KR200425883Y1 - Apparatus for estimating channel in communication system supporting OFDM/OFDMA - Google Patents

Abstract

The present invention relates to an apparatus for estimating a channel at a base station when using a PUSC mode in an uplink channel of a communication system supporting an OFDM / OFDMA scheme.

To this end, the present invention is an apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme using a PUSC mode for an uplink channel, the phase change of the channel using pilots included in the signal input in sub-channel units A phase estimation compensator for estimating and compensating for the signal; And a channel estimator for estimating a channel by averaging pilots of the phase-compensated signal.

Description

Apparatus for estimating channel in communication system supporting OFDM / OFDMA}

1 is a structural diagram of a logical signal transmitted when a PUSC mode is used in an uplink channel of a communication system supporting an OFDM / OFDMA scheme.

2 is a structure diagram of a receiver in a communication system supporting an OFDM / OFDMA scheme in a PUSC mode for an uplink channel.

3 is a block diagram of a channel estimating apparatus according to the present invention.

4 is a structural diagram of pilots of each tile.

5 is a flowchart illustrating an operation process of a channel estimating apparatus according to the present invention.

The present invention relates to an apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme, and more particularly, to a base station when using a partial usage of subchannels (PUSC) mode in an uplink channel of a communication system supporting the OFDM / OFDMA scheme. Relates to an apparatus for estimating a channel in.

Recently, in the wireless communication system, active researches are being conducted to provide users with services having various Quality of Service for transmitting large amounts of data at high speed. In particular, high-speed in the form of ensuring mobility and quality of service in a broadband wireless access (BWA) communication system such as a wireless local area network system and a wireless metropolitan area network system. Researches to support the service are actively being conducted, and representative communication systems are the Institute of Electrical and Electronics Engineers (IEEE) 802.16a communication system and the IEEE 802.16e communication system.

The IEEE 802.16a communication system and the IEEE 802.16e communication system provide orthogonal frequency division multiplexing (OFDM) / orthogonal frequency division multiple access (OFDMA) to support a broadband transmission network on a physical channel of the wireless MAN system. This is a communication system applying the method. The IEEE 802.16a communication system is a system in which a subscriber station (SS) is currently fixed, that is, a state in which the mobility of the SS is not considered at all and only a single cell structure is considered. In contrast, the IEEE 802.16e communication system is a system considering mobility of an SS in the IEEE 802.16a communication system, and the SS having the mobility is referred to as a mobile subscriber station (MSS).

Similarly, Wibro (Wireless Broadband Internet), a domestic wireless mobile Internet standard, uses a signal transmission method called OFDM to enable high-speed data service even when a user is moving in a wireless environment. In addition, the multiple access method called OFDMA based on OFDM is used so that multiple users can receive Internet service at the same time.

In a communication system supporting the OFDM / OFDMA scheme, the channel change in the frequency domain is caused by the following causes. That is, the phase change of the channel experienced by the signal in the frequency domain may vary according to the position of the fast fourier transform (FFT) received from the receiver, and the channel in the frequency domain according to the delay difference of the multipath channels received in the time domain. Will change.

In this way, a communication system in which a channel change occurs makes a channel estimation in order to adapt to a channel change, and for this purpose, the transmitter inserts and transmits a pilot in the frequency domain so as to be used for channel estimation.

The receiver then uses the transmitted pilot to make a channel estimate to compensate for the distortion of the data portion between the pilots, which are averaged by adding the pilots or multiplying the pilots by different weights, and estimating the channel by adding them. There are ways.

For example, if the difference between the pilots in the frequency domain is small, using the channel estimation method of adding the pilots and averaging can reduce the effect of noise, but there is a difference in the channels. Can cause errors in channel estimation.

In addition, the channel estimation method of multiplying and adding pilots to other weights compensates for channel differences by giving weights to pilots in close proximity. At this time, if the weights are the same, it is the same as the channel estimation method of adding and averaging the pilots. If the weights are different, the noise is reduced to the estimated channel while adapting well to the channel change. That is, in the channel estimation method of multiplying and adding pilots to other weights, the influence of noise or channel difference varies depending on the weight.

Therefore, there is a demand for a method for estimating a channel that is not affected by noise or channel difference.

Accordingly, an object of the present invention is to provide an apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme using a PUSC mode for an uplink channel.

Another object of the present invention is to provide an apparatus for estimating a channel by estimating and compensating a phase using a pilot in a communication system supporting an OFDM / OFDMA scheme using a PUSC mode for an uplink channel.

To this end, the present invention is an apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme, phase estimation compensation for estimating and compensating for a phase change of a channel using pilots included in a signal input in subchannel units Wealth; And a channel estimator for estimating a channel using pilots of the phase-compensated signal.

The phase estimation compensator may include: a pilot extractor configured to extract pilots for each tile constituting the subchannel from a signal input in the subchannel unit; A phase change estimator estimating a phase in units of the subchannels using the extracted pilots; And a phase compensator configured to compensate the phases of the extracted pilots by using the estimated phase.

The channel estimator may include: an average unit configured to calculate representative values of each tile by adding and averaging the phase-compensated pilots in tile units; And a phase reflecting unit estimating a channel to be used for data compensation by using the representative values of each tile and the estimated phase.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Since the present invention relates to a channel estimating apparatus, it is applied to a receiver. In particular, since the present invention relates to an apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme using a PUSC mode for an uplink channel, a receiver to which the present invention is applied is, for example, a RAS (Radio Access Station) serving as a base station. Can be

In addition, the logical structure of a signal transmitted when a PUSC mode is used for an uplink channel in a communication system supporting an OFDM / OFDMA scheme is shown in FIG. 1. As shown in FIG. 1, one subchannel includes 6 tiles, and each tile includes 4 pilots and 8 data. One subchannel is formed over three OFDMA symbols. When these signals are transmitted, they are carried on different subcarriers (subcarriers) in units of tiles.

The receiver to which the present invention is applied includes a radio frequency (RF) module 210, an FFT module 220, a deramdomizer 230, and a depermutation module 240 as shown in FIG. 2. , A channel estimator 250, and a channel compensator 260.

The RF module 210 converts a signal of a radio frequency band received by an antenna into a signal of a low frequency band. The FFT module 220 converts the signal of the low frequency band of the time domain into the signal of the frequency domain. The derandomizer 230 multiplies a signal in the frequency domain transformed by the FFT module 220 by canceling the same random number that was multiplied by the signal at the time of transmission from the transmitter. The demutation module 240 collects tiles transmitted on different subcarriers in subchannel units. The signals gathered in subchannel units are input to the channel estimator 250. The value estimated by the channel estimator 250 is input to the channel compensator 260 and used to compensate the channel. The present invention is directed to a channel estimator 250 of these components.

The signal input to the channel estimator 250 is processed in subchannel units. As illustrated in FIG. 1, the tiles constituting the subchannel are carried on different subcarriers, and thus, each subcarrier undergoes a constant phase change due to a time delay. The present invention relates to an apparatus for estimating such phase change.

The present invention is largely divided into a part of estimating and compensating for a phase change of a channel using pilots included in a signal input in sub-channel units, and a part of estimating a channel by averaging pilots of the phase-compensated signal.

The channel estimator according to the present invention has a phase estimation compensator 310 for estimating and compensating for a phase change of a channel using pilots included in a signal input in units of subchannels as shown in FIG. The channel estimator 320 estimates a channel by averaging pilots of a signal, and estimates a channel in a communication system supporting an OFDM / OFDMA scheme using a PUSC mode for an uplink channel.

More specifically, the phase estimation compensator 310 estimates a phase change of a channel by using a pilot extracted from a pilot extractor 312 and a pilot extractor 312 for extracting pilots from a signal input in sub-channel units. A phase compensator 316 for compensating phases in units of tiles with respect to the pilot extracted by the pilot extractor 312 using the phase change estimator 314 and the phase change estimated by the phase change estimator 314. It consists of. The channel estimator 320 estimates the average and phase change estimator 314 of the average unit 322 that averages the pilots of the signal whose phase is compensated by the phase compensator 316, and the average unit 322. The phase reflection unit 324 estimates a channel to be used for data compensation using the phase shift.

The pilot extractor 312 extracts only the pilot from the subchannel unit signal input to the channel estimating apparatus. That is, the pilot extractor 312 extracts four pilots for each tile from six tiles included in one subchannel. If the pilots of each tile configuration as shown in Figure 4, the output signal from the pilot extracting section 312 it may be expressed by a set {P _{i, 1,} P _{i, 2,} P _{i, 3,} P _{i, 4}.} Where i is i = 0,... , Which is an index of tiles forming one subchannel of 5.

The phase change estimator 314 estimates the phase change in subchannel units. The phase change occurs as shown in Equation 1 in the signal in the frequency domain according to the position of FFT the signal received at the receiver.

Where r (n) is the signal after the FFT when there is an error in the position, s (n) is the signal after the FFT at the correct position, θ is the phase value generated by the FFT position, and n is the index of the subcarrier. That is, θ is a phase difference between adjacent subcarriers.

According to Equation 1, it can be seen that the phase increases as the subcarrier index increases. The phase change estimator 314 estimates θ causing the phase change in the subcarriers using the pilot extracted in the subchannel unit by the pilot extractor 312.

To this end, the phase change estimator 314 is configured to perform conjugation multiplication with pilots that are separated by three subcarriers for each of the two pilots on the same frequency axis among the four pilots in each tile constituting the subchannel. Conjugation Multiplication. And arctan is added by adding the conjugation far applied in tile unit for one subchannel. The arctan is then divided by 3, which is the difference between the subcarrier positions of the two pilots, to find the phase θ. If this is expressed as equation (2).

Where P _{i , 1} , P _{i , 2} , P _{i , 3} , and P _{i , 4} represent four pilots included in one tile as shown in FIG. 4. And i is i = 0,... , Which is an index of tiles forming one subchannel of 5.

The phase compensator 316 compensates the phase in units of tiles with respect to the pilot extracted by the pilot extractor 312 using the phase θ estimated by the phase change estimator 314.

The average unit 322 adds the phase-compensated pilot in the tile unit in the phase compensator 316 and averages P _i. Calculate the value. Where i is i = 0,... , Which is an index of tiles forming one subchannel of 5. In more detail, the output of the average unit 322 may be represented by Equation 3 below.

In order to compensate for the channel in the data by using the P _i value representing each tile calculated by the average unit 322, the phase in the data must be reflected in P _i , and this function is applied to the phase reflector 324. Perform on

The phase reflector 324 calculates a channel to be used for data compensation by using the representative value P _i of the tile unit and θ obtained by the phase change estimator 320 in subchannel units. To this end, the phase reflector 324 multiplies the signals of the first subcarrier 410 of each tile by 1 for each tile having the structure as shown in FIG. 4, and the exp (jθ) of the signals of the second subcarrier 420. ), Multiply the signals of the third subcarrier 430 by exp (j2θ), and the signals of the fourth subcarrier 440 by multiplying exp (j3θ) by four values, Pi * {1, e ^{j θ} , e ^{j2 θ} , e ^{j3 θ} } is transmitted to the channel compensator 260 of FIG. Where i is i = 0,... , Which is an index of tiles forming one subchannel of 5. The channel compensator 260 then uses the four values for channel compensation according to the subcarrier position of the data in each tile.

5 is a flowchart illustrating an operation process of a channel estimating apparatus according to the present invention, which will be described below with reference to the components of FIG. 3.

First, when the pilot extractor 312 extracts pilots for each tile constituting the subchannel from a signal input in subchannel units (S510), the phase change estimator 314 uses the extracted pilots to extract the pilots. The phase is estimated in channel units (S520). Then, the phase compensator 316 compensates for the phases of the extracted pilots using the estimated phase (S530).

When the phases of the pilots are compensated in operation S530, the average unit 322 calculates representative values of each tile by adding and averaging the phase-compensated pilots in tile units (S540) and representing each tile calculated in operation S540. The channel to be used for data compensation is estimated using the values and the phase estimated in step S520 (S550).

Detailed description thereof is the same as the description of FIG. 3 described above, and thus description thereof will be omitted.

Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art to which the present invention pertains can be implemented in other specific forms without changing the technical spirit or essential features, The examples are to be understood in all respects as illustrative and not restrictive.

And, the scope of the present invention is specified by the utility model registration claims to be described later than the above detailed description, and all changes or modifications derived from the meaning and scope of the utility model registration claims and the equivalent concept of the present invention It should be construed as being included in the scope.

The present invention compensates the phase change estimated by the phase change estimator 314 in the phase compensator 316 to remove the phase change present in the signal received by the receiver and to average the pilot in the average unit 322. You can get the value.

In the present invention, the phase change estimator 314 estimates the phase change in units of subchannels to estimate the exact phase change. In addition, the average unit 322 may reduce the influence of noise by adding and averaging the pilots in each tile.

Claims (8)

An apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme, A phase estimation compensator for estimating and compensating for a phase change of a channel by using pilots included in a signal input in sub-channel units; And a channel estimator for estimating a channel using pilots of the phase-compensated signal. The method of claim 1, The phase estimation compensator, A pilot extracting unit extracting pilots for each tile constituting the subchannel from the signal input in the subchannel unit; A phase change estimator estimating a phase in units of the subchannels using the extracted pilots; And And a phase compensator for compensating for the phases of the extracted pilots using the estimated phases. The method according to claim 1 or 2, The channel estimator, An average unit configured to calculate representative values of each tile by adding and averaging the phase-compensated pilots in tile units; And a phase reflector for estimating a channel to be used for data compensation using the representative values of each tile and the estimated phase. The method of claim 3, The phase change estimator, Conjugation multiplication is performed for each of the tiles in the tile by conjugation and conjugation of the pilots in each tile with the pilots spaced apart by subcarriers of a predetermined position for each of the two pilots in the same frequency axis. After arctan by adding the value for one subchannel, the phase is estimated by dividing the arctan by a value corresponding to the subcarrier position difference between the two pilots, and estimating the phase in a communication system supporting an OFDM / OFDMA scheme. Device. An apparatus for estimating a channel in a communication system supporting an OFDM / OFDMA scheme, A radio frequency (RF) module for converting a signal of a radio frequency band received from a terminal through an antenna into a signal of a low frequency band; A Fast Fourier Transform (FFT) module for converting the low frequency band signal into a frequency domain signal; A deramdomizer for canceling a random number transmitted from the terminal with respect to the signal in the frequency domain; A depermutation module for combining and outputting a signal in the frequency domain from which the random number is canceled in subchannel units; And OFDM comprising: a channel estimator for estimating and compensating for a phase change of a channel using pilots included in the frequency domain signal of the subchannel unit, and for estimating a channel using pilots of the phase-compensated signal; Channel Estimation System in a Communication System Supporting the & OFDMA System. The method of claim 5, The channel estimator, A pilot extractor configured to extract pilots for each tile constituting the subchannel from a frequency domain signal in units of the subchannels; A phase change estimator estimating a phase in units of the subchannels using the extracted pilots; A phase compensator for compensating for the phases of the extracted pilots using the estimated phase; An average unit configured to calculate representative values of each tile by adding and averaging the phase-compensated pilots in tile units; And And a phase reflector for estimating a channel to be used for data compensation using the representative values of each tile and the estimated phase. The method of claim 6, The phase change estimator, Conjugation multiplication is performed for each of the tiles in the tile by conjugation and conjugation of the pilots in each tile with the pilots spaced apart by subcarriers of a predetermined position for each of the two pilots in the same frequency axis. After arctan by adding the value for one subchannel, the phase is estimated by dividing the arctan by a value corresponding to the subcarrier position difference between the two pilots, and estimating the phase in a communication system supporting an OFDM / OFDMA scheme. Device. The method according to claim 6 or 7, And estimating the channel by reflecting each of the estimated phases according to the positions of subcarriers constituting each tile and multiplying by representative values of each tile to estimate the channel.

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