Disclosure of Invention
The main technical problem to be solved by the embodiments of the present invention is to provide a method and a device for initiating and detecting reverse access, so that the performance of a wireless terminal moving at a high speed in a reverse access channel is improved.
In order to solve the above technical problem, an embodiment of the present invention provides a method for initiating a reverse access, where at least two speed ranges and signature sequence groups corresponding to the speed ranges are preset;
the wireless terminal determines the speed range according to the self moving speed, selects a signature sequence from the signature sequence group corresponding to the speed range, generates a reverse access prefix according to the signature sequence and sends the reverse access prefix to the network side.
The embodiment of the invention also provides a method for detecting reverse access, which presets at least two speed ranges and signature sequence groups respectively corresponding to the speed ranges;
and the network side detects the reverse access prefixes generated by each signature sequence group corresponding to each speed range by using different block modes, wherein the higher the speed range is, the smaller the block mode is, and the number of blocks is more than or equal to 1.
The embodiment of the invention also provides a method for initiating reverse access, which comprises the following steps:
the wireless terminal repeats the short signature sequence at least once in the time domain to generate a reverse access prefix and send the reverse access prefix to a network side;
the length of the short signature sequence is determined by the maximum moving speed of the wireless terminal supported by the network side, and the length of the short signature sequence is shorter when the maximum moving speed is higher.
The embodiment of the invention also provides a method for initiating reverse access, which comprises the following steps:
presetting at least two distance ranges or speed ranges, wherein each distance range or speed range corresponds to a different reverse access prefix structure;
the wireless terminal determines the distance range according to the distance between the wireless terminal and the base station, or determines the speed range according to the moving speed of the wireless terminal, and generates a reverse access prefix according to the distance range or the structure corresponding to the speed range and sends the reverse access prefix to the network side.
The embodiment of the invention also provides a method for detecting reverse access, which comprises the following steps:
presetting at least two distance ranges or speed ranges, wherein each distance range or speed range corresponds to different resource ranges and different reverse access prefix structures respectively;
the network side determines the distance range or the speed range of the wireless terminal which sends the reverse access prefix according to the resource range of the resource which transmits the reverse access prefix, and detects the reverse access prefix according to the reverse access prefix structure corresponding to the distance range or the speed range.
An embodiment of the present invention further provides a wireless terminal, including:
a unit for storing at least two speed ranges and signature sequence groups respectively corresponding to the speed ranges;
a group selecting unit for determining the speed range according to the moving speed of the wireless terminal and selecting the corresponding signature sequence group according to the speed range;
a code selecting unit that selects one signature sequence from the selected signature sequence group;
and a sending unit for generating a reverse access prefix according to the selected signature sequence and sending the reverse access prefix to a network side.
The embodiment of the present invention further provides a network side device, including:
a storage unit for storing at least two speed ranges and signature sequence groups respectively corresponding to the speed ranges;
a receiving unit for receiving a reverse access prefix signal from a wireless terminal;
a block detection unit for detecting the reverse access prefix signal received by the receiving unit in a block mode;
the reverse access prefixes generated by the signature sequence groups corresponding to the speed ranges are detected by using different block modes, the higher the speed range is, the smaller the block mode is, and the number of the blocks is more than or equal to 1.
The technical scheme of the invention is mainly different from the prior art in that signature sequences are grouped, different signature sequence groups are used in different speed ranges, and a network side receives the high-speed signature sequence groups in a blocking mode, so that the packet loss rate of reverse access of the high-speed wireless terminal is reduced, and the performance of a reverse access channel is improved.
The signature sequence groups in different speed ranges are detected by different block modes, the signature sequence group in the lowest speed is not detected by the block mode, and the signature sequence group in the higher speed is detected by smaller blocks, so that the block size is suitable for the change condition of reverse channels in different speeds, and the best effect is achieved.
The signature sequences in the signature sequence group corresponding to different speed ranges are different in length, the signature sequence corresponding to a higher speed range is shorter, the wireless terminal repeats the selected short signature sequence on a time domain for multiple times to generate a long reverse access prefix, the repetition times are related to the length of the signature sequence, the longer the signature sequence is, the fewer the repetition times are, and the finally generated access prefixes are the same in length; the network side carries out blocking according to the repeated times, so that the size of the blocking corresponds to the length of the signature sequence, and each signature sequence in the prefix is taken as a unit for carrying out correlation detection, so that the best effect is achieved during detection.
Only one signature sequence group is used for carrying out related detection on each block mode, so that the detection efficiency is improved.
The blocks can be overlapped with each other, and the accuracy of block detection is improved.
Shorter signature sequences can be selected for wireless terminals which are closer to the base station, so that the detection performance of the wireless terminal which moves at a high speed in the center of the cell is improved.
Longer signature sequences can be selected for wireless terminals far away from the base station, so that the defect of limited terminal power is overcome, and the coverage range of signals is improved. The longer signature sequences are grouped according to the speed range so as to be received by different block modes at the network side, thereby further improving the success rate of reverse access of the wireless terminal far away from the base station when the wireless terminal moves at high speed.
The selected signature sequence is modulated and transmitted after being interleaved, thereby improving the capability of resisting channel time selectivity attenuation and frequency selectivity attenuation.
The wireless terminal divides the signature sequence into blocks, and interleaves each block independently, and the interleaving modes for each block can be the same or different and respectively represent different signature sequences. The network side tries to perform deinterleaving by using various possible deinterleavers, and knows the interleaving mode used by the wireless terminal, so that different signature sequences are distinguished by different interleaving modes.
The network side allocates different transmission resources, such as frequency resources and/or time slot resources and/or spread spectrum code resources, for different speed ranges or different distances from the base station, and distinguishes wireless terminals in different speed ranges or different distances according to the transmission resources, and directly adopts a corresponding block mode for detection, thereby simplifying the detection operation of the network side.
The network side detects the received reverse access prefix in a blocking mode and a whole block mode respectively, and if any one of detection energy of the blocking detection or the whole block detection exceeds a judgment threshold value, the network side is considered to capture the reverse access prefix. By detecting the two methods, the wireless terminals with different moving speeds can be better met, when the moving speed of the terminal is higher, the detection effect can be improved by overlapping and partitioning detection, when the moving speed of the terminal is lower, a better detection effect can be obtained by integral detection, the packet loss rate of reverse access of the wireless terminal can be reduced by detecting from two aspects, and the performance of a reverse access channel is improved.
The wireless terminals with different distances from the base station or the wireless terminals with different moving speeds adopt reverse access prefixes with different protection time and different cyclic prefix lengths, so that the cyclic prefix sent by the wireless terminal far away from the base station can better keep orthogonality, and the access success rate of the part of terminals is improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
In the invention, signature sequences are grouped in advance, each signature sequence group corresponds to different speed ranges, a wireless terminal initiates reverse access by using the signature sequences in the corresponding signature sequence group according to the moving speed of the wireless terminal, and a network side detects and receives the high-speed signature sequence group in a blocking mode, thereby reducing the packet loss rate of the reverse access of the high-speed wireless terminal and improving the performance of a reverse access channel.
In the present invention, reverse access refers to access initiated from a terminal to a network side, and is also referred to as random access in some wireless communication systems.
A first embodiment of the present invention will be described below, which relates to a method for initiating and detecting reverse Access, and the mobile communication system in this embodiment is an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a reverse Access prefix is transmitted on consecutive subcarriers of one physical frame (8 OFDM symbols).
In this embodiment, two speed ranges, a high speed range and a low speed range, are preset, and a speed threshold may be set, where the moving speed is greater than the threshold and belongs to the high speed range, and the moving speed is less than or equal to the threshold and belongs to the low speed range. Dividing the signature sequence into two groups, wherein the first group corresponds to the wireless terminal with the moving speed belonging to the altitude range; the second group corresponds to wireless terminals whose moving speed belongs to a low speed range. Assuming that the signature sequences are 1024-bit-long Walsh codes and the number of signature sequences is 1024, Walsh codes indexed 0 through 511 can be divided into a first signature sequence group and Walsh codes indexed 512 through 1023 into a second signature sequence group.
As shown in fig. 3, when the wireless terminal needs to transmit a prefix sequence, the method first proceeds to step 301, where a speed range is determined according to the moving speed of the wireless terminal itself, one signature sequence is selected from a signature sequence group corresponding to the speed range, and a reverse access prefix is generated according to the signature sequence and transmitted to the base station.
Specifically, as shown in fig. 4, a Walsh code group selector is used to select a corresponding signature sequence group according to the moving speed of the wireless terminal, and then a Walsh code selector is used to select an appropriate Walsh code from the selected signature sequence group according to the prior art, the selected Walsh code is scrambled by a scrambling code and arranged into a matrix of 128 rows and 8 columns, each column is subjected to 128-point DFT, and then mapped onto 128 subcarriers of OFDM, and then modulated by OFDM, and transmitted through an antenna. One Walsh code is sent over 8 OFDM symbols.
Wherein, the moving speed of the wireless terminal is the moving speed of the wireless terminal at the current moment or the average speed in the latest fixed-length time period. The current moving speed of the wireless terminal can be obtained by detecting the change speed of the downlink pilot frequency quality, or by a network assisted Global Positioning System (GPS), or other speed measurement methods.
Then, step 302 is entered, and at the receiving end, the base station needs to detect the reverse access prefixes generated by the signature sequence sets corresponding to different speed ranges in different manners. And a multi-block detection mode is adopted for a high-speed range, and a whole-block detection mode is adopted for a low-speed range. In this embodiment, both the whole block detection method and the multi-block detection method are referred to as block detection, where the whole block detection method is a specific example of block detection, that is, only one block is detected.
When the block detection method is adopted, as shown in fig. 5, firstly, OFDM demodulation (including cyclic prefix removal and 512-point FFT) and 128-point IDFT conversion are performed on a received signal (i.e., a reverse access prefix) by the prior art, and the demodulated reverse access prefix is continuously blocked according to a carried OFDM symbol, and the blocks can be overlapped with each other to improve the accuracy of block detection. For example, the reverse access prefix is transmitted on 8 consecutive OFDM symbols, and when the reverse access prefix is divided into blocks, the 1 st to 4 th symbols may be divided into a first block, the 3 rd to 6 th symbols may be divided into a second block, and the 5 th to 8 th symbols may be divided into a third block. Alternatively, when the blocks are divided, the blocks may be divided without overlapping. For example, the 1 st to 4 th symbols are directly divided into a first block, and the 5 th to 8 th symbols are divided into a second block. And then, respectively carrying out correlation detection on the prefix loaded on each block, and detecting to obtain the correlation energy of each block. In the correlation detection, only Walsh codes in the signature sequence group corresponding to the speed range are correlated. And then, carrying out joint judgment on the detection result through a judgment device, namely adding or averaging the correlation energy of each block obtained by detection, then comparing the correlation energy with a judgment threshold value, judging that the reverse access prefix is captured if the correlation energy is greater than the judgment threshold value, and otherwise, judging that the reverse access prefix is not captured.
In the detection of the reverse access prefix generated by the signature sequence group corresponding to the low-speed range, the received signal is subjected to OFDM demodulation (including cyclic embellishment and 512-point FFT) by the prior art, prefix data is extracted from eight continuous symbols of 128 subcarriers for transmitting the reverse access prefix, the prefix data is restored into a sequence of 1024 scrambled elements through 128-point IDFT conversion and rearrangement, and the sequence is subjected to descrambling and correlation detection. Unlike the prior art, in the present embodiment, correlation detection is performed using only Walsh codes in the signature sequence group corresponding to the low speed range. Similarly, if the detection signal is greater than the decision threshold, it is determined that the reverse access prefix is acquired, otherwise, it is determined that the reverse access prefix is not acquired.
In addition, in this embodiment, two or more speed ranges and signature sequence groups corresponding to the speed ranges may be provided, and the base station may perform detection using different block methods on reverse access prefixes generated by signature sequence groups corresponding to speed ranges other than the lowest speed range, wherein the higher speed range is detected using a smaller block method, so that the block size is suitable for the change situation of the reverse channel at different speeds, and the best effect is achieved. Three speed ranges can be set: a low speed range, a higher speed range, and a high speed range and their respectively corresponding set of signature sequences. When detecting reverse access, the base station may divide each 4 consecutive symbols of a reverse access prefix generated by the signature sequence group corresponding to the higher speed range into 1 block, perform correlation detection with the signature sequence group corresponding to the higher speed range, divide each 2 consecutive symbols of the reverse access prefix generated by the signature sequence group corresponding to the high speed range into 1 block, and perform correlation detection with the signature sequence group corresponding to the high speed range. Because only one signature sequence group is used for carrying out related detection on each blocking mode, the detection efficiency is improved.
In the present embodiment, the access prefix technology of different time domain lengths is transmitted in the center of a cell and at the edge of the cell in combination, so as to optimize the performance of the entire communication system.
In this embodiment, the signature sequences are divided into two types in advance, one is a long signature sequence, such as 1024-bit Walsh code, and the reverse access prefix generated according to the signature sequence occupies a longer time domain and is transmitted by being carried on 8 OFDM symbols; the other is a short signature sequence, such as 512-bit Walsh code, and the reverse access prefix generated from the signature sequence occupies a short time domain and can be transmitted over 4 OFDM symbols. The wireless terminal at the edge of the cell adopts the long signature sequence, and the prefix occupying more time slices can obtain larger detection energy, so that the base station can capture the prefix sequence, the defect of limited power of the wireless terminal can be overcome, and the coverage range of signals is improved. The wireless terminal in the center of the cell adopts the short signature sequence to reduce the influence of time selectivity attenuation, thereby improving the detection performance of the wireless terminal moving at high speed in the center of the cell.
The long signature sequences are further grouped in this embodiment, with different sets of signature sequences corresponding to different speed ranges.
As shown in fig. 6, when initiating a reverse access, the wireless terminal enters step 601, determines to use a long signature sequence or a short signature sequence according to a distance between the wireless terminal and a base station, and determines to use a short signature sequence if the distance between the wireless terminal and the base station is less than a preset threshold, if the wireless terminal is in the center of a cell, enters step 602, the wireless terminal selects a short signature sequence from a group of short signature sequences, generates a short reverse access prefix according to the signature sequence, and sends the short reverse access prefix to the base station. If the wireless terminal is at the edge of the cell, that is, the distance between the wireless terminal and the base station is greater than the preset threshold, step 603 is entered, the wireless terminal determines the speed range according to the moving speed, selects a long signature sequence from the signature sequence group corresponding to the speed range, generates a long reverse access prefix according to the signature sequence, and sends the long reverse access prefix to the base station. By the method, the access performance of the cell edge high-speed wireless terminal is optimized, and the coverage range of the cell edge low-speed wireless terminal is not influenced.
The distance of the wireless terminal from the base station can be obtained in various ways: one is obtained by measuring the strength of the pilot, because the farther the wireless terminal is from the base station, the weaker the pilot will be, the distance between the wireless terminal and the base station can be estimated by measuring the strength of the pilot; the other is that the current position is measured by a GPS device on the wireless terminal, and then the position of the base station is obtained from the broadcast information of the base station, and the distance between the wireless terminal and the base station can be calculated from the two positions.
Then, in step 604, at the receiving end, the base station performs detection on different signature sequence sets in different manners. The method comprises the following steps of detecting a short signature sequence group and a long signature sequence group corresponding to a low-speed range by directly using the mode of the prior art; and detecting the long signature sequence group corresponding to the high-speed range by using a block division mode. The block detection method can be referred to the first embodiment. The received signal may be detected by attempting with each signature sequence set, with the signature sequence with the largest coherent energy as the final result.
The third embodiment of the present invention also relates to a method for initiating and detecting reverse access, which is substantially the same as the first embodiment, and the difference is that in the present embodiment, after a signature sequence is selected, a wireless terminal interleaves the signature sequence during initiating reverse access, and then generates a reverse access prefix according to the interleaved signature sequence to transmit the reverse access prefix to a base station, thereby improving the capability of resisting channel time selectivity fading and frequency selectivity fading; accordingly, the base station needs to perform de-interleaving processing on the reverse access prefix before detecting the reverse access prefix. When interleaving a signature sequence to be block-detected, the wireless terminal interleaves each block using the same block-division method as that used by the network side. For example, in the high-speed range, since the signature sequence length is 1024 bits and the detection is performed in blocks of 512 bits on the network side, the signature sequences are also divided into two blocks of 512 bits on the radio terminal side, and the same interleaver is used for each block to perform interleaving. When interleaving is used, the blocks received at the network side may not overlap.
In practical application, an interleaver may be added after scrambling and before DFT to interleave the signature sequence, as shown in fig. 7; alternatively, the interleaver may be added after the Walsh code selector before scrambling, as shown in fig. 8; alternatively, if there is no scrambled portion, an interleaver is added between the Walsh code selector and the DFT, as shown in FIG. 9. The length of the interleaver may be identical to the size of the block detected by the block.
Fig. 10 shows a comparison of simulation results of the present invention and the prior art, where the curve with asterisks is the packet loss rate of the present invention and the curve with circles is the packet loss rate of the prior art. The packet loss rate is 10-3In the scheme of the invention, the signal-to-noise ratio is higher than 1dB in the prior art, and therefore, by grouping the signature sequences, using different signature sequence groups in different speed ranges and receiving the high-speed signature sequence groups in a blocking mode at the network side, the packet loss rate of reverse access of the high-speed wireless terminal can be obviously reduced, and the performance of a reverse access channel is improved to a great extent. Wherein, the simulation conditions are as follows: moving speed of wireless terminal: 120 km/h; and (3) channel model: VA 120; false alarm probability: 0.1 percent.
A fourth embodiment of the present invention relates to a method for initiating and detecting reverse access, and is substantially the same as the third embodiment except that the third embodiment uses the same interleaver interleaving for different blocks in the same signature sequence, whereas the fourth embodiment uses the same or different interleaver interleaving for different blocks in the same signature sequence, and the interleavers used for different signature sequences may be different. For example, the signature sequence group includes a positive symmetric signature sequence AA and a negative symmetric signature sequence AB, where B ═ a and A, B respectively represent bit strings of a certain length. The same interleaver can be used for the front and back parts of AA and different interleavers can be used for the front and back parts of AB, so that AA and AB can be distinguished by the difference of the interleavers during detection.
When the network side carries out de-interleaving processing on the received reverse access prefix, all possible de-interleaving modes are respectively tried to carry out de-interleaving on different blocks.
Specifically, a 1024-bit Walsh code as a signature sequence is divided into two 512-bit code segments, and the two 512-bit code segments are interleaved by 512-point interleavers. After interleaving, the OFDM symbols are mapped to 4 consecutive OFDM symbols after DFT. The interleaving pattern of the interleaver that interleaves the two segments depends on the Walsh code being transmitted, and the same interleaver or different interleavers, each representing a different Walsh code, can be selected. For example, one interleaver is used for symmetric Walsh codes and another interleaver is used for anti-symmetric Walsh codes. I.e. using different interleavers. This has the advantage that different Walsh codes can be distinguished at the receiving end by different interleavers.
A fifth embodiment of the present invention is also directed to a method of initiating and detecting reverse access, and the present embodiment is substantially the same as the first embodiment except that in the first embodiment, all signature sequences in the signature sequence groups corresponding to different speed ranges are long signature sequences, in the present embodiment, a signature sequence in a signature sequence group corresponding to a lowest speed range is a long signature sequence, and signature sequences in signature sequence groups corresponding to other speed ranges are short signature sequences, wherein the higher the signature sequence in the signature sequence group corresponding to the speed range, the shorter the signature sequence in the signature sequence group corresponding to the speed range, the longer the reverse access prefix is generated by the wireless terminal in the long signature sequence group corresponding to the speed range from the selected long signature sequence; the wireless terminal with the speed range corresponding to the short signature sequence group repeats the selected short signature sequence on the time domain for multiple times to generate a long reverse access prefix; wherein, the long reverse access prefix generated by the short signature sequence is equal to the reverse access prefix generated by the long signature sequence. The network side continuously divides the reverse access prefix into blocks according to OFDM symbols according to the length and the repetition times of the received signature sequence, the reverse access prefix carried on each block corresponds to one signature sequence, and therefore, the correlation detection is carried out by taking each signature sequence in the prefixes as a unit, and the best effect is achieved during the detection. And averaging or summing the detection values of the plurality of signature sequences, comparing the detection values with a judgment threshold value, and judging that the reverse access prefix is captured if the detection values are greater than the judgment threshold value. Here, the reverse access prefix of the lowest speed range wireless terminal may be regarded as block detection in which the number of blocks is 1 or no block detection is performed.
The description will be given taking Walsh codes as the signature sequence as an example: two speed ranges, a high speed range and a low speed range are preset, wherein the low speed range corresponds to a long signature sequence group, signature sequences in the group are 1024-bit Walsh codes, the high speed range corresponds to a short signature sequence group, and the signature sequences in the group are 512-bit Walsh codes.
In practical applications, the wireless terminal corresponding to the high speed range is selected from the following Walsh codes Walsh0 512,Walsh1 512,Walsh2 512,...,WalshNs-1 512One of them is selected, and after the selected Walsh code is repeated for 1 time, the Walsh code whose length is 1024 bits, i.e. Walsh code is obtained0 1024,Walsh1 1024,Walsh2 1024,...,WalshNs-1 1024. And respectively modulating the first half part and the second half part of the repeated Walsh code with the length of 1024 bits to the first half part and the second half part of the reverse access prefix time domain signal, and transmitting the reverse access prefix time domain signal to a network side.
The remaining 512-bit Walsh codes are spread into 1024-bit subcodes, i.e., (Walsh)Ns 1024,Walsh512+Ns 1024),(WalshNs+1 1024,Walsh512+Ns+1 1024),(WalshNs+2 1024,Walsh512+Ns+2 1024),...,(Walsh511 1024,Walsh512+511 1024). The wireless terminal corresponding to the low speed range selects one generated reverse access prefix from the 1024-bit sub-codes and transmits the reverse access prefix to the network side.
The number proportion of Walsh codes in the two signature sequence groups is determined by Ns. The length of the reverse access prefix generated after the 512-bit Walsh code is repeated is the same as that of the reverse access prefix generated by the 1024-bit Walsh code.
A sixth embodiment of the present invention relates to a method of initiating and detecting reverse access, and is substantially the same as the first embodiment except that in the first embodiment, signature sequences in the signature sequence group corresponding to different speed ranges are all long signature sequences, in the present embodiment, signature sequences in the signature sequence group corresponding to each speed range are short signature sequences, the wireless terminal generates a long reverse access prefix by repeating the selected short signature sequences a plurality of times in the time domain, and the generated long reverse access prefix has the same length as the reverse access prefix generated in the first embodiment.
In this embodiment, one short signature sequence group may be separately provided, and the length of the short signature sequence in the short signature sequence group may be the same as or different from that of the short signature sequence group corresponding to each speed range. According to the distance between the wireless terminal and the base station, if the distance between the wireless terminal and the base station is smaller than a preset threshold, if the wireless terminal is in the center of a cell, selecting a short signature sequence from the short signature sequence, generating a short reverse access prefix according to the short signature sequence, and sending the short reverse access prefix to a network side; if the distance between the wireless terminal and the base station is larger than the preset threshold, determining the speed range according to the self moving speed, selecting a short signature sequence from the signature sequence group corresponding to the speed range, and repeatedly generating a reverse access prefix to send the short signature sequence to the network side on the time domain.
A seventh embodiment of the present invention also relates to a method for initiating and detecting reverse access, which can be based on any one of the first to sixth embodiments, and in this embodiment, the network side further allocates the same frequency resource and/or timeslot resource and/or spreading code resource to the wireless terminals corresponding to the same speed range and/or the distance between the wireless terminals and the base station, according to the speed range corresponding to the wireless terminals and/or the distance between the wireless terminals and the base station. The wireless terminal sends the reverse access prefix through the corresponding frequency resource and/or time slot resource and/or spread spectrum code resource according to the speed range and/or the distance between the wireless terminal and the base station. The network side determines the speed range of the wireless terminal sending the reverse access prefix according to the frequency resource and/or the time slot resource and/or the spread spectrum code resource for transmitting the reverse access prefix, and detects the reverse access prefix by using the block mode corresponding to the speed range.
For example, a high-speed range and a low-speed range are currently set, a network side allocates a frequency 1 to a wireless terminal whose distance from a base station is smaller than a preset threshold, allocates a frequency 2 to a wireless terminal whose distance from the base station is greater than the preset threshold and corresponds to the high-speed range, allocates a frequency 3 to a wireless terminal whose distance from the base station is smaller than the preset threshold and corresponds to the low-speed range, and different wireless terminals transmit reverse access prefixes on corresponding frequencies according to the distance from the wireless terminals to the base station and the speed of the wireless terminals. The network side can adopt the detection mode of the prior art to the reverse access prefix received from the frequency 1 according to the transmission frequency; a multi-block detection mode is used for the reverse access prefix received from the frequency 2; for the reverse access prefix received from the frequency 3, a whole block detection mode is used. Specific blocking detection methods (including both multi-block and whole-block detection) can be seen in the first embodiment. In the embodiment, the network side can determine the adopted block detection mode without performing complex judgment, so that the detection operation of the network side is simplified.
In addition, in order to improve the resource utilization rate, the network side may periodically detect the utilization rate of the allocated resources of the wireless terminals with different speed ranges and/or different distances from the base station, and adjust and allocate frequency resources and/or timeslot resources and/or spreading code resources for the wireless terminals with different speed ranges and/or different distances from the base station.
An eighth embodiment of the present invention relates to a method for initiating and detecting a reverse access, and is substantially the same as the seventh embodiment except that in the present embodiment, a reverse access prefix generated from a signature sequence further includes a cyclic prefix and a guard time. Reverse access prefixes generated by wireless terminals corresponding to different speed ranges contain guard times of different lengths. Considering that the coverage area of the low-speed user is generally required to be higher by the system, the reverse access prefix generated by the wireless terminal corresponding to the higher speed range may include a shorter guard time, and the reverse access prefix generated by the wireless terminal corresponding to the lower speed range may include a longer guard time. Or, considering that the propagation delay spread of the wireless terminal is large when the speed of the wireless terminal is high, the reverse access prefix generated by the wireless terminal corresponding to the higher speed range may include a longer guard time, and the reverse access prefix generated by the wireless terminal corresponding to the lower speed range may include a shorter guard time.
A ninth embodiment of the present invention relates to a method for initiating and detecting a reverse access in the same manner, and the present embodiment is substantially the same as the eighth embodiment. The difference is that in the eighth embodiment, the reverse access prefixes generated by the wireless terminals corresponding to different speed ranges include guard times of different lengths; in the present embodiment, the reverse access prefixes generated by the wireless terminals having different distances from the base station include guard times and cyclic prefixes having different lengths.
If the distance between the wireless terminal and the base station is greater than the preset threshold, the protection time and the cyclic prefix contained in the reverse access prefix generated by the wireless terminal are longer; if the distance between the wireless terminal and the base station is less than the preset threshold, the protection time and the cyclic prefix contained in the reverse access prefix generated by the wireless terminal are shorter.
A tenth embodiment of the present invention is directed to a method of initiating and detecting reverse access. In this embodiment, wireless terminals with different moving speeds select signature sequences from the same signature sequence group, the signature sequences in the signature sequence group are short signature sequences, and different wireless terminals randomly select different short signature sequences. And repeating the selected short signature sequence on the time domain for multiple times to generate a reverse access prefix and sending the reverse access prefix to the network side. The length of the short signature sequence is determined by the maximum moving speed which needs to be supported by the network side under certain target performance, and the larger the maximum moving speed is, the shorter the length of the short signature sequence is. The repetition times of the short signature sequence in the time domain is determined by the length of the short signature sequence, the shorter the length of the short signature sequence is, the larger the repetition times is, and the lengths obtained after the short signature sequences with different lengths are repeated in the time domain are the same, and are usually 1024 bits.
For example, the short signature sequence in the signature sequence group has a length of 512 bits, and the short signature sequence may be a 512-bit Walsh code, a GCL code, or a CAZAC code, and the wireless terminal repeats the short signature sequence twice to form 1024 bits, and generates a reverse access prefix from the 1024-bit repeated signature sequence and transmits the reverse access prefix to the network side. Alternatively, the short signature sequence may be the first 512 Walsh codes in a Walsh code group having a length of 1024 bits, and since the first 512 bits and the last 512 bits of each Walsh code are symmetrical among the first 512 Walsh codes, which is equivalent to repeating the 512-bit Walsh codes once, the short signature sequence can be directly used.
On the network side, as shown in fig. 11, the base station detects the received reverse access prefix in a non-overlapping block manner and a whole block manner, and if any detection energy in the detection results obtained by the non-overlapping block detection or the whole block detection exceeds the decision threshold, it is considered that the reverse access prefix is captured. In the detection of non-overlapping block mode, the base station firstly carries out continuous block division on the reverse access prefix according to OFDM symbols, all blocks are not overlapped, the reverse access prefix carried on each block is respectively subjected to relevant detection, the detected relevant energy of each block is added or averaged and then compared with a decision threshold value, and if the energy is greater than the decision threshold value, the reverse access prefix is determined to be captured. The detection in the monoblock mode can be regarded as a special case of the detection in the block mode, the base station does not need to block the reverse access prefix, and directly carries out related detection on the reverse access prefix, and if the detected related energy is greater than a judgment threshold value, the reverse access prefix is judged to be captured. By detecting the two methods, the wireless terminals with different moving speeds can be better met, when the moving speed of the terminal is higher, the detection effect can be improved by overlapping and partitioning detection, when the moving speed of the terminal is lower, a better detection effect can be obtained by integral detection, the packet loss rate of reverse access of the wireless terminal can be reduced by detecting from two aspects, and the performance of a reverse access channel is improved.
In order to improve the capability of resisting channel time selectivity fading and frequency selectivity fading, in this embodiment, the wireless terminal may also interleave the short signature sequence first, and then generate a reverse access prefix according to the interleaved short signature sequence to send to the network side, where the interleaving manners for different short signature sequences are the same or different. The wireless terminal may interleave after repeating the short signature sequence or before repeating.
Correspondingly, before the base station performs block-mode detection or whole-block-mode detection on the reverse access prefix, the reverse access prefix needs to be de-interleaved first.
An eleventh embodiment of the present invention is substantially the same as the tenth embodiment, and in the eleventh embodiment, a wireless terminal of different speed randomly selects a signature sequence from the same signature sequence group as well, but differs from the tenth embodiment in that the signature sequence in the signature sequence group is a short signature sequence, and the wireless terminal generates a reverse access prefix by repeating the short signature sequence a plurality of times in the time domain; in the present embodiment, the signature sequences in the signature sequence group are long signature sequences and are not required to have a repetitive structure. For example, all Walsh codes in the set of Walsh codes of length 1024. The wireless terminal may generate the reverse access prefix directly from the selected signature sequence.
On the network side, as shown in fig. 12, the base station detects the received reverse access prefix in an overlapping block manner and a whole block manner, and if any of the detection energies obtained by the overlapping block detection or the whole block detection exceeds a judgment threshold, it is considered to capture the reverse access prefix. Through two detection methods, different moving speeds of the wireless terminal can be well adapted, when the moving speed of the terminal is high, the detection effect can be improved through overlapped block detection, when the moving speed of the terminal is low, a better detection effect can be obtained through whole block detection, the packet loss rate of reverse access of the wireless terminal can be reduced through detection in two aspects, and the performance of a reverse access channel is improved.
A twelfth embodiment of the present invention is directed to a method of initiating and detecting reverse access. In this embodiment, at least two distance ranges are preset, and each distance range corresponds to a different length of the guard time and the cyclic prefix, and a different resource range. Wherein, the farther the distance range from the base station, the longer the guard time and the cyclic prefix. The resource range may be a range of frequency resources, a range of time slot resources, or a range of spreading code resources.
As shown in fig. 13, when the wireless terminal needs to initiate a reverse access, step 1301 is entered, and the wireless terminal determines a distance range according to a distance between itself and the base station. The wireless terminal can obtain the current position of the wireless terminal according to the global positioning system, and then calculate the distance between the wireless terminal and the base station according to the base station position obtained from the base station broadcast; alternatively, the distance between the wireless terminal and the base station is obtained by measuring the strength of the pilot.
Then, step 1302 is entered, and a reverse access prefix is generated by using the cyclic prefix and the guard time with the length corresponding to the distance range. Because the longer the protection time and the longer the cyclic prefix corresponding to the distance range from the base station, the wireless terminal far away from the base station can well keep the orthogonality of the reverse access prefix, and the interference in the transmission process is avoided.
Then, step 1303 is entered, the wireless terminal sends the generated reverse access prefix to the network side through the transmission resource in the resource range corresponding to the distance range where the wireless terminal is located.
Then, step 1304 is performed, in which the network side determines a distance range in which the wireless terminal transmitting the reverse access prefix is located according to a resource range in which the resource transmitting the reverse access prefix is located, and detects the reverse access prefix according to the guard time and the cyclic prefix length corresponding to the distance range.
In order to improve the resource utilization rate, the network side can detect the resource utilization rates of the wireless terminals in different distance ranges at regular time and adjust the resource ranges corresponding to the distance ranges. For example, if there are fewer wireless terminals in a distance range closer to the base station and the resource utilization rate is low, the resource range can be reduced, and the part of resources can be allocated to a distance range farther from the base station, thereby avoiding the vacancy of transmission resources.
A thirteenth embodiment of the present invention is directed to a method of initiating and detecting a reverse access, which is substantially the same as the twelfth embodiment except that in the thirteenth embodiment, different distance ranges correspond to different lengths of guard time and cyclic prefix; in the present embodiment, the different distance ranges correspond to different modulation schemes on the physical channel, for example, the wireless terminal in the distance range closer to the base station adopts the CDMA modulation scheme, and the wireless terminal in the distance range farther from the base station adopts the OFDMA modulation scheme, so as to improve the orthogonality of the reverse access prefix and increase the access success rate.
A fourteenth embodiment of the present invention is directed to a method for initiating and detecting a reverse access, which is substantially the same as the twelfth or thirteenth embodiment except that different distance ranges are preset in the twelfth or thirteenth embodiment, and different speed ranges are preset in the present embodiment, and each distance range corresponds to a guard time and a cyclic prefix with different lengths, or corresponds to a different physical channel modulation method. The wireless terminals with different moving speeds generate reverse access prefixes with different protection time and cyclic prefix lengths to be sent to the network side, or the reverse access prefixes are modulated on a physical channel through different modulation modes to be sent to the network side.
Wherein, the moving speed of the wireless terminal is the moving speed of the wireless terminal at the current moment or the average speed in the latest fixed-length time period.
A fifteenth embodiment of the present invention relates to a wireless terminal, as shown in fig. 14, including a storage unit configured to store at least two speed ranges and signature sequence groups respectively corresponding thereto; the group selection unit is used for determining the speed range according to the moving speed of the wireless terminal and determining the corresponding signature sequence group according to the speed range; a code selection unit for selecting one signature sequence from the determined set of signature sequences; a scrambling unit, which is used for scrambling the selected signature sequence; and a sending unit, configured to generate a reverse access prefix according to the scrambled signature sequence and send the reverse access prefix to the network side. By using different signature sequence groups according to different moving speeds, the network side can receive the high-speed signature sequence group in a blocking mode, so that the packet loss rate of reverse access of the high-speed wireless terminal is reduced, and the performance of a reverse access channel is improved.
Besides the above several main functional units, the transmitting unit also includes DFT module and OFDM modulator, and a scrambling unit is connected in series between the code selecting unit and the DFT module for scrambling the selected signature sequence.
In the present embodiment, the signature sequence in the signature sequence group corresponding to each speed range stored in the storage unit is a long signature sequence. The storage unit may further store a short signature sequence group including at least one short signature sequence.
If the storage unit stores the short signature sequence group, when the distance between the wireless terminal and the base station is larger than a preset threshold, the group selection unit determines the speed range according to the moving speed of the wireless terminal and selects the corresponding signature sequence group according to the speed range. When the distance between the wireless terminal and the base station is smaller than a preset threshold, the group selection unit selects the short signature sequence group, so that the detection performance of the wireless terminal moving at a high speed in the center of the cell is improved.
Or the signature sequences in the signature sequence group corresponding to each speed range are short signature sequences; the sending unit sends the selected short signature sequence to the network side by repeating the multiple growing reverse access prefixes in the time domain.
Or the signature sequence in the signature sequence group corresponding to the lowest speed range is a long signature sequence, and the signature sequences in the signature sequence groups corresponding to other speed ranges are short signature sequences, wherein the signature sequences in the signature sequence group corresponding to the higher speed range are shorter. The sending unit generates a long reverse access prefix according to the selected long signature sequence and sends the long reverse access prefix on the network side when the speed range of the wireless terminal corresponds to the long signature sequence group; when the speed range of the wireless terminal corresponds to the short signature sequence group, the selected short signature sequence is repeatedly grown for multiple times in the time domain to send a reverse access prefix to a network side; wherein, the long reverse access prefix generated by the short signature sequence is equal to the reverse access prefix generated by the long signature sequence.
In response to the second or third case, the storage unit may also store a short signature sequence group including at least one short signature sequence, where the short signature sequence in the short signature sequence group is used to generate the short reverse access prefix. If the distance between the wireless terminal and the base station is greater than the preset threshold, the group selection unit determines the speed range according to the moving speed of the wireless terminal, and selects the corresponding signature sequence group according to the speed range, the code selection unit selects one signature sequence from the corresponding signature sequence group, and the sending unit generates a long reverse access prefix according to the selected signature sequence and sends the long reverse access prefix to the network side; if the distance between the wireless terminal and the base station is less than the preset threshold, the group selection unit selects the short signature sequence group, the code selection unit selects a short signature sequence from the corresponding short signature sequence group, and the sending unit generates a short reverse access prefix according to the selected short signature sequence and sends the short reverse access prefix to the network side.
In this embodiment, the transmitting unit may further include a cyclic prefix and a guard time in the reverse access prefix generated from the signature sequence.
Considering that the coverage area of the low-speed user is generally required to be higher by the system, the protection time included in the reverse access prefix generated by the wireless terminal corresponding to the higher speed range can be made shorter, and the protection time included in the reverse access prefix generated by the wireless terminal corresponding to the lower speed range can be made longer.
Or, considering that the propagation delay spread of the wireless terminal is large when the speed of the wireless terminal is high, the protection time included in the reverse access prefix generated by the wireless terminal corresponding to the higher speed range may be longer, and the protection time included in the reverse access prefix generated by the wireless terminal corresponding to the lower speed range may be shorter.
Or, if the distance between the wireless terminal and the base station is greater than the preset threshold, the protection time and/or cyclic prefix contained in the reverse access prefix generated by the wireless terminal is longer; and if the distance between the wireless terminal and the base station is less than the preset threshold, the reverse access prefix generated by the wireless terminal contains shorter protection time and/or cyclic prefix.
In addition, the storage unit of the wireless terminal may further store different frequency resources and/or time slot resources and/or spreading code resources allocated by the network side to wireless terminals with different speed ranges and/or different distances from the base station according to the speed range corresponding to the wireless terminal and/or the distance from the wireless terminal to the base station. And the transmitting unit transmits the reverse access prefix of the wireless terminal through corresponding frequency resources and/or time slot resources and/or spread spectrum code resources according to the speed range of the wireless terminal and/or the distance between the wireless terminal and the base station.
In the wireless terminal according to this embodiment, an interleaver may be connected in series between the code selection unit and the transmission unit, and used to interleave the selected signature sequence. The transmitting unit generates a reverse access prefix according to the interleaved signature sequence and transmits the reverse access prefix to the network side, so that the capacity of resisting channel time selectivity attenuation and frequency selectivity attenuation is improved.
A sixteenth embodiment of the present invention relates to a network-side device including, as shown in fig. 15, a storage unit that stores at least two speed ranges and signature sequence groups respectively corresponding thereto; a receiving unit for receiving a reverse access prefix signal from a wireless terminal; and a block detection unit for detecting the reverse access prefix signal received by the receiving unit in a block mode. The high-speed signature sequence group is received in a blocking mode, so that the packet loss rate of reverse access of the high-speed wireless terminal is reduced, and the performance of a reverse access channel is improved. The reverse access prefixes generated by the signature sequence groups corresponding to the speed ranges except the lowest speed range are detected by using different block modes, and the higher speed range is detected by using the smaller block mode, so that the block size is suitable for the change situation of the reverse channel at different speeds, and the best effect is achieved.
Wherein, the block detection unit further comprises: a block module for continuously blocking the reverse access prefix according to OFDM symbols; a block detection module for respectively carrying out relevant detection on the reverse access prefix loaded on each block; and the judgment module is used for comparing the detected correlation energy of each block after adding or averaging the correlation energy with a judgment threshold value, and judging that the reverse access prefix is captured if the comparison result is greater than the judgment threshold value.
The receiving unit also comprises an OFDM demodulator and an IDFT module, wherein the OFDM demodulator performs OFDM demodulation on the received signals and then transmits the signals to the IDFT module for inverse discrete Fourier transform and then outputs the signals.
And also contains a descrambling unit and a de-interleaver, and performs the reverse operation of the scrambling unit and the interleaver in the wireless terminal.
In addition to the above main units, the network side device of this embodiment may further include a deinterleaving unit configured to deinterleave the reverse access prefix signal received by the receiving unit and output the deinterleaved reverse access prefix signal to the block detection unit.
There may also be the following: in the storage unit, the signature sequence in the signature sequence group corresponding to the lowest speed range is a long signature sequence, and the signature sequences in the signature sequence groups corresponding to the other speed ranges are short signature sequences, wherein the signature sequences in the signature sequence group corresponding to the higher speed range are shorter.
And correspondingly, the blocking module continuously blocks the reverse access prefix according to the OFDM symbols according to the length and the repetition times of the signature sequence, so that the reverse access prefix carried on each block corresponds to one signature sequence, and the correlation detection is carried out by taking each signature sequence in the prefixes as a unit, thereby achieving the best effect during the detection.
In addition, the receiving unit may also determine a speed range in which the wireless terminal that transmits the reverse access prefix is located according to the frequency resource and/or the timeslot resource and/or the spreading code resource that transmits the reverse access prefix, and instruct the block detection unit to detect the reverse access prefix using a block method corresponding to the speed range. The corresponding block mode can be directly adopted for detection without other complex judgment, so that the detection operation of the network side is simplified.
While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
A seventeenth embodiment of the present invention is directed to a wireless terminal including: and repeating the short signature sequence at least once in the time domain to generate a reverse access prefix and sending the reverse access prefix to a network side. The length of the short signature sequence is determined by the maximum moving speed of the wireless terminal supported by the network side, and the length of the short signature sequence is shorter when the maximum moving speed is higher. The repetition times of the short signature sequence is determined by the length of the short signature sequence, the shorter the length of the short signature sequence is, the larger the repetition times is, and the lengths obtained after the short signature sequences with different lengths are repeated on a time domain are the same. By repeating the short signature sequence in the time domain, the phenomenon of antisymmetric front half and rear half of the signature sequence can be avoided, for example, in a 1024-bit Walsh code group, the first 512 bits and the second 512 bits of the latter 512 Walsh codes form antisymmetric, which easily causes that the network side cannot identify the reverse access prefix generated by the Walsh codes, and by repeating the short signature sequence in the time domain, the problem can be well solved, and the success rate of capturing the reverse access prefix by the network side is improved.
An eighteenth embodiment of the present invention relates to a network-side device including: a block detection unit for detecting the received reverse access prefix in a block mode; a whole block detection unit for detecting the received reverse access prefix in a whole block mode; and the judging unit judges that the reverse access prefix is captured when at least one detection result is greater than a judging threshold value according to the detection results of the blocking detection unit and the whole block detection unit. By detecting the two methods, the wireless terminals with different moving speeds can be better met, when the moving speed of the terminal is higher, the detection effect can be improved by overlapping and partitioning detection, when the moving speed of the terminal is lower, a better detection effect can be obtained by integral detection, the packet loss rate of reverse access of the wireless terminal can be reduced by detecting from two aspects, and the performance of a reverse access channel is improved.
Wherein, this blocking detecting element still contains: a block module for continuously blocking the reverse access prefix according to OFDM symbols; a module for respectively carrying out relevant detection on the reverse access prefix loaded on each block; and the module compares the detected correlation energy of each block with a judgment threshold value after adding or averaging, and judges that the reverse access prefix is captured if the correlation energy of each block is greater than the judgment threshold value.
In addition, the detection of the blocking mode can be the detection of a non-overlapping blocking mode, and when the blocking module carries out continuous blocking, all blocks are not overlapped; alternatively, the block-wise detection may be an overlapped block-wise detection, and when the block-wise module performs continuous block-wise division, the blocks may be overlapped with each other.
A nineteenth embodiment of the present invention relates to a wireless terminal including: the storage unit is used for storing at least two distance ranges, protection time and/or cyclic prefix lengths corresponding to the distance ranges, and resource ranges corresponding to the distance ranges; a distance detection unit for obtaining the current position of the wireless terminal according to the global positioning system and calculating the distance between the wireless terminal and the base station according to the base station position obtained from the base station broadcast; alternatively, the distance between the wireless terminal and the base station is obtained by measuring the strength of the pilot. And the transmitting unit is used for determining the distance range according to the distance between the wireless terminal and the base station, generating a reverse access prefix by adopting the protection time and/or the cyclic prefix with the length corresponding to the distance range and transmitting the reverse access prefix to the network side. The transmitting unit transmits the reverse access prefix through the transmission resource in the resource range corresponding to the distance range of the wireless terminal.
A twentieth embodiment of the present invention relates to a network-side device, including: the storage unit is used for storing at least two distance ranges, resource ranges respectively corresponding to the distance ranges, and protection time and/or length of a cyclic prefix respectively corresponding to the distance ranges; the judging unit is used for determining the distance range of the wireless terminal for transmitting the reverse access prefix according to the resource range of the resource for transmitting the reverse access prefix; and the detection unit is used for detecting the reverse access prefix according to the protection time and/or the cyclic prefix length corresponding to the distance range. Wherein the resource range may be a range of frequency resources, a range of time slot resources, or a range of spreading code resources.
In addition, in order to improve the resource utilization rate, the network side device further includes: and a unit for adjusting the resource range corresponding to each distance range according to the resource utilization rate of the wireless terminal in different distance ranges. For example, if there are fewer wireless terminals in a distance range closer to the base station and the resource utilization rate is low, the resource range can be reduced, and the part of resources can be allocated to a distance range farther from the base station, thereby avoiding the vacancy of transmission resources.