CN100536382C - MC-CDMA system transmitting and receiving method - Google Patents

Abstract

The present invention relates to a transmitting and receiving method of an MC-CDMA system, which comprises transmitting steps and receiving steps. In the transmitting steps, a data stream of a subscriber through BPSK demodulation is replicated to form a parallel data stream which is identical with a P-path; the P-path parallel data stream after reproduction is carried out with frequency domain spread spectrum so as to take the period of transmitting signals as the integral multiple of a chip period; P-path parallel signals after the frequency domain spread spectrum are carried out with inverse fast Fourier transform; P-path sub-carrier signals after modulation are added up and transmitted. In the receiving steps, signals received by an antenna are carried out with fast Fourier transform to recover the signals of each sub-carrier; the signals of each subscriber, each sub-carrier and each path are treated with dispreading and matched filtering to obtain the signals after the dispreading; multipath signals are carried out with time domain combination to obtain the signals after the multipath combination of each sub-carrier; the signals after the multipath combination are carried out with frequency domain combination to obtain a final decision variable of the signals of the subscriber; the final decision variable is carried out with the BPSK demodulation to recover the data stream of the subscriber.

Description

A kind of MC-CDMA system's emission and method of reseptance

Technical field

The invention belongs to mobile communication system and adopt multicarrier (MC) technology and code division multiple access (CDMA) technical field.

Background technology

CDMA is a kind of topmost technology in 3G, and multi-carrier modulation will be the key technology of following wideband wireless transmission system.Merge CDMA technology with multi-transceiver technology, constituting multi-carrier CDMA system is one of important directions of future mobile communications development.The scheme that multi-transceiver technology combines with CDMA technology mainly contains CDMA multiple carrier (MC-CDMA), multi-carrier direct sequence spectrum CDMA (MC-DS-CDMA) and three kinds of principal mode [R.Prasad of multitone modulation CDMA (MT-CDMA), S.HARA.An Overview ofMulti-carrier CDMA.IEEE Commun.Magazine, 1997,35 (12): 126-133].The MC-CDMA scheme adopts the frequency domain spread spectrum technology, and MC-DS-CDMA and MT-CDMA scheme adopt the time domain spread spectrum.Wherein, the MC-CDMA scheme is owing to can obtain frequency diversity gain and good performance is considered in three kinds of schemes the scheme of tool prospect, and the many concrete forms of future mobile communication system will be based on the MC-CDMA scheme constructs.

Traditional MC-CDMA scheme requires each subcarrier experience frequency non-selective fading channel, for the symbol period that guarantees this condition transmission signals and the general cycle of cutting of frequency expansion sequence all will be subjected to certain restriction, otherwise the condition of each subcarrier experience frequency non-selective fading may be destroyed, will cause the mis-behave of system.When the symbol period of transmission does not satisfy this condition of frequency non-selective fading channel, for guaranteeing that each subcarrier still experiences the frequency non-selective fading, traditional MC-CDMA scheme adopts the data flow after will modulating to carry out the method for 1:P serial to parallel conversion, makes the symbol period increase P of transmission guarantee that doubly each subcarrier still experiences the frequency non-selective fading.But increase serial to parallel conversion link will make the sub-carrier number of system increase P doubly, this will increase the frequency resource expense of system greatly, simultaneously because sub-carrier number has increased P doubly, also will increase the complexity of transceiver itself and the complexity of processing greatly, and in practice because channel is dynamic change, this just needs the variation of dynamic adjustments P with adaptive channel, implements very difficultly, is unfavorable for the high-speed radio transmission of data.

Summary of the invention

The present invention is the limitation that overcomes traditional MC-CDMA scheme, has proposed a kind of improved MC-CDMA system's emission and method of reseptance.

This launching technique need not to change the basic structure of traditional MC-CDMA scheme emission, but the symbol period that need get emission is an integral multiple of cutting the general cycle, and this is a key point of the present invention.Traditional MC-CDMA scheme, also can't be separated multipath signal even there is the multipath transmission because the symbol period of emission is identical with the Qie Pu cycle, therefore need limit cutting general cycle and symbol period.The present invention is owing to the symbol period of getting emission is an integral multiple of cutting the general cycle, like this, when subcarrier experience frequency selective fading channels, can guarantee effective separation at receiving terminal to the subcarrier multipath signal, fundamentally eliminate traditional MC-CDMA scheme to cutting the restriction of general cycle and symbol period, very helped the high-speed radio transmission of data.Simultaneously, the present invention is owing to need not to change the basic structure of traditional MC-CDMA scheme emission, and not needing increases the serial to parallel conversion link, has saved valuable frequency resource, has reduced the complexity of transceiver itself and the complexity of processing.

This method of reseptance adopts the RAKE reception technique to merge to the multipath signal of each subcarrier, makes traditional MC-CDMA scheme obtain the time domain diversity gain again on the basis of frequency diversity gain, has improved the overall performance of traditional MC-CDMA scheme significantly.

A kind of MC-CDMA system's emission of the present invention and reception technique scheme may further comprise the steps:

A. step of transmitting:

(1) duplicating of the data flow process 1:P of each user's process BPSK modulation forms the identical parallel data stream in P road;

(2) be that the spreading code of P carries out frequency domain spread spectrum to the P channel parallel data after duplicating stream with length, frequency domain spread spectrum cut integral multiple/one that the general cycle takes the family modulation signal cycle, promptly Fa She symbol period is an integral multiple of cutting the general cycle, and different users adopts different spreading codes;

(3) the P road parallel signal behind the frequency domain spread spectrum is carried out fast fourier inverse transformation (IFFT), each road signal is modulated on the corresponding subcarrier;

(4) launch after the P way carrier signal addition after will modulating.

B. receiving step:

(1) signal that receives of antenna comprises the stack of each user's signal and noise, and the signal that antenna is received carries out the fast fourier transform (FFT) corresponding with transmitting terminal fast fourier inverse transformation (IFFT), recovers each subcarrier signals;

(2) after each subcarrier has experienced the frequency selectivity multidiameter fading channel, each subcarrier all comprises L footpath signal again, signal to each footpath of each subcarrier of each user all carries out despreading corresponding with transmitting terminal and matched filter processing, obtains each footpath signal after despreading of each subcarrier of each user;

(3) time domain that each footpath signal after despreading of each subcarrier of each user is carried out multipath signal merges, and obtains the signal after each subcarrier multipath of each user merges;

(4) signal after each subcarrier multipath time domain merging of same user is carried out frequency domain again and merge, obtain the conclusive judgement variable of subscriber signal;

(5) the conclusive judgement variable is carried out the BPSK demodulation, recover user's data stream.

Below the related content of the inventive method is discussed.

1. transmit

Consideration has the emission process of K user's MC-CDMA system.Each user adopts the BPSK modulation, has identical transmitting power S and data rate 1/T _s, the symbol period of emission is T _sTo traditional MC-CDMA system, the symbol period of emission equals the general period T of cutting of spreading code _cBut to method of the present invention, the symbol period of getting emission is the integral multiple of cutting the general cycle, i.e. T _s=NT _c, N is one greater than 1 integer.

Then transmitting of user k can be expressed as:

$s_k\left(t\right)=\sqrt{S}\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{a}_k\left(t\right)c_{k,p}\left(t\right)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051008692500111.png,C20051008692500121.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{p}t\right)$ [formula 1]

In the formula, $a_k\left(t\right)={\mathrm{\&Sigma;}}_{n=-\&infin;}^{\&infin;}{a}_k^{\left(n\right)}{g}_{T_s}(t-n{T}_s)$ Represent user k and duplicate arbitrary road, back signal, wherein, a _k ⁽ⁿ⁾Represent user k and duplicate n the data bit in arbitrary road, back.c _k(t)=[c _{K, 1}(t) ... c _{K, P}(t)] be k user's frequency expansion sequence waveform, c _{K, p}With $c_{k,p}\left(t\right)=c_{k,p}{g}_{T_c}(t-p{T}_c)$ Represent corresponding spreading code and Qie Pu waveform respectively, T _cFor cutting the general cycle.

With

Be respectively be defined in [0, T _s) and [0, T _c) on the rectangular pulse shaping function.f _pIt is the carrier frequency of p subcarrier.

2. channel

The present invention allows each subcarrier to experience the frequency selectivity multidiameter fading channel.The low-pass impulse response of p sub-carrier channels of k user can be expressed as:

$h_{k,p}\left(t\right)=\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{k,l}{e}^{j{\mathrm{\&beta;}}_{k,l}}\mathrm{\&delta;}(t-t_{k,l})$ [formula 2]

Wherein, L is the distinguishable multipath number of channel, Be complex channel coefficient, α _{K, l}Be the amplitude gain in path, β _{K, l}Be the phase gain in path, t _{K, l}Be multidiameter delay, to different k, l supposes that it is independent identically distributed stochastic variable.

3. received signal

After having experienced the described channel of formula (2), the signal indication that receiving terminal receives is:

$r\left(t\right)=\sqrt{S}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{a}_k(t-t_{k,l}-{\mathrm{\&tau;}}_k)c_{k,p}(t-t_{k,l}-{\mathrm{\&tau;}}_k)$

[formula 3]

$\&CenterDot;{\mathrm{\&alpha;}}_{k,l}\exp \left[j(2\mathrm{\&pi;}{f}_{p}t+{\mathrm{\&theta;}}_{k,p,l})\right]+\mathrm{\&eta;}\left(t\right)$

Wherein, τ _kBe the propagation delay of user k, the k to different supposes τ _kBe independently.θ _{K, p, l}=(β _{K, l}-2 π f _pt _{K, l}-2 π f _pτ _k) mod2 π is the phase shift that p subcarrier l of user k directly goes up signal, η (t) represents additive white Gaussian noise.

4. the demodulation of signal

Be without loss of generality, suppose that user k is a desired user, makes τ _k=0.To above-mentioned receiving course, the despreading and the matched filtering of n the symbol of p subcarrier l footpath signal of desired user k are output as:

$y_{k,p,l}^{\left(n\right)}=\frac{1}{T_s}{\&Integral;}_{n{T}_s+t_{k,l}}^{(n+1)T_s+t_{k,l}}r\left(t\right)\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051008692500111.png,C20051008692500121.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{p}t)c_{k,p}(t-t_{k,l})\mathrm{dt}$ [formula 4]

Use γ _{K, p, l} ⁽ⁿ⁾The multipath merge coefficient of p subcarrier l footpath of expression user k signal is to Merge Scenarios of the present invention, a _k ⁽ⁿ⁾The conclusive judgement variable be:

$Y_k^{\left(n\right)}=\mathrm{Re}\left(\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{y}_{k,p,l}^{\left(n\right)}{\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}\right)$ [formula 5]

High specific to multipath signal merges, the multipath merge coefficient γ of p subcarrier l footpath of user k signal _{K, p, l} ⁽ⁿ⁾For:

${\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}={\mathrm{\&alpha;}}_{k,l}\exp (-j{\mathrm{\&theta;}}_{k,p,l})$ [formula 6]

Resulting conclusive judgement variable is carried out promptly obtaining after the BPSK demodulation information data of desired user k.

Beneficial effect of the present invention:

MC-CDMA scheme proposed by the invention is compared with traditional MC-CDMA scheme, because getting the symbol period of emission is the integral multiple of cutting the general cycle, so just allow each subcarrier experience frequency selectivity multidiameter fading channel, thereby fundamentally eliminated traditional MC-CDMA system to cutting the inherence restriction of general cycle and symbol period, very helped the realization of high speed wireless data transmission; Simultaneously, because the symbol period of getting emission is an integral multiple of cutting the general cycle, can guarantee effective separation to multipath signal at receiving terminal, realization merges the time domain of subcarrier multipath signal, compare with traditional scheme, also obtained the rake gain, improved the performance of system significantly; Secondly, owing to do not need the serial to parallel conversion link, still experience the frequency non-selective fading with traditional scheme for each subcarrier of assurance, data flow after the modulation being carried out the method for 1:P serial to parallel conversion compares, the sub-carrier number of system has reduced P doubly, very help the frequency resource of saves valuable, also help reducing simultaneously the complexity of transceiver itself and the complexity of processing.Therefore, the many concrete forms of future mobile communication system will be than more favourable based on traditional MC-CDMA scheme constructs based on the solution of the present invention structure.

Description of drawings

Fig. 1 is the emission process figure of the arbitrary user k of MC-CDMA system;

Fig. 2 is the receiving course figure of the arbitrary user k of MC-CDMA system;

Fig. 3 is that error rate BER is to E _s/ N ₀Relation curve (P=32, N=16, K=8);

Fig. 4 is relation curve (P=32, N=16, the E of error rate BER to number of users _s/ N ₀=10dB);

Fig. 5 is that the bandwidth efficiency of system is to E _s/ N ₀Relation curve (P=32, N=16, K=8).

Embodiment

Below in conjunction with accompanying drawing method of the present invention is described in detail.

With reference to the emission process of a kind of MC-CDMA arbitrary user k of system of Fig. 1, concrete steps comprise:

(1) binary signal of information source 11 generations of arbitrary user k, through BPSK modulation 12, the data flow of generation duplicates 13 through 1:P's, forms the identical parallel data stream in P road, $a_k\left(t\right)={\mathrm{\&Sigma;}}_{n=-\&infin;}^{\&infin;}{a}_k^{\left(n\right)}{g}_{T_s}(t-n{T}_s)$ Represent user k and duplicate arbitrary road, back signal, wherein, a _k ⁽ⁿ⁾Represent user k and duplicate n the data bit in arbitrary road, back, symbol period is T _s

(2) P channel parallel data stream is the frequency domain spread spectrum 14 of the spreading code of P through length, obtains the signal of user k correspondence behind the p spread spectrum of arbitrary road and is:

a _k(t)c _k，p(t)

Wherein, c _{K, p}(t) expression spreading code c _{K, p}Cut general waveform, cutting the general cycle is T _c, the symbol period of getting emission is the integral multiple of cutting the general cycle, i.e. T _s=NT _c, N is one greater than 1 integer;

(3) the P road parallel signal behind the frequency domain spread spectrum is modulated to each road signal on the corresponding subcarrier through fast fourier inverse transformation (IFFT) 15, and the signal that obtains on the user k modulation arbitrary subcarrier p in back is:

$\sqrt{S}{a}_k\left(t\right)c_{k,p}\left(t\right)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051008692500111.png,C20051008692500121.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{p}t\right)$

Wherein, S is a user emission power, f _pIt is the carrier frequency of p subcarrier;

(4) P road, modulation back subcarrier signals is through addition 16 back emissions, and the signal indication of user k emission is:

$s_k\left(t\right)=\sqrt{S}\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{a}_k\left(t\right)c_{k,p}\left(t\right)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051008692500111.png,C20051008692500121.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{p}t\right)$

With reference to the receiving course of the arbitrary user k of MC-CDMA system of Fig. 2, concrete steps comprise:

(1) signal that receives of antenna comprises the stack of each user's signal and noise, signal process and the corresponding fast fourier transform of transmitting terminal fast fourier inverse transformation (IFFT) (FFF) 21 that antenna receives, recover the signal on each subcarrier, the signal on the arbitrary subcarrier p that is recovered is:

r(t)exp(-j2πf _pt)

Wherein, r (t) is the received signal on the antenna;

(2) after each subcarrier has experienced the frequency selectivity multidiameter fading channel, each subcarrier all comprises L footpath signal again, each footpath signal of each each subcarrier of user all passes through despreading corresponding with transmitting terminal and matched filter processing 22, obtain each footpath signal after despreading of each subcarrier of each user, the signal of n bit is after despreading on the arbitrary footpath l of the arbitrary subcarrier p of user k and the matched filter processing:

$y_{k,p,l}^{\left(n\right)}=\frac{1}{T_s}{\&Integral;}_{n{T}_s+t_{k,l}}^{(n+1)T_s+t_{k,l}}r\left(t\right)\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20051008692500111.png,C20051008692500121.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{p}t)c_{k,p}(t-t_{k,l})\mathrm{dt}$

Wherein, t _{K, l}It is the time delay of the arbitrary footpath l of user k;

(3) signal after each the footpath despreading of each subcarrier of each user is carried out the multipath signal time domain and merge 23, obtain the signal after each subcarrier multipath of each user merges, the signal that time domain merges the arbitrary subcarrier p of back user k n bit is:

$\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{y}_{k,p,l}^{\left(n\right)}{\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}$

Wherein, L is the distinguishable multipath number of channel, γ _{K, p, l} ⁽ⁿ⁾The multipath merge coefficient of p subcarrier l footpath of expression user k signal;

(4) signal after each subcarrier multipath time domain merging of same user is carried out frequency domain again and merge 24, obtain the conclusive judgement variable of subscriber signal, the conclusive judgement variable of user k n bit is:

$\mathrm{Re}\left(\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{y}_{k,p,l}^{\left(n\right)}{\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}\right)$

(5) the conclusive judgement variable to subscriber signal carries out BPSK demodulation 25, recovers users'data signals, promptly obtains user's the stay of two nights 26.

For estimating MC-CDMA scheme proposed by the invention, its BER performance and bandwidth efficiency have been carried out Computer Simulation, and also the performance that result and traditional MC-CDMA scheme carrier wave are merged when adopting high specific to merge (MRC) and equal gain combining (EGC) respectively compares.In order to compare, adopted the BPSK modulation, system has identical bandwidth and data rate, and multipath power is assumed to be even distribution.Spreading code has adopted the Walsh-Hadamard sign indicating number, and the define symbol energy is E _s=PST _s, error rate thresholding is 10 ^-3

The time domain that Fig. 3 has provided multipath signal merges when adopting high specific to merge (MRC) and equal gain combining (EGC) respectively, and the BER performance of MC-CDMA scheme of the present invention and traditional MC-CDMA scheme is to E _s/ N ₀Computer artificial result.As can be seen from Figure 3, the solution of the present invention is owing to obtained the rake gain, and the BER performance of comparing system with former scheme is significantly improved, and along with the increase of multipath number, the improvement of BER performance is also all the more remarkable.

The time domain that Fig. 4 has provided multipath signal merges and to adopt high specific to merge respectively and during equal gain combining, and the BER performance of MC-CDMA scheme of the present invention and traditional MC-CDMA scheme is to the computer artificial result of number of users.Merge the increase of number as can be seen from Figure 4 along with multipath, the BER performance of system significantly improves, and makes under the condition of the same error rate, and the number of users that system holds is significantly improved.

Fig. 5 is for working as the multipath number not simultaneously, and the bandwidth efficiency of system is to E _s/ N ₀The Computer Simulation relation curve.The multipath number has remarkable influence to the bandwidth efficiency of system as can be seen from Figure 5, and promptly because rake gains, the present invention program's bandwidth efficiency or power system capacity are compared with traditional scheme and obtained significant raising.

From Fig. 3,4 and 5, it can also be seen that the BER performance and the bandwidth efficiency of system when the BER performance of system and bandwidth efficiency will obviously be better than adopting equal gain combining when the time domain of multipath signal merged the merging of employing high specific.Therefore, the merging of multipath signal time domain adopts the mode of high specific merging more suitable.

Claims (2)

1. a frequency domain spread spectrum MC-CDMA MC-CDMA system launches and method of reseptance, it is characterized in that emission and the receiving course of arbitrary user k, may further comprise the steps:

A. step of transmitting:

(1) binary signal of the information source of arbitrary user k (11) generation, through BPSK modulation (12), the data flow of generation forms the identical parallel data stream in P road through duplicate (13) of 1:P, $a_k\left(t\right)={\mathrm{\&Sigma;}}_{n=-\&infin;}^{\&infin;}{a}_k^{\left(n\right)}{g}_{T_s}(t-{\mathrm{nT}}_s)$ Expression user k duplicates arbitrary road, back signal, wherein, and a _k ⁽ⁿ⁾Expression user k duplicates n the data bit in arbitrary road, back, and symbol period is T _s

For be defined in [0, T _s) on the rectangular pulse shaping function;

(2) P channel parallel data stream is the frequency domain spread spectrum (14) of the spreading code of P through length, obtains the signal of user k correspondence behind the p spread spectrum of arbitrary road and is:

a _k(t)c _k，p(t)

Wherein, c _{K, p}(t) expression spreading code c _{K, p}Cut general waveform, cutting the general cycle is T _c, the symbol period of getting emission is the integral multiple of cutting the general cycle, i.e. T _s=NT _c, N is one greater than 1 integer;

(3) the P road parallel signal behind the frequency domain spread spectrum is modulated to each road signal on the corresponding subcarrier through fast fourier inverse transformation (15), and the signal that obtains on the user k modulation arbitrary subcarrier p in back is:

$\sqrt{S}{a}_k\left(t\right)c_{k,p}\left(t\right)\exp \left(j2\mathrm{\&pi;}{f}_{p}t\right)$

Wherein, S is a user emission power, f _pIt is the carrier frequency of p subcarrier;

(4) P road, modulation back subcarrier signals is through the emission of addition (16) back, and the signal indication of user k emission is:

$s_k\left(t\right)=\sqrt{S}\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{a}_k\left(t\right)c_{k,p}\left(t\right)\exp \left(j2\mathrm{\&pi;}{f}_{p}t\right)$

B. receiving step:

(1) signal that receives of antenna comprises the stack of each user's signal and noise, signal process and the corresponding fast fourier transform of transmitting terminal fast fourier inverse transformation (21) that antenna receives, recover the signal on each subcarrier, the signal on the arbitrary subcarrier p that is recovered is:

r(t)exp(-j2πf _pt)

Wherein, r (t) is the received signal on the antenna;

(2) after each subcarrier has experienced the frequency selectivity multidiameter fading channel, each subcarrier all comprises L footpath signal again, each footpath signal of each each subcarrier of user all passes through despreading corresponding with transmitting terminal and matched filter processing (22), obtain each footpath signal after despreading of each subcarrier of each user, the signal of n bit is after despreading on the arbitrary footpath l of the arbitrary subcarrier p of user k and the matched filter processing:

$y_{k,p,l}^{\left(n\right)}=\frac{1}{T_s}{\&Integral;}_{{\mathrm{nT}}_s+t_{k,l}}^{(n+1)T_s+l_{k,l}}r\left(t\right)\exp (-j2\mathrm{\&pi;}{f}_{p}t)c_{k,p}(t-t_{k,l})\mathrm{dt}$

Wherein, t _{K, l}It is the time delay of the arbitrary footpath l of user k;

(3) signal after each the footpath despreading of each subcarrier of each user is carried out the multipath signal time domain and merge (23), obtain the signal after each subcarrier multipath of each user merges, the signal that time domain merges the arbitrary subcarrier p of back user k n bit is:

$\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{y}_{k,p,l}^{\left(n\right)}{\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}$

Wherein, L is the distinguishable multipath number of channel, and promptly each subcarrier all comprises L footpath signal, γ again _{K, p, l} ⁽ⁿ⁾The multipath merge coefficient of p subcarrier l footpath of expression user k signal;

(4) signal after each subcarrier multipath time domain merging of same user is carried out frequency domain again and merge (24), obtain the conclusive judgement variable of subscriber signal, the conclusive judgement variable of user k n bit is:

$\mathrm{Re}\left(\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{y}_{k,p,l}^{\left(n\right)}{\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}\right)$

(5) the conclusive judgement variable to subscriber signal carries out BPSK demodulation (25), recovers users'data signals, promptly obtains user's the stay of two nights (26).

2. according to described a kind of MC-CDMA system's emission of claim 1 and method of reseptance, it is characterized in that claim 1 receiving step (3) merges the merging of employing high specific to the time domain of the arbitrary subcarrier p of user k multipath signal, the merge coefficient γ of p subcarrier l footpath of user k signal _{K, p, l} ⁽ⁿ⁾For:

${\mathrm{\&gamma;}}_{k,p,l}^{\left(n\right)}={\mathrm{\&alpha;}}_{k,l}\exp (-j{\mathrm{\&theta;}}_{k,p,l})$

a _{K, l}It is the amplitude gain of p subcarrier l footpath of user k signal;

θ _{K, p, l}Phase shift for p subcarrier l footpath of user k signal.

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