CN101521535B - Base station transmitting circuit for CDMA system sparetime spread spectrum method - Google Patents

Abstract

The invention relates to a base station transmitting circuit of a space-time spread spectrum method in a CDMA system, comprising two down-sampling modules, a delay module connected with one down-sampling module, and a plurality of spread spectrum connected with the down-sampling module or the time-delay module respectively and two adders connected with the frequency spreader, the two down-sampling modules sample the data flow into two data flows, one of which is delayed by the delay module and enters the frequency spreader. The delay module adjusts the time difference between the two data streams to make the time difference equal to the time difference between the two data streams when the distance between the two transmitting antennas is 10-15 times the wavelength of the radio frequency signal. The spacing of the transmitting antennas need not be greater than 10-15 wavelengths of the transmitting signal. The distance between the transmitting antennas of the base station of the present invention can be in the range of 4 times greater than the wavelength of the transmitting signal to less than 10-15 times the wavelength of the transmitting signal, which is more suitable for engineering applications. Moreover, the circuit design is simple, and the spreading codes of the odd data stream and the even data stream are obtained by using one spreading code.

Description

Base Station Transmitting Circuit of Space-Time Spread Spectrum Method in CDMA System

This application is a divisional application of the invention patent application "CDMA system space-time spread spectrum method and corresponding mobile station receiving circuit". The original application date: March 12, 2004, application number: 200410008815.0, invention name: CDMA System space-time spread spectrum method.

technical field

The invention relates to a base station transmitting circuit of a space-time spread spectrum method in a CDMA system, and belongs to the field of mobile communication.

Background technique

The direct spread spectrum technology of multiple transmit antennas is used in the forward and reverse links of CDMA system, which can effectively improve the system performance. CDMA 1X adopts direct spread spectrum transmit diversity technology, which has two methods:

(1) One is Orthogonal Transmit Diversity OTD (Orthogonal Transmit Diversity)

The method is that the CDMA base station first separates the data streams and then spreads the two data streams with different orthogonal Walsh codes, and transmits them through two transmitting antennas of the base station.

(2) The other is the space-time spread spectrum diversity method STS (Space Time Spreading) CDMA base station uses two spatially separated antennas to transmit interleaved data, uses the same original Walsh code channel, and combines the odd data stream and the even data stream Rather than being transmitted separately through two antennas.

Using forward link transmit diversity technology can reduce transmit power, resist Rayleigh fading, and increase system capacity.

Although the complete spatial diversity (OTD) of the CDMA base station can be realized with two transmitting antennas, it is obtained at the cost of twice the bandwidth, and each user needs to use twice as much bandwidth to spread spectrum coding. The increased bandwidth resources limit the overall efficiency of the CDMA system.

In addition, in the direct spread spectrum orthogonal transmit diversity technique (OTD), the space diversity characteristic of the channel is not fully utilized. Any advantage of time diversity will disappear when the mobile station is caught in a deep fade in a slowly fading channel. Since many wireless data users of the 3rd generation communication are static or moving (walking) very slowly, the dependence on time-varying channel parameters is reduced, and the importance of space diversity is highlighted. This is detailed in the document co-authored by Hochwald B, Marzetta TL, Papadias C B: A Transmitter Diversity Scheme for Wideband CDMA Systems Based on Space-Time Spreading for Wideband CDMA Systems illustrate.

In the existing space-time spread spectrum technology (STS), the distance between the transmitting antennas of the base station must be greater than 10-15 times the wavelength of the radio frequency signal to ensure that the signals reaching each unit of the antenna array are not correlated with each other, which causes difficulties in engineering implementation. Because due to objective conditions, the distance between the transmitting antennas of the CDMA base station may not meet the aforementioned requirements. The existing space-time spread spectrum technology with multiple transmitting antennas requires the mobile station to have multiple antennas, which brings great difficulties to the technical realization of the mobile station, increases the cost of the mobile station, and increases the volume of the mobile station. The receiving despreading algorithm in the aforementioned literature requires a large number of matrix operations, so it is difficult to implement.

The present invention solves the above problems, eliminates multiple access interference in the case of multiple users and multiple paths, and improves the performance of the bit error rate of the system.

Contents of the invention

The purpose of the present invention is to propose a base station transmit diversity circuit of a CDMA system space-time spread spectrum method, which can realize complete diversity without additional bandwidth resources, and each user only needs one spread spectrum code, which is easy to implement. Implementation scheme of the present invention is:

The base station transmitting circuit of the space-time spread spectrum method of the CDMA system, the base station applying the space-time spread spectrum method of the CDMA system proposed by the present invention, the distance between the transmitting antennas need not be greater than the wavelength of the 10-15 transmitted signal. The distance between the transmitting antennas of the base station of the present invention can be in the range of greater than half of the wavelength of the transmitting signal to less than 10-15 times the wavelength of the transmitting signal, and is more suitable for engineering applications. Moreover, the circuit design is simple, and the spreading codes of the odd data stream and the even data stream are obtained by using one spreading code.

The transmitting circuit of the base station applying the CDMA system space-time spread spectrum method that the present invention proposes is: comprise two down-sampling modules, the time-delay module that is connected with a down-sampling module, a plurality of time-delay modules that are connected with down-sampling module or time-delay module respectively The frequency spreader and two adders connected with the frequency spreader, and the two down-sampling modules sample the data flow into two data flows, one of which is delayed by the delay module and then enters the frequency spreader. The delay module adjusts the time difference between the two data streams to make the time difference equal to the time difference between the two data streams when the distance between the two transmitting antennas is 10-15 times the wavelength of the radio frequency signal.

A kind of CDMA system space-time spread spectrum method, this CDMA system comprises at least one base station and a plurality of mobile stations communicating with the base station, it is characterized in that,

The base station obtains the transmission signal according to the following steps:

1) Divide each user's data stream into odd data stream and even data stream

2) Spectrum spreading is performed on the odd data stream and the even data stream respectively to obtain the spread spectrum signal

3) Add the signals after spreading to obtain the transmitted signals t1 and t2

4) Signals t1 and t2 are transmitted by two antennas respectively;

The mobile station obtains the restored data according to the following steps:

5) The receiving circuit of the mobile station despreads the received signal in two ways to obtain the first despread signal and the second despread signal

6) The receiving circuit of the mobile station performs channel parameter weighting on the first and second despread signals to obtain a combined signal of the first and second despread signals

7) The receiving circuit of the mobile station judges the combined signal of the first and second despread signals respectively, and then obtains the restored data.

，“H”表示复共轭转置，而且是由同一个扩谱码得到的。The space-time spread spectrum method of the CDMA system is characterized in that, in step 2), the spread spectrum codes c1 and c2 used for the odd data stream and the even data stream are mutually orthogonal,

, "H" represents the complex conjugate transpose, and is obtained by the same spreading code.

The space-time spread spectrum method of the CDMA system is characterized in that the spread spectrum codes c1 and c2 used for spreading the odd data flow and the even data flow are obtained from the spread spectrum code c0, and c0 is a Walsh code sequence with a finite length of 64.

The space-time spread spectrum method of the CDMA system is characterized in that step 1) and step 2) also include a step: the base station transmit diversity circuit adjusts the time difference between the even data flow and the odd data flow, so that the time difference is equal to two transmissions The time difference between odd and even data streams when the distance between the antennas is 10-15 times the wavelength of the radio frequency signal.

The space-time spread spectrum method of the CDMA system is characterized in that, in step 7), the method for the receiving circuit judgment of the mobile station is: the judging device (341) of the receiving circuit of the mobile station combines and judges the first despreading signal The calculation method is:

If the real part of the decision device (341) input signal is greater than zero, then output 1,

If the real part of the decision device input (341) input signal is less than zero, then output-1,

The judging device (342) of the receiving circuit of the mobile station merges the signal after the second despreading and the method for judging calculation is:

If the real part of the decision device (342) input signal is greater than zero, then output 1,

If the real part of the input signal to the decider (342) is less than zero, -1 is output.

The space-time spread spectrum method of the CDMA system is characterized in that step 7) further includes: the receiving circuit of the mobile station delays the judgment result of combining and summing the first despreading signal, and then combines with the second despreading signal Merge and merge the judgment results to obtain the restored data.

The space-time spread spectrum method of the CDMA system is characterized in that, step 6) comprises the channel parameters h1 and h2 of the two antenna transmission signals of the CDMA base station estimated by the receiving circuit of the mobile station, and respectively with the first despreading signal d1 and The second despread signal d2 is multiplied to obtain d1h1 and d2h2; d1h1 and d2h2 are added in reverse, and then a judgment is made, and d2h2 and d1h1 are added in reverse, and then a judgment is made.

Another object of the present invention is to propose a mobile station receiving circuit applying the space-time spread spectrum method of the CDMA system. The mobile station of the present invention uses an omnidirectional antenna and two-way matching filter to restore the parity data stream, realizes the space-time spread spectrum method of the present invention, reduces the volume of the mobile station and saves the cost. The mobile station of the invention does not need to perform complex matrix operations, can directly combine and judge even and odd data streams, and has simple circuit design. The mobile station receiving circuit of the present invention uses delay spread spectrum series C1 and C2 to despread and channel parameters h1 and h2 to weight, which can suppress MAI (multiple access interference) in the case of multiple users.

The implementation scheme of the mobile station receiving circuit of the application CDMA system space-time spread spectrum method of the present invention is: the receiving circuit of the mobile station comprises two matched filters connected in parallel, input receiving signals respectively, and two multipliers are respectively connected with two matched filters , the two adders are respectively connected to the multipliers, and the decision unit is respectively connected to the two adders, wherein the input of each adder is the inversion of the output of one multiplier and the output of the other multiplier.

The base station of the present invention only needs to use two double omnidirectional antennas, and the mobile station uses a single omnidirectional antenna. The base station adopts the present invention to perform transmit diversity on multi-user data streams in the baseband, and the single-antenna mobile station adopts the present invention to receive data to obtain diversity gain, which significantly improves the information transmission quality of the wireless communication system as a whole. Moreover, the present invention can eliminate multiple access interference to a certain extent in the case of multi-user and multi-path, and improve the performance of the bit error rate of the system.

Description of drawings

The present invention will be described in detail below through the accompanying drawings and embodiments.

Fig. 1 is a circuit diagram of the transmit diversity of the base station of the present invention.

FIG. 2 is a flow chart of the base station in FIG. 1 applying the space-time spread spectrum method for the CDMA system of the present invention.

Fig. 3 is a schematic diagram of the circuit of the mobile station receiver of the present invention.

Fig. 4 is a flow chart of the mobile station in Fig. 3 applying the CDMA system space-time spread spectrum method of the present invention.

Fig. 5 is a comparison graph of bit error rates of mobile stations in a system applying a single transmitting antenna base station and a system applying the base station of the present invention when a single user is used.

Fig. 6(a) and (b) are graphs comparing bit error performance of the system using the method of the present invention and the system not using the method of the present invention when there are 4 and 16 users respectively.

Detailed ways

Referring to Fig. 1, the present invention is a space-time spread spectrum method for downlink of CDMA system. The system of the present invention includes a base station and a plurality of mobile stations. The base station has two antennas, and each mobile station has only one antenna. The base station performs transmit diversity on the multi-user data flow b at the baseband, and its transmit diversity circuit includes down-sampling modules 111 and 112, a delay module 122, spreaders (multipliers) 131, 132, 133, 134, and adders 141 and 142 .

Combined with Figure 2, the steps of the base station baseband processing are:

1) Step 21: Divide each user's data stream into odd data stream and even data stream

The data stream b of each user is divided into two paths, and the odd data stream b1 and the even data stream b2 are obtained through the down-sampling modules 111 and 112 . Data stream b is BPSK modulated.

2) Step 22: Adjust the time difference between the even data stream and the odd data stream

The delay module 122 adjusts the time difference between the even data stream b2 and the odd data stream. The time difference between the adjusted odd and even data streams equals the time difference between the two transmitting antennas when the distance between the two transmitting antennas is 10-15 times of the radio frequency signal wavelength. Therefore, if the base station of the present invention is used, the distance between the two antennas on the base station does not require It must be 10-15 times the wavelength of the radio frequency signal, but the time difference between the odd and even data streams is changed through the delay module 122 to ensure the irrelevance of the signals received by the mobile station. The transmit diversity circuit of the base station of the present invention provides time diversity by adjusting the time difference between the odd data flow and the even data flow through the delay module 122 . However, the multipath channel correlation between the two antennas of the base station and the mobile station is very small, and at this time, the correlation between the delay spreading code of the odd data stream of a single user and the delay spreading code of its even data stream is very small . Therefore, the distance between the two antennas of the base station needs to be greater than half of the wavelength of the radio frequency signal.

If the distance between the two transmitting antennas of the base station is greater than 10-15 times the wavelength of the radio frequency signal, then the delay value of the delay module is set to zero. Therefore, in this case, the baseband circuit of the present invention is still applicable.

3) Step 23: Spectrum spreading is performed on the odd data stream and the even data stream respectively to obtain the spread spectrum signal

The odd data stream output by the down-sampling module 111 is mixed with the spreading code c1 in the multiplier 131 to obtain the spread signal b1c1, and mixed with the spreading code c2 in the multiplier 134 to obtain the spread signal b1c2.

“H”表示复共轭转置。Here, the spread spectrum codes c1 and c2 are orthogonal spread spectrum codes with a length of 2P, which are unit real vectors, and,

"H" indicates complex conjugate transpose.

For the convenience of calculation, in the present invention, the spreading codes c1 and c2 are calculated by a 64-bit Walsh code sequence c0: c ₁ =[c ₀ c ₀ ] c ₂ =[c ₀ -c ₀ ]

条件的正交扩谱码c1、c2就可以实现本发明。Another set of c1 and c2 is c ₁ =[c ₀ 0], c ₂ =[0 c ₀ ]. The above two groups of c1 and c2 are obtained through the same Walsh code sequence c0, so the number of existing spreading codes of the system may not be increased. understandable, as long as

The conditional orthogonal spread spectrum codes c1 and c2 can realize the present invention.

The even data output by the down-sampling module 112 flows through the delay circuit 122 and is spread by the spreading code c2 in the multiplier 132 to obtain the spread signal b2c2, which is spread by the multiplier 133 and the spreading code c1 to obtain the spread signal b2c1.

4) Step 24: Add the spread spectrum signals to obtain the transmitted signals t1 and t2

The input of the adder 141 is: the spread signal b1c1 obtained by multiplying the odd data stream by the spreading code c1 and the spread signal b2c2 obtained by multiplying the even data stream by the spreading code c2. The adder 141 outputs the baseband transmission signal t1, which is transmitted by the first antenna (not shown) through the radio frequency module (not shown).

Similarly, the spread signal b2c1 obtained by mixing the even data stream with the spreading code c1 and the spread signal b1c2 obtained by mixing the odd data stream with the spreading code c2 are added in the adder 142 to obtain the baseband transmission signal t2, It is transmitted by the second antenna (not shown) through the radio frequency module (not shown).

t ₁ =b ₁ c ₁ +b ₂ c ₂ (Formula 1)

t ₂ =b ₂ c ₁ -b ₁ c ₂

5) Step 25: transmit signals t1 and t2 respectively by two antennas

It can be understood that the present invention can also use multiple antennas for transmission.

The above is the processing flow in the baseband circuit of the base station. The processing of the received signal by the receiver circuit of the mobile station will be introduced below in conjunction with Figs. 3 and 4 . Under multipath fading, it is assumed that the channel from the base station transmit antenna to the mobile station receive antenna contains J different paths. Here, J paths from the mth antenna element of the base station go through independent Rayleigh fading, represented by channel parameters h _mj (m=1, 2, j=1, 2...J). Specifically, the channel fading of the signal transmitted by the first antenna is represented by the channel parameter h _1j ; the channel fading of the signal transmitted by the second antenna is represented by the channel parameter h _2j . The mobile station can estimate channel attenuation and multipath delay according to the downlink pilot signal sent by the base station. Under the best receiving condition, each component of the signal transmitted by the base station has the same expected power and the delay-spreading codes are completely orthogonal.

Mobile station receiver circuit comprises two matched filters 311,312, two multipliers 321,322 connected with a matched filter respectively, adders 331,332 connected with two multipliers, connected with an adder respectively The decision units 341 and 342, the delay unit 351 connected to the decision unit, and the interpolation and combining module 361 are connected to the decision unit and the delay unit.

After the transmitted signals t ₁ and t ₂ sent from the first and second antennas undergo multipath fading h ₁ and h ₂ respectively, the signals obtained at the receiving end of the mobile station are

$r=\sqrt{\mathrm{\ρ}}(\underset{j=1}{\overset{J}{\mathrm{\Σ}}}{h}_{1j}(b_1{c}_{1j}+b_2{c}_{2j})+\underset{j=1}{\overset{J}{\mathrm{\Σ}}}{h}_{2j}(b_2{c}_{1j}-b_1{c}_{2j}))+\mathrm{no}$ (Formula 2)

$<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="b"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">b</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="h"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="b"\; filenames="HSB00000764563600031.png,HSB00000764563600033.png"\; state="\{\{state\}\}">b</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}$

Among them, C ₁ =[c _l1 ,...,c _lJ ], h _l =[h _l1 ,...,h _lJ ] ^T , l∈{1,2}; assuming that the noise n has a mean of 0 and a variance of N ₀ / 2 Gaussian white noise vector, with ρ representing the expected SNR (signal-to-noise ratio) of each multipath component,

The mobile station receives the received signal r through an antenna (not shown), and performs the following processing:

1) Step 41: Despread the received signal in two ways to obtain the first despread signal and the second despread signal

The received signal r is multiplied by the delayed spread spectrum code C1 in the matched filter 311, and the first despread signal d1 is output. The received signal r is multiplied by the delayed spread spectrum code C2 in the matched filter 312, and the second despread signal d2 is output. Wherein, the delay-spread codes C1 and C2 are respectively input to the matched filters 311 and 312 by a delay-spread code generating unit (not shown). The mobile station estimates the multipath delay according to the downlink pilot signal sent by the base station, and calculates the delay spreading code. The first despread signal d1 and the second despread signal d2 are respectively:

${\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">d</figure-callout>}}_1=C_1^{h}r=\sqrt{\mathrm{\&rho;}}[R_{11}{h}_1-R_{12}{h}_2]{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+\sqrt{\mathrm{\&rho;}}[R_{12}{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">h</figure-callout>}}_1+R_{11}{h}_2]{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSB00000764563600031.png,HSB00000764563600033.png"\; state="\{\{state\}\}">b</figure-callout>}}_2+C_1^h\mathrm{no}$ (Formula 3)

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="d"\; filenames="HSB00000764563600031.png,HSB00000764563600033.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="b"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">b</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="h"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="b"\; filenames="HSB00000764563600031.png,HSB00000764563600033.png"\; state="\{\{state\}\}">b</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; no</span>}$

i＝1或2，j＝1或2。here

i=1 or 2, j=1 or 2.

2) Step 42: Carrying out channel parameter weighting to the first and second despread signals respectively to obtain the combined sum of the first and second despread signals

The first despread signal d1 is multiplied by the channel parameter vector h1 in the multiplier 321, and then input to the adder 331; the product of the first despread signal d1 and the channel parameter vector h1 is input to the adder after inversion 332.

Similarly, the second despread signal d2 is multiplied by the channel parameter vector h2 in the multiplier 322, and then input to the adder 333; the product of the second despread signal d2 and the channel parameter vector h2 is input after inversion to adder 331.

In the adder 331, the inversion (-d2h2) of the product of the second despread signal d2 and the channel parameter vector h2 is added to the product (d1h1) of the first despread signal d1 and the channel parameter vector h1, and its output is The input of decider 341. In the adder 332, the product (d2h2) of the second despread signal d2 and the channel parameter matrix h2 is added to the inversion (-d1h1) of the product of the first despread signal d1 and the channel parameter vector h1, and then input to the decision The device 342 makes a decision. It should be noted that the mobile station of the present invention uses a maximum ratio combiner. The mobile station has a channel parameter generating unit (not shown) to estimate channel attenuation according to the downlink pilot signal sent by the base station, calculate the channel parameter, and input the corresponding multiplier. Wherein, channel parameter vector h ₁ =[h ₁₁ ,…,h _1J ] ^T , h ₂ =[h ₂₁ ,…,h _2J ] ^T

3) Step 43: combining and separately judging the first and second despread signals to obtain the restored signal

The restored data b1 and data stream b2 are obtained through the judgment of the decision units 341 and 342 . The method for the judgment calculation of decision unit 341 is:

If the real part of the decision device input signal is greater than zero, then b1 is equal to 1, expressed by (Equation 4a):

$\mathrm{Re}{\{h_1^h{d}_1-h_2^h{d}_2\}}^{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">b</figure-callout>}}_1=1}>0$ (Formula 4a)

If the real part of the decision device input signal is less than zero, then whether b1 is equal to -1, expressed by (Formula 4b):

$\mathrm{Re}{\{h_1^h{d}_1-h_2^h{d}_2\}}^{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">b</figure-callout>}}_1=-1}<0$ (Formula 4b)

The method for the judgment calculation of decision unit 342 is:

If the real part of the decision device input signal is greater than zero, then b2 is equal to 1, expressed by (Equation 4c):

$\mathrm{Re}{\{h_2^{\mathrm{<figure-callout\; id="1"\; label="h\; d"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">h</figure-callout>}}{d}_{}{}_1+h_1^h{d}_2\}}^{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSB00000764563600031.png,HSB00000764563600033.png"\; state="\{\{state\}\}">b</figure-callout>}}_2=1}>0$ (Formula 4c)

If the real part of the input signal of the decision device is less than zero, then b2 is equal to -1, expressed by (Equation 4d):

$\mathrm{Re}{\{h_2^{\mathrm{<figure-callout\; id="1"\; label="h\; d"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">h</figure-callout>}}{d}_{}{}_1+h_1^h{d}_2\}}^{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSB00000764563600031.png,HSB00000764563600033.png"\; state="\{\{state\}\}">b</figure-callout>}}_2=-1}<0$ (Formula 4d)

It can be seen that the mobile station of the present invention directly combines and judges the combination of the first despread signal and the second despread signal without complex matrix calculations, thereby simplifying circuit design and reducing the amount of calculation.

Step 44: Delay the restored odd data stream, and then combine with the restored even data stream to form restored data stream b.

The determined restored odd data stream b1 is sent to the interpolation and merging module 36 via the delay circuit 35 and the restored even data stream b2. The interpolation and merging module 36 alternately interpolates the parity data streams b1 and b2 to restore the data stream b. The delay circuit 35 in FIG. 3 is the same as the delay circuit 12 in the transmitter circuit, and takes the same delay parameters.

In order to illustrate the effect of the method of the present invention, simulation data are presented here.

移动台用户的比特误码率表达式为Further theoretical derivation can prove that: when the correlation between the delay spreading code of the odd data stream of a single user and the delay spreading code of its even data stream is small, R _ij ≈ 0, i≠j, i=1 Or 2, j=1 or 2, or the correlation between the multipath channel h ₁ from the base station antenna 1 to the mobile station and the multipath channel h 2 from the base station antenna ₂ to the mobile station is very small,

The bit error rate expression of the mobile station user is

$P_e\&ap;Q\left(\sqrt{\mathrm{\&rho;}(h_1^h{R}_{11}{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="HSB00000764563600011.png"\; state="\{\{state\}\}">h</figure-callout>}}_1+h_2^h{R}_{\mathrm{twenty\; two}}{h}_2)}\right)$ (Formula 5)

The bit error rate in Figure 5 is obtained by theoretical calculation formula 5 and Monte Carlo simulation respectively. Compared with the single-antenna design scheme without STS technology, it can be seen that the STS scheme improves the bit error rate performance of the system. The curves represented by the solid line and the dotted line in FIG. 5 are the relationship curves between the expected SNR and the bit error rate obtained by simulation when the number of transmitting antennas of the base station is M=1 and 2 respectively under multipath conditions. When the bit error rate is 10 ^-2 , the SNR of the STS system in the theoretical value and simulation situation is about 4dB higher than that of the single-antenna system. Here, the spread spectrum codes c ₁ and c ₂ used are orthogonal Walsh codes with a length of 128. Due to the existence of multipath, their forms after channel delay are C ₁ =[c ₁₁ c ₁₂ ], C ₂ =[ c ₂₁ c ₂₂ ], the delay takes 10 codewords.

In the foregoing introduction, only the case of a single-user system is involved. In practice, however, the system is multi-user. Due to the existence of inter-user symbol interference (ISI), as the number of users increases, its interference effect increases, resulting in a significant decline in system performance.

Next, we will study the situation when the system has K users, and its design principle and operating environment are consistent with the previous ones, then the transmission signal of the kth user is

$t_1^{\left(k\right)}=b_1^{\left(k\right)}{c}_1^{\left(k\right)}+b_2^{\left(k\right)}{c}_2^{\left(k\right)}$ (Formula 6)

${\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}$

Under multipath channel (J=2) fading, there are channel parameters

$h^{\left(k\right)}=\left[\begin{array}{c}{h}_1^{\left(k\right)}\\ h_2^{\left(k\right)}\end{array}\right]$ (Formula 7)

Similar to formula 2, the kth user receives the signal transmitted to it by the base station as

${\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}$

$=\sqrt{\mathrm{\&rho;}}(\underset{j=1}{\overset{J}{\mathrm{\&Sigma;}}}{h}_{1j}^{\left(k\right)}(b_1^{\left(k\right)}{c}_{1j}^{\left(k\right)}+b_2^{\left(k\right)}{c}_{2j}^{\left(k\right)})+\underset{j=1}{\overset{J}{\mathrm{\&Sigma;}}}{h}_{2j}^{\left(k\right)}(b_2^{\left(k\right)}{c}_{1j}^{\left(k\right)}-b_1^{\left(k\right)}{c}_{2j}^{\left(k\right)}))+{\mathrm{no}}^{\left(k\right)}$ (Formula 8)

$<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</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">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</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">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</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">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</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">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}$

The symbols in formula (8) are consistent with formula (2). Then the total received signal at the receiver is

$r=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{r}^{\left(k\right)}$ (K is the total number of users) (Formula 9)

Similarly, the despread signal is

$d_1^{\left(k\right)}={\left(C_1^{\left(k\right)}\right)}^{h}r={\left(C_1^{\left(k\right)}\right)}^h\&CenterDot;\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{r}^{\left(k\right)}={\left(C_1^{\left(k\right)}\right)}^h{r}^{\left(k\right)}+\underset{m\&NotEqual;k}{\overset{K}{\underset{m=1}{\mathrm{\&Sigma;}}}}{\left(C_1^{\left(k\right)}\right)}^h\&Center\; Dot;r^{\left(m\right)}$ (Formula 10a)

$d_2^{\left(k\right)}={\left(C_2^{\left(k\right)}\right)}^{h}r={\left(C_2^{\left(k\right)}\right)}^h\&Center\; Dot;\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{r}^{\left(k\right)}={\left(C_2^{\left(k\right)}\right)}^h{r}^{\left(k\right)}+\underset{m\&NotEqual;k}{\overset{K}{\underset{m=1}{\mathrm{\&Sigma;}}}}{\left(C_2^{\left(k\right)}\right)}^h\&CenterDot;r^{\left(m\right)}$ (Formula 10b)

The restored data flow is

${<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}$

$<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; r</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>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&NotEqual;</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}}}<span\; class="notranslate">\; )</span>$

$={\left(h_2^{\left(k\right)}\right)}^h{\left(C_2^{\left(k\right)}\right)}^h{r}^{\left(k\right)}-\left({\left(h_2^{\left(k\right)}\right)}^h{\left(C_2^{\left(k\right)}\right)}^h\underset{m\&NotEqual;k}{\overset{K}{\underset{m=1}{\mathrm{\&Sigma;}}{r}^{\left(m\right)}}}\right)$ (Formula 11a)

${<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}$

$<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; r</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>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&NotEqual;</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

$+{\left(h_1^{\left(k\right)}\right)}^h{\left(C_2^{\left(k\right)}\right)}^h{r}^{\left(k\right)}+\left({\left(h_1^{\left(k\right)}\right)}^h{\left(C_2^{\left(k\right)}\right)}^h\underset{m\&NotEqual;k}{\overset{K}{\underset{m=1}{\mathrm{\&Sigma;}}}}{r}^{\left(m\right)}\right)$ (Formula 11b)

部分是多用户比单用户情况多出来的部分，即得基站两天线至移动台k的多址干扰(MAI)From formula (11), it can be seen that,

Part of it is the part where multi-user is more than that of single-user, that is, the multiple access interference (MAI) from the two antennas of the base station to the mobile station k

$\mathrm{<span\; class="notranslate">\; MA</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&NotEqual;</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{MA}{I}_2^{\left(k\right)}={\left(h_2^{\left(k\right)}\right)}^h\left(C_2^{\left(k\right)}\right)\underset{m\&NotEqual;k}{\overset{K}{\underset{m=1}{\mathrm{\&Sigma;}}}}\left(C_2^{\left(m\right)}\right)\left(h_2^{\left(m\right)}\right)$ (Formula 12)

Thus, the total multiple access interference (MAI) is

${\mathrm{MAI}}^{\left(k\right)}={\mathrm{MAI}}_1^{\left(k\right)}+{\mathrm{MAI}}_2^{\left(k\right)}$ (Formula 13)

In the receiving circuit of the mobile station of the present invention, spread spectrum sequences C1 and C2 are used for despreading, h1 and h2 are weighted, and the decision unit adopts the method (formula 4) to make a decision, so as to realize the suppression of MAI.

When there are many users, the present invention greatly improves the bit error rate of the system.

When the system of the present invention has multiple users with dual transmitting antennas, the bit error rate of the kth mobile user

$P_{e2}^{\left(k\right)}=Q\left(\sqrt{\frac{{\left(h_1^{\left(k\right)}\right)}^h{R}_{11}^{\left(k\right)}{h}_1^{\left(k\right)}+{\left(h_2^{\left(k\right)}\right)}^h{R}_{\mathrm{twenty\; two}}^{\left(k\right)}{h}_2^{\left(k\right)}}{K/\mathrm{\&rho;}+{\mathrm{MAI}}^{\left(k\right)}}}\right)$ (Formula 14)

In formula 14, when K=1, then transform into formula 14. So the dual transmit antenna single user of Equation 5 is just a special case of Equation 14.

The bit error rate of the kth mobile user when the system of the present invention is not adopted when there are multiple users on a single transmitting antenna

$P_{e1}^{\left(k\right)}=Q\left(\sqrt{\frac{{\left(h^{\left(k\right)}\right)}^h{R}_{11}^{\left(k\right)}{h}^{\left(k\right)}}{K/\mathrm{\&rho;}+{\left(h^{\left(k\right)}\right)}^h\left(C^{\left(k\right)}\right)\underset{m\&NotEqual;k}{\overset{K}{\underset{m=1}{\mathrm{\&Sigma;}}}}\left(C^{\left(m\right)}\right)\left(h^{\left(m\right)}\right)}}\right)$ (Formula 15)

随移动台的空间位置的改变而发生变化，这需要移动台通过信道估计来确定C_i，C_j，进而确定R_ij。In the above formula, the correlation matrix

It changes with the change of the spatial position of the mobile station, which requires the mobile station to determine C _i , C _j through channel estimation, and then determine R _ij .

In order to verify the effectiveness of the technology of the present invention, adopt theoretical calculation (according to formula (14) and (15)) and link simulation (Monte Carlo simulation: base station sends data 10 ⁵ bits, measures the bit error rate of mobile station receiving data) , and compare it with the performance of a single-antenna system that does not employ the present invention. The simulation of the present invention does not add channel error correction codec. The spread spectrum codes c ₁ and c ₂ used are orthogonal Walsh codes with a length of 64. Considering the situation of two multipaths, the form of c ₁ and c ₂ after channel delay is C ₁ =[c ₁₁ c ₁₂ ], C ₂ = [c ₂₁ c ₂₂ ], the delay takes 10 codewords. The channel attenuation is random: the channel attenuation matrix when simulating 16 users is as follows

h11(1,2,...,16)＝[0.6552 0.8376 0.6284 0.57470.5947 0.5657 0.7165 0.5113 0.7764 0.51070.8141 0.7006 0.9827 0.8066 0.7036 0.5150];

h12(1,2,...,16)＝[0.3448 0.1624 0.3716 0.42530.4053 0.4343 0.2835 0.4887 0.2236 0.48930.1859 0.2994 0.0173 0.1934 0.2964 0.4850];

h21(1,2,...,16)＝[0.8854 0.6649 0.6346 0.86000.5668 0.8230 0.6739 0.9994 0.9616 0.94110.6397 0.5485 0.7382 0.5973 0.9507 0.5711];

h22(1,2,...,16)=[0.1146 0.3351 0.3654 0.14000.4332 0.1770 0.3261 0.0006 0.0384 0.05890.3603 0.4515 0.2618 0.4027 0.0493 0.4289].

(1) The system has 4 users

In Figure 6(a), the solid line represents the variation of the theoretical bit error rate of the STS system with the expected SNR, and the curve where the asterisk is located is the variation of the simulated bit error rate of the STS system with the expected SNR; the dotted line indicates the variation of the single-antenna system The theoretical bit error rate varies with the expected SNR, and the curve where the circle is located is the variation of the simulated bit error rate. It can be seen that when the bit error rate is 10 ⁻² , the SNR of the system using the present invention is increased by about 7.6 dB in both theoretical and simulated values compared with the system SNR not using this technology. During the simulation process, the generated noise is random, and the restoration and judgment of the signal will cause errors between the theoretical value and the simulated value, so the bit error performance of the simulated STS is worse than its theoretical bit error performance.

(2) The system has 16 users

Figure 6(b) shows the bit error performance of the system when there are 16 users. It is easy to see that when the SNR is greater than 8dB, the bit error rate of the system adopting the technology of the present invention decreases rapidly, while the theoretical value and simulation value of the bit error rate of the system not using this technology remain at about 20%.

At the same time, it can also be seen that the bit error performance of 16 users is worse than that of 4 users. This is because in the case of channel correlation, the increase of the number of users increases the influence of multiple access interference, resulting in a poor bit error performance. dropped. As the proportion of inter-symbol interference between users in the received signal increases, the bit error performance of the system that does not adopt the method of this aspect is no longer acceptable, while the bit error performance of the system that adopts the technology of the present invention is still working normally range, but the SNR of the system is required to be greater than 14dB.

Through the comparison of the effect diagrams, it is shown that the technology of the present invention is an effective technology, which improves the bit error rate performance of the system to a certain extent.

Although the present invention has been described above through the embodiments, those skilled in the art know that the present invention has many modifications and changes without departing from the spirit of the present invention, and the appended claims will include these modifications and changes.

Claims (5)

1. use the base station radiating circuit of cdma system space-time spectrum extending method, it is characterized in that, comprise two lower decimation blocks, the time delay module that is connected with a lower decimation blocks, a plurality of frequency multipliers that are connected with lower decimation blocks or time delay module respectively and two adders that are connected with frequency multiplier, two lower decimation blocks are sampled to two data flow with data flow, wherein a data flow enters frequency multiplier after the time delay module time-delay, another data flow directly enters frequency multiplier, the addition of frequency multiplier output signal, t1, t2 obtain transmitting.

2. the base station radiating circuit of cdma system space-time spectrum extending method as claimed in claim 1, it is characterized in that, time delay module is adjusted the time difference between two data flow, the time difference of two data flow when to make this time difference equal two transmitting antenna spacings be 10-15 times of radiofrequency signal wavelength.

3. the base station radiating circuit of cdma system space-time spectrum extending method as claimed in claim 1 is characterized in that, one group of quadrature spread-spectrum codes c1, c2 that frequency multiplier uses obtain c by a Walsh code sequence c0 ₁=[c ₀c ₀], c ₂=[c ₀-c ₀], other one group of quadrature spread-spectrum codes c1, c2 are c ₁=[c ₀0], c ₂=[0 c ₀].

4. the base station radiating circuit of cdma system space-time spectrum extending method as claimed in claim 1 is characterized in that, frequency multiplier uses quadrature spread-spectrum codes c1, c2 respectively to two data flow spread spectrums.

5. frequency multiplier uses quadrature spread-spectrum codes c1, c2 respectively to two data flow spread spectrums as claimed in claim 4, the even data that it is characterized in that 112 outputs of lower decimation blocks flow through delay circuit 122 at multiplier 132 by spread-spectrum codes c2 spread spectrum, obtain signal b2c2 behind the spread spectrum, at multiplier 133 and spread-spectrum codes c1 spread spectrum, obtain signal b2c1 behind the spread spectrum, with signal plus behind the spread spectrum, t1, t2 obtain transmitting.

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