JP2002262328A - Mobile communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication terminal provided with an adaptive array antenna that can realize high-speed handover. SOLUTION: The mobile communication terminal is provided with a plurality of multipliers that multiply a plurality of signals outputted from the array antenna by corresponding weighting coefficients to provide an output of a multiplication result signal, a reception means that generates a received signal from the multiplication result signal outputted form the multipliers, a control means that executes the calculation of the weighting coefficient based on the received signal outputted from the reception means to conduct adaptive control by giving the weighting coefficient to the multipliers, an initial value calculation means that calculates the initial value of the weighting coefficient before the handover. The control means starts the calculation of the weight coefficient by using the initial value calculated at the handover.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile terminal for performing wireless communication with a base station, and more particularly to a mobile communication terminal using an adaptive array antenna.

[0002]

2. Description of the Related Art An adaptive array antenna performs weighting by multiplying the output of each antenna element of an array antenna composed of a plurality of antenna elements arranged in a predetermined shape by a weight coefficient, and controls the weight coefficient. This makes it possible to adaptively change the directivity of the antenna. In recent years, research and development of a wireless communication system in which the adaptive array antenna is mounted on a mobile terminal have been promoted.

FIG. 16 shows a typical example of a radio communication system using such a mobile radio terminal. Mobile terminal 10
00 is the mounted adaptive array antenna 101
By adaptively controlling the weighting factor of 0, the beam pattern 1 with directivity directed to the base station 1001 of the communication partner
011 to communicate with the base station 1001. As a result, compared to the case where an omni directional antenna is mounted,
Transmission power can be suppressed to reduce power consumption. When a power supply with a limited capacity such as a battery is used, communication for a longer time can be performed. Further, since it is possible to suppress the radiation of interference power in other directions, it is possible to suppress interference with base stations other than the base station 1001 that is performing communication.

In such a wireless communication system,
The mobile terminal 1000 moves to the base station 1001 of the communication partner.
, The handover is performed when the reception electric field strength necessary for continuing communication cannot be obtained. At the time of handover, it is necessary to newly combine a beam pattern 1012 with the antenna directivity directed to the base station 1002 that has moved closer to the mobile terminal 1000 due to the movement.
However, re-synthesizing the beam pattern of the adaptive array antenna requires a signal processing time for adaptive control of the weighting factor, and a signal processing time required for the adaptive control accompanying the change from the beam pattern 1011 to the beam pattern 1012. During that time, the communication will be interrupted.

As described above, in a conventional mobile radio terminal for radio communication equipped with an adaptive array antenna capable of adaptively changing the directivity, a signal for adaptive control of a weight coefficient is used for directivity synthesis of the adaptive array antenna. Since processing time is required, there is a problem that communication is interrupted during a signal processing time required for adaptive control accompanying a change in a beam pattern at the time of handover.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and to provide a mobile communication terminal device having an adaptive array antenna capable of realizing a high-speed handover.

[0007]

To solve the above problems, a mobile communication terminal according to the present invention is configured as follows. That is, the mobile communication terminal device according to the present invention communicates with one of the first base station and the second base station,
A mobile communication terminal device that performs handover from said first base station to said second base station, comprising: multiplying a plurality of signals output from said array antenna by a weighting coefficient; A plurality of multipliers that output a multiplication result signal; a receiving unit that generates a reception signal from the multiplication result signal output from the multiplier; and a weighting coefficient based on the reception signal output from the reception unit. Control means for performing calculation and adaptively controlling the multiplier by giving the calculated weighting coefficient, and initial value calculating means for calculating an initial value of the weighting coefficient before the handover, The control means starts calculation of the weighting coefficient using the initial value at the time of the handover.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a diagram for explaining an outline of a wireless communication system according to a first embodiment of the present invention, in which a mobile phone provided with an adaptive array antenna,
A mobile terminal device (hereinafter, simply referred to as a mobile terminal) 100 such as a portable wireless device or a portable information terminal and a base station 101 are TD
It shows a state in which communication is performed by a MA (Time Division Multiple Access) communication method.

[0009] In the TDMA communication system, as shown in the upper part of FIG.
M frames), and each TDM frame is further divided into a plurality of time slots S1, S2, S3. When the mobile terminal 100 performs communication, one time slot is usually assigned to one frame.

[0010] In the example of FIG.
The time slot allocated for communication to 00 is S
1, the mobile terminal 100 uses the antenna beam 111 synthesized by the array antenna 110 in the time slot S1 in each TDM frame to use the base station 101.
Is receiving a transmission signal from In other time slots S2 and S3, a transmission signal for mobile terminal 100 is not output from base station 101.

The mobile terminal 100 uses, for example, the time slot of time slots S2 and S3 other than the time slot S1 used for reception and the time required for switching an antenna beam, for example, the head of time slot S2 and the time slot S2. In the time zone excluding the vicinity of the end of S3, the direction of arrival of radio waves arriving from the surrounding base stations 102 other than the base station 101 currently communicating is estimated. If the mobile terminal 100 is not moving at high speed, the time slots S2 and S
It is not necessary to estimate the direction of arrival in all the time zones of 3, but at least in consideration of the moving speed of the mobile terminal 100,
The arrival direction estimation is performed at time intervals such that the arrival direction estimation result does not fluctuate extremely. A specific example of the arrival direction estimation will be described later in detail.

The mobile terminal 100 calculates a weighting factor for directing the antenna beam in the estimated direction of arrival,
Alternatively, a weighting factor is calculated so that a null can be directed toward the base station 101 which is currently communicating using the time slot S1, and is stored in the memory together with the arrival direction estimation result and information on the reception level, for example. Keep it. Then, at the time of handover from the base station 101 to the base station 102, adaptive control of the adaptive array antenna is started with the arrival direction estimation result and the weighting factor calculated up to that time and stored in the memory as initial values.

By such an operation, the mobile terminal 100 may move away from the base station 101 with which communication is currently being performed, or an obstacle such as a building may enter between the base station 101 and suddenly lose visibility. Thus, the convergence of the adaptive control of the adaptive array antenna can be accelerated, and the problem of the related art can be solved. Hereinafter, a more specific description will be given.

FIG. 2 shows a mobile terminal 10 according to the present embodiment.
0 shows an example of the configuration of a transceiver used for the transmission / reception apparatus. The array antenna 110 is shown in FIG. 1, and is configured by arranging a plurality of antenna elements A1, A2, A3, and A4 in a predetermined shape such as a linear shape or a circular shape. An output signal of each antenna element of the array antenna 110 is filtered by a filter (for example, a band-pass filter) 201 to remove unnecessary components, further amplified by a low noise amplifier (LNA) 202, input to a mixer 203, and output from a local oscillator 204. The frequency is converted (down-converted) by being multiplied by the local signal supplied via the distributor 205. The output of the multiplier 203 is the filter 20
Unnecessary components are removed by 6 and demodulated by a quadrature demodulator 207, and then converted into a digital signal by an A / D converter (ADC) 208. Filter 201, LNA20
2, mixer 203, local oscillator 204, distributor 20
5, the number of filters 206, the number of quadrature demodulators 207, and the number of A / D converters 208 are equal to the number of antenna elements of the array antenna 110.

The digital signal output from the A / D converter 208 is input to a digital signal processor (DSP) 210. In the digital signal processing unit 210, A
The digital signal from the / D converter 208 is first input to a multiplier (complex multiplier) 211 and multiplied by a weight coefficient (complex weight coefficient) for amplitude and phase. Multiplier 2
The outputs of 11 are added by the adder 212. Adder 2
The output of the detection circuit 12 is detected by a detection circuit 213, and the output of the detection circuit 213 is guided to a next-stage circuit (not shown) as a reception signal and is input to the control circuit 214. A digital signal from the A / D converter 208 is also input to the control circuit 214. The weight coefficient is given to the multiplier 211 by the control circuit 214. Control circuit 2
14 will be described in detail later.

The digital signal processing section 210 includes, in addition to the main synchronization circuit 215 used for transmission / reception to / from the base station 101 with which the mobile terminal 100 is currently communicating, at least one other terminal other than the base station 101. A sub-synchronization circuit 216 used when transmitting and receiving to and from a base station (for example, the base station 102 in FIG. 1) is provided. These synchronization circuits 215 and 216 are circuits that perform bit synchronization and frame synchronization, and are configured using, for example, a PLL (Phase Locked Loop). The synchronization circuits 215 and 216 are switched by switches 217 and 218.

That is, the mobile terminal 100 is connected to the base station 101
When communication is performed between the switch 217 and the switch 217, the switches 217 and 218 are connected to the solid line side, and the output of the adder 212 is
17, the signal is input to the main synchronization circuit 215, and the output of the main synchronization circuit 215 is input to the detection circuit 213 and the control circuit 214 via the switch 218. Similarly, when the mobile terminal 100 communicates with the base station 102, the switches 217 and 218 are connected to the side of the broken line, and the output of the adder 212 is sent to the sub-synchronous circuit 216 via the switch 217. At the same time, the output of the sub-synchronous circuit 216 is input to the detection circuit 213 and the control circuit 214 via the switch 218. The signal supplied from the synchronization circuits 215 and 216 to the detection circuit 213 is a reference signal for synchronous detection, and a clock signal synchronized with the reference signal is input to the control circuit 214.

As described above, in the mobile terminal 100, apart from the main synchronization circuit 215 used for receiving a transmission signal from the communicating base station 101, the sub synchronization circuit 216 used for receiving a transmission signal from another base station 102 is used. , It is possible to obtain excellent error rate characteristics by synchronous detection even in intermittent transmission and reception with the base station 102. Further, it is expected that the control circuit 214 can easily apply a necessary direction estimation algorithm to the signal detected by the detection circuit 213.

Further, in the mobile terminal 100, since the signal reception from the base station 102 other than the base station 101 which is currently communicating is in a burst form, that is, intermittent, the time constant of the PLL used for the sub-synchronization circuit 216 is received. The time constant is changed between time and non-reception, and the time constant is increased so that the parameter does not move so much during non-reception, so that the phase is hardly fluctuated. This provides an effect that synchronous detection from the receiver becomes possible.

Next, the control circuit 214 will be described with reference to FIG. FIG. 3 shows a configuration of a portion related to weight coefficient control in the control circuit 214. In addition to a main weight coefficient calculation section 301 and a weight coefficient holding section 302, an arrival direction estimation section 303, a weight coefficient calculation section 304, and a weight coefficient It has a storage unit 305. The weighting factor calculation unit 301 calculates
An optimum weight coefficient is calculated based on the digital signal output from the / D converter 208 and the received signal from the detection circuit 213. The calculation of the weight coefficient is performed according to a criterion that minimizes an error signal between the received signal and the reference signal, for example. The weight coefficient calculated by the weight coefficient calculation unit 301 is provided to the multiplier 211 via the weight coefficient holding unit 302 for holding the weight coefficient until the next frame.

The arrival direction estimation unit 303
Is for estimating the direction of arrival of radio waves from base stations 102 and the like other than the base station 101 with which communication is being performed (hereinafter, referred to as the base station 102). The estimation method is as follows. Can be considered. (1) A “beam scan” of scanning around the mobile terminal 100 by deflecting the directionality of the maximum directivity of the adaptive array antenna is performed, and the direction in which the received electric field intensity becomes the largest is defined as the arrival direction of the radio wave. Specifically, while performing beam scanning by sequentially changing the weight coefficient, the level of the received signal from the detection circuit 213 is monitored, and the direction corresponding to the weight coefficient at the time when the received signal level is maximized is changed to the arrival direction. And

(2) The mobile terminal 100 changes the direction of the null, which is the trough of the radiation directivity of the adaptive array antenna.
"Null scan" is performed to scan the periphery of the radio wave, and the direction in which the received electric field intensity is the smallest is defined as the arrival direction of the radio wave. In order to realize this method, the level of the reception signal from the detection circuit 213 is monitored while performing null scanning by sequentially changing the weight coefficient, and the direction corresponding to the weight coefficient when the reception signal level becomes minimum is obtained. Should be the direction of arrival. (3) MUSIC (Multiple Signal Classification), known as a high-resolution DOA estimation algorithm, ES
PRIT (Estimation of Signal Parametersvia Rotat
methods based on eigenvalue expansion, such as ional Invariance Techniques, or the root MU
A method such as SIC or unitary ESPRIT is used. Although these methods increase the amount of signal processing for estimation,
The estimation accuracy is high.

The direction-of-arrival estimating section 303
If the estimation of the direction of arrival of the radio wave from 2 is successful, another weighting factor calculation unit 304 calculates a weighting factor for directing the antenna beam in the direction of arrival. The weighting factor thus calculated is stored in the weighting factor storage unit 305 in FIG.
In the form of a table as shown in FIG. That is, since there may be a plurality of surrounding base stations 102 other than the base station 101 which is currently communicating, the weight coefficient corresponding to the direction of arrival of the radio wave from each base station is determined by the arrival direction and the reception level. They are stored in association with each other. The reception level indicates the level of the reception signal output from the detection circuit 213. In addition,
In the table of FIG. 4, the direction of arrival corresponds to the weighting coefficient on a one-to-one basis, so that information on the direction of arrival may be omitted.

From the weight coefficient storage unit 305, the mobile terminal 1
When 00 needs to perform handover, the weight coefficient corresponding to the highest reception level is read. The weighting factor calculation unit 301 receives the weighting factor read from the weighting factor storage unit 305 as an initial value, and calculates (updates) the weighting factor from the initial value, that is, the optimal weighting factor for communication with the base station 102. Start adaptive control.

Next, the flow of processing in this embodiment will be described with reference to the flowchart shown in FIG. First, a time slot Sn (for example, Sn = S1) used for communication with the mobile terminal 100 from the base station 101 is allocated (S501). Next, the time slot Si is set to Sn, and when the time slot Sn starts, the mobile terminal 100 directs an antenna beam to the base station 101, receives a transmission signal from the base station 101 using the time slot Sn,
This reception is performed until the time slot Sn ends (S
502-S504). At the time when the time slot Sn ends, it is checked whether or not to continue the communication (S505). If the communication does not continue, a termination process is performed (S506). If the communication continues, the communication continues for a predetermined time or more from the previous arrival direction estimation. It is checked whether or not the time has elapsed (S50).
7).

In step S507, if the predetermined time has not elapsed after the end of the time slot Sn, the process returns to step S502. If the time has elapsed, the arrival direction estimating unit 303 causes the base station 101 currently communicating with the mobile terminal 100 to return to step S502. The direction of arrival of radio waves from other base stations 102 is estimated (S508). Then, a weighting factor is calculated by the weighting factor calculation unit 304 based on the estimated direction of arrival (S
509), the estimated arrival direction and reception level are associated with the calculated weighting factor and stored in the weighting factor storage unit 305 (S510).

Next, in step S 511, it is necessary to perform a handover while the mobile terminal 100 is communicating with the base station 101, that is, shift from a state where the mobile terminal 100 is communicating with the base station 101 to a communication with another base station 102. If this occurs, the weighting factor stored in the weighting factor storage unit 305 and corresponding to the direction of arrival of the radio wave from the base station 102 is given to the weighting factor calculation unit 301 as an initial value, and the radio wave from the base station 102 is transmitted. The adaptive control of the weight coefficient for reception is started (S512).

Here, the base stations 10 around the base station 101
In the case where there are a plurality of base stations 2, the weight coefficient storage unit 305 stores the weight coefficients corresponding to the directions of arrival of the radio waves from the base stations 102 together with the directions of arrival and the reception levels. Weighting factor corresponding to the base station having the highest reception level among the base stations is given as an initial value to the weighting factor calculation section 301, so that the weighting factor for receiving the radio wave from the base station having the highest reception level is obtained. Will be started.

Next, in step S513, the base station 1
If the handover from 01 to the base station 102 is not successful, termination processing is performed (S514). If the handover is successful, the base station 102 allocates a time slot Sm (S514).
515), the process after step S502 is repeated with Si as Sm.

As described above, in the present embodiment, the mobile terminal 10
During the handover for switching the base station 101 that communicates with the base station 101 to another base station 102, the weight coefficient storage unit 305 sends the weight coefficient calculated in advance to the weight coefficient calculation unit 301 according to the arrival direction of the radio wave from the base station 102. By giving it as an initial value, the adaptive control of the weight coefficient can be quickly converged.

Here, a modified example of this embodiment will be described.

FIG. 6 shows an example of a detailed internal configuration of the weighting factor calculator 304 in FIG.

In this configuration example, the weight coefficient initial value calculation unit 1401 from the estimated direction of arrival has the same function as the weight coefficient calculation unit 304 described above. This calculation unit 1401
Based on the direction-of-arrival estimation result from the direction-of-arrival estimation unit 303,
A weighting value capable of directing the maximum directivity to the estimated direction of arrival is calculated and output as an initial value. Weight coefficient updating section 1402 uses this initial value to receive a received signal from a corresponding base station other than the communicating base station.
Used as the initial value of the weight coefficient of the array antenna. Weight coefficient updating section 1402 also receives an ADC output from an input from each antenna element. The updating unit 1402 updates the weight coefficient by applying an adaptive control algorithm such as LMS (Least Mean Square) to the initial value. In the case of such a configuration, the output as it is from the calculation unit 1401 is used as the main weight calculation circuit 301 at the time of handover.
There is an advantage that the convergence time can be shortened as compared with the case where is given as an initial value.

In such a configuration example, with respect to the table shown in FIG. 4, the arrival direction and the weight coefficient do not always correspond one-to-one.

In another configuration example, as shown in FIG. 6, an initial value output control circuit 1403 according to the reception level is provided. Based on the information on the reception level output from the detection circuit 213, only when the reception level is higher than a predetermined threshold value, it is determined that the error of the estimated arrival direction estimation result is small, Value calculator 140
1 to output an initial value.

Next, another configuration example of the control circuit shown in FIG. 3 will be described.

FIG. 7 shows a case in which only the estimation of the direction of arrival for another base station is performed, and the estimated arrival direction and the reception level at that time are stored as a table of the base station. According to this configuration, there is an advantage that the size of the base station table can be reduced. Further, since the configuration is not such that the initial value of each weighting coefficient is calculated each time, it is possible to abundantly allocate hardware and software resources to the arrival direction estimation processing itself. This configuration is suitable for performing a high-resolution arrival direction estimation that requires a considerable processing time, instead of a direction estimation such as a beam scan, which usually does not require much processing time but the accuracy of the direction of arrival is slightly reduced. Yes, the direction estimation accuracy can be improved.

FIG. 8 shows a case where the arrival direction estimating unit is not provided and a second weighting coefficient calculating circuit is provided. This configuration is used when receiving at a timing other than the communication slot with the communicating base station, and when it is possible to calculate the weighting coefficients for other base stations with a certain degree of accuracy without estimating the direction of arrival. Are suitable.

For example, if there are few base stations transmitting at timings other than the communication slot with the communicating base station because the base stations are not set so densely, the interference is not severe, or And second-order modulation (or first-order modulation) is performed on a signal such as another type of spreading code, and after despreading of the second-order modulation, the signal from the base station is less likely to be interfered. It is.

In the configuration of FIG. 3, since the initial value of the weight for each antenna element is already calculated at the time of handover, the amount of calculation at the time of handover is smaller than that of the configuration shown in FIG. The advantage is less. The configuration of FIG. 3 (and FIG. 6) including the arrival direction estimating unit can use the estimation result of the arrival direction as the initial value of the weighting calculation circuit.
This is advantageous in that the convergence speed of the iterative calculation of the antenna weighting coefficient is improved as compared with.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 9 is a diagram schematically illustrating a wireless communication system according to the second embodiment.
In the same manner as described above, a mobile terminal device (hereinafter simply referred to as a mobile terminal) 600 such as a mobile phone, a mobile wireless device, and a personal digital assistant equipped with an adaptive array antenna and a base station 601 are CDMA (Code Division Multiple Access). This shows a state in which communication is performed by a communication method.

In the CDMA communication system, as shown in the upper part of FIG.
2, multiplexed by C3. The mobile terminal 600 has a receiving circuit including, for example, two sets of beam combining and despreading circuits, and each receiving circuit individually transmits the antenna beam 61.
1,612 can be formed. In the example of FIG. 9, the mobile terminal 600 is the base station 60 using the spreading code C1.
1 is received by an antenna beam 611 formed by one receiving circuit.

Further, the mobile terminal 600 deflects the antenna beam 612 formed by the other receiving circuit, scans the surroundings, or performs signal processing on the input signal vector to the adaptive array antenna. To estimate the direction of arrival of radio waves using the spreading code C2 arriving from the surrounding base station 602 other than the base station 601 that is currently communicating. In this case, the mobile terminal 600
The arrival direction estimation is performed at time intervals such that the arrival direction estimation result does not fluctuate extremely in consideration of the moving speed of the vehicle.

Thereafter, the mobile terminal 600 calculates a weighting factor for directing the antenna beam in the estimated arrival direction according to the arrival direction estimation result as in the first embodiment.
Alternatively, a weighting factor is calculated so that null can be directed toward the base station 601 with which communication is currently being performed,
It is stored in a memory together with the arrival direction estimation result. Then, at the time of handover from the base station 601 to the base station 602, adaptive control of the adaptive array antenna is started with the arrival direction estimation result and the weighting factor calculated and stored up to that time as initial values.

By doing so, the mobile terminal 60
0 speeds up the convergence of adaptive control of the adaptive array antenna even when the line of sight is suddenly lost due to being away from the base station 601 with which communication is currently being performed, or an obstacle such as a building entering between the base station 601 and the like. It becomes possible.

FIG. 10 shows a mobile terminal 6 according to this embodiment.
1 shows an example of the configuration of a transceiver used in 00.
Array antenna 610, filter 701, LNA 70
2, the mixer 703, the local oscillator 704 to the distributor 7
05, a filter 706, a quadrature demodulator 707, and an A / D converter (ADC) 708 are the same as the configuration of the mobile terminal 100 shown in FIG. 2 in the first embodiment.

Digital signal processing unit (DSP) to which a digital signal output from A / D converter 708 is input
The 709 is provided with two sets of receiving circuits 710 and 720. One receiving circuit 710 is used when the mobile terminal 600 receives a transmission signal from the base station 601 with which communication is currently performed, and the other reception circuit is used when the mobile terminal 600 receives a transmission signal from the other base station 602. A circuit 720 is used.

That is, a plurality of digital signals respectively input to the receiving circuits 710 and 720 in the digital signal processing unit 709 are respectively input to a plurality of first multipliers 711 and a second multiplier 721 which are complex multipliers. , Amplitude and phase are multiplied by a weighting factor (complex weighting factor). The outputs of multipliers 711 and 712 are added by adders 712 and 722, respectively. Adder 712
And 722 are output from despreading circuits 713 and 72, respectively.
3, after being despread using a spreading code,
13 and 723. Outputs of the detection circuits 714 and 724 are guided as reception signals to a next-stage circuit (not shown), and are also input to the control circuits 715 and 725, where the multipliers 711 and 7 are output from the control circuits 715 and 725.
21 is given a weighting factor. Control circuits 715 and 72
5 is the same as the control circuit 214 shown in FIG. 2 in the first embodiment.

The receiving circuits 710 and 720 are further provided with synchronization circuits 716 and 726. Synchronous circuit 71
6, 726, the mobile terminal 600 is the base station 601, 602
, And in other words, when the receiving circuits 710 and 720 receive transmission signals from the base stations 601 and 602, respectively, they perform bit synchronization and frame synchronization, and are configured using, for example, a PLL. .
Synchronizing circuits 716 and 726 are despreading circuits 713 and 723
Supplies a spread code (for example, C1 and C2), supplies reference signals for synchronous detection to the detection circuits 714 and 724, and supplies a clock signal to the control circuits 715 and 725. .

As described above, the two receiving circuits 710 and 720 in the mobile terminal 600 are provided with the synchronization circuits 716 and 72, respectively.
Provision of 6 makes it possible to obtain excellent error rate characteristics by synchronous detection even in intermittent transmission and reception with the base station 702. In addition, an effect that it is easy to apply the direction estimation algorithm required by the control circuits 715 and 725 to the signals detected by the detection circuits 714 and 724 can be expected.

Further, the reception of signals from the base station 602 other than the base station 601 currently communicating with the mobile terminal 600 is bursty, that is, intermittent, so that the time constant of the PLL used for the synchronization circuit 726 is different from that at the time of reception. By changing the time constant during reception and increasing the time constant so that the parameter does not move too much during non-reception, and devising a phase that is less likely to fluctuate, the synchronization state is preserved even during non-reception, and synchronization from different base stations is maintained. The effect that detection becomes possible is obtained.

Next, the flow of processing in this embodiment will be described with reference to the flowchart shown in FIG. First, a spreading code Cn (for example, Cn = C1) to be used for communication with the base station 601 that initially communicates with the mobile terminal 600 is determined (S801). Next, the spreading code Ci is set to Cn, the mobile terminal 600 directs an antenna beam to the base station 601, and receives a transmission signal from the base station 601 using the spreading code Cn (S802). In step S803, it is determined whether or not to continue the communication. If the communication is not to be continued, a termination process is performed (S804). If the communication is to be continued, it is further determined whether or not a predetermined time or more has passed since the previous arrival direction estimation. A check is made (S805).

If it is determined in step S805 that the predetermined time has not elapsed since the previous arrival direction estimation, step S8 is performed.
02, if the time has elapsed, the arrival direction estimating unit in the control circuit 725 estimates the arrival direction of radio waves from the base stations 102 other than the base station 101 currently communicating with the mobile terminal 600 (S806). Then, a weighting factor is calculated by the weighting factor calculation unit in the control circuit 725 based on the estimated arrival direction (S807), and the estimated arrival direction and reception level are associated with the calculated weighting factor in the control circuit 725. It is stored in the weight coefficient storage unit (S808).

Next, in step S 809, it is necessary to perform a handover while the mobile terminal 600 is communicating with the base station 601, that is, shift from the state where the mobile terminal 600 is communicating with the base station 601 to the communication with another base station 602. If this occurs, the weighting factor stored in the weighting factor storage unit in the control circuit 725 and corresponding to the direction of arrival of the radio wave from the base station 602 is given to the weighting factor calculation unit in the control circuit 725 as an initial value. Then, adaptive control of a weight coefficient for receiving a radio wave from the base station 602 is started (S810).

Here, the base stations 60 around the base station 601
If there are a plurality of 2's, since the weighting factors corresponding to the directions of arrival of the radio waves from the plurality of base stations 602 are stored in the weighting factor storage unit in the control circuit 725 together with the direction of arrival and the reception level, step S810 Then, by giving a weight coefficient corresponding to the base station having the highest reception level among the plurality of base stations to the weight coefficient calculation section in the control circuit 725 as an initial value, the weight coefficient from the base station having the highest reception level can be obtained. The adaptive control of the weight coefficient for receiving the radio wave is started.

Next, in step S811, the base station 6
If handover from 01 to the base station 602 is not successful, termination processing is performed (S812). If successful, the base station 602 and the spreading code Cm are determined (S813).
The process from step S802 is repeated with Ci set to Cm.

As described above, also in the present embodiment, at the time of handover in which the base station communicating with the mobile terminal 600 is switched from the base station 601 to another base station 602, the base station 60
By giving a weighting coefficient calculated in advance according to the arrival direction of the radio wave from 2 to the adaptive array antenna as an initial value, the adaptive control of the weighting coefficient can be quickly converged.

Further, in the present embodiment, the following handover process based on a base station list indicating the priority of link allocation may be used together. As shown in FIG. 12, the base station 6 currently communicating with the mobile terminal 600 in the mobile terminal 600
The identification information (base station ID) of the base station 602 (base station whose arrival direction is to be estimated) other than 01 is a spreading code multiplexed on a signal of a specific channel such as a pilot channel transmitted by the base station 602. (S90)
1) In the mobile terminal 600, reception strength information of a radio wave transmitted from the base station 602, for example, PSMM (Pilot S)
trength Measurement Message) along with the base station ID of the base station 602.
01 or the control station (MSC) (S90
2). Then, the base station 601 or the MSC receiving the PSMM updates the contents of the managed base station list (S903). The PSMM is a mobile terminal 60
0 is obtained from the received signal level of the pilot channel signal transmitted from the base station 602.

[0059] The base station list is a list showing a relationship indicating a transmission / reception state between each mobile terminal and each base station in order to indicate the priority of link assignment. For example, as shown in FIG. An active set corresponding to the PSMM and a candy date set (Candidate) are used for identifying the identification information (called terminal ID) of each mobile terminal and each base station ID.
set) and a neighbor set (Neighbor set).
In FIG. 13, the terminal ID is represented by an uppercase alphabet and the base station ID is represented by a lowercase alphabet. The active set corresponds to a case where a mobile station 600 can receive a pilot channel signal transmitted from a certain MSC. The candy date set transmits a pilot channel signal transmitted from the MSC side to the mobile terminal 6.
00 is received at a sufficient level, but is not in the active set. Further, the neighbor set is expected to become a candy date (candidate) soon, but this corresponds to a case where the pilot channel signal transmitted from the MSC side is still intermittently received.

At the base station or MSC that manages this base station list, the P
When the SMM is received, the base station list in FIG. 13 is updated accordingly. Specifically, the base station ID of the base station ID described at the intersection of the terminal ID corresponding to the mobile terminal that transmitted the PSMM and the relevant parameter at each level is updated. Update the content. As shown in FIG. 13, the base station ID described at each intersection may be one or plural.

Here, when the processing in S806 shown in FIG. 11, that is, when the direction of arrival of radio waves from a base station other than the base station currently communicating is estimated, of the plurality of other base station groups, The process of determining which base station is to be selected as the target in the direction of arrival using the base station list will be described with reference to FIGS. 14 and 15.

In the determination processing in S805 shown in FIG. 11, if it is determined that a predetermined time or more has elapsed since the last time the arrival direction was estimated, as shown in FIG. Then, the base station transmits a command for inquiring the base station list to the MSC via the base station (S1201). The base station or the MSC that has received the command determines, as a target base station in the direction of arrival, (1) at least one of the active stations in the base station list other than the base station currently communicating. In cases other than (2) and (1), if the candy date set in the base station list is not empty, at least one of them, (3)
(1) In cases other than (2), at least one of the neighbor sets in the base station list is selected (S120).
2) Notify the selected base station to the mobile terminal 600 (S
1203). Also, as shown in FIG. 15, after the base station list updating process (S903) shown in FIG. 12, the base station to be the arrival direction target is obtained from the base station list by the method as described in (1) to (3) above. A configuration is also conceivable in which a station is selected (S1301) and the selected base station is notified to the mobile terminal 600 (S1302). In this case, unlike the one in FIG. 14, there is an advantage that the processing time in S806 can be shortened because no base station list inquiry command is sent to the base station or MSC side. On the other hand, in the case of FIG.
Since the selection work is performed only when it is determined that a predetermined time or more has elapsed from the time of arrival direction estimation in the determination processing of S805, there is an advantage that the total work amount can be reduced.

Further, on the terminal side, based on the result of monitoring the pilot channel, the base station candidate most suitable for the next handover is determined based on the average height of the latest several electric field strength values and the lowest weakest value. Should be selected in advance,
At S806, the candidate may be selected.

According to the present embodiment, in addition to the earlier effect of accelerating the convergence of the adaptive control of the adaptive array antenna at the time of handover, a highly reliable handover based on the base station list indicating the priority of the link assignment is performed.
It is possible to obtain an effect that it can be realized by the same procedure as the conventional case using the omni-directional antenna for the mobile terminal.

It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications.

[0066]

As described above, according to the present invention,
It is possible to provide a mobile communication terminal device including an adaptive array antenna capable of realizing high-speed handover.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a wireless communication system including a mobile terminal device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a transceiver in the mobile terminal device according to the first embodiment.

FIG. 3 is a block diagram illustrating a configuration of a control circuit according to the first embodiment.

FIG. 4 is a diagram illustrating an arrival direction / weight coefficient storage unit according to the first embodiment;

FIG. 5 is a flowchart showing a flow of main processing according to the first embodiment;

FIG. 6 is a diagram illustrating an example of an internal configuration of a weight calculation unit 304 illustrated in FIG. 3;

FIG. 7 is a block diagram showing another configuration of the control circuit according to the first embodiment.

FIG. 8 is a block diagram showing still another configuration of the control circuit according to the first embodiment.

FIG. 9 is a diagram schematically illustrating a wireless communication system including a mobile terminal device according to a second embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a transceiver in a mobile terminal device according to the second embodiment.

FIG. 11 is a flowchart showing a main processing flow in the second embodiment.

FIG. 12 is a flowchart showing a part of a processing flow for updating a base station list in the second embodiment;

FIG. 13 is a diagram illustrating a base station list.

FIG. 14 is a flowchart showing another part of the processing flow for updating the base station list in the second embodiment.

FIG. 15 is a flowchart showing another part of the process flow according to the modification for updating the base station list in the second embodiment.

FIG. 16 is a diagram for explaining an outline of a wireless communication system including a conventional mobile terminal device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 mobile communication terminal device 101 first base station 102 second base station 110 array antenna 111, 112 antenna beam 201 low noise amplifier 202 filter 203 mixer 204 local signal generator 205 distribution Device 206 ... filter 207 ... quadrature demodulator 208 ... A / D converter 210 ... digital signal processing unit 211 ... multiplier 212 ... adder 213 ... detection circuit 214 ... control circuit 215 ... main synchronization circuit 216 ... sub synchronization circuit 217 218 ... switch 301 ... weight coefficient calculation unit 302 ... weight coefficient holding unit 303 ... arrival direction estimation unit 304 ... weight coefficient calculation unit 305 ... weight coefficient storage unit 600 ... mobile communication terminal device 601 ... first base station 602 ... second Base station 610 ... array antenna 611,612 ... antenna beam 701 ... low noise Sound amplifier 702 Filter 703 Mixer 704 Local signal generator 705 Distributor 706 Filter 707 Quadrature demodulator 708 A / D converter 709 Digital signal processing unit 710, 720 Receiving circuits 711, 721 Multiplication 712 722 adder 713 723 despreading circuit 714 724 detection circuit 715 725 control circuit 716 726 synchronization circuit 1401 initial value of weight coefficient according to arrival direction 1402 weight coefficient update calculation Unit 1403: Initial value output control circuit based on reception level

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) // H04J 3/00 H04J 13/00 DF term (Reference) 5J021 AA03 AA06 AA11 DB01 EA04 FA13 FA16 FA30 GA02 GA08 HA06 HA10 5K022 EE01 EE21 EE36 5K028 BB06 CC02 CC05 EE08 HH00 KK12 LL12 RR02 5K059 CC03 CC04 DD32 DD35 5K067 AA15 CC04 DD25 EE02 EE10 EE24 EE71 HH21 HH22 HH23 JJ39 JJ72 KK02KK

Claims (11)

[Claims] 1. A mobile communication terminal device that communicates with one of a first base station and a second base station and performs handover from the first base station to the second base station. An array antenna that outputs a signal; a plurality of multipliers that multiply a plurality of signals output from the array antenna by a weighting coefficient to output a multiplication result signal; and a reception signal from the multiplication result signal output from the multiplier. Receiving means for generating, based on the received signal output from the receiving means, control means for executing the calculation of the weighting coefficient, and adaptively controlling the multiplier by giving the calculated weighting coefficient, Initial value calculating means for calculating an initial value of the weighting coefficient before the handover, wherein the control means uses the initial value at the time of the handover to calculate the weighting factor. A mobile communication terminal device for starting calculation of a number. 2. An initial value calculating means, comprising: an estimating means for estimating an arrival direction of a radio wave from the second base station to the mobile communication terminal device; and the weighting coefficient calculated according to the arrival direction. The mobile communication terminal device according to claim 1, further comprising: storage means for storing an initial value of the mobile communication terminal. 3. A mobile communication terminal that communicates with one of a first base station and a second base station and performs handover from the first base station to the second base station. An array antenna that outputs a signal; a plurality of multipliers that multiply a plurality of signals output from the array antenna by a weighting coefficient to output a multiplication result signal; and a reception signal from the multiplication result signal output from the multiplier. Receiving means for generating, based on the received signal output from the receiving means, control means for executing the calculation of the weighting coefficient, and adaptively controlling the multiplier by giving the calculated weighting coefficient, Estimating means for estimating a direction of arrival of a radio wave from the second base station to the mobile communication terminal device, and storage means for storing information indicating the estimated direction of arrival; Initial value calculating means for calculating an initial value of the weighting coefficient before the handover, the control means, at the time of the handover, start calculating the weighting coefficient using the initial value. Mobile communication terminal device. 4. A mobile communication terminal device that communicates with one of a first base station and a second base station and performs handover from the first base station to the second base station. An array antenna that outputs a signal; a plurality of multipliers that multiply a plurality of signals output from the array antenna by a weighting coefficient to output a multiplication result signal; and a reception signal from the multiplication result signal output from the multiplier. Receiving means for generating, based on the received signal output from the receiving means, control means for executing the calculation of the weighting coefficient, and adaptively controlling the multiplier by giving the calculated weighting coefficient, An initial value calculating unit that calculates an initial value of the weighting coefficient before the handover; and a storage unit that stores the calculated initial value. During chromatography server, mobile communication terminal apparatus characterized by starting the calculation of the weighting coefficients using the initial value. 5. The communication between said first and second base stations,
The mobile communication terminal according to any one of claims 1 to 4, wherein wireless communication is performed according to a DMA (Time Division Multiple Access) method. 6. The mobile communication terminal device according to claim 2, wherein the estimation unit estimates the direction of arrival in a time zone other than a TDMA time slot. 7. A communication system between the first and second base stations.
The mobile communication terminal device according to any one of claims 1 to 4, wherein wireless communication is performed according to a DMA (Code Division Multiple Access) method. 8. Obtaining a base station list from the first base station or another base station, and selecting the second base station from a plurality of base stations based on the base station list. The mobile communication terminal device according to claim 7, wherein: 9. The method according to claim 1, wherein the initial value calculating means calculates an initial value of the weighting coefficient calculated according to the arrival direction by LMS (LMS).
4. The mobile communication terminal device according to claim 2, wherein updating is performed based on an adaptive control algorithm including east mean square. 5. 10. The apparatus according to claim 2, wherein said initial value calculating means outputs an initial value of said weighting coefficient calculated according to said direction of arrival when a reception level is higher than a predetermined threshold value. Or the mobile communication terminal device according to any one of 3. 11. A first synchronization circuit for bit synchronization and frame synchronization used in communication with the first base station, and a first synchronization circuit for bit synchronization and frame synchronization used in communication with the second base station. The mobile terminal communication device according to any one of claims 1 to 10, further comprising a second synchronization circuit.