CN1505412A - Method for estimating number of users of mobile terminal in mobile communication system - Google Patents

Abstract

The invention discloses a method for estimating mobile terminal user amount in mobile communication system. It includes: estimating noise power according to the channel impulse response; the threshold value selecting; selecting the channel impulse response; completing union detecting algorithm. The invention enhances the system performance, and decrease the calculation complexity.

Description

The method of estimating number of users of mobile terminal in the mobile communication system

(1). technical field

The invention belongs to field of mobile communication, specifically relate to a number of users method of estimation of portable terminal in the TDD CDMA mobile communication system

(2). background technology

In time-division duplex (to call TD-CDMA in the following text) mobile communication system,, adopt joint detection algorithm to carry out the data despreading usually in order to reduce the influence that multiple access disturbs (MAI) and intersymbol interference (ISI).Associated detection technique is a kind of based on multiple access being disturbed the signal processing method that suppresses or eliminate.It all treats as the useful signal with certain feature with all users' signal, makes full use of the signal that the various information butt joint that can access receive and handles, and disturbs in the hope of suppressing or eliminate multiple access.

In the TD-CDMA system, data send by data burst (Data Burst) form, comprise a plurality of user's data and middle trained code (midamble) in a burst, and middle trained code is used for estimated channel impulse response (to call CIR in the following text): $\hat{h}=G^{-1}{e}_{\mathrm{mid}},$ E in the formula _MidBe the middle trained code (midamble) that portable terminal receives, G is the matrix that is generated by known middle trained code.

In joint-detection, use ${\hat{d}}_{\mathrm{est}}={\left(A^{T_{*}}A\right)}^{-1}{A}^{T_{*}}e$ Original transmission data are estimated, wherein

The expression receiving terminal is to the valuation of original transmission data, and e is the data that receiving terminal receives, and A represents sytem matrix, A ^{* T}The conjugate transpose of expression A.A=(A ⁽¹⁾, A ⁽²⁾...., A ^(K)By K user's spreading code and channel impulse response (CIR) valuation decision, i.e. A ^(k)By $b^{\left(k\right)}=C^{\left(k\right)}{\hat{h}}^{\left(k\right)}$ Generate C ^(k)With

Represent the valuation of k user's spreading code and channel impulse response respectively.Which code channel is activated in a time slot, has just used which spread spectrum codes C ^(k), when network does not send to portable terminal with these information, portable terminal just can't the constructing system matrix A.If network passes through the signaling portable terminal with these information, because the use of code channel is dynamic change, thereby huge the increasing of the signaling traffic of base station and portable terminal, the utilance of system is reduced.

Existing channel impulse response (CIR) valuation

Be earlier by formula e _Mid=Gh+n is again by formula $\hat{h}=G^{-1}{e}_{\mathrm{mid}}$ Calculate, wherein n represents the noise in the transmission channel.Fig. 1 represents to use the result of the definite channel CIR of above-mentioned algorithm.Fig. 1 points out in the impulse response of noiseless disturbed condition lower channel by forming tap coefficient and time of delay, first, second, third and fourth user represents that respectively the user has used relevant code track, first CIR estimating window is illustrated in [0, W] first user is judged in the scope, wherein exist restriction relation: P=MW, P represents the length of CIR, and M represents number of users, and W represents that the CIR estimating window is long.Fig. 2 points out the code channel that is activated (i.e. the code channel that is used by the user), in its CIR estimating window, there is the coefficient of a tap to substantially exceed the coefficient of other tap in the window, and do not have the code channel that activates, just to the estimation of interference noise, the coefficient of each tap is all smaller in corresponding CIR estimating window.

If when carrying out joint-detection, whether code channel is activated all according to fixed forms such as code channel 1 corresponding spreading code 1, code channel 2 corresponding spreading codes 2, the corresponding spreading code k of code channel k, because the valuation of the channel impulse response of un-activation code channel is smaller, make that the value of some row or column is less among the sytem matrix A, thereby A ^{* T}A becomes singular matrix, can't find the solution (A ^{* T}A) ^-1Inverse matrix descends systematic function, even makes the system break communication.

(3). summary of the invention

Purpose of the present invention provides the method for estimating number of users of mobile terminal in a kind of mobile communication system.It can reduce the computation complexity that the user data valuation is calculated in the joint-detection, and the systematic function of mobile communication is improved, and guarantees that communication is unimpeded.

For reaching above-mentioned purpose, the present invention is characterized in that: according to the channel impulse response estimating noise power; The selection of threshold value; Carry out selected to channel impulse response; Finish joint detection algorithm.

Calculate the energy of each tap of CIR by the CIR valuation, to the channel impulse response estimating noise power.

The peak-peak tap that utilizes above-mentioned CIR valuation calculating noise energy to remove each CIR estimating window is with the energy addition of remaining tap; Energy addition with above-mentioned each CIR estimating window; The computing noise energy;

The energy of each tap of CIR is compared with the processing noise energy.

A threshold value and noise energy addition are obtained handling the selection that noise energy is carried out threshold value.

The thresholding span is 0～1.

Determine that by above-mentioned selected CIR valuation a number of users (comprising desired user and interference user number) in the time slot carries out selected to channel impulse response.

To the selected method of channel impulse response, with the energy of each tap of CIR with handle noise energy relatively, if the energy of tap then keeps corresponding tap coefficient, otherwise tap coefficient is changed to 0 greater than handling noise energy.

The picking equipment that is used for channel impulse response is used for the picking equipment of channel impulse response, comprises that CIR estimates and selected CIR equipment, selected CIR and the employed spreading code of user that estimated is multiplied each other constructing system matrix A and be used for joint-detection ${\hat{d}}_{\mathrm{est}}={\left(A^{T_{*}}A\right)}^{-1}{A}^{T_{*}}e$ Device, utilize the said system matrix to carry out the valuation that matrix operation obtains user data.

The invention has the beneficial effects as follows: carry out selected to CIR by certain determination methods, keep the code channel (i.e. the code channel that is used by the user) that is activated, determine number of users in the time slot, selected CIR reduces the dimension of sytem matrix A in the joint-detection, reduce computation complexity, solve the uncertain problem of number of users in the time slot that when portable terminal adopts existing associated detection technique to carry out the data despreading, runs into.The present invention is applicable in the mobile terminal device of TD-CDMA mobile communication system that the TD-CDMA system comprises that TD-SCDMA and WCDMA-TDD use middle trained code to carry out in the mobile communication system of channel estimating.

(4) description of drawings

Fig. 1 is the CIR drawing for estimate under the noiseless disturbed condition;

Fig. 2 is actual CIR drawing for estimate;

Fig. 3 is selected CIR drawing for estimate;

Fig. 4 estimates the flow chart of user in the time slot for the CIR estimated value;

Fig. 5 combines the block diagram of finishing the data despreading for selected CIR with joint detection algorithm;

Fig. 6 is downlink combined detection simulation figure as a result.

The present invention is described further below by embodiment.

(5). embodiment

Referring to Fig. 4.Method based on number of users in time slot of channel impulse response (CIR) valuation estimation may further comprise the steps:

1) pass through the energy that each tap of CIR is calculated in the CIR valuation, $P_i=\mathrm{Re}{\left\{{\hat{h}}_i\right\}}^2+\mathrm{Im}{\left\{{\hat{h}}_i\right\}}^2,$ I=0 ..., P-1, P are the length of channel impulse response, Re (x), Im (x) represents real part and the imaginary part of plural x respectively;

2) utilize above-mentioned CIR valuation calculating noise energy; Because e _Mid=Gh+n carries out power conversion to this formula, and the formula both sides all use corresponding ENERGY E to represent: $E\left({e_{\mathrm{mid}}^{T_{*}}e}_{\mathrm{mid}}\right)=E\left({(\mathrm{Gh}+n)}^{T_{*}}(\mathrm{Gh}+n)\right)=E\left(h^{T_{*}}{G}^{T_{*}}\mathrm{Gh}\right)+E\left(n^{T_{*}}n\right),$ E (e wherein _Mid ^{* T}e _Mid) expression received signal energy, E (h ^{* T}G ^{* T}Gh) expression signal energy, E (n ^{* T}N) energy of expression noise, so the average noise energy is:

$P_n=E\left(n^{T_{*}}n\right)/N=E\left(e_{\mathrm{mid}}^{T_{*}}{e}_{\mathrm{mid}}\right)/N-E\left(h^{T_{*}}{G}^{T_{*}}\mathrm{Gh}\right)/N$

3) threshold value and the direct addition of noise energy are obtained handling noise energy; That is: P _n+ P _Th

4) energy with each tap of CIR compares with the processing noise energy, if P _i＞P _n+ P _Th, then keep Otherwise, ${\hat{h}}_i=0,$ I=0 ..., P-1 obtains selected CIR valuation;

5) determine a number of users (comprising desired user and interference user number) in the time slot by above-mentioned selected CIR valuation.If its selected CIR existence is not 0 tap in certain CIR estimating window, then illustrate in the CIR estimating window to have excited users, because CIR estimating window and code channel are corresponding, thereby can determine which code channel is used by the user.

The method of approximate estimation noise energy comprises the steps:

1) removes the peak-peak tap of each CIR estimating window, the energy addition of remaining tap is obtained P _{CIR, m}, m=1 ..., M, M represent the quantity of CIR estimating window, and the number of remaining tap in each CIR estimating window is counted, and represent that with W-1 W is that the estimating window of CIR is long;

2) with the energy P of above-mentioned each CIR estimating window _{CIR, m}Addition obtains P _CIR, P _CIR/ (M (W-1)) is exactly the estimated value of the average noise energy of each tap;

3) handle noise energy by P _CIR/ (M. (W-1))+P _ThObtain.

Described predetermined threshold P _ThThe constant that the person of being to use is specific.The inventor proves P by experiment _ThAppropriate value at 0＜P _Th≤ 1 scope.

Referring to Fig. 3.The method that selected CIR is used in combination with joint-detection is, CIR estimate with ${\hat{d}}_{\mathrm{est}}={\left(A^{T_{*}}A\right)}^{-1}{A}^{T_{*}}e$ Between add selected CIR (being the number of users estimation module).

Next 4 describe in detail with reference to the accompanying drawings according to relevant device of the present invention.

Referring to Fig. 4., a CIR signal that has estimated $\hat{h}=({\hat{h}}_1,{\hat{h}}_2,...,{\hat{h}}_i,...,{\hat{h}}_P)$ Shunted and offered respectively first calculating unit 1 and the 4th calculating unit 4.

Described first parts are suitable for calculating the energy of each tap of CIR, are expressed as:

$P_i={\left|{\hat{h}}_i\right|}^2=\mathrm{Re}{\left\{{\hat{h}}_i\right\}}^2+\mathrm{Im}{\left\{{\hat{h}}_i\right\}}^2,i=0,...,P-1---\left(1\right)$

Described second parts are used for the calculating average noise energy, handle noise energy, and in computational process, the estimating window of CIR is long to have MW=P for W, and M represents the estimating window number of CIR in the formula, and is corresponding with each activated code channel; P represents the total length of CIR.In certain estimating window, the CIR total noise power:

$P_{\mathrm{CIR}}=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}(\underset{w=1}{\overset{M}{\mathrm{\Σ}}}{P}_{(m-1)\·W+w}-P_{(m-1)W,\max })$

$=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\{\underset{w=1}{\overset{W}{\mathrm{\Σ}}}\left(\mathrm{Re}\right\{{\hat{h}}_{(m-1)W+w}{)}^2+\mathrm{Im}{\left\{{\hat{h}}_{(m-1)W+w}\right\}}^2)-P_{(m-1)W,\max }\}---\left(2\right)$

P in the formula _{(m-1) W, max}Be at { the peak value in (m-1) W, mW} estimating window.The average noise energy of each tap of CIR is P _CIR/ (M (W-1)).

The 3rd component computes:

P _CIR/(M·(W-1))+P _th??????????????????????????????????(4)

The signal that described the 4th parts comparison provides based on parts 1 and parts 3, and carry out selected to channel impulse response CIR according to comparative result.To all i (1≤i≤P), work as P _i＞P _CIR/ (M (W-1))+P _ThThe time, Remain unchanged, otherwise ${\hat{h}}_i=0.$ Fig. 3 is selected CIR result.Following table is actual CIR of first CIR estimating window and selected CIR data.Numeral is a tap coefficient in the table.

Tap number	?1	?2	?3	?4
					Actual CIR	?0.0258+0.1342i	?0.0506+0.1058i	?0.0245+0.0428i	?-0.0066+0.0436i
Selected CIR	?0	?0	?0	?0
					Tap number	?5	?6	?7	?8
Actual CIR	?-0.0819-0.0666i	?0.6226-0.3807i	?-0.0533-0.1210i	?0.0273+0.0659i
					Selected CIR	?0	?0.6226-0.3807i	?0	?0
Tap number	?9	?10	?11	?12
					Actual CIR	?0.0165-0.0554i	?-0.2483+0.0636i	?0.0444+0.1083i	?-0.0615+0.0338i
Selected CIR	?0	?0	?0	?0
					Tap number	?13	?14	?15	?16
Actual CIR	?0.0542-0.0234i	?-0.0156+0.0108i	?-0.0294+0.0300i	?-0.0499-0.0768i
					Selected CIR	?0	?0	?0	?0

The spreading code sequence number of described the 5th component computes number of users and use.(1≤m≤M) is in that ((m-1) W mW) in the scope, judges to all m

Whether coefficient is arranged is not 0 tap, if having, then has the user to use this code channel, and the sequence number of code channel that value m is just corresponding according to mobile communication standard (as TD-SCDMA or WCDMA-TDD) regulation, can be found out the employed spreading code sequence number of this code channel.

Referring to Fig. 5.CIR estimate with ${\hat{d}}_{\mathrm{est}}={\left(A^{T_{*}}A\right)}^{-1}{A}^{T_{*}}e$ Between, add a selected CIR device, by selected CIR, the number of users in the time slot not only can be estimated, and the computation complexity of joint detection algorithm can be reduced, make system obtain bigger improvement.Referring to Fig. 6.Abscissa among Fig. 6 is represented the input signal-to-noise ratio of receiving terminal, and ordinate is represented error rate index.To be portable terminal know under the condition which code channel used by the user in hypothesis " actual CIR " curve among Fig. 6, from $\hat{h}=G^{-1}{e}_{\mathrm{mid}}$ Take out cir value in the corresponding CIR estimating window in the valuation and be used for the generation system matrix A, obtain the ber curve of joint-detection data estimation.The ber curve that obtains is handled in " selected CIR " expression by the present invention.Following table is an emulated data, and numeral is the size of the error rate (BER) in the table.

??Eb/N0(dB)	??-8	??-6	??-4	??-2	??0	??2	??4	???6	??8	??10	??12
												Actual CIR	??0.3199	??0.2515	??0.1777	??0.1040	??0.0552	??0.0164	??0.0037	???0.0003	??0	??0	??0
Selected CIR	??0.3118	??0.2035	??0.1078	??0.0573	??0.0264	??0.0085	??0.0012	???0	??0	??0	??0

From last table and simulation curve as can be seen, under the situation of known users number, the systematic function that obtains by the present invention is better than the method that prior art adopts, if under the ignorant situation of number of users, utilize prior art estimating user data, its performance will be inferior to technology (deteriorating to single user detects) or the terminal that the present invention uses can't operate as normal.

Claims (9)

1. the method for estimating number of users of mobile terminal in the mobile communication system is characterized in that: according to the channel impulse response estimating noise power; The selection of threshold value; Carry out selected to channel impulse response; Finish joint detection algorithm.

2. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 1 is characterized in that: calculate the energy of each tap of CIR by the CIR valuation, to the channel impulse response estimating noise power.

3. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 2 is characterized in that: the peak-peak tap that utilizes above-mentioned CIR valuation calculating noise energy to remove each CIR estimating window, with the energy addition of remaining tap; Energy addition with above-mentioned each CIR estimating window; The computing noise energy;

4. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 2 is characterized in that: the energy and the processing noise energy of each tap of CIR are compared.

5. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 1 is characterized in that: a threshold value and noise energy addition are obtained handling the selection that noise energy is carried out threshold value.

6. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 5 is characterized in that: the thresholding span is 0～1.

7. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 1 is characterized in that: determine that by above-mentioned selected CIR valuation a number of users (comprising desired user and interference user number) in the time slot carries out selected to channel impulse response.

8. the method for estimating number of users of mobile terminal in the mobile communication system according to claim 1, it is characterized in that: to the selected method of channel impulse response, the energy of each tap of CIR is compared with the processing noise energy, if the energy of tap is greater than handling noise energy, then keep corresponding tap coefficient, otherwise tap coefficient is changed to 0.

9. equipment of realizing claim 1 method, it is characterized in that: be used for the picking equipment of channel impulse response, comprise that CIR estimates and selected CIR equipment, selected CIR is multiplied each other with the employed spreading code of user that has estimated, constructing system matrix A and be used for joint-detection ${\hat{d}}_{\mathrm{est}}={\left(A^{T_{*}}A\right)}^{-1}{A}^{T_{*}}e$ Device, utilize the said system matrix to carry out the valuation that matrix operation obtains user data.

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