JP2001177460A - Wireless receiver and wireless reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high speed transmission without being affected by an environment of a propagation path and deteriorating the reception performance. SOLUTION: A 2nd channel estimation section 109 applies FFF filtering to the output from an array synthesis section 102 to obtain an input sequence for an array element. A replica signal is obtained by using a tap coefficient of a TVF, and a channel is estimated and a tap coefficient is obtained by using an error signal between a synthesis signal of the input sequence and the replica signal. This tap coefficient is fed to a directivity conversion section 113, where the tap coefficient is converted into directivity information. An average section 114 averages the directivity information. The averaged directivity information is fed to a null angle detection section 115, which detects a null angle on the basis of the averaged directivity information. The null angle information is fed to a pseudo-interference section 116, which generates an interference wave arrived from the obtained null angle and a 3rd channel estimation section 117 estimates a tap coefficient for array synthesis to suppress it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radio receiving apparatus and a radio receiving method in a digital radio communication system.

[0002]

2. Description of the Related Art In a next-generation mobile communication system, high-speed transmission (several tens of Mbps) is required along with an increase in demand for data communication.
Is required. However, since the time length of one symbol is relatively shortened by the high-speed transmission, there is a problem that an apparent delayed wave looks long.

As a countermeasure against this, an adaptive equalizer is known as an effective technique. However, it is difficult to compensate for all the delayed waves to be considered in real time by the equalizer in terms of the amount of calculation and the current device capability. It is.

For example, the delay time in a typical urban area is about 5
When the transmission rate is 20 Mbps, one symbol time is 50 ns, so that a delayed wave of 100 symbols is seen. Thus 100
It is very difficult to process all of the symbol delay waves in real time with an equalizer.

[0005] Therefore, it has been reported that a process for removing such a long delay wave in the direction of arrival and an adaptive array reception process are combined with an equalizer (1999 IEICE Communications Society Conference B).
-5-42). In the configuration according to this report, each of the array elements in the L branch is provided with an N-tap filter for the purpose of absorbing a synchronization shift, and in the subsequent stage, an MLSE (Maximum Likelihood Sequence Estimation: Maximum
Likelihood Sequence Estimation) is cascaded.

Therefore, in this configuration, channel estimation is performed for (L × N + M) taps at once. Here, if L = 16, N = 3, and M = 4, there are 52 taps. Normally, among the adaptive algorithms used in channel estimation, the fastest convergence is RLS (Recursive Le
It is said that even if the ast square) algorithm is used, it takes twice the number of symbols to be calculated until the channel estimation is completed. In other words, it takes 104 symbol times for channel estimation of 52 taps. This is not practical because the overhead is too large.

In view of the above, conventionally, there has been proposed a radio receiving apparatus having a configuration for separately estimating the tap coefficients of the array and the tap coefficients of the equalizer. In this radio receiving apparatus, as shown in FIG.
01-n are transmitted to the array combining section 60
In step 2, the adaptive array reception processing is performed and the signals are combined. The synthesized signal that has undergone the adaptive array reception processing is filtered by a feedforward filter (FFF) 603 to absorb a synchronization shift.

[0008] The filtered combined signal is sent to a maximum likelihood sequence estimator (MLSE) 604, where the channel is estimated and a signal determination is performed. The determined signal is sent to a transversal filter (TVF) 605 which is a replica generation unit. In the TVF 605, a replica signal is generated by performing a convolution operation on the determined signal.

This replica signal is output to adder 606. In the adder 606, the replica signal is subtracted from the synthesized signal that has passed through the FFF 603, and the difference is sent to the first channel estimation unit 607 as an error signal. The first channel estimator 607 performs channel estimation using the error signal, and obtains tap coefficients of the FFF 603 and the TVF 605. This tap coefficient is stored in the memory 608.

[0010] The second channel estimating section 609 includes a memory 60
Using the tap coefficients of the FFF stored in No. 8 to perform FFF filtering on the output from the array synthesis unit 602, an input sequence for the array elements is obtained. And memory 6
A replica signal is obtained by using the TVF tap coefficient stored in 08, and channel estimation is performed by using an error signal between the input sequence and the replica signal, thereby obtaining a tap coefficient of the array combining section 602. This tap coefficient is calculated by the array synthesis unit 60.
The adaptive array receiving process is performed on the received signal using the tap coefficient.

In this case, the switches 610, 611
Are switched under the control of the timing by the timing management unit 612.

In the radio receiving apparatus having the above configuration, attention is paid to the fact that the direction of arrival does not suddenly change, and the tap coefficients of the array are updated at certain time intervals.
The tap coefficients of the equalizer are updated in real time in consideration of the fact that the propagation environment fluctuates due to the moving speed even during about s. With such a configuration, the amount of calculation is reduced and real-time operation by the equalizer is enabled.

[0013]

However, with such a configuration, sufficient reception performance cannot be obtained. This may be due to the fact that the tap coefficients of the array are updated at certain time intervals. That is, if the level of the interference wave at the time of updating the tap coefficients of the array happens to be extremely small due to fading fluctuation, it is determined that the target is not a target to which null is directed, and the tap coefficient is estimated, and this tap coefficient is reflected as the tap coefficient of the array. You. In this case, if the level of the interference wave is increased by the next update timing, null is not directed, so that it becomes inevitable large interference, which is a cause of deterioration of reception performance.

The present invention has been made in view of such a point, and can greatly improve the performance as compared with a configuration in which the array and the equalizer are separated and controlled without being affected by the propagation path environment.
It is an object of the present invention to provide a wireless receiving device and a wireless receiving method that can support high-speed transmission.

[0015]

A radio receiving apparatus according to the present invention forms a directivity by using a channel estimation result obtained by using a received signal, and detects a null angle from the directivity. A signal generating means for generating a signal arriving from the null angle in a pseudo manner, a tap coefficient calculating means for obtaining an array tap coefficient so as not to capture the signal, and a plurality of antenna elements, An adaptive array receiving means for performing an adaptive array receiving process on a received signal using a tap coefficient is adopted.

According to this configuration, in the adaptive array reception, a pseudo interference wave is generated from the null angle and the tap coefficient is obtained based on the interference wave, so that the reception is performed without being affected by the propagation path environment. It is possible to cope with high-speed transmission without deteriorating performance.

The radio receiving apparatus according to the present invention employs, in the above configuration, a configuration including an averaging means for averaging the directivity for a predetermined observation frame.

According to this configuration, the directivity is averaged for a predetermined number of observation frames, so that fluctuations in the propagation path environment can be absorbed. This makes it possible to specify the direction in which the interference wave exists without being affected by the propagation path environment.

The radio receiving apparatus according to the present invention employs a configuration having a timing control means for controlling the update timing of the array tap coefficient in the above configuration. According to this configuration, it is possible to perform an accurate adaptive array reception process.

The radio receiving apparatus according to the present invention employs a configuration in which the above configuration further includes a synchronization shift absorbing means for absorbing a synchronization shift between the plurality of array elements.

According to this configuration, the high-precision symbol synchronization required in the MLSE type equalizer is not required, and the processing can be simplified.

[0022] A wireless base station apparatus according to the present invention includes the wireless receiving apparatus. Further, a communication terminal device according to the present invention includes the above-mentioned wireless receiving device. As a result, it is possible to cope with high-speed transmission, to realize a calculation amount that cannot be realized by the conventional methods, and to realize wireless reception with excellent reception characteristics.

The radio receiving method according to the present invention forms a directivity using a channel estimation result obtained using a received signal, and detects a null angle from the directivity. A signal generation step of generating an incoming signal in a pseudo manner, a tap coefficient calculation step of obtaining an array tap coefficient so as not to take in the signal, and an adaptive array reception process using the array tap coefficient for a received signal. And performing an adaptive array receiving step.

According to this method, in the adaptive array reception, a pseudo interference wave is generated from the null angle and the tap coefficient is obtained based on the interference wave, so that the reception is performed without being affected by the propagation path environment. It is possible to cope with high-speed transmission without deteriorating performance.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention estimate the tap coefficients of an array at certain update timings. When the tap coefficients of the array are updated, the level of the interference wave happens to be extremely small due to fading fluctuation. It is noted that the tap coefficient is estimated because it is determined that the tap coefficient is not a target to be turned.

This will be described with reference to FIGS. It is assumed that an existing path is in a state shown in FIG. As shown in FIG. 3A, the desired wave 301 and the interference wave 3
In the case where the levels of 02 are almost equal, as shown in FIG. 3B, a tap coefficient for forming a directivity pattern 304 that turns null in the arrival direction of the interference wave 302 is estimated. In FIG. 3B, reference numeral 303 denotes a receiving point (wireless receiving device).

At the update timing with the tap coefficients of the array, as shown in FIG. 4A, when the level of the interference wave 302 becomes smaller due to the effect of fading, as shown in FIG. Directivity pattern 305
Is such that null is hardly directed to the arrival direction of the interference wave.

When this directivity pattern is used until the next update timing, as shown in FIG. 5A, the level of the interference wave to which no null is directed (the level is low) during this period becomes so large that it cannot be ignored. In this case, as shown in FIG. 5B, the interference wave 302 is captured. For this reason,
The deterioration of the reception performance becomes severe.

Therefore, the present inventors use the information obtained by estimating the tap coefficients in a state that is not influenced by fading fluctuations (ie, the static characteristics) in the adaptive array reception processing corresponding to the high-speed transmission for estimating the tap coefficients of the array. Thus, the present inventors have found that deterioration of reception characteristics can be prevented, and have accomplished the present invention. That is, the gist of the present invention is that, in the adaptive array reception processing corresponding to the high-speed transmission, the state of FIG.
By determining the tap coefficient estimated in step (1), it is possible to prevent reception characteristic deterioration without being influenced by fading fluctuation.

Here, there is a problem how to estimate the tap coefficient in the same manner as under the static characteristic. In the present invention,
First, the estimated tap coefficients of the array are converted to directivity, and the arrival direction (direction of null) of the interference wave is estimated with a relatively long average time. Thereby, fading fluctuation is absorbed. Then, an interference wave coming from the direction of the null is artificially created, and a tap coefficient for forming directivity such that a null is directed to the interference wave is obtained from the information on the arrival direction. In this way, since a pseudo interference wave is created in the wireless receiving device and null is directed to the pseudo interference wave, the tap coefficient is estimated using a signal that is not affected by the propagation path at all. Can be.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a configuration of a wireless reception device according to one embodiment of the present invention. The signals received via the antenna elements 101-1 to 101-n are subjected to adaptive array reception processing in the array combining unit 102 and combined. The synthesized signal subjected to the adaptive array reception processing is filtered by a feedforward filter (FFF) 103 to absorb a synchronization shift. This eliminates the need for high-precision symbol synchronization required in the MLSE-type equalizer, and can simplify the processing.

The filtered synthesized signal is sent to a maximum likelihood sequence estimator (MLSE) 104, where the channel is estimated and a signal determination is performed. The determined signal is sent to a transversal filter (TVF) 105 which is a replica generation unit. In the TVF 105, a convolution operation is performed on the determined signal to generate a replica signal.

This replica signal is output to adder 106. In the adder 106, the replica signal is subtracted from the synthesized signal that has passed through the FFF 103, and the difference is sent to the first channel estimation unit 107 as an error signal. The first channel estimator 107 performs channel estimation using the error signal, and obtains tap coefficients of the FFF 103 and the TVF 105. This tap coefficient is stored in the memory 108.

The second channel estimating unit 109 is provided in the memory 10
Using the tap coefficients of the FFF stored in No. 8, FFF filtering is performed on each of the antenna inputs 101-1 to 101-n to obtain an input sequence for array elements. Then, a replica signal is obtained by using the tap coefficients of the TVF stored in the memory 108, channel estimation is performed by using an error signal between the composite signal of the input sequence and the replica signal, and an array tap coefficient is obtained.

The tap coefficients are sent to the directivity conversion unit 113 and are converted into directivity information (information on the input levels of the desired wave and the interference wave and their arrival angles). If the observation frame is A
In the case of (A: the number of frames for averaging the directivity), this tap coefficient is also sent to the array synthesis unit 102. This directivity information is averaged by the averaging unit 114. Here, if the observation frame is A or more, the averaged directivity information is sent to the null angle detection unit 115. The null angle detection unit 115 detects a null angle based on the averaged directivity information (information of a pseudo interference wave). The null angle information is sent to the pseudo interference wave generation unit 116.
The pseudo interference wave generator 116 generates an interference wave arriving from the null angle in accordance with the null angle information.
The third channel estimation section 117 estimates tap coefficients for array synthesis so as to suppress this. The tap coefficients are sent to the array synthesizing section 102, and the received signals are subjected to adaptive array reception processing using the tap coefficients.

In this case, the switches 110 and 111
Are switched under the control of the timing by the timing management unit 112.

The operation of estimating tap coefficients under static characteristics in the radio receiving apparatus having the above configuration will be described.

The timing management unit 112 manages a predetermined number of observation frames for averaging the directivity of the array and an update timing of the tap coefficient of the array. First, if the number of observation frames is less than the predetermined number, the update timing is updated. , Tap coefficients are obtained by the first and second channel estimations, and an adaptive array receiving process is performed on the received signal using the tap coefficients.

When the number of observation frames is equal to or more than a predetermined number, a control signal is output to the switch 110 when the update timing comes. The switch 110 switches the switch according to the control signal from the timing management unit 112 so that the combined signal from the array combining unit 102 is sent to the second channel estimation unit 109.

In the second channel estimating section 109, the memory 1
08 and the FF obtained by the first channel estimation.
Each of the antenna inputs 101-1 to 101-1 using the tap coefficient of F
FFF filtering is performed on 01-n to obtain an input sequence for array elements. Then, a replica signal is obtained by using the tap coefficients of the TVF stored in the memory 108, channel estimation is performed by using an error signal between the composite signal of the array input sequence and the replica signal, and the tap coefficients are obtained.

The tap coefficients obtained by second channel estimation section 109 are input to directivity conversion section 113. The directivity conversion unit 113 converts the tap coefficient from the second channel estimation unit 109 into directivity information, that is, information on the input levels of the desired wave and the interference wave and their arrival angles. In particular,
By correlating with a phase signal generated at an angle interval between -180 ° and 180 ° with respect to the tap coefficient,
Directivity information can be obtained.

After the directivity information is stored in the averaging unit 114, it is sent to the null detection unit 115. The null detection unit 115 detects a null angle from information on the arrival angle of an interference wave having a predetermined level or more. The null angle detection information is sent to the pseudo interference wave generation unit 116. In the pseudo interference wave generator,
A pseudo interference wave is generated from the obtained null angle information, and the third channel estimation unit 117 estimates tap coefficients so as to suppress the pseudo interference wave. This tap coefficient is sent to array combining section 102, and array combining section 102 performs an adaptive array receiving process on the received signal using the tap coefficient.

As described above, first, the variation of the propagation path environment can be absorbed by converting the tap coefficients of the array into directivity and averaging them for a predetermined number of observation frames.
This makes it possible to specify the direction in which the interference wave exists without being affected by the propagation path environment. Also, from the averaged directivity information, the angle at which the null points is detected, a signal arriving from the null angle is pseudo-generated, and the tap coefficient is calculated so as not to capture this pseudo interference wave. The tap coefficient can be estimated in a state where no distortion on the propagation path is added. As a result, it is possible to perform wireless reception in a state that is hardly affected by fluctuations in the propagation environment. Further, since the adaptive array reception processing and the equalizer are combined, it is possible to cope with high-speed transmission with a small amount of calculation.

Next, the radio reception method of the present invention will be described with reference to the flowchart of FIG. Step (hereinafter, ST
In the initial state, tap coefficients for the array synthesizing unit 102, the FFF 103, and the TVF 105 are initialized in an initial state. Next, array synthesis is performed on the received signal (ST202). However, immediately after the initialization, until the tap coefficients of the array are reflected, a process of simply adding the signals that have passed through the array elements 101-1 to 101-n is performed (the tap coefficients that are set in the initial setting). Is set).

Next, the tap coefficients of the FFF 103 and the TVF 105 are estimated by using the output signal of the array synthesis (synthesized signal), and the FFF 103 and the TVF 105 are estimated.
(ST203).

Next, in the control of the timing management section 112, if it is not the update timing of the tap coefficient of the array, the process returns to ST202. If it is the update timing (ST204), the FFF and TV determined in ST203
The tap coefficients of the array are estimated using the tap coefficients of F (ST205), and the result is reflected on the array tap coefficients of ST202. Further, the tap coefficients are converted to directivity and averaged (ST206). Next, when the number of observation frames is smaller than A (the number of frames that take an average of directivity with a certain integer), the process returns to ST202. If the angle is equal to or larger than A, a null angle is detected from the averaged directivity (ST20).
8) Then, an interference wave arriving from the detected null angle is artificially generated (ST209), and a tap coefficient for suppressing the interference wave is estimated (ST210). ST20
2 is reflected in the array tap coefficient. The above process is repeated.

The radio receiving apparatus and the radio receiving method of the present invention can be applied to a communication terminal apparatus such as a radio base station apparatus and a mobile station in a digital radio communication system. As a result, it is possible to cope with high-speed transmission, and to realize wireless reception with a small amount of calculation and excellent reception characteristics.

The present invention is not limited to the above embodiment, but can be implemented with various modifications.

[0049]

As described above, the radio receiving apparatus and the radio receiving method of the present invention have a configuration in which the adaptive array and the equalizer are combined, and perform the estimation in the adaptive array reception in the same situation as under the static characteristic. Since the tap coefficients are determined, it is possible to cope with high-speed transmission without deteriorating the reception performance without being affected by the propagation path environment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a wireless reception device according to one embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the wireless reception device according to one embodiment of the present invention;

FIG. 3 is a diagram showing a relationship between a desired wave and an interference wave and directivity.

FIG. 4 is a diagram illustrating a relationship between a desired wave and an interference wave and directivity.

FIG. 5 is a diagram showing a relationship between a desired wave and an interference wave and directivity.

FIG. 6 is a block diagram showing a configuration of a conventional radio receiving apparatus.

[Explanation of symbols]

 101-1 to 101-n Antenna element 102 Array synthesis unit 103 Feedforward filter 104 Maximum likelihood sequence estimation unit 105 Transversal filter 106 Adder 107 First channel estimation unit 108 Memory 109 Second channel estimation unit 110, 111 Switch 112 Timing Management unit 113 Directivity conversion unit 114 Averaging unit 115 Null angle detection unit 116 Pseudo interference wave generation unit 117 Third channel estimation unit 301 Desired wave 302 Interference wave

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J021 AA05 AA06 CA06 DB02 DB03 EA04 FA06 FA16 FA20 FA25 FA26 FA29 FA30 FA32 GA02 HA05 HA10 5K052 AA01 BB02 DD03 DD04 FF02 FF05 FF29 FF32 5K059 CC03 CC04 DD33 DD37 DD39

Claims (7)

[Claims] 1. A null angle detecting means for forming a directivity by using a channel estimation result obtained by using a received signal and detecting a null angle from the directivity, and simulating a signal coming from the null angle. Signal generating means for generating an array tap coefficient so as not to take in the signal, and a plurality of antenna elements, the adaptive signal receiving process using the array tap coefficient for receiving a signal. Wireless receiving apparatus comprising: 2. An averaging means for averaging the directivity for a predetermined number of observation frames.
The wireless receiving device according to claim 1. 3. The radio receiving apparatus according to claim 1, further comprising timing control means for controlling an update timing of an array tap coefficient. 4. The apparatus according to claim 1, further comprising a synchronization shift absorbing means for absorbing a synchronization shift between the plurality of array elements.
The wireless receiver according to any one of claims 1 to 3. 5. A wireless base station device comprising the wireless receiving device according to claim 1. 6. A communication terminal device comprising the wireless receiving device according to any one of claims 1 to 4. 7. A null angle detecting step of forming a directivity using a channel estimation result obtained using a received signal and detecting a null angle from the directivity, and generating a signal arriving from the null angle in a pseudo manner. Generating an array tap coefficient so as not to capture the signal, and an adaptive array receiving step of performing an adaptive array receiving process on a received signal using the array tap coefficient. And a wireless receiving method.