KR20080041520A - A method for estimation and saving channel in communication system - Google Patents

Abstract

Methods for estimating and saving a channel in a communication system are provided to reduce the complexity of the system by using average CE(Channel Estimation) together with joint CE when a sounding sequence does not have orthogonality. A method for estimating a channel in a communication system includes the steps of: checking the orthogonality between sounding sequences between terminals of an inner cell and an adjacent cell(302); estimating the channels by using a first CE scheme when maintaining the orthogonality(304); and judging whether the complexity of the system is very high when the orthogonality is not maintained(308). The method further includes the steps of: performing CE through the first CE scheme; selecting a smaller number of terminals than the number of terminals considered by user selection(312); and performing the CE for the selected terminals by using a second CE scheme when the complexity is very high(314). The method further includes a step: performing the CE by using the second CE scheme when the complexity is not high(316).

Description

A method for Estimation and Saving Channel In Communication System

1 illustrates a communication system according to a preferred embodiment of the present invention.

2 is a diagram illustrating a method of estimating a channel when a sounding sequence according to the first embodiment of the present invention has orthogonality.

3 is a flowchart illustrating a channel estimation method of a base station according to an exemplary embodiment of the present invention.

4 is a diagram illustrating an example of a method for storing an estimated channel value according to a fourth embodiment of the present invention.

5 is a diagram illustrating an example of a method of storing estimated channel values according to a fourth embodiment of the present invention;

6 is a view showing a method of storing an estimated channel value in the case of a PUSC BF according to a fourth embodiment of the present invention.

The present invention relates to a communication system and to a channel estimation and channel storage method.

Techniques using multiple antennas (hereinafter referred to as 'MIMO') have been actively studied to increase capacity of high-speed data transmission and communication systems. The user terminal is difficult to apply multiple antennas due to space constraints. Therefore, a beamforming technique using multiple antennas at the base station side and one antenna at the user terminal has attracted a lot of attention.

In the case of downlink (hereinafter, referred to as 'DL'), the base station collects channel information using a method such as feedback or sounding to obtain channel information. Thus, many of the BF techniques known to date are mostly limited to the case of uplink (hereinafter referred to as 'U'), where the base station can easily obtain the channel information necessary for the application of BF.

The WiBro (Wireless Broadband Internet) system, which is currently being actively developed, performs a BF function at a base station based on a sounding method. In particular, the WIBRO system uses a sounding method to use channel information in the base station during DL.

Specifically, in the sounding method, the user terminal generates a sounding sequence according to a predetermined method, and then transmits the sounding sequence to the corresponding base station. The base station then estimates the channel using the received sounding sequence. For example, in a time division duplex (TDD) system, the base station may use a channel estimated at UL for DL-BF. A simple DL-BF technology is Tx-MRC (Transmit Maximal Ratio Combining). To implement this, only the channel from the base station to the designated terminal needs to be estimated.

As described above, Tx-MRC is optimal in a single cell point-to-point communication environment, but in a multi-cell environment, the performance of the Tx-MRC is greatly degraded due to interference from external cells. There was this.

Accordingly, an object of the present invention, which is designed to solve the problems of the prior art operating as described above, is to provide a method for estimating channels of location terminals in a terminal located in a corresponding base station and adjacent cells without interference with each other. .

Another object of the present invention is to reduce the complexity of the system, when the sounding sequence does not have orthogonality, Average Channel Estimation (hereinafter referred to as 'average CE') and Joint Channel Estimation (Joint CE)) It is to provide a method to use a mixture.

Another object of the present invention is to provide a method for storing an estimated channel.

In accordance with another aspect of the present invention, a method for storing a channel in a communication system includes: combining a predetermined number of subcarriers of the channel estimated by sounding according to channel characteristic values. And storing the units in units of one or more groups generated by dividing into a predetermined number of subchannels among the subchannels constituting the channel.

Another embodiment of the present invention provides a method of storing a channel in a communication system, comprising: estimating subcarriers of the channel by sounding the entire frequency domain; According to the present invention includes a step of rotating by configuring a single unit consisting of a predetermined number of combinations, and the step of re-grouping only the necessary parts for the entire frequency band.

Another embodiment of the present invention provides a method of estimating a channel in a communication system, the method comprising: checking whether orthogonality is maintained between sounding sequences between terminals of an inner cell and an adjacent cell, and maintaining orthogonality as a result of the checking; If so, the method includes estimating a channel using the first channel estimation method, and determining whether the system complexity is very large if the orthogonality is not maintained as a result of the checking.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. Like reference numerals refer to the same elements as shown in the drawings, even though they may be shown on different drawings, and detailed descriptions of related well-known functions or configurations are not required in the following description of the present invention. If it is determined that it can be blurred, the detailed description will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, the present invention proposes a method for estimating a channel through a DL-BF scheme that can eliminate interference between terminals located in a cell to which a specific base station belongs and terminals located in an adjacent cell. That is, the base station applies DL-BF weight similarly to applying Minimum Mean Squared Error (MMSE) in UL in order to enhance and send signals to terminals of the same cell while removing signals received from neighboring terminals. The applied signal is transmitted using the multi antenna of the base station.

To this end, the present invention proposes a method in which a base station estimates channels of neighboring cell terminals as well as a terminal located in an inner cell and stores the estimated channel information. Here, as an example, a method of interpolating and storing BFs based on band-adaptive modulation and coding (B-AMC) and partial usage of subchannels (PUSC) permutation schemes in a WiBro system will be described. do.

1 is a diagram illustrating a communication system according to an exemplary embodiment of the present invention. Here, the DL operation of the base station 100 and the terminal 140 of the WiBro system will be described as an example.

Referring to FIG. 1, the base station 100 generates user data 102 to encode an encoding unit 104, a symbol mapping unit 106, and a scrambling unit 108. ) Performs an OFDM function, calculates a BF weight through a BF weight application unit 116, and applies it to a du signal, an IFFT unit 118, and a CP (cyclic prefix) adding unit ( And a channel sounding unit 110 for estimating a channel using sounding with the signal having passed through 120, and a channel estimating unit 112 and a linear interpolation unit 114.

The terminal 140 includes a CP remover 142, an FFT unit 144, a descrambling unit 146, a symbol demapping unit 148, and a decoding unit. 150 and a detection unit 152 are configured.

The present invention corresponds to a part of estimating a channel using a sounding signal in the base station 100 and a method of storing a channel, so that a DL-BF function for performing interference nulling can be improved. Is designed.

Hereinafter, the present invention consists of four embodiments.

In the first embodiment, the channel is estimated when the sounding sequence has orthogonality.

In the second embodiment, the channel estimation method is performed when the sounding sequence does not have orthogonality.

In a third embodiment, average cyclic shift separation is used to reduce the influence of cross-correlation of non-orthogonal sounding sequences in channel estimation.

In the fourth embodiment, the estimated channel is linearly interpolated and stored according to a permutation method.

2 is a diagram illustrating a method of estimating a channel when a sounding sequence has orthogonality according to the first embodiment of the present invention. Here, the channel is estimated using the average CE method.

Referring to FIG. 2, the base station 200 of the communication system generates not only a desired signal to the inner cell terminal 202 but also interference signals to the terminals 204, 206, and 208 of the outer cell.

When the sounding scheme is effectively used in a time division duplex (TDD) system, it is possible to estimate a channel at a base station while overcoming the influence of interference.

Specifically, a sounding sequence having orthogonality is generated in a WiBro system. The generation of the sounding signal begins by stripping off a portion of the Golay sequence. The Golay sequence has a low Peak Average Power Ratio (PAPR) with one dive configured of ± 1. For example, a Golay sequence g ^T having a length L is represented by Equation 1 below.

은 와이브로에서 사용되는 오프셋(offset)값을 일 예로 사용한다.here,

Uses an offset value used in WiBro as an example.

인 Golay 시퀀스의 일부분을 떼어낸 다음, 페이즈(phase) 항{

}들을 떼 낸 Golay 시퀀스 부분에 하기 <수학식 2>와 같이 곱하여, 완성된 사운딩 시퀀스

를 만든다.Length

Remove a portion of the Golay sequence and then add the phase term {

} Golay sequence of removing them is multiplied by Equation 2 below to complete sounding sequence

Make

Here, m denotes a cyclic-shift time index, and P _c denotes a cyclic shift period. The k _start and N _{used, which} are the length of the Golay sequence, are given as integer multiples of P _c . Different cyclic shift indices for the same Golay sequence portion make the sounding sequences of generated length P _c orthogonal to each other.

)은 하기 <수학식 3>와 같이 정의된다.For example, the orthogonality of two sounding sequences (

) Is defined as in Equation 3 below.

퀀스의 콤플렉스 콘쥬게이트(complex conjugate)를 곱하고 평균을 취하여 계산된다.Here, g is an integer, and when the channel is estimated by sounding, it is assumed that consecutive P _c subcarriers have the same channel coefficient. For example, when a base station receives sounding sequences having a length P _c orthogonality from a number of terminals less than or equal to P _c present in the same cell and a foreign cell, the base station may be connected to the base station from the terminals. Estimate each channel. The channel estimation may be performed on specific sounding of the received signal.

Calculated by multiplying the complex conjugates of the quants and taking the average.

i-번째 기지국의 a-번째 안테나(antenna)를 통해 k-번째 서브캐리어 상에서 수신된 신호(

)이다.Equation 4 is

The signal received on the k-th subcarrier through the a-th antenna of the i-th base station (

)to be.

는 u-번째 단말기에서 i-번째 기지국으로의 채널을 표시하고,

는 ZMCSCG(Zero Mean Circularly Symmetric Complex Gaussian) 잡음을 표시한다. UL채널인

를 DL채널인

로 대치할 수 있는데, 이는 두 채널이 TDD시스템에서 서로 동일하다고 할 수 있기 때문이다. 연속적인 개의 서브캐리어들이 동일한 주파수 채널응답을 갖는다고 가정할 경우, Wherein a is an antenna identifier, u is a terminal identifier, i is a terminal identifier, and

Indicates a channel from the u-th terminal to the i-th base station,

Denotes Zero Mean Circularly Symmetric Complex Gaussian (ZMCSCG) noise. UL channel

DL channel

This is because the two channels are identical to each other in the TDD system. Assuming successive subcarriers have the same frequency channel response,

a-번째 안테나에서 u-번째 단말로의 채널을 상수 채널 계수(

)로 표시할 수 있다. 즉, 상기 채널이 원래는

이지만 주어진 서브캐리어 레인지에서 상수값을 가지므로 상기 <수학식 4>에서 노이즈(noise) 부분인

를 생략할 경우, k-번째 서브캐리어 상에서 i-번째 기지국의 a-번째 안테나로 수신한 수신 신호를 하기 <수학식 6>과 같이 근사화 한다.For the subcarrier range represented by Equation 5, the i-th base station

The channel from the a-th antenna to the u-th terminal is determined by a constant channel coefficient (

) Can be displayed. That is, the channel is originally

However, since it has a constant value in a given subcarrier range, the noise portion of Equation 4

If omitted, the received signal received by the a-th antenna of the i-th base station on the k-th subcarrier is approximated as in Equation 6 below.

Using the orthogonality characteristic of the sounding sequence, the channel from the a-th antenna of the i-th base station to the v-th terminal on the subcarrier range as shown in Equation 5 is estimated as in Equation 7 below. do.

를 얻는다.The channel estimation as described above is repeated for all antennas of the base station and all terminals to be considered, and is repeated for a given frequency domain, where the DL channel matrix is expressed by Equation 8 below.

Get

On the other hand, when the sounding sequences do not have orthogonality to each other, a large performance degradation may occur when estimating channels of terminals of the same cell and terminals of adjacent cells using the average CE method according to the first embodiment.

Hereinafter, in the second embodiment of the present invention, when the sounding sequence does not have orthogonality, the joint CE method is used to accurately estimate the channel while avoiding the influence of the correlation between the sounding sequences. Estimate

)이다.Equation (9) below is a frequency domain signal vector received with the a-th antenna and the g-th group of the i-th base station (

)to be.

는 0주파수 톤(tone)들 '

' 상에서의 수신 신호를 나타내는 벡터를 하기 <수학식 10>내지 <수학식 12>와 같이

와

,

매트릭스 형태로 표현된다.remind

Zero frequency tones ''

A vector representing the received signal on 'is expressed as in Equation 10 to Equation 12.

Wow

,

It is expressed in matrix form.

에 상기 <수학식 10>을 통해서 구해진

를 이용하여 계산된 하기 <수학식 13>을 곱하고, 노이즈(

)부분의 크기를 무시할 경우, 상기

의 추정치는 하기 <수학식 14>와 같이 계산된다.Next, U is the sum of the number of terminals present in the neighboring cells and the communicating terminal on one subcarrier under consideration by the base station. remind

Obtained through Equation 10 above

Multiply the following <Equation 13> calculated by using the noise (

If you ignore the size of the part,

The estimate of is calculated as shown in Equation 14 below.

As described above, in order to enable channel estimation using Equation 14, the following two conditions must be satisfied.

의 랭크(rank)가

을 만족해야 한다. 즉,

임을 가정하면, 상기

는 임의의 두 열이 서로 달라야 함을 의미한다. 상기 "서로 다른 두 열" 조건을 만족하기 위해서 사이클릭 쉬프트 분리(Cyclic-shift Separability) 시, 한 셀에 속하는 단말기들이 서로 다른 타임 쉬프트(time shift)값( 상기 <수학식 2>에서의 m)을 갖도록 사운딩 시퀀스를 생성하거나, 다른 셀에 속하는 단말기들이 서로 다른

값을 사용하여 사운딩 시퀀스를 생성해야 한다. The first condition is that

Your rank

Must be satisfied. In other words,

Assuming that

Means that any two columns must be different. In order to satisfy the "two different columns" condition, cyclic shift separation (Cyclic-shift Separability), the time shift value of the terminals belonging to one cell (m in Equation 2) Create a sounding sequence to have or have different terminals belonging to different cells

You must create a sounding sequence using the values.

이 좋은 상태 넘버(condition number)를 가져야 한다. 즉,

이 작을수록

를 곱했을 때, 노이즈 부분의 크기가 매우 커지는 노이즈 증대(noise enhancement) 효과가 발생하지 않도록 해 준다.The second condition is

You should have this good condition number. In other words,

The smaller this is

When multiplying by, the noise enhancement effect of the noise portion becomes very large.

가 두번째 조건을 유지하게 됨으로써, 사운딩 시퀀스가 서로 직교성을 갖지 않을 경우라도 기지국 내부 셀의 단말기와, 상기 내부 셀의 인접 셀 단말기들의 채널들을 서로간의 간섭이 없이 추정한다.That is, when the first condition is satisfied,

By maintaining the second condition, even when the sounding sequences do not have orthogonality to each other, the terminals of the base station inner cell and the adjacent cell terminals of the inner cell are estimated without interference with each other.

Hereinafter, a method of reducing cross-correlation effects of sounding sequences having no orthogonality in channel estimation using an average CE (for Cyclic-shift Separation) method according to a third embodiment of the present invention will be described.

In cyclic shift separation, when orthogonality is maintained between sounding sequences, the performance of the channel estimated by the average CE method and the joint CE method is the same. However, when comparing the complexity of the average CE method and the joint CE method, the complexity of the average CE is much smaller than the joint CE.

값을 사용하고, 임의의 한 셀이 인접 셀들에서 사용한

값들과 사운딩 시퀀스의 타임 쉬프트 값들을 모두 알 경우, 한 셀이 크로스 상관(cross correlation) 문제를 피하면서 채널 추정을 하기 위해서는 조인트 CE방법을 사용한다. 평균 CE는 사운딩 신호를 사용해 조작한 일정 개수의 수신신호를 평균하여 채널을 추정하는 방법이고, 조인트 CE는 일정 개수의 수신 신호로 이루어진 벡터로부터 사운딩 신호로 구성된 매트릭스 부분을 매트릭스 연산을 통해 제거함으로써 채널을 추정하는 방법이다.Specifically, the cells are different

Value, and any one cell used in adjacent cells

When both the values and the time shift values of the sounding sequence are known, the joint CE method is used to estimate the channel while avoiding the cross correlation problem. The average CE is a method of estimating a channel by averaging a certain number of received signals manipulated using a sounding signal, and the joint CE removes a matrix portion consisting of a sounding signal from a vector of a certain number of received signals through a matrix operation. By estimating the channel.

매트릭스(matrix)의 인버전(inversion)이 필요하다. 상기

는 고려되는 단말기의 수이고, 상기 U가 클 경우 구현 복잡도가 크게 증가한다. 비록

가 매우 크지 않은 경우라도, 복잡도를 고려해 평균 CE를 사이클릭 쉬프트 분리의 기본 채널추정 방식으로 선택할 수 있다. 그러나, 만약 해당 기지국의 인접 셀들의 단말기들이 상기 기지국 내부의 셀 단말기들과 다른

값을 사용할 경우, 결과적으로 생성된 사운딩 시퀀스들 간에 크로스 상관이 발생한다. 상기 크로스 상관 문제는 채널 추정에 있어서, 평균 CE 방법의 부정확성을 일으키는 문제점이 있다. In the case of the joint CE, for each band which is a frequency unit of data transmission set by a scheduler

Inversion of the matrix is required. remind

Is the number of terminals to be considered, and the implementation complexity greatly increases when the U is large. Although

Even if is not very large, the average CE can be selected as the basic channel estimation method of the cyclic shift separation in consideration of the complexity. However, if the terminals of the neighbor cells of the base station is different from the cell terminals inside the base station

Using a value, cross correlation occurs between the resulting sounding sequences. The cross correlation problem has a problem of inaccuracy of the average CE method in channel estimation.

Therefore, in order to improve the complexity and correlation problem, first perform an average CE, and based on this, terminals of "one antenna number -1" among the terminals of neighboring cells of the base station that are most affected by interference. Next, the channel may be estimated by performing the joint CE again on only the selected terminals.

3 is a flowchart illustrating a channel estimation method of a base station according to an exemplary embodiment of the present invention. Here, the case of performing only the average CE method will be described, but as described above, a method of combining the average CE and the joint CE may be performed.

In step 300, the base station determines whether sounding sequence information is available from terminals of neighbor cells. If the determination result is available, the base station determines in step 302 whether orthogonality of sounding sequences between internal cells and adjacent cell terminals is maintained. If orthogonality is maintained as a result of the checking, in step 304, the base station estimates a channel by applying an average CE method.

If the determination is not available, the base station proceeds to step 304.

If the orthogonality is not maintained as a result of the checking, in step 308, the base station determines whether the system complexity is very large. If the system complexity is very large, the base station performs channel estimation by applying an average CE in step 310 and proceeds to step 312.

In step 312, the base station selects a user whose M <U by user selection. U is the number of terminals considered and M is the number of terminals selected by the user. That is, the user selects M terminals less than the U and proceeds to step 314. In step 314, the base station performs channel estimation through the joint CE for the selected M terminals.

If the system complexity is not large as a result of the checking, the base station performs joint channel estimation by applying a joint CE in step 316.

Hereinafter, a method of linearly interpolating and storing a channel according to a permutation method according to the fourth embodiment of the present invention will be described.

For example, in a WiBro system, representative permutation methods related to BF are B-AMC and PUSC. A method of linearly interpolating and storing estimated channels for the B-AMC and the PUSC will now be described. At this time, it is assumed that the calculation of the BF weight is performed based on the stored channel, and the estimation channel is performed through the first to third embodiments.

일 경우, 상기 빈과 그룹(group)이 일대일로 대응되므로 각 그룹의 채널 값을 빈 단위로 쉽게 저장할 수 있다. 상기 그룹은 하나 이상의 서브채널들의 묶음으로 여기서는 일정 개수임을 가정한다. 다음으로,

일 경우, 한 그룹의 채널 값이 한 빈에 저장되던지, 두 그룹의 채널 값들이 평균되어 한 빈에 저장된다. 두 그룹의 채널 값들이 평균되어 한 빈에 저장될 경우, 겹치는 톤 수에 따라 상이한 웨이트가 적용된다.Firstly, in the case of B-AMC BF, the estimated channel is linearly interpolated and stored. In this case, the channel information by sounding is stored in a bin unit consisting of nine subcarriers.

In this case, since the bin and the group correspond to one-to-one, the channel value of each group can be easily stored in an empty unit. The group is a bundle of one or more subchannels and is assumed to be a certain number here. to the next,

In this case, the channel values of one group are stored in one bin, or the channel values of two groups are averaged and stored in one bin. When the two groups of channel values are averaged and stored in one bin, different weights apply according to the number of overlapping tones.

인 경우이다.4 is a diagram illustrating an example of a method of storing estimated channel values according to a fourth embodiment of the present invention. Here,

If

인 경우 즉,

=16인 경우로 빈1(404)의 채널 추정값은

이고, 빈 3의 채널 추정값은

다. 이때, 빈 2(406)는 그룹1(400)과 그룹2(402)의 톤 들이 겹친다. 상기 톤은 한개의 서브캐리어 혹은 OFDM의 부반송파를 의미한다. 이때, 겹치는 톤 수에 따라 상이한 웨이트가 적용되기 때문에, 상기 빈 2(406)의 채널 추정 값은 자신의 앞과 뒤의 채널 추정값 _와 _의 평균 값으로 하기 <수학식 16>과 같이 계산된다.Referring to Figure 4,

In other words,

= 16, the channel estimate of bin 1 404 is

And channel estimate of bin 3 is

All. At this time, the bin 2 406 overlaps the tones of the group 1 (400) and the group 2 (402). The tone means a subcarrier of one subcarrier or OFDM. In this case, since different weights are applied according to the number of overlapping tones, the channel estimation value of the bin 2 406 is calculated as shown in Equation 16 as an average value of the channel estimation values _ and _ before and after. .

경우이다.5 is a diagram illustrating an example of a method of storing estimated channel values according to a fourth embodiment of the present invention. Here,

If it is.

인

4개로 구성되고, 상기 그룹2(504)는 추정 채널값이

인

4개로 구성되고, 상기 그룹3(506)은 추정 채널값이

인

4개로 구성된다. Referring to FIG. 5, bin 1 500 is composed of nine subcarriers, and channel estimates of group 1 502, group 2 504, and group 3 506 overlap. The group 1 502 has an estimated channel value

sign

The group 2 504 has an estimated channel value.

sign

The group 3 506 has four estimated channel values.

sign

It consists of four.

Since the bin 1 overlaps three channel values, a different weight is applied to the number of overlapping tones, so that the channel estimate of the bin 1 is calculated as an average of the estimated channel values of the overlapping groups as shown in Equation 17 below. .

Secondly, in the case of PUSC-BF, the estimated channel value is stored.

6 is a diagram illustrating a method of storing estimated channel values in the case of PUSC-BF according to a fourth embodiment of the present invention.

Referring to FIG. 6, in the PUSC, tones of one logical subchannel 602 are scattered into tones in a corresponding group (608). The tones are rotated into successive logical clusters and then scattered back to the physical tones that exist in the entire frequency band (610).

Subchannels in a group produce six or four physically contiguous 14 tones. Therefore, to facilitate the application of interference nulling, one group is set to be used by only one user on one OFDM symbol. That is, as one group, for example, G0 is randomly scattered among a plurality of physical clusters (610), so that a pair of terminals having the best orthogonal condition is each Given differently for physical clusters, it is difficult to apply SDMA (Space Division Multiple Access). Accordingly, the PUSC performs interference nulling using only BF without applying SDMA. At this time, the channel storage method is similar to the case of the B-AMC, but instead of the bin consisting of nine subcarriers as a unit of the cluster consisting of 14 subcarriers. The weight of the average for channel storage is determined according to the relative position of a cluster with a given P _c value, and the weight of the average for channel storage is determined according to the relative position of a bin with a given P _c value in B-AMC. Is the same as In the case of PUSC, the length of the sounding sequence is equal to the entire frequency domain, and channel estimation is performed for the entire frequency domain. This is because channel estimation for the entire frequency domain is necessary because the tones of the logical subchannels in the PUSC are spread to all the physical subcarriers. In actual DL-BF, only the necessary channel values are extracted from the stored channel information.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The channel estimation method and the estimation channel storage method according to the present invention may be applied to a WiBro system and used as a unit for calculating a DL-BF weight at a base station. That is, for the case where the sounding sequence of the terminal located in the inner cell and neighboring cells of the corresponding base station has orthogonality, the average CE method and the joint for the target terminal and the neighboring cell terminals are reduced in order to reduce the complexity of the system. By suggesting a method of estimating the channel by combining the CE method, the estimated channel is estimated in units of P _c , and the manipulation (9 tones or 14 tones) is used according to the permutation method of the WiBro system. By storing channel information after manipulation, and calculating the DL-BF weight in the manipulation unit, by solving the inconsistency between the sounding parameter P _c and the given permutation number (9 or 14). This improves performance, improves convenience of management, and saves memory.

Claims (44)

In a method for storing a channel in a communication system, Storing the subcarriers of the channel estimated by sounding in one unit consisting of a predetermined number of combinations according to channel characteristic values; And mapping the unit to one or more groups generated by dividing the subchannels into a predetermined number of subchannels constituting the channel. The method of claim 1, wherein the mapping process, And when at least two or more units are mapped to the group, setting the average of the channel characteristic values of each unit as a channel characteristic value of the corresponding group. The method of claim 1, wherein the unit, The channel storage method of claim 9, characterized by consisting of nine subcarriers. The method of claim 1, wherein the channel characteristic value, Check whether orthogonality is maintained between sounding sequences between the inner cell and the terminals of the neighboring cell.If the orthogonality is maintained as the result of the checking, the channel is estimated using the first channel estimation method, and the orthogonality is not maintained as the result of the checking. If not, the channel storage method estimated by determining whether the system complexity is very large. The method of claim 4, further comprising: performing channel estimation through the first channel estimation method when the system complexity is very large; Selecting fewer terminals than the number of terminals considered by the user selection; And performing channel estimation on the selected terminals using a second channel estimation scheme. 6. The method of claim 5, further comprising performing channel estimation using the second channel estimation method when the system complexity is not large as a result of the determination. The method of claim 5, wherein the first channel estimation method, The channel storage method, characterized in that the channel estimate is calculated through the following equation. Equation

Where

Is the i-th base station

at the a-th antenna

v-th terminal

Is the channel estimate of. 8. The method of claim 7, wherein

Is, The channel storage method, characterized in that estimated by the following equation. Equation

Where

Is

Of the -th base station

Through the first antenna

The received signal on the -th subcarrier, and

Is the sounding sequence of the v-th terminal, and denotes a cyclic shift period. The method of claim 5, wherein the second channel estimation method, The channel storage method, characterized in that calculated as follows. Equation

Where

,

,

,

The channel storage method according to claim 1, wherein the sounding vector received by the a-th antenna and the g-th group of the i-th base station, the received signal in the frequency domain, and the noise and channel estimate value. The method of claim 9, wherein the equation is, The channel storage method of claim 1, wherein the first and second conditions must be satisfied. The method of claim 10, wherein the first condition is: remind

In order for the two arbitrary columns to be different from each other, the cyclic shift separation in order to satisfy the two different column conditions, so that the terminals belonging to one cell have different time shift values. Generate a ding sequence or use different offsets between terminals belonging to different cells.

And a sounding sequence using the value of. The method of claim 8, wherein the second condition is,

And a smaller value satisfies a condition for preventing a noise enhancement effect, in which the size of the noise portion becomes larger. In a method for storing a channel in a communication system, Estimating subcarriers of the channel by sounding over the entire frequency domain; Rotating the subcarriers of the estimated channel by configuring one unit consisting of a predetermined number of combinations according to channel characteristic values; And regrouping the units into only necessary portions for the entire frequency band. The method of claim 13, wherein the unit, The channel storage method, characterized in that the cluster consisting of 14 subcarriers. The method of claim 13, wherein the channel characteristic value, Check whether orthogonality is maintained between sounding sequences between the inner cell and the terminals of the neighboring cell.If the orthogonality is maintained as the result of the checking, the channel is estimated using the first channel estimation method, and the orthogonality is not maintained as the result of the checking. If not, the channel storage method estimated by determining whether the system complexity is very large. The method of claim 15, further comprising: performing channel estimation through the first channel estimation method when the system complexity is very large. Selecting fewer terminals than the number of terminals considered by the user selection; And performing channel estimation on the selected terminals using a second channel estimation scheme. 17. The method of claim 16, further comprising: performing channel estimation using the second channel estimation method when the system complexity is not large as a result of the determination. The method of claim 16, wherein the first channel estimation method, The channel storage method, characterized in that the channel estimate is calculated through the following equation. Equation

Where

Is an estimate of the channel from the a-th antenna of the i-th base station to the v-th terminal. 19. The method of claim 18, wherein

Is, The channel storage method, characterized in that estimated by the following equation. Equation

Where

Is a signal received on the v-th subcarrier through the a-th antenna of the i-th base station, and

Is the sounding sequence of the v-th terminal,

Denotes a cyclic shift period. The method of claim 16, wherein the second channel estimation method, The channel storage method, characterized in that calculated as follows. Equation

Where

,

,

,

The channel storage method according to claim 1, wherein the sounding vector received by the a-th antenna and the g-th group of the i-th base station, the received signal in the frequency domain, and the noise and channel estimate value. The method of claim 9, wherein the equation is, The channel storage method of claim 1, wherein the first and second conditions must be satisfied. The method of claim 21, wherein the first condition, remind

In order for the two arbitrary columns to be different from each other, the cyclic shift separation in order to satisfy the two different column conditions, so that the terminals belonging to one cell have different time shift values. Generate a ding sequence or use different offsets between terminals belonging to different cells.

And a sounding sequence using the value of. The method of claim 21, wherein the second condition is,

The smaller channel value satisfies the condition of preventing a noise enhancement effect, in which the size of the noise portion becomes very large. In a communication system, a method of channel estimation, Checking whether orthogonality is maintained between sounding sequences between terminals of an inner cell and an adjacent cell; Estimating a channel using a first channel estimation method when the orthogonality is maintained as a result of the checking; And if the orthogonality is not maintained, determining whether the system complexity is very large. 25. The method of claim 24, further comprising: performing channel estimation through the first channel estimation method when the system complexity is very large; Selecting the number of terminals less than the number of terminals considered by the user selection, and performing channel estimation on the selected terminals using a second channel estimation scheme. 27. The method of claim 25, further comprising performing channel estimation using the second channel estimation method when the system complexity is not large as a result of the determination. 25. The method of claim 24, wherein the first channel estimation scheme is: Check whether orthogonality is maintained between sounding sequences between the inner cell and the terminals of the neighboring cell.If the orthogonality is maintained as the result of the checking, the channel is estimated using the first channel estimation method, and the orthogonality is not maintained as the result of the checking. If not, the channel estimation method estimated through the process of determining whether the system complexity is very large. 28. The method of claim 27, further comprising: performing channel estimation through the first channel estimation method when the system complexity is very large; Selecting fewer terminals than the number of terminals considered by the user selection; And performing channel estimation on the selected terminals by using a second channel estimation scheme. 29. The method of claim 28, further comprising performing channel estimation using the second channel estimation method when the system complexity is not large as a result of the determination. The method of claim 27, wherein the first channel estimation method, The channel estimation method, characterized in that the channel estimate is calculated through the following equation. Equation

Where

Is an estimate of the channel from the a-th antenna of the i-th base station to the v-th terminal. The method of claim 30, wherein

Is, The channel estimation method, characterized in that estimated by the following equation. Equation

Where

Is a signal received on the k-th subcarrier through the a-th antenna of the i-th base station, and

Is the sounding sequence of the v-th terminal,

Denotes a cyclic shift period. The method of claim 28, wherein the second channel estimation method, The channel estimation method is calculated as in the following equation. Equation

Where

,

,

,

The channel estimation method according to claim 1, wherein a sounding vector received through the a-th antenna and the g-th group of the i-th base station, a received signal in the frequency domain, and a noise and channel estimate value. 33. The method of claim 32, wherein the equation is The channel estimation method of claim 1, wherein the first and second conditions must be satisfied. The method of claim 33, wherein the first condition is remind

In order for the two arbitrary columns to be different from each other, the cyclic shift separation in order to satisfy the two different column conditions, so that the terminals belonging to one cell have different time shift values. Generate a ding sequence or use different offsets between terminals belonging to different cells.

And a sounding sequence using a value of. The method of claim 33, wherein the second condition is,

The smaller channel value satisfies a condition for preventing a noise enhancement effect, in which the size of the noise portion becomes very large. The method of claim 25, wherein the second channel estimation method, Check whether orthogonality is maintained between sounding sequences between the inner cell and the terminals of the neighboring cell.If the orthogonality is maintained as the result of the checking, the channel is estimated using the first channel estimation method, and the orthogonality is not maintained as the result of the checking. If not, the channel estimation method estimated through the process of determining whether the system complexity is very large. 37. The method of claim 36, further comprising: performing channel estimation through the first channel estimation method when the system complexity is very large as a result of the determination; Selecting fewer terminals than the number of terminals considered by the user selection; And performing channel estimation on the selected terminals by using a second channel estimation scheme. 38. The method of claim 37, further comprising performing channel estimation using the second channel estimation method when the system complexity is not large as a result of the determination. The method of claim 37, wherein the first channel estimation method, The channel estimation method, characterized in that the channel estimate is calculated through the following equation. Equation

Where

Is an estimate of the channel from the a-th antenna of the i-th base station to the v-th terminal. 40. The method of claim 39, wherein

Is, The channel estimation method, characterized in that estimated by the following equation. Equation

Where

Is

a signal received on the v-th subcarrier through an a-th antenna of the i-th base station, and

Is the sounding sequence of the v-th terminal,

Denotes a cyclic shift period. The method of claim 36, wherein the second channel estimation method, The channel estimation method is calculated as in the following equation. Equation

Where

,

,

,

The channel estimation method according to claim 1, wherein a sounding vector received through the a-th antenna and the g-th group of the i-th base station, a received signal in the frequency domain, and a noise and channel estimate value. 42. The method of claim 41, wherein the equation is The channel estimation method of claim 1, wherein the first and second conditions must be satisfied. 42. The method of claim 41, wherein the first condition is remind

In order for the two arbitrary columns to be different from each other, the cyclic shift separation in order to satisfy the two different column conditions, so that the terminals belonging to one cell have different time shift values. Generate a ding sequence or use different offsets between terminals belonging to different cells.

And a sounding sequence using a value of. 42. The method of claim 41 wherein the second condition is

The smaller channel value satisfies a condition for preventing a noise enhancement effect, in which the size of the noise portion becomes very large.

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