CN103501186B - Mutual-complementing code CDMA (Code Division Multiple Access) system of time-frequency mixing separation sub-code structure - Google Patents

Abstract

The invention relates to a mutual-complementing code CDMA (Code Division Multiple Access) system of a time-frequency mixing separation sub-code structure, relates to a mutual-complementing code CDMA system, and aims to reduce multipath interference in a sub-band of each subcarrier in a communication system. The signal transmission process comprises the following steps of replicating data of a user k into W parts, W subcarrier spread spectrum modules respectively adopting a set of corresponding sub-codes to spread the data of the user k and respectively modulating onto W subcarriers, and then superposing W subcarriers and sending the subcarriers to a wireless channel. The signal reception process comprises the following steps that a receiver respectively demodulates the data on W sub-carriers, W sub-carrier despreading modules respectively despread the signals spreaded by each sub-code on each path by using the corresponding sub-code, and decision is carried out to output after three combinations. The invention is suitable for wireless communication occasions.

Description

Time a kind of-the mutual-complementing code cdma system of frequently hybrid separation subcode structure

Technical field

The present invention relates to a kind of mutual-complementing code cdma system.

Background technology

In numerous cellular radio Communication correlation technique, multiple access technique is one of physical-layer techniques of core the most, the mode that it fundamentally determines multi-user in communication system, multichannel shares Radio Resource, and the selection of which also finally have impact on the service quality being supplied to terminal use significantly.Therefore, the development of multiple access technology indicate cell mobile communication systems by for evolution: the analog mobile communication system being adopted frequency division multiple access (FDMA) by the first generation, adopt the gsm system of time division multiple access (TDMA) to the second generation and adopt Narrowband CDMA (Code Division Multiple Access, CDMA) IS-95 system, the system of Wideband CDMA technology is extensively adopted to the third generation, then to adopting the forth generation mobile communication system of OFDM.

Although compared to frequency division, time division multiple access way, the many advantages such as CDMA has that secret and safe is high, frequency reuse is high, the interference of anti-arrowband and multipath fading, but because all cdma systems are interference-limited, when especially considering that communication system exists the problem such as multi-path jamming, asynchronous transmission.Therefore, CDMA multi-access mode is faced with the embarrassed shape of the cellular mobile communication stage that fades out gradually.

As its name suggests, the orthogonality of address code/signed codevector (SignatureCodes) that it adopts is relied on to distinguish different user/different channels compared to FDMA and TDMA, CDMA.Therefore, the selection of code fundamentally determines the performance of cdma system.The interference-limited immediate cause of cdma system is that the correlation properties of its spreading code adopted are nonideal, that is: 1) in the auto-correlation function of frequency expansion sequence except there is a peak value when zero shift, also there is less other peak in other displacements place.Under Multipath Transmission environment, these other peaks will be collected in the correlator of receiving terminal, thus cause multi-path jamming; 2) there is nonzero value in the cross-correlation function of two frequency expansion sequences.Between multipath or user under asynchronous transmission environment, the correlator of receiving end collects by these non-zero correlations, thus causes multi-access inference and near-far interference.Even if finally cause adopting a series of assistant subsystem or technology to solve these problems, the power as complexity controls, multiuser detection etc., cdma system still cannot provide competitive systematic function.

In order to the innovation accelerating code point technology returns to stage to impel it, based on the spreading code of a class novelty---the CDMA brand-new solution of future generation of mutual-complementing code (Complementary Codes, CCs) is carried out.Mutual-complementing code have employed the code design concept in conjunction with actual communication environment, the auto-correlation that can truly realize ideal and their cross correlation, thus imparts CDMA technology and break away from interference-limited ability.Can the realize ideal basic reason of correlation properties of mutual-complementing code is the structure of its many subcode, and multiple subcodes that namely each user needs employing mutual-complementing code to comprise carry out the desirable correlation properties that spread spectrum just can realize expecting.But the particularity of mutual-complementing code structure brings new problem to the design of corresponding cdma system.In order to support the spread spectrum structure based on mutual-complementing code and realize based on the relevant testing process of complementation, the CDMA(CC-CDMA based on mutual-complementing code) system demand fulfillment: be effectively separated subcode, subcode order correspondence, subcode displacement synchronous and correlation equal gain combining four conditions.So far, in order to meet above-mentioned requirements, according to the mode being separated mutual-complementing code subcode, CC-CDMA system configuration can be classified as two classes: 1) the CC-CDMA system of serial time division; 2) the CC-CDMA system of parallel frequency division.Signal after the different subcode spread spectrum of transmission of the CC-CDMA system employing different time sheet order serial of serial time division structure; its advantage can eliminate multi-path jamming completely when protecting interval to be not less than the maximum delay expansion of multipath channel, thus obtain superior multipath diversity gains.Its shortcoming is then the effective separation in order to ensure subcode in CC-CDMA system, and the communication in the CC-CDMA system of serial time division between multi-user needs to be synchronous or quasi synchronous.That is, in the scope that the relative time delay that the different user caused due to synchronous error and propagation delay arrives receiver must be determined at, the determination protecting interval is convenient to.And protect the introducing at interval to also reduce the spectrum efficiency of this system.Signal after the different subcode spread spectrum of transmission adopting different carrier to walk abreast unlike the CC-CDMA system of, parallel frequency division with it.One group of subcarrier can for not having the subcarrier of orthogonality for the subcarrier with orthogonality yet.The CC-CDMA system of parallel frequency division all can eliminate multi-access inference completely in synchronous, asynchronous communication, and then also can not there is the near-far problem in conventional CDMA system.Therefore, compared to time division scheme, the CC-CDMA system of frequency division is more subject to the welcome of researcher in recent years.But the performance of the CC-CDMA system of parallel frequency division is responsive for the frequency selective fading caused by multipath.This is because frequency selective fading experiences different decline by causing different subcode, thus causes realizing the equal gain combining in complementary related definition.Especially in uplink communication, the different carrier of various user experiences different decline, and " equal gain combining " cannot be recovered by any merging criterion at receiving terminal.Although, have the detection algorithm of some novelties to be suggested at present, improve the performance of CC-CDMA system under frequency selective fading channels of parallel frequency division.But these schemes are only applicable to frequence of exposure Selective intensity in whole bandwidth, and when the decline of each subcarrier inner flat.When also there is Selective intensity in the bandwidth of each subcarrier, when namely the coherence bandwidth of channel is less than the bandwidth of each subcarrier, these detection algorithms will be no longer applicable, and the impact being subject to multiple access and multi-path jamming is also deteriorated by corresponding CC-CDMA systematic function.

Summary of the invention

The present invention is the multi-path jamming in the subband in order to reduce each subcarrier in communication system, thus when providing a kind of-and the mutual-complementing code cdma system of hybrid separation subcode structure frequently.

Time-the mutual-complementing code cdma system of frequency hybrid separation subcode structure,

For user k, the signal emission process of transmitter:

Step one, by the data b of user k ^(k)copy W part, W is positive integer, and is emitted to W sub-frequency spectrum module respectively, described each subcarrier spread spectrum module corresponding Q subcode respectively;

Step 2, W sub-frequency spectrum module adopts one group of corresponding subcode to carry out spread spectrum to the data of user k respectively, obtains the signal after spread spectrum

The detailed process of each subcarrier spread spectrum module spread spectrum is:

First, adopt Q subcode to carry out spread spectrum respectively each data in subcarrier, Q is positive integer;

Then, the data after spread spectrum are carried out serial/parallel conversion respectively, is then stitched together in order, and intubating length is the protection interval of G chip lengths between adjacent two subcode spread-spectrum signals, G is positive integer;

Finally, spliced data obtain the output signal of this subcarrier spread spectrum module after carrying out parallel/serial conversion w=1,2 ..., W;

Step 3, by step 2 obtain spread spectrum after signal be modulated to W subcarrier f respectively ₁, f ₂..., f _won, be then sent to wireless channel by after W subcarrier superposition; The signal completing transmitter is launched;

For user g, the Signal reception process of receiver:

Step 4, subchannel independently modeling to each subcarrier, the Channel Modeling of W subcarrier is have the distinguishable footpath that identical number is L, and corresponding each footpath time delay τ ₁, τ ₂..., τ _lidentical independent identically distributed tap line delay model; Receiver is demodulation W subcarrier f respectively ₁, f ₂..., f _won data, the W an obtained baseband signal and be emitted to W subcarrier despreading module respectively, described each subcarrier despreading module corresponding Q subcode respectively;

Step 5, W subcarrier solution frequency module adopts corresponding subcode carry out despreading and merge to the signal of each the subcode spread spectrum on each footpath respectively, obtains the signal of W subcarrier despreading;

Step 6, the signal of W subcarrier despreading that step 5 obtained are with weight merge, obtain the result after merging carry out adjudicating rear output;

Complete the Signal reception of receiver.

Each data in subcarrier adopted Q subcode to carry out the method for spread spectrum in step 2 respectively all identical with the 1st subcarrier, be specially:

The signal after q subcode spread spectrum is adopted to be:

$d_{1,q}^{\left(k\right)}\left(t\right)=\sqrt{p_k}\underset{j=0}{\overset{B-1}{\mathrm{\Σ}}}{b}_j^{\left(k\right)}{C}_{1,q}^{\left(k\right)}(t-\mathrm{jN}{T}_c)$

Wherein: represent the jth data that user k sends in a data block, j ∈ 1,2 ..., x}, wherein x represents that the bit number that each subcarrier sends, N are the code length of each subcode; T _cit is the duration of a chip; B is the length of this data block; T is the time; p _kfor transmitted power, q ∈ 1,2 ..., Q}, for the frequency spreading wave corresponding to a subcarrier 1 q subcode of user k, be expressed as:

$C_{1,q}^{\left(k\right)}\left(t\right)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{c}_{q,n}^{\left(k\right)}q(t-n{T}_c+T_c)$

Wherein, (t) for chip transmission pulse waveform n ∈ 1,2 ..., N};

If q (t) is apart from shape pulse, then:

In step 5, W subcarrier solution frequency module adopts corresponding subcode to carry out despreading to the signal of each the subcode spread spectrum on each footpath and the method merged is all identical with the 1st subcarrier respectively, is specially:

Step May Day, adopt first group of delay to carry out alignment operation to the signal in each footpath, that is: postpone τ _l,gcorresponding subsequent treatment is the signal in l footpath in the propagation channel of detection user g; Adopt second group of delay to carry out alignment operation to the signal of subcode spread spectrum, that is: the subsequent treatment postponing (q-1) △ corresponding is that employing q subcode carries out despreading;

Step 5 two, carry out matched filtering and despreading for L footpath, a Q subcode respectively, to obtain on every footpath signal u after Q despreading _{l, 1}, u _{l, 2}... u _l,Q, l=1,2 ..., L;

Assuming that carrier wave, bit and chip synchronization that the signal of receiver and user g is realized ideal, for a user g jth data in l footpath by q subcode despreading detailed process be:

$u_{q,l}^{\left(g\right)}\left(j\right)={{\∫}_0^{{\mathrm{NT}}_c}r}_1(t+j{T}_b+{\mathrm{\τ}}_{l,g}+(q-1)\mathrm{\Δ})C_{1,q}^{\left(g\right)}\left(t\right)\mathrm{dt}$

Wherein, l ∈ 1,2 ..., L}, q ∈ 1,2 ..., Q}, j ∈ 1,2 ..., x}, T _b=(xN+G) Tc, △=GT _c, for the frequency spreading wave corresponding to a subcarrier 1 q subcode of user g;

Signal u after step 5 three, Q despreading obtaining for each footpath _{l, 1}, u _{l, 2}... u _l,Qcarry out equal gain combining, complete the complementary correlated process of mutual-complementing code, l ∈ { 1,2, L ..., L},

That is:

$U_l^{\left(g\right)}\left(j\right)=\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{u}_{l,q}^{\left(g\right)}\left(j\right)$

Step the May 4th, high specific criterion is adopted to merge the detection signal on each footpath obtained, that is:

$y_1^{\left(g\right)}\left(j\right)=\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\left(h_{1,l}^{\left(g\right)}\right)}^{*}{U}_l^{\left(g\right)}\left(j\right)$

Wherein, for the multiple decay factor in l footpath of the 1st subcarrier experience of user g, * represents and asks conjugation; Complete the despreading process of subcarrier 1.

The present invention is compared with the CC-CDMA of traditional parallel frequency division, and the time-frequency mixed molecules code plan that the present invention proposes can utilize the autocorrelation performance that on each subcarrier, multiple subcode is realized ideal, and then effectively resists the multi-path jamming in the subband of each subcarrier.Under three identical footpath channels (channel fading factor variance is [0.7,0.2,0.1], and time delay is [0,2,4]), there are 4 users in system, and under all adopting the simulated conditions of 4 subcarriers, the error rate contrast of two kinds of systems as shown in Figure 6.When signal to noise ratio is 10dB, the error rate of present system can reach 3 × 10 ^-4, and Traditional parallel frequency division systems only reaches 6 × 10 ^-3.

Accompanying drawing explanation

Fig. 1 is the structural representation of transmitter in present system;

Fig. 2 shows structural representation for the subcarrier spread spectrum module of subcarrier 1;

Fig. 3 is signal structure schematic diagram after the subcarrier spread spectrum module spread spectrum for subcarrier 1;

Fig. 4 is the structural representation of receiver in present system;

Fig. 5 shows structural representation for the subcarrier solution frequency module of subcarrier 1;

Fig. 6 is that mixed molecules code structure CC-CDMA system of the present invention and Traditional parallel frequency division CC-CDMA error rate of system contrast schematic diagram.

Embodiment

Embodiment one, composition graphs 1 to 6 illustrate this embodiment, time a kind of-and the mutual-complementing code cdma system of frequently hybrid separation subcode structure,

The signal emission process of transmitter:

For user k process of transmitting, transmitter architecture is as shown in Fig. 1 and 2, and process of transmitting mainly comprises the steps:

The data b of step one, user k ^(k)w the sub-frequency spectrum module corresponding to W group subcode is entered respectively, as shown in Figure 1 after copying W part.

Step 2, W sub-frequency spectrum module adopts corresponding one group of subcode to carry out spread spectrum to the data of user k respectively, and for first sub-frequency spectrum module, as shown in Figure 2, the signal structure after spread spectrum as shown in Figure 3 for its process. represent the jth data that user k sends in a data block, j ∈ 1,2 ..., x}, wherein x represents the bit number that each data block sends, and is determined by the time-varying characteristics of channel.T _cbe the duration of a chip, T _gfor adopt different subcode spread spectrum data between the length at protection interval, to be expanded according to the maximum delay of transmission delay, channel by channel estimation module and synchronous error is determined.

Detailed process is, each data first in data block adopt Q subcode to carry out spread spectrum respectively, in subcarrier 1, adopts the signal after q subcode spread spectrum to be

$d_{1,q}^{\left(k\right)}\left(t\right)=\sqrt{p_k}\underset{j=0}{\overset{B-1}{\mathrm{\Σ}}}{b}_j^{\left(k\right)}{C}_{1,q}^{\left(k\right)}(t-\mathrm{jN}{T}_c)---\left(1\right)$

Wherein, q ∈ 1,2 ..., Q}, pk are transmitted power, for the frequency spreading wave corresponding to a subcarrier 1 q subcode of user k, be expressed as:

$C_{1,q}^{\left(k\right)}\left(t\right)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{c}_{q,n}^{\left(k\right)}q(t-n{T}_c+T_c)---\left(2\right)$

Wherein, q (t) is chip transmission pulse waveform.Consider simplicity, can suppose that q (t) is for rectangular pulse, that is:

$q\left(t\right)=\left\{\begin{array}{cc}\frac{1}{\sqrt{T_c}}& 0\≤t\≤T\\ 0& \mathrm{elsewhere}\end{array}---\left(3\right)\right.$

Subsequently, the data after spread spectrum carry out serial/parallel conversion respectively, are then stitched together in order, and intubating length is the protection interval of G chip lengths between adjacent two subcode spread-spectrum signals, i.e. T _g=GT _c.Spliced data obtain the output signal of this subcarrier spread spectrum module after carrying out parallel/serial conversion its structure as shown in Figure 3.

The length T at protection interval _gby subchannel maximum delay expand and multi-user between synchronous error maximum determine, that is: T _g>=| τ _l,k-τ _z,g+ θ _k-θ _g|, wherein τ _l,kand τ _z,gbe respectively the propagation delay in any footpath of any user, θ _kand θ _gthe signal being respectively any two users arrives the time delay of receiver.

Step 3, as shown in Figure 1, the signal that W sub-frequency spectrum module exports be modulated to W subcarrier f respectively ₁, f ₂..., f _won, be sent in wireless channel after last W subcarrier superposition and go.

The Signal reception process of receiver:

The present invention is applicable to frequency selective fading channels, and the coherence bandwidth of channel is less than the bandwidth of a subcarrier.To the subchannel independently modeling of each subcarrier.Because the bandwidth of each subcarrier is identical, therefore, the channel of W subcarrier can be modeled as the distinguishable footpath (L footpath) and the identical (τ of corresponding each footpath time delay with identical number ₁, τ ₂..., τ _l) independent identically distributed tap line delay model.Assuming that w subcarrier is the slow fading channel in L footpath, then its equivalent low pass channel can describe with following time varying impulse response:

Wherein, for the multiple decay factor in l footpath of w the subcarrier experience of user k, τ _l,kt propagation delay that () is this footpath.Assuming that channel is gradual channel, namely suppose and τ _l,kt () is at least constant in x bit transmitting time.

Have K user to communicate in system, for the receiving course of user g, as shown in figs. 4 and 5, the signal detection process of receiver mainly comprises the steps: receiver structure simultaneously

Step 4, as shown in Figure 4, receiver is demodulation W subcarrier f respectively ₁, f ₂..., f _won data, the W an obtained baseband signal enter W subcarrier despreading module of corresponding W group subcode respectively.

Step 5, W subcarrier solution frequency module adopts corresponding subcode carry out despreading and merge to the signal of each subcode spread spectrum on each footpath respectively.For first subcarrier despreading module, its process as shown in Figure 5.Comprise following sub-step:

In step May Day, Fig. 5, first group of signal postponed for each footpath of aliging, namely postpones τ _l,gcorresponding subsequent treatment is the signal in l footpath in the propagation channel of detection user g.Second group of signal postponed for the subcode spread spectrum that aligns, the subsequent treatment namely postponing (q-1) △ corresponding is that employing q subcode carries out despreading.

Step 5 two, carry out matched filtering and despreading for L footpath, a Q subcode respectively.Assuming that carrier wave, bit and chip synchronization that the signal of receiver and user g is realized ideal, for a user g jth data in l footpath by q subcode despreading detailed process be:

$u_{q,l}^{\left(g\right)}\left(j\right)={{\∫}_0^{{\mathrm{NT}}_c}r}_1(t+j{T}_b+{\mathrm{\τ}}_{l,g}+(q-1)\mathrm{\Δ})C_{1,q}^{\left(g\right)}\left(t\right)\mathrm{dt}---\left(5\right)$

Wherein, l ∈ 1,2 ..., L}, q ∈ 1,2 ..., Q}, j ∈ 1,2 ..., x}, T _b=(xN+G) T _c, △=GT _c, for the frequency spreading wave corresponding to a subcarrier 1 q subcode of user g, as the formula (2).

Signal u after step 5 three, Q despreading obtaining for each footpath _{l, 1}, u _{l, 2}... u _l,Q, { 1,2, L, L} carry out equal gain combining to l ∈, complete the complementary correlated process of mutual-complementing code, that is:

$U_l^{\left(g\right)}\left(j\right)=\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{u}_{l,q}^{\left(g\right)}\left(j\right)---\left(6\right)$

Step the May 4th, as shown in Figure 5, adopts high specific criterion to merge the detection signal on each footpath obtained, that is:

$y_1^{\left(g\right)}\left(j\right)=\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\left(h_{1,l}^{\left(g\right)}\right)}^{*}{U}_l^{\left(g\right)}\left(j\right)---\left(7\right)$

Wherein for the multiple decay factor in l footpath of the 1st subcarrier experience of user g, * represents and asks conjugation.So far the despreading process of subcarrier 1 is completed.

Step 6, as shown in Figure 4, the signal of W subcarrier despreading step 2 obtained is with weight merge:

${\hat{b}}^{\left(g\right)}\left(j\right)=\underset{w-1}{\overset{w}{\mathrm{\Σ}}}{\mathrm{\μ}}_w{y}_w^{\left(g\right)}\left(j\right)---\left(7\right)$

Wherein, μ _wbe the merging weight coefficient that w sub-carrier signal is corresponding, this weight can be obtained by the mode of maximum-ratio combing criterion, minimum mean-square error combining criterion or self-adopt combination.For minimum mean-square error combining criterion, weight coefficient obtains as follows:

${\mathrm{\μ}}_w=\frac{\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\left|h_{w,l}^{\left(g\right)}\right|}^2}{\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{\left|h_{w,l}^{\left(g\right)}\right|}^2+\frac{{\mathrm{WE}}_B}{N_u{N}_0}}---\left(8\right)$

Wherein, N _ufor active users, E _bfor bit energy, N ₀for the power spectral density of channel white Gaussian noise.Result after finally merging send into decision device and complete receiving course of the present invention.

A CC-CDMA system adopts gang mutual-complementing code C (K, M, N) as the address code of K user, and wherein M is the subcode number that a mutual-complementing code comprises, and N is the code length of each subcode, i.e. its number of chips comprised.Suppose that the mutual-complementing code distributing to user k is $C^{\left(k\right)}=\{c_m^{\left(k\right)}{\}}_{m=1}^M\∈C(K,M,N),k\∈\{\mathrm{1,2},...K\}.$ Wherein, $c_m^{\left(k\right)}=[c_{m,1}^{\left(k\right)},c_{m,2}^{\left(k\right)},...,c_{m,N}^{\left(k\right)}]$ Be m subcode (subsequence), m ∈ 1,2, L, M}, n ∈ { 1,2, L, N}.Time of the present invention-the CC-CDMA system of frequently hybrid separation subcode structure in, K the subcode distributing to user is divided into W=M/Q group, namely $S_2^{\left(k\right)}={\left\{c_m^{\left(k\right)}\right\}}_{m=Q+1}^{2Q}...S_W^{\left(k\right)}={\left\{c_m^{\left(k\right)}\right\}}_{m=M-Q+1}^M.$ This mutual-complementing code has following two characteristics.

Characteristic 1: mutual-complementing code has correlation properties desirable complementary aperiodic

$\mathrm{\ρ}(C^{\left(k\right)},C^{\left(g\right)},\mathrm{\δ})=\underset{m=1}{\overset{M-1}{\mathrm{\Σ}}}\underset{n=1}{\overset{N-\mathrm{\δ}}{\mathrm{\Σ}}}{c}_{m,n}^{\left(k\right)}{c}_{m,n+\mathrm{\δ}}^{\left(g\right)}=\left\{\begin{array}{cc}\mathrm{MN},& \mathrm{\δ}=0,k=g\\ 0,& \mathrm{elsewhere}\end{array}\right.$

Wherein, k ∈ 1,2 ..., K}, δ are relative chip shift.

Characteristic 2: the W group subcode group of mutual-complementing code there is desirable complementation autocorrelation performance aperiodic

$\mathrm{\ρ}(S_w^{\left(k\right)},S_w^{\left(k\right)};\mathrm{\δ})\underset{q=(w-1)Q+1}{\overset{\mathrm{wQ}}{\mathrm{\Σ}}}\underset{n-1}{\overset{N-\mathrm{\δ}}{\mathrm{\Σ}}}{c}_{q,n}^{\left(k\right)}{c}_{q,n+\mathrm{\δ}}^{\left(k\right)}=\left\{\begin{array}{cc}\mathrm{QN}& \mathrm{\δ}=0\\ 0& \mathrm{elsewhere}\end{array}\right.$

Wherein, k ∈ 1,2 ..., K}, w ∈ 1,2 ..., W}, δ are relative chip shift.

The present invention is compared with the CC-CDMA of traditional parallel frequency division, and the time-frequency mixed molecules code plan that the present invention proposes can utilize the autocorrelation performance that on each subcarrier, multiple subcode is realized ideal, and then effectively resists the multi-path jamming in the subband of each subcarrier.Under three identical footpath channels (channel fading factor variance is [0.7,0.2,0.1], and time delay is [0,2,4]), there are 4 users in system, and under all adopting the simulated conditions of 4 subcarriers, the error rate contrast of two kinds of systems as shown in Figure 6.When signal to noise ratio is 10dB, the error rate of present system can reach 3 × 10 ^-4, and Traditional parallel frequency division systems only reaches 6 × 10 ^-3.

Claims (1)

1. time-and the mutual-complementing code cdma system of frequently hybrid separation subcode structure, it is characterized in that:

For user k, the signal emission process of transmitter:

Step one, by the data b of user k ^(k)copy W part, W is positive integer, and is emitted to W sub-frequency spectrum module respectively, and each subcarrier spread spectrum module is a corresponding Q subcode respectively;

Step 2, W sub-frequency spectrum module adopts one group of corresponding subcode to carry out spread spectrum to the data of user k respectively, obtains the signal after spread spectrum

The detailed process of each subcarrier spread spectrum module spread spectrum is:

First, adopt Q subcode to carry out spread spectrum respectively each data in subcarrier, Q is positive integer;

Then, the data after spread spectrum are carried out serial/parallel conversion respectively, is then stitched together in order, and intubating length is the protection interval of G chip lengths between adjacent two subcode spread-spectrum signals, G is positive integer;

Finally, spliced data obtain the output signal of this subcarrier spread spectrum module after carrying out parallel/serial conversion w=1,2 ..., W;

Step 3, by step 2 obtain spread spectrum after signal be modulated to W subcarrier f respectively ₁, f ₂..., f _won, be then sent to wireless channel by after W subcarrier superposition; The signal completing transmitter is launched;

For user g, the Signal reception process of receiver:

Step 4, subchannel independently modeling to each subcarrier, the Channel Modeling of W subcarrier is have the distinguishable footpath that identical number is L, and corresponding each footpath time delay τ ₁, τ ₂..., τ _lidentical independent identically distributed tap line delay model; Receiver is demodulation W subcarrier f respectively ₁, f ₂..., f _won data, the W an obtained baseband signal and be emitted to W subcarrier despreading module respectively, described each subcarrier despreading module corresponding Q subcode respectively;

Step 5, W subcarrier solution frequency module adopts corresponding subcode carry out despreading and merge to the signal of each the subcode spread spectrum on each footpath respectively, obtains the signal of W subcarrier despreading;

Step 6, the signal of W subcarrier despreading that step 5 obtained are with weight merge, obtain the result after merging carry out adjudicating rear output;

Complete the Signal reception of receiver;

In step 5, W subcarrier solution frequency module adopts corresponding subcode to carry out despreading to the signal of each the subcode spread spectrum on each footpath and the method merged is all identical with the 1st subcarrier respectively, is specially:

Step May Day, adopt first group of delay to carry out alignment operation to the signal in each footpath, that is: postpone τ _l,gcorresponding subsequent treatment is the signal in l footpath in the propagation channel of detection user g; Adopt second group of delay to carry out alignment operation to the signal of subcode spread spectrum, that is: the subsequent treatment postponing (q-1) Δ corresponding is that employing q subcode carries out despreading;

Step 5 two, carry out matched filtering and despreading for L footpath, a Q subcode respectively, to obtain on every footpath signal u after Q despreading _{l, 1}, u _{l, 2}... u _l,Q, l=1,2 ..., L;

Signal u after step 5 three, Q despreading obtaining for each footpath _{l, 1}, u _{l, 2}... u _l,Qcarry out equal gain combining, complete the complementary correlated process of mutual-complementing code, l ∈ 1,2 ..., L},

That is:

$U_l^{\left(g\right)}\left(j\right)=\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{u}_{l,q}^{\left(g\right)}\left(j\right)$

Step the May 4th, high specific criterion is adopted to merge the detection signal on each footpath obtained, that is:

$y_1^{\left(g\right)}\left(j\right)=\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\left(h_{1,l}^{\left(g\right)}\right)}^{*}{U}_l^{\left(g\right)}\left(j\right)$

Wherein, for the multiple decay factor in l footpath of the 1st subcarrier experience of user g, * represents and asks conjugation; Complete the despreading process of subcarrier 1.