CN1965492A - A transmitter and receiver for ultra-wideband OFDM signals employing a low-complexity CDMA layer for bandwidth expansion - Google Patents
A transmitter and receiver for ultra-wideband OFDM signals employing a low-complexity CDMA layer for bandwidth expansion Download PDFInfo
- Publication number
- CN1965492A CN1965492A CNA2005800161500A CN200580016150A CN1965492A CN 1965492 A CN1965492 A CN 1965492A CN A2005800161500 A CNA2005800161500 A CN A2005800161500A CN 200580016150 A CN200580016150 A CN 200580016150A CN 1965492 A CN1965492 A CN 1965492A
- Authority
- CN
- China
- Prior art keywords
- code element
- ofdm code
- sequence
- increases
- ofdm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Landscapes
- Mobile Radio Communication Systems (AREA)
Abstract
A method and apparatus for transmitting and receiving high-bandwidth OFDM signals, while limiting the complexity of the OFDM signal processing is described. Bandwidth expansion is achieved by repetition of whole OFDM symbols with the polarity of repetitions determined by a long PN code. This technique ensures a perfectly white spectrum. Use of zero-suffix OFDM symbols allows a large tolerance to multipath channels, even while maintaining a single, low-rate RAKE finger for despreading in the receiver.
Description
Known and advise using OFDM to be used for the ultra wideband transmissions of high-rate wireless individual domain network (PAN).Because from the additional emission of the electronic equipment that exists today, these systems are proposed and are operated in below the limit range, in any case but, it will be provided at the data rate up to 480MBps and the 110Mbps on 10 meters scopes in 3 meters scopes.For rational complexity, such system can be made into the primary bandwidth that takies 528MHz, and uses the extra play of a frequency hopping simultaneously, so that shared bandwidth multiply by integral multiple (3 times typically).
Also known and advised using pure Direct swquence spread spectrum system, utilization is about the spreading rate of per second 1,400,000,000 chips and relevant RAKE receiver or channel matched filter, and described RAKE receiver or channel matched filter must be carried out multiplication and accumulating operation with above-mentioned spreading rate.In addition, need obtain low error substrate (floor) such as the such equalizer of DFF mostly.
Though work finely on the combination principle of OFDM and frequency hopping, management organization also not like this interference characteristic and the power level that allowed of system make decision.Be set up because the average power that allowed is the average power spectrum density according to signal, so in fact frequency hopping has improved N to peak power doubly, wherein N is the frequency hopping number of times, and this may make the interference effect to some broadband receiver increase same multiple.For this has relation especially such as the such broadband satellite receiver system of C-band satellite retroreflector (satellite dish).Under the situation that provides this potential constraints, seeking to allow to expand the bandwidth of ofdm signal but the method that do not rely on frequency hopping.
Scheme based on the replacement of Direct swquence spread spectrum has been proposed, but the supposition correlator must be to surpass the speed operation of per second 1,000,000,000 samples, and suppose to adopt Digital Signal Processing, need a plurality of correlators to form acceptable RAKE receiver, the signal processing complexity of this solution may be unacceptable so.Because Moore law, digital circuit complexity reduce and reduce with the IC basic production process dimension, so Digital Signal Processing is highly hope.
The signal waveform of being advised is the OFDM code element of sampled by repetition (upsample).With whole ofdm signal is that unit carries out repetition under time domain.For fear of by any spectral ripple that repeats to cause, adopt two measures:
1. use zero energy suffix to replace the Cyclic Prefix that in the OFDM code element, typically obtains.
2. the OFDM code element of Chong Fuing stands polarity inversion according to a long PN sequence known at the transmitter and receiver place.
Because in fact channel becomes during right and wrong on the length that repeats, so receiver can recover original OFDM code element by simple addition or subtraction according to known PN sequence.At last, carry out overlapping and sum operation, be applied to fast Fourier transform (FFT) with the constant characteristic of circulation of the expectation that forces sample for the OFDM code element of each despreading.
Behind process FFT, domain samples can be by making each frequency bin (frequency bin) quilt equilibrium divided by the complex conjugate in the corresponding storehouse of frequency domain channel valuation.Ground of equal value, the complex conjugate multiplication of same amount can be used to the phase shift that the derotation (deroate) is caused by channel under the situation that the demodulation such as M system PSK is not needed amplitude accuracy.
A kind of new understanding is: the up-sampling of the ofdm signal that is undertaken by repetition does not change needed IFFT and FFT throughput, but increases the bandwidth that takies really.The filtering of carrying out on frequency domain in transmitter remains in kilter by this new up-sampling process, makes it generally be suitable for outer emission of low band and spectrum radios flexibly.
Among the figure:
Fig. 1 is the transmitter block diagram according to principle described herein.
Fig. 2 is the receiver block diagram according to principle described herein.
Fig. 3 shows figure overlapping and that addition is handled.
Fig. 4 shows the exemplary signal graph that is launched envelope waveform.
Fig. 5 is the signal graph that shows the power spectral density (PSD) that is launched envelope waveform.
Fig. 6 shows the exemplary signal graph that is received envelope waveform.
Fig. 7 shows the exemplary signal graph that is launched the PSD of envelope waveform.
Fig. 8 is the signal graph that is presented at the output QPSK scatter diagram of receiver.
The transmitter block diagram of Fig. 1 shows a possible embodiment of transmitter section.Selected the QPSK modulation as an example.In Fig. 1, symbol "/2 " is used for representing a complex signal.
Always five pieces of representing with reference number 110 are known in this area: they comprise random information bit source, forward error correction coding, and the back is a qpsk modulator.The frequency bin of IFFT is filled the code element with QPSK.(randomly, can in direct current and frequency domain, want the other places of zero energy to insert zero.In addition, can insert pilot tone at this point.) added a zero energy suffix, its length is designed to be equal to or greater than the longest effective channel impulse response.
To one of challenge of UWB system is to take very large bandwidth in the boundary of acceptable hardware complexity.If do not take very large bandwidth, because of the extremely low signal power that is required that is transmitted, received signal becomes useless so.This challenge is solved by the utilized bandwidth expansion in the transmitter of Fig. 1.In the embodiment in figure 1, in being marked as the piece 111 of " by whole OFDM code element repeat to carry out up-sampling ", carry out the bandwidth expansion.The number of times that repeats each OFDM code element (the relevant cyclic suffix that comprises it) is relevant with embodiment.In one embodiment, can use 4 times, cause the identical multiple of bandwidth expansion.
Each copy of OFDM code element is inverted according to the currency of the PN sequence that is generated by bipolarity (+1 ,-1) PN maker 113 or is nonreversible.The index of PN sequence is incremented 1 for the OFDM code element of each transmission.In other words, the PN sequence rate is identical with the OFDM chip rate.In fact, do not use multiplier 115 as shown in Figure 1, the sign of the OFDM sample that each is cushioned can be inverted in buffer according to the current polarity of PN maker or be nonreversible.There is not the PN maker, then the OFDM code element repeats and will produce excessive " spectral ripple ", allow promptly that unmodified repeating will make the autocorrelation value of waveform depart from desirable Dirac (Di Lake) pulse in the time domain, the power of hint in frequency domain, power spectral density right and wrong white.
Represent the number of the sample of original information bit to increase multiple N corresponding to the repetition number of each the whole OFDM code element that in the piece 111 of Fig. 1, applies.Suppose that the OFDM symbol transformations that will repeat increases corresponding multiple N to the sampling rate of analog domain, then causes expanding (identical multiple N) with respect to the bandwidth of the situation that does not apply expansion.
In piece 111, use variable spread factor N, have corresponding increase in the speed of PN maker 113 the low-complexity bandwidth extension schemes that provides one to have factor N that may be variable is provided.By changing factor N, user data rate can be used to exchange expansion gain, the favourable scalability and the flexibility of end user data speed is provided, and keeps the identical bandwidth that takies simultaneously.The flexibility that is provided by the orthogonal variable spreading factor that uses in the 3G cell phone (OVSF) sign indicating number is provided in this flexibility.
The PN sequence only needs long enough, repeats on the value of the maximum support of up-sampling ratio N to guarantee to avoid.For simplicity, the phase place of PN sequence can be synchronized to the end of preamble at the starting end of the burst of OFDM code element.If want, different PN sequences can be used for the different piconet that shares out the work with same frequency spectrum, make the minimizing possibility of the cross-communication (cross-communication) between piconet.Yet, and do not require that employed PN sequence changes in time for given piconet or peer-to-peer communications session meeting.
Last step is the frequency displacement to suitable RF carrier frequency of digital to analogy conversion and baseband signal in the transmitter.What these steps were total represents with reference number 120, and they are all followed traditional scheme and do not need here and further elaborate.
The block diagram of Fig. 2 shows a receiver structure, receives the ofdm signal of bandwidth expansion under its situation that is designed to exist multipath delay to expand in radio-frequency channel.
In the first half of Fig. 2, total form representing of device quilt with a pair of AD converter and a complex sample behind a traditional direct down-conversion receiver with reference number 210.The remainder of this figure Lower Half has shown the example that the numerical signal of expection is handled.As an example, channel guess value and be to obtain synchronously from initial preamble (preamble) (suppose transmitter, but not shown).So complex sample at first is applied to preamble detection block 211, these preamble detection block 211 back adjoining lands have been followed synchronization blocks 213 and channel estimation block 215.The phase place of local PN sequence generator 217 and timing obtain from this initial synchronisation with this preamble.The polarity inversion of finishing in transmitter, reverse is marked as piece 221 digital multiplier 219 representatives before of " storage and N OFDM code element of addition ground combination " by directly being inserted in.
Bandwidth/rate reduces by aforesaid " storage and N OFDM code element of addition ground combination " piece 221 execution in the receiver.This computing is simple add operation, so have relatively low complexity.
The required cycle characteristics of FFT computing 225 after " overlapping and addition " piece 223 is responsible for creating and is used for.Idea is that the block of symbols that make to receive seems it to have experienced " circular convolution " of channel impulse response such.This is because the division of domain samples is equivalent to corresponding contrary circumference deconvolution process.
As shown in Figure 3, the program process that is adopted is to be taken at the OFDM code element to finish the sample that the back receives, and they are added on the sample of the respective number at OFDM code element starting end place.For example, if the OFDM code element is that 128 samples are long, 32 samples of zero energy suffix are followed in the back, then should be added on 32 samples of the OFDM code element that received at corresponding 32 samples of OFDM code element end.
Get back to Fig. 2, behind FFT (piece 225), division block 227 is carried out the division of each FFT storehouse and corresponding frequency domain channel guess value in frequency domain.As previously mentioned, this effect of channel impulse response of deconvoluting and reverse corresponding to circumference.In some cases, division can substitute with complex conjugate multiplication easily, such as the current example that wherein relates to the QPSK modulation.Represent with reference number 230 as total, after the QPSK demodulation, use common FEC algorithm and recover the Useful Information bit stream.
Fig. 4-8 is presented at illustrative waveforms and the power spectrum on each aspect in the communication link.On Fig. 4-8, one section mourning in silence the period corresponding to zero energy suffix is followed in each burst back.One group of four burst and their relevant zero energy suffix can with the identical duration that in alternative, is used in the past single OFDM code element and its associated cyclic prefix or zero energy suffix in send.Note comparing with the PSD that transmits of Fig. 5, the caused PSD of decline changes in receiver shown in Figure 7.Signal processing in the receiver comprises overlapping and sum operation, and it provides enough expansion gains, makes the information that is sent to be resumed (Fig. 8) with low-down error probability.
Alternative embodiment:
1. aforesaid transmitter and receiver, just single-tone piece (tone block) be set to zero so that the frequency spectrum that takies less than sampling rate.This uses the IFFT in the transmitter effectively, thereby obtains up-sampling and filtering in once-through operation.
2. aforesaid transmitter and receiver, just the size of OFDM code element can be dynamically adjusted with the corresponding increase of each OFDM code element repetition number.Therefore, when keeping sampling rate constant, the relative spreading gain of data rate can be adjusted on demand.
3. aforesaid transmitter and receiver, just modulation scheme is not fixed on QPSK, but can select according to available SNR.
4. aforesaid transmitter and receiver wherein allows length with zero energy suffix to be increased to equal but is not more than the length of the OFDM code element of energy supply.
5. aforesaid transmitter and receiver, wherein the length of zero energy suffix surpasses the length of the energy supply part of OFDM code element, so that ' sparse ' modulation scheme is suitable for low data rate.Overlapping and sum operation in the receiver will be subject to the length of the energy supply part of OFDM code element.
6. aforesaid receiver, but wherein overlapping and sum operation only are applied to the suffix sample above certain amplitude threshold.
7. aforesaid transmitter, it utilizes the power-saving technology during the zero energy part (zero energy suffix) of emission.Such power-saving can particularly be implemented in DAC in RF, simulation and mixed signal parts.
8. aforesaid receiver, it uses complex conjugate multiplication to replace complex division, to reach frequency domain channel equalization.
9. aforesaid receiver, wherein overlapping and addition is handled the improved equalization scheme of using such as MMSE and is substituted.
Use:
The present invention always can be applicable to the problem that spread spectrum is conciliate the spread spectrum OFDM waveform by low signal processing expense with for the high resilience of multipath channel effect.
A concrete application is the radio ultra wide band system that is used for two-forty, short-range communication link.Particularly, Current Standard work can select to utilize these technology as the measure that overcomes the management resistance (regulatory resistance) for Frequency Hopping Signal among the IEEE (802.15.3a).
The standard in wireless future that is used for cognitive and software dictates can be used the scheme such as here, selectively to take big bandwidth range according to main disturbed condition.Taking with irregular frequency spectrum flexibly is to be set to zero energy and available by the FFT storehouse of selecting in transmitter.
In view of above-mentioned advantage, the international standard that is used for the future of UWB can be selected modulation according to this technology.
Claims (25)
1. a Signalling method comprises: produce the OFDM code element; Repeating this OFDM code element produces and increases the expansion sequence; Selectively reversing, this increases the expansion sequence, to obtain showing the modified expansion sequence that increases of improved spectral characteristic; And launch this modification increase the expansion sequence.
2. the method for claim 1 comprises the suffix that can ignore energy is attached to this OFDM code element.
3. the process of claim 1 wherein that whole OFDM code element is selectively reversed.
4. the process of claim 1 wherein that whole OFDM code element is selectively reversed according to the PN sign indicating number.
5. the process of claim 1 wherein that the single-tone piece in the OFDM code element is set to zero, to realize frequency spectrum shaping.
6. the process of claim 1 wherein that the size and the repetition factor of OFDM code element dynamically change with opposite relation, keep constant sampling rate simultaneously.
7. the method for claim 1 comprises dynamically changing an applied modulation.
8. the method for claim 1 comprises the suffix that can ignore energy is applied to each OFDM code element.
9. the method for claim 8, the length that wherein can ignore the suffix of energy is not more than the length of the energy supply part of OFDM code element.
10. the method for claim 8, the length of suffix that wherein can ignore energy is greater than the length of the energy supply part of OFDM code element.
11. the method for claim 8 comprises for the active parts of selecting and carries out the power management step, so that during occurring ignoring the suffix of energy, provide less power to described active parts.
12. the method that signal receives comprises: receive a modified expansion sequence that increases, the expansion sequence that increases that wherein the OFDM code element is repeated and finally obtains is selectively reversed; The example that makes up the repetition of this OFDM code element obtains compound OFDM code element; And carry out transform operation to obtain the sequence of conversion for compound OFDM code element.
13. the method for claim 12 comprises the sequence of conversion is carried out the complex arithmetic division.
14. the method for claim 12 comprises the sequence of conversion is carried out complex conjugate multiplication.
15. the method for claim 13, wherein the sequence of conversion quilt is divided by channel guess value.
16. the method for claim 12, increasing of wherein revising expand intersperse between the repetition example that sequence is included in the OFDM code element, only launch period of insignificant energy therebetween, and wherein at Assemble Duration, the sample that occurs during the described period with corresponding to before the sample of OFDM code element combined.
17. the method for claim 16, the wherein said period surpasses the duration of OFDM code element, and the sample that wherein only equaling before, occurs during the first of the period of the duration of OFDM code element and corresponding to before the sample of OFDM code element combined.
18. the method for claim 16, the sample of the threshold amplitude that wherein only occurs during the described period and surpass regulation is with combined corresponding to the sample of the OFDM code element before each.
19. a communication transmitter comprises: the device that is used to produce the OFDM code element; Be used to repeat this OFDM code element and increase the device that expands sequence with generation; Being used for selectively reversing, this increases the expansion sequence to obtain showing the modified device that expands sequence that increases that improves spectral characteristic; And be used to launch this modified device that expands sequence that increases.
20. the equipment of claim 19 comprises the device that is used for the suffix that can ignore energy is attached to this OFDM code element.
21. the equipment of claim 19, wherein whole OFDM code element is selectively reversed.
22. the equipment of claim 19, wherein whole OFDM code element is selectively reversed according to the PN sign indicating number.
23. a communication control processor comprises: be used to receive a modified device that expands sequence that increases, the expansion sequence that increases that wherein the OFDM code element is repeated and finally obtains is selectively reversed; The example of repetition that is used to make up this OFDM code element is to obtain the device of compound OFDM code element; And the device that is used for compound OFDM code element is carried out transform operation.
24. the equipment of claim 23 comprises the device that is used for the sequence of conversion is carried out the complex arithmetic division.
25. the equipment of claim 24, wherein the sequence of conversion quilt is divided by channel guess value.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57304504P | 2004-05-21 | 2004-05-21 | |
| US60/573,045 | 2004-05-21 | ||
| US60/612,753 | 2004-09-24 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1965492A true CN1965492A (en) | 2007-05-16 |
| CN100590986C CN100590986C (en) | 2010-02-17 |
Family
ID=38083546
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN200580016150A Expired - Fee Related CN100590986C (en) | 2004-05-21 | 2005-05-20 | OFDM signal transmitting and receiving method, a transmitter and a receiver employing the method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100590986C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104718717A (en) * | 2012-10-15 | 2015-06-17 | 高通股份有限公司 | Support for signaling over flexible bandwidth carrier |
-
2005
- 2005-05-20 CN CN200580016150A patent/CN100590986C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104718717A (en) * | 2012-10-15 | 2015-06-17 | 高通股份有限公司 | Support for signaling over flexible bandwidth carrier |
| CN104718717B (en) * | 2012-10-15 | 2016-09-14 | 高通股份有限公司 | Support to the signaling on flexible bandwidth carrier wave |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100590986C (en) | 2010-02-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102318206B (en) | Low power ultra wideband transmitter and receiver | |
| JP5211057B2 (en) | UPLINK LINK SIGNAL TRANSMISSION METHOD, TRANSMISSION DEVICE, GENERATION METHOD, AND GENERATION DEVICE IN COMMUNICATION SYSTEM | |
| EP1754313B1 (en) | A transmitter and receiver for ultra-wideband ofdm signals employing a low-complexity cdma layer for bandwidth expansion | |
| US7675960B2 (en) | Method for generating communication signal sequences having desirable correlation properties and system for using same | |
| US20110080936A1 (en) | Orthogonal spread-spectrum waveform generation with non-contiguous spectral occupancy for use in cdma communications | |
| US20070041348A1 (en) | Transmitting/receiving apparatus and method for cell search in a broadband wireless communications system | |
| US10277438B2 (en) | Method and apparatus for communicating data in a digital chaos communication system | |
| EP2195940A1 (en) | Frequency hopping pattern and method for transmitting uplink signals using the same | |
| CN109246041B (en) | R-CSK double-rate composite telegraph text signal broadcasting control method | |
| CN102215047B (en) | Soft spread spectrum multiplexing method for high-speed data transmission | |
| WO2019046824A1 (en) | High-order psk signaling (hops) techniques for low-power spread spectrum communications | |
| Nassar et al. | Direct sequence spreading UWB systems: Frequency domain processing for enhanced performance and throughput | |
| JP4644988B2 (en) | Wireless impulse transmitter, receiver and method | |
| WO2006039489A2 (en) | System and method for ultra wideband communications using multiple code words | |
| Sadough | A tutorial on ultra wideband modulation and detection schemes | |
| JP3621644B2 (en) | Spread spectrum multiple access coding | |
| CN100590986C (en) | OFDM signal transmitting and receiving method, a transmitter and a receiver employing the method | |
| US20020009124A1 (en) | Large area wireless CDMA system and method | |
| KR20080110790A (en) | Non-data-aided channel estimators for multipath and multiple antenna wireless systems | |
| Addad et al. | Suitable spreading sequences for asynchronous MC-CDMA systems | |
| JPH07107007A (en) | Spreading code generation system | |
| US20160301551A1 (en) | Radio Frame for Communicating Data in a Digital Chaos Communication System | |
| JP2002325071A (en) | Transmitter, receiver, transmitting method and receiving method | |
| Kakade | Implementation of DS-CDMA Transmitter and Receiver in VHDL for FPGA | |
| KR20060120331A (en) | Apparatus and method for ultra wideband communication |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| ASS | Succession or assignment of patent right |
Owner name: NXP CO., LTD. Free format text: FORMER OWNER: KONINKLIJKE PHILIPS ELECTRONICS N.V. Effective date: 20070824 |
|
| C41 | Transfer of patent application or patent right or utility model | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20070824 Address after: Holland Ian Deho Finn Applicant after: Koninkl Philips Electronics NV Address before: Holland Ian Deho Finn Applicant before: Koninklijke Philips Electronics N.V. |
|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20100217 Termination date: 20200520 |