JP3243989B2 - Wireless communication control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication control device serving as a base station in a mobile communication system.

[0002] Conventionally, a TDMA (Time Division) system used as a communication system of a mobile communication system is used.
n Multiple Access: Time Division Multiple Access (PHS)
The description will be made with reference to an example of an ndy phone system. FIG. 5A shows a frame configuration of a wireless communication control device serving as a base station, and FIG. 5B shows a frame configuration of a mobile terminal station, which is described by matching their time axes. One frame is composed of eight slots called transmission slots Tx0 to Tx3 and reception slots Rx0 to Rx3. Between the base station and the mobile terminal station, the transmission slots Tx0
Communication is performed between Tx3 and the reception slots Rx0 to Rx3. That is, for example, the base station transmits its own transmission slot Tx
1, the mobile terminal station receives its own reception slot Rx1
, And the mobile terminal station transmits in its own transmission slot Tx1, and the base station receives in its own reception slot Rx1 so that bidirectional communication is possible.

[0003] Further, a transmission slot Tx0 and a reception slot Rx0 are used for a control channel.
1 to Tx3 and reception slots Rx1 to Rx3 are allocated for a communication channel. That is, the base station can communicate with up to three mobile terminal stations.
Note that the control channel is not transmitted every frame, but in the case of a PHS public system, the control channel information is transmitted once every 20 frames.

Communication between a base station and a mobile terminal station is performed in the following procedure. For example, when a call is received from a base station to a mobile terminal station (actually, a call is made from a terminal station connected to a wired line to which the base station is connected to the mobile terminal station): Call the designated mobile terminal station using the control channel. (2) The mobile terminal station that has received the call transmits a response using the control channel. (3) The base station notifies the mobile terminal station of the information of the slot for the communication channel and the carrier (frequency). (4) Communication is performed between the base station and the mobile terminal station using the designated slot and carrier for the communication channel.

[0005] Here, one of the four slots is used as a control channel, so that usually up to three mobile terminal stations can communicate simultaneously with one base station.

Now, as shown in FIG. 6, base stations BS1-B
It is assumed that S3 is installed adjacently, base stations BS4 to BS6 are installed far away, and each of the base stations BS1 to BS6 has wireless zones S1 to S6, respectively. Base station BS
In the case of PHS, the arrangement method of 1 to BS 6 is such that the radio zone of one BS is as small as several hundred meters in radius, and the number of mobile terminal stations that can be accommodated by one base station is as small as three. In steps S6 to S6, the wireless zones are arranged so as to overlap each other in order to increase the number of mobile terminal stations that can simultaneously talk.

On the other hand, since the frequency of the control channel of each base station is the same, when the base stations are arranged so that the radio zones overlap, the probability of radio wave interference increases. That is, since the frequency of the control channel is the same between the base station and the mobile terminal station (the uplink frequency and the downlink frequency are the same), for example, the uplink control channel F1 transmitted by the mobile terminal station PS1 and the base station BS2 transmit the same. When the transmission timing of the downlink control channel F2 overlaps, radio wave interference occurs, and a situation occurs in which the base station BS1 cannot receive the uplink control channel of the mobile terminal station PS1.

In order to solve this problem, a method has been adopted in which synchronization is established between base stations so that the transmission timing of the uplink control channel and the transmission timing of the downlink control channel do not overlap. In other words, when the base station rises, the downlink control channel transmitted by the neighboring base stations is monitored for a certain period of time, a timing at which interference is unlikely to be detected, and the control channel is transmitted at that timing.

[0009]

However, in the above method, in order to secure a wide wireless zone,
Generally, a base station is mounted on the roof of a building or the like. In this case, since the base station generally has a higher output than the mobile terminal station, a plurality of unsynchronized remote base stations BS4
, The downlink control channels F4 to F6 of the base station BS6 are received, so that it is impossible to determine the transmission timing of the downlink control channel where no interference occurs.

[0010] The present invention has been made in view of the above points, and an object of the present invention is to prevent interference even when wireless zones are arranged so as to overlap with each other, and to simultaneously perform wireless communication within the same wireless zone. It is an object of the present invention to provide a wireless communication control device capable of increasing the number of mobile terminal stations capable of making a call.

[0011]

According to the first aspect of the present invention,
By controlling the transmission and reception of a frame having a plurality of slots previously allocated for the communication channel and the control channel by the control unit, in a wireless communication control device that performs communication with a mobile terminal station in the wireless zone,
The control unit monitors a control channel transmitted from another wireless communication control device, controls the transmission output of its own frame based on the monitoring result, and further updates the communication channel while its own communication channel is in use. When a special communication channel is required, the control channel is changed to the communication channel.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a wireless communication control device (base station) showing an example of an embodiment of the present invention. The wireless communication control device according to the present embodiment includes a reception unit 1, a transmission unit 2, a demodulation unit 3, a modulation unit 4, an antenna 5, and a control unit 6. The receiving unit 1 receives a frame transmitted from the mobile terminal station via the antenna 5 and sends the frame to the demodulating unit 3 and receives a received signal strength RSS of the received signal.
I to the control unit 6. The transmission section 2 transmits the data modulated by the modulation section 4 through the antenna 5 in the form of a frame. The control unit 6 has a wireless vacancy detection processing function and a call slot allocation processing function.

As shown in FIG. 3, the wireless vacancy detection processing function is based on the received electric field strength RSSI of the received signal from the receiving unit 1 and the received data demodulated by the demodulating unit 3, and a peripheral wireless communication control device (base station). Search the status of the control channel in the frame to be transmitted, determine whether there is a control channel vacancy, if the transmission has been made at a constant electric field strength in all slots, and there is no control channel vacancy Repeats the wireless vacancy detection processing operation, and controls the transmission unit 2 to stop the transmission or to reduce the transmission power to a value lower than usual and transmit. If there is a free control channel, the control unit 2 controls the transmission unit 2 to start transmission of the control channel at normal power.

As shown in FIG. 4, the call slot assignment processing function determines whether or not all three of the present call slots have been assigned, and determines whether the number of call slots in use is two.
If the number is less than or equal to one, an empty communication slot is allocated. If all three communication slots are allocated, transmission of the control channel is stopped, and a slot for the control channel is allocated as a communication channel. Further, when four slots including the control channel slot are already being used as speech slots, control is performed so that assignment of speech slots is rejected.

Next, the operation of the radio communication control device (base station) of the present embodiment will be described. As shown in FIG.
BS1 to BS3 are arranged, and the base stations BS1 to BS3 have wireless zones S1 to S3, respectively. Now, the base station BS1 has three mobile terminal stations PS1 to PS3 and a transmission slot Tx1.
ＴTx3 and receiving slots Rx1 to Rx3 are in communication. It is also assumed that control channel information is transmitted and received at intervals of 20 frames using the transmission slot Tx0 and the reception slot Rx0. Here, at the time of start-up, the base station BS2 performs a wireless vacancy detection process as shown in FIG. 3 to determine whether there is a vacancy in the control channel. Now, if it is detected that the surrounding base stations are transmitting at a constant electric field strength in all slots, and it is determined that there is no free control channel, the transmission from the transmitting unit 2 is stopped and the wireless free space is detected. Continue the process.

On the other hand, if a call is originated from the mobile terminal station PS4 at the base station BS1, for example, a call slot allocation process shown in FIG. 4 is performed. That is, the base station BS
1 indicates that “current call slot = 3” during a call with the three mobile terminal stations PS1 to PS3. Tx0 and the reception slot Rx0 are allocated as slots for communication with the mobile terminal station PS4. At the same time, the base station BS2 detects the release of the control channel of the base station BS1 from the measurement of the received field strength RSSI and the received data, determines that “there is a free control channel”, and sets the control channel to the base station BS1. Transmission of the control channel is started at the timing of transmission. Thereafter, the base station BS2
Wireless zone (substantially the same as the wireless zone of base station BS1)
Then, for example, when there is a call from the mobile terminal station PS5, the base station BS2 makes a call with the mobile terminal station PS5. Thereafter, the base station BS2 can communicate with three base stations by the processing based on the flowchart shown in FIG.

Here, at the base station BS1,
For example, when the communication with the mobile terminal station PS1 in the transmission slot Tx1 and the reception slot Rx1 is completed, by switching the communication channel, the current transmission slot Tx1 is switched.
0, the mobile terminal station PS4 in the reception slot Rx0
Can be switched to the transmission slot Tx1 and the reception slot Rx1, and the transmission channel Tx0 and the reception slot Rx0 can be left free as slots for control channels. When the base station BS2 talks using the four slots and stops transmitting the control channel, the base station BS1 transmits the vacant transmission slot Tx0,
The control channel can be transmitted in the reception slot Rx0.

As described above, according to the radio communication control apparatus (base station) of the present embodiment, the control unit 6 performs the radio vacancy detection processing and the speech slot allocation processing, and based on these processing results, the interference May stop transmitting its own control channel if necessary, or if necessary,
Since the slot allocated to the control channel is allocated for communication, it is possible to simultaneously perform communication with as many mobile terminal stations as possible without causing interference.

[0019]

As described above, according to the first aspect of the present invention, the transmission and reception of a frame having a plurality of slots allocated in advance for a speech channel and a control channel are controlled by the control unit, thereby enabling radio control. In a wireless communication control device configured to perform communication with a mobile terminal station in a zone, the control unit monitors a control channel transmitted from another wireless communication control device, and based on the monitoring result, determines a frame of its own frame. While controlling the transmission power,
If a new communication channel is required while all of the own communication channels are in use, the control channel is changed to the communication channel. In addition, a wireless communication control device capable of increasing the number of mobile terminal stations that can simultaneously talk in the same wireless zone can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a wireless communication control device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an arrangement state of a radio communication control device according to the above and a communication state with a mobile terminal station.

FIG. 3 is a flowchart illustrating an operation of the wireless communication control device illustrated in FIG. 1;

FIG. 4 is a flowchart showing an operation of the wireless communication control device shown in FIG.

FIG. 5 is a diagram illustrating a frame configuration of a mobile communication system.

FIG. 6 is a schematic diagram showing a communication state according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Receiving part 2 Transmitting part 3 Demodulation part 4 Modulation part 5 Antenna 6 Control part BS1-BS6 Base station PS1-PS6 Mobile terminal station S1-S6 Wireless zone Tx0-Tx3 Transmission slot Rx0-Rx3 Reception slot

Continuation of front page (56) References JP-A-5-191336 (JP, A) JP-A-7-264659 (JP, A) JP-A-7-177567 (JP, A) JP-A-7-273722 (JP, A) , A) JP-A-60-62748 (JP, A) JP-A-59-47852 (JP, A) JP-A-56-102138 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H04Q 7/00-7/38 H04B 7/24-7/26 102

Claims (1)

(57) [Claims] 1. A wireless communication system in which communication with a mobile terminal station in a wireless zone is performed by controlling the transmission and reception of a frame having a plurality of slots previously allocated to a communication channel and a control channel by a control unit. In the communication control device, the control unit monitors a control channel transmitted from another wireless communication control device, controls transmission output of its own frame based on the monitoring result, and uses its own communication channel. The wireless communication control device according to claim 1, wherein when a new communication channel is required in the state of (1), the control channel is changed to the communication channel.