KR20020030473A - System and method for spreading factor estimation in variable rate direct sequence code division multiple access systems - Google Patents

Abstract

PURPOSE: A system for estimating a spreading factor in a variable transmission rate DS/CDMA(Direct Sequence/Code Division Multiple Access) system and a method therefor are provided to decrease the number of memory for storing signals received before spreading factor information is received and shorten a signal process time by estimating the spreading factor using the received signal and using the estimated spreading factor in a data channel. CONSTITUTION: If a data channel signal is received(S300), a despreading process is performed(S310). Despreaded result information is received, and received result information is processed(S320). Processed information is received, and received information is combined during a combination interval(S330). Combined result information is received, and a conversion process for estimating spreading factors is performed(S340). The performed result value is received, and a transform function(f(.)) and a function(gk(.)) are suitably set or the functions(f(.),gk(.)) are varied, if necessary. The spreading factors are received from a function(e) or reference information is received from an other place, and the function(e) and reference information are processed and selected for estimating the spreading factors(S350).

Description

System and method for spreading factor estimation in variable rate direct sequence code division multiple access systems

The present invention relates to a system for obtaining a spreading element in a variable rate direct sequence code division multiple access system, and more particularly, to a method for obtaining spreading elements in a variable rate direct sequence code division multiple access system. A system and method for estimating spreading factors using signals received in a channel.

One of the widely used methods for varying the transmission rate in a direct sequence code division multiple access system is to transmit a variable spreading factor. At this time, in order to recover the information transmitted from the receiver, it is necessary to know the spreading factor. In some systems, the spreading factor of the symbol may be known in advance, but in some systems, it may be known only after a certain time has elapsed, for example, after a frame is finished. In this case, storing a received signal for that time and processing requires a lot of storage.

1A and 1B schematically illustrate a method of obtaining a spreading element in a receiver of various variable rate direct sequence code division multiple access systems, which will be described in detail as follows.

First, FIG. 1A is a system capable of knowing a spreading element in advance, and transmits the spreading element 120 of information to be transmitted by the transmitter 110 directly to the receiver 140 in advance of the information 130 to be transmitted or a higher layer ( 150).

1B is a system in which the spreading element is unknown in advance, and transmits the spreading element 170 directly to the receiver 190 along with information 180 to be transmitted by the transmitter 160. In this case, the receiver 190 does not know until the time when the diffusion element is determined (for example, at the end of one frame).

For example, a 3GPP2 (3GPP2) CDMA2000 system may be known as a spreading factor. For example, an uplink of a 3GPP wideband CDMA system may be used as an example. Can be.

However, as illustrated in FIG. 1B, in the case of a system in which a spreading element is not known in advance, there is a problem in that a large amount of storage device is required because the received signal must be stored for a certain period of time.

Accordingly, an object of the present invention is to solve the problems of the prior art, and an object of the present invention is to provide a signal received in a data channel when a spreading element is not known in advance in a receiver of a variable rate direct sequence code division multiple access system. By estimating and using the spreading factor by using a, it is to reduce the number of storage devices storing the received signal until the spreading element information is received, and to shorten the signal processing time.

FIG. 1A is a diagram illustrating a method of obtaining a spreading element in a case in which a spreading element is known in advance in a receiver of various variable rate direct sequence code division multiple access systems. FIG.

FIG. 1B is a diagram schematically illustrating a method of obtaining a spreading element when a spreading element is not known in advance in a receiver of various variable rate direct sequence code division multiple access systems; FIG.

2 is a flowchart illustrating a method of estimating a spreading element in a variable rate direct sequence code division multiple access system according to an embodiment of the present invention;

3 is a block diagram of a spreading factor estimation system in a variable rate direct sequence code division multiple access system according to an embodiment of the present invention.

※ Explanation of code about main part of drawing ※

110, 160: transmitter 120, 170: diffusion element

130, 180: information to be transmitted 140, 190: receiver

150: upper layer 410: despreader

420: accumulator 430: processing machine

440: Combiner 450: Converter

460: Machining & Selector

According to the present invention for achieving the above object, a despreader for despreading a signal received in a data channel according to each spreading element possible; A combiner for receiving the respective despread information from the despreader and processing the despreading information according to a predetermined method and then combining the despreader for a predetermined time; And a selector for performing a function of estimating a spreading element using the information combined in the combiner. The spreading element estimation system of the variable rate direct sequence code division multiple access system is provided.

Further, a first step of despreading the signal received in the data channel according to each possible spreading element; A second step of receiving each despread information in the first step, processing the same according to a predetermined method, and then combining the despreading information for a predetermined time; And a third step of estimating and selecting a spreading element using the information combined in the second step. The spreading element estimation method of the variable rate direct sequence code division multiple access system is provided.

In addition, the computer further comprises: a first step of despreading the signal received in the data channel according to each spreading element possible; A second step of receiving each despread information in the first step, processing the same according to a predetermined method, and then combining the despreading information for a predetermined time; And a third step of estimating and selecting a spreading element using the information combined in the second step, a computer-readable recording medium having recorded thereon a program capable of executing the program.

Hereinafter, an apparatus and method for estimating a spreading factor in a variable rate direct sequence code division multiple access system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a flowchart illustrating a method for estimating a spreading element in a variable rate direct sequence code division multiple access system according to an embodiment of the present invention.

First, when a data channel signal r (t) is received in step S300, a despreading process is performed in step S310. In more detail, let {SF ₀ , ..., SF _n } be a set of possible spreading elements. At this time, when i> j, SF _i > SF _j . That is, in step S310 SF _0, from r (t) ..., and despread with SF _n.

Subsequently, in step S320, a process of processing the despread information by receiving the result of the despreading in step S310 is performed. In more detail, g _k (.) = {G _{k, 1} (.), ..., g _{k, q} (.)} Is a function of processing the despread information according to the k th diffusion element. . Where q = M x SF _n / SF _k .

Subsequently, in step S330, the process of combining the received information processed in step S320 during the joining period is performed. In more detail, the combining section is M x SF _n , and the k th processed information is combined by q = M x SF _n / SF _k pieces. If the combined information is d = {d ₀ , ..., d _n }, d _k is defined as shown in Equation 1 below.

Where M x SF _n is a coupling interval that combines to estimate the spreading factor, T _c is the chip period, c _k is the despread signal corresponding to spreading element SF _k , and τ is the time delay of the received signal Indicates.

Subsequently, in step S340, the resultant of step S330 is input to perform a conversion process for spreading element estimation. In more detail, f (.) Is a transform function for spreading element estimation, and is defined as f (d) = e = {e ₀ , ..., e _n }.

On the other hand, the above functions f (.) And g _k (.) May be varied by the variable information 370 according to a predetermined rule.

Subsequently, in step S350, the resultant in step S340 is input, and f (.) And g _k (.) Are appropriately determined or variable as necessary, so as to reference the diffusion element SF from e or from elsewhere. The process of selecting e and the reference information 390 by processing the information 390 is performed to estimate a spreading factor.

3 is a block diagram of a spreading element estimator in a variable rate direct sequence code division multiple access system according to an embodiment of the present invention, wherein the spreading element estimator despreads a signal of a received data channel to a minimum spreading element. The despreader 410 performs a process of accumulating the despread signal from the despreader 410 according to a spreading factor, and processes the output signal from the accumulator 420. The processor 430 performing the process, the combiner 440 performing the process of combining the information processed by the processor 430 during the combining period, the combined information received from the combiner 440 to estimate the diffusion element The converter 450 is configured to perform a process for converting the data, and a processing and selector 460 for estimating a spreading element by receiving the value converted by the converter 450.

This will be described in detail as follows.

First, when a signal of a data channel is received, the despreader 410 despreads each possible spreading element SF ₀ ,..., SF _n and then accumulates the accumulator 420 according to each possible spreading element. Accumulate in. Wherein each accumulator 420 is according to a respective diffusion element.

The processor 430 receives the output of the accumulator 420 and processes each of the absolute values by taking an absolute value, and then multiplies a predetermined integer multiplied by the maximum diffusion element of the chip period in the combiner 440. Accumulate d over time to get d. At this time, the present embodiment is designed to accumulate for an integer time of the maximum spreading element of the chip period, but this does not exclude the operator's arbitrary designation.

The converter 450 receives d obtained from the combiner 440 to obtain e converted by e _k = a _k d _k (where a _k is a predetermined value). Finally, the processing and On selector 460 The spreading factor SF is estimated. At this time, by receiving the noise power information 480 from the other, or by processing the received information accordingly Compare with the value.

At this time, The value is only processed noise If the value is not greater than a predetermined threshold, the estimated SF may not be valid.

On the other hand, in the present embodiment, the maximum value is taken by using the constant a _k above, but when the designer arbitrarily designates another a _k and uses it with other selection criteria, the new e '(e' = a _k 'd _k obtained is obtained. ) Can be converted from e obtained in the present embodiment, and the case in which the index value selected according to the new selection criteria obtains the same result as taking the maximum value in the present embodiment is not excluded. For example, you can use a ' _k = -a _k and take the minimum value.

In other words, in this embodiment, the maximum value is taken by using the function f (.), But when the designer arbitrarily designates another function f '(.) And uses it with other selection criteria, the new e' (e '= f obtained) is obtained. It is not excluded that '(d)) can be converted from e obtained in the present embodiment, and the index value selected according to the new selection criteria obtains the same result as obtaining the maximum value in the above embodiment.

In addition, in the case of a system using diversity, the spreading element SF may be estimated by inputting the information obtained from each diversity element to the processing and selector 460.

In general, in a code division multiple access mobile communication system, the signal-to-noise ratio of a symbol is adjusted according to the quality of service through power control. The target signal-to-noise ratio can be known by the receiver. In the case of a coherent system, a reference channel may be used for channel estimation, and in some cases, a power ratio between the reference channel and the data channel is determined, and the receiver knows this in advance. Can be. Using this property, in the embodiment of FIG. 3, α is set to 2 and a _l = 2 ^-k (k = 0, ..., n) to set the power of the noise-received received symbol according to each spreading element. Then, as reference information, the symbol power value of the reference channel, the estimated noise power value, and the power ratio of the reference channel and the data channel are inputted to select a spreading element having a value closest to the estimated data channel power or signal-to-noise ratio. Can be.

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

As described above, according to the present invention, when the spreading element is not known in advance in the receiver of the variable rate direct sequence code division multiple access system, if the spreading element is estimated using the signal received in the data channel, the spreading element is required. Various signal processing procedures can be performed quickly, and the number of storage devices storing the received signals can be greatly reduced.

As an example, in the case of a coherent system, when using a method of using the reference channel and the data channel together to increase the performance of the channel estimator, the information of the data channel is despread using the estimated spreading factor and used for channel estimation. As a result, the amount of memory required and the signal processing time can be greatly reduced.

Claims (21)

A despreader for despreading the signal received in the data channel according to each spreading element possible; A combiner for receiving the respective despread information from the despreader and processing the despreading information according to a predetermined method and then combining the despreader for a predetermined time; And And a selector for performing a function of estimating a spreading element by using the combined information in the combiner. The method of claim 1, The combiner receives the despread value from the despreader, takes an absolute value, and processes the result by performing a predetermined value α power. . The method according to claim 1 or 2, And the combiner accumulates and combines the processed values for an integer multiple of the maximum spreading element of the chip period for spreading factor estimation system in a variable rate direct sequence code division multiple access system. The method of claim 3, wherein The combiner combines the processed values according to Equation 1 below. The spreading factor estimation system of the variable rate direct sequence code division multiple access system. [Equation 1] Where M x SF _n is a coupling interval that combines to estimate the spreading factor, T _c is the chip period, c _k is the despread signal corresponding to spreading element SF _k , and τ is the time delay of the received signal G _k (.) = {G _{k, 1} (.), ..., g _{k, q} (.)} Is a function of processing the despread information according to the k th diffusion element. The method of claim 3, wherein And the selector selects a spreading element corresponding to an index of the largest value among the information combined in the combiner as an actual spreading element. The method of claim 5, And the selector receives the noise power information and compares the estimated spreading element with the largest value of the combined information in the combiner to verify the estimated spreading factor. The method of claim 3, wherein And the selector selects a spreading element corresponding to an index of the smallest value among the pieces of information combined in the combiner as an actual spreading element. The method of claim 7, wherein And the selector receives the noise power information and compares the estimated spreading element with the smallest value of the combined information in the combiner to verify the estimated spreading element. The method of claim 1, The selector obtains a power of a received symbol mixed with noise according to each spreading element, and then receives a symbol power value of a predetermined channel, an estimated noise power value, and a power ratio of a predetermined channel and a data channel. A spreading factor estimation system in a variable rate direct sequence code division multiple access system, wherein the spreading factor is selected to have a value closest to the power or the signal-to-noise ratio of the signal. The method of claim 1, The selector, in the case of a system using diversity, the spreading element estimation system in the variable rate direct sequence code division multiple access system, characterized in that for selecting the spreading element using the information obtained from each diversity element. Despreading a signal received in the data channel according to each spreading element possible; A second step of receiving each despread information in the first step, processing the same according to a predetermined method, and then combining the despreading information for a predetermined time; And And a third step of estimating and selecting a spreading factor using the information combined in the second step. The method of claim 11, The second step receives the despread value in the first step, takes an absolute value, and then processes the result by performing a predetermined value α power. Factor estimation method. The method according to claim 11 or 12, And the second step accumulates and combines the processed values for an integer multiple of the maximum spreading factor of the chip period. The method of claim 13, The second step is a spreading factor estimation method in a variable rate direct sequence code division multiple access system, characterized in that combining the processed values according to the following [Equation 2]. [Equation 2] Where M x SF _n is a coupling interval that combines to estimate the spreading factor, T _c is the chip period, c _k is the despread signal corresponding to spreading element SF _k , and τ is the time delay of the received signal G _k (.) = {G _{k, 1} (.), ..., g _{k, q} (.)} Is a function of processing the despread information according to the k th diffusion element. The method of claim 14, The third step, A variable for estimating a spreading element by receiving the d _k , performing a transform process for estimating a spreading element using a predetermined transform function, and processing predetermined reference information and a result of the transforming process A Spreading Factor Estimation Method in a Direct Rate Sequence Division Multiple Access System. The method of claim 15, In the third step, a spreading factor estimation method in a variable rate direct sequence code division multiple access system, wherein the spreading element corresponding to the index of the largest value among the information combined in the second step is selected as an actual spreading element. . The method of claim 16, The third step includes receiving noise power information and comparing the largest value among the information combined in the second step to verify the estimated spreading factor. The spreading factor in the variable rate direct sequence code division multiple access system according to claim 3, wherein Estimation method. The method of claim 16, In the third step, a variable bit rate direct method is used to estimate a value obtained by using a different transform function arbitrarily and a value obtained when a result obtained by obtaining a maximum value according to a new selection criterion is obtained as a maximum value. Spreading Factor Estimation Method in Sequence Code Division Multiple Access Systems. The method of claim 11, The third step is to calculate the power of the received symbol mixed with noise according to each spreading element, and then input the symbol power value of the predetermined channel, the estimated noise power value and the power ratio of the predetermined channel and the data channel is estimated A spreading factor estimation method in a variable rate direct sequence code division multiple access system, characterized in that a spreading factor is selected that has a value closest to a power or signal-to-noise ratio of a data channel. The method of claim 11, In the third step, in the case of a system using diversity, a spreading factor estimation method in a variable rate direct sequence code division multiple access system, characterized in that a spreading factor is selected using information obtained from each diversity factor. . On your computer, Despreading a signal received in the data channel according to each spreading element possible; A second step of receiving each despread information in the first step, processing the same according to a predetermined method, and then combining the despreading information for a predetermined time; And A computer having recorded thereon a program capable of executing what is included, comprising a third step of estimating and selecting a spreading factor using the information combined in the second step Readable media.