CN1992699A - OFDM system of broad band backward compatibility and method thereof - Google Patents
OFDM system of broad band backward compatibility and method thereof Download PDFInfo
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- CN1992699A CN1992699A CN 200510137401 CN200510137401A CN1992699A CN 1992699 A CN1992699 A CN 1992699A CN 200510137401 CN200510137401 CN 200510137401 CN 200510137401 A CN200510137401 A CN 200510137401A CN 1992699 A CN1992699 A CN 1992699A
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Abstract
The invention provides a broadband OFDM system compatible with narrow-band OFDM system signals, including: base station receiver, for receiving uplink signals, and in which the base station receiver includes the first module to support broadband terminal signal transmission, and the second module to support narrowband and broadband terminal signal transmission; base station transmitters, for launching downlink signals. Compared with traditional technology, the system and the method of the invention has less processing complexity, faster computing speed, and more simple and better engineering implementation.
Description
Technical field
The present invention relates to belong to the field of ofdm communication system, particularly, relate to a kind of and wideband OFDM (OFDM) system arrowband ofdm system backward compatibility.
Background technology
IEEE 802.16d/e standard has been adopted the OFDM technology, has also advised corresponding utilized bandwidth and frequency.Yet IEEE 802.16d/e standard does not provide method, solving the overlap backward compatibility issues of scalable ofdm system of single frequency network (SFN) frequency, promptly following new, more how the ofdm system of wide bandwidth supports OFDM terminal existing, relative arrowband.
Summary of the invention
Therefore, the object of the invention is, at the single frequency network frequency scalable ofdm system that overlaps, designs a kind of new broadband (is 40MHz such as bandwidth) ofdm system, can existing arrowband of backward compatibility (is 20MHz such as bandwidth) ofdm system terminal.The frequency spectrum of this arrowband and broadband system has part overlapping (Frequency overlay).
The present invention proposes the wideband OFDM system of a kind of compatible arrowband ofdm system signal, comprising:
Base station receiver is used to receive upward signal, and wherein base station receiver comprises first module of supporting the transmission of wide-band terminal signal and supports narrowband terminal and second module of wide-band terminal signal transmission;
Base station transmitter is used for the transmitting downstream signal.
According to another aspect of the present invention, propose a kind of method that is used to make wideband OFDM system and arrowband ofdm system backward compatibility, comprised step:
The upward signal that receives is detected processing respectively;
If the base station only receives the wide-band terminal signal, adopt first method of reseptance to handle;
If the base station receives the signal of narrowband terminal and wide-band terminal simultaneously, adopt second method of reseptance to handle and carry out.
Compare with conventional art, system and method for the present invention has lower processing complexity, and computational speed is faster, and simpler, easier Project Realization.
Description of drawings
Fig. 1 shows the overlap spectrum allocation may of scalable ofdm system of frequency according to the present invention.
Fig. 2 shows the overlap transmitter architecture of scalable ofdm system base station (descending) of wideband frequency according to the present invention.
Fig. 3 shows the overlap receiver structure of scalable ofdm system base station (up) of wideband frequency according to the present invention.
Fig. 4 shows frequency and overlaps the performance of three methods of scalable ofdm system when using BPSK relatively.
Fig. 5 shows frequency and overlaps the performance of three methods of scalable ofdm system when using QPSK relatively.
Embodiment
The present invention solves the problem of following two aspects:
(1) backward compatibility of descending (downlink): the IFFF size of 40MHz broadband system base station (WB-BS) transmitter is the twice of 20MHz narrowband systems terminal, and 20MHz narrowband terminal (NB-MT) and 40MHz wide-band terminal (WB-MT) still can correctly receive the corresponding signal that WB-BS sends with reception structure separately (noiseless).
(2) backward compatibility of up (uplink): the IFFF size of WB-BS receiver also is the twice of NB-MT, and WB-BS can correctly receive the corresponding signal that NB-MT and WB-MT (still using emitting structural separately) send (noiseless).
The present invention is directed to the single frequency network frequency scalable ofdm system that overlaps, the bandwidth of supposing existing arrowband ofdm system is 20MHz, and our bandwidth of wideband OFDM system design, new is 40MHz.Be illustrated in figure 1 as its spectrum allocation may situation.In the drawings, LFD is meant the bandwidth of low-frequency range, i.e. [f
0, f
0+ 20M] low-frequency range 20MHz bandwidth.HFD is meant the bandwidth of high band, i.e. [f
0+ 20M, f
0+ 40M] high band 20MHz bandwidth.We consider that existing arrowband ofdm system only takies LFD 20MHz bandwidth, and scalable ofdm system takies [f and new wideband frequency overlaps
0, f
0+ 40M] bandwidth, this figure has illustrated the overlapping situation of portions of the spectrum of two kinds of (arrowband, broadband) systems.
The present invention has following hypothesis:
(1) FFT of WB-BS size is 2N.The FFT size of NB-MT is N.
(2) the sampling clock Ts of NB-MT
20With the sampling clock Ts of WB-BS spaced-apart alignment accurately, and Ts
20=2Ts.
(3) NB-MT is merely able to use the wideband frequency low-frequency range 20MHz bandwidth (20MHz LFD) of scalable ofdm system that overlaps, and the 20MHz bandwidth (20MHzHFD) of high band is only used for WB-MT.
Fig. 2 has provided the transmitter architecture figure of a kind of 40MHz SOFO BS of system.Fig. 3 has provided the receiver structure figure of a kind of 40MHz SOFO BS of system.In Fig. 2 and Fig. 3, G40 (f) is the frequency response of 40MHz bandwidth transceiving filter; G20 (f) is the frequency response of low-frequency range (LFD) 20MHz bandwidth transceiving filter; G20h (f) is the frequency response of high band (HFD) 20MHz bandwidth transceiving filter; D/A and A/D are the transducers between digital signal and the analog signal; RF is the radio-frequency front-end processing unit; Fs and 2Fs represent that respectively sampling rate is Fs and 2Fs; IFFT (2N points)/FFT (2N points) expression 2N point IFFT/FFT.
As shown in Figure 3, three main modular according to the present invention are respectively " Inserting ' 0 ' " module, " ∑ " module and " Interference Cancellation " module, and its function is as follows respectively:
" Inserting ' 0 ' " module is to insert " 0 " signal in each sampled point (sampling rate is Fs) back, makes that original length is that the former sample sequence lengthening of N is the long sequence of 2N for length.This long sequence is identical with former sample sequence at the signal of even bit, and is " 0 " at the signal of odd bits.Annotate: the original position in the sequence is since 0 number consecutively, is that the former sample sequence of N is an example with length, and its Position Number then is successively: 0,1 ..., N-1.
Suing for peace of the sequence that it is 2N that " ∑ " module is finished two length by sampled point.In actual use, " Inserting ' 0 ' " and " ∑ " two modules also can co-operation, the signal that is about to length from LFD and is the former sample sequence of N and length from HFD and be even number position on the former sample sequence of 2N carries out addition, can reduce functional module like this and simplifies and handle computing.
" Interference Cancellation " module is exactly after through 2N point IFFT, HFD is gone up signal on N the subcarrier deduct on the LFD signal on N the subcarrier, just obtains corresponding received signal on the HFD.
Shown in Fig. 2 and 3, when only WB-MT being arranged among the WB-BS (Cell), it receives and adopts module 1 (first handles) to receive processing, can support WB-MT.Such reception structure has high spectrum efficiency.
When among the WB-BS (Cell) NB-MT and WB-MT being arranged, it receives and adopts module 2 (second handles) to receive processing, can support NB-MT and WB-MT.Such reception structure can be supported the terminal NB-MT and the WB-MT of two kinds of different bandwidths simultaneously.Thereby realized that wideband frequency overlaps scalable ofdm system to having the backward compatibility of narrowband terminal.
Carry out Computer Simulation by " inserting 0 " method (i.e. " inserting 0 method ") that the present invention is proposed, analyze the performance difference that has contrasted with conventional method (i.e. " traditional method "), interpolation method (i.e. " interpolation method ").
When adopting BPSK, QPSK modulation system, by the bit error rate performance behind awgn channel and the quasistatic Rayleigh channel.Supposed N=4, interpolation method uses the sinc function.Here, interpolation method is exactly directly the mixed signal of NB-MT that receives and WB-MT to be carried out the 2Fs sampling and carried out 2N point FFT demodulation.
In Fig. 4 and Fig. 5, provided the simulation performance of the up link of above-mentioned three kinds of methods respectively.Wherein Fig. 4 is corresponding to combining with BPSK, and Fig. 5 is corresponding to combining with QPSK.Number in the figure be 1 line corresponding respectively the performance the awgn channel under, label is 2 line correspondence quasistatic Rayleigh channel is down and adopt the performance of ideal communication channel estimation (ideal channelestimation).SNR conventional letter noise power ratio, BER represents bit error rate.
Result's demonstration, identical according to the performance of " inserting 0 " method of the present invention and conventional method, and the interpolation method performance is the poorest, and also it improves with the enhancing of signal power hardly.Compare with conventional method, " inserting 0 " method that the present invention carried has lower processing complexity, and computational speed is faster, and simpler, the easier Project Realization of method.
Compare with conventional method, the present invention has increased the three functions module, and they are all very simple and be easy to realize, and the present invention has reduced a N point FFT module and calculating, therefore overall complexity obviously reduces, and each FFT demodulation approximately can reduce Nlog2N complex multiplication operation and Nlog2N-2N complex addition computing. Such as: when N=1K (1024), Can save the inferior complex addition fortune of the inferior complex multiplication operation of 10K (10240) and 8K (8192) Calculate. Therefore, it is a kind of effective method that the present invention adopts " inserting 0 " method, can be successfully Realize the backward compatibility of the folded scalable ofdm system of SFN (SFN) frequency friendship, and Complexity is littler, is easy to Project Realization.
Claims (13)
1. the wideband OFDM system of a compatible arrowband ofdm system signal comprises:
Base station receiver is used to receive upward signal, and wherein base station receiver comprises first module of supporting the transmission of wide-band terminal signal and supports narrowband terminal and second module of wide-band terminal signal transmission;
Base station transmitter is used for the transmitting downstream signal.
2. by the described system of claim 1, it is characterized in that when the base station only received the signal of wide-band terminal, described base station receiver adopted first module to detect the wide-band terminal signal; When the base station received the signal of narrowband terminal and wide-band terminal simultaneously, described base station receiver adopted second module that the front end terminal and the low-frequency range terminal signaling of terminal arrowband are detected processing, and wherein the signal to low-frequency range carries out zero insertion.
3. by claim 1 or 2 described systems, it is characterized in that described second module comprises:
The narrow band filter module is used for leaching narrow band signal from broadband signal;
The A/D modular converter is used for upward signal is carried out the A/D conversion;
The zero insertion module is used for the numerical data of low-frequency range is carried out zero insertion;
Summation module is used for suing for peace by sampled point to Serial No.;
Fourier transform module is used for Fourier transform is carried out in the output of summation module;
The Interference Cancellation module is used to calculate the received signal of high band.
4. by the described system of claim 3, it is characterized in that described zero insertion module is inserted " 0 " signal after each sampled point, to obtain the long sequence that length is two times of the length of former sample sequence.
5. by the described system of claim 4, it is characterized in that described long sequence is identical with former sample sequence at the signal of even bit, and be " 0 " at the signal of odd bits.
6. by claim 3 or 4 described systems, it is characterized in that described summation module is sued for peace to the numerical data of described long sequence and high band.
7. by the described system of claim 3, it is characterized in that described Interference Cancellation module obtains the received signal of high band by the signal on the subcarrier on the high band being deducted the signal on the subcarrier on the low-frequency range.
8. method that is used to make wideband OFDM system and arrowband ofdm system backward compatibility comprises step:
The upward signal that receives is detected processing respectively;
If the base station only receives the wide-band terminal signal, adopt first method of reseptance to handle;
If the base station receives the signal of narrowband terminal and wide-band terminal simultaneously, adopt second method of reseptance to handle and carry out.
9. by the described method of claim 8, it is characterized in that described second receiving handling method comprises:
The upward signal of being received is carried out narrow-band filtering respectively to be handled;
Filtered signal is carried out the A/D conversion;
Numerical data to low-frequency range is carried out zero insertion;
To suing for peace of Serial No. by sampled point;
Fourier transform is carried out in output to summation module;
Calculate the received signal of high band.
10. by the described method of claim 9, it is characterized in that described zero insertion step comprises, insertion " 0 " signal each sampled point after is to obtain the long sequence that length is two times of the length of former sample sequence.
11. by the described method of claim 10, it is characterized in that described long sequence is identical with former sample sequence at the signal of even bit, and be " 0 " at the signal of odd bits.
12., it is characterized in that described summation module is sued for peace to the numerical data of described long sequence and high band by the described method of claim 10.
13. by the described method of claim 9, it is characterized in that,, obtain the received signal of described high band by the signal on the subcarrier on the high band being deducted the signal on the subcarrier on the low-frequency range.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510137401 CN1992699A (en) | 2005-12-30 | 2005-12-30 | OFDM system of broad band backward compatibility and method thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510137401 CN1992699A (en) | 2005-12-30 | 2005-12-30 | OFDM system of broad band backward compatibility and method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014075458A1 (en) * | 2012-11-16 | 2014-05-22 | 华为技术有限公司 | Method, terminal device, and base station for determining working narrow-band |
-
2005
- 2005-12-30 CN CN 200510137401 patent/CN1992699A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014075458A1 (en) * | 2012-11-16 | 2014-05-22 | 华为技术有限公司 | Method, terminal device, and base station for determining working narrow-band |
| CN103825670A (en) * | 2012-11-16 | 2014-05-28 | 华为技术有限公司 | Working narrowband determining method, terminal equipment and base station |
| CN103825670B (en) * | 2012-11-16 | 2018-05-18 | 华为技术有限公司 | Work narrowband determines method, terminal device and base station |
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