CN101741773B - Method and device for channel estimation of terminal in time division synchronous code division multiple access system - Google Patents

Abstract

The invention provides a method and a device for channel estimation of a terminal in a time division synchronous code division multiple access system. The system comprises the following steps: determining a Midamble code for calculating a channel estimation post-processing noise threshold; removing reconstructed signals of each cell from data received_midamble in the Midamble code to obtain relative clean data received_midamble_net of which the reconstructed signals of all cells are removed; obtaining the channel estimation post-processing threshold by the data received_midamble_net and the determined Midamble code; and calculating channel estimation values of each cell according to the data received_midamble, the Midamble code of each cell and the obtained channel estimation post-processing threshold. The method and the device improve the accuracy of the channel estimation of the terminal in an environment of same frequency interference so as to improve the demodulation performance of the terminal.

Description

Terminal channel is estimated in the TD-SCDMA system method and device

Technical field

The present invention relates to communication technical field, relate in particular to terminal channel is estimated in a kind of TD-SCDMA (Time DivisionSynchronous Code Division Multiple Access, TD SDMA access) system method and device.

Background technology

In existing TD-SCDMA system, in order to improve the availability of frequency spectrum, identical networking becomes a kind of effective solution, but identical networking has also brought co-channel interference when improving the availability of frequency spectrum.Co-channel interference namely is contiguous co-frequency cell because use identical carrier frequency to carry out interference between different districts user that transfer of data causes, and co-channel interference can make systematic function descend.

When inter-frequency networking, the signal of adjacent cell is on different frequencies, can be used as out-of-band noise and process, and only considers other users' of this residential quarter the interference to this user, only need to include the user of this residential quarter in joint-detection, only need to estimate the channel estimating of this residential quarter.

When identical networking, because the signal of adjacent cell and the signal of this residential quarter are on identical frequency, can cause co-channel interference, simultaneously, because the spreading code of TD-SCDMA system is shorter, only have 16 chips, spreading gain is smaller, and it is improper that the signal of adjacent cell still is used as noise processed, should be as other users that process this residential quarter, to also include joint-detection in the user of frequently adjacent cell, namely adopt multi-cell joint detection during identical networking.

Usually the computational methods of channel estimating reprocessing thresholding have two kinds:

(1) based on the maximum value calculation thresholding of channel estimating tap, usually maximum be multiply by one less than 1 coefficient, the result is as thresholding, and the advantage of the method is simple, if but the setting of thresholding coefficient is less, when signal to noise ratio is not high, partial noise can be declared into signal, too high if the thresholding coefficient arranges, when signal master footpath is stronger, weak footpath can be judged to into noise, causes terminal demodulation performance decline under the multi-path environment;

(2) based on the noise calculation thresholding, normally the noise average be multiply by one greater than 1 coefficient, the result is as thresholding, but the judgement of noise itself also needs certain foundation, normally judges noise according to the thresholding in (1), if the thresholding in (1) is unreasonable, the calculating of noise is just inaccurate, cause the noise gate set point undesirable, particularly under the multi-path environment of strong co-channel interference, can affect to a great extent terminal demodulation performance.

Summary of the invention

In order to address the above problem, the purpose of this invention is to provide terminal channel is estimated in a kind of TD-SCDMA system method and device, improve the channel estimation accuracy of terminal under the co-channel interference environment, thereby can improve the demodulation performance of terminal.

In order to achieve the above object, the invention provides the method that terminal channel is estimated in a kind of TD-SCDMA system, described method comprises:

Step 1, determine the Midamble code that channel estimating reprocessing Noise gate limit value calculates;

Step 2, the data received_midamble in the described Midamble code removed the signal of each residential quarter of reconstruct, obtain removing the data received_midamble_net behind the signal of all residential quarter reconstruct;

Step 3, with the described Midamble code of determining in the described data received_midamble_net that exports in the described step 2 and the described step 1, obtain channel estimating reprocessing threshold value;

Step 4, with the Midamble code of described data received_midamble, each residential quarter, and the channel estimating reprocessing threshold value that obtains of described step 3 is calculated the channel estimation value of each residential quarter.

Preferably, described method also comprises:

Step 5, repeat described step 2 to the process of described step 4, eliminate and all finish until set the interference of progression, export last channel estimation value.

Preferably, described step 1 is specially:

Determined the Midamble code of calculating noise threshold value by Cell searching, Cell searching calculates the energy of each residential quarter, chooses the corresponding Midamble code in the most weak residential quarter of energy, as the Midamble code that calculates channel estimating reprocessing Noise gate limit value; Perhaps

By measuring the Midamble code of determining the calculating noise threshold value, choose a Midamble code that the residential quarter is corresponding by measuring in the residual set of determining, as the Midamble code of subsequent calculations channel estimating reprocessing Noise gate limit value.

Preferably, if when the first order is processed, the signal of described all the residential quarter reconstruct in the described step 2 is zero.

Preferably, described step 3 is specially:

Described Midamble code with determining in the described data received_midamble_net of described step 2 and the described step 1 by the Steriner channel estimator, obtains 8 channel estimation windows totally 128 noise path;

128 all noise path energy are averaging, and as system's average noise, pass through the weighting of thresholding coefficient as channel estimating reprocessing thresholding again.

Preferably, described step 3 is specially:

Remove the tap of an energy maximum in each channel estimation window, and 120 noise path energy that other are all are averaging, as system's average noise;

By the thresholding coefficient to the average noise weighting of described system as channel estimating reprocessing threshold value.

The present invention also provides the device that terminal channel is estimated in a kind of TD-SCDMA system, and described device comprises:

Determination module is used for the Midamble code of determining that channel estimating reprocessing Noise gate limit value calculates;

The first computing module is used for the data received_midamble of described Midamble code is removed the signal of each residential quarter of reconstruct, obtains removing the data received_midamble_net behind the signal of all residential quarter reconstruct;

The second computing module is used for obtaining channel estimating reprocessing threshold value according to described data received_midamble_net and described Midamble code;

Channel estimation module is used for the Midamble code according to described data received_midamble, each residential quarter, and the described channel estimating reprocessing threshold value that obtains, and calculates the channel estimation value of each residential quarter.

Preferably, described device also comprises:

Circulation module is used for controlling described the first computing module, the second computing module and channel estimation module and opens operation, all finishes until set the interference elimination of progression, exports last channel estimation value.

At least one technical scheme in the technique scheme has following beneficial effect: improved the channel estimation accuracy of terminal under the co-channel interference environment, thereby can improve the demodulation performance of terminal.

Description of drawings

Fig. 1 is the method flow diagram that terminal channel is estimated in the TD-SCDMA system among the present invention;

Fig. 2 is the structure drawing of device that terminal channel is estimated in the TD-SCDMA system among the present invention.

Embodiment

For the purpose, technical scheme and the advantage that make the embodiment of the invention is clearer, below in conjunction with embodiment and accompanying drawing, the embodiment of the invention is done in further detail explanation.At this, illustrative examples of the present invention and explanation are used for explanation the present invention, but not as a limitation of the invention.

The present embodiment with

K=8 is example, and wherein, P=128 is basic Midamble code length, and W=16 is channel estimation window length; Interference Cancellation is 4 grades, 3 adjacent cells.

Referring to Fig. 1, be the method flow diagram that terminal channel in the TD-SCDMA system among the present invention is estimated, the concrete steps of the method are as follows:

Step 101, determine the Midamable code that channel estimating reprocessing Noise gate limit value calculates;

Namely behind starting up of terminal, then the beginning cell search process is calculated the energy of each residential quarter, and is chosen the corresponding Midamble code in the most weak residential quarter of energy, as the Midamble code that calculates channel estimating reprocessing Noise gate limit value;

Perhaps also can from the residual set that measuring process is determined, choose a corresponding Midamble code in residential quarter, as the Midamble code of subsequent calculations channel estimating reprocessing Noise gate limit value;

Step 102, the data received_midamble in the Midamble code removed the signal of each residential quarter of reconstruct, obtain removing the data received_midamble_net of the relative clean behind the signal of all residential quarter reconstruct;

Deduct the signal of each residential quarter of reconstruct with the partial data received_midamble in the Midamble code that receives.But when the first order is processed, owing to there not being reconstruction signal, think the signal of reconstruct for complete zero, obtain removing data behind the signal of all residential quarter reconstruct as output;

Take the time domain Interference Cancellation as example, the processing method of each residential quarter of every one-level is as follows:

$\mathrm{recevied}\_\mathrm{midamble}\_\mathrm{net}=\mathrm{recevied}\_\mathrm{midamble}-\underset{\mathrm{allcell}}{\mathrm{\Σ}}\mathrm{covn}(\mathrm{channel},\mathrm{basic}\_\mathrm{midamble})$

Wherein, received_midamble_net is Interference Cancellation data afterwards;

Recevied_midamble is the partial data among the Midamble that receives;

Channel is the result of channel estimating reprocessing;

Basic_midamble is the basic Midamble code of each residential quarter;

$\underset{\mathrm{allcell}}{\mathrm{\Σ}}\mathrm{covn}(\mathrm{channel},\mathrm{basic}\_\mathrm{midamble})$ Be time domain with the Midamble part signal of all residential quarters of channel estimation value and basic Midamble code convolution reconstruct and, channel estimating channel initial value when the first order all is zero.

The Midamble code of determining in step 103, the data received_midamble_net that uses output in the step 102 and the step 101 obtains channel estimating reprocessing threshold value;

Midamble code with determining in the data received_midamble_net that exports in the step 102 and the step 101 calculates 8 channel estimation windows totally 128 noise path by the Steiner channel estimator.128 all noise path energy are averaging, and as system's average noise, pass through the weighting of thresholding coefficient as channel estimating reprocessing thresholding again.

Perhaps also can select: remove the tap of 1 energy maximum in each window, not strict orthogonal between the Midamble code is done correction, make the result of noise calculation more accurate, other 120 all noise path energy are averaging, as system's average noise, pass through again the weighting of thresholding coefficient as channel estimating reprocessing thresholding.

In the TD-SCDMA system, channel estimation value can calculate by the Steiner channel estimator, it is a kind of channel estimation methods of low-cost, it constructs each user's Midamble code according to certain rules by a basic Midamble code, thereby so that have circular dependency at the Midamble of receiving terminal code system matrix, so just can calculate with FFT and IFFT and obtain fast channel estimation value.

The Steiner channel estimator by the IFFT inverse transformation, obtains the time domain channel estimated value more first in frequency-domain calculations, removes noise effect by the channel estimating reprocessing at last.

Calculate first the frequency domain value received_midamble_fft of the Midamble partial data received_midamble of the 128chip that receives:

received_midamble_fft＝fft(received_midamble) (1)

The calculating of channel estimation value channel is first two frequency domain values to be divided by, and result again IFFT transforms to time domain, and is as follows:

channel＝ifft(received_midamble_fft·/basic_midamble_fft)(2)

Wherein. the corresponding number of two arrays of/expression is divided by.

The channel estimating reprocessing is exactly with the thresholding of the result of top channel estimating and a setting relatively, sets to 0 less than the channel estimating tap of thresholding.The accuracy of thresholding setting directly determines the precision of channel estimating.

Under many cell environments, in order to eliminate the interference with adjacent cell frequently, accurately estimate this residential quarter and adjacent cell user's channel estimating, need to do the adjacent cell interference-cancellation process.Interference Cancellation generally adopts multistep treatment, eliminates the interference of each residential quarter.Its principle is in data, deducts other the signal of residential quarter of reconstruct.

The channel estimating of each residential quarter of every one-level all needs to carry out the channel estimating reprocessing and removes noise, obtains effective channel estimating tap.The accuracy of reprocessing thresholding setting directly affects the precision of channel estimating, thereby affects the precision of signal reconstruction, and the effect of eliminating is disturbed in impact.If it is improper that the reprocessing thresholding arranges, can affect the calculating of system noise, ISCP, RSCP, SIR, affect power control, cause whole receiver demodulation performance to descend, under strong jamming under the multi-path environment even can't work.

Step 104, the data received_midamble with in the Midamble code, the Midamble code of each residential quarter, and the channel estimating reprocessing threshold value of step 103 acquisition calculate the channel estimation value of each residential quarter.

With the partial data received_midamble in the Midamble code that receives, the Midamble code of each residential quarter, and the channel estimating reprocessing threshold value that calculates, the channel estimating of each residential quarter calculated;

In the present embodiment, concrete grammar is as follows:

$\mathrm{recevied}\_\mathrm{midamble}\_\mathrm{residual}=\mathrm{recevied}\_\mathrm{midamble}-\underset{\mathrm{othercell}}{\mathrm{\Σ}}\mathrm{conv}(\mathrm{channel},\mathrm{basic}\_\mathrm{midamble})$

Wherein, $\underset{\mathrm{othercell}}{\mathrm{\Σ}}\mathrm{conv}(\mathrm{channel},\mathrm{basic}\_\mathrm{midamble})$ Be time domain with the Midamble part signal of other residential quarters of channel estimation value and basic Midamble code convolution reconstruct and.

Then, received_midamble_residual is inputted the Steiner channel estimator and calculate channel estimating.

As shown from the above technical solution, the channel estimation accuracy of terminal under the co-channel interference environment can be improved by the said method flow process, thereby the demodulation performance of terminal can be improved.

In order to realize above-mentioned embodiment of the method, other embodiment of the present invention also provide the device that terminal channel is estimated in a kind of TD-SCDMA system.What need in addition at first explanation is; because following embodiment is for realizing aforesaid embodiment of the method; therefore this device all is to establish for each step that realizes preceding method; but the present invention is not limited to following embodiment, and any device of said method of realizing all should be contained in protection scope of the present invention.And in the following description, the content identical with preceding method omitted at this, to save length.

Referring to Fig. 2, be the structure drawing of device that terminal channel is estimated in the TD-SCDMA system among the present invention, by among the figure as can be known, this device 20 comprises:

Determination module 21 is for the Midamble code of determining channel estimating reprocessing Noise gate limit value;

The first computing module 22 is used for the data received_midamble of described Midamble code is removed the signal of each residential quarter of reconstruct, obtains removing the data received_midamble_net behind the signal of all residential quarter reconstruct;

The second computing module 23 is used for obtaining channel estimating reprocessing threshold value according to described data received_midamble_net and described Midamble code;

Channel estimation module 24 is used for the Midamble code according to described data received_midamble, each residential quarter, and the described channel estimating reprocessing threshold value that obtains, and calculates the channel estimation value of each residential quarter.

In another embodiment of the present invention, this device 20 also comprises: circulation module 25, be used for controlling described the first computing module 22, the second computing module 23 and channel estimation module 24 and open operation, all finish until set the interference elimination of progression, export last channel estimation value.

The above only is preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (6)

1. the method that terminal channel is estimated in the TD-SCDMA system is characterized in that, described method comprises:

Step 1, determine the Midamble code that channel estimating reprocessing Noise gate limit value calculates;

Step 2, the data received_midamble in the described Midamble code removed the signal of each residential quarter of reconstruct, obtain removing the data received_midamble_net behind the signal of all residential quarter reconstruct;

Step 3, with the described Midamble code of determining in the described data received_midamble_net that exports in the described step 2 and the described step 1, obtain channel estimating reprocessing threshold value;

Step 4, with the Midamble code of described data received_midamble, each residential quarter, and the channel estimating reprocessing threshold value that obtains of described step 3 is calculated the channel estimation value of each residential quarter;

Described method also comprises:

Step 5, repeat described step 2 to the process of described step 4, eliminate and all finish until set the interference of progression, export last channel estimation value.

2. the method that terminal channel is estimated in the TD-SCDMA system according to claim 1 is characterized in that, described step 1 is specially:

Determined the Midamble code of calculating noise threshold value by Cell searching, Cell searching calculates the energy of each residential quarter, chooses the corresponding Midamble code in the most weak residential quarter of energy, as the Midamble code that calculates channel estimating reprocessing Noise gate limit value; Perhaps

By measuring the Midamble code of determining the calculating noise threshold value, choose a Midamble code that the residential quarter is corresponding by measuring in the residual set of determining, as the Midamble code of subsequent calculations channel estimating reprocessing Noise gate limit value.

3. the method that terminal channel is estimated in the TD-SCDMA system according to claim 1 is characterized in that, if when the first order is processed, the signal of described all the residential quarter reconstruct in the described step 2 is zero.

4. the method that terminal channel is estimated in the TD-SCDMA system according to claim 1 is characterized in that, described step 3 is specially:

Described Midamble code with determining in the described data received_midamble_net of described step 2 and the described step 1 by the Steriner channel estimator, obtains 8 channel estimation windows totally 128 noise path;

128 all noise path energy are averaging, and as system's average noise, pass through the weighting of thresholding coefficient as channel estimating reprocessing thresholding again.

5. the method that terminal channel is estimated in the TD-SCDMA system according to claim 1 is characterized in that, described step 3 is specially:

Remove the tap of an energy maximum in each channel estimation window, and 120 noise path energy that other are all are averaging, as system's average noise;

By the thresholding coefficient to the average noise weighting of described system as channel estimating reprocessing threshold value.

6. the device that terminal channel is estimated in the TD-SCDMA system is characterized in that, described device comprises:

Determination module is used for the Midamble code of determining that channel estimating reprocessing Noise gate limit value calculates;

The first computing module is used for the data received_midamble of described Midamble code is removed the signal of each residential quarter of reconstruct, obtains removing the data received_midamble_net behind the signal of all residential quarter reconstruct;

The second computing module is used for obtaining channel estimating reprocessing threshold value according to described data received_midamble_net and described Midamble code;

Channel estimation module is used for the Midamble code according to described data received_midamble, each residential quarter, and the described channel estimating reprocessing threshold value that obtains, and calculates the channel estimation value of each residential quarter;

Described device also comprises:

Circulation module is used for controlling described the first computing module, the second computing module and channel estimation module and opens operation, all finishes until set the interference elimination of progression, exports last channel estimation value.

Images