JPH0530028A - Idle channel detection system - Google Patents

Abstract

PURPOSE:To minimize deterioration in the communication quality by holding the state synchronized so far even when burst synchronization is unlocked tentatively due to fading or the like so as to restore the burst. CONSTITUTION:A master station stores a data of an idle channel to an idle channel table 4 for a time not communicated by using devices 1-3. The table 4 is always revised. When a received control signal requests an idle channel for its speech channel, a channel instructing device 12 references the table 4 to scan an idle channel thereby seeking the idle channel. When the idle channel is found out, the information is informed to the slave station to establish the speech channel. Furthermore, the slave station similarly seeks an idle channel and so long as the notice of the information of the idle channel does not comes, the slave station seeks the idle channel. The base station and the slave station refers to the table 4 in opposite directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for searching a free channel at high speed and with high accuracy in a device which communicates using the bidirectional time division multiplexing (TDMA) at the same frequency.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, when a decoder output requests a free channel, a free channel detector sequentially switches the channels received by a receiver and determines whether or not the free channel is available. Then, when a free channel was found, it was used for communication. Thus, the free channel was searched only for the base station, and only when requested. In the slave station, the base station switches to the designated channel for communication.

In FIG. 4, 1 is an antenna, 2 is a TDMA receiver, 3 is a TDMA decoder, 6 is a TDMA multiplexer, and 7 is T.
DMA modulator, 8 TDMA transmitter, 10 decoding output,
11 is a transmission signal input, 13 is an empty channel detector, 14
Is a channel designator.

[0004]

According to the conventional method, the base station searches for an empty channel only. Therefore, it takes time to search, and even if the base station has an empty channel, the slave station has a strong interference. There was also a problem that the free channel had to be searched again.

The present invention aims to eliminate such drawbacks.

[0006]

According to the present invention, a free channel is searched for when the base station and the slave station are not talking, and the information is stored. When a free channel is needed for a call, a free channel is searched for based on the free channel information stored in the base station and the slave station. At this time, the search order is reversed between the base station and the slave station. For example, the base station searches for a low frequency channel, and the slave station searches for a high frequency channel.

[0007]

According to the control signal received by the controller, each of the base station and the slave station searches for a vacant channel and stores the data when not in a call. When a call channel is needed, a free channel is searched according to the data stored in both the base station and the slave station. When there is no free channel in this stored channel, a channel not included in the data is searched.

The person who finds an empty channel at the end of the slave station or base station transfers the information to the other party.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a first embodiment device of the present invention. In FIG. 1, the same reference numerals as in FIG. 4 denote the same, 4 is an empty channel table, 5 and 9 are controllers, 1
2 is a channel indicator. In the base station, the data of channels that are vacant when the telephone call is not made by the devices 1 to 3 is stored in the vacant channel table 4. This table is constantly updated.

When the received control signal requests an empty channel for the communication channel, the channel indicator 12 scans the empty channel with reference to the above table and searches for an empty channel. When it finds it, it informs the slave station of the information and establishes a communication channel.

Similarly, the slave station also searches for a free channel and searches for a free channel unless the base station reports the information about the free channel. Here, the directions of referring to the table are reversed between the base station and the slave station.

FIG. 2 is a flowchart showing a part of the empty channel detection method of the present invention. When a free channel is searched for and found, the information is written in the table. Check if there is a request for a call channel when necessary. When this request is received, the free channel is scanned while referring to the free channel table. When a free channel is found, the information is transferred to the base station.

Although not shown in this flow chart, when the base station reports the information of the empty channel, an interrupt occurs and the empty channel search is stopped. Also, when there is no free channel even when the entire table is scanned, the channels not written in the table are searched.

FIG. 3 shows a flowchart for searching for an available channel in the slave station. The slave station also searches for an empty channel as in the base station.

[0015]

As described above, according to the present invention,
Even if the burst synchronization is temporarily lost due to fading, etc., the state that was synchronized until then is retained and the burst is decoded, so that the received signal can be recovered and decoded at the same time as long as the burst position does not change. Can be minimized.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart of empty channel detection according to the present invention.

FIG. 3 is a flowchart of idle channel detection in a slave station.

FIG. 4 is a block diagram of a system adopting a conventional empty channel search method.

[Explanation of symbols]

1 antenna 2 TDMA receiver 3 TDMA decoder 4 Free channel table 5 Base station controller 6 TDMA multiplexer 7 TDMA modulator 8 TDMA transmitter 9 Slave station controller 10 Decode output 11 Transmission signal input 13 Base Station Conventional Controller 14 Conventional controller of slave station

Claims (2)

[Claims] 1. A method of searching for an empty channel for performing bidirectional communication between wireless communication devices that perform time-division communication at the same frequency, wherein a slave station has a means for receiving at an antenna and a receiver. The received signal is time-division multiplexed, and a TDMA decoding unit that decodes the signal to decode a control signal when not in a call, and a signal necessary for a call and a control signal when necessary, and the decoding It is shown that means for judging an empty channel whose reception level is less than a specified value from a signal, means for recording the empty channel when the judgment result is an empty channel, and output of the TDMA decoding means for searching for an empty channel. When the signal is a signal, a method for scanning the vacant channel by referring to the vacant channel recording result and searching for the vacant channel in a predetermined order; Means for transmitting the information to the base station, and the base station, like the slave station, stores the information of the vacant channel when the call is not being performed and the slave station when the call is required. And a means for searching for a free channel by scanning in the reverse order of the search by the slave station, and a means for allocating a speech channel when the free channel is found ahead of the slave station or base station. Free channel detection method. 2. The idle channel detection method according to claim 1, wherein one of the child station and the base station, which has found the idle channel first, notifies the other of the idle channel information, and then the notified station is A free channel detection method characterized by confirming that the channel is a free channel.