JPH07131411A - Antenna switching type transmission control access method - Google Patents

Abstract

PURPOSE:To avoid multipath fading, to realize high-speed radio transmission capable of coping with the change of propagation circumstances, and to make a terminal station small-sized and inexpensive in the radio system where a control station stores plural terminal stations. CONSTITUTION:A control station 1-1 has directional antennas 1-2 to 1-5 different in directions, and terminal stations 1-6 to 1-11 have non-directional antennas. The control station transmits a permission signal while switching the directional antennas and waits for and receives the incoming signal from a terminal station placed under the control station. When any incoming signals are not received or reception of the incoming signal is terminated, the control station switches directional antenna to perform the same operation in another direction. The terminal station transmits the incoming signal when the signal quality of the permission signal from the control station is higher than a reference value. The transmission order of directions and the frequency in transmission of the outgoing signal and the permission signal from the control station are controlled in accordance with the traffic intensity of up data signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless access control method in a wireless communication system.

[0002]

2. Description of the Related Art (Prior Art 1: ICMA) As one of random access control technologies for mobile telephones, ICMA (empty space) aimed at preventing signal disappearance due to collision of uplink signals from a mobile station to a base station. There is a line control method. FIG. 8 shows a timing chart of ICMA. ICMA is a random access method in which the usage status of the uplink channel is left in the downlink channel. As shown in FIG. 8, when the uplink channel is in an idle state, a skyline signal (8-2) is notified and signal transmission from the mobile device is performed. Is permitted, and when it is in use, a prohibition signal (8-3) is issued to prohibit signal transmission from other mobile units. When transmitting a signal to the base station, the mobile device sends out the uplink signal (8-1) after confirming that the skyline signal (8-2) is broadcast in the downlink channel. Also, another mobile station that made a call request while the prohibition signal was being notified on the downlink channel continued to monitor the downlink control channel until the prohibition signal changed to a skyline signal, and then changed to a skyline signal. Immediately thereafter, signal transmission (8-4) is performed.

(Prior Art 2: Japanese Unexamined Patent Publication No. 2-79628) As an example of an access method of a system using a plurality of directional antennas as a control station, "high bit rate communication system for overcoming multipath" (Japanese Unexamined Patent Publication No. Hei-2- 79628). In this system, a reference signal for antenna selection is transmitted from the base station sequentially and periodically by switching each directional antenna of the base station. The wireless telephone that communicates with the base station also has a plurality of directional antennas, receives the reference periodic signal while switching the antenna of the own station, the propagation status and the antenna of the own station and the antenna of the base station at that time. The combination of is stored in memory. For example, when the base station and the wireless telephone each have six directional antennas 1 to 6,
The radio telephone sets the antenna of its own station to 1, receives the reference signals sequentially transmitted by the antennas 1 to 6 of the base station, and stores the propagation status for each combination of antennas in the memory. Then, the wireless telephone switches the antenna of its own station to 2 and performs the same operation. After that, the same operation is repeated up to the antenna 6, and a 6 × 6 table is created in the memory. When the wireless telephone tries to communicate with the base station, it selects the combination of antennas having the best characteristics from the table of propagation conditions stored in the memory and sets the communication antenna of its own station as the combination of the antennas. At the same time, the base station is instructed to use the designated antenna for communication with itself.

[0004]

With the improvement of the wireless transmission rate, the so-called multipath fading, which causes mutual interference of radio waves reaching the receiver via a plurality of different routes, becomes a serious problem. These radio waves are waves with different delays, and waves with a phase shift are combined by the receiver. Therefore, particularly in the case of high-speed digital wireless transmission with a short cycle per bit, the phase shift per bit is large, which is a major cause of transmission error. As one method of solving this problem, there is a method of removing an interference wave by narrowing the beam width of one antenna of a pair of wireless stations that perform communication.

By the way, when this method is applied to a radio communication system in which one base station accommodates a plurality of mobile stations such as a car telephone system and the antenna beam width on the base station side is made narrow, the antenna of the base station is used. It is necessary to change the directivity of each mobile device.

However, in the car telephone of the prior art 1, since one antenna is shared by a plurality of radio channels having different frequencies, it is impossible to change the directivity of the antenna of the base station for each mobile device. .

In the access method of the prior art 2, it is necessary to monitor the received signal for a relatively long time with respect to the instantaneous fluctuation of the signal, and it is not possible to follow the short-term change in the propagation situation due to shadowing or the like. is there. Further, when a plurality of directional antennas are used for the terminal station, there is a drawback that the configuration of the terminal station and the control of the system become complicated.

Therefore, in the present invention, in a centralized control type wireless system in which such a control station having a plurality of directional antennas accommodates a plurality of terminal stations, multipath fading is avoided and propagation environment changes. It is an object of the present invention to realize high-speed wireless transmission capable of responding promptly and to make the terminal station smaller and less expensive.

[0009]

According to the present invention, in order to solve the above problems, a reference signal for antenna selection as used in the prior art 2 is used instead of the reference signal for antenna selection. In addition, the permission signal, which has the meaning of permitting the transmission of the data signal to the terminal station, is sequentially transmitted from the multiple directional antennas of the control station, and the reception field strength of the permission signal at the terminal station exceeds the predetermined threshold. In case of data transmission. This threshold has two parameters, the received electric field and the received signal error rate, which are changed according to changes in the propagation situation. In addition, the control station constantly monitors the response rate of the terminal station to the permission signal from each directional antenna, increases the frequency of permission signal transmission for antennas with high response rates, and conversely the transmission frequency for antennas with low response rates. Lower.

[0010]

According to the present invention by the above operation, in a high-speed wireless transmission system consisting of one control station and a plurality of terminal stations accommodated in the control station, a plurality of directional antennas are installed in the control station, It is possible to perform communication between one of the plurality of directional antennas and one terminal station, and it is possible to avoid multipath fading. In addition, by using the permission signal as a reference when the terminal station selects the antenna of the control station, it is possible to send out the signal immediately after making a judgment on the propagation environment, and quickly respond to the propagation environment that changes from time to time. be able to. Furthermore, by optimally changing the transmission frequency of the permission signal for each directional antenna according to the traffic load of the terminal station on each directional antenna of the control station, effective use of radio frequency is possible. Become.

[0011]

FIG. 1 is a conceptual diagram of a wireless communication system to which the access method according to the present invention is applied. This figure shows that the control station uses the directional antennas 1-4 to communicate with the terminal stations 1-10.

FIG. 2 is a block diagram of the control station. The control unit (2-5) switches the directional antenna (2-1) based on the access method of the present invention by a switch (2-
While switching by 2), permit from transmitter (2-3) /
A call signal is transmitted and a signal from the terminal station is received from the receiver (2-4). Further, the memory (2-6) stores the history of the correspondence between the terminal station numbers accommodated by the control station and the numbers of the directional antennas that have received the reservation signal / response signal from each of the terminal stations. The data to be transmitted to the terminal station is temporarily stored in the buffer (2-7), and the arrival of the data is reported to the control unit. The control unit refers to the memory to select an antenna and transmits a signal to the terminal station.

FIG. 3 shows a block diagram of the terminal station.
The transmission data to the control station is temporarily stored in the buffer (3-8), and the arrival of the data is reported to the control unit (3-6).
The control unit waits for and receives the permission signal from the control station, and when the electric field strength, the signal error rate, or both of them exceeds the threshold stored in advance in the memory (3-7), the data is transmitted according to the sequence described later. Send. The value of the electric field threshold is determined by the electric field strength detection unit (3
It is rewritten by the control unit according to the radio propagation situation between the control station and the terminal station, which is estimated from the measured value of -5).
Further, when a call signal addressed to the own terminal station is received during the reception of the downlink signal from the control station, the response signal is transmitted and the subsequent data signal is received.

FIG. 4 shows a timing chart at the time of transferring an upstream data signal in the access system of the present invention, a received electric field strength of a downlink signal at a terminal station, and an outline of a switching operation of a directional antenna by a control station. At the time of transferring the upstream data signal, the control station first transmits permission signals (4-1 to 4-3) by sequentially using the directional antennas Nos. 2, 3, and 4. The terminal station that has requested the uplink data transfer
The permission signal (4
-3) received electric field strength (4-9) is the threshold (4
Since it has exceeded -8), the reservation signal (4-4) including the own station number is transmitted within the response waiting time of the permission signal. There are three types of concrete threshold values, that is, the received electric field strength, the signal error rate, and a combination of both. In the present embodiment, the received electric field strength is shown. The control station, which correctly receives the reservation signal, keeps the antenna locked to No. 4 (4-12) and receives the reception signal (4- (4)) including the terminal station number written in the reservation signal.
5) is transmitted. The terminal station receives this and transmits the uplink data (4-6). When the control station finishes receiving the data signal, it switches the directional antenna to enable the permission signal (4
-3) Transmission is restarted. (In this figure, the 4th antenna is used to transmit the permission signal again.)

FIG. 5 shows a timing chart at the time of downlink data signal transfer. At the time of downlink transfer, the control station transmits a calling signal (5-5) including the number of the destination terminal station of the downlink data signal instead of the permission signal. At this time, the control station displays the correspondence table (6-
Referring to 1), the antenna used for transmission is selected. Upon receiving this, the terminal station immediately transmits the response signal (5-6) and receives the subsequent downlink data signal (5-7). When the transmission of the data signal (5-7) is finished, the control station switches the directional antenna and restarts the transmission of the permission signal (5-3).

FIG. 6 shows an operation algorithm of the control station in this embodiment. At the time of downlink data transmission, the control station refers to the information (6-1) in the memory shown in FIG. 2 to select the directional antenna that was most frequently used when receiving the uplink signal from the destination terminal station. Although a paging signal is transmitted, it is possible that radio waves may not reach the terminal station due to changes in the propagation situation or movement of the terminal station. When there is no response from the calling terminal station, the directional antenna having the next highest frequency of use is selected and the calling signal is retransmitted.
Hereinafter, the directional antennas are switched in descending order of frequency of use, and the process is repeated until a response signal from the calling terminal station is received or a calling signal is transmitted from all the antennas. Also, the traffic information of the data transmitted / received by each directional antenna at the time of receiving the reservation signal and the response signal is updated, and the selection frequency of each antenna at the time of transmitting the permission signal is set according to an algorithm from the value (6-2). As a selection method at the time of antenna switching, a method of generating a random number inside the control station and switching each directional antenna with a probability distribution according to the selection frequency from the value can be considered.

FIG. 7 shows the operation algorithm of the terminal station in this embodiment. In the mode in which the terminal station receives the downlink control signals (permission signal and ringing signal) from the control station, if it does not receive the ringing signal or the permission signal exceeding the threshold within a certain period of time, it lowers the threshold value. . Further, in the idling state where there is no transmission / reception data, the threshold value is increased when the received electric field strength is sufficiently higher than the threshold value. By these controls, the terminal station can change the threshold value according to the change of the propagation situation with the control station.

[0018]

EFFECTS OF THE INVENTION By using the antenna switching type transmission control access method according to the present invention, in a high-speed wireless transmission system consisting of one control station and a plurality of terminal stations accommodated in the control station, a plurality of directions are directed to the control station. It is possible to install a directional antenna and perform communication between one of the plurality of directional antennas and one terminal station, and avoid multipath fading. Further, by using the permission signal described in claim 1 as a reference when the terminal station selects the antenna of the control station, it is possible to transmit a signal immediately after making a judgment on the propagation environment, and the propagation which changes at any time. You can quickly respond to the environment. Furthermore, as described in claim 7, the transmission frequency of the permission signal is optimally changed for each directional antenna in accordance with the traffic load of the terminal station on each directional antenna of the control station, whereby Effective use of frequencies is possible.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a wireless communication system using the present invention.

FIG. 2 is a block diagram of a control station configuration in the embodiment.

FIG. 3 is a block diagram of a terminal station configuration in the embodiment.

FIG. 4 is a timing chart and an outline of operation when an upstream data signal is transferred in the access method of the present invention.

FIG. 5 is a timing chart when transferring a downlink data signal in the access system of the present invention.

FIG. 6 is a control station operation algorithm in the embodiment.

FIG. 7 is a terminal station operation algorithm.

FIG. 8 is a timing chart of ICMA-DR described in Related Art 2.

[Explanation of symbols]

1-1 Control station 1-2 to 1-5 Directional antenna 1-6 to 1-11 Terminal station 2-1 Multiple directional antennas 2-2 Antenna / transmission / reception changeover switch 2-3, 3-3 Transmitter 2 -4, 3-4 Receiver 2-5 Control station control section 2-6 Memory (terminal station / directional antenna number correspondence table) 2-7, 3-8 Transmission data buffer 2-8, 3-9 Data input terminal 2-9, 3-10 Data output terminal 3-1 Antenna 3-2 Transmission / reception changeover switch 3-5 Electric field strength measurement device 3-6 Terminal station control unit 3-7 Memory (Threshold value (reception electric field strength or signal error rate) ) 4-1 to 4-3 Directional antennas 2 to 4 (1-3 to 1-)
5) Permission signal from 4-4 Reserved signal from terminal station 4-5 Reception signal from control station 4-6 Upstream data signal from terminal station 4-7 Permission signal from directional antenna 1 (1-2) 4-8 Threshold of reception electric field strength at terminal station 4-9 Change of reception electric field strength of permission signal at terminal station 4-10 to 4-13
Periods in which 3, 4, 1 (1-3, 1-4, 1-5, 1-2) are used 5-1 to 5-4 Directional antennas 1 to 4 (1-2 to 1-
5) Permit signal 5-5 Call signal from directional antenna 4 (1-5) 5-6 Response signal from terminal station 5-7 Downlink data signal from directional antenna 4 (1-5) 6- 1 Correspondence table of the directional antenna numbers of the control station used in the previous communication with each terminal station 6-2 Each directional antenna of the control station and the communication traffic in each antenna, and the antennas obtained from it Relationship table of selection frequency 8-1 Uplink signal (uplink) 8-2 Skyline signal (downlink) 8-3 Prohibited signal (downlink) 8-4 Uplink signal from another mobile device (uplink)

Claims (4)

[Claims] 1. A control station and a plurality of terminal stations communicating with the control station, wherein the control station has a pair of transceivers and a plurality of directional antennas, and the terminal station has a pair of transmission and reception. And a single omnidirectional antenna, and notifies the signal permission signal from the control station to the terminal station under the control station to permit transmission, the transmission of the uplink data signal from the terminal station to the control station In doing so, the terminal station transmits the uplink data signal when it receives the permission signal, the control station transmits the permission signal from the first antenna of the plurality of directional antennas of the control station, and Time said first
When the uplink data signal from the terminal station under control of the control station is received by the antenna of, and the uplink data signal from the terminal station is not received, or when the reception of the uplink data signal is completed, the control is performed. An antenna switching type transmission characterized in that the station selects a second directional antenna different from the first antenna, transmits the permission signal, and then repeats the same operation while switching the directional antenna. Control access method. 2. When the terminal station receives the permission signal, the signal quality of the permission signal is a reception electric field strength and a signal error rate which are set to be adjustable in advance in the terminal station according to a propagation situation. 2. The antenna switching type transmission control access method according to claim 1, wherein the terminal station transmits an upstream data signal when both of the thresholds are small and both are exceeded. 3. When the control station receives an uplink data signal transmitted from the terminal station to the control station, the control station receives the uplink data signal from the terminal station that transmitted the uplink data signal. A history of the correspondence relationship of the directional antennas used for receiving is stored, and when the control station transmits a downlink data signal to the terminal station, the history of the correspondence relationship is referred to to refer to the terminal station. 2. The antenna switching type transmission control access method according to claim 1, wherein the antennas used when receiving the upstream signal from are preferentially used in order from the antenna with the highest frequency of use. 4. The antenna switching according to claim 1, wherein the transmission frequency of the permission signal is changed for each directional antenna according to the traffic volume of the upstream data signal transmitted from the terminal station. Type send control access method.