JP2006319447A - Wireless station apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of making TDD ratios match with each other between wireless stations even when a communication state is considerably deteriorated resulting in that an FWA system with a variable TDD ratio cannot inform the stations of TDD ratio information. <P>SOLUTION: A TDD ratio control method for controlling a ratio of a transmission time to a reception time in a wireless station apparatus making wireless communication, includes: a means for detecting a communication state; and a means for fixing the ratio of the transmission time to the reception time in response to the communication state. The wireless station apparatus is configured of at least: a wireless communication section 1; a modulation section 3; a demodulation section 4; and a control section 5, allows the control section 5 to control the ratio of the transmission time to the reception time in response to a communication traffic quantity, detects the communication state, and fixes the ratio of the transmission time to the reception time depending on the communication state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio station apparatus, and more particularly to a radio station apparatus that performs control of a TDD (Time Division Duplex) ratio.

  The subscriber wireless access system (FWA: Fixed Wireless Access system, hereinafter referred to as the FWA system) is a high-speed system that uses millimeter-wave or microwave radio for purposes such as complementary use of optical fiber networks and communication between remote islands. This is a system for providing a line to a subscriber. (See Patent Document 1)

  One of the FWA systems is disclosed in Patent Documents 2 to 4. In the FWA system of Patent Document 2, the wireless station apparatus has a plurality of modulation / demodulation units. In the FWA systems of Patent Documents 2 and 3, when reception field strength and equivalent error power are obtained as communication state information, communication can be performed by switching to a modulation method having the maximum transmission capacity within a range where there is no communication error. Further, in the FWA systems of Patent Documents 2 and 4, when the traffic volume is obtained as the traffic information and the system adopts TDD as the duplex method, the transmission / reception asymmetry of the traffic is changed by changing the TDD time ratio. Can be adapted to.

Japanese Patent Laid-Open No. 2003-324412 JP 2004-260698 A JP 2004-72666 A JP 2004-7487 A

  In the FWA system having a variable TDD time ratio disclosed in Patent Document 2, when the communication state is significantly deteriorated, a modulation scheme having the maximum transmission capacity within a range without communication error cannot be found. At this time, an error is mixed in data transmitted / received by radio, the TDD ratio cannot be received accurately, and the TDD ratio cannot be made the same between radio stations. As a result, communication may not be maintained.

In order to solve the above problems, the FWA system of the present invention
In a TDD ratio control method for controlling a ratio between a transmission time and a reception time in a wireless station apparatus that performs wireless communication,
Means for detecting a communication state and means for fixing the time, the reception time, and the ratio according to the communication state are provided.
Further, in the radio station apparatus, which is composed of at least a radio communication unit, a demodulation unit, a modulation unit, and a control unit, and controls the ratio of the transmission time and the reception time according to the communication state by the control unit,
The communication state is detected, and the ratio between the transmission time and the reception time is fixed according to the communication state.

  According to the present invention, even when the communication state deteriorates and the TDD ratio cannot be accurately transmitted / received, the TDD ratio can be made the same between the radio stations, so that communication can be performed without mistaking the TDD ratio between the radio stations. Is possible.

The configuration of the radio station is shown in FIG. The radio station shown in FIG. 1 includes a radio communication unit 1, a radio path switching unit 2, a modulation unit 3, a demodulation unit 4, a radio router 5, and a control unit 6. Two-way wireless communication.
The wireless communication unit 1 performs wireless communication with a communication partner wireless station via a wireless antenna. The wireless communication unit 1 is, for example, an RF front end, and inputs / outputs analog or digital intermediate frequency signals to / from the wireless path switching unit 2.
The radio path switching unit 2 switches transmission / reception of radio signals for each frame. For example, the intermediate frequency signal multiplexed in transmission / reception by TDD is switched to and connected to the modulation unit 3 or the demodulation unit 4 according to the TDD timing. Further, similarly to Patent Document 2, when a plurality of wireless communication units 1, modulation units 3, and demodulation units 4 are provided, the combination is also switched.
The modulation unit 3 performs signal modulation processing using the modulation method designated by the control unit 6.
The demodulator 4 performs a demodulation process on the received signal. At that time, the demodulation unit 4 detects the communication state as RSSI (Received Signal Strength Indicator), equalization error power, or the like. Further, as described later, demodulation method information is obtained from a control channel modulated by a predetermined modulation method, and the demodulation method is automatically selected.
The wireless router 5 has a layer 3 routing function similar to that of a normal router, and performs communication with a network (LAN), monitoring of a network state, and the like. Also, processing such as frame / deframe of a radio signal frame and necessary buffering is performed.
Based on the signal received by the demodulator 4 and information notified from the wireless router 5, the control unit 6 determines the modulation method, calculates the traffic volume based on the network state, and transmits and receives the radio signal. Time ratio determination processing and the like are performed, and the modulation unit 3 and the radio path switching unit 2 are controlled based on these.

  Next, FIG. 2 shows an example of a radio signal frame format in the FWA system using the TDD scheme. One frame includes a transmission frame and a reception frame, and each frame includes a preamble part (PRA), a data part (DATA), a termination part (T), and a guard time (GT).

  The preamble part (PRA) includes a continuous wave (CW) for detecting and correcting the initial phase of the frame on the demodulation side, a unique word (UW) for frame synchronization, symbol synchronization, and equalizer training, and a radio station. And a control channel (CCH) used for transmission / reception of control signals between them, which uses a modulation scheme with less error generation than a modulation scheme used for data transmission. For example, when a modulation scheme equal to or higher than QPSK (Quadrature Phase Shift Keying) is used for data transmission, the control channel is set to BPSK (Bi-Phase Shift Keying). This control channel is used for transmission / reception of information such as a communication state, a TDD ratio, and a traffic amount described below.

The data portion (DATA) is composed of blocks each having 1088 symbols, and is provided with 1 to 11 blocks for each of the transmission frame and the reception frame. The total number of blocks of the transmission frame and the number of blocks of the reception frame is 12 blocks. It is comprised so that. This ratio of the number of blocks is called a TDD ratio. FIG. 3 shows a frame format when the TDD ratio is 6: 6.
The guard time (GT) is provided so that the transmission frame and the reception frame do not overlap each other, and the guard time of the transmission frame is a non-transmission section with an amplitude of zero.

Next, the modulation method determination process will be described with reference to FIG.
The modulation scheme determination process is performed by the control unit 6 for each wireless station. When each wireless station receives a wireless signal from a communication partner wireless station, each wireless station measures the communication state from the received signal and transmits it to the communication partner wireless station. The control unit obtains the communication state of the communication partner from the receiving unit (S41), obtains a modulation method that allows normal data transmission from the communication state (S42), and changes the modulation method of the modulation unit ( S43).

Next, the flow of TDD ratio determination processing when wireless communication is performed between two wireless stations will be described with reference to FIG.
Here, the TDD ratio is determined by one of the two wireless stations. Hereinafter, this radio station is referred to as an upper radio station. The other radio station follows the TDD ratio instructed by the higher radio station. Hereinafter, this radio station is referred to as a lower radio station. Further, a signal transmitted from the upper radio station to the lower radio station is referred to as a downlink signal, and a signal transmitted from the lower radio station to the upper radio station is referred to as an uplink signal.

The lower radio station transmits the traffic amount obtained from the radio router on the lower radio station side to the upper radio station. Upon receiving the traffic volume from the lower radio station, the upper radio station performs a TDD ratio determination process based on the traffic volume obtained from the radio router on the upper radio station side and the traffic volume of the lower radio station. When the TDD ratio is obtained, the upper radio station transmits the determined TDD ratio to the lower radio station. In order to match the TDD ratio change timing between the upper radio station and the lower radio station, each radio station synchronizes timing and simultaneously changes the TDD ratio. Transmission / reception is performed with the changed TDD ratio from the first radio signal frame after the change is made.
The traffic amount here is, for example, the amount of data (communication amount) to be transmitted from the own station to the partner radio station, and may be measured as the amount of data buffered for wireless transmission by the wireless router.

Next, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 6 shows a modulation scheme determination process based on the present invention. The communication state of the communication partner is acquired from the receiving unit 3 (S61), and a modulation method capable of normally performing data transmission from the communication state is obtained in the same manner as in Patent Document 3 (S62).
When the modulation method with the minimum transmission capacity (QPSK in the case of FIG. 6) is selected from among a plurality of modulation methods (Yes in S63), the TDD ratio fixed flag is turned on (S64). Otherwise (S64 No), the TDD ratio fixed flag is turned off (S65). Then, the modulation method of the modulation unit is changed (S66).

  FIG. 7 shows a TDD ratio determination process based on the present invention. When the TDD ratio fixing flag is on (S67 Yes), the TDD ratio is fixed to a predetermined ratio (S69). When the TDD ratio fixed flag is off (No in S67), the optimum TDD ratio is calculated based on the traffic amounts of the upper radio station and the lower radio station (S68).

Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 8 shows a TDD ratio determination process based on the present invention. When the modulation method is the modulation method with the smallest transmission capacity (S71 Yes), the TDD ratio is fixed to a predetermined ratio (S73). In other cases (No in S71), the optimum TDD ratio is calculated based on the traffic amounts of the upper radio station and the lower radio station (S72).

  Note that the TDD ratio to be fixed is fixed at a certain ratio, but may be different depending on the amount of information communicated between the upper radio station and the lower radio station. For example, when the same amount of information is communicated between the upper radio station and the lower radio station, the amount of information from the upper radio station to the lower radio station is large with the same transmission time and reception time (6: 6). In this case, the ratio of the downlink signal transmission time is increased (for example, 11: 1). Alternatively, a fixed TDD ratio ratio may be determined from an average value of TDD ratios in a normal communication state, and the ratio may be exchanged between radio stations.

Radio station apparatus based on the present invention Radio frame format used in TDD FWA system Radio frame format with a TDD ratio of 6: 6 Modulation method decision process follow chart Flow chart of TDD ratio determination process Flow chart of modulation scheme determination processing based on first embodiment of the present invention Flowchart of TDD ratio determination processing based on the first embodiment of the present invention Flowchart of TDD ratio determination processing based on second embodiment of the present invention

Explanation of symbols

  1: wireless communication unit, 2: wireless path switching unit, 3: modulation unit, 4: demodulation unit, 5: wireless router, 6: control unit

Claims (1)

In a radio station apparatus comprising at least a radio communication unit, a demodulation unit, a modulation unit, and a control unit, wherein the control unit controls the ratio of transmission time and reception time according to the communication state.
A radio station apparatus characterized by detecting a communication state and fixing a ratio between the transmission time and the reception time according to the communication state.

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