CN1482754A - Method and apparatus for two-level weight and parallel disturbance cancellation under MQAM modulation - Google Patents

Abstract

The invention provides a method and apparatus of double layer weighted parallel interference compensation under the MQAM modulation, wherein the PIC arrangement improves substantially compared with the PIC arrangement of the BPSK, and decisional device is deleted, under the MQAM modulation, seeking the soft decisional result of the real component and the soft decisional result of the virtual component, dispatching the symbol to obtain the user regeneration signal from the result of the real component, the result of the virtual component and the channel evaluation result. The method and apparatus by the invention may simplify the arrangement.

Description

The MQAM modulation is double-weighing parallel interference cancellation method and device thereof down

Technical field

The present invention relates to the multiuser detection of base station in the mobile communication system, relate in particular to the method and the device thereof of parallel interference cancellation under MQA (M-aryQuadrature Amplitude Modulation, M ary quadrature Modulation and Amplitude Modulation) modulation.

Background technology

Multiuser detection is to overcome the influence that multiple access disturbs, and improves a kind of Enhanced Technology of cdma system capacity.It can make full use of a plurality of users' information, and a plurality of subscriber signals are carried out joint-detection, disturbs the receiver Effect on Performance thereby reduce multiple access as much as possible, improves the capacity of system.

Verdu proposed best multi-user detector in 1986, but this detector complexity height is difficult to use.The multi-user test method of suboptimum roughly is divided into two classes: linearity test method and interference cancellation method.The linearity test method is carried out linear transformation to the soft output of single user detector, produces one group of new output that can improve performance.Linearity test method better performances, but calculate very complicated.The interference cancellation method is considered as useful signal with the signal of desired user, and other users' signal is considered as interference signal; Eliminate other users' interference earlier from received signal, obtain the signal of desired user, the signal to desired user detects then, thereby improves the performance of system.

The interference cancellation method can be divided into: successive interference cancellation and parallel interference cancellation.The performance of successive interference cancellation method is better than single user detector, but time-delay is bigger, need carry out the power ordering, and amount of calculation is bigger, initialize signal is estimated responsive.The parallel interference cancellation method is eliminated every other user's signal interference concurrently for each user from received signal.This method performance is better than single user detector, and it is little to have a time-delay, and the advantage that computational complexity is little is the at present most possible method that realizes.

Chinese patent application number is that 01132754.5 patent application has proposed double-weighing parallel interference cancellation method.This method is the improvement to traditional parallel interference cancellation method, not only makes the cost minimum of symbol level judgement, and can remedy the deviation of on the statistical significance subscriber signal being estimated, has improved the performance of traditional parallel interference cancellation method greatly.

The multilevel hierarchy of the receiver that double-weighing parallel interference cancellation method is adopted as shown in Figure 1.Structure 1 as shown in Figure 2 for the PIC of this receiver (Parallel Interference Cancellation, parallel interference cancellation).The afterbody PIC structure 2 of this receiver as shown in Figure 3.In the end in the one-level PIC structure, 3 pairs of input signals of user's RAKE receiver carry out despreading, channel estimating and multipath and merge, and obtain user's soft output.User's soft output is exactly the final result of multistage PIC structure.In receiver, user's soft output is fed to user's decoder and deciphers.

Under the BPSK modulation, the principle of double-weighing parallel interference cancellation method is as follows:

If the multipath amalgamation result of the Rake receiver of user i can be expressed as in the k level PIC structure:

$Y_i^{\left(m\right)\left(k\right)}={\mathrm{\μ}}_i{a}_i^{\left(m\right)}+n_i----\left(1\right)$

Y _i ^{(m) (k)}The multipath amalgamation result of representing m the symbol of user i in the k level PIC structure, μ _iBe the real number relevant, obtain by channel estimating with channel fading; n _iBe white Gaussian noise, Normal Distribution N(0, σ _i ²); a _i ^(m)Value is ± 1 under the BPSK modulation.

By (1) formula, can obtain: when $a_i^{\left(m\right)}=1$ The time, Y _i ^{(m) (k)}Normal Distribution N (u _i, σ _i ²); When $a_i^{\left(m\right)}=-1$ The time, Y _i ^{(m) (k)}Normal Distribution N (μ _i, σ _i ²).

If hard decision result ${\hat{a}}_i^{\left(m\right)\left(k\right)}=\mathrm{sgn}\left\{Y_i^{\left(m\right)\left(k\right)}\right\}$ Coefficient of reliability be f _i ^{(m) (k)}Double-weighing parallel interference cancellation method is calculated from bayesian criterion according to following formula _i ^{(m) (k)}Coefficient of reliability: $f_i^{\left(m\right)\left(k\right)}=\tan h\left\{\frac{{\mathrm{\μ}}_i\left|Y_i^{\left(m\right)\left(k\right)}\right|}{{\mathrm{\σ}}_i^2}\right\}----\left(2\right)$

In double-weighing parallel interference cancellation method, by channel estimation results, hard decision result and _i ^{(m) (k)}The reliability of judgement is f _i ^{(m) (k)}Obtain user's regenerated signal.In the signal regeneration process, earlier by _i ^{(m) (k)}And f _i ^{(m) (k)}Obtain a _i ^(m)Soft-decision f _i ^{(m) (k)} _i ^{(m) (k)}, the estimation of soft-decision result, carry out signal regeneration then as the symbol of user's transmission.Here, the effect of soft-decision result in signal regeneration just is equivalent to the effect of hard decision result in the signal regeneration of traditional parallel interference cancellation method.

Double-weighing parallel interference cancellation method adopts the part interference cancellation, establishes the baseband signal of r (t) expression received signal, r _i ^(k+1)(t) output signal of user i (this signal also is the input signal of the RAKE receiver of user i in (k+1) level PIC structure) in the expression k level PIC structure, then the interference cancellation process is as follows:

$r_i^{(k+1)}\left(t\right)=r\left(t\right)-p^{\left(k\right)}{\hat{I}}_i^{\left(k\right)}----\left(3\right)$

Wherein, p ^(k)Be the weights of k level PIC method: p ⁽¹⁾＜p ⁽²⁾...＜p ^(S), S is the progression of PIC;  _i ^(k)Represent in the k level PIC structure estimation that multiple access that i user is subjected to disturbs.

The above double-weighing parallel interference cancellation method proposes under the BPSK modulation.Under same bandwidth, with BPSK chopping phase ratio, high order modulation can improve the rate of information throughput.Therefore, can only adopt high order modulation in the higher occasion of the rate of information throughput in order not increase bandwidth.MQAM is a kind of modulator approach commonly used in the high order modulation, and therefore, research multi-user test method under the MQAM modulation is significant.

Summary of the invention

The objective of the invention is to propose a kind of double-weighing parallel interference cancellation method and device thereof under the MQAM modulation, this method can make the judgement cost minimum of symbol under the MQAM modulation, and can remedy the deviation of on the statistical significance subscriber signal being estimated.

The object of the present invention is achieved like this, and double-weighing parallel interference cancellation method comprises following concrete steps under the MQAM modulation:

A. in every grade of PIC (parallel interference cancellation) structure, user's RAKE receiver is carried out the operation of multi path despreading, channel estimating, multipath merging to input signal, and give user's soft-decision maker and user's signal regenerator with channel estimation results, simultaneously the multipath amalgamation result is given user's soft-decision maker, under the MQAM modulation, the multipath amalgamation result of user's Rake receiver can be expressed as in the k level PIC structure:

$Y_i^{\left(m\right)\left(k\right)}={\mathrm{\μ}}_i{a}_i^{\left(m\right)}+n_i----\left(1\right)$

B. user's at the corresponding levels soft-decision maker generates the soft-decision result of each symbol, and the soft-decision result is given user's signal regenerator by the multipath amalgamation result and the channel estimation results of each symbol of user;

Real part and imaginary part P under the MQAM modulation _IR, P _IMWhen being independently definite, (1) formula can separately be write as following two formulas:

$Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\mathrm{Re}\left(Y_i^{\left(m\right)\left(k\right)}\right)={\mathrm{\μ}}_i{a}_{\mathrm{iR}}^{\left(m\right)}+n_{\mathrm{iR}}----\left(4\right)$

$Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}=\mathrm{Im}\left(Y_i^{\left(m\right)\left(k\right)}\right)={\mathrm{\μ}}_i{a}_{\mathrm{iM}}^{\left(m\right)}+n_{\mathrm{iM}}----\left(5\right)$

Wherein,

$a_i^{\left(m\right)}=a_{\mathrm{iR}}^{\left(m\right)}+j{a}_{\mathrm{iM}}^{\left(m\right)},$ n _i＝n _iR+jn _iM。

To Y in (1) formula _i ^{(m) (k)}Judgement also just resolve into two independently the judgement, promptly by Y _IR ^{(m) (k)}Judgement obtains _IR ^{(m) (k)}, by Y _IM ^{(m) (k)}Judgement obtains _IM ^{(m) (k)}, Y _i ^{(m) (k)}Court verdict be ${\hat{a}}_i^{\left(m\right)\left(k\right)}={\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}+j{\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)},$ Wherein, ${\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\∈\{A_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\},$ ${\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\∈\{B_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\}.$ Decision rule is as follows:

$|{\mathrm{\μ}}_i{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}|={\min }_{i=0}^{\sqrt{M}-1}\left\{\right|{\mathrm{\μ}}_i{A}_i-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\left|\right\}----\left(6\right)$

$|{\mathrm{\μ}}_i{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}|={\min }_{i=0}^{\sqrt{M}-1}\left\{\right|{\mathrm{\μ}}_i{A}_i-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\left|\right\}----\left(6\right)$

If court verdict _IR ^{(m) (k)}Coefficient of reliability be f _IR ^{(m) (k)}, the cost function that judgement is set is:

$C={\left[{\mathrm{\μ}}_i(a_{\mathrm{iR}}^{\left(m\right)}-f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)})\right]}^2.......\left(8\right)$

The average of judgement cost:

$E\left(C\right){\mathrm{\μ}}_i^2\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{(A_i-f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)})}^{2}P\left\{A_i\right|Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\}----\left(9\right)$

Symbol P{A B} is illustrated in the probability that A takes place under the condition of known B in the following formula, can be in the hope of making the f of following formula minimum _IR ^{(m) (k)}Satisfy following formula:

$f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\frac{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{A}_{i}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}----\left(10\right)$

Wherein,

$f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}={\frac{1}{\sqrt{2\mathrm{\π}}{\mathrm{\σ}}_i}e}^{-\frac{{(Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-{\mathrm{\μ}}_i{A}_i)}^2}{{2\mathrm{\σ}}_i^2}}----\left(11\right)$

f _IR ^{(m) (k)} _IR ^{(m) (k)}The real part a of m the symbol that sends for user i _IR ^(m)The soft-decision result;

In like manner, establish _IM ^{(m) (k)}Coefficient of reliability for establishing f _IM ^{(m) (k)}, f then _IM ^{(m) (k)}Satisfy following formula:

$f_{\mathrm{iM}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}=\frac{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{B}_{i}f\left\{Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\right|B_i\}}{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}f\left\{Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\right|B_i\}}----\left(12\right)$

Wherein,

$f\left\{Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\right|B_i\}={\frac{1}{\sqrt{2\mathrm{\π}}{\mathrm{\σ}}_i}e}^{-\frac{{(Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}-{\mathrm{\μ}}_i{B}_i)}^2}{{2\mathrm{\σ}}_i^2}}----\left(13\right)$

f _IM ^{(m) (k)} _IM ^{(m) (k)}The a of the imaginary part of m the symbol that sends for the user _IR ^(m)The soft-decision result; Under MQAM modulation, can directly obtain the soft-decision f as a result of the real part of described symbol _IR ^{(m) (k)} _IR ^{(m) (k)}With the soft-decision of imaginary part f as a result _IM ^{(m) (k)} _IM ^{(m) (k)}, the regenerated signal that obtains the user by the soft-decision result and the channel estimation results of real part, imaginary part.

C. signal regenerator at the corresponding levels obtains user's regenerated signal by user's soft-decision result and user's channel estimation results, and user's regenerated signal is given the estimation and the interference cancellation device of multiple access interference at the corresponding levels;

D. add up other users' regenerated signal of the estimation that multiple access at the corresponding levels disturbs and interference cancellation device obtains the multiple access interference that desired user is subjected to, from the baseband signal of received signal, partly eliminate the multiple access interference that the desired user signal is subjected to, thereby obtain the output signal of this user in the PIC structure at the corresponding levels, this signal is as the input signal of same user's RAKE receiver in the next stage PIC structure simultaneously;

E. repeating step a-d carries out the processing of next stage parallel interference cancellation;

F. for afterbody PIC structure, only carry out the calculating that multi path despreading among the step a, channel estimating and multipath merge, multipath is merged the final result of the soft output of the user i that obtains as user i in the multistage PIC structure, and in receiver, this result is fed to the decoder of user i and deciphers.

The device of realizing said method is a pair of lamina weighing parallel interference cancellation receiver, this receiver is made up of several layers PIC structure, and each layer PIC structure is connected to form successively by some groups of RAKE receiver, soft-decision maker, signal regenerator and multiple access Interference Estimation and interference cancellation device.

The present invention proposes the double-weighing parallel interference cancellation method and apparatus under the MQAM modulation.This method can make the judgement cost minimum of symbol under the MQAM modulation, and can remedy the deviation of on the statistical significance subscriber signal being estimated.Simultaneously the PIC structure of MQAM has been compared improvement with the PIC structure of BPSK, and it can directly calculate the soft-decision result, needn't calculate the hard decision result earlier, computed reliability coefficient again, thus simplify the structure, also reduced amount of calculation.

Description of drawings

Accompanying drawing 1 is the multilevel hierarchy schematic diagram of double-weighing parallel interference cancellation receiver;

Accompanying drawing 2 is PIC structural representations of double-weighing parallel interference cancellation receiver;

Accompanying drawing 3 is afterbody PIC structural representations of double-weighing parallel interference cancellation receiver;

Accompanying drawing 4 is MQAM modulation PIC structural representations of double-weighing parallel interference cancellation receiver down.

Embodiment

The present invention is further illustrated below in conjunction with drawings and Examples.

Realize the MQAM modulation device of double-weighing parallel interference cancellation method down, it is double-weighing parallel interference cancellation receiver, the multilevel hierarchy of this receiver as shown in Figure 1, the afterbody PIC structure of this receiver as shown in Figure 3, the PIC structure of this receiver is as shown in Figure 4.

As shown in Figure 1, this receiver is connected and composed successively by identical PIC structure and the afterbody PIC structure of some levels.General PIC progression is 3～4 grades.

As shown in Figure 3, in the end in the one-level PIC structure, device 3 is RAKE receiver, in this PIC structure several RAKE receiver is arranged, and each user has and have only a RAKE receiver.User's RAKE receiver is carried out multi path despreading, channel estimating to the input signal from the same user of previous stage, carries out multipath then and merges, and obtains user's soft output.In the end in the one-level PIC structure, user's soft output is exactly the final result of multistage PIC structure.

As shown in Figure 4, this PIC structure is connected to form successively by the estimation and the interference cancellation device of some groups of RAKE receiver, soft-decision maker, signal regenerator and a multiple access interference.Device 3 is RAKE receiver, it carries out multi path despreading to input signal, carries out channel estimating by the despreading result, carries out multipath then and merges, and give soft-decision maker 8 with the RAKE amalgamation result, give soft-decision maker and signal regenerator 5 with channel estimation results.Device 8 is soft-decision makers, and it obtains soft-decision by RAKE amalgamation result and channel estimation results, and gives signal regenerator 5 with the soft-decision result.Device 5 is signal regenerators, and it obtains user's regenerated signal by two input signals, and user's regenerated signal is given the estimation and the interference cancellation device 6 of multiple access interference.Device 6 is estimation and interference cancellation devices that multiple access disturbs, it is disturbed by the multiple access that each user's the regenerated signal of input calculates each user respectively, and the multiple access of partly eliminating certain user from the baseband signal of received signal disturbs the signal that the obtains input signal as this user's RAKE receiver in the next stage PIC structure.

Double-weighing parallel interference cancellation method under the MQAM modulation is come specific implementation by following steps:

As shown in Figure 1, the baseband signal r of received signal (t) enters first order PIC structure 1 among the figure with parallel mode.As shown in Figure 4, and the input signal that is advanced into PIC structure 1 enter each user's RAKE receiver 3 respectively.RAKE receiver 3 is carried out despreading to input signal earlier, carries out channel estimating, multipath merging by the despreading result then, and gives soft-decision maker 8 with the multipath amalgamation result, gives soft-decision maker 8 and signal regenerator 5 with channel estimation results.Soft-decision maker 8 obtains the soft-decision result by multipath amalgamation result and channel estimation results.

Part interference cancellation method is still adopted in MQAM modulation double-weighing parallel interference cancellation method down, and modulation proposes but the computational methods of hard decision coefficient of reliability are at MQAM.MQAM modulation soft-decision result down calculates by following.

Under the MQAM modulation, m the symbol that user i sends can be expressed as:

$a_i^{\left(m\right)}\∈\{P_i-P_{\mathrm{iR}}+{\mathrm{jP}}_{\mathrm{iM}},i=\mathrm{0,1},...,M-1\},$

Wherein,

$P_{\mathrm{iR}}\∈\{A_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\},$ $P_{\mathrm{iM}}\∈\{B_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\},$ Under the MQAM modulation, the multipath amalgamation result of the Rake receiver of user i still can be expressed as in the k level PIC structure:

$Y_i^{\left(m\right)\left(k\right)}={\mathrm{\μ}}_i{a}_i^{\left(m\right)}+n_i----\left(1\right)$

But, under the MQAM modulation, the Y in the following formula _i ^{(m) (k)}, a _i ^(m)It is plural number; n _iBe white complex gaussian noise, establish n _iReal part and imaginary part respectively Normal Distribution N (0, σ _i ²), σ _i ²Can obtain by noise power estimation method, use as known quantity at this paper; μ _iBe real number, calculate by channel estimation results.

Order $N=\mathrm{lo}{g}_2^M,$ Then under the MQAM modulation, N bit determined the symbol of a MQAM.The MQAM symbol determine that two kinds of situations can be arranged only:

In first kind of situation N bit Individual bit is determined the real part of MQAM symbol, in addition Individual bit is determined the imaginary part of MQAM symbol, i.e. MQAM modulation is real part and imaginary part P down _IR, P _IMBe independent definite;

Real part and imaginary part P under second kind of situation MQAM modulation _IR, P _IMNot independent definite;

Usually, the MQAM modulation real part and the imaginary part of symbol down is independent definite, as 16QAM and 64QAM modulation.The present invention only considers MQAM the modulation real part and the independently definite situation of imaginary part of symbol down.

Real part and imaginary part P under the MQAM modulation _IR, P _IMWhen being independently definite, (1) formula can separately be write as following two formulas:

$Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\mathrm{Re}\left(Y_i^{\left(m\right)\left(k\right)}\right)={\mathrm{\μ}}_i{a}_{\mathrm{iR}}^{\left(m\right)}+n_{\mathrm{iR}}----\left(4\right)$

$a_i^{\left(m\right)}=a_{\mathrm{iR}}^{\left(m\right)}+j{a}_{\mathrm{iM}}^{\left(m\right)},$

Wherein, $Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}=\mathrm{Im}\left(Y_i^{\left(m\right)\left(k\right)}\right)={\mathrm{\μ}}_i{a}_{\mathrm{iM}}^{\left(m\right)}+n_{\mathrm{iM}}.....\left(5\right)$ n _i＝n _iR+jn _iM。

To Y in (1) formula _i ^{(m) (k)}Judgement also just resolve into two independently the judgement, promptly by Y _IM ^{(m) (k)}Judgement obtains _IR ^{(m) (k)}, by Y _IM ^{(m) (k)}Judgement obtains _IM ^{(m) (k)}Y _i ^{(m) (k)}Court verdict be ${\hat{a}}_i^{\left(m\right)\left(k\right)}={\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}+j{\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}.$ Wherein, ${\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\∈\{B_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\},$ ${\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\∈\{B_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\}.$ Decision rule is as follows:

$|{\mathrm{\μ}}_i{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}|={\min }_{i=0}^{\sqrt{M}-1}\left\{\right|{\mathrm{\μ}}_i{A}_i-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\left|\right\}----\left(6\right)$

$|{\mathrm{\μ}}_i{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}|={\min }_{i=0}^{\sqrt{M}-1}\left\{\right|{\mathrm{\μ}}_i{A}_i-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\left|\right\}----\left(6\right)$

If court verdict _IR ^{(m) (k)}Coefficient of reliability be f _IR ^{(m) (k)}, the cost function that judgement is set is:

$C={\left[{\mathrm{\μ}}_i(a_{\mathrm{iR}}^{\left(m\right)}-f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)})\right]}^2$ $----\left(8\right)$

The average of judgement cost:

$E\left(C\right)={\mathrm{\μ}}_i^2\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{(A_i-f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)})}^{2}P\left\{A_i\right|Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\}----\left(9\right)$

In the following formula symbol P{A B} be illustrated in the probability that A takes place under the condition of known B.

Can be in the hope of making the f of following formula minimum _IR ^{(m) (k)}Satisfy following formula:

$f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\frac{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{A}_{i}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}----\left(10\right)$

Wherein, $f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}={\frac{1}{\sqrt{2\mathrm{\π}}{\mathrm{\σ}}_i}e}^{-\frac{{(Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-{\mathrm{\μ}}_i{A}_i)}^2}{{2\mathrm{\σ}}_i^2}}----\left(11\right)$

f _IR ^{(m) (k)} _IR ^{(m) (k)}The real part a of m the symbol that sends for user i _IR ^(m)The soft-decision result.

In like manner, establish _IM ^{(m) (k)}Coefficient of reliability be f _IM ^{(m) (k)}, f then _IM ^{(m) (k)}Satisfy down:

$f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\frac{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{A}_{i}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}----\left(10\right)$

Wherein,

$f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}={\frac{1}{\sqrt{2\mathrm{\π}}{\mathrm{\σ}}_i}e}^{-\frac{{(Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-{\mathrm{\μ}}_i{A}_i)}^2}{{2\mathrm{\σ}}_i^2}}----\left(11\right)$

f _IM ^{(m) (k)} _IM ^{(m) (k)}Be the imaginary part a of m symbol of user i transmission _IM ^(m)The soft-decision result.Under MQAM modulation, the soft-decision that can directly obtain the real part that sends symbol is f as a result _IR ^{(m) (k)} _IR ^{(m) (k)}With the soft-decision of imaginary part f as a result _IM ^{(m) (k)} _IM ^{(m) (k)}, by the soft-decision result of real part, the soft-decision result of imaginary part and the regenerated signal that channel estimation results obtains the user.Like this, can simplified structure, reduce the multiplication number of times simultaneously.

The soft-decision result that soft-decision maker 8 is tried to achieve said method gives signal regenerator 5.Signal regenerator 5 obtains user's regenerated signal by two signals of input, and regenerated signal is sent into the estimation and the interference cancellation device 6 of multiple access interference.As we can see from the figure, the baseband signal r of received signal (k) also enters estimation and the interference cancellation device 6 that multiple access disturbs.This device estimates that by each user's of parallel input regenerated signal the multiple access that each user is subjected to disturbs, from the baseband signal r (t) of received signal, partly eliminate multiple access that certain user is subjected to and disturb the signal that obtains output signal, the input signal of this user's RAKE receiver in the next stage PIC structure as this user in the PIC structure at the corresponding levels.Next stage PIC structure is carried out same processing to the signal of parallel input.Handle so step by step, when handling to the end one-level PIC structure (as shown in Figure 3), the signal of parallel input enters each user's RAKE receiver 3 respectively.3 pairs of input signals of user's RAKE receiver carry out despreading, channel estimating and multipath and merge, and obtain user's soft output.User's soft output is exactly the final result of multistage PIC structure.In receiver, user's soft output is fed to user's decoder and deciphers.

Need to prove, any for those of ordinary skill, the unsubstantiality that invention is made is changed, or conspicuous replacement all belongs to protection category of the present invention.

Claims (2)

1, MQAM modulates double-weighing parallel interference cancellation method down in a kind of mobile communication system, it is characterized in that described method comprises the steps:

A. in every grade of parallel interference cancellation structure, user's RAKE receiver is carried out the operation of multi path despreading, channel estimating, multipath merging to input signal, and give user's soft-decision maker and user's signal regenerator with channel estimation results, simultaneously the multipath amalgamation result is given user's soft-decision maker, under the MQAM modulation, the multipath amalgamation result of the Rake receiver of user i can be expressed as in the k level PIC structure:

$Y_i^{\left(m\right)\left(k\right)}={\mathrm{\μ}}_i{a}_i^{\left(m\right)}+n_i----\left(1\right)$

B. user's at the corresponding levels soft-decision maker generates the soft-decision result of each symbol, and the soft-decision result is given user's signal regenerator by the multipath amalgamation result and the channel estimation results of each symbol of user;

Real part and imaginary part P under the MQAM modulation _IR, P _IMWhen being independently definite, (1) formula can separately be write as following two formulas:

$Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\mathrm{Re}\left(Y_i^{\left(m\right)\left(k\right)}\right)={\mathrm{\μ}}_i{a}_{\mathrm{iR}}^{\left(m\right)}+n_{\mathrm{iR}}----\left(4\right)$

$Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}=\mathrm{Im}\left(Y_i^{\left(m\right)\left(k\right)}\right)={\mathrm{\μ}}_i{a}_{\mathrm{iM}}^{\left(m\right)}+n_{\mathrm{iM}}----\left(5\right)$

Wherein, $a_i^{\left(m\right)}=a_{\mathrm{iR}}^{\left(m\right)}+j{a}_{\mathrm{iM}}^{\left(m\right)},$ n _i＝n _iR+jn _iM。

To Y in (1) formula _i ^{(m) (k)}Judgement also just resolve into two independently the judgement, promptly by Y _IR ^{(m) (k)}Judgement obtains _IR ^{(m) (k)}, by Y _IM ^{(m) (k)}Judgement obtains _IR ^{(m) (k)}, Y _i ^{(m) (k)}Court verdict be ${\hat{a}}_i^{\left(m\right)\left(k\right)}={\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}+{j\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)},$ Wherein, ${\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\∈\{A_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\},$ ${\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\∈\{B_i\∈R,i=\mathrm{0,1},...,\sqrt{M}-1\},$

Decision rule is as follows:

$|{\mathrm{\μ}}_i{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}|={\min }_{i=0}^{\sqrt{M}-1}\left\{\right|{\mathrm{\μ}}_i{A}_i-Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\left|\right\}----\left(6\right)$

$|{\mathrm{\μ}}_i{\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}-Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}|={\min }_{i=0}^{\sqrt{M}-1}\left\{\right|{\mathrm{\μ}}_i{B}_i-Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\left|\right\}----\left(7\right)$

If court verdict _IR ^{(m) (k)}Coefficient of reliability be f _IR ^{(m) (k)}, the cost function that judgement is set is:

$C={\left[{\mathrm{\μ}}_i(a_{\mathrm{iR}}^{\left(m\right)}-f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)})\right]}^2----\left(8\right)$

The average of judgement cost:

$E\left(C\right)={\mathrm{\μ}}_i^2\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{(A_i-f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)})}^{2}P\left\{A_i\right|Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\}----\left(9\right)$

Symbol P{A B} is illustrated in the probability that A takes place under the condition of known B in the following formula, can be in the hope of making the f that satisfies of following formula minimum _IR ^{(m) (k)}Following formula:

$f_{\mathrm{iR}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iR}}^{\left(m\right)\left(k\right)}=\frac{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{A}_{i}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}}----\left(10\right)$

Wherein,

$f\left\{Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}\right|A_i\}={\frac{1}{\sqrt{2\mathrm{\π}}{\mathrm{\σ}}_i}e}^{-\frac{{(Y_{\mathrm{iR}}^{\left(m\right)\left(k\right)}-{\mathrm{\μ}}_i{A}_i)}^2}{{2\mathrm{\σ}}_i^2}}----\left(11\right)$

f _IR ^{(m) (k)} _IR ^{(m) (k)}The real part a of m the symbol that sends for user i _IR ^(m)The soft-decision result;

In like manner, establish _IM ^{(m) (k)}Coefficient of reliability be f _IM ^{(m) (k)}, f then _IM ^{(m) (k)}Satisfy following formula:

$f_{\mathrm{iM}}^{\left(m\right)\left(k\right)}{\hat{a}}_{\mathrm{iM}}^{\left(m\right)\left(k\right)}=\frac{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}{B}_{i}f\left\{Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\right|B_i\}}{\underset{i=0}{\overset{\sqrt{M}-1}{\mathrm{\Σ}}}f\left\{Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\right|B_i\}}----\left(12\right)$

Wherein,

$f\left\{Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}\right|B_i\}={\frac{1}{\sqrt{2\mathrm{\π}}{\mathrm{\σ}}_i}e}^{-\frac{{(Y_{\mathrm{iM}}^{\left(m\right)\left(k\right)}-{\mathrm{\μ}}_i{B}_i)}^2}{{2\mathrm{\σ}}_i^2}}----\left(13\right)$

f _IM ^{(m) (k)} _IM ^{(m) (k)}The imaginary part a of m the symbol that sends for user i _IM ^(m)The soft-decision result;

C. signal regenerator at the corresponding levels obtains user's regenerated signal by user's soft-decision result and user's channel estimation results, and user's regenerated signal is given the estimation and the interference cancellation device of multiple access interference at the corresponding levels;

D. add up other users' regenerated signal of the estimation that multiple access at the corresponding levels disturbs and interference cancellation device obtains the multiple access interference that desired user is subjected to, from the baseband signal of received signal, partly eliminate the multiple access interference that the desired user signal is subjected to, thereby obtain the output signal of this user in the PIC structure at the corresponding levels, this signal is as the input signal of same user's RAKE receiver in the next stage PIC structure simultaneously;

E. repeating step a-d carries out the processing of next stage parallel interference cancellation;

F. for afterbody PIC structure, only carry out the calculating that multi path despreading among the step a, channel estimating and multipath merge, multipath is merged the i final result of the soft output of the user i that obtains as user in the multistage PIC structure, and in receiver, this result is fed to the decoder of user i and deciphers.

2, a kind of device of realizing the described parallel interference cancellation method of claim 1, described device comprises the identical parallel interference cancellation structure PIC structure different with afterbody of some levels, described afterbody PIC structure comprises several RAKE receiver, it is characterized in that the identical PIC structure of described each grade is connected to form successively by estimation and the interference cancellation device that several RAKE receiver, soft-decision maker, signal regenerator and multiple access disturb.

Images