CN1863022B - Method for detecting code channel - Google Patents

Abstract

The invention discloses a method for code channel detecting that can be used in the code dividing multi address system with the exclusive corresponding relationship between every channel estimating window and every channel code. It includes the following steps: when the receiver receives the signal, the channel estimating and post process would be performed based on the basic midamble code sent from the system to gain channel response of every corresponding basic midamble code; determining signal channel estimating window; determining activated code channel corresponding to signal channel estimating window; taking multi-user detecting by using the activated code channel. The invention could accurately determine signal channel estimating window, exactly orient the channel code, and realize multi-user detecting.

Description

The method that a kind of code channel detects

Technical field

The present invention relates to code division multiple access (CDMA) system communication technology, be meant the method that a kind of code channel detects especially.

Background technology

In existing time division duplex CDMA (TDD-CDMA) standard, 3 kinds of the code channel method of salary distribution: specific, default and common have been defined.Wherein, the specific mode is come corresponding relation between notification channel sign indicating number and the channel estimation window by high level.Default and common mode define corresponding relation between channel code and the channel estimation window according to the criterion of acquiescence.For these 3 kinds of methods of salary distribution, each sub-district only takies 1 basic midamble sign indicating number, and its each displacement window is corresponding with one or more channel codes, and these channel codes may have identical spread spectrum coefficient, also may have different spread spectrum coefficients.In communication process, high level tells the distribution condition of desired user to receiving terminal receiver is realized Multiuser Detection according to these information.

Because a basic midamble sign indicating number is adopted in each sub-district, the channel estimation window that obtains is limited, makes each channel estimation window general simultaneously corresponding with a plurality of channel codes, and these channel codes belong to same walsh branch.Cause under the situation of variable Rate, after receiving terminal obtains channel estimation window, can not locate the channel code of actual transmission exactly, thereby brought difficulty for the realization of Multiuser Detection.

Summary of the invention

In view of this, main purpose of the present invention is to provide a kind of code channel detection method, can determine the channel estimation window of activation more accurately, and more accurate locating channel sign indicating number is realized Multiuser Detection more reliably.

The method that a kind of code channel that proposes based on above-mentioned purpose the present invention detects is applied to have in the code division multiple access system of unique corresponding relation between each channel estimation window and each channel code, comprising:

A) after receiver received signal, each the basic midamble sign indicating number that adopts when sending according to system carried out channel estimating, obtains the channel response of each basic midamble sign indicating number correspondence;

All channel responses that b1) will obtain are divided into a plurality of channel estimation windows according to window length;

B2) calculate the window power of each channel estimation window;

B3) according to the definite channel estimation window that activates of each window power;

B4) each that determine according to the corresponding relation determining step b3 of channel estimation window and channel code activates the corresponding channel code of channel estimation window;

B5) whether there is the walsh branch of coincidence to exist in the channel code according to the activation channel estimation window correspondence of determining among the determining step b3 of walsh branch of channel code,, then enters step b6 if having; If no, then the determined activation channel estimation window of determination step b3 is all accurate;

B6) be subordinated in the described activation channel estimation window of walsh branch of same coincidence and further determine the real channel estimation window that activates;

C) according to the definite corresponding activated code channel of channel estimation window that activates of the corresponding relation of channel estimation window and channel code;

D) utilize activated code channel to carry out Multiuser Detection.

The described step b3 of this method comprises: whether the ratio of maximal window power of judging the window power of each channel estimation window and this window is more than or equal to the window power ratio thresholding that sets in advance, if judge that then this window is the channel estimation window of initial activation; Otherwise, judge that this window is unactivated channel estimation window.

The described step b3 of this method comprises: whether the ratio of noise power of judging the window power of each channel estimation window and receiving terminal is more than or equal to the signal-noise ratio threshold that sets in advance, if judge that then this window is the channel estimation window of initial activation; Otherwise, judge that this window is unactivated channel estimation window.

The described step b6 of this method comprises:

A. list preliminary activation window with channel code correspondence in each walsh branch that overlaps characteristic, result of calculation according to window power among the step b2, select the activation window that each overlaps window power in walsh branch or signal to noise ratio maximum, determine that each overlaps channel code residing position in its walsh branch that maximum power in walsh branch or signal to noise ratio activate the window correspondence;

B. write down the channel estimation window of this position;

C. remove all roots and the pairing preliminary activation window of subdirectory of this position correspondence;

D. other sub-branch arranged side by side in the coincidence walsh branch at this place, position is carried out the walsh repeatability and judge,, then write down activation windows all in these sub-branches arranged side by side if other sub-branch arranged side by side does not have walsh to overlap situation; Otherwise, execution in step E;

E. write down all preliminary activation windows in the sub-sub-branch that does not have the walsh coincidence, enter steps A.

Further comprise behind the described channel estimation process of this method step a: channel estimation results is carried out the channel estimating reprocessing.

The described channel estimating reprocessing of this method is interference-cancellation process or noise reduction process or the combination of the two.

From above as can be seen, code channel detection method provided by the invention, taken into full account the inaccuracy of the channel estimating that causes because of factor such as adjacent area interference of cross-correlation between the basic midamble sign indicating number and receiving terminal and noise, carrying out further walsh branch on the basis of the preliminary activation estimating window collection of determining overlaps and judges, thereby obtain activating more accurately the estimating window collection, and, utilize these activated code channels to go to carry out Multiuser Detection again with the corresponding activated code channel collection that obtains of these activation estimating window collection with its channel code.

Description of drawings

Fig. 1 is the many code channels method of salary distribution under default mode, the K=16 situation;

Fig. 2 carries out the schematic flow sheet that code channel detects for the receiving terminal of preferred embodiment of the present invention;

Fig. 3 carries out the schematic flow sheet that activated code channel detects in the code channel testing process for receiving terminal;

Fig. 4 determines to overlap the schematic flow sheet that walsh branch activates window in the activated code channel testing process.

Embodiment

The present invention is further described in more detail below in conjunction with drawings and the specific embodiments.

In another piece name of submitting to simultaneously with the present invention is called the patent application of " a kind of code channel distribution method ", a kind of code channel allocative decision based on a plurality of basic midamble sign indicating numbers has been proposed.This scheme utilizes a plurality of basic midamble sign indicating numbers to construct more channel estimation window, and makes between channel estimation window and the channel code corresponding one by one.Referring to shown in Figure 1,, under the Kcell=16 situation, utilize 2 basic midamble sign indicating number m for adopting the default mode ₁And m ₂The code channel allocative decision schematic diagram of structure channel estimation window.Wherein, channel estimation window m ₁ ⁽¹⁾～m ₁ ⁽¹⁶⁾Distribute to spread spectrum coefficient respectively and be 16 channel code c ₁₆ ⁽¹⁾～c ₁₆ ⁽¹⁶⁾, channel estimation window m ₂ ⁽¹⁾～m ₂ ⁽⁸⁾Distribute to spread spectrum coefficient respectively and be 8 channel code c ₈ ⁽¹⁾～c ₈ ⁽⁸⁾, channel estimation window m ₂ ⁽⁹⁾～m ₂ ⁽¹²⁾Distribute to spread spectrum coefficient respectively and be 4 channel code c ₄ ⁽¹⁾～c ₄ ⁽⁴⁾, channel estimation window m ₂ ⁽¹³⁾～m ₂ ⁽¹⁴⁾Distribute to spread spectrum coefficient respectively and be 2 channel code c ₂ ⁽¹⁾～c ₂ ⁽²⁾, channel estimation window m ₂ ⁽¹⁵⁾Distribute to spread spectrum coefficient and be 1 channel code c ₁ ⁽¹⁾Thereby make between channel estimation window and the channel code corresponding one by one.

Based on above-mentioned code channel allocative decision, core concept of the present invention comprises: the channel estimating of a plurality of basic midamble sign indicating number that adopts when at first carrying out corresponding to transmission; Try to achieve all activated channel estimation window; Determine each uniquely according to the one-to-one relationship between channel estimation window and the channel code again and activate the pairing channel code of channel estimation window, also promptly determine activated code channel; Utilize these activated code channels to carry out Multiuser Detection at last.

Below in conjunction with accompanying drawing 2 to 4, the preferable implementation of the present invention is further specified.

Referring to shown in Figure 2, the code channel testing process of present embodiment comprises:

Step 201, the receiver received signal.

The signal of training sequence part correspondence is expressed as with formula (1) in received signal:

$e=\mathrm{\Σ}{m}_j^{\left(i\right)}*h_j^{\left(i\right)}+n---\left(1\right)$

Wherein, e represents received signal, m _j ⁽ⁱ⁾Expression is based on the training sequence of i displacement window of j basic midamble sign indicating number, h _j ⁽ⁱ⁾Expression is corresponding to the channel response of the transmission code channel of i displacement window of the basic midamble sign indicating number of j, and n represents the adjacent area interference and the thermal noise that receive.

Step 202, channel estimating and reprocessing thereof.

At first, receiving terminal utilizes each basic midamble sign indicating number to carry out channel estimating earlier.

The method of channel estimating is expressed as follows with formula (2):

$h_j^{\′\′}=\mathrm{ifft}(\mathrm{fft}\left(e\right)\·/\mathrm{fft}\left(m_j\right))---\left(2\right)$

Wherein, e represents received signal, m _jRepresent j basic midamble sign indicating number, h _j" expression is based on the original channel response of j basic midamble sign indicating number, and fft () represents Fourier transform, ifft () expression Fu Shi inverse transformation.

Then, to these original channel response carrying out channel estimating reprocessings.

The channel estimating reprocessing here can be based on the reprocessing of interference eliminated, also can be based on the reprocessing of noise reduction, or Interference Cancellation and noise reduction process are carried out simultaneously.

Concrete Interference Cancellation and noise reduction process process can adopt multiple scheme, such as: the method that can adopt the applicant in the Chinese patent application of first to file number is 03100670.1 patent " many yards collection of time slot CDMA system channel estimation methods ", to be adopted.

Here the post process channel response h that obtains of hypothesis _j' expression.

Step 203, activated code channel detects.

This step is subdivided into substep 301～306 again, referring to shown in Figure 3.

Step 301 is divided into a series of channel estimation windows to each channel estimation results after the reprocessing according to window length, and calculates the power of these channel estimation windows.

At first carry out window and cut apart, the window cutting procedure is expressed as follows with formula (3):

$h_j^{\left(i\right)}=h_j^{\′}(:,(i-1)*W+1:i*W)---\left(3\right)$

Wherein, h _j ⁽ⁱ⁾Implication and formula (1) in identical, expression is based on the channel response of i displacement window of j basic midamble sign indicating number, W represents that window is long.

Calculate the power of each channel estimation window that obtains after window is cut apart then, window power calculation process is expressed as follows with formula (4):

$P_j^{\left(i\right)}=\left|\right|{h_j^{\left(i\right)}\left|\right|}^2---\left(4\right)$

Wherein, h _j ⁽ⁱ⁾Implication and formula (1) in identical, expression is based on the channel response of i displacement window of j basic midamble sign indicating number, P _j ⁽ⁱ⁾The window power of representing this window.

302, the preliminary channel estimation window of determining activation.

The window power of each channel estimation window that calculates according to formula (4) adopts window power ratio criterion or signal-to-noise ratio (SNR) Criterion that all channel estimation windows are judged, keeps the channel estimation window that those satisfy threshold requirement, and their are formed the preliminary window collection that activates.

Wherein, window power ratio criterion is represented with formula (5):

$f\left(h_j^{\left(i\right)}\right)=\left\{\begin{array}{cc}1,& P_j^{\left(i\right)}/\max \left(P_j^{\left(i\right)}\right)\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H05169289320050524E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1\\ 0,& P_j^{\left(i\right)}/\max \left(P_j^{\left(i\right)}\right)<T_1\end{array}\right.---\left(5\right)$

Wherein, T ₁Expression window power ratio thresholding, f () represents activation primitive, and f ()=1 expression activation, f ()=0 expression is not activated.

From formula (5) as can be seen, if the window power P of a channel estimation window _j ⁽ⁱ⁾Maximal window power max (P with this sub-district _j ⁽ⁱ⁾) ratio more than or equal to thresholding T ₁, then this window is considered to be the channel estimation window of activation; Otherwise, be considered as un-activation.

Signal-to-noise ratio (SNR) Criterion is represented with formula (6)

$f\left(h_j^{\left(i\right)}\right)=\left\{\begin{array}{cc}1,& P_j^{\left(i\right)}/{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="H05169289320050524E000011.png"\; state="\{\{state\}\}">n</figure-callout>}}^2\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H05169289320050524E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_2\\ 0,& P_j^{\left(i\right)}/{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="H05169289320050524E000011.png"\; state="\{\{state\}\}">n</figure-callout>}}^2<T_2\end{array}\right.---\left(6\right)$

Wherein, σ _n ²The noise power of expression receiving terminal, T ₂The expression signal-noise ratio threshold, f () represents activation primitive, and f ()=1 expression activation, f ()=0 expression is not activated.

From formula (6) as can be seen, if the window power P of a channel estimation window _j ⁽ⁱ⁾With noise power σ _n ²Ratio more than or equal to thresholding T ₂, then this window is considered to be the channel estimation window of activation; Otherwise, be considered as not being activated.

In the reality, can select the definite channel estimation window that activates of any one mode of formula (5) and formula (6) expression as required.For the channel estimation window that prevents to activate is taken place by the situation of omission, can be with thresholding T ₁, T ₂Be provided with relatively lowly.

If can in above-mentioned testing process, guarantee the channel estimation window entirely accurate of detected activation, the preliminary activation window collection of determining in this step can be thought the final accurate activation window collection of determining, directly execution in step 305 is listed the activation window composition activation window collection that this step is determined.If can't guarantee entirely accurate or need further accurately to confirm that then further execution in step 303～304 accurately determines to activate the window collection.

Be to utilize channel code in the present embodiment, promptly the characteristic of walsh sign indicating number realizes that the preliminary activation window collection that step 302 is obtained is exactly determined, specifically as described in step 303～304.

Step 303 is carried out the repeatability judgement of walsh branch to the preliminary window collection that activates of step 302.

At first, the preliminary activation window collection that obtains according to step 302 is determined the channel code of wherein each channel estimation window correspondence.

Then, judge that according to the walsh branch of channel code the walsh branch whether coincidence is arranged in the channel code that tentatively activates the window correspondence exists, the code channel that is code channel and the bigger spread spectrum coefficient of being drawn by himself of certain littler spread spectrum coefficient exists simultaneously, if have the walsh of coincidence branch to exist, then enter step 304; Do not exist if overlap walsh branch, then change step 305 over to, judge that promptly the accurate window collection that activates equals preliminary activation window collection.

Step 304 is listed each walsh branch with coincidence characteristic, and determines the accurate activation window of each branch.

This step is subdivided into substep 401～407 again, referring to shown in Figure 4.

Step 401, list preliminary activation window with channel code correspondence in each walsh branch that overlaps characteristic, result of calculation according to window power in the step 301, select each and overlap the prominent preliminary activation window of window in walsh branch, determine that each overlaps channel code residing position in its walsh branch that maximum power in walsh branch tentatively activates the window correspondence.

Step 402 writes down the channel estimation window of this position.

Step 403 is removed all roots and the subdirectory of this position correspondence, i.e. the pairing preliminary activation window of higher level's catalogue and subprime directory.

Step 404 is carried out the walsh repeatability to other sub-branch arranged side by side in the coincidence walsh branch at this place, position and is judged.

Step 405 if other sub-branch arranged side by side does not have walsh to overlap situation, then writes down preliminary activation windows all in these sub-branches arranged side by side.

Step 406～407 if other sub-branch arranged side by side also has walsh to overlap situation, are then write down all preliminary activation windows in those sub-sub-branches that do not have the walsh coincidence earlier; The sub-sub-branch that will have walsh to overlap then is used as new coincidence walsh branch and handles.Promptly change step 401 over to.

Step 305, all activated window that above-mentioned deterministic process is obtained is combined into accurate activation window collection.

Step 306 is listed this and is accurately activated the channelization code set that window set pair is answered, and promptly obtains the code channel collection that activates, enters step 204.Wherein each activation window and certain channel code are one to one.

The activated code channel collection that step 204, utilization obtain above carries out Multiuser Detection.

Be example with up three users below, the specific implementation process of the invention described above be described:

Suppose to adopt code channel distribution method shown in Figure 1, user 1 distributes code channel m ₂ ⁽¹⁾-c ₈ ⁽¹⁾, m ₁ ⁽³⁾-c ₁₆ ⁽³⁾User 2 distributes code channel m ₂ ⁽¹⁰⁾-c ₄ ⁽²⁾User 3 distributes code channel m ₁ ⁽¹⁰⁾-c ₁₆ ⁽¹⁰⁾

After carrying out the window activation, judge that by step 302 the preliminary activation window collection that obtains is: { m ₁ ⁽²⁾, m ₁ ⁽³⁾, m ₁ ⁽⁶⁾, m ₁ ⁽¹⁰⁾, m ₂ ⁽¹⁾, m ₂ ⁽¹⁰⁾, m ₂ ⁽¹¹⁾, m ₂ ⁽¹³⁾.

By step 303,, obtain these and activate the channelization code set that window set pairs answer and be: { c according to the one-to-one relationship between pre-assigned channel estimation window and the channel code ₁₆ ⁽²⁾, c ₁₆ ⁽³⁾, c ₁₆ ⁽⁶⁾, c ₁₆ ⁽¹⁰⁾, c ₈ ⁽¹⁾, c ₄ ⁽²⁾, c ₄ ⁽³⁾, c ₂ ⁽¹⁾.

By step 304, from the concentrated { c of branch that finds of the channel code that obtains ₂ ⁽¹⁾, c ₄ ⁽²⁾, c ₈( ¹⁾, c ₁₆ ⁽²⁾, c ₁₆ ⁽³⁾, c ₁₆ ⁽⁶⁾Overlap; { the c of branch ₄ ⁽³⁾, c ₁₆ ⁽¹⁰⁾Overlap.

By step 401～403, to { the c of branch ₂ ⁽¹⁾, c ₄ ⁽²⁾, c ₈ ⁽¹⁾, c ₁₆ ⁽²⁾, c ₁₆ ⁽³⁾, c ₁₆ ⁽⁶⁾Ask maximal window power position, the channel estimation window that obtains maximal window power is m ₂ ⁽¹⁰⁾-c ₄ ⁽²⁾, remove all higher levels and the subprime directory of this position correspondence, m is described ₂ ⁽¹³⁾-c ₂ ⁽¹⁾, m ₁ ⁽⁶⁾-c ₁₆ ⁽⁶⁾Do not exist;

By step 404, again to the { c of sub-branch ₈ ⁽¹⁾, c ₁₆ ⁽²⁾Judge, obtain m according to maximal window power position ₂ ⁽¹⁾-c ₈ ⁽¹⁾To { the c of branch ₄ ⁽³⁾, c ₁₆ ⁽¹⁰⁾Judge, obtain m according to maximal window power position ₁ ⁽¹⁰⁾-c ₁₆ ⁽¹⁰⁾

According to above-mentioned judgement, the sign indicating number collection that obtains participating in Multiuser Detection at last is { m ₂ ⁽¹⁾-c ₈ ⁽¹⁾, m ₁ ⁽³⁾-c ₁₆ ⁽³⁾, m ₂ ⁽¹⁰⁾-c ₄ ⁽²⁾, m ₁ ⁽¹⁰⁾-c ₁₆ ⁽¹⁰⁾.

Code channel detection method of the present invention both had been applicable to that the cross-correlation performance of basic midamble sign indicating number was not good situation, also was applicable to the adjacent area interference and the very big situation of noise of receiving terminal.

The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. the method that code channel detects is applied to have in the code division multiple access system of unique corresponding relation between each channel estimation window and each channel code, it is characterized in that, comprising:

A) after receiver received signal, each the basic midamble sign indicating number that adopts when sending according to system carried out channel estimating, obtains the channel response of each basic midamble sign indicating number correspondence;

All channel responses that b1) will obtain are divided into a plurality of channel estimation windows according to window length;

B2) calculate the window power of each channel estimation window;

B3) according to the definite channel estimation window that activates of each window power;

B4) each that determine according to the corresponding relation determining step b3 of channel estimation window and channel code activates the corresponding channel code of channel estimation window;

B5) whether there is the walsh branch of coincidence to exist in the channel code according to the activation channel estimation window correspondence of determining among the determining step b3 of walsh branch of channel code,, then enters step b6 if having; If no, then the determined activation channel estimation window of determination step b3 is all accurate;

B6) be subordinated in the described activation channel estimation window of walsh branch of same coincidence and further determine the real channel estimation window that activates;

C) according to the definite corresponding activated code channel of channel estimation window that activates of the corresponding relation of channel estimation window and channel code;

D) utilize activated code channel to carry out Multiuser Detection.

2. method according to claim 1, it is characterized in that, described step b3 comprises: whether the ratio of maximal window power of judging the window power of each channel estimation window and this channel response is more than or equal to the window power ratio thresholding that sets in advance, if then judge the channel estimation window of this window for activating; Otherwise, judge that this window is unactivated channel estimation window.

3. method according to claim 1, it is characterized in that, described step b3 comprises: whether the ratio of noise power of judging the window power of each channel estimation window and receiving terminal is more than or equal to the signal-noise ratio threshold that sets in advance, if then judge the channel estimation window of this window for activating; Otherwise, judge that this window is unactivated channel estimation window.

4. method according to claim 1 is characterized in that, described step b6 comprises:

A. list preliminary activation window with channel code correspondence in each walsh branch that overlaps characteristic, result of calculation according to window power among the step b2, select the activation window that each overlaps window power in walsh branch or signal to noise ratio maximum, determine that each overlaps channel code residing position in its walsh branch that maximum power in walsh branch or signal to noise ratio activate the window correspondence;

B. write down the channel estimation window of this position;

C. remove all roots and the pairing preliminary activation window of subdirectory of this position correspondence;

D. other sub-branch arranged side by side in the coincidence walsh branch at this place, position is carried out the walsh repeatability and judge,, then write down activation windows all in these sub-branches arranged side by side if other sub-branch arranged side by side does not have walsh to overlap situation; Otherwise, execution in step E;

E. write down all preliminary activation windows in the sub-sub-branch that does not have the walsh coincidence, enter steps A.

5. method according to claim 1 is characterized in that, further comprises behind the described channel estimation process of step a: channel estimation results is carried out the channel estimating reprocessing.

6. method according to claim 5 is characterized in that, described channel estimating reprocessing is interference-cancellation process or noise reduction process or the combination of the two.

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