JP4166606B2 - Mobile station, communication control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile station and a communication control method suitable for use in a code division multiple access (CDMA) wireless communication system.
[0002]
[Prior art]
Conventionally, a mobile station (portable terminal) has an adaptive array antenna system having a plurality of antenna elements, performs reception wave adaptation processing using MMSE (least square error method), etc., and forms a directivity pattern to form a radio base station. One that receives a radio signal from a station is known. The adaptive array antenna system forms a received beam pattern in the direction of arrival of the desired wave, and improves the communication quality by forming and suppressing nulls in the direction of arrival of interference waves from other base stations. It has been. In addition, there is a case in which calculation of a radio wave propagation path by reception wave adaptation processing is omitted by creating a database of directivity pattern data corresponding to the position of the mobile station in advance and forming the directivity pattern using the data ( For example, see Patent Documents 1 and 2). As a result, when the mobile station moves, the directivity of the antenna is quickly controlled with good followability.
[0003]
[Patent Document 1]
JP-A-8-139657 [Patent Document 2]
Japanese Patent Laid-Open No. 13-94496
[Problems to be solved by the invention]
However, since the above-described conventional technology uses directivity pattern data stored in advance in a database, there is a problem that it cannot cope with the surrounding environment of a mobile station that changes every moment. For example, if the mobile station is hidden behind a moving object that passes by or is behind the user due to the way the mobile terminal is a mobile station, the radio wave environment changes, so existing data may not be supported. There is.
[0005]
The present invention has been made in consideration of such circumstances, and its purpose is to change the surroundings of a mobile station that changes every moment when a directivity pattern is formed by an adaptive array antenna system to improve communication quality. It is an object of the present invention to provide a mobile station and a communication control method that can cope with the environment.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the mobile station according to claim 1 calculates a direction of the radio base station with respect to the array antenna in a mobile station that receives a radio signal by an array antenna having a plurality of antenna elements, Beam pattern forming means for forming a beam pattern in the direction of the base station, directivity pattern forming means for forming a directivity pattern corresponding to a received wave based on the received signal, the beam pattern in the direction of the base station, and the reception Reception processing means for combining the directivity pattern corresponding to the wave and performing reception processing of the reception signal.
[0007]
The mobile station according to claim 2, further comprising transmission processing means for performing transmission processing of a transmission signal based on a beam pattern in the direction of the base station and a directivity pattern corresponding to the received wave. .
[0008]
In the mobile station according to claim 3 , both of the currently communicating radio base station and a candidate radio base station to be handed off based on the beam pattern in the direction of the base station and the directivity pattern corresponding to the received wave It is characterized by communicating simultaneously.
[0009]
The communication control method according to claim 4 is a communication control method in a mobile station that receives a radio signal by an array antenna having a plurality of antenna elements, the step of calculating a direction of the radio base station with respect to the array antenna; A process of forming a beam pattern in the direction of the base station, a process of forming a directivity pattern corresponding to a received wave based on the received signal, a beam pattern in the direction of the base station and a directivity pattern corresponding to the received wave And a process of performing reception processing of the received signal.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a mobile terminal 100 according to an embodiment of the present invention. The portable terminal 100 is used as a mobile station (MS) in a code division multiple access (CDMA) wireless communication system.
In FIG. 1, a mobile terminal 100 includes an array antenna composed of a plurality of antenna elements ANT-1 to ANT-N, a radio transmission / reception unit 1, a plurality of reception wave adaptation processing units 2-1 to M, and a plurality of reception weighting units 3. −0 to M, Rake receiving unit 4, baseband processing unit 5, GPS (Global Positioning System) antenna GPSANT, position information processing unit 11, azimuth information processing unit 12, and base station direction adaptation processing A unit 13, a direction comparison unit 14, and a selector (SEL) 15.
[0011]
The wireless transmission / reception unit 1 performs transmission and reception using the antenna elements ANT-1 to ANT-N. In FIG. 1, other blocks related to the transmission function are omitted. After the signals A1 to AN of the antenna elements ANT-1 to N are received by the wireless transmission / reception unit 1, they are output to the reception wave adaptation processing units 2-1 to M and reception weighting units 3-0 to M as reception signals B1 to BN. Is done.
[0012]
The reception wave adaptive processing units 2-1 to M perform adaptive signal processing using, for example, MMSE on the input reception signals B1 to BN. By this adaptive signal processing, weighting factors W11 to W1N, W21 to W2N,... WM1 to WMN are calculated for each antenna element corresponding to each received wave, and reception weighting units 3-1 to 3-1 corresponding to each received wave, respectively. Output to M. Each weighting factor is for forming a directivity pattern corresponding to each received wave. Since the directivity pattern corresponding to the received wave changes from time to time due to the reflected wave or the like, the received wave adaptive processing units 2-1 to M determine the weighting coefficient so as to follow the change.
[0013]
The reception weighting units 3-1 to M add and multiply the input reception signals B1 to BN by corresponding weighting factors W11 to W1N, W21 to W2N, ..., WM1 to WMN, respectively, and output the result to the rake reception unit 4 . Thereby, the phase and amplitude of the reception signals B1 to BN are controlled, and a directivity pattern is formed.
[0014]
The rake receiving unit 4 performs rake reception using a plurality of received signals. By this rake reception, several desired waves having different propagation paths such as delayed waves are combined at the maximum ratio to improve the reception characteristics.
The baseband processing unit outputs a baseband signal for the received signal after rake reception. Further, the base station position information (latitude, longitude) received from the radio base station is output to the position information processing unit 11. The base station position information may be stored as data in advance.
[0015]
The position information processing unit 11 has a position measurement function such as GPS, and measures position information (latitude and longitude) of the mobile terminal 100 based on a received signal from the antenna GPSANT. Then, from the position information of the mobile terminal (MS) 100 and the base station position information, the positional relationship with the currently communicating radio base station (BS) 200 is grasped, and the reference direction (for example, true north) Is calculated (see FIG. 2). In the example of FIG. 2, the mobile terminal 100 includes four antenna elements ANT-1 to ANT-4, and the antenna element ANT-1 is used as a reference antenna.
[0016]
The azimuth information processing unit 12 has an azimuth measurement function such as an electronic compass, measures the azimuth that the portable terminal 100 is facing, and calculates angle information (θd) with respect to the reference direction (see FIG. 2). This angle information is obtained with reference to a predetermined reference antenna (antenna element ANT-1 in the example of FIG. 2) from a plurality of antenna elements.
[0017]
The base station direction adaptation processing unit 13 calculates angle information (θbs) in the base station direction based on the angle information (θp, θd) obtained by the position information processing unit 11 and the direction information processing unit 12 (FIG. 2). reference). Then, weighting factors W01 to W0N are calculated for each antenna element from the angle information (θbs), and output to the reception weighting unit 3-0. The reception weighting unit 3-0 multiplies the input reception signals B1 to BN by weighting factors W01 to W0N and outputs the result to the selector 15. Thereby, the phase and amplitude of the reception signals B1 to BN are controlled, and a beam pattern is formed. This beam pattern is always formed in the direction of the base station.
[0018]
The received wave adaptation processing units 2-1 to M and the base station direction adaptation processing 13 operate constantly. The base station direction adaptation processing unit 13 operates regardless of the reception characteristics of the desired wave. Then, the base station direction adaptation processing unit 13 forms a directivity pattern for performing auxiliary reception when the directivity pattern formed by the reception wave adaptation processing units 2-1 to M varies drastically. (See FIG. 4). Alternatively, an object is to form a directivity pattern for instantaneously receiving a desired wave when the mobile terminal 100 moves from a non-line-of-sight to a line-of-sight with respect to the radio base station 200 (see FIG. 3). .
[0019]
The direction comparison unit 14 is based on the base station direction angle information (θbs) input from the base station direction adaptation processing unit 13 and the weighting factors W11 to W1N input from the received wave adaptation processing unit 2-1. The relation between the base station direction and the arrival direction of the received wave is grasped, and when those directions are within a predetermined range, the selector 15 is closed and the reception signal from the reception weighting unit 3-0 is not output to the rake receiving unit 4. Like that.
[0020]
Next, an example of a method for calculating the weighting factors W01 to W0N for forming the beam pattern in the base station direction will be described.
First, the angle θp in the base station direction with respect to the reference direction around the mobile station is calculated from the position information (longitude, latitude) of each of the radio base station and the mobile station (portable terminal 100). Here, the angle θa is defined by the following equation.
θa = atan [(| longitude of mobile station−longitude of base station | × Dk)
÷ (| Latitude of mobile station-Latitude of base station | × Di)]
Where Di is the distance per second of latitude at the position of the mobile station, and Dk is the distance per second of longitude. These values Di and Dk may be the same value in a predetermined area range.
[0021]
Then, an angle θp with respect to a reference direction (in this example, with true north as a reference and eastward rotation as +) is obtained from the conditions shown in the following (a) to (h). Conditions (a) to (h) show an angle θp corresponding to the positional relationship between the mobile station and the base station.
(A) Mobile station longitude <base station longitude, mobile station latitude <base station latitude; θp = θa
(B) Mobile station longitude <base station longitude, mobile station latitude> base station latitude; θp = 180 degrees−θa
(C) Mobile station longitude> base station longitude, mobile station latitude> base station latitude; θp = 180 degrees + θa
(D) Mobile station longitude> base station longitude, mobile station latitude <base station latitude; θp = 360 degrees−θa
(E) Mobile station longitude = base station longitude, mobile station latitude <base station latitude; θp = 0 degrees (f) Mobile station longitude = base station longitude, mobile station latitude> base station latitude; θp = 180 degrees (g) Station longitude <base station longitude, mobile station latitude = base station latitude; θp = 90 degrees (h) mobile station longitude> base station longitude, mobile station latitude = base station latitude; θp = 270 degrees
Next, the base station direction angle θbs relative to the reference antenna is calculated from the base station direction angle θp relative to the reference direction and the mobile station azimuth angle θd using the following equation.
If θd <θp, θbs = θp-θd
When θd> θp, θbs = 360 degrees − (θd−θp)
When θd = θp, θbs = 0
[0023]
Next, weighting factors W01 to W0N are calculated from the angle θbs in the base station direction with respect to the reference antenna. An example of calculating the weighting factors W01 and W02 is shown below. In this example, the number of antenna elements N of the array antenna is 2, the distance between the antenna elements is λ / 2, the power of the desired wave is 1, and there is no interference wave.
W01 = 1
W02 = exp (−jπsinθbs)
Note that the above calculation method is an example, and the calculation formula varies depending on conditions such as the number of elements, element spacing, and arrangement.
[0024]
Next, the operation of the mobile terminal 100 shown in FIG. 1 will be described.
First, the basic operation will be described.
First, in a state where normal transmission / reception as a mobile station is performed, the received wave adaptation processing units 2-1 to M form a beam pattern in the arrival direction of the received wave based on the received reference signal of the desired wave. In addition, a weighting coefficient is calculated and output to the reception weighting units 3-1 to M so as to form a null in the interference wave direction. The phases and amplitudes of the reception signals B1 to BN are controlled by the reception weighting units 3-1 to M based on the weighting coefficients, and directivity patterns (reception wave directivity patterns) corresponding to the respective reception waves are formed.
[0025]
In addition, the position information processing unit 11 measures the position information (latitude and longitude) of the mobile station, and receives the position information (latitude and longitude) of the neighboring base stations received from the radio base station from the baseband processing unit 5. The position information of the radio base station that is currently communicating is obtained from the position information of the base station. Then, angle information (θp) in the base station direction with respect to the reference direction is calculated from the position information of the own mobile station and the position information of the base station in communication.
[0026]
Further, the azimuth information processing unit 12 measures azimuth information indicating the azimuth (own direction) in which the reference antenna element is facing. Then, angle information (θd) of its own direction with respect to the reference direction is calculated.
[0027]
The base station direction adaptation processing unit 13 receives angle information (θp, θd) from the position information processing unit 11 and the azimuth information processing unit 12, and calculates an angle θbs in the base station direction with respect to the reference antenna element. Next, a weighting coefficient is calculated based on the angle θbs and output to the reception weighting unit 3-0. Based on the weighting factors, the reception weighting units 3-1 to M control the phases and amplitudes of the reception signals B1 to BN to form a beam pattern (base station direction beam pattern) in the direction of the base station.
[0028]
The rake receiving unit 4 receives a desired wave by combining each formed reception wave directivity pattern and base station direction beam pattern, and performs rake reception.
[0029]
Next, a reception method in the rake reception unit will be described.
First receiving method;
Reception processing is performed by combining a desired wave obtained from one received wave directivity pattern and a desired wave obtained from a base station direction beam pattern. This method is applied when the surrounding environment of the mobile terminal 100 is in the situation shown in FIG. 3 or FIG. 4, for example.
[0030]
Second receiving method;
A plurality of desired waves obtained by one received wave directivity pattern and a desired wave obtained by the base station direction directivity pattern are combined to perform reception processing. This method is applied when the surrounding environment of the mobile terminal 100 is in the situation shown in FIG. 5, for example.
[0031]
A third receiving method;
A plurality of desired waves obtained from a plurality of received wave directivity patterns and a desired wave obtained from a base station direction beam pattern are combined to perform reception processing. This method is applied when the surrounding environment of the mobile terminal 100 is in the situation shown in FIG. 6, for example.
[0032]
4th receiving method;
When the direction of the maximum receiving sensitivity point of the desired wave obtained by one received wave directivity pattern is the same as the direction of the base station direction beam pattern, or the difference between these directions is within a predetermined range, A desired wave obtained by the received wave directivity pattern is selected. Here, when there are a plurality of desired waves obtained by the received wave directivity pattern, they are combined and subjected to reception processing.
[0033]
Fifth reception method;
When the direction of the maximum reception sensitivity point in a plurality of desired waves obtained by a plurality of reception wave directivity patterns is the same as the direction of the base station direction beam pattern, or the difference between these directions is within a predetermined range The desired wave at the maximum reception sensitivity point is selected.
[0034]
Note that receiving characteristics by rake reception are further improved by capturing more desired waves with different propagation paths, so that one desired wave in the same direction of arrival is received, and more desired waves of different propagation paths are received. Is preferred. The fourth and fifth methods are based on this finding.
The first to fifth receiving methods can be appropriately selected and used.
[0035]
In the above-described embodiment, the reception process is described as an example, but the present invention can be similarly applied to the transmission process. At the time of transmission, correction corresponding to the transmission frequency is performed based on the weighting factor of each directivity pattern obtained at the time of reception. Then, the phase and amplitude are controlled by the corrected weighting factor to form a directivity pattern for transmission. The transmission method will be described below.
First transmission method;
Transmission is performed in two directions: a beam pattern of one reception wave directivity pattern and a beam pattern of a base station direction.
[0036]
Second transmission method;
Among the plurality of desired waves obtained by the plurality of received wave directivity patterns, the received wave directivity pattern of the desired wave having the maximum received power is selected. Then, transmission is performed in the two directions of the beam pattern of the selected received wave directivity pattern and the beam pattern of the base station direction.
[0037]
Third transmission method;
When the direction of the maximum reception sensitivity point of one received wave directivity pattern is the same as the direction of the base station direction beam pattern or the difference between these directions is within a predetermined range, the received wave directivity pattern Transmission is performed in one direction of the beam pattern or the base station direction beam pattern.
[0038]
Fourth transmission method;
Among the plurality of desired waves obtained by the plurality of received wave directivity patterns, the received wave directivity pattern of the desired wave having the maximum received power is selected. When the beam pattern direction of the selected reception wave directivity pattern is the same as the direction of the base station direction beam pattern, the beam pattern of the reception wave directivity pattern is selected and transmitted.
[0039]
Fifth transmission method;
Transmission by directivity pattern is not performed, but transmission is performed by omni.
[0040]
The first to fifth transmission methods can be appropriately selected and used.
[0041]
When the mobile station performs handoff, each combination of the receiving method and the transmitting method to each base station (current base station) that is currently communicating with the candidate base station (next candidate base station) to be handed off. Select a directivity pattern. As a result, simultaneous communication between the current base station and the next candidate base station in two directions becomes possible.
[0042]
In the embodiment of FIG. 1 described above, the base station direction adaptive processing unit 13 and the reception weighting unit 3-0 correspond to a base station direction beam pattern forming unit. The reception wave adaptive processing units 2-1 to M and the reception weighting units 3-1 to M correspond to reception wave directivity pattern forming means. The rake receiving unit 4 corresponds to a reception processing unit. The baseband processing unit 5 corresponds to a base station position information acquisition unit.
[0043]
Further, the position and orientation information of the mobile station may be measured by an external device connected externally in the vicinity of the mobile station, and the mobile station may acquire the information from the external device.
[0044]
Note that the mobile station (portable terminal) of the present embodiment includes, for example, a portable terminal called a mobile phone or PDA (Personal Digital Assistants). Here, in the case of a PDA, it is assumed that wireless communication means is incorporated. In addition, the mobile station of the present invention is not limited to a portable type, and various mobile phones equipped with a car navigation system having position and orientation information acquisition means such as a GPS function and an electronic compass function, or mounted on a moving object. Wireless devices are included as well.
[0045]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
[0046]
【The invention's effect】
As described above, according to the present invention, radio signals are received or transmitted using a beam pattern in the direction of a base station or a directivity pattern corresponding to a received wave, so that it can cope with the surrounding environment of a mobile station that changes every moment. can do. Thereby, the outstanding effect that communication quality can be improved stably can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a mobile terminal 100 according to an embodiment of the present invention.
FIG. 2 is a first diagram illustrating a communication control method according to an embodiment of the present invention.
FIG. 3 is a second diagram illustrating a communication control method according to an embodiment of the present invention.
FIG. 4 is a third diagram illustrating a communication control method according to an embodiment of the present invention.
FIG. 5 is a fourth diagram for explaining a communication control method according to an embodiment of the present invention;
FIG. 6 is a fifth diagram for explaining a communication control method according to an embodiment of the present invention;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Radio | wireless transmission / reception part, 2-1-M ... Received wave adaptive processing part, 3-0-M ... Reception weighting part, 4 ... Rake receiving part, 5 ... Baseband processing part, 11 ... Position information processing part, 12 ... Direction information processing unit, 13 ... base station direction adaptation processing unit, 14 ... direction comparison unit, 15 ... selector (SEL), 100 ... mobile terminal (mobile station), 200 ... radio base station, ANT-1 to N ... antenna elements , GPSANT ... GPS antenna

Claims (4)

In a mobile station that receives a radio signal by an array antenna having a plurality of antenna elements,
A beam pattern forming means for calculating a direction of the radio base station relative to the array antenna and forming a beam pattern in the direction of the base station;
Directivity pattern forming means for forming a directivity pattern corresponding to a received wave based on the received signal;
A reception processing means for performing reception processing of the received signal by combining a beam pattern in the direction of the base station and a directivity pattern corresponding to the received wave;
A mobile station characterized by comprising:   The mobile station according to claim 1, further comprising transmission processing means for performing transmission processing of a transmission signal based on a beam pattern in the base station direction and a directivity pattern corresponding to the received wave.   The communication is performed simultaneously with both a radio base station that is currently communicating and a candidate radio base station to be handed off based on a beam pattern in the base station direction and a directivity pattern corresponding to the received wave. The mobile station according to claim 1 or 2. A communication control method in a mobile station that receives a radio signal by an array antenna having a plurality of antenna elements,
Calculating the direction of the radio base station relative to the array antenna;
Forming a beam pattern in the direction of the base station;
Forming a directivity pattern corresponding to a received wave based on the received signal;
A process of performing reception processing of the received signal by combining a beam pattern in the direction of the base station and a directivity pattern corresponding to the received wave;
The communication control method characterized by including.

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