CN1163014C - Code division multiple access spreading and despreading method and its transmitter, receiver and communication system - Google Patents

Abstract

The invention relates to a code division multiple access spreading and despreading method for eliminating multipath interference, a corresponding transmitter, a receiver and a communication system. The feature of the present invention is to change the continuous spread spectrum method of each symbol in the information symbol flow by the orthogonal spread code in the traditional CDMA spread spectrum step to change the spread spectrum in a discrete manner for each symbol, and the information of different users is still code division multiple access. From the perspective of the receiver, this transmission technique completely transforms the multiple access interference caused by multipath in the traditional CDMA system into the overlapping of symbols of respective users (or the so-called inter-symbol interference in the traditional technology). On the basis of eliminating multiple access interference, each information symbol used is obtained from overlapping symbols by solving equations. Since the present invention completely eliminates multiple access interference, the system capacity is completely determined by non-system noise. And improving the spreading ratio becomes an effective method to improve the system capacity.

Description

Code division multiple access spreading and despreading method and its transmitter, receiver and communication system

technical field

The present invention relates to a spread spectrum and despread method based on code division multiple access and a transmitter, a receiver and a communication system realized by using the method.

Background technique

In the existing CDMA system, the information transmission of multiple users is distinguished by codes, so it is a parallel multi-channel structure under a certain bandwidth. In a high-quality synchronous direct spread spectrum CDMA system, the above-mentioned parallel multi-channels are assigned to multiple users, and the user's information symbols are spread with orthogonal spread spectrum codes. The receiver obtains certain user information by means of correlation calculation. While other user signals are canceled due to orthogonality.

However, in a multipath environment, the above technology cannot maintain the orthogonality of the spreading codes of each user. The reason is that the synchronous modulation technology can only guarantee the orthogonality of spreading codes of different users belonging to the same path in the time domain, but loses the orthogonality of the signals belonging to different paths superimposed on it (the signal delay in the time domain Signals with a duration greater than one chip are defined as signals of different paths), thus causing mutual interference of various users, also known as multiple access interference (MAI). This interference is currently the most important factor limiting the capacity of the CDMA system. In the direct spread spectrum communication system, considering the time delay of the frequency selective fading channel, this time delay is determined by the characteristics of the channel and cannot be changed by humans, and it is this time delay that leads to multipath generated, causing great disturbance to the system.

The concept of the fourth-generation mobile communication system can be called a broadband (Broadband) access and distribution network, and its data transmission rate greatly exceeds that of the third-generation mobile communication system in indoor, outdoor and mobile environments. Due to the increase of communication bandwidth, multipath interference becomes more serious. Therefore, multiple access interference becomes a problem that we urgently need to solve.

Contents of the invention

Aiming at the defects of the existing spread spectrum method, the present invention proposes a key technology designed for the fourth generation mobile communication (4G)—a discrete spread spectrum method.

The first object of the present invention is to provide a discrete spread spectrum method that can eliminate multipath interference in a frequency selective fading channel by utilizing the orthogonality of spread spectrum codes.

A second object of the invention is to provide a corresponding demodulation method.

The third object of the present invention is to provide a de-dispersion method so that the traditional de-spreading method can also be used for signal demodulation.

A fourth object of the present invention is to provide a method for separating superimposed symbols.

A fifth object of the present invention is to provide a transmitter, receiver and communication system capable of eliminating multipath interference.

In the discrete spreading method according to one aspect of the present invention, each user information symbol is spread using orthogonal spreading codes. Information symbols can be modulated by BPSK\QPSK or QAM. Therefore, the concept of code division multiple access is still applicable in this technology. Compared with the traditional CDMA spread spectrum method, we discretely distribute the spread spectrum data corresponding to an information symbol at equal intervals one by one in time sequence. If this interval is the duration of (M+L) chips, and each time delay is one chip later, then one spread information symbol can be placed. Until a total of (L+M) information symbols are placed. We define this (L+M) data as a data block. In the data block, M information symbols are independent, and L information symbols are multipath data prefix symbols. The information prefix symbols take the last L symbols in M. When transmitting, the prefix symbol precedes the independent information symbol.

It should be noted that the above modulation method is applicable to the case where the maximum multipath time delay is less than L chips. In addition, if the spreading ratio is n, the data block length is n(L+M) chip durations.

According to the first demodulation method of another aspect of the present invention, the spreading code correlation of the user is used for the discrete information symbols passing through the multipath channel on its discrete corresponding positions, and then the current information symbols and the previous several information symbols of the user are obtained overlay results. We define this correlation method as a discrete correlation method. The correlation operation shall start from the L+1th symbol. That is: the first L prefix symbols of the data block are discarded. Note: Superimposition of information symbols is caused by multipath.

According to the second demodulation method of another aspect of the present invention, the discrete information symbols passing through the multipath channel are rearranged. Arranging the symbols arriving on the first path in symbol order is a traditional continuous spread spectrum method. Utilize the traditional despreading method, that is, the continuous despreading method, to demodulate from the L+1th symbol.

According to the information symbol separation method of another aspect of the present invention, for the results of demodulation by the above two methods (they give the same result), the equation is solved to separate the transmitted information symbols. Thus realizing the transmission of information symbols.

The transmitter and receiver according to another aspect of the present invention implement communication by using the discrete spread spectrum method and the discrete correlation method or the de-dispersion and traditional de-spreading methods respectively.

Description of drawings

Preferred embodiments according to the present invention will be described below with reference to the accompanying drawings, in which the same reference numerals denote the same or similar components.

Fig. 1 is the flowchart showing existing mobile communication system;

Fig. 2 is a structural diagram of the system according to the present invention;

Fig. 3 is the flowchart showing the discrete spread spectrum method according to the present invention;

Fig. 4 is the flow chart showing the method for separating discrete spread spectrum according to the present invention;

Fig. 5 is the structural block diagram of spreader and discretizer in the transmitter according to the present invention;

Fig. 6 is the structural block diagram of solution discretizer and despreader in the receiver according to the present invention;

Fig. 7 is to show when the spread spectrum ratio is n=16 according to the bit error rate of the system of the present invention along with the change graph of SNR; And

Fig. 8 is a graph showing the variation of the system bit error rate with the spreading ratio when SNR=0dB.

Detailed ways

First, a CDMA mobile communication system according to the prior art will be described with reference to FIG. 1 .

On the transmitter 14 side, the data packets to be transmitted are sequentially read from the data packet memory 11 . Modulation is performed in the modulator 12, and the modulation mode can be BPSK\QPSK or QAM mode. The modulated data is sent to the frequency spreader 13, and in the frequency spreader 13, the PN code is used for CDMA spreading. It is then sent out via an antenna (not shown). The signal sent by the transmitter is received by the receiver 16 after undergoing multi-path channel, and the original data packet is obtained after the despreader 17 and decision demodulation 18 . Thereby completing a process of communication.

See Figure 2 now. In the discrete spread spectrum communication system of the present invention, in the transmitter 23, a device 21 for setting a prefix is added between the existing data packet memory 11 and the modulator 12, which is used for the data packet to be sent The prefix is set so that the receiver can obtain the original data packet by solving the equation for the received signal. And a discretizer 22 is added between the spreader 13 and the antenna (not shown), which is used to perform the method of discretely arranging the chips of the symbols to be transmitted according to the present invention before transmitting the information symbols.

In the receiver 24 the received information symbols first pass through a de-discreteizer 25 which is used to de-discretize the information symbols sent by the transmitter 23 . Then a timer 26 is used to select a piece of required information from the de-discrete information and send it to the despreader 17 for despreading. Since the user information included in the piece of information selected by the timer maintains an orthogonal relationship with the multipath information of other users, the information obtained after despreading has eliminated the multipath interference of other users. Although the information of other users is eliminated by the information after despreading, the main path information of this user and the side path information are delayed by an integer number of symbols and overlap each other, so the data after despreading need to be sent to the solver 27 Establish a system of equations, and obtain the original data packet by solving the equations.

Referring to FIG. 3, the working flow of the discretizer 22 of the present invention will be further described. At first it should be pointed out that before the step S1 shown in Fig. 3, the data to be sent has been divided into M symbols as a data block, and the last L symbols of the M symbols in each data block are appended to the Before the symbol group, as L prefix symbols. Thus, a group of M+L symbols is formed as a data block. Wherein, L is an integer greater than or equal to the maximum number of delay chips in the multipath channel; M is an integer greater than L.

In step S1, the sequence of symbols to be transmitted is stored in the register in order of the above-mentioned M+L symbols as a group, assuming that each symbol has n chips.

In step S2, a set of symbols is stored in a register, ready for discrete arrangement.

In steps S3-S6, according to the order of the symbols, the i-th chip of each symbol in the group of symbols is sequentially taken out and sent. Until each chip in the group of M+L symbols is obtained.

In step S7, it is judged whether to discretely arrange and send all the data packets to be sent. This ends the operation in the discretizer if the transmission is complete.

The operation flow of the de-segregator 25 in the receiver 24 will be described below with reference to FIG. 4 .

In step S11, conventional timing and synchronization methods are used to determine each data block divided at the transmitter side. As described above, each data block has a length of M+L symbols, with (M+L)*n chips.

In step S12, a data block is stored in the register.

In the step S13-S16 process, at first the pointer i is initialized to 1, and then the i-th chip, M+L+i, 2(M+L) is sequentially taken out from the i-th chip of the data block stored in the register +i..., (n-1)×(M+L)+i chips, and output to the timing device. After each cycle, the value of i is increased by 1, and the next cycle is executed until all chips are taken. The processing in the de-discreteizer 25 is thereby completed.

Describe the effect and the function of timer 26, despreader 17, equation solver 27 below, in timer 26, the chip that is taken out by solution discretizer 25 is stored in the register of timer 26 according to the sequence, by routine The timing method of takes out the last M symbols in the set of data. The main path signals of the desired user and other users, as well as the multipath delayed signals of these users are included in the last M symbols, but there is an integral number of symbols between the main path signal and the multipath delayed signals, so although there is a multipath delay , but the signals of different users maintain an orthogonal relationship (this will be described in more detail below). Then the extracted M symbols are sent to the despreader 17 for conventional despreading processing. Since the signals of different users still maintain an orthogonal relationship, the main path signals and multipath signals of other users are completely eliminated in the signals obtained through despreading. However, the data obtained after despreading is the result of misplaced superposition between the main path signal of the desired user and the multipath signal of the user in units of symbols according to different amplitude ratios. Therefore, each symbol can be found by setting up a system of equations in the equation solver 27 and solving the equations. And arrange each obtained symbol according to the order of transmission, and send it to the decision demodulator 18 for demodulation.

So far, the principles and specific steps of the present invention have been generally described with reference to FIGS. 1 to 4 . The principle of the present invention will be described in more detail below by means of mathematical formulas.

Discrete spread spectrum is to disperse each information symbol in the information stream in a periodic manner, and then multiply it with the user's orthogonal spread spectrum code at the corresponding position, that is, the discrete spread spectrum method. From the perspective of the transmitted data form, it is equivalent to the discrete arrangement of the traditional CDMA transmitted data.

1. The basic method of discrete spread spectrum

First of all, for ease of understanding, we give the data flow form of traditional CDMA. Using the chip duration as the minimum measurement unit of the time process, the data stream composed of M data in traditional CDMA can be written as:

${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

The expression s _i ^(k) p _{k, j} is the data stream, where k represents the signal of the kth user, s _i represents the i-th information symbol of the user, and p _{k, j} represents the j-th information symbol for the i symbol A spreading code value. Under orthogonal code modulation, the orthogonality is expressed by the following formula:

The discrete spread spectrum method of the present invention is used for the sequence described in (1) above, and M symbols are used as a group to adjust the transmission order of each chip in each symbol. Specifically, put the i-th chip of each symbol in the M symbols together and arrange them sequentially, for example, first send the first chip s ₀ ^(k) p _{k of each symbol in the order of the symbols, 0} , s ₁ ^(k) p _{k, 0} , s ₂ ^(k) p _{k, 0} …s _M-1 ^(k) p _{k, 0} , and then send the second chip s ₀ ^(k) of each symbol p _{k, 1} , s ₁ ^(k) p _{k, 1} , s ₂ ^(k) p _{k, 1} ... s _M-1 ^(k) p _{k, 1} , and so on.

The discrete spread spectrum data stream composed of (L+M) symbols can be expressed as:

${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span>$

${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Under the condition of transmission synchronization, the mathematical expression of the multi-user channel transmission signal:

$\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

in

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; CP</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Represents the user's characteristic function, where S(t) is the transmitter output signal, t represents time, and CP(u) is a square wave function:

2. Orthogonality under multipath channel conditions

Assumption: the maximum delay of the multipath channel is the duration of L chips, after the discrete spread spectrum signal experiences the multipath channel, its data flow has the following form

Among them: υ(t) is the received signal, α _l is the multipath fading coefficient; T _c represents the duration of one chip, l is an integer, which marks the time delay.

If the receiver correlation function is defined as:

${\mathrm{<span\; class="notranslate">\; d</span>}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; \&prime;</span>}{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; p</span>}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; LT</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Where: j' is the synchronization coefficient of the receiver. Through the following related operations:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\overset{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; nM</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; \&upsi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>{{\mathrm{<span\; class="notranslate">\; d</span>}}^{<span\; class="notranslate">\; *</span>}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; \&prime;</span>}{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; j</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

We get the kth user information symbol, while other user signals are eliminated due to orthogonality.

That is to say, the signal obtained after adopting the discrete spread spectrum method of the present invention to spread through the multipath channel, the signal obtained after despreading with the despread method of the present invention at the receiver, and the multipath signals of other users Maintain an orthogonal relationship. Multipath interference is thus eliminated.

On the other hand, in order to more clearly illustrate the demodulation method 2 of the spread spectrum method of the present invention, it is assumed below that the signal chip s _i ^(k) p _k of a certain user is expressed as a _ij (i, j=0, 1, 2, 3), where each symbol has 4 chips, that is to say, the spreading ratio is 4, then there are:

In prior art:

The original sent data is:

After passing through the multipath channel, due to the multipath delay, multiple paths that delay an integer number of chips are formed. Here, it is assumed that there is one path and the main signal is only delayed by one chip, then:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

It can be seen from the above that A is the main signal, and B is the side path delayed by one chip. A and B have their own fading coefficients, and they are superimposed on the corresponding chips. A5, A6, A7, and A8 in the above table are a symbol composed of 4 chips of the main signal A, which are staggered and superposed with the corresponding symbols B6, B7, B8, and B9 in the side path B by one chip. Due to the multipath delay, the main signal of a certain user and the delayed sidepath signals of itself and other users are staggered by an integer number of chips, thereby destroying the orthogonality and generating so-called multipath interference.

According to the present invention, spreading is performed using the discrete spreading method of the present invention before data is transmitted. Assume that M=3 symbols are used as a group, and L=1 is used as the number of prefix symbols. The information prefix symbols take the last L symbols in M. When transmitting, the prefix symbol precedes the independent information symbol.

Assume that the group formed by these M symbols is:

In order to clearly show the position of each chip in one of the symbols, choose

Reference.

Then the prefix symbol is:

a ₂₀ a ₂₁ a ₂₂ a ₂₃

The symbol group after the prefix is set in the setting prefix device 21 in Fig. 2 is:

a ₂₀ a ₂₁ a ₂₂ a ₂₃ a ₀₀ a ₀₁ a ₀₂ a ₀₃ a ₂₀ a ₂₁ a ₂₂ a ₂₃

The symbol group after the discretizer 22 carries out the discrete arrangement is:

a₂₁  a₂₂  a₀₂

a₂₂  a₂₃  a₀₃

a₂₃ a ₂₀ a ₀₀ a ₂₀ a ₂₁ a ₀₁

a ₂₁ a ₂₂ a ₀₂

a ₂₂ a ₂₃ a ₀₃

a ₂₃

Assuming that this group of data blocks has only one chip delay after passing through the multipath channel, the signal received by the receiver is:

A is the main path signal, and B is the multipath signal delayed by one chip.

Assuming that the receiver simultaneously receives another user b's data block sent after the same discrete spread spectrum and the user b's multipath delay signal:

Since user a and user b share the same frequency band, when received in the receiver, they are superimposed on each other:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

The resulting data block after de-discretization is:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Since the de-discretization is the inverse transformation of the discretization process, it can be seen that row A restores the original sorting. After row B is reordered, in columns 5-16, the order of each symbol is adjusted relative to the symbols in row A, and aligned with the symbols in column A.

Rows C and D are also integer-symbol-aligned in columns 5-16, since each symbol is multiplied with a spreading code in the transmitter. In the timer 26, the signals in the 5th to 16th columns are selected by means of timing and synchronization for despreading.

5 6 7 8 9 10 11 12 13 14 15 16

The spreading codes between user a and user b have an orthogonal relationship. If the same spreading code as user a is used in the receiver for despreading, the signal of user b can be completely eliminated.

The despread signal is:

5 6 7 8 9 10 11 12 13 14 15 16

This is the result of the superimposition of the A-path signal and the B-path signal of user a. Each symbol can be found by establishing an equation.

For example, assume unknown symbols x ₁ =a ₀₀ , a ₀₁ , a ₀₂ , a ₀₃ ; x ₂ =a ₁₀ , a ₁₁ , a ₁₂ , a ₁₃ ; x ₃ =a ₂₀ , a ₂₁ , a ₂₂ , a ₂₃ ; A The fading coefficient of path B is k _A ; the fading coefficient of path B is k _B . The fading coefficient can be obtained by performing channel estimation before sending a signal or by periodically using pilot symbols, etc., and the fading coefficient generally does not change during the signal sending process. The superimposed signals received are R ₁ , R ₂ and R ₃ .

From the above superposition results, it can be concluded that:

k _A x ₁ + k _B x ₃ = R ₁ ;

k _A x ₂ + k _B x ₁ = R ₂ ;

k _A x ₃ + k _B x ₂ = R ₃ ;

Among them, k _A , k _B , R ₁ , R ₂ and R ₃ are known, and there are three unknowns and three equations, so the values of each symbol x ₁ , x ₂ and x ₃ can be solved.

A more general system of equations is the following matrix multiplication form, where _ki is the modulus of the i-th path fading coefficient, ki is known after channel estimation, _{R i is} the related despreading value and is also known, and xi _is Data symbols to be requested, i=1, 2, 3...M.

A specific embodiment of the present invention will be described below with reference to FIGS. 5 and 6. FIG. Fig. 5 is a structural block diagram of a spreader and a discretizer in a transmitter according to the present invention, and Fig. 6 is a structural block diagram of a de-scatterer and a despreader in a receiver according to the present invention.

In Fig. 5, a circuit structure is adopted to realize the discrete spread spectrum method of the present invention. This circuit structure realizes the functions of the frequency spreader 13 and the discretizer 22 shown in FIG. 2 and described above. It includes a symbol group module 31 , a cyclic shift register 32 , a multiplier 33 , a synchronization system 34 , an orthogonal code generator 35 , a chip clock 36 and a frequency divider 37 . The original symbol to be sent is stored in the symbol group module 31 . Driven by the chip clock 36, the symbol group module 31 outputs a group of symbols, the number of symbols is M+L, and then under the control of the synchronization system 34, the symbol module is in a waiting state. This group of symbols is input into the cyclic shift register 32, and under the drive of the chip clock 36, it is cyclically output n times (n is the spreading ratio), and then the synchronization system 34 triggers the symbol group module to output another group of symbols, and the symbols The number is still M+L. The frequency divider 37 divides the frequency of the clock of the chip clock 36 into a frequency of 1/(M+L), drives the orthogonal code generator 35 to output the data of the pn code and the circular shift register output with the clock after the frequency division Multiplied in the multiplier 33, it can be known that each symbol of the pn code is multiplied with a group of symbols, thus completing the discrete spread spectrum process.

In FIG. 6, a circuit structure is used to realize the de-discrete spread spectrum method of the present invention. This circuit structure realizes the functions of the despreader 17 and the de-discreteizer 25 described in FIG. 2 and above. The circuit includes: a multiplier 41 , an adder 42 , a shift register 43 , an equation solver 44 , an orthogonal code generator 45 , a frequency divider 46 , a chip clock 47 , a synchronization system 48 and a channel estimator 49 . The frequency divider 46 divides the frequency of the clock from the chip clock 47 into a frequency of 1/(M+L), and drives the orthogonal code generator 45 to output the pn code with the divided clock. The n×(M+L) chips received by the receiver are sent to the multiplier 41 and the channel estimator 49 . The received chip sequence is multiplied by the pn code generated by the orthogonal code generator 45 in the multiplier 41 . The multiplication result is input to the adder 42 and the shift register 43 . Driven by the chip clock 47 , the shift register 43 returns the shifted output signal to the adder 42 for correlation and summing with subsequent signals, and outputs it to the equation solver 44 . The received signal is estimated at the channel estimator 49 for channel parameters such as the attenuation factor of each path of the Rayleigh channel and the like. The resulting channel parameters are fed to an equation solver 44 . The original signal is solved by the equation solver 44 by establishing a system of equations.

Please note that the example described above is only one embodiment of the present invention and not the only way to realize the present invention.

In the scheme proposed in this paper, since the spreading codes do not need to have good auto-correlation and cross-correlation properties, only the orthogonality of the spreading codes is required, and the walsh codes just meet this requirement. The suppression of multipath interference adopts the method of understanding equations, the system interference is completely eliminated, and all interference comes from non-system noise, so the performance is greatly improved. The number of multipaths that the system can resist is related to the size of the inserted redundancy. The greater the redundancy, the more the number of paths resisted.

Another advantage of the scheme proposed in this paper is that it has nothing to do with the spreading ratio, and the change of the spreading ratio does not affect the system design. Therefore, we can obtain higher processing gain by increasing the spreading ratio. In fact, every time the spreading ratio doubles, the system improves by 3dB.

The following are the computer simulation results.

a. The simulation conditions are as follows:

The inventor adopts Matlab emulation language programming, runs through under Windows2000. In the simulated SSS-CDMA spread spectrum system, the transmitter adopts BPSK modulation, that is, each symbol only represents one bit of information. Under the multipath channel, the maximum delay multipath includes a delay of 8 chips, and the magnitude of the attenuation factor of each path obeys the Rayleigh distribution with the same average power, while the phase obeys the uniform distribution of (0, 2π). The signals of multiple users are sent at the same time, and the non-system noise is additive white Gaussian noise (AWGN). At the receiving end, it is assumed that the system makes an ideal channel estimate, that is, it is assumed that the attenuation factor of each path of the channel is known during demodulation. Each group includes M=17 symbols, of which 8 symbols are repeatedly sent as a cyclic prefix.

b. Results

① Refer to the BER-SNR curve in Figure 7, which shows the variation curve of the system bit error rate with the signal-to-noise ratio when the spreading ratio is n=16. Among them, what SNR represents is the ratio of the average power of each path to the power spectral density of the system noise.

② Refer to the BER-n curve in Figure 8, which shows the variation curve of the system bit error rate with the spreading ratio when SNR=0dB.

Although the principle and implementation of the present invention have been described in detail above and with reference to the preferred embodiments of the present invention, those skilled in the art can make various modifications without departing from the scope of the present invention. For example, in this specification, setting a prefix is used as an example to increase the redundancy of the signal to be sent, so as to solve the equation at the receiver, but it is also possible to use the method of setting a suffix to place the first L symbols in the data block in the The end of the data block, or placed in other positions; the order of certain steps can also be changed or executed simultaneously, for example, in the receiver, the timing step can be performed after despreading first. These modifications and modified embodiments do not depart from the scope of the present invention defined in the claims of the present invention.

Claims (15)

1. CDMA spread spectrum method, comprising following steps:

The packet step, it is a plurality of data blocks of one group that data to be sent are divided into M symbol, M is the integer greater than 1;

Redundant step is set, selecting L symbol in the data block of each grouping and duplicating other positions that are put in this data block, forms the data block of M+L symbol, L is an integer that is less than or equal to M;

Modulation step is modulated the data block that redundant step gained is set;

The spread spectrum step is carried out CDMA spread spectrum to the data block after the modulation;

Discrete step rearranges the symbols behind the spread spectrum, chooses in M+L the symbol in each symbol the transmission of putting together of the 1st～n chip sequentially, and wherein each symbol comprises n chip.

2. spectrum spreading method according to claim 1 wherein in redundant step is set, copies to back L symbol of the symbol of the M in this data block before this data block, forms the data block of M+L symbol.

3. spectrum spreading method according to claim 1 wherein in redundant step is set, copies to preceding L symbol of the symbol of the M in this data block after this data block, forms the data block of M+L symbol.

4. code division multiple access despreading method is characterized in that comprising following steps:

Receive the grouping step, receive the data segment that sends corresponding in groups, every group of data segment comprises (M+L) * n chip;

It is rapid to separate discrete step, from the i of described one group of data block (i=1,2 ..., M+L) individual chip begins to take out successively i, M+L+i, 2 (M+L)+i..., (n-1) * (M+L)+i chip, and output to extraction step in proper order, up to having got all chips;

Extraction step according to the position that redundant symbol is set before sending in these data, takes out M symbol from separate the rapid symbol sebolic addressing that obtains afterwards of discrete step;

The despreading step is carried out despreading to the M that an is extracted symbol and is handled;

Solution procedure is set up equation group with M symbol of gained after the despreading as the result of original symbol sequence and known channel parameter inner product, solves an equation, and tries to achieve the symbol sebolic addressing of original transmission.

5. despreading method according to claim 4 is characterized in that, chooses a last M symbol in described extraction step.

6. despreading method according to claim 4 is characterized in that, the fading coefficients that adopts each footpath that draws by channel estimating in described solution procedure is set up equation group according to the number of chips of the delay between each footpath and found the solution as parameter.

7. CDMA transmitters, comprising as lower device:

Packet memory, it is that a plurality of data blocks of one group are stored that data to be sent are divided into M symbol, M is the integer greater than 1;

Redundant apparatus is set, selecting L symbol in the data block of each grouping and duplicating other positions that are put in this data block, forms the data block of M+L symbol, L is an integer that is less than or equal to M;

Modulating device is modulated the data block that redundant step gained is set;

The spread spectrum discrete device, data block after the modulation is carried out the orthogonal code division multiple access spread spectrum, then the symbols behind the spread spectrum is rearranged, choose in M+L the symbol in each symbol the transmission of putting together of the 1st～n chip sequentially, wherein each symbol comprises n chip.

8. transmitter according to claim 7 wherein in redundant apparatus is set, copies to back L symbol of the symbol of the M in this data block before this data block, forms the data block of M+L symbol.

9. transmitter according to claim 7 wherein in redundant apparatus is set, copies to preceding L symbol of the symbol of the M in this data block after this data block, forms the data block of M+L symbol.

10. transmitter according to claim 7, described spread spectrum discrete device comprises symbols register (31), circulating register (32), multiplier (33), synchro system (34), orthogonal code maker (35), chip clock (36) and frequency divider (37), wherein:

Storage original symbol to be sent in the symbols register (31);

Symbols register (31) is connected to chip clock (36), and exports a group code under the driving of chip clock (36), and symbol numbers is M+L, and under the control of synchro system (34), symbols register (31) is in wait state subsequently;

Circulating register (32) receives this group code from symbols register (31), under the driving of chip clock (36), circulation output n time, wherein n is a spreading ratio, then synchro system (34) again trigger symbol group register (31) export another group code, symbol numbers still is M+L;

Frequency divider (37) is the frequency division of the frequency of the clock of chip clock (36) frequency of 1/ (M+L), the data that drive orthogonal code maker (35) output pn sign indicating number and circulating register (32) output with the clock behind the frequency division multiply each other in multiplier (33), draw the discrete result of spread spectrum and output to subsequent conditioning circuit.

11. a CDMA receiver is characterized in that comprising as lower device:

The grouping register, reception and storage are corresponding to the data segment that sends in groups, and every group of data segment comprises (M+L) * n chip;

In bulk the putting of dissociating, the i of the described data block of from register, storing (i=1,2 ..., M+L) individual chip begins to take out successively i, M+L+i, 2 (M+L)+i..., (n-1) * (M+L)+i chip, and output to extraction element in proper order, up to having got all chips;

Extraction element according to the position that redundant symbol is set before sending in these data, takes out M symbol from separate the rapid symbol sebolic addressing that obtains afterwards of discrete step;

Despreading device carries out despreading to the M that an is extracted symbol and handles;

Solving device is set up equation group with M symbol of gained after the despreading as the result of original symbol sequence and known channel parameter inner product, solves an equation, and tries to achieve the symbol sebolic addressing of original transmission.

12. receiver according to claim 11 is characterized in that, chooses a last M symbol in described extraction element.

13. receiver according to claim 11 is characterized in that, the fading coefficients that adopts each footpath that draws by channel estimating in described solving device is set up equation group according to the number of chips of the delay between each footpath and is found the solution as parameter.

14. receiver according to claim 11, wherein said in bulk the putting of dissociating comprises shift register (43), adder (42) and chip clock (47); Described despreading device comprises multiplier (41), orthogonal code maker (45) and frequency divider (46): and described solving device comprise equation solver (44), synchro system (48) and and channel estimator (49), wherein:

Frequency divider (46) is the clock frequency frequency division from chip clock (47) frequency of 1/ (M+L), drives orthogonal code maker (45) output pn sign indicating number with the clock behind the frequency division;

N * (M+L) individual chip was sent to multiplier (41) and channel estimator (49) by receiver received;

The pn sign indicating number that in multiplier (41) chip sequence that is received and orthogonal code maker (45) is produced multiplies each other;

Multiplied result is imported into adder (42) and shift register (43);

Under the driving of chip clock (47), this shift register (43) turns back to the signal of displacement output in the adder (42) with afterwards signal and carries out relevant summation, and outputs to equation solver (44);

The signal that is received is estimated channel parameter at channel estimator (49), and resulting channel parameter is transported to equation solver (44);

Solve primary signal by equation solver (44) by setting up equation group.

15. a code division multiple address communication system comprises transmitter and receiver, it is characterized in that:

Described transmitter comprises as lower device:

Packet memory, it is that a plurality of data blocks of one group are stored that data to be sent are divided into M symbol, M is the integer greater than 1;

Redundant apparatus is set, selecting L symbol in the data block of each grouping and duplicating other positions that are put in this data block, forms the data block of M+L symbol, L is an integer that is less than or equal to M;

Modulating device is modulated the data block that redundant step gained is set;

The spread spectrum discrete device, data block after the modulation is carried out CDMA spread spectrum, then the symbols behind the spread spectrum is rearranged, choose in M+L the symbol in each symbol the transmission of putting together of the 1st～n chip sequentially, wherein each symbol comprises n chip; Described receiver comprises as lower device:

The grouping register, reception and storage are corresponding to the data segment that sends in groups, and every group of data segment comprises (M+L) * n chip;

In bulk the putting of dissociating, the i of the described data block of from register, storing (i=1,2 ..., M+L) individual chip begins to take out successively i, M+L+i, 2 (M+L)+i..., (n-1) * (M+L)+i chip, and output to extraction element in proper order, up to having got all chips;

Extraction element according to the position that redundant symbol is set before sending in these data, takes out M symbol from separate the rapid symbol sebolic addressing that obtains afterwards of discrete step;

Despreading device carries out despreading to the M that an is extracted symbol and handles;

Solving device is set up equation group with the symbol of gained after the despreading as the result of original symbol sequence and known channel parameter inner product, solves an equation, and tries to achieve the symbol sebolic addressing of original transmission.

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