JPH0630464B2 - Cordless telephone system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cordless telephone system for avoiding an interference phenomenon due to co-channel radio waves from a plurality of fixed devices (CE).

[Conventional technology]

In the conventional cordless telephone system, as shown in FIG. 3 (a), the fixed devices (CE) 10 and 11 and the cordless telephones (Tel) 30 and 31 are provided in each service zone 2.
It was uniquely associated with 0,21. That is, the cordless telephone usable in the service zone 20 of the fixed device 10 is the telephone 30 that is uniquely supported, and the fixed devices 10 and 11 operate independently. This was a system designed on the assumption that the distance between each fixed device is sufficiently larger than the distance between the cordless telephone and the fixed device.

When the number of users increases in this system and the fixed devices 10 and 12 are arranged close to each other as shown in FIG. 3 (b), the cordless telephone 30 causes the cordless telephone 30 to cover the service zones 20 and 22 of the fixed devices 10 and 12. In the case where the radio waves of the same frequency are emitted from both of the fixing devices 10 and 12 in the case where the cordless telephone 30 is located in the overlapping portion 40, the cordless telephone 30 receives the interference of the radio waves.

Recently, as shown in Fig. 3 (c), the number of
A cordless telephone system in which a fixed device and a cordless telephone do not have a one-to-one correspondence, that is, a system in which the cordless telephone can communicate with the service zone of any fixed device, is considered, but in the part 40 where these service zones overlap. As with the one-to-one correspondence cordless telephone system, there is a possibility of causing an interference phenomenon on the same channel.

[Problems to be solved by the invention]

In the above-mentioned conventional structure, when the number of users increases in a cordless telephone system in which the fixed device and the cordless telephone correspond one-to-one, or in the case where the cordless telephone is a cordless telephone system capable of making a call in the service zone of any fixed device, It is difficult for users to know the interference phenomenon of the same channel, and even if they know that they are receiving interference,
I couldn't avoid it.

An object of the present invention is to solve such a conventional problem, to switch a channel for sending an empty line at a fixed device (CE) side at regular time intervals, and to perform this channel switching between fixed devices which have adjacent service zones. An object of the present invention is to provide a cordless telephone system which allows a cordless telephone to acquire a channel without interference by each fixed device according to a different rule.

[Means for solving problems]

According to the configuration of the present invention, a fixed device and a plurality of cordless telephones corresponding to the fixed device are provided, and in the cordless telephone system in which each fixed device and each cordless telephone has a plurality of wireless channels, the fixed device is After sending a blank line signal for a certain period of time on a wireless channel that can accept calls from the cordless telephone, a channel scan is started from the set channel according to a predetermined rule that differs according to each fixed device, and then a new available channel is used again. The feature is that the line signal is transmitted for a certain period of time.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIGS. 1 (a) and 1 (b) are flow charts showing the operations of the cordless telephone and the fixing device according to the embodiment of the present invention.
For cordless phones, after turning on the power, first step 5
In step 1, a call request from the cordless telephone is received, and then in step 52, the channel owned by the cordless telephone is scanned and the channel in which the skyline signal is broadcast is captured (step 53). At this time, if the skyline signal is not output from any fixed device, or if the skyline signal cannot be received due to the interference phenomenon, the busy tone (Busy tone) is displayed as in step 54.
tone) is output and is maintained until the hook of the telephone is turned on in step 55, and the process returns to step 51 by the hook-on in step 56. On the other hand, if there is a skyline signal, in step 57, a call signal including the fixed device identification number and self identification number of the other party is transmitted to make a call (step 58), and after the call is completed, the call goes on hook (step 5).
9) and returns to step 51.

Here, as shown in FIG. 3C, the cordless telephone 33
However, when a call is made at a point 41 where the service zones 20, 21, 22, 23 of the fixed devices 10, 11, 12, 13 overlap each other, even if the skyline signals of the fixed devices 10, 11 have the same frequency. If the fixed devices 12 and 13 are broadcasting the skyline signals at different frequencies, the working device 33 will be
Either one of the 13 broadcast skyline signals can be captured. However, if both the fixed devices 12 and 13 are in the call service, the fixed devices 10 and 11 interfere with each other, so that the telephone 33 cannot capture the skyline signal.

In this way, an interference phenomenon may occur when two or more fixed devices with overlapping service zones are transmitting skyline signals at the same frequency. However, if the telephone side does not send a calling signal, the fixed device side Since the calling signal cannot be received, the skyline signal is first transmitted in step 61 according to the flow chart of FIG. 1 (b). In step 62, the reception of the skyline signal is checked, and if the call signal cannot be received for 30 seconds (step 64), the skyline signal is stopped (step 70) to avoid the interference as described above. In order to do so, go to step 65. In this step 65, a value according to the rule unique to each fixed device is set in the scan start channel.

This rule means that, for example, a random value is selected from the channels assigned to the system, and the channel used at this time may be continuously selected, but this is also possible. It means any form such as adding a positive or negative integer in a predetermined range to the number of channels used previously.

Further, in step 66, the channel assigned to the system is scanned from the set scan start channel, and if an unused channel is found in step 67, a blank signal is broadcast again on that channel.

When the call signal can be received, line connection is performed as in step 63 to make a call (step 68) and the call is completed by the on-hook in step 69.

In the present embodiment, the case where the received electric field is checked is shown as an example of the method of detecting an unused empty channel.

FIG. 4 shows an example of a block diagram of the fixing device used in this embodiment. In this fixing device, the electric field received by the antenna 3 is received by the receiving device 6 and checked by the control device 4,
If the magnitude of the value is a certain value or more, it indicates that the channel is in use, while if the received electric field is less than the certain value, the channel is not used in the service area of the fixed device, It is an empty channel.

The unique rule in step 55 is that, when fixed devices 10, 11, 12, 13, and 14 of adjacent devices are adjacent to each other and their service zones 20 to 24 overlap, as in the case of fixed devices 10, 11, 12, 13, and 14 in FIG. The fixed device employs channel scanning with different rules.

For example, the rule adopted by the fixed device 10 is the operation "add m" and the rule adopted by the fixed device 11 is the operation "subtract m". At this time, m is m ≧ 1
, And the fixing devices 10 and 11 select any one from the parameter range of ± m. By doing so, even if the fixed devices 10 and 11 broadcast the skyline signal to the same channel n in step 61, and therefore the cordless telephone 33 located in the portion 42 where the service zones are overlapped is interfered with. , 30 seconds later, the fixing device 10 is n + m
Since the fixed device 11 starts channel scanning from the n-m channel from the respective channels, both fixed devices do not broadcast the skyline signal again on exactly the same channel, and the probability that it will occur, if any Is so low that the cordless telephone 33 can pick up a channel without interference.

When the cordless telephone thus seizes the interference-free channel and receives the skyline signal from the fixed device, it sends a call signal as in step 57. At this time, since the calling signal includes the identification number of the fixed device and the identification number of the cordless telephone, which were included in the blank signal,
If this number is received by the fixed device side, the telephone line 9 and the cordless telephone are connected as in step 63 to provide the call service.

[Effects of the Invention] As described above, according to the present invention, the cordless telephone can capture the channel without interference only by switching the channel for broadcasting the skyline signal by the fixed device at regular intervals. For this reason, a channel utilization rate can be increased, a system with a small fixed device interval can be adopted, call loss can be reduced, and as a result, the system subscriber capacity can be increased.

Further, since the interference avoidance operation is all performed by the fixed device side, the cordless telephone side does not have to have a function related to this operation, and the cordless telephone can be reduced in size and weight and the cost thereof can be reduced. A cordless telephone system capable of servicing a plurality of cordless telephones for one device can be constructed at low cost, and the spread of services is expanded.

[Brief description of drawings]

1 (a) and 1 (b) are flow charts showing the operation of the cordless telephone and the fixing device according to the embodiment of the present invention, and FIG. 2 is a block diagram of an example of the fixing device used in the embodiment, and FIG. FIGS. 3 (a) and 3 (b) are block diagrams for explaining a cordless telephone system in which a conventional cordless telephone and a fixed device correspond one-to-one, and FIGS. 3 (c) and 3 (d) show a cordless telephone and each fixed device. It is a block diagram explaining the system which can talk between. 1 ... connection part, 2 ... transmitter, 3 ... antenna, 4 ...
Control device, 5 ... Synthesizer, 6 ... Receiver, 7 ...
Shared device, 8 ... Received electric field information transmission signal line, 9 ... Telephone line, 10, 11-14 ... Fixed device, 20-24 ... Service zone, 30-39 ... Cordless telephone, 40
~ 42 …… The overlapping part of the service zone.

Claims (1)

[Claims] 1. A cordless telephone system in which a fixed device and a plurality of cordless telephones corresponding to the fixed device are provided, and each of these fixed devices and each cordless telephone has a plurality of wireless channels, the fixed device is A wireless channel that can accept calls from cordless telephones sends a blank line signal for a certain period of time, then starts channel scanning from the set channel according to a predetermined rule that differs depending on each fixed device, and then reopens a blank line on a new acceptable channel. A cordless telephone system characterized by transmitting signals for a certain period of time.