KR20030028111A - Space-Time Array Receiver System in the CDMA system and Receiving method - Google Patents

Abstract

PURPOSE: A space-time array receiving system in a CDMA(Code Division Multiple Access) and a method thereof are provided to easily cancel signals of several users located at the same region in a CDMA system under a multi path channel environment, thereby enhancing amount of a reverse direction channel. CONSTITUTION: A signal processing unit(20) consists of a multi-channel array receiver(21) which changes a plurality of signals received from an array antenna(10) into a base band digital signal. An arrival angle and beam coefficient estimator(23) estimates an arrival angle and beam formation coefficient of the received signal on the basis of a signal outputted from the multi-channel array receiver(21). A digital beam formation device(22) forms an optimum directional beam by multiplying a signal outputted from the multi-channel array receiver(21) by an estimated beam formation coefficient. A rake receiver(24) combines a signal outputted from the digital beam formation device(22) with the maximum ratio in order to maximize a signal power to noise of a user's signal to noise power. An adaptation plural user detector(25) cancels an identical channel interference signal to a signal outputted from the rake receiver(24). A controller(26) discriminates whether a user are positioned at the same position on the basis of an arrival angle of an estimated user, then controls the adaptation plural user detector(26) according to the result and performs a plural user detection method on the users positioned at the same position.

Description

Space-Time Array Receiver System in the CDMA system and Receiving method}

The present invention relates to a base station system for code division multiple access (CDMA), and more particularly, to a space-time array receiving system using a multi-user detection method for each user group in a multipath channel environment, and to receiving the same. It is about a method.

In general, a signal received during wireless communication includes a desired signal (hereinafter, referred to as an original signal) and an interference signal, and a plurality of interference signals exist for one original signal. Since the degree of communication distortion caused by such an interference signal is determined by the sum of the original signal power and all other signal powers, the total power of the interference signal is increased when the number of the interference signals is large even when the level of the original signal is significantly higher than the level of each of the interference signals. This becomes large and communication distortion occurs. Therefore, the information distortion of the original signal becomes difficult due to such communication distortion.

In order to solve this problem, an array antenna technology has been developed and used in a wireless communication system.

The array antenna represents an antenna in which a plurality of trend unit antennas are arranged in a predetermined direction in order to increase the directivity of the antenna. As a method of processing a signal received through the array antenna, an adaptive beamforming technique and an angle of arrival estimation technique are used.

The adaptive beamforming technique detects the direction of the user when the user (mobile subscriber) is in a call and increases the gain of the antenna in that direction, and decreases the gain of the antenna in the other direction, thereby minimizing interference between the same cells. . In this adaptive beamforming technique, radio waves are directionally transmitted and received according to the spatial distribution of users, thereby increasing power efficiency, reducing unnecessary interference, and ultimately improving communication quality, service radius per base station, and subscriber capacity. Will increase.

However, the conventional adaptive beam array antenna system has a disadvantage in that when multiple users are located in the same area, each user signal cannot be removed from each other.

Meanwhile, in addition to such an array antenna system, a multi-user detection technique is used as a method for detecting an original signal from a plurality of interference signals. The multi-user detection technique is a method for improving reception performance at a base station by detecting signals of other users that are considered noise in an existing CDMA system and suppressing or eliminating interference by other users.

However, this technique is very easy to apply to systems where the number of users and spreading rate is limited (3GPP WCDMA TDD: 3rd Generation Partnership Project Wideband Code Division Multiple Access Time Division Duplex system), but the number of users or array antenna is large. The computational complexity of the ground multi-user detection technique is significantly increased.

Recently, a method for interworking such a multi-user detection technique and an array antenna system is disclosed in Korean Patent Publication No. 2000-0002214 ("Interference Cancellation System Using Antenna Array in a Multipath Environment").

However, in the interference cancellation system using the antenna array, since all received signals of the user are input to the interference cancellation stage, the interference cancellation stage needs to perform an operation to remove the interference component for all user signals, and also the original interference cancellation stage. Since there is a large amount of calculation to remove the interference component at, the computational complexity still has a significant increase.

Therefore, the technical problem to be achieved by the present invention is to solve the disadvantages of the prior art, in the CDMA base station system in a multi-path channel environment to facilitate the removal of a number of user signals located in the same area with each other, thereby improving the reverse channel capacity I'm going to sleep.

In addition, the technical problem to be achieved by the present invention is to reduce the complexity and calculation amount of the calculation by applying a multi-user detection method for each user group located in the same area.

1 is an exemplary diagram of a reverse link channel environment of a space-time array receiving system in a code division multiple access system according to an embodiment of the present invention.

2 is an overall structural diagram of a space-time array receiving system in a code division multiple system according to an embodiment of the present invention.

3 is a detailed structural diagram of a space-time array receiving system in a code division multiple system according to an embodiment of the present invention.

4 is a schematic flowchart of a method for receiving a space-time array in a code division multiple system according to an embodiment of the present invention.

5 is a diagram illustrating a method of estimating angle of arrival according to an exemplary embodiment of the present invention.

According to an aspect of the present invention, a space-time array receiving system in a code division multiple access system according to an aspect of the present invention provides a multi-channel array for converting a multipath signal of multiple users received from an array antenna into a baseband digital signal. receiving set; A controller for determining a degree of simultaneous location of users based on the multi-path signal of each user, and outputting a control signal for removing interference signals for each group of simultaneous users according to the determination result; And an adaptive multi-user detector for receiving a control signal from the controller as an input and removing the co-channel interference signal included in each user-specific signal.

The apparatus further includes an angle of arrival and beamforming coefficient estimator for estimating angle of arrival and beamforming coefficients for each user and multipath signals based on the signals output from the multichannel array receiver. In this case, the controller determines the degree of simultaneous location of users based on each user's arrival angle information for each multipath signal. In particular, the controller compares the arrival angles of the path signals having the maximum power among the multipath signals of the users. Determine the degree of simultaneous positioning.

And a digital beamformer for performing spatial filtering by forming an optimal directional beam by multiplying the signal output from the multichannel array receiver by the beamforming coefficients of the angle of arrival and the beamforming coefficient estimator; And a rake receiver configured to provide a maximum ratio of multipath signals for each user to the adaptive multi-user detector with respect to multipath signals of each user output from the digital beamformer.

On the other hand, the adaptive multi-user detector detects the original signal by grouping the input signals based on the control signal of the controller with the co-located user signals, and performing the multi-user interference cancellation for each group. To this end, the adaptive multi-user detector includes: a multi-user interference canceller for each group that detects an original signal by performing multi-user interference cancellation for each co-located user group; A single user detector for detecting an original signal with respect to a signal of a single user not co-located; And a selector configured to provide a signal output from the rake receiver to the multi-user interference canceller for each group or to the single-user detector according to a control signal of the controller.

A receiving method of a space-time array receiving system of a code division multiple access system according to another aspect of the present invention comprises the steps of: a) determining whether there are concurrently located users based on a multipath signal of each user received through an array antenna; ; b) grouping concurrently located users, and performing multi-user interference cancellation on each user signal for each group to detect the original signal; And c) detecting the original signal by performing a single user interference cancellation on the user signal for each single user not co-located.

In addition, d) estimating the angle of arrival for each user and the multi-path signal received through the array antenna. In this case, step a) of determining the degree of co-location, compares the estimated angles of arrival of each multi-path signal of each user to determine whether there are co-located users, and in particular, the multi-path signal of each user. The degree of arrival of the path signal having the maximum power is compared to determine the degree of simultaneous users.

And e) multiplying the multipath signals of each user by beamforming coefficients to form an optimal directional beam to perform spatial filtering; And f) maximally combining the multipath signals for each user with respect to the spatially filtered multipath signals of each user. In this case, steps b) and c) of detecting the original signal perform multi-user interference cancellation or single-user interference cancellation on the signals of the spatially filtered and maximally combined users, respectively.

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

1 illustrates a reverse link channel environment of a space-time array receiving system in a code division multiple system according to an embodiment of the present invention.

As shown in FIG. 1, the application of an array antenna using an adaptive beamforming technique to a base station is not only to increase power efficiency but also unnecessary interference (user # 3) by directionally transmitting and receiving radio waves according to spatial distribution of users. This is a valid way to reduce both user and user # 4).

However, when the user # 1 and the user # 2 are located at the same spatial position, the beams LC of the two users formed by the space-time array antennas are the same, so that the user # 1 and the user # 2 each have unnecessary interference. Signals from 2 and user # 1 cannot be removed. In this case, the user # 1 and the user # 2 are located at the same location, and the two users are defined as "co-location".

The space-time array receiving system in the code division multiple system according to the embodiment of the present invention is a group of users co-located with respect to users who could not be distinguished by the existing array antenna system when the users are co-located with each other. Multiple user detection schemes are applied for each to distinguish users from each other to remove interference from each other.

2 schematically shows the overall structure of a space-time array receiving system (hereinafter, referred to as an array antenna receiving system) in a code division multiple system according to an embodiment of the present invention having this feature.

In an array antenna receiving system according to an embodiment of the present invention, an array antenna 10 including a plurality of antenna elements for receiving signals transmitted from terminals of a plurality of users, a signal for processing a signal received from the array antenna 10 It consists of a processing unit 20.

The signal processor 20 converts a plurality of signals received from the array antenna 10 into baseband digital signals, and the signals received based on the signals output from the multichannel array receiver 21. The angle of arrival and beamforming coefficient estimator 23 for estimating the angle of arrival and the beamforming coefficient of the digital beam former multiplying the signal output from the multi-channel array receiver 21 by the estimated beamforming coefficient to form an optimal directional beam ( 22, or a spatial filter), a rake receiver 24 that combines the signal output from the digital beamformer 22 to a maximum ratio to maximize the ratio of signal power to interference and noise power for the user signal, Adaptive multi-user detector 26 that removes co-channel interference signals for signals output from rake receiver 24, based on the angle of arrival of the estimated user signal Determining that the concurrent position, and a controller 25 for the multi-user detection method to be performed by the co-location user controls the adaptive multi-user detector (26) according to the determination result.

3 illustrates the structure of the array antenna receiving system in the embodiment of the present invention having such a structure in more detail.

The number of fingers in the rake receiver 24 determines the number of digital beam formers 22, angles of arrival and beamforming coefficient estimators 23. In this example, three examples are used to receive and process three multipath signals transmitted from four users, but the present invention is not limited thereto.

Meanwhile, as shown in FIG. 3, an adaptive multi-user detector for selectively removing a co-channel interference signal by selectively performing a multi-user detection scheme on a signal output from the rake receiver 24 under the control of the controller 25 ( 26 includes a selector 261, a multi-user interference canceller 262 per group, and a single user detector 263.

The selector 261 is configured to provide the multi-user interference canceller 262 for each group to be processed by the signals transmitted from the co-located users among the signals output from the rake receiver 24 under the control of the controller 25. Among the signals output from the receiver 24, signals transmitted from non-simultaneous users are provided to the single user detector 263 for processing.

Here, the multi-user interference canceller 262 for each group eliminates interference of signals according to the multi-user detection scheme used in the code division multiple access system, and this interference cancellation technique is already known and thus a detailed description thereof will be omitted.

Next, an operation of the array antenna reception system according to the embodiment of the present invention having such a structure will be described.

Figure 4 is a simplified view of the receiving method of the array antenna receiving system according to an embodiment of the present invention. First, the angle of arrival for each user is estimated using the signal input from the multi-channel array receiver (S100 to S110). Next, it is determined whether there are concurrently located users by comparing the estimated angles of arrival of each estimated user (S120), and based on the determined information, the simultaneously located user signals pass through the digital beam former and the rake receiver (BF). Users located at the same time are grouped, and the original signal is detected by applying the multiple user interference cancellation method (GW-MUD) for each group of users located at the same time (S130 to S140). On the other hand, user signals that are not co-located with other users are passed through the digital beam former and the rake receiver (BF), and the original signal is detected by applying a single user detection method (SUD) for each user signal (S150).

In more detail, the operation received by the array antenna 100 in a multipath channel environment is first converted into a digital signal through the multichannel array receiver 21, and then a searcher of a demodulator (not shown). Is used for initial synchronization acquisition and multipath search.

The digitally converted signal is input to the angle of arrival and the beamforming coefficient estimator 23 and at the same time for each user (1-K) and for each path (1-L) estimated as a signal previously received by the digital beamformer 22. ) Is multiplied by the beamforming coefficients and then summed.

The signal is band despread for each path based on finely tuned path delay profile information at each finger in the rake receiver 24 and then maximum ratio synthesized.

As such, the user-specific signal having the maximum ratio synthesized for each path is input to the adaptive multi-user detector 26 to remove interference signals. The adaptive multi-user detector 26 is a user input under the control of the controller 25. Adaptive interference cancellation is performed on the star signal.

On the other hand, the PN code output from the pseudo noise (PN) code generator of each finger in the rake receiver 24 is fed back to the input of the angle of arrival and the beamforming coefficient estimator 23 to generate a reference signal for estimating the angle of arrival and the beamforming coefficient. Used for

The angle of arrival and the beamforming coefficient estimator 23 estimate the angle of arrival and the beamforming coefficient for each user and each path based on the reference signal generated according to the PN code. 5 illustrates a method of estimating angle of arrival according to an embodiment of the present invention. The angle of arrival and the beamforming coefficient estimator 23 form a plurality of beams predetermined for each sector, and then compare the received signal in the direction of each beam with the reference signal generated by the rake receiver to use the most received beam. The angle of arrival of the user is estimated.

The estimated angle of arrival information is input to the controller 25. The controller 25 compares the angle of arrival of the path with the maximum power for each user to determine whether the users are simultaneously located (e.g., when the angle of arrival is the same). To remove the interference for each concurrently positioned user according to the determination result, and control the adaptive multi-user detector 26 such that users who are not concurrently positioned are applied with a single user detection method for each user. do.

The signal output from the rake receiver 24 is first input into the selector 261 of the adaptive multi-user detector 26, and the selector 261 receives the input signal according to the control signal provided from the controller 25. Input to eliminator 262 or single user detector 263.

For example, as shown in FIG. 1, since user # 1 and user # 2 are simultaneously located among four users, user # 1 and user # 2 signals are distinguished from each other by a space-time array antenna system. And since the cancellation is not performed, the signals of the user # 1 and the user # 2 that passed through the rake receiver 24 are passed through the multi-user interference canceller 262 for each group to detect the original signal from which the interference has been removed. On the other hand, since the user # 3 and user # 4 signals can be spatially separated and removed by the space-time array antenna system, the user # 3 and user # 4 signals passing through the rake receiver are transferred to the single user detector 263. Input to detect the signal from which interference has been removed.

Meanwhile, the complex beamforming coefficient of the digital beam former 22 receives the PN codes of the rake receiver 24 and the signal received through the multi-channel array receiver 21 as inputs, and the angle of arrival and beamforming coefficient estimator 23 are input. Is updated through an adaptive control process. Then, the angle of arrival and the complex beamforming coefficients of the beamforming coefficient estimator 23 are independently updated.

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 embodiment of the present invention, in a multipath environment, by applying a multi-user detection method for each group of concurrently located users, communication efficiency can be reduced by increasing power efficiency due to optimal directional beam formation and reducing unnecessary interference. Quality can be improved and service radius per base station and subscriber capacity can be increased.

In addition, since the multi-user detection method is applied to the spatially separated user signals by the space-time array receiving system, the calculation amount of the interference cancellation stage can be significantly reduced than the conventional method. Therefore, the implementation of the multi-user detection scheme, which has not been applicable to an actual system since the computational amount increases rapidly as the number of users increases so far, can be easily achieved by interworking with the space-time array antenna system.

Claims (10)

A space-time array reception system of a code division multiple access system in a wireless multipath channel environment, A multi-channel array receiver for converting a multipath signal of a plurality of users received from the array antenna into a baseband digital signal; A controller for determining a degree of simultaneous location of users based on the multi-path signal of each user, and outputting a control signal for removing interference signals for each group of simultaneous users according to the determination result; An adaptive multi-user detector that receives a control signal from the controller and removes co-channel interference signals included in each user's signal Space-time array receiving system in a code division multiple system comprising a. The method of claim 1, Further comprising an angle of arrival and beamforming coefficient estimator for estimating angle of arrival and beamforming coefficients for each user and multipath signal based on the signals output from the multichannel array receiver; And the controller determines the degree of simultaneous location of users based on the angle of arrival information for each multipath signal of the user. The method of claim 2, The controller may compare the angle of arrival of the path signal having the maximum power among the multi-path signals of each user to determine the degree of simultaneous location of the users. The method of claim 2, A digital beamformer for performing spatial filtering by forming an optimal directional beam by multiplying the signal output from the multichannel array receiver by the beamforming coefficients of the angle of arrival and the beamforming coefficient estimator; And Rake receiver for providing the adaptive multi-user detector by combining the maximum ratio of the multipath signals for each user with respect to the multipath signals of each user output from the digital beamformer Space-time array receiving system in the code division multiple system further comprising. The method according to claim 1 or 4, The adaptive multi-user detector groups signals inputted on the basis of control signals of the controller among the co-located user signals and detects the original signal by performing multi-user interference cancellation for each group. Space-time array receiving system. The method of claim 5, The adaptive multi-user detector, A multi-user interference canceller for each group detecting the original signal by performing the multi-user interference cancellation for each user group located at the same time; A single user detector for detecting an original signal with respect to a signal of a single user not co-located; And A selector for providing a signal output from the rake receiver to the multi-user interference canceller for each group according to the control signal of the controller or to the single-user detector Space-time array receiving system in a code division multiple system, characterized in that consisting of. In the space-time array reception method of a code division multiple access system in a wireless multipath channel environment, a) determining whether there are concurrently located users based on the multipath signal of each user received via the array antenna; b) grouping concurrently located users, and performing multi-user interference cancellation on each user signal for each group to detect the original signal; And c) detecting the original signal by performing a single user interference cancellation on the user signal for each non-simultaneously located user; Space-time array receiving method in a code division multiple system comprising a. The method of claim 7, wherein d) estimating the angle of arrival for each user and multipath signal received via the array antenna, In the step a) of determining the degree of co-location, the estimated angles of the multi-path signals of each user are compared with each other to determine whether there are users co-located. How to receive time array. The method of claim 8, In the step a) of determining the degree of co-location, in the code division multiple system, the degree of simultaneous location of the users is determined by comparing the angles of arrival of the path signals having the maximum power among the multi-path signals of the respective users. Space-time array reception method. The method of claim 7, wherein e) multiplying the multipath signals of each user by beamforming coefficients to form an optimal directional beam to perform spatial filtering; And f) maximally combining the multipath signals for each user with respect to the spatially filtered multipath signals of each user More, B) and c) steps for detecting the original signal perform multi-user interference cancellation or single-user interference cancellation on the signals of the spatially filtered and maximally uncoupled users, respectively. -How to receive a time array.