CN1194492C - Multi-user Detection Method of Base Station in Code Division Multiple Access Mobile Communication System - Google Patents

Abstract

The multi-user detection method of the base station in the code division multiple access mobile communication system of the present invention, adopts the method for segmental hard judgment to realize, comprises the following steps: rake (RAKE) receiver carries out multipath despreading to input signal; By despreading result Carry out channel estimation, then carry out multi-path combination, send the combined result of each bit to the hard decision device and the threshold calculation device at the same time, and send the channel estimation result to the signal regenerator; A threshold is obtained by calculating the path combination result, and the threshold is sent to the hard decision device of each user; the hard decision device makes a hard decision on the multipath combination result of the bits of the corresponding serial number according to the threshold, and sends the decision result to the signal regenerator ; The signal regenerator obtains the user's regenerated signal by the decision result and the channel estimation result, and sends the regenerated signal to the estimation of multiple access interference and the interference cancellation device; the estimation of multiple access interference and the interference cancellation device are input by each user The multiple access interference of each user is calculated from the regenerated signal; the signal obtained by eliminating the multiple access interference of a certain user from the baseband signal of the received signal is used as the input signal of the user's rake receiver in the next-level parallel interference cancellation structure; Repeating the above steps until the number of repetitions is equal to the set number of stages of multi-level parallel interference cancellation, the multi-level interference cancellation is realized; the feature is that the hard decision is segmented hard decision. Improved performance of multiuser detection technology.

Description

Multi-user detection method for base station in CDMA mobile communication system

Technical Field

The present invention relates to a communication system, and more particularly, to a multi-user detection method of a base station in a code division multiple access (WCDMA and CDMA2000) cellular mobile communication system.

Technical Field

The multi-user detection technique is an enhanced technique for overcoming the influence of multiple access interference and improving the capacity of a Code Division Multiple Access (CDMA) system. The method can make full use of the information of a plurality of users to carry out joint detection on the signals of the plurality of users, thereby reducing the influence of multiple access interference on the performance of a receiver as much as possible and improving the capacity of a system.

Verdu published an article on a maximum likelihood sequence detector in the United states of America "IEEE Transactions on Information Theory", in 1986. This detector is an optimal multi-user detector but it is highly complex and requires an estimate of the received signal amplitude and phase information, which makes the maximum likelihood sequence detector difficult to apply.

Sub-optimal multi-user detection methods are roughly divided into two categories: a linear detection method and an interference cancellation method. The linear detection method performs a linear transformation on the soft output of the single-user detector to produce a set of new outputs that improve performance. The linear detection method has good performance, but the calculation is complex. The interference cancellation method estimates the multiple access interference of the desired user through the regenerated signals of other users, cancels the multiple access interference suffered by the desired user from the received signals, and then detects the signals with the interference removed, thereby improving the performance of the system.

The current interference cancellation method can be divided into: serial Interference Cancellation (Serial Interference Cancellation) and Parallel Interference Cancellation (Parallel Interference Cancellation). The serial interference cancellation method performs better than the single-user detector. But this method is time-delayed; power sequencing is required, and the calculated amount is large; sensitive to initial signal estimation. The performance of the parallel interference cancellation method is superior to that of a single-user detector, the time delay is small, the calculation complexity is small, and the method is the most promising and practical method at present.

In the conventional parallel interference cancellation method, the performance of the parallel interference cancellation method is reduced due to an erroneous hard decision result. Aiming at the defects of the traditional parallel interference cancellation method, the zero-domain hard-decision parallel interference cancellation method uses a threshold value to measure the reliability of a multipath combining result of a RAKE receiver, and determines whether corresponding bits participate in interference cancellation or not according to the measuring result. When the absolute value of the RAKE combination result is larger than or equal to the threshold value, the RAKE combination result is considered to be reliable, and the corresponding bit is judged to be +1 or-1, so that the bit participates in interference cancellation; when the absolute value of the RAKE combination result is less than the threshold value, the RAKE combination result is considered to be unreliable, and the corresponding bit is judged to be 0, so that the bit does not participate in interference cancellation. Thus, the problem that the performance of the parallel interference cancellation method is reduced by wrong judgment results is avoided. In the following, a zero-field hard-decision parallel interference cancellation method is described in detail.

The multi-stage structure of the zero-domain hard-decision parallel interference cancellation method is shown in fig. 1. The first stage Parallel Interference Cancellation (PIC) device structure 11 takes the baseband signal of the received signal as the input signal of each user, and processes the input signal, and the obtained output signal of each user is the input signal of each user in the next stage PIC structure; the second-level PIC structure processes input signals of all users, and the obtained output signals of all users are the input signals of all users in the next-level PIC structure; thus, the final stage of PIC structure 12 processes the input signals of each user, and the output signals of each user are the final results of the multi-stage PIC structure.

Fig. 2 is a block diagram of a Parallel Interference Cancellation (PIC) device of fig. 1. The reference numerals in the figures denote: a user signal 1, 2 … K, RAKE receiver 13, a hard decision device 14, a signal regenerator 15, an estimation and interference cancellation device 16 for multiple access interference, a threshold calculation device 17. Each user signal 1, 2 … K output from this stage enters the next stage PIC fabric.

Fig. 3 is a block diagram of the last parallel interference cancellation arrangement of fig. 1. The user signals output from the PIC architecture of the previous stage are input to the RAKE receiver 13 of each user, and the output of this stage is the soft output of each user 1, 2 … K.

In a fading channel environment, the baseband signal of the received signal can be expressed as:

$r\left(t\right)=\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{a}_{\mathrm{il}}{S}_i(t-{\mathrm{\τ}}_{\mathrm{il}})+Z\left(t\right)$

$=\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{a}_{\mathrm{il}}\sqrt{P_i}{b}_i(t-{\mathrm{\τ}}_{\mathrm{il}})c_i(t-{\mathrm{\τ}}_{\mathrm{il}})+Z\left(t\right)----\left(1\right)$

wherein r (t) represents a baseband signal of the received signal; a is_ilThe channel fading value of the ith path of the ith user is represented, and L is the number of paths; tau is_ilThe time delay of the ith path of the ith user is represented; s_i(t) represents a transmission signal of a user i, and K represents the total number of users; p_iRepresents the power of user i; b_i(t) represents the bit stream of user i, $b_i\left(t\right)=\underset{m=-\∞}{\overset{\∞}{\mathrm{\Σ}}}{a}_i^{\left(m\right)}p(t-m{T}_b),$ a_i ^(m)m bit representing the ith user, p (T) representing a period of T_bLet p (T) be a rectangular pulse (when T ∈ [0, T ] without disturbing the conclusion of the method_b]When p (t) is 1; when in use $t\∉[0,T_b]$ When p (t) is 0); c. C_i(t) represents the spreading code of user i; z (t) represents channel noise.

In the kth stage PIC architecture, the input signal to the RAKE receiver for user i is r_i ^(k)(t) of (d). When k is 1, r_i ^(l)(t) r (t). RAKE receiver pair r_i ^(k)(t) performing multipath despreading, performing channel estimation from a despreading result, and then performing multipath combining. RAKE receiver pair for user iThe despreading result of the l path is as follows:

$y_i^{\left(m\right)\left(k\right)}\left(l\right)=\frac{1}{\sqrt{T_b}}\underset{(m-1)T_b+{\mathrm{\τ}}_{\mathrm{il}}}{\overset{m{T}_b+{\mathrm{\τ}}_{\mathrm{il}}}{\∫}}{r}_i^{\left(k\right)}\left(t\right)c_i^{*}(t-{\mathrm{\τ}}_{\mathrm{il}})\mathrm{dt}----\left(2\right)$

wherein, L1.

The multipath combining result of the RAKE receiver is obtained by adopting maximum ratio combining:

$Y_i^{\left(m\right)\left(k\right)}=\mathrm{Re}\left\{y_i^{\left(m\right)\left(k\right)}\right\}----\left(3\right)$

wherein,

$y_i^{\left(m\right)\left(k\right)}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{A}_{\mathrm{il}}^{*}{y}_i^{\left(m\right)\left(k\right)}\left(l\right)----\left(4\right)$

A_ilis thatAn estimate of (d). The specific method of channel estimation is not set forth herein.

Referring to fig. 2, the multipath combining result of the RAKE receiver is simultaneously sent to the hard decision device 14 and the threshold value calculating device 17, which calculates the threshold value from the multipath combining result of the same sequence number bit of all users and sends the threshold value to the hard decision devices of all users simultaneously.

The calculation method of the threshold is the key of the zero-domain hard decision method. The calculation formula of the threshold value is as follows:

${\mathrm{TH}}^{\left(m\right)\left(k\right)}=\frac{1}{K}\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\left\{\right|Y_i^{\left(m\right)\left(k\right)}|-t^{\left(k\right)}{\mathrm{\ξ}}^{\left(m\right)\left(k\right)}\}----\left(5\right)$

wherein,

${\mathrm{\ξ}}^{\left(m\right)\left(k\right)}=\sqrt{\frac{1}{K}\underset{i=1}{\overset{K}{\mathrm{\Σ}}}{\left\{\right|Y_i^{\left(m\right)\left(k\right)}|-\frac{1}{K}\underset{j=1}{\overset{K}{\mathrm{\Σ}}}|Y_j^{\left(m\right)\left(k\right)}\left|\right\}}^2}----\left(6\right)$

t⁽¹⁾＜t⁽²⁾＜...＜t^(S)and S represents the number of stages of the PIC.

The above formula has the following problems:

the threshold value calculated according to the formula (5) may have a negative value, and the nonnegativity of the threshold value is not judged in the formula; the calculation formula is not concise.

The threshold calculation formula is modified, and the threshold is calculated according to the following sequence:

${\mathrm{\μ}}^{\left(m\right)\left(k\right)}=\frac{1}{K}\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\left|Y_i^{\left(m\right)\left(k\right)}\right|----\left(7\right)$

${\mathrm{\σ}}^{\left(m\right)\left(k\right)}=\sqrt{\frac{1}{K}\underset{i=1}{\overset{K}{\mathrm{\Σ}}}{\left\{\right|Y_i^{\left(m\right)\left(k\right)}|-{\mathrm{\μ}}^{\left(m\right)\left(k\right)}\}}^2}----\left(8\right)$

$\mathrm{TEMP}\_{\mathrm{TH}}^{\left(m\right)\left(k\right)}=\frac{1}{K}\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\left|Y_i^{\left(m\right)\left(k\right)}\right|-t^{\left(k\right)}{\mathrm{\σ}}^{\left(m\right)\left(k\right)}----\left(9\right)$

$={\mathrm{\μ}}^{\left(m\right)\left(k\right)}-t^{\left(k\right)}{\mathrm{\σ}}^{\left(m\right)\left(k\right)}$

when TEMP _ TH^(m)(k)When greater than 0, TH^(m)(k)＝TEMP_TH^(m)(k)

When TEMP _ TH^(m)(k)When the temperature is less than or equal to 0, TH^(m)(k)＝0 (10)

The threshold calculation formula has one parameter: t is t^(k). When t is^(k)At an increase, the calculated threshold is smaller, i.e. the threshold used to measure the reliability of the RAKE combining result is lower, so that there is a higher mth ratio for more usersSpecially participate in interference cancellation; when t is^(k)When the number of the m-th bits of the user is reduced, the calculated threshold is larger, that is, the threshold for measuring the reliability of the RAKE combination result is higher, so that the m-th bits of fewer users participate in interference cancellation. Selecting a suitable t^(k)The m-th bit of all reliable users can be made to participate in interference cancellation, and the unreliable users do not participate in interference cancellation.

In particular: when the signal-to-noise ratio is large, the reliability of the RAKE combination result is large, the error rate of hard decision is low, and t can be made^(k)Larger, more users participate in interference cancellation; when the signal-to-noise ratio is small, the reliability of the RAKE combination result is reduced, the error rate of hard decision is higher, and t can be made^(k)And the reliability threshold is raised to make only those users with larger RAKE combination result participate in interference cancellation.

The reliability of the RAKE combination result increases and the error rate of hard decision decreases as the number of stages increases, so that t can be made to be t when the number of stages increases^(k)The value increases.

And the hard decision device of the user carries out hard decision on the RAKE combination result according to the threshold value to obtain the decision result of the kth-level PIC method. The result of the decision on the kth bit of the ith user is:

${\hat{a}}_i^{\left(m\right)\left(k\right)}=\mathrm{nsgn}\left\{Y_i^{\left(m\right)\left(k\right)}\right\}----\left(11\right)$

wherein,

x is an independent variable, TH^(m)(k)> 0 is a threshold.

As can be seen from equations (11, 12), the zero-field hard decision method uses a threshold to measure the reliability of the RAKE combining result. When the absolute value of the RAKE combination result is larger than or equal to the threshold value, the RAKE combination result is reliable, the bit is judged to be +1 or-1, and the bit participates in interference cancellation; when the absolute value of the RAKE combining result is smaller than the threshold, the RAKE combining result is unreliable, the bit is judged to be 0, and the bit does not participate in interference cancellation. This avoids the problem of erroneous decision results degrading the performance of the PIC method.

The functional form of the hard decider 14 is shown in fig. 4. The decision result is further processed, including signal regeneration by the signal regenerator 15, estimation of multiple access interference and interference cancellation by the interference cancellation device 16, to obtain the output signal of user i in the kth level PIC structure. This signal is the input signal to the RAKE receiver for user i in a (k +1) stage PIC architecture. In the kth-level PIC configuration, the reproduced signal of user i can be represented as:

$g_i^{\left(k\right)}\left(t\right)=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{A}_{\mathrm{il}}\underset{n=-\∞}{\overset{\∞}{\mathrm{\Σ}}}{\hat{a}}_i^{\left(n\right)\left(k\right)}p(t-n{T}_b-{\mathrm{\τ}}_{\mathrm{il}})c_i(t-{\mathrm{\τ}}_{\mathrm{il}})----\left(13\right)$

from the regenerated signals of the other (K-1) users, an estimate of the Multiple Access Interference (MAI) of user i can be obtained:

${\hat{I}}_i^{\left(k\right)}=\underset{j=\mathrm{lj}\≠i}{\overset{K}{\mathrm{\Σ}}}{g}_j^{\left(k\right)}\left(t\right)$

for the ith user, the MAI generated by other users is eliminated from the received signal according to the following formula:

$r_i^{(k+1)}\left(t\right)=r\left(t\right)-{\hat{I}}_i^{\left(k\right)}----\left(15\right)$

r_i ^(k+1)(t) isThe output signal of user i in a k-level PIC configuration. This signal is the input signal to the RAKE receiver of user i in the (k +1) th stage PIC architecture.

In the last stage PIC architecture of the S-stage PIC method (see FIG. 3), the RAKE receiver of user i is coupled to the input signal r_i ^(S)And (t) carrying out multipath despreading, channel estimation and multipath combination, wherein the soft output of the user i obtained by multipath combination is the final result of the user i in the S-level PIC method. The result is sent to the decoder of user i for decoding. The final stage PIC architecture does not include signal regeneration and multiple access interference estimation and interference cancellation means.

The zero-domain hard decision method divides the RAKE combining result into two categories according to the threshold value: reliable and unreliable. When the RAKE combination result is reliable, the corresponding bit participates in the interference cancellation; when the results of the RAKE combining are unreliable, the corresponding bits do not participate in interference cancellation. In different levels of PIC structures, the zero field hard decision method processes the RAKE combining results in the same way.

In fact, the reliability of the RAKE combining results is not the same in the PIC structures of different stages. In the first-stage PIC structure, the reliability of the RAKE combination result is the worst; in the second-level PIC structure, due to the interference cancellation effect in the first-level PIC structure, the reliability of the RAKE combination result in the second-level PIC structure is enhanced; also, interference cancellation in the second stage PIC architecture further enhances the reliability of the RAKE combining results in the third stage PIC architecture. Thus, as the number of stages increases, the reliability of the RAKE combining result increases. Therefore, in different levels of PIC structures, it is not reasonable for the zero-field hard decision method to use exactly the same processing mode for the RAKE combining result: in each level of PIC structure, reliable users are judged to completely participate in interference cancellation, and unreliable users are judged not to participate in interference cancellation.

Although the zero-field hard decision method effectively improves the performance of the traditional parallel interference cancellation method under a lower signal-to-noise ratio, the improvement amplitude is limited.

Disclosure of Invention

The invention aims to overcome the defects of a zero-field hard decision method in the existing multi-user detection technology, and provides a segmented hard decision parallel interference cancellation method, so that the performance of the multi-user detection technology is improved.

In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows: a multi-user detection method of base station in CDMA mobile communication system is characterized in that it is realized by using segmented hard decision method, including the following steps:

a. the rake receiver performs multipath despreading on the input signal;

b. the de-spread result is used for channel estimation, then multipath combination is carried out, the multipath combination result is simultaneously sent to a hard decision device and a threshold value calculation device, and the channel estimation result is sent to a signal regenerator;

c. the threshold value calculating device calculates a threshold value according to the multipath merging result of the bits with the same serial number of all users, and sends the threshold value to the hard decision device of each user;

d. the user's hard decision device makes hard decision to the multipath merging result of the bit of the corresponding serial number according to the threshold value, and sends the decision result to the signal regenerator;

e. the signal regenerator obtains the regenerated signal of the user according to the judgment result and the channel estimation result, and sends the regenerated signal to the multiple access interference estimation and interference cancellation device;

f. the estimation and interference cancellation device of the multiple access interference calculates the multiple access interference of each user according to the input regeneration signal of each user; the signal obtained by eliminating the multiple access interference of a certain user from the baseband signal of the received signal is used as the input signal of the rake receiver of the user in the next stage of parallel interference cancellation structure;

g. repeating the steps a-f until the repetition times are equal to the set number of the multistage parallel interference cancellation, and realizing the multistage interference cancellation;

the hard decision in step d is a segment hard decision, the decision device makes a decision on the multipath combination result segment of the bit with the corresponding sequence number according to the threshold value, and when the rake combination result of the bit is equal to 0, the hard decision of the corresponding bit is 0; when the absolute value of the rake combining result of the bit is greater than or equal to the threshold value and the rake combining result is greater than 0, the corresponding bit is hard-decided as gamma^k(ii) a When the absolute value of the rake combining result is equal to or greater than the threshold value and the rake combining result is less than 0, the corresponding bit is hard decided as-gamma^k(ii) a When the absolute value of the rake combining result is less than the threshold value and the rake combining result is greater than 0, the corresponding bit is hard decided as beta^k(ii) a When the absolute value of the rake combining result is less than the threshold value and the rake combining result is less than 0, the corresponding bit is hard decided as beta^k。

The multi-user detection method of the base station in the CDMA mobile communication system, wherein in the segmented hard decision, gamma is^kAnd beta^kThe value ranges are as follows: beta is not less than 0^k≤γ ^k1 or less, and gamma is increased with the increase of the number k^kAnd beta^kThe value of (a) increases.

Because the invention adopts the technical proposal, the new information is merged into the judgment formula of the segmented hard judgment method: in different levels of PIC structures, the reliability of the RAKE combination result is different; with the increase of the series, the strength of reliable bit participation in interference cancellation is judged to be stronger according to the RAKE combination result; the strength of interference cancellation participation by bits decided to be unreliable according to the RAKE combining result also increases.

Drawings

Specific performance characteristics of the present invention are further illustrated by the following examples.

Fig. 1 is a schematic diagram of a multi-stage architecture of a prior art zero-domain hard-decision parallel interference cancellation receiver.

Fig. 2 is a schematic diagram of the PIC architecture of fig. 1.

Fig. 3 is a schematic diagram of the last stage PIC architecture of fig. 1.

Fig. 4 is a functional diagram of a hard decision device of a prior art zero-field hard decision parallel interference cancellation method.

Fig. 5 is a functional diagram of a hard decision device of the segmented hard decision parallel interference cancellation method of the present invention.

Detailed Description

Referring to fig. 1, the base band signal r (t) of the received signal enters the first level PIC structure in parallel. Referring to fig. 2, the input signals entering the PIC architecture in parallel enter the RAKE receiver 13 of each user separately. The RAKE receiver despreads the input signal, performs channel estimation from the despread result, performs multipath combining, and simultaneously sends the multipath combined result to the hard decision device and threshold calculation device 17, and sends the channel estimation result to the signal regenerator 15. The threshold value calculating device calculates a threshold value from the multi-path combination result of the bits with the same serial number of all the users, and sends the threshold value to the hard decision device of each user. The hard decision device of the user carries out hard decision on the multipath combination result of the bit of the corresponding serial number according to the threshold value and sends the decision result to the signal regenerator. The multipath despreading formula is (2), and the multipath combining formula is (3, 4). The specific decision formula of the decision device is (16, 17), and the calculation formula of the threshold value can follow the formula (7-10). The signal regenerator obtains the regenerated signal of the user from the decision result and the channel estimation result, and sends the regenerated signal to the estimation and interference cancellation device 16 for multiple access interference. The signal reproduction formula is (13). It can be seen from the figure that: the baseband signal r (t) of the received signal also enters the estimation and interference cancellation means 16 of the multiple access interference. The device estimates the multiple access interference suffered by each user from the regenerated signal of each user input in parallel, and the signal obtained by eliminating the multiple access interference suffered by a certain user from the baseband signal r (t) of the received signal is used as the output signal of the user in the PIC structure of the current stage and the input signal of the user in the PIC structure of the next stage. The formulas for estimating the multiple access interference and the interference cancellation are (14, 15). The next stage PIC architecture performs the same processing on the parallel input signals. This is done in stages, and when processing is to the final stage PIC architecture, the parallel input signals enter the RAKE receiver 13 of each user separately. The RAKE receiver of the user performs despreading, channel estimation and multipath combining on the input signal to obtain the soft output of the user. The soft output of the user is the final result of the multi-level PIC architecture. In the receiver, the soft output of the user is decoded by a decoder that is fed to the user.

The hard decision process of the segmented hard decision method of the present invention is shown in equations (16, 17). In the segmented hard decision method, the threshold calculation method may follow the threshold calculation method in zero-field hard decision, for example: we can calculate the threshold using equations (7-10) and then make segmented hard decisions according to equations (16, 17). The segmentation decision of the present invention is such that: the hard decision device carries out hard decision on the multipath merging result of the bit according to the threshold value: when the rake combination result of the bit is equal to 0, the corresponding bit is hard decided as 0; when the absolute value of the RAKE combination result of the bit is greater than or equal to the threshold value and the RAKE combination result is greater than 0, the corresponding bit is hard-decided as gamma^k(ii) a When the absolute value of the RAKE combination result is greater than or equal to the threshold value and the RAKE combination result is less than 0, the corresponding bit is hard-decided as-gamma^k(ii) a When the absolute value of the RAKE combination result is less than the threshold value and the RAKE combination result is greater than 0, the corresponding bit is hard-decided as beta^k(ii) a When the absolute value of the RAKE combination result is less than the threshold value and the RAKE combination result is less than 0, the corresponding bit is hard-decided as beta^k。

In segmented hard decision, γ^kAnd beta^kThe value range is as follows: beta is not less than 0^k≤γ ^k1 or less, and gamma is increased with the increase of the number k^kAnd beta^kThe value of (a) increases.

The following is a formula. In the kth level PIC structure, the decision formula of the segmented hard decision method is as follows:

${\hat{a}}_i^{\left(m\right)\left(k\right)}=\mathrm{ssgn}\left\{Y_i^{\left(m\right)\left(k\right)}\right\}----\left(16\right)$

wherein,

x is an independent variable, TH^(m)(k)More than 0 is threshold value, beta is more than or equal to 0^k≤γ^k≤1。

From the decision formula of the segmented hard decision method can be seen: when the rake combination result of the bit is equal to 0, the corresponding bit is hard decided as 0; when the absolute value of the RAKE combination result is greater than or equal to the threshold value, the result is reliable and can be hard judged as +/-gamma^kMaking the bit participate in interference cancellation with a large strength; when the absolute value of the RAKE combining result is less than the threshold, the result is unreliable and the bit can be hard-decided to ± β^kThe bit portion is made to participate in interference cancellation. As the number of stages k increases, the reliability of the RAKE combining result increases. Therefore, as the number of stages increases, β can be made^k、γ^kThe value increases. The hard decision function form of the segmented hard decision PIC is shown in fig. 5.

Because the new information is merged into the decision formula of the segmented hard decision method of the invention: in different levels of PIC structures, the reliability of the RAKE combination result is different; as the number of stages increases, the reliability of the RAKE combining results increases. The new information is integrated, so that the judgment formula of the segmentation hard judgment method is more reasonable, and the segmentation hard judgment method has better performance.

Claims (2)

1, the multi-user detection method of the base station in the code division multiple access mobile communication system, adopts the method for segmentation hard judgment to realize, comprises the following steps: a. The rake receiver performs multipath despreading on the input signal; b. Carry out channel estimation by the despreading result, then perform multipath combination, and send the multipath combination result to the hard decision device and the threshold calculation device at the same time, and send the channel estimation result to the signal regenerator; c, the threshold calculation device calculates a threshold by the multipath combination result of the bits of the same serial number of all users, and sends the threshold to the hard decision device of each user; d. The user's hard decision device performs hard judgment on the multipath combination result of the bit of the corresponding serial number according to the threshold, and sends the judgment result to the signal regenerator; e. The signal regenerator obtains the user's regenerated signal from the judgment result and the channel estimation result, and sends the regenerated signal to the multiple access interference estimation and interference cancellation device; f, multiple access interference estimation and interference cancellation device calculates the multiple access interference of each user from the input regenerative signal of each user; the signal obtained by eliminating the multiple access interference of a certain user from the baseband signal of the received signal is used as the next The input signal of the RAKE receiver of the user in the parallel interference cancellation structure; g. Repeat steps a to f until the number of repetitions is equal to the number of stages set for multi-level parallel interference cancellation, and multi-level interference cancellation is realized; It is characterized in that, the hard decision in the step d is a segmented hard decision, and the decision unit judges the segmented multipath combination result of the bit of the corresponding sequence number according to the threshold: when the Rake combination result of the bit is equal to 0, The corresponding bit is hard-judged as 0; when the absolute value of the Rake combination result of the bit is greater than or equal to the threshold value, and the Rake combination result is greater than 0, the corresponding bit is hard-judged as γ ^k ; when the absolute value of the Rake combination result is greater than or equal to the threshold, and when the Rake combination result is less than 0, the corresponding bit is hard-judged as -γ ^k ; when the absolute value of the Rake combination result is less than the threshold, and the Rake combination result is greater than 0, the corresponding bit is hard-judged is β ^k ; when the absolute value of the Rake combination result is less than the threshold and the Rake combination result is less than 0, the corresponding bit is hard-determined as -β ^k . 2. The method for multi-user detection of a base station in a code division multiple access ^mobile communication system according ^to claim 1, characterized in that, in the segmented hard decision, the value ranges of γ ^k and β ^k are: 0≤βk≤γk ≤1, and with the increase of series k, the values of γ ^k and β ^k increase.

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