JPH0681097B2 - Empty channel detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a distributed control type MCA (Multi Channel Acces
s) The present invention relates to a method for detecting an empty channel at the start of transmission in a wireless communication system.

[Conventional technology]

The MCA wireless communication system enables communication between a large number of wireless devices at the same time by using a large number of frequency channels assigned in a predetermined frequency band, as is found in a so-called personal wireless device.

As a means for that, a call control channel is provided in addition to the communication channel. For example, in the case of personal wireless communication, for example, a personal call for communication with a specific station or a communication with an unspecified station is provided. The transmission of the CQ call is inevitably sent on the call control channel, and the side waiting for the communication naturally enters the standby state of the call control channel when the power of the communication device is turned on.

In personal communication in which communication is desired only with specific parties, the same identification signal consisting of a predetermined five-digit number (group number in personal radio) is set between two stations or set in the same group, and both stations are set. Only when the identification signals match, the communication can be started. In addition, CQ for calling unspecified stations
Any station can answer the call.

Before that, to start sending a call, first set the identification signal in the communication device or read it from the memory and set it, and then press the send button, the communication device will first set a new empty channel for communication. If a channel that is not communicating is found, the channel is stored as a scheduled communication channel, sent to the call control channel together with the identification signal, and when the partner station responds, the designated channel is entered and communication is continued for 5 minutes. Up to 5 minutes have passed, the transmission is stopped and the stand-by reception state is automatically set. Since the purpose of this is to digest the communication of as many stations as possible on a limited channel, the time limit is appropriately determined according to the use and congestion degree of the MCA communication system.

In the above-mentioned empty channel search, channels are sequentially received by channel scanning, and the channels that have detected signals pass one after another, and signals above a threshold value (for example, 1 μV of input electric field strength conversion) are not detected for several seconds. In this case, the channel is determined to be empty, the channel number is stored, and the call identification channel is transmitted. At that time, if the empty channel determination time is short, there is a possibility that the communication suspension period is erroneously determined to be an empty channel, and if it is long, there is a problem that it takes too long to detect an empty channel.

Therefore, as a method to shorten the time of empty channel detection,
Search all channels from time to time in standby mode to create a table of empty channel numbers, and at the start of transmission, search only the channels with the numbers listed in the empty channel table, thereby randomly selecting all channels. A method that can detect an empty channel more quickly and surely than searching is also considered.

[Problems to be Solved by the Invention]

In the empty channel detection at the start of transmission in the MCA wireless communication system by the distributed control method, it takes time in the conventional random search method when there are few empty channels, and in the idle channel table creation method in the standby mode. On the other hand, the time for detecting empty channels can be shortened surely,
Since the call channel is left during the search period, even if a call is received from another station during the search period, the opportunity for response may be missed.

This is a common problem for both personal calls and CQ calls, so a better solution is being sought.

[Means for Solving the Problems]

According to the present invention, instead of searching for an empty channel during standby, the designated communication channel numbers included in all call transmissions received by the call control channel are registered in the memory bank for the transmission time limit. , There is a high possibility that the channel with the registered number is in use (because there is a possibility that communication has ended within the time limit and it is an empty channel), and conversely, the unregistered channel is considered as an empty channel. Therefore, if the registered channels are excluded and an empty channel search is performed, an empty channel can be detected immediately. Further, in practice, it is possible to omit the detection by setting an unregistered channel as an empty channel.

If all channels are registered as being in use, empty channels will be searched from the registered channels due to the end of communication, but in that case, the probability of empty channel detection is to search in the order of oldest registration. It is expensive. Also, only when all channels are registered for use in this way, an empty channel search is performed, and when an empty channel is detected, it is stored and used for transmission start, and it is confirmed that the channel has been designated by another station. If you do this, you can register it in the channel you are using and search for another empty channel.
The in-use channel can be set for the shortest time at that time.

Specific means for applying the present invention will be described in detail in the following embodiments.

〔Example〕

The details of the configuration and operation of the embodiment of the present invention will be described below.

The first requirement of the configuration of the present invention is to register the designated communication channel number included in the identification signal sent in the paging control channel in the memory bank to create the busy channel table. If the identification number of the ringing signal sensed in the stand-by reception state matches with the own station, the designated communication channel number in the identification signal is also read, and after the response, the designated channel is switched to for communication. ,
Even if the identification number does not match with the own station, only the communication designated channel number is read and sequentially registered in the memory bank to make the channel table in use.
entral Processing Unit) operation flowchart is the first
As shown in the figure.

The second requirement is temporal processing of the created busy channel table. In the MCA wireless communication system, the time limit for one communication on the communication channel is fixed, and it is automatically cut off when the time expires, so after the time limit has passed, work to delete from the channel table being used as an empty channel Is. As an example, the case of an MCA wireless communication system using a distributed control method with a call limit time of 3 minutes is explained. A 4-bit shift counter for call channels that can be used in the system is secured in the CPU data memory, and the counter initial value is φφφφ. .

When an identification signal other than the own station is received during standby, "1" is set to the 3rd bit of the shift counter corresponding to the designated communication channel number in the identification signal.

The secured shift counter is shifted to the right every one minute (there is no need to limit to one minute, but it is meaningless to subdivide it too much).

Due to the above, the counter is "φφφφ" after 3 minutes.
It returns to the initial value of and is sequentially deleted from the used channel table. The CPU flow chart for that purpose is as shown in FIG.

The third requirement is a procedure for incorporating an empty channel to be used for a call in an identification signal when transmitting a call. Press the PTT (Push To Talk) switch of the communication device to start sending the call, or
When the transmission switch of equivalent operation is turned on, empty channels are checked with a threshold value of 1 μV of input electric field strength for channels not registered in the used channel table as shown in the flowchart of FIG. The probability of an empty channel is extremely high except in a special case where registration is missed due to a change in distance or distance, but if a signal is detected, the next unregistered channel is detected as an empty channel. Further, when all the call channels are registered as being in communication, it is rational to detect the empty channels in the order of oldest registration.

As described above, when an empty channel is detected, the channel number is incorporated into the identification signal and the call transmission is started, as in the conventional method.

For comparison, FIG. 4 shows a flowchart for detecting an empty channel in the conventional method.

〔The invention's effect〕

According to the empty channel detection method of the present invention, an empty channel is first detected by excluding the in-use channel, and moreover, the channel should be an empty channel except in special cases. The channel can be detected and the detection time is extremely short.

Even if all channels are registered in the used channel table, the detection time can be expected to be stochastically shortened by sequentially detecting empty channels from the oldest registered channel number.

In the above method, there is no possibility of leaving the calling channel from time to time unlike the method of searching all channels during standby of the conventional method and creating an empty channel table.
There is no need to worry about missed call transmissions to your station.

In order to implement the method of the present invention, it is sufficient to secure a data memory for storing numbers for all communication channels and a shift counter for monitoring a time limit in the conventional system configuration. It has the advantage that it can be easily adapted to all communication devices and the desired effect can be obtained.

[Brief description of drawings]

FIG. 1 is a flowchart of [creation of used channel table] for operation of CPU to execute the present invention. FIG. 2 is a flow chart of the same [used channel timer process]. FIG. 3 is a flow chart of [empty channel detection]. FIG. 4 is an example of a flowchart of [Detection of empty channel in conventional system].

Claims (1)

[Claims] 1. In a communication method for detecting and designating an empty channel as a communication channel, a call control channel is received and a communication designated channel number included in an identification signal is registered in a memory bank for a transmission time limit. The registered channel number lowers the importance of registration at every predetermined time and cancels the registration after the transmission time limit elapses, and means for performing an empty channel search by excluding the registered channel, A method for detecting an empty channel, comprising means for searching up to the channel number of a memory bank whose registration importance is lowered by the memory management means if no empty channel is detected by searching.