbols. As used herein, a "data symbol" is a modulation symbol for data, a "pilot symbol" is a modulation symbol for the pilot, and a modulation symbol is a complex value for a point in a signal constellation. for a modulation scheme (for example, M-PSK, M-QAM, and so on). The processor 1320 also processes pilot data to generate pilot symbols and provides the pilot data and symbols of an OFDM modulator 1330. The OFDM modulator 1330 multiplexes the data and pilot symbols onto the appropriate subbands and periods of symbols. and further performs OFDM modulation on the multiplexed symbols to generate OFDM symbols, as described below. A transmitter unit (TMTR) 1332 converts the OFDM symbols into one or more analog signals and also conditions (for example, it amplifies, filters and converts upwards by frequency) the analog signals to generate a modulated signal. The base station 1310 then transmits the modulated signal from an antenna 1334 to the wireless device in the system. In the wireless device 1350, the transmitted signal from the base station 1310 is received by an antenna 1352 and provided to a receiving unit (RCVR) 1354. The receiving unit 1354 conditions (eg, filters, amplifies and downconverts by frequency) the received signal and digitizes the conditioned signal to obtain a flow of input samples. An OFDM demodulator 1360 performs' the demodulation OFDM on the input samples to obtain received data and pilot symbols. The OFDM demodulator 1360 also performs detection (eg, matched filtering) on the received data symbols with a channel estimate (eg, an estimate of the frequency response) to obtain the detected data symbols, which are estimates of the data symbols sent by .the base station 1310. The OFDM demodulator 1.360 provides the data symbols detected - 'to a received data processor (RX) 1370. A synchronization / channel estimation unit 1380 receives the input samples from the receiving unit 1354 and synchronizes to determine the timing of frames and symbols, as described above and below. The unit 1380 also derives the channel estimate using the pilot symbols received from the OFDM demodulator 1360. The unit 1380 provides the symbol timing and channel estimation to the OFDM demodulator 1360 and can provide frame timing to the RX data processor 1370 and / or a 1390 controller. The scrambler OFDM 1360 uses the symbol timing to perform the OFDM demodulation and uses the channel estimation to effect the detection of the received data symbols. The RX 1370 data processor processes'; (eg, undo symbols maps, deinterleaves' and decodes) the detected data symbols of the OFDM demodulator 1360 and provides decoded data. The RX data processor 1370 and / or the controller 1390 may use frame timing to retrieve different types of data sent by the base station 1310. In general, processing by the OFDM demodulator 1360 and the RX 1370 data processor is complementary to processing by the OFDM modulator 1330 and the TX data processor and pilot 1320, respectively, in the base station 1310. The controllers 1340 and 1390 direct the operation to the base station 110 and the wireless device 1350, respectively. The memory units 1342 and 1392 provide storage for the program codes and data used by the controllers 1340 and 1390, respectively. The base station 1310 may send a point-to-point transmission to a single wireless device, a multi-transmit transmission to a group of wireless devices, a broadcast transmission to all wireless devices under its coverage area, or any combination thereof. For example, base station 1310 can issue pilot and complementary / control data to all. Wireless devices under your coverage area. The base station 1310 may further transmit user-specific data to specific wireless devices, multiemmission data to a group of wireless devices, and / or broadcast data to "all wireless devices." Figure 14 shows a structure of super-frame 1400 which it can be used by the O'FDM 1300 system. The data and pilot can be transmitted in superframes, with each superframe having a predetermined duration of time (for example, a second) A superframe can also be referred to as a frame, an interval of time, or some other terminology, for the modality shown in FIGURE 14, each superframe includes a field 1412 for a first TDM pilot (or "TDM pilot 1"), a field 1414 for a second TDM pilot (or "TDM pilot 2"), a field 1416 for complementary data / control, and a field 1418 for traffic / packet data. The four fields 1412 through 1418 are multiplexed by time division in each superframe so that only one field is transmitted at any given time. The four fields are also arranged in the order shown in Figure 14 to facilitate data synchronization and retrieval. The OFDM symbols of the pilot in fields 1412 and 1414, which are transmitted first in each superframe, can be used for the detection of the complementary OFDM symbols in field 1416, which is then transmitted in the superframe. The complementary information obtained from field 1416 can then be used to retrieve the traffic / packet data sent in field 1418, which is transmitted, finally in the superframe. In an exemplary embodiment, field 1412 contains an OFDM symbol for TDM pilot 1, and field 1414 also contains an OFDM symbol for TDM pilot 2. In general, each field can be of any duration, and the fields can be arranged in any order. The TDM pilot 1 and the TDM pilot 2 are broadcast periodically in each frame to facilitate synchronization by the wireless devices. The complementary field 1416 and / or the data field 1418 may also contain pilot symbols that are multiplexed by frequency division with data symbols as described below. The OFDM system has a total system bandwidth of BW MHz, which is distributed in N orthogonal subbands using OFDM. The separation between adjacent subbands is BW / N MHz. Of the N total subbands, M subbands can be used for pilot transmission and data, where M <; N, and the remaining N-M sub-bands may not be used and serve as protection sub-bands. In one embodiment, the OFDM system uses an OFDM structure with N = 4096 subbands in total, = 4000 useful subbands, and N-M = 9β protection subbands. In general, any OFDM structure with any number of total, useful, and protection sub-bands can be used by the OFDM system. As described above, TDM pilots 1 and 2 can be designed to facilitate synchronization by the wireless devices in the system. A wireless device can use the TDM pilot 1 to detect the start of each frame, obtaining an approximate estimate of the timing of the symbol, and estimate frequency errors. The wireless device can then use the TDM pilot 2 to obtain a more accurate symbol timing. Figure 15a shows a mode of the TDM pilot 1 in the frequency domain. For this mode, the TDM pilot 1 comprises Li pilot symbols which are transmitted on Li subbands, one pilot symbol per subband used by the TDM pilot 1. The Lx subbands are uniformly distributed across the N total subbands and are equally separated by subbands, where. For example, N = 4096, I = 128, and S2 = 32. However, other values can also be used for N, Li and 3? . This structure for TDM Pilot 1 can (1) provide good performance for frame detection on various types of 'channels including the severe multipath channel', (2) provide a sufficiently accurate frequency error estimate and the approximate symbol timing in a severe multipath channel, and (3) simplify processing on wireless devices, as described below. . • Figure 15b shows a modality of TDM pilot 2 in the frequency domain. For this mode, the TDM pilot 2 comprises L2 pilot symbols that are transmitted on L subbands, where L2 > . The L2 subbands are evenly distributed across the N total subbands and are equally separated because S2 subbands, where S2 = N / L2. For example, N = 4096, L2 = 2048, and S2 = 2. Again, other values for N, L2 and S can also be used. This structure for the TDM pilot 2 can provide accurate symbol timing in various types of channels including the severe multipath channel. The wireless devices may also (1) process the TDM pilot 2 in an effective manner to obtain symbol timing before the arrival of the next OFDM symbol, which may occur immediately after the TDM 2 pilot, and (2) apply the symbol timing to this next symbol, OFDM, as described below. A smaller value is used for Ll r so that a larger frequency error can be corrected with the TDM pilot 1. A larger value is used for L2r so that the sequence of pilot 2 is larger, which allows a wireless device to obtain an estimate of the impulse response of the largest channel of the pilot sequence 2. The Lx subbands for the TDM pilot 1 are selected so that pilot 1 sequences identical to 5 are generated for the TDM pilot 1. Similarly, the L2 subbands for the TDM pilot 2 are selected so that the sequences of the pilot 2 identical to S2 are generated. for the pilot 2 of TDM. Figure 16 shows a block diagram of a mode of the TX data processor and pilot 1320 in the base station 1310. Within the processor 1320, a data processor TX 1610 receives, encodes, interleaves and maps data symbols of traffic / package to generate data symbols. . '• "In one embodiment, a pseudorandom number generator (PN) 1620 is used to generate data for both TDM pilots 1 and 2. The generator PN PN 1620 can be implemented, for example, with a deviation register. 15-lead linear feedback system (LFSR) that implements a generator polynomial g (x) = x15 + x14 + 1. In this case, the PN 1620 generator includes (1) 15 delay elements 1622a to 16.22o coupled in series and (2) an adder 1624 coupled between the delay elements 1622n and 1622. The delay element 1622o provides pilot data, which are also fed back to the input of the delay element 1622a and the input of the adder 1624. The PN generator 1620 can be initialized with different initial states by the TDM pilots 1 and 2, for example, to 011010101001110 'for the TDM pilot 1 and to 010110100011100' for the TDM pilot 2. In general, any one can be used. data by pilots 1 and 2 of TDM. Pilot data can be selected to reduce the difference between the-, peak amplitude and the average amplitude of a pilot OFDM symbol (ie, to minimize the variation of the peak to the average in the waveform in the time domain for the TDM pilot). The pilot data for the TDM pilot 2 can also be generated with the same PN generator used to mix data. The wireless devices are aware of the data used by the TDM pilot 2 but do not need to know the data used by the TDM pilot 1. A tracer unit of bitmaps to symbols 1630 receives the pilot data from the generator of "PÑ 1620 and maps the bits of the pilot data to pilot symbols based on a modulation scheme. the same or different modulation schemes with the pilots 1 and 2 of TDM., QPSK is used by both pilots 1 and 2 of TDM. In this case, the mapper unit 1630 groups the pilot data into binary values of .2 bits and also maps to each 2-bit value to a specific pilot modulation symbol. Each pilot symbol is a complex value in a signal constellation for QPSK. If QPSK is used by the TDM pilots, then the 1630 map plotter maps the 2L maps? Pilot data bits per pilot 1 from TDM to Lx pilot symbols and also trace the maps of 2L2 pilot data bits for pilot 2 from TDM to L2 pilot-symbols, a multiplexer (Mux) 440 receives the symbols data, "of the data processor TX 1610, the symbols of the pilot of the map trace unit 1630, and the signal TDM_Ctr-l of the controller 1340. The multiplexer 1640 provides the OFDM modulator 1330 with the symbols of the pilot by the TDM pilot 1 and 2 fields and the data symbols-for the complementary and data fields of each frame, "as shown in Figure 14. Figure 17 shows a block diagram of a mode of the OFDM modulator 1330 at the base station 1310. A symbol mapping unit to sub-bands 1710 receives the data and pilot symbols -from the data processor TX and the pilot 1320 and traces, those symbols over the appropriate subbands on the basis of a signal Subband_Mux_Ctrl of the 1340 controller. In each OFDM symbol period, the map trace unit 1710 provides a data symbol or pilot on each subband used for the data transmission or pilot and a "zero symbol" (which is a signal with a value of. zero) for each subband not used. The pilot symbols designated for the sub-bands that are not used are replaced with zero symbols. For each OFDM symbol period, the map trace unit 1710 provides N "transmission symbols" for the N total subbands, where each transmission symbol may be a data symbol, a pilot symbol or a zero symbol. An Inverse Discrete Fourier Transform Unit (IDFT) 1720 receives the N transmission symbols for each OFDM symbol period, transforms the N transmission symbols into the time domain with an 'IDFT d'e' N points, and provides a "transformed" symbol containing N samples in a time domain. Each sample is a complex value to be sent in a sampling period. Also, a fast inverse Fourier transformation of N points (IFFT) can be effected instead of an IDFT of N points if? is a power of two, which is typically the case, a converter in parallel to serial (P / S) 1730 puts in series the N samples of each transformed symbol. A cyclic prefix generator 1740 repeats a portion (or C samples) of each transformed symbol to form an OFDM symbol containing N + C samples. The cyclic prefix is used to combat intersymbol interference (ISI) and intercarrier interference (ICI) caused by a prolonged propagation of delay in the communication channel. The delay propagation is the time difference between the case of the signal that arrives first and the case of the signal that arrives later in the receiver. An 'OFDM symbol' period (or simply, a "symbol period") is the duration of an OFDM symbol and is equal to N + C sampling periods. Figure 18a shows a time domain representation of the TDM pilot 1. An OFDM symbol for the TDM pilot 1 (or "OFDM symbol of.-Pilot 1") is composed of a transformed symbol of length N and a cyclic prefix of length C. Because the Lx pilot symbols for the TDM pilot 1 are sent on Lx subbands that are uniformly separated by S subbands, and because the zero symbols are sent on the remaining subbands, the transformed symbol for the TDM pilot 1 contains S identical pilot sequences 1, with each sequence-of pilot 1 containing x samples in the time domain. Each sequence of pilot 1 can also be generated by performing an IDFT of Lx points, on the Lx pilot symbols for pilot 1 of TDM. The cyclic prefix for the TDM pilot 1 is composed of the C samples farther to the right of the transformed symbol and is inserted in the front part of the transformed symbol. The OFDM symbol of pilot 1 thus contains a total of Sx + C / L? pilot sequences 1. For example, if N = 4096, 2 = 128, Si = 32, and C = 512, then the OFDM symbol of pilot 1 could contain 36 sequences of pilot 1, with each sequence of pilot 1 containing 128 samples in the time domain. Figure 18b shows a time domain representation of the TDM pilot 2. An OFDM symbol for the TDM pilot 2 (or "pilot OFDM symbol 2") is also composed of a transformed symbol of length N and a cyclic prefix • of length C. The transformed symbol for the pilot 2 of TDM contains S2 identical pilot sequences 2, with each; sequence of pilot 2 containing L2 samples in the time domain. The cyclic prefix for the TDM pilot 2 is composed of the C samples furthest to the right of the transformed symbol and is inserted into the front part of the transformed symbol. For example, if N = 40'96, L2 = 2048, S2 = 2, and C = 512, then the OFDM symbol of pilot 2 could contain two complete pilot 2 sequences, with each pilot 2 sequence containing 2048 samples in the domain of time. The cyclic prefix for the TDM pilot 2 could contain only a portion of the pilot sequence 2. Figure 19 shows a block diagram for a channel synchronization and channel estimation mode 1380 in a wireless 1350 device (Figure 1380). 13). Inside the unit 1380, a detector of 100 frames (as described in detail above) receives the input samples from the receiving unit 1354, processes the input samples to detect the start of each frame, and provides the frame timing. A 1920 symbol timing detector receives input samples and frame timing; - processes the input samples to detect the start of the received OFDM symbols and provides the timing of the symbols; a frequency error estimator 1912 estimates the frequency error in the received OFDM symbols. A channel estimator 1930 receives an output from the symbol timing detector 1920 and derives the channel estimate. As described in more detail in the Figure 1, the frame detector 100 performs the frame-synchronization by detecting, for example, by the pilot 1 of TDM, the input samples of the receiver unit 1354. For simplicity, the detailed description of this assumes that the channel of communication is an additive white Gaussian noise channel (A GN). The input sample for each periodic sample can be expressed as: rn = xn + w ", Ec (2) • where n is an index for the sampling period; xn is a sample in the time domain sent by the base station in the sampling period n; rn is an input sample obtained by the wireless device in sampling period n; and wn is the noise for the sampling period n. The frequency error estimator 1912 estimates the frequency error in the OFDM symbol of the received pilot 1. This frequency error can be due to several sources, for example, a difference in the. frequencies of the oscillators in the base station and the wireless device, Doppler shift and so on. The frequency error estimator 1912 can generate a frequency error estimate for each pilot 1 sequence (except for the last sequence of pilot 1) as follows: ¥? = where r? r i is the ith entry sample for the 1-th sequence of pilot 1; Arg (x) is the tangent arc of the relation 'of the imaginary component of x on the real component of x, or Arg (x) = arctan [Im (x) / Re (x)]; Gr, is the gain of the detector, which is 2p -L, GD = -? - I; and J samp? fj. is the frequency error estimate '- for the 1-th sequence of pilot 1.,. • The range of detectable frequency errors can be given as: ? / / f. n I J samp where fsamp is the input sampling rate. Equation (2) indicates that the range of frequency errors detected depends, and is inversely related to, the length of the pilot sequence 1. The frequency error estimator 1912 can also be implemented within the detector component. of frames 100, and more specifically, by means of the component of the delayed correlator 110 because the cumulative correlation results are also available from adder 524. Frequency error estimates can be used in various ways. For example, the frequency error estimate for each sequence of pilot 1 can be used to update a frequency tracking cycle that attempts to correct any frequency error detected in the wireless device. The frequency tracking cycle may be a cycle or phase-synchronized circuit (PLL) that can adjust the frequency of a carrier signal used for the down-conversion of the frequency in the wireless device. The estimates of the frequency error. they can also be averaged to obtain a single frequency error estimate? f for the pilot OFDM symbol 1. This? f "can be used to correct the frequency error before or after the DFT of N points within the demodulator of OFDM 160. For the correction of the frequency error after the DFT, which can be used to correct a frequency deviation? f that is an integral multiple of the subband separation, the receiving symbols of the. N points can be translated by? F subbands, and can a symbol be corrected by frequency- .. ff? for each applicable subband k as Rk = Rk + & f. For the correction of frequency error before the DFT, 'the input samples can be rotated in phase by the frequency error estimate? F, and the DFT of N points can then be effected on samples rotated in phase. The frame detection and the frequency error estimation can also be performed in other ways based on the OFDM symbol of the pilot 1. For example, frame detection can be achieved by direct correlation between the input samples by the OFDM symbol of pilot 1 with the 1 real pilot sequences generated at the base station.The direct correlation provides a result of high correlation for each case of strong signal. " (or multipath). Since more can be obtained from a multipath or peak by a given base station, a wireless device will perform a subsequent processing on the detected peaks to obtain the timing information. The detection of frames can also be achieved with a combination of a delayed correlation and a direct correlation. Figure 20 shows a block diagram of a modality of the symbol timing detector 1920, which performs timing synchronization based on the OFDM symbol of the pilot 2. Within the symbol timing detector 1920, a buffer memory of 2012 samples receives the input samples from the receiving unit 1354 and stores a "sample" window of L2 input samples for the OFDM symbol of the pilot 2. The start of the sample window is determined by a 2010 unit based on of the frame timing of the frame detector 100. FIG. 21a shows a timing diagram of the processing of the OFDM symbol, of the pilot 2. The frame detector 100 provides the approximate symbol timing (denoted as Tc) on the basis of the OFDM symbol of pilot 1. The OFDM symbol of pilot 2 contains S2 identical pilot sequences of length L (for example, pilot sequences or 2 of length 2048 if f = 4096 and L2 = 2048). A window of L2 input samples is collected by the sample buffer 912 by the OFDM symbol of the pilot 2 starting in the sampling period Tw. The start of the sample window is delayed by an initial deviation 0Sini of the approximate symbol timing, or Tw = Tc + OS? N? . The initial deviation does not need to be exact and is selected to ensure that a complete pilot 2 sequence is collected in the 2012 sample buffer. The initial deviation can also be selected so that processing for the OFDM symbol of the pilot 2 can be completed before the fix of the next OFDM symbol, so that the timing of the symbol obtained from the OFDM symbol of pilot 2 can be applied to this next OFDM symbol. Referring again to Figure 20, a 2014 DFT unit performs a DFT of L2 points on the L2 input samples collected by the 2012 sample buffer and provides L values in the frequency domain for the L2 received pilot symbols. If the start of the sample window is not aligned with the. Starting the OFDM symbol of pilot 2 (ie Tw '? TS), then the impulse response of the channel is deviated circularly, which means that a front portion of the channel impulse response is wound back. A pilot demodulation unit 2016 removes the modulation on the L2 received pilot symbols by multiplying the received pilot symbol Rk for each pilot subband k with the full conjugate of the known pilot symbol Pk for that subband, or Rk -Pk. The 2016 unit also sets the pilot symbols received by the sub-bands not used in symbols with a value-of-zero. If an IDFT unit 2018 then performs an IDFT of L2 points on the L2 demodulated symbols of the pilot - and provides L2 values in the time domain, which are L2 branches of a pulse response of the communication channel between the base station 110 and the wireless device 150. FIG. 21b shows the channel impulse response of L2 leads of the IDFT unit 2018. Each of the L2 leads is associated with a complex channel gain in that bypass delay. The channel impulse response can be cyclically diverted, which means that the back portion of the channel impulse response can be rolled up and appear in the initial portion of the output of the IDFT 2018 unit. Referring again to Figure 2.0, A 2020 symbol timing finder can determine the symbol timing by looking, the sting, on the energy of the channel impulse response. Peak detection can be achieved by sliding a "detection" window through the channel impulse response, as indicated in Figure 21b. The size of the detection window can be determined as described below. In each initial window position, the energy of all the leads that fall within the detection window is calculated. Figure 21c shows a graph of the energy of the channel branches at different initial window positions. The detection window was diverted to the circularity on the right, so that when the right edge of the detection window reaches the last derivation in the index L2, the window wraps around the first derivation in index 1. The energy it is thus collected by the same number of channel derivations ppr each initial window position. The size of the detection window can be selected based on the expected delay propagation of the system. The propagation delay in a wireless device is the time difference between the signal components arriving earlier and later to the wireless device. The propagation of system delay is the largest delay propagation among all wireless devices in the system. If the size of the detection window is equal to or greater than the propagation of system delay, then the detection window, when properly aligned, will capture all the energy of the channel impulse response. The size of the detection window Lw can also be selected so that it is not more than half of L2 (or Lw = L2 / 2) to avoid ambiguity in detecting the start of the channel impulse response. The start of the channel impulse response can be detected (1) by determining the peak energy between all the L initial window positions and (2) identifying the initial window position further to the right with the peak energy, if multiple positions Window initials have the same peak energy. The energies for the different initial window positions can also be averaged or filtered to obtain a more accurate estimate of the start of the channel impulse response in a noisy channel. In any case, the start of the channel impulse response is denoted as -BT, and the deviation between the start of the sampling window and the start of the channel impulse response is T0s = TB-TW.-The Fine symbol timing can be calculated uniquely once the start of the TB channel impulse response has been determined. Referring to Figure 21a, the fine symbol timing is indicative of the start of the received OFDM symbol. The fine symbol timing Ts can be used to accurately and appropriately place a "DFT" window for each OFDM symbol received later. The DFT window indicates the N. specific input samples (from among N + C input samples) to collect each received OFDM symbol. The N input samples within the DFT window are then transformed with a DFT of N points to obtain the N received data / pilot symbols by the received OFDM symbol. The exact placement of the DFT window for each received O-FDM symbol is necessary to avoid (1) intersymbol interference (ISI) of a preceding or following OFDM symbol "(2) degradation in channel estimation (eg, inappropriate placement of the DFT window may result in an erroneous channel estimate), (3) errors in processes that depend on the cyclic prefix (for example, cycle or frequency tracking circuit, automatic gain control (AGC), and so on), and (4) other harmful effects.The OFDM symbol of pilot 2 can also • It can be used to obtain a more accurate frequency error estimate For example, the frequency error can be estimated using the sequences of pilot 2 and based on equation (3), in this case, the sum is made on the L2 samples (instead of the Lx samples) for the pilot sequence 2. The channel impulse response of the IDFT 2018 unit can also be used to derive a frequency response estimate for the communication channel between the station. base ion 1310 and wireless device 1350. A unit 2022 receives a channel impulse response from L leads, the circularity bypasses the channel impulse response so that the start of the channel impulse response is in-. index 1, inserts an appropriate number of zeros after the channel impulse response deviated by circularity, and provides an impulse-channel response of N leads. A DFT unit 2024 then forms a DFT of N points on the N-channel channel impulse response and provides the frequency response estimate, which is composed of N complex channel gains by the 'N total subbands. The OFDM demodulator • 1360 can use the frequency response estimate for the detection of the data symbols received in the subsequent OFDM symbols. The estimation of the channel can also be derived in some other way. Figure 22 shows a pilot transmission scheme with a combination of TDM and FDM pilot. The base station 1310 can transmit the TDM pilots 1 and -2 in each superframe to facilitate initial acquisition by the wireless devices. The load '"for the TDM pilots is two OFDM symbols, which may be small compared to the size of the superframe.The base station 1310 may also transmit one FDM pilot in all, most, or some of the OFDM symbols remaining in each super-frame For the embodiment shown in Figure 22, the FDM pilot is sent on an alternate set of sub-bands so that the pilot symbols are sent in a set of sub-bands in periods of even-numbered symbols and over another set of subbands in periods of numbered and even symbols Each set contains a sufficient number of Lfdm) subbands to support the channel estimate and possibly one- tracking of frequency and time by the wireless devices The subbands in each set can be evenly distributed across the N total subbands and evenly separated by Sfcta = N / Lfdm subbands .. In addition, the subbands in a set can be alternated, or deviated with respect to the sub-bands in the other set. So the subbands in the two sets are interspersed with each other. As an example, N = 4096, Lfdm = 512, -Sfdm = 8, and the subbands in the two sets can be alternated by four subbands. In general, any number of sets of subbands can be used by the FDM pilot and each set can contain any number of subbands and any of the N total subbands. A wireless device can use TDM pilots 1 and 2 for initial synchronization, for example for frame synchronization, frequency deviation estimation, and fine symbol timing acquisition (for proper placement of the DFT window for subsequent OFDM symbols). The wireless device can perform the initial • synchronization, for example, when you have access to a base station for the first time, when you receive it? request data for the first time or after a prolonged period of inactivity, when it is turned on for the first time, and so on. The wireless device can perform the delayed correlation of the pilot 1 sequences to detect the presence of the OFDM symbol of the pilot 1 and thus the start of a superframe, - as described above. Subsequently, the wireless device can use the sequences of the pilot '1 to estimate the frequency error in the OFDM symbol of the pilot 1 and to correct this frequency error before. to receive the OFDM symbol from pilot 2. The OFDM symbol of pilot 1 allows the estimation of a larger error-frequency and a more reliable placement of the DFT window for the next OFDM symbol (pilot 2) that the conventional methods using the cyclic prefix structure of the data -OFDM symbol. The OFDM symbol of the pilot 1 can thus provide better operation for a terrestrial radio channel with a large multipath delay propagation. The wireless device may use the OFDM symbol of the pilot 2 to obtain the fine symbol timing to more accurately place the DFT window for the OFDM symbols received later. The wireless device can also use the OFDM symbol of pilot 2 for can-al estimation and frequency error estimation. The OFDM symbol of Pilot 2 allows fast and accurate determination of fine symbol timing and proper positioning of the DFT window. The wireless device can use the pilot FDM for channel estimation and temporal tracking and possibly for frequency trackingX The wireless device can obtain an initial channel estimate based on the OFDM symbol of pilot 2, as described above. The wireless device 75.,. _ -,.

You can use the OFDM pilot to obtain a more accurate channel estimate, particularly if the 'FDM' pilot. it is transmitted through the superframe, as shown in Figure 11. The wireless device can also use. the FDM pilot to update the cycle or frequency tracking circuit that can correct frequency errors in received OFDM symbols. The wireless device may also use the FDM pilot to update a cycle or time tracking circuit, which may take into account the timing drag on the input samples (e.g., due to changes in the channel impulse response). of the communication channel). The synchronization techniques described herein can be implemented by various means. For example, these techniques can be implemented by physical computing or hardware components, software or programming systems or software, or a combination thereof. For an implementation of physical computing or hardware components, the processing units in a base station used to support synchronization (for example, the TX data processor and pilot 120) can be implemented within one or more application-specific integrated circuits (ASIC), digital signal processors (DSP), devices. digital signal processing (DSPDs), programmable logic devices (PLD), gate arrays, programmable in the field (FPGA), processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform, the functions described here , or a combination of. l -the same. The processing units in a wireless device used to effect synchronization (for example, the channel 180 timing and estimation unit) can also be implemented with one or more ASICs, DSPs, and so on. For the implementation by programs and programming or software systems, synchronization techniques can be implemented in combination with program modules (for example, routines, programs, components, procedures, functions, data structures, schemas ...) that perform the different functions described here. Program codes and programming or software systems can be stored in a memory unit (for example, the memory unit. "Í392 in Figure 13) and executed by a processor (for example, controller 190). of memory may be implemented within the processor or external to the processor.In addition, those skilled in the art will appreciate that the methods object of the invention may be practiced with other configurations of computer systems, including single-processor or microprocessor computer systems. or multiprocessor, mini-computing devices, large computers, as well as personal computers, hand-held computing devices, consumer-based electronic devices, microprocessors, etc. As used herein, OFDM may also include an access architecture. multiple by orthogonal frequency division (OFDMA) where multiple users share OFDM channels. which has been described above includes examples of various aspects and modalities. Of course, it is not possible to describe every conceivable combination of the components or methodologies. Various modifications to these modalities will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other modalities without departing from the spirit or scope of the modalities mentioned above. In this way, the described modalities are not intended to be limited to the aspects and modalities shown and described herein but according to the broadest scope consistent with the principles and characteristics and novel techniques described herein. Further, to the extent that the term "includes" has been used in any detailed description or claims, that term is meant to be inclusive, 'in a manner similar to the term "comprising" as "comprising" is interpreted when It is used as a transition word in a claim.

Claims (78)

1. NOVELTY OF THE INVENTION Having described the invention as above, "the content of the following is claimed as property; CLAIMS 1. An initial frame detection and synchronization method, characterized in that it comprises: receiving a flow of input signals having at least some associated with a pilot-symbol; generate correlation outputs that form a correlation curve from signals and delayed copies thereof; detecting a potential leading edge of the correlation curve from the correlation outputs; confirm detection of the leading edge from the correlation outputs; and detect a trailing edge of the curve of the correlation outputs. The method according to claim 1, characterized in that the detection of the potential leading edge comprises: comparing a correlation output with a threshold; ... increasing a counter if the output is less than or equal to the threshold; Analyze the counter to determine if it is equal to a predefined value. 3. The method of compliance with. Claim 2 characterized in that the. The predefined value is 64. 4. The method according to claim 1, characterized in that the confirmation of the detection of the leading edge includes detecting a flat area and / or a trailing edge. 5. The method according to claim 4, characterized in that the flat zone is detected by counting the number of times the correlator values are greater than or equal to a threshold. "" 6. The compliance method. with ... claim 4 characterized in that the trailing edge is detected by counting the number of times that the output of the correlator is less than a threshold. 7. The method according to claim 1, characterized in that the confirmation of the detection of a leading edge comprises:. - increase a first counter if the "correlation value is greater than or equal to a threshold;" • increase a second counter if the correlation value is less than the threshold by readjusting the second counter to zero otherwise; values of the first and second counters to decipher which one is being received 8. The method according to claim 7, characterized in that a false front edge is detected when the first counter is substantially equal to the second counter: 9. The method according to claim 7 characterized in that it further comprises saving time to be used with a fine timing algorithm when the second counter is equal to zero. 10. The method of compliance with. claim 7, characterized in that it further comprises increasing a third counter for each new sample. received and correlated. 11. The method according to claim 10, characterized in that the beginning of the trailing edge is observed when the third counter indicates that the entire planar zone should have been received and the second counter is greater than zero. The method according to claim 7, characterized in that it further comprises-requiring that the first value of the counter be greater than or equal to half the number of what it would be without the tempering effect of the noise before declaring the detection of a flat area or a trailing edge. _; 13. The method of conformity • with-claim 1, characterized in that it also comprises-updating a cycle or frequency-synchronized circuit periodically before detection of the trailing edge. The method according to claim 1, characterized in that the detection of the trailing edge comprises: increasing a first counter when the value of the correlation is less than a threshold, otherwise. adjust the first counter equal to zero; and determining when the first counter is equal to a predetermined value 15. The method according to claim 14, characterized in that the predetermined value is 32. 16. The method according to claim 14., characterized in that it also comprises saving time when the first counter is equal to zero, to be used by a fine timing algorithm. The method according to claim 14, characterized in that it further comprises increasing a second counter for each received sample to facilitate the timing of a process of detecting the trailing edge after a -nümér-ó. default of samples. 18. The method according to claim 1, characterized in that the pilot symbol is a TDM symbol. ': 19. A method implemented in a computer for the synchronization of frames and the acquisition of the initial symbol timing, characterized in that it comprises: receiving emission signals that transmit at least a plurality of wireless symbols; detecting a potential leading edge of a correlator output associated with a first pilot symbol; confirm the detection of the leading edge by detecting a flat area of the output of the correlator; and detecting a trailing edge of the correlator output. 20. The method according to claim 19, characterized in that the wireless symbols are OFDM symbols. • '. • • '21. The method of compliance with' - claim 19, characterized in that the pilot symbol is a TDM pilot symbol. 22. The method according to claim 19, characterized in that the potential leading edge is detected by analyzing the output of a delayed correlator to determine if the output exceeds a threshold during a predetermined number of consecutive times. 23. The method according to claim 19, characterized in that it further comprises updating a cycle or frequency circuit periodically during the observation of the planar zone. 24. The method according to claim 23, characterized in that it further comprises saving a case of time just before the detection of a trailing edge, where the case of time is related to a specific number of samples in a second pilot symbol. 25. The method according to claim 24, characterized in that the second pilot symbol is a TDM pilot symbol. 26. The method of. according to claim 24, characterized in that it further comprises changing the cycle or frequency circuit to the tracking mode. 27. The method according to claim 26, characterized in that it further comprises acquiring fine timing using the second symbol of the pilot and the case of time saved. 28. The method according to claim 19, characterized in that the detection of the planar zone comprises: generating correlation outputs correlating new signal samples with a delayed version thereof; compare the correlation output with a threshold; and increasing a counter when the correlation output is greater than or equal to the threshold, where the flat zone is detected when the value of the counter is at least half the value that would be detected in an ideal environment. 29. The method according to claim 19, characterized in that the detection of the trailing edge comprises: generating correlation outputs correlating new signal samples with a delayed version thereof; compare each correlation output with a threshold; and increase a counter when the correlation output 'is less than the threshold, otherwise set the execution counter to zero, where the detection "of the flat zone occurs • when the second counter is greater than or equal to a value 30. A computer implemented method for the detection of initial wireless symbol frames and the acquisition of approximate symbol timing, characterized in that it comprises: receiving a flow of emission input signals, at least some is associated with a symbol of pilot, generate correlation outputs that form a correlation curve over time from signals and delayed copies of them, detect a leading edge of the correlation curve, detect a portion of the flat area of the correlation curve and detecting a trailing edge of the curve 31. The method of compliance with claim 30, characterized in that the symbol of the iloto is an OFDM pilot symbol. The method according to claim 30, characterized in that the detection of the leading edge comprises: comparing a correlation output with a threshold; * increasing a counter if the output is less than or equal to the threshold and then adjusting the counter to zero; and evaluate the counter to determine if- is equal to a predefined value. . - '• "., 33. The method according to claim 32, characterized in that the detection of the flat zone comprises: comparing the correlation output with the threshold; increase a second counter when the correlation output is greater than or equal to the threshold; and scrutinizing the counter value to determine if the value is greater than or equal to a predetermined value that is less than an expected value in an ideal environment. 34. The method according to claim 33, characterized in that it further comprises updating a cycle or frequency circuit periodically to count the deviation or frequency change of the signal. 35. The method of compliance with. • 'claim 33, characterized in that the detection of the trailing edge comprises: increasing a third counter when. the correlation value is less than the threshold, in another mode • adjust the counter equal to zero; and determine if and when the counter is equal to a predetermined value. 36. The method according to claim 35, characterized in that it also comprises saving time when the third counter is equal to zero. 37. A frame detection and synchronization system, characterized in that it comprises: a component of the delayed correlator that receives a flow of input samples, correlates the input samples with delayed versions of. them, and generates a plurality of outputs that form a correlation curve; a component of the leading edge that receives outputs, compares the outputs with a threshold, and generates a signal if it detects a potential leading edge of the correlation curve; "; a confirmation component which, after receiving the signal from the leading edge component, compares the additional outputs with the threshold to confirm that the leading edge was detected, and a component of the trailing edge which after a signal from the confirmation component compares the additional outputs with the threshold to locate the trailing edge of the correlation curve • 38. The compliance system "with.- claim 37, characterized in that the component 'of the leading edge is configured to generate the signal when the output remains greater than or equal to the threshold during a predetermined number of consecutive samples 39. The system according to claim 38, characterized in that the consecutive number of samples is 64. J 40. The system of according to claim 37, characterized in that the component- of. confirmation comprises: a hit counter that stores the number of times the output is greater than or equal to the threshold; an execution counter that stores the number of consecutive outputs that are less than the threshold; and - a processing component that -receives outputs, compares the outputs with a threshold and populates the counters. 41. The conformity system ".with claim 40, characterized in that the execution counter and the hit counter provide the indication that a leading edge was not detected.- 42. The system according to claim 41 , characterized in that the execution counter has a value greater than or equal to 128, and the hit counter has a value less than 400. '.' - 43. The system of 'compliance with' 'claim 40, characterized in that the counter-run and the hit counter indicate that the leading edge component was slow in detecting the leading edge. 44. The system according to claim 43, characterized in that the execution counter is greater than or equal to 768 and the hit counter is greater than 400. 45. The compliance system according to claim 40, characterized in that it also comprises an interval counter that stores the number of output values produced and analyzed. 46. The system according to claim 45, characterized in that the interval counter in conjunction with the execution counter indicates the detection of a trailing edge of the correlation curve. 47. The system of conformity .with .. the. Claim 46, characterized in that the counter, of. intervals is greater than or equal to 4352 and the counter of. execution is greater than zero. 48. The compliance system with. J Claim 45, characterized in that it also comprises a component that updates a cycle or circuit synchronized by frequency every 128 outputs according to what is indicated by the interval counter. 49. The system according to claim 45, characterized in that the confirmation component is configured to save time in the case when the execution counter is equal to zero. 50. The system according to claim 37, characterized in that the rear edge component comprises: an execution counter that stores the number of consecutive times that the correlation value is less than the threshold; and a processor that receives correlation values, compares the correlation value with the threshold and increases the execution count to the value which is indicative of the detection of the trailing edge. 51. The system in accordance with the. claim 50, characterized in that the rear edge component detects a trailing edge when the value of the execution counter is 32. 52. The system according to claim 50, characterized in that it also comprises an interval counter that increases every ez a new correlation value is received, where the interval counter is used to delay., the search for the trailing edge. 53. The system according to claim 52, characterized in that it further comprises a component that causes the search for the trailing edge to be delayed when the interval counter is greater than or equal to 8 * '128. 54. The compliance system c) claim 52, characterized in that the rear edge component saves time when the execution counter is equal to zero. 55. A wireless apparatus characterized in that it comprises: a component of the receiving receiver. broadcast transmissions, including a plurality of wireless symbol frames, at least one frame comprising a pilot symbol; and a frame detector component that identifies the beginning of a frame from the detection of the pilot symbol. 56. The apparatus according to claim 55, characterized in that the wireless symbol frames are OFDM frames. 57. The compliance device. with claim 55, characterized in that the pilot symbol is a TDM pilot symbol. '• 58. The apparatus according to claim 55, characterized in that it further comprises a correlator that generates output values of the received signals and delayed versions thereof, the output values producing a de-correlation curve over time. 59. The apparatus according to claim 58, characterized in that the frame detector component comprises: a front edge component that detects a leading edge of a correlation curve on the base of a first programmable value, a threshold, and the output of the correlator; a flat-area component that identifies a flat portion of the correlation curve based on a second programmable value, the threshold and the correlator output; and a component of the trailing edge which detects-a trailing edge in the correlation curve on the basis of a third programmable value, the threshold and the output, of the correlator. 60. The apparatus according to claim 59, characterized in that the front edge component is configured to detect a leading edge when the correlator output is greater than or equal to the threshold for a consecutive number of times equal to or greater than the first programmable value 61. The apparatus according to claim 60, characterized in that the component of the planar zone is configured to detect a flat area when the correlator output is greater than or equal to the threshold for a number of times greater than or equal to the second. programmable value 62. The apparatus according to claim 61, characterized in that the rear edge component is configured to detect the trailing edge when the output of the correlator is less than the threshold during the consecutive number of times equal to or greater than the third programmable value. 63. An initial frame detection system, characterized in that it comprises: means for receiving a signal flow at least a portion of which are associated with a pilot symbol; means for generating correlation outputs of the signals and delayed copies thereof; and means for detecting a leading edge,. a flat area, and a trailing edge of the outputs' correlation. 64. The system according to claim 63, characterized in that the pilot symbol is a TDM pilot symbol 65. The system according to claim 63, characterized in that the means for detecting a leading edge comprise means for comparing the values of output with a threshold being the "leading edge detected when the output - values are greater than the threshold during a first - programmable number of consecutive times. 66. The system according to claim 65, characterized in that the means for detecting a flat area comprise means for comparing output values with the threshold, the flat area being detected when the output values are greater than or equal to the threshold. during a second programmable number of times. 67. The system according to claim 66, characterized in that it also comprises means for detecting a deviation or approximate frequency change. 68. The system of conformity with. claim 67, characterized in that it also comprises means for saving time after detection of the flat area and before the initial detection of the trailing edge. • • '69. The compliance system "with claim 66, characterized in that the means for detecting a trailing edge comprise means for comparing the output values with the threshold, the trailing edge being detected when the threshold is less than the threshold. for a third programmable number of times 70. Microprocessor executing instructions for detecting an initial frame detection and synchronization method, characterized in that it comprises: X '- .. generating correlation metrics from signal samples and delayed copies of the same; and detect a leading edge, a flat area, and a trailing edge by comparing the metrics with the threshold. 71. The method according to claim 70, characterized in that a leading edge is detected when the metric is greater than the -threshold during a first predetermined number of consecutive times. 72. The method according to claim 71, characterized in that a flat area is detected after detection of the leading edge when the metric is greater than the threshold during a second predetermined number of times. -. 73. The method according to claim 70, characterized in that the trailing edge is detected when the metric is greater than the threshold during. a third predetermined number of consecutive times. 74. The conformance method according to claim 70, characterized in that it comprises "in addition to updating the cycle or circuit synchronized by frequency to take into account a deviation or change of frequency of a detection set of the flat area. method according to claim 70, characterized in that it also comprises saving time after detection of at least a portion of the flat area and before detection of the initial trailing edge 76. A frame detection and synchronization system, characterized because it comprises: a first component that receives a plurality of data packets comprising at least one pilot symbol; a second component that generates correlation metrics from the data packets; a third component that analyzes the metrics over time to determine if a pilot symbol has been received, the pilot symbol received after the detection of metric values stent less than the threshold for a first number of times, followed by metric values greater than or equal to the threshold for a second number of times, followed by metric values consistently less than the threshold during the third number of times. 77. The system according to claim 76, characterized in that it also comprises a component that counts the deviation or change of frequency when the values of the metric are greater than or equal to the threshold. 78. The system according to claim 77, characterized in that the third component saves time after the detection of metric values greater than or equal to the threshold and just before the detection of metric values consistently less than the threshold.