JP4130374B2 - Wireless device and communication control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio apparatus and a communication control method suitable for use in a spatial division multiple access (SDMA) type radio communication system.
[0002]
[Prior art]
A conventional SDMA wireless communication system includes an adaptive array antenna in a wireless base station, and forms a plurality of transmission beams having radiation patterns with different directivities for each user terminal (hereinafter referred to as a terminal). Sending radio waves for your device. When a radio base station forms a radiation pattern of a certain terminal, it directs the direction of the terminal of the transmission partner by adaptive beam forming (Adaptive Beam Forming), and by adaptive null steering (Adaptive Null Steering). A null is formed in the direction of the other terminal. As a result, the same frequency channel is allocated to a plurality of terminals at the same time, thereby increasing the channel utilization efficiency.
[0003]
An example of the SDMA wireless communication system described above is PHS (registered trademark) (Personal Handy-phone System). In this system, a radio base station wirelessly connects to a terminal by a time division multiplex system (TDMA / TDD) defined in the PHS (registered trademark) standard, and in addition to the time division multiplex Further, it performs spatial multiplexing and communicates with the terminal. Then, the radio base station forms an appropriate radiation pattern based on reception information with the terminal (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-58061
[Problems to be solved by the invention]
However, in the conventional PHS (registered trademark) radio base station described above, when a plurality of terminals are accommodated by spatial multiplexing on the same time division channel, a terminal in the spatial multiplexing uses a communication channel (TCH). When the mode used during communication (for example, a mode for performing voice communication, data communication, etc.) is shifted to a mode during transmission / reception of synchronization burst (establishment of synchronization), a radiation pattern is appropriately formed for the terminal during transmission / reception of synchronization burst. There are times when you can't. For example, when the wireless environment is temporarily deteriorated due to the movement of the terminal and the terminal is in synchronization burst transmission / reception, the past received information held in the wireless base station becomes invalid, so the synchronization burst An appropriate radiation pattern for a terminal that is transmitting / receiving cannot be formed appropriately.
[0006]
As a result, a transmission beam directed to another terminal communicating on the same time division channel becomes an interference wave with respect to the terminal that is transmitting and receiving the synchronization burst, and if the synchronization burst is not normally transmitted and received, Synchronization establishment fails. As a result, handover is started in the terminal that is transmitting and receiving the synchronous burst, and spatial multiplexing cannot be continued, resulting in a problem that the channel utilization efficiency decreases. Furthermore, there is a problem in that a transmission radio wave for a terminal that is transmitting and receiving a synchronous burst becomes an interference wave for another terminal that is communicating on the same time division channel, and adversely affects the terminal that is communicating.
[0007]
In addition, since there is no reception information for a terminal that has undergone synchronous burst transmission / reception due to switching back from handover, an appropriate radiation pattern cannot be formed appropriately as well. As a result, if the synchronization burst is not normally transmitted / received, there is a possibility that switching from the handover may fail.
[0008]
For this reason, when a terminal in communication and a terminal in synchronization burst transmission / reception (synchronization established) are accommodated by spatial multiplexing on the same time division channel, adverse effects on communication quality are prevented. It is hoped that. In particular, failure to switch back from handover may lead to communication disconnection. From the viewpoint of communication reliability, the reliability of synchronous burst transmission / reception is ensured for terminals that are in sync burst transmission / reception due to switch-over from handover. There is a strong demand for improvement.
[0009]
The present invention has been made in view of such circumstances, and its purpose is to accommodate terminals in communication and terminals in synchronization burst transmission / reception (synchronization established) by spatial multiplexing on the same time division channel. Therefore, it is an object of the present invention to provide a radio apparatus and a communication control method that can prevent adverse effects on communication quality.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, a radio apparatus according to the present invention is a radio apparatus that performs radio communication with a plurality of terminals by time division multiplexing and spatial multiplexing, and establishes synchronization with a communicating terminal by switching back from a handover. The switch-back terminal is in the process of establishing synchronization with the time-switched channel or the switch-back terminal that is establishing synchronization by switch-back from another time-division channel. It is characterized by comprising detection means for detecting based on shifting to a mode, and control means for switching the communicating terminal to a different time division channel by the detection.
[0011]
A communication control method according to the present invention is a communication control method in a radio apparatus that performs radio communication with a plurality of terminals by time division multiplexing and spatial multiplexing, and is in the process of establishing synchronization with a communicating terminal by switching back from a handover . The switch-back terminal or the switch-back terminal that has established synchronization by switch-back from another time-division channel is accommodated by spatial multiplexing in one time-division channel, and the switch-back terminal is in a mode in which synchronization is established. It includes a detection process that is detected based on transition, and a control process that switches the communicating terminal to a different time division channel based on the detection.
[0012]
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 example of a wireless communication system having a wireless base station (wireless device) and a mobile station (mobile terminal) according to an embodiment of the present invention. In this example, a PHS (registered trademark) (Personal Handy-phone System) will be described as a wireless communication system according to the present embodiment.
[0013]
In FIG. 1, a radio base station 1 spatially multiplexes a plurality of signals at the same frequency using a spatial multiplexing system in addition to a time division multiplexing (TDMA / TDD) system defined by the PHS (registered trademark) standard. Thus, digital wireless communication is performed with a plurality of terminals. The terminal 2-1 (UserB) and the terminal 2-2 (UserC) are PHS (registered trademark) terminals. The terminals 2-1 and 2-2 are communicating with the radio base station 1 by using the respective communication channels (TCH) by spatial multiplexing on the same time division channel. For example, voice calls and data communication are performed via TCH.
[0014]
FIG. 2 is a block diagram showing a configuration of the radio base station 1. The radio base station 1 includes an adaptive array antenna 11, a radio unit 12, a signal processing unit 13, a line interface unit 14, and a control unit 15.
[0015]
The radio base station 1 performs time division multiplexing of four channels (one for the control channel (CCH) and three for the communication channel (TCH)) in one TDMA frame in accordance with the PHS (registered trademark) standard. Signals on a maximum of m communication lines (m is an integer of 2 or more) capable of spatial multiplexing for one time division channel are processed in parallel. One TDMA frame has a period of 5 milliseconds, and is composed of four transmission time slots and four reception time slots obtained by dividing each period into eight equal parts. A set of one transmission time slot and one reception time slot constitutes one time division channel by time division multiplexing.
[0016]
In FIG. 2, the adaptive array antenna 11 is connected to the radio unit 12. The radio unit 12 includes a transmission unit and a reception unit, and controls the adaptive array antenna 11 in a time division manner to switch between transmission and reception. The transmission unit of the radio unit 12 includes an upper converter, a power amplifier, and the like, converts a signal input from the signal processing unit 13 from a low frequency to a high frequency, amplifies the signal to a transmission output level, and outputs the amplified signal to the adaptive array antenna 11. . The receiving unit of the radio unit 12 includes a low noise amplifier, a down converter, and the like, converts a signal received by the adaptive array antenna 11 from a high frequency to a low frequency, amplifies it, and outputs it to the signal processing unit 13.
[0017]
The signal processing unit 13 performs control related to directivity pattern formation, that is, separates and extracts received signals from each spatially multiplexed terminal input from the wireless unit 12 and outputs the received signals to the line interface 14. In addition, control is performed to generate a signal weighted for spatial multiplexing so that the transmission signal input from the line interface 14 can be transmitted to a desired terminal and output the signal to the radio unit 12. The signal processing unit 13 performs parallel processing on a maximum of m signals spatially multiplexed in one time division channel. The signal processing unit 13 is realized by, for example, a DSP (Digital Signal Processor).
[0018]
The line interface 14 has a TDMA / TDD processing function, is connected to a digital communication line such as an ISDN line, and a plurality of signals (voice or data baseband) between the plurality of communication lines and the signal processing unit 13. Signal).
[0019]
The control unit 15 controls the entire radio base station 1. Further, the control unit 15 performs time division channel switching control processing for switching the time division channel accommodating the terminal with respect to the line interface 14. The control unit 15 includes a CPU and a memory.
[0020]
Next, operations related to communication control in the wireless communication system of FIG. 1 will be described with reference to FIGS. FIG. 3 is a sequence chart showing a flow of communication processing between a terminal and a radio base station that are shifted to a mode in which synchronization burst transmission / reception (synchronization is established). FIG. 4 is a diagram illustrating an example of a radiation pattern of a transmission beam when two terminals are spatially multiplexed on the same time division channel. 5 to 8 are diagrams for explaining switching control of the time division channel.
[0021]
First, in step S1 of FIG. 3, the terminal 2-1 (UserB) and the terminal 2-2 (UserC) establish a time division channel “Slot3” between the radio base station 1 and the radio base station 1 as shown in FIG. Each of them is in communication (for example, during a call) using TCH by spatial multiplexing. Here, in another time division channel “Slot 2”, User A is communicating using TCH, and in time division channel “Slot 4”, User D is communicating using TCH. A transmission beam radiation pattern 101 for the terminal 2-1 (User B) at this time is shown in FIG. As shown in FIG. 4, in the radiation pattern 101, a directivity pattern of the transmission beam is formed in the direction of the terminal 2-1 (UserB), and a null pattern is formed in the direction of the terminal 2-2 (UserC). ing. As a result, the communication quality for the terminal 2-1 (UserB) is kept good, and the transmission beam for the terminal 2-1 (UserB) is prevented from becoming an interference wave of the terminal 2-2 (UserC). .
[0022]
Next, in step S2 of FIG. 3, the terminal 2-2 (UserC) shifts to a mode in which synchronization burst transmission / reception (synchronization is being established) due to some condition. As a result of this mode transition, the control unit 15 of the radio base station 1 causes the terminal 2-1 (User B) in communication with the terminal 2-1 (User B) in communication and the terminal 2-2 in transmission and reception of the synchronization burst in the time division channel “Slot 3” as shown in FIG. 2 (UserC) is detected by spatial multiplexing.
[0023]
Next, the control unit 15 switches the terminal 2-1 (User B) that is communicating on the time division channel “Slot3” to a different time division channel. In this example, as shown in FIG. 7, the time division channel “Slot 4” is switched. As a result, in the time division channel “Slot4”, the terminal 2-1 (UserB) and the UserD terminal are spatially multiplexed and are in communication using TCHs. Further, the time division channel “Slot 3” accommodates only the terminal 2-2 (User C) that is currently transmitting and receiving the synchronous burst. As a result, transmission / reception of the synchronization burst (SYNC) with the terminal 2-2 (UserC) is stably performed. Further, in the time division channel “Slot4”, since the reception information of the terminal 2-1 (UserB) in the time division channel “Slot3” is valid, an appropriate radiation pattern is formed, and the communication quality is kept good.
[0024]
Next, when the synchronous burst transmission / reception with the terminal 2-2 (UserC) succeeds, in step S3 of FIG. 3, the terminal 2-2 (UserC) uses the time division channel “Slot3” as shown in FIG. The communication mode using the TCH is shifted to, for example, a call is resumed.
[0025]
As described above, according to the present embodiment, when a terminal in communication and a terminal in synchronization burst transmission / reception (synchronization establishment) are accommodated by spatial multiplexing on the same time division channel, The terminal is switched to a different time division channel. As a result, synchronization burst transmission / reception with a terminal during synchronization burst transmission / reception is performed stably, and communication quality of the terminal during communication is maintained well, and adverse effects on communication quality can be prevented. it can.
[0026]
In the above-described embodiment, the control unit 15 detects that the communicating terminal and the switching terminal that has established synchronization by switching from the handover are accommodated by spatial multiplexing on one time division channel. By this detection, the terminal in communication may be switched to a different time division channel.
In addition, when a plurality of terminals in synchronization burst transmission / reception are accommodated in one time division channel, the control unit 15 detects the presence / absence of a switching terminal that is transmitting / receiving synchronization bursts by switching back from handover, If a return terminal is detected by this detection, all terminals other than the return terminal may be switched to different time division channels.
This improves the reliability of synchronization burst transmission and reception, especially for terminals that are in sync burst transmission / reception due to switching back from handover, and prevents failure of switching back from handover. Will improve. In addition to switching back from handover, the same processing is performed when moving to another channel and then switching back to the original channel. Note that “switching back” refers to returning the same terminal to a place (radio base station or time division channel) where a specific terminal has been accommodated until just before.
[0027]
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.
[0028]
【The invention's effect】
As described above, according to the present invention, when a terminal that is establishing synchronization (synchronized burst transmission / reception) and a terminal that is communicating are accommodated by spatial multiplexing on the same time division channel, Are switched to different time division channels. As a result, synchronous burst transmission / reception with a terminal that has established synchronization is stably performed, and communication quality of the terminal that is performing communication is maintained well, and adverse effects on communication quality can be prevented. .
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a radio communication system having a radio base station and a mobile station according to an embodiment of the present invention.
2 is a block diagram showing a configuration of a radio base station 1. FIG.
FIG. 3 is a sequence chart showing a flow of communication processing between a terminal and a radio base station that shift to a mode during synchronous burst transmission / reception.
FIG. 4 is a diagram showing an example of a radiation pattern of a transmission beam when two terminals are spatially multiplexed on the same time division channel.
FIG. 5 is a first diagram for explaining switching control of a time division channel.
FIG. 6 is a second diagram for explaining time-division channel switching control;
FIG. 7 is a third diagram for explaining time-division channel switching control;
FIG. 8 is a fourth diagram for illustrating time-division channel switching control;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Wireless base station (wireless apparatus), 2-1 and 2-2 ... Portable terminal, 11 ... Adaptive array antenna, 12 ... Radio | wireless part, 13 ... Signal processing part, 14 ... Line | wire interface part, 15 ... Control part

Claims (2)

In a wireless device that performs wireless communication with a plurality of terminals by time division multiplexing and spatial multiplexing,
Accommodates a terminal in communication and a switch-back terminal that is establishing synchronization by switch-back from handover or a switch-back terminal that is establishing synchronization by switch-back from another time-division channel in one time-division channel by spatial multiplexing Detecting means for detecting that the switching terminal shifts to a mode in which synchronization is established; and
Control means for switching the communicating terminal to a different time division channel by the detection;
A wireless device comprising: A communication control method in a wireless device that performs wireless communication with a plurality of terminals by time division multiplexing and spatial multiplexing,
Accommodates a terminal in communication and a switch-back terminal that is establishing synchronization by switch-back from handover or a switch-back terminal that is establishing synchronization by switch-back from another time-division channel in one time-division channel by spatial multiplexing A detection process for detecting that the switching terminal shifts to a mode in which synchronization is established;
A control process of switching the communicating terminal to a different time division channel by the detection;
The communication control method characterized by including.

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