CN101388683A - Code channel detection method in CDMA system - Google Patents

Abstract

The invention discloses a method for detecting code channels in a cdma system. The method comprises: firstly, estimating communication channels of a training sequence which receives user data, secondly, determining corresponding training sequence deviation according to the communication channel estimating results, finding out corresponding spread-spectrum codes according to configuration information, thirdly, using each spread-spectrum code in the corresponding spread-spectrum codes of the training sequence deviation to de-extend received data sections which are corresponding to taps, obtaining symbol energy, fourthly, sequencing the symbol energy according to size, wherein same with the symbol energy value which is de-extended by a minimum spread-spectrum factor, a spread-spectrum code which is corresponding to the maximum spread-spectrum factor in all spread-spectrum factors is the spread-spectrum code which is used by users. The method uses corresponding relation between the training sequence deviation and a spread-spectrum code set and de-extension of received data to realize blind detection of occupied code channel information of the users, and the transfer of the code channel information which is used by the users through a signaling message is avoided, hollow port resources are saved for systems, and the realizing complexity is small, the use is convenient, and the burden of a base station controller is lightened.

Description

The method that code channel detects in a kind of code division multiple access system

Technical field

The present invention relates to communication technique field, relate in particular to the method that code channel detects in a kind of TD SDMA (TD-SCDMA) system.

Background technology

TD-CDMA (time division CDMA, particularly TD-SCDMA) is based on the 3-G (Generation Three mobile communication system) of time division duplex (TDD), wherein relates to a lot of key technologies, as Fast Channel estimation technique, associated detection technique, intelligent antenna technology etc.Use associated detection technique in the TD-SCDMA system, can effectively suppress multiple access and disturb (MAI) and intersymbol interference (ISI), the basis that these key technologies are used will be known the code channel of CU in the system, i.e. channel code of Shi Yonging exactly.

In the TD-SCDMA system, the multi-plot joint detection algorithm need know that adjacent sub-district is in the spreading code of the portable terminal use of state of activation, the just inhibition that can disturb.Present way is that each adjacent sub-district is passed to this cell base station with the information of the excited users in the own sub-district by signaling, has increased signaling consumption.In high speed uplink packet inserts (HSUPA) because UE can change up spreading factor and code channel automatically at different time slots, like this since the very difficult spreading factor and the spreading code that obtains adjacent sub-district cellphone subscriber by means of signaling in base station of this sub-district.

Summary of the invention

Technical problem to be solved by this invention provides the method that code channel detects in a kind of code division multiple access system.

For solving the problems of the technologies described above, the present invention is achieved by the following technical solutions:

The method that code channel detects in a kind of code division multiple access system may further comprise the steps:

A: the training sequence that will receive user data carries out channel estimating;

B: according to channel estimation results, determine corresponding training sequence deviation (Midamble shift), and find corresponding spreading code class according to the configuration information of Midamble shift;

C: respectively the reception data segment of tap correspondence is carried out despreading with each spreading code in the spreading code class of Midamble shift correspondence, obtain symbol energy;

D: symbol energy is sorted the spreading code that the spreading code of that maximum spreading factor correspondence uses for the user in all spreading factors the same with the symbol energy values of minimal frequency spreading factor despreading according to its size.

Wherein, training sequence can be expressed as described in the step a:

e＝Gh+n

Wherein, the G matrix is the ring shift right matrix that is made of a basic Midamble sign indicating number, and h is user's a channel impulse response, and n is a white Gaussian noise;

Obtaining channel estimating is: $\hat{h}={\left(G^{*T}G\right)}^{-1}{G}^{*T}e$

Because the G matrix is the ring shift right matrix, so obtain

$\hat{h}=G^{-1}e.$

Wherein, configuration information according to Midamble shift described in the step b finds corresponding spreading code class to be specially: under Midamble sign indicating number default (default) method of salary distribution, midamble sign indicating number shift and the configuration mode of channel code under the different K values situation have been provided according to agreement, find out the corresponding spreading code class of midamble sign indicating number shift according to this corresponding relation, wherein K is the maximum number of available training sequence code in the time slot.

Wherein, among the step c reception data segment of tap correspondence being carried out despreading is specially: the transmission data vector of user k is

d _k＝(d ₁，d ₂，…，d _N)

Wherein N represents the symbolic number of each data block in each code channel;

Through spreading code c _k=(c ₁, c ₂..., c _Q)

Behind the spread spectrum, become and expand signal S _k=dc=(S ₁, S ₂..., S _NQ)

Obtaining symbol energy is:

${\mathrm{SE}}_{\mathrm{Qi}}=S{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{S}_k{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{d}_k{c}_s{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{d}_k\underset{l=1}{\overset{16/\mathrm{Qi}}{\mathrm{\Σ}}}{c}_{s,l}{c}_{r,l}^{*}$

Wherein Q represents scrambler cycle, c _rThe spreading code that expression receives, c _sThe spreading code of expression emission, ^*The expression conjugation.

The present invention has following beneficial effect:

Adopt the despreading that utilizes the relation of minamble shift and spreading code set correspondence and receive data of the present invention, finish the scheme of the detection of the spreading code that user uplink is used, can realize the blind Detecting of CU code channel information.Avoided like this using code channel information by signaling transmission user, for system has saved valuable interface-free resources, this scheme implementation complexity is little, easy to use, has alleviated the burden of base station controller, the simple detection of finishing code channel that the user uses.

Description of drawings

Fig. 1 is the default corresponding relation figure of up channel sign indicating number and up midamble sign indicating number;

Fig. 2 is the inventive method flow chart.

Embodiment

Core concept of the present invention: go out the code channel situation that adjacent sub-district UE uses by receiving the Midamble sequencal estimation that contains in the user data.At first carry out adjacent cell channel and estimate, utilize the corresponding relation of up channel sign indicating number and midamble intersymbol, and in conjunction with to the user data despreading, the mode that varies in size according to the symbol energy of despreading detects the method that the user uses code channel.If the whole network uses this corresponding relation, this cell base station does not need process Iub (logic interfacing between RNC and the Node B) oral instructions to pass this information, just can realize the detection of the spreading code of the up use of portable terminal that adjacent sub-district is activated.

The present invention is described in further detail below in conjunction with drawings and Examples:

From the data that the base station receives, isolate the training sequence received signal, finish channel estimating and channel post-processing adjacent users of all cells.The training sequence that receives can be expressed as

e＝Gh+n (1)

Wherein, the G matrix is the ring shift right matrix that is made of a basic Midamble sign indicating number (training sequence that use adjacent sub-district), and h is user's a channel impulse response, and n is a white Gaussian noise.Finish the maximal possibility estimation of channel impulse response h with formula (2)

Promptly

$\hat{h}={\left(G^{*T}G\right)}^{-1}{G}^{*T}e---\left(2\right)$

Because the G matrix is the ring shift right matrix, has

$\hat{h}=G^{-1}e---\left(3\right)$

Therefore, utilize the cyclic shift characteristic of matrix, above-mentioned channel estimating can adopt fast fourier transform/inverse-Fourier transform (FFT/IFFT) fast method realization fast, thereby has improved arithmetic speed significantly.

As shown in the formula (4):

$\hat{h}=\mathrm{ifft}(\mathrm{fft}\left(e\right)/\mathrm{fft}\left(m\right))---\left(4\right)$

According to channel estimating

The result, have the window of tap to be the Midamble shift of activation, can know the operating position of Midamble shift.

In the foundation Midamble sign indicating number default method of salary distribution, provided midamble sign indicating number shift and the configuration mode of channel code under the different K values situation in the agreement 25.221, found out a corresponding channel code class of midamble sign indicating number shift (also claiming the spreading code class) according to this corresponding relation.

Wherein, the K value is the maximum number of available Midamble sign indicating number in the time slot.

Be example with the K=8 situation below, under other K value situations, the method that code channel detects is identical.Specifically introduce the process of estimating code channel according to the configuration information of midamble shift.Under the Midamble sign indicating number default method of salary distribution, the corresponding relation of up channel sign indicating number and up midamble sign indicating number has the default corresponding relation (K=8) of following up channel sign indicating number class and up midamble sign indicating number as shown in Figure 1 like this, as table 1:

Table 1

Channel code is directly to define with the code tree that generates ovsf code, each level in the code tree all correspondence a spreading factor Q.TD-SCDMA system requirements:, must guarantee that so this branch left side all is not used up to all sign indicating numbers of root node, and the sign indicating number of these all subtrees of branch the right can not be used again if a certain branch of certain one-level is used in the code tree.According to such characteristics of system, in the table 1 in each up channel sign indicating number class, have only a spreading factor to be used in the above, the different spreading codes of the same spread factor can be used simultaneously.Therefore, in the spreading code class of same midamble shift correspondence, have only a spreading code to be used by the user of current time slots.

Because spreading code is elongated in the TD-SCDMA system, therefore to carry out preliminary treatment to each user's spreading code.With spreading code expand to 16 long.If Q=2 then repeats spreading code 8 times; If Q=4 then repeats spreading code 4 times, and the like.Spreading code expansion cross-reference, as shown in table 2:

Table 2

If know the spreading code class of midamble shift correspondence, respectively tap corresponding data section is carried out despreading with each spreading code in the same spreading code class then, calculate possible symbol energy.According to the symbol energy that despreading obtains, determine again the spreading code judgement of maximum correspondence is the spreading code of this tap correspondence.

Transmitting terminal, the transmission data vector of user k is

d _k＝(d ₁，d ₂，…，d _N) (5)

Wherein N represents the symbolic number of each data block in each code channel.

Through spreading code c _k=(c ₁, c ₂..., c _Q) (6)

Behind the spread spectrum, become and expand signal

S _k＝d _c＝(S ₁，S ₂，...，S _NQ) (7)

With all spreading codes in the spreading code class of midamble shift correspondence, the reception data segment of tap correspondence is carried out despreading, obtain symbol energy, use SE _Qi(symbol energy) expression, i represents the value of Q.

Carry out despreading to received signal

${\mathrm{SE}}_{\mathrm{Qi}}={\mathrm{Sc}}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{S}_k{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{d}_k{c}_s{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{d}_k\underset{l=1}{\overset{16/\mathrm{Qi}}{\mathrm{\Σ}}}{c}_{s,l}{c}_{r,l}^{*}---\left(8\right)$

Wherein Q represents scrambler cycle, c _rThe spreading code that expression receives, c _sThe spreading code of expression emission, ^*The expression conjugation.The symbol lengths of despreading can be less than NQ, and data length is big more, and reliability is high more.

By table 1, table 2 as can be known, the code word in the spreading code class of each midamble shift correspondence has such feature, expansion can generate the spreading code of little spreading factor and the big identical code word of spreading factor through simply duplicating again.

In conjunction with following formula, so the SE that the big spreading factor that receiving terminal is launched with little spreading factor demodulation transmitting terminal obtains is just arranged _{Little Q}The SE that obtains with the spreading factor demodulation of using with actual transmission _{Big Q}Be the same, otherwise it is but quite different, because the statistical property of symbol of emission is that 0.5 probability is { 0, send at random in the 1} set, two adjacent symbols can be different, therefore when transmitting terminal uses little spreading factor to launch, when coming demodulation with big spreading factor, symbol energy has loss, SE _{Big Q}Less than SE _{Little Q}

Spreading code class with first midamble shift correspondence is an example:

Suppose that the spreading factor that the user uses is 8, so just have SE ₁₆＜SE ₈=SE ₄=SE ₂=SE ₁

Suppose that the spreading factor that the user uses is 4, so just have SE ₁₆≤ SE ₈＜SE ₄=SE ₂=SE ₁

Suppose that the spreading factor that the user uses is 16, so just have SE ₁₆=SE ₈=SE ₄=SE ₂=SE ₁

Thus, in despreading, to SE _QiSort and the symbol energy values of minimal frequency spreading factor despreading SE ₁That maximum spreading factor is exactly the spreading factor that user's transmitting terminal uses in value all spreading factors equally, and the spreading code that uses this spreading factor in the midamble of correspondence shift spreading code class is exactly the channel code that the user uses.

When network was set up in the system, the concrete steps of code assignment scheme were consulted shown in Figure 2:

Step 201: the training sequence that will receive data proposes to do channel estimating;

The maximal possibility estimation of channel impulse response, $\hat{h}=G^{-1}e;$

Step 202: according to channel estimating

The result, determine the pairing Midamble shift of theactivewindow.There is the window of tap to be the Midamble shift of activation, can arrives the operating position of Midamble shift; Under the Midamble sign indicating number default method of salary distribution, provided midamble sign indicating number shift and the configuration mode of channel code under the different K values situation according to agreement, find out a corresponding channel code class of midamble sign indicating number shift according to this corresponding relation;

Step 203: respectively tap corresponding data section is carried out despreading with each spreading code in the spreading code class of same midamble shift correspondence, calculate possible symbol energy, be designated as SE _Qi

Step 204: according to size, to SE _QiSort and the symbol energy values of minimal frequency spreading factor despreading SE ₁That maximum spreading factor is exactly the spreading factor that user's transmitting terminal uses in all the same spreading factors, and the spreading code that uses this spreading factor in the midamble of correspondence shift spreading code class is exactly the channel code that the user uses; Return step 202, up to finishing the detection that user under all Midamble shift uses channel code.

Adopt the despreading that utilizes the relation of minamble shift and spreading code set correspondence and receive data of the present invention, finish the scheme of the detection of the spreading code that user uplink is used, can realize the blind Detecting of CU code channel information.Avoided like this using code channel information, for system has saved valuable interface-free resources by signaling transmission user.

The present invention can also be used for all cdma systems of moving communicating field, particularly TDD-CDMA system and all SCDMA systems.

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

Claims (4)

1, the method that code channel detects in a kind of code division multiple access system is characterized in that, may further comprise the steps:

A: the training sequence that will receive user data carries out channel estimating;

B: according to channel estimation results, determine corresponding training sequence deviation, and find corresponding spreading code class according to the configuration information of training sequence deviation;

C: respectively the reception data segment of tap correspondence is carried out despreading with each spreading code in the spreading code class of training sequence deviation correspondence, obtain symbol energy;

D: symbol energy is sorted the spreading code that the spreading code of that maximum spreading factor correspondence uses for the user in all spreading factors the same with the symbol energy values of minimal frequency spreading factor despreading according to its size.

2, the method that code channel detects in the code division multiple access system as claimed in claim 1 is characterized in that training sequence described in the step a can be expressed as:

e＝Gh+n

Wherein, the G matrix is the ring shift right matrix that is made of a basic training sequences sign indicating number, and h is user's a channel impulse response, and n is a white Gaussian noise;

Obtaining channel estimating is: $\hat{h}={\left(G^{*T}G\right)}^{-1}{G}^{*T}e$

Because the G matrix is the ring shift right matrix, so obtain

$\hat{h}=G^{-1}e.$

3, the method that code channel detects in the code division multiple access system as claimed in claim 2, it is characterized in that, configuration information according to training sequence deviation described in the step b finds corresponding spreading code class to be specially: under the training sequence code default distributing mode, provide training sequence code skew and the configuration mode of channel code under the different K values situation according to agreement, find out training sequence code according to this corresponding relation and be offset corresponding spreading code class, wherein K is the maximum number of available training sequence code in the time slot.

4, the method that code channel detects in the code division multiple access system as claimed in claim 3 is characterized in that, among the step c reception data segment of tap correspondence is carried out despreading and be specially: the transmission data vector of user k is

d _k＝(d ₁，d ₂，…，d _N)

Wherein N represents the symbolic number of each data block in each code channel;

Through spreading code c _k=(c ₁, c ₂..., c _Q)

Behind the spread spectrum, become and expand signal S _k=dc=(S ₁, S ₂..., S _NQ)

Obtaining symbol energy is:

${\mathrm{SE}}_{\mathrm{Qi}}=S{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{S}_k{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{d}_k{c}_s{c}_r^{*}$

$=\underset{k=1}{\overset{\mathrm{NQ}}{\mathrm{\Σ}}}{d}_k\underset{l=1}{\overset{16/\mathrm{Qi}}{\mathrm{\Σ}}}{c}_{s,l}{c}_{r,l}^{*}$

Wherein Q represents scrambler cycle, c _rThe spreading code that expression receives, c _sThe spreading code of expression emission, ^*The expression conjugation.

Images