JP2003283404A - Array antenna wireless communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array antenna wireless communication apparatus for keeping the circuit scale small, allowing a searcher to detect a path with high accuracy and estimating a path arrival direction even in the case of employing an array antenna comprising many antenna elements. <P>SOLUTION: A beam former 31 of the searcher 30 forms beams for searching for a plurality of paths, a correlation processing section 32 applies inverse spread to each of a plurality of the beams, power conversion and average processing are applied to the processed beams and produces a delay profile 35 of the paths. A path arrival detection section 36 detects the path timing and the path arrival direction on the basis of the delay profile of the plurality of beams. The path arrival detection section 36 outputs the information to a reception demodulation section 20 for its path timing for the inverse spread processing and its weight update of the beam form. Further, the searcher 30 utilizes the path arrival direction information for forming a succeeding beam. Since the searcher 30 is provided only with the correlation processing sections 32 by the number of beams to be formed, the circuit scale can be kept small. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array antenna wireless communication device, and more particularly to a searcher for detecting a path timing of a received signal in a wireless communication device using an adaptive array antenna in a DS-CDMA digital cellular wireless communication system. Technology for path detection and path direction of arrival estimation.

[0002]

2. Description of the Related Art Earlier application by the same applicant as the present applicant (Japanese Patent Application No. 2000-270508, September 6, 2000)
In the invention related to “array antenna wireless communication device”,
As a means for improving the deterioration of the detection accuracy of the path detection using the received signal of one antenna, which is performed in the array antenna receiving apparatus of the conventional DS-CDMA wireless communication system, the received signals of a plurality of antennas are used. We have devised a means to improve the accuracy of path detection by performing path detection, and to speed up the beam formation in the adaptive array antenna receiving section by estimating the arrival direction of the path by the searcher.

FIG. 4 shows the configuration of the array antenna baseband received signal processing section of the array antenna radio communication apparatus according to the previous application. A radio frequency signal received by each antenna element of the array antenna 10 is converted into a baseband signal by a frequency conversion unit (not shown), and then discretely quantized by an A / D converter (not shown) to generate a digital signal. The signal is converted into a baseband signal and input to the adaptive array antenna reception / demodulation unit 20 that performs beamforming / demodulation processing and the searcher 40 that performs path search.

All received signals of the array antenna 10 including a plurality of antenna elements are input to the searcher 40. In the searcher 40, a complex signal subjected to correlation processing with the spreading code for despreading in the correlation processing unit 41 for each antenna element is input to the antenna synthesis path timing detection unit 42 and the inter-antenna correlation estimation unit 43. It

In the antenna combining path timing detection unit 42, the power converter 421 converts the complex correlation value signal after the correlation processing (despreading processing) for each antenna into a power value, and then combines them in the combiner 422. . This is because when there is a path, a large received signal with almost the same level is obtained between each antenna element, and the signal component is multiplied by the number of antenna elements, whereas when there is no path, there is only a noise component. , Even if the random and small level signals are combined,
The noise components are averaged without being multiplied by the number of antenna elements, and the noise distribution for the signal after combining is suppressed as compared with that before combining, so that the signal-to-noise ratio (SN
Even if R) is low, highly accurate path timing detection can be performed.

Further, the combined signal of the received signal power of each antenna element is integrated and averaged for a predetermined time in an averaging unit 423, and fluctuations due to path fading are averaged to generate a delay profile 424. . Then, the bus detection unit 425 detects the path timing of the path exceeding the path detection threshold based on the delay profile 424, and outputs the detected timing pulse of the bus.

On the other hand, the inter-antenna correlation estimation section 43 inputs the complex signal subjected to the correlation processing for each antenna element,
The inter-antenna correlator 431 multiplies the correlation processing output complex number signals of each antenna element between adjacent antenna elements and then synthesizes them. By performing such a calculation, in an array antenna with an evenly spaced linear array configuration, the phase part of all multiplication results is in the direction of arrival angle of the path, so the noise components are averaged and canceled out by combining, The inter-antenna complex correlation value (phase term) corresponding to the arrival angle is added to obtain the noise suppression effect.

The inter-antenna correlating unit 431 calculates an inter-antenna element correlation estimation value, and the inter-antenna correlating unit 432 performs time averaging processing, and the inter-antenna element inter-element correlation is performed by the averaging effect including the path level fluctuation due to fading. The accuracy of the correlation estimation value is improved and the inter-antenna element correlation estimation value corresponding to each path timing of the delay profile 242 is obtained.

Adaptive array antenna reception demodulator 2
0 inputs the signal indicating the inter-antenna element correlation estimation value together with the bus timing signal from the searcher 40, and the finger allocating unit 21 performs finger allocation based on the path timing signal, and the despreading unit 22 for each finger. In, the despreading process is started at each pass timing.

Further, the adaptive array antenna reception / demodulation section 20 calculates the input inter-antenna element correlation estimation value as
The weight conversion unit 23 converts the weight value for beam forming of the array antenna by calculation or table reference, and outputs the weight value to the weight update unit 24.

The searcher 40 outputs a signal indicating the amount of phase rotation as an inter-antenna element correlation estimation value, and the weight conversion unit 23 converts the signal into a weight value. Instead, the weighter 40 calculates the weight value itself. The weight updating unit 24 may be directly input.

Adaptive array antenna reception demodulator 2
In 0, the beam forming weight obtained from the weight updating unit 24 is used, the beam forming process is performed on the signal obtained by despreading the received signal by the beam former 25, and the synchronous detection unit is performed on the beam formed signal. At 26, demodulation processing is performed. By using the estimated value of the inter-antenna element correlation obtained by the searcher 40 as the initial weight value of the beam former 25, the beam formation can be immediately performed in the position direction of the user (mobile station) to be communicated.

After that, the weight updating unit 24 updates the beam forming weight value of the array antenna using a known algorithm and performs beam forming in the direction of the position where the communication target exists. The weight value update can be converged at a higher speed than updating the weight value from the beam weight initial value in the direction unrelated to the direction. Therefore, beam formation can be performed quickly in the communication target direction, and the quality of received signals from users and transmitted signals to users can be improved. Further, when this configuration is applied to the user terminal, the transmission power of the user terminal can be reduced.

In the above configuration example, the weight updating unit 24 and the weight converting unit 23 are provided in common for all fingers, and the same weight value is used for signals of different paths on the same channel. This is an example of the configuration for forming one beam. However, in reality, the input directions of the radio waves arriving at the array antenna 10 may be different when the paths are different. Therefore, the weight updating unit 24 and the weight converting unit 23 are provided for each finger corresponding to each path, and each finger is provided for each finger. It is also possible to adopt a configuration (not shown) in which different weight values are set.

[0015]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The invention according to No. 0-270508) was able to improve the path detection accuracy of a wireless device to which an array antenna is applied and to speed up beam formation, but in the present invention, the correlation configured by a matched filter or the like is used. The number of processing (despreading processing) units 41 is required for the number of antenna elements, and the correlation processing unit is required to be provided in proportion to the increase in the number of antenna elements of the array antenna. Therefore, the circuit scale and the amount of calculation increase. There was a point.

According to the present invention, even when an array antenna composed of a large number of antenna elements is used, the correlation processing (despreading processing) section does not increase and similarly highly accurate path detection is performed and the path arrival direction is determined. It is an object of the present invention to provide an array antenna wireless communication device having a searcher capable of estimating and maintaining a small circuit scale.

[0017]

The array antenna radio communication apparatus of the present invention is (1) a DS-unit using an array antenna.
In a wireless communication device for CDMA mobile communication, a searcher for detecting a path timing of a received signal, and a reception demodulator for performing demodulation processing on a received signal of an array antenna for the detected path are provided. Beam forming means for forming a plurality of path search beams by an array antenna, means for generating a path delay profile for each of a plurality of beams formed by the beam forming means, and a delay profile based on the plurality of beams A path arrival detecting means for detecting a path timing for despreading processing in the reception demodulation section and estimating an arrival direction of the path, wherein the reception demodulation section receives a received signal based on a path timing from a searcher. And a means for despreading from the searcher as a reception weight value for array antenna beamforming. Or array reception demodulator using the arrival direction information of the scan as a reception weight value (fingers)
And a means for demodulating a received signal using the reception weight value estimated independently by the array receiver or using the reception weight value estimated by the array reception demodulator as the initial weight information of the direction of arrival of the path from the searcher. It is a thing.

(2) The searcher forms a beam smaller than the number of antenna elements of the array antenna, and based on the delay profile of each beam generated from the beam, the beam forming weight for the next path search. It is provided with a means for determining the value.

(3) The searcher uses a plurality of beam forming weight values prepared in advance having slightly different beam directions as beam forming beam forming weight values for the next path search. A means for determining a beam forming weight value is provided.

(4) The searcher forms two beams whose beam directions are adjacent to each other, and based on the delay profiles of the two beams, a beam having a delay profile with a high path level or a large number of paths ( Hereafter, the first beam will be referred to as "first beam") and the delay profile beam having a low path level or a small number of paths (hereinafter referred to as "second beam"), and the weight value of the first beam will be unchanged. A means for maintaining the weight value of the second beam and changing the weight value of the second beam to the weight value of the beam direction adjacent to the opposite side across the first beam to determine the beam forming weight value for the next path search. Be prepared.

(5) The searcher uses a weight value (hereinafter referred to as a "first weight value") for forming a plurality of beams having narrow beam widths and slightly different directions by using all antenna elements of the array antenna. , And a weight value for forming a beam with a wide beam width using only a part of the antenna elements of the array antenna (hereinafter referred to as “second
"Weight value". ) Is stored in advance, and when a path is not detected from the delay profile at the time of narrow beam forming by the first weight value, the beam forming weight value for the next path search is set by the second weight value. Changing to a wide beamforming weight value, and when forming a wide beam by the second weight value and a path is detected only from the delay profile of the one beam, beamforming for the next path search Means for changing the weight value of 1 to a weight value for forming a narrow beam by the plurality of first weight values covered by the beam of the second weight value.

[0022]

1 shows the configuration of an array antenna baseband received signal processing section according to the present invention. A radio frequency signal received by each antenna of the array antenna 10 is converted into a baseband signal by a frequency converter (not shown), and then discrete / quantized by an A / D converter (not shown) to obtain a digital baseband signal. The signal is converted into a signal and input to the adaptive array antenna reception demodulation unit 20 that performs beamforming / demodulation processing and the searcher 30 that detects path timing.

The searcher 30 according to the present invention inputs a signal from the array antenna 10 and a beam former 31 for forming a plurality of beams, and a correlation for performing a correlation process (a despreading process) on each received signal of the formed beams. A processing unit 32, a power conversion unit 33 that performs power conversion on the signal after the correlation processing, an averaging processing unit 34 that performs time averaging processing, and a plurality of delay profiles output from the averaging processing unit 34. A path arrival direction detection unit 36 that performs path timing detection and path arrival direction detection based on 35, a weight control unit 37 that determines and controls a weight value for beam forming of the beam former 31 from the path arrival direction, and the weight control. The weight value determined by the unit 37 is applied to the beamformer 31.
And a weight setting unit 38 for setting.

As the weight value of the beam former of the searcher 30, a plurality of different values are set according to an instruction from the weight controller 37. In addition, the weight control unit 37 and the path arrival direction detection unit 36 cooperate to estimate the path arrival direction based on the current weight value, and determine the weight value for the next beam formation based on the estimation result. Prepare

In FIG. 1, in the searcher 30, the array antenna 10 is used to form a beam by the beam former 31 based on the weight value set by the weight controller 37, and the correlation processor 32 performs correlation processing for each beam ( Despreading process). The correlation processing unit 32 performs correlation calculation with the spreading code by the matched filter and in-phase addition.

The signals after in-phase addition are subjected to power conversion by the power conversion unit 33 and time averaged by the averaging processing unit 34.
A delay profile 35 of the formed beam is generated. The path signal included in the formed beam can be detected with high accuracy by the beam forming gain of the array antenna.

By forming a beam by the array antenna and performing path detection, the detection accuracy of the path in the direction included in the formed beam is improved, but the path detection accuracy in the direction not included in the beam is rather deteriorated. I will end up. Therefore, how to form a beam is important.

When the path arrival direction changes every moment, it is necessary to have a function of forming a beam by following the changing path arrival direction. In order to realize this, a plurality of beams are formed and a delay profile is created for each beam. The number of beams may be smaller than the number of antenna elements, and the configuration example shown in FIG. 1 shows a configuration example in which two beams are formed.

The path arrival direction detecting section 36 detects the path timing from the plurality of delay profiles 35 to detect the path timing with high accuracy, and to follow the direction of the mobile station which changes momentarily, The path arrival direction is estimated by the method described below using the plurality of delay profiles 35.

A method of estimating the path arrival direction by following the mobile station will be described with reference to FIG. In the beam former 31 of the searcher 30, as shown in FIG.
Weight values are prepared so that eight types of beams from # 1 to eighth beam B # 8 can be formed. In FIG. 2, the horizontal axis represents the beam direction angle, and the vertical axis represents the beam intensity level.

Here, the weight values to be prepared are not limited to the set of weight values of orthogonal beams corresponding to the number of antenna elements to be used, but the weight values of a plurality of beams with slightly different beam directions filling the space between orthogonal beams. Values are prepared in advance to improve the accuracy of path timing detection and path arrival direction estimation.

The first different path arrival direction from the mobile station 50
The path P # 1 and the second path P # 2 of FIG. Now, the weight control unit 37 controls the fourth beam B.
Forming two beams of # 4 and fifth beam B # 5,
It is assumed that those delay profiles are being generated.

Here, assuming that the mobile station 50 has moved to the right in FIG. 2, in the path detection using the delay profiles of the fourth and fifth beams B # 4 and B # 5, the gain due to the beam formation is detected. A large level of the path due to the large fifth beam B # 5 is detected. Therefore, the path arrival direction detection unit 3
In 6, the arrival time of the path detected by the fifth beam B # 5 is detected as the path timing. Further, the direction angle of the fifth beam B # 5 is detected as the path arrival direction estimation value.

The beam to be formed next time is determined as follows based on the level information of the detected path in the path arrival direction detection unit 36. The two beams to be formed are always adjacent to each other. Of the two beams
The beam with the high level of the detected path is formed as it is, and the beam with the low level of the detected path is changed to the beam direction that is adjacent to the opposite side across the beam of the high detection level. The forming weight value is determined, and the delay profile of the beam is generated next time to perform path detection.

For each cycle of delay profile generation and path detection, only the beam with the smaller path detection level is
The change to the beam in the position direction adjacent to the opposite side of the beam having a high path detection level is repeated. When the mobile station moves to the right as shown in FIG. 2, the set of two beams formed is as follows. When moving: (B # 5, B # 4)
→ (B # 5, B # 6) → (B # 7, B # 6) → (B #
7, B # 8) formed when the mobile station is stationary 2
The set of two beams is as follows. At rest: (B # 5
B # 4) → (B # 5, B # 6) → (B # 5, B # 4) →
(B # 5, B # 6)

Note that, instead of the above-described configuration in which the beam is made to follow based on the level of the path detected by the two adjacent beams, the number of paths detected by the two adjacent beams is used instead. The beam may be made to follow. In this way, two adjacent beams in the direction of the mobile station are formed, the moving direction is estimated according to the path level or the number of detected paths detected by the beams, and the beam forming direction is switched to move the mobile station. At this time, it is possible to form a beam that follows the mobile station according to the movement and even when the mobile station is stationary, and it is possible to estimate the path arrival direction while performing highly accurate path detection.

In the above embodiment, two adjacent beams are formed, a delay profile for the two beams is generated to detect the path timing, and the beam to be formed next is determined. This method enables highly accurate path detection and beam tracking when the spread in the direction of arrival of a path is less than or equal to the width of two adjacent beams, but the width of two beams in the direction of arrival depends on the propagation environment. If the beam spreads over the above range or the levels of all the paths temporarily drop, the beam switching and path detection accuracy become unstable in the above embodiment.

In order to operate stably in such a situation, the beam width as shown in FIGS. 3A and 3B formed by using a part of the antenna elements of the array antenna 10. Also prepare weight values for wide beams. Then, as shown in (c) of the figure, when a narrow beam is formed and path detection is performed with high accuracy, when a path is not detected from the delay profile of any beam, A beam having a wider beam width as shown in (b) of the figure including the beam direction which has been performed until then is changed to the two beams B # 1 as in the above-described embodiment.
Path detection is performed by switching between 1 and B # 12.

When the path is not detected even by the wide beam shown in FIG. 9B, the wider beam B # 1 shown in FIG. 9A is formed to detect the path.
Then, when the paths are continuously detected only in one specific beam B # 1, the narrower beams B # 11, B covered by the specific beam width as shown in FIG.
# 12 is formed, path detection is performed, and the specific 1
When a path is continuously detected by two beams (for example, B # 11), a narrower beam (for example, B # 11) covered by the specific beam B # 11 is displayed as shown in (c) of the figure.
# 111, B # 112) to perform path detection,
Improves path detection accuracy. By doing so, a highly accurate and stable path search can be continuously performed.

[0040]

As described above, according to the present invention,
In the searcher, multiple beam forming is performed using an array antenna to generate a delay profile for each beam,
By performing path detection and path arrival direction estimation based on the plurality of delay profiles, high-accuracy path detection can be performed by only generating delay profiles by about two beam formations regardless of an increase in the number of antenna elements. The path arrival direction can be estimated, and the increase in circuit scale can be suppressed.

As described above, in the communication device of the CDMA mobile communication system to which the array antenna is applied, it is possible to suppress the increase of the transmission power due to the deterioration of the path search characteristic and the incompleteness of the formed beam. In the CDMA mobile communication system in which the system capacity is limited by the increase in the amount of interference from the communication device, the amount of interference is reduced by accurate beam forming by the array antenna,
It will be possible to bring about an increase in system capacity.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an array antenna baseband received signal processing unit according to the present invention.

FIG. 2 is an explanatory diagram of a method of estimating a path arrival direction by following a mobile station according to the present invention.

FIG. 3 is an explanatory diagram of a method of path detection by beam forming with different widths according to the present invention.

FIG. 4 is a diagram showing a configuration of a conventional array antenna baseband received signal processing section.

[Explanation of symbols]

10 array antenna 20 Adaptive array antenna reception demodulator 21 Finger assignment section 22 Despreading section 23 Weight converter 24 Wait update section 25 beam former 26 Synchronous detection section 30 Searcher 31 Beamformer 32 Correlation processing unit 33 Power converter 34 Averaging processor 35 Delay Profile 36-path arrival direction detector 37 Weight control unit 38 Weight setting section

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J021 AA05 AA06 CA06 DB01 EA07                       FA09 FA14 FA18 FA20 FA25                       FA29 FA30 FA32 GA02 GA08                       HA06 HA10 JA07                 5J070 AA02 AC11 AD06 AD09 AH04                 5K022 EE02 EE32                 5K059 CC03 CC04 DD31

Claims (5)

[Claims] 1. DS-CDMA using an array antenna
In a wireless communication device for mobile communication, a searcher that detects a path timing of a received signal, and a reception demodulation unit that demodulates a received signal of an array antenna for the detected path are provided, and the searcher is the array. Beam forming means for forming a plurality of beams for path search by the antenna, means for generating a path delay profile for each of the plurality of beams formed by the beam forming means, and based on the delay profile of the plurality of beams, The reception demodulation unit includes a path arrival detection unit for detecting a path timing for despreading processing and estimating an arrival direction of the path, and the reception demodulation unit detects a reception signal based on a path timing from a searcher. It is characterized by including means for despreading and means for demodulating a received signal by performing array antenna beamforming. Array antenna radio communication apparatus according to. 2. The searcher forms a beam smaller in number than the number of antenna elements of the array antenna, and determines a beam forming weight value for the next path search based on a delay profile of each beam generated from the beam. The array antenna wireless communication device according to claim 1, further comprising: 3. The searcher, as a beam forming weight value for path search, from among a plurality of beam forming weight values prepared in advance with slightly different beam directions,
The array antenna radio communication apparatus according to claim 2, further comprising means for determining a weight value for beamforming for the next path search. 4. The searcher forms two beams whose beam directions are adjacent to each other, and based on a delay profile of the two beams, a beam having a delay profile having a high path level or a large number of paths (hereinafter referred to as “first beam”). 1 beam ”) and a beam with a delay profile having a low path level or a small number of paths (hereinafter referred to as“ second beam ”).
, The weight value of the first beam is maintained as it is, and the weight value of the second beam is changed to the weight value of the beam direction adjacent to the opposite side across the first beam. 4. The array antenna wireless communication apparatus according to claim 3, further comprising means for determining a beam forming weight value for path search of the above. 5. The searcher uses a weight value (hereinafter, referred to as “first weight value”) for forming a plurality of beams having narrow beam widths and slightly different directions by using all antenna elements of an array antenna. At the same time, a weight value (hereinafter, referred to as a “second weight value”) for forming a beam having a wide beam width is stored in advance by using only some antenna elements of the array antenna, and the first weight value is stored. If a path is not detected from the delay profile during narrow beamforming by, the beam forming weight value for the next path search is changed to the wide beam forming weight value by the second weight value. , When a path is detected only from the delay profile of one beam when forming a wide beam with the second weight value, the next pass server A means for changing the beam forming weight value for the H channel to a narrow beam forming weight value by the plurality of first weight values covered by the beam of the second weight value is provided. The array antenna wireless communication device according to Item 2, 3 or 4.