JPH01125130A - Idle channel discrimination system for cordless telephone system - Google Patents

Abstract

PURPOSE:To surely decide whether or not a control channel is idle by detecting a frame synchronizing signal included in a control signal. CONSTITUTION:When it is detected by a received electric field intensity detecting means 8 that the received electric field intensity is not over a threshold level and even when the received electric field intensity detecting means 8 detects the received electric field intensity is over a threshold level, but when no frame synchronizing signal is detected by a frame synchronizing detection means 11, a deciding means deciding that the control channel is idle, which is provided at least on one of connection device and a radio telephone set. Thus, when the frequency of an interference wave is nearly equal to the carrier frequency of a control channel, even when the received electric field intensity as to the control channel is over the threshold level through the detection, when no frame synchronizing signal is detected, it is discriminated that the control channel is in the idle state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a cordless telephone device to which a multi-channel access system is applied.

(Prior Art) FIG. 2 illustrates a schematic configuration of a cordless telephone device, in which each connection wave fl! 222-1 to 22-n and each connection wave Wt22-1
22-n and wireless telephones 23-1 to 23-m connected via wireless lines. In this cordless telephone device, a multi-channel access method is applied in which a channel of a wireless line is shared between each of the connection devices 22-1 to 22-n and each of the wireless telephones 23-1 to 23-m. For example, a wireless line consists of one control channel and multiple communication channels. When transmitting and receiving a control signal between the connecting device and the radio telephone 11, the control channel is used after confirming that the control channel is in an empty state.

Furthermore, when transmitting and receiving call signals between the connection device and the non-FJ telephone, use the free call channel while confirming that one of the call channels is free.

FIG. 3 is a block diagram showing a conventional Mla telephone.

The control unit 1 in this radio telephone switches the reception f12 and the transmission 4113 to whichever of the control channel and the idle communication channel is set to operate. In the case of a call channel, the call signal sent from the handset 4 is the transmission IO! 3 from the transmitting antenna 5, received by the connecting device, and sent out to the wired line. Further, a call signal from the wired line is transmitted from the connecting device, received by the receiver 62 via the receiving antenna 6, and applied to the receiver 7.

In the case of the control channel, the control signal sent from the control unit 1 is transmitted from the transmitting antenna 5 via the transmitting fi3,
Received by the connected device. Further, a control signal transmitted from the connecting device is received by the receiver 2 via the receiving antenna 6 and is applied to the control unit 1.

Here, in this wireless phone, the lees receiver is normally in the state, and the control section 1 operates the receiver 2 on the control channel. For reception, the demodulator 2 demodulates the reception input from the reception antenna 6 and applies it to the electric field strength detection circuit 8 which outputs an 'fi modulated output signal for the control channel. The received field strength detection circuit 8 detects whether the received field strength for the control channel is greater than or equal to a preset threshold based on the demodulated output of the receiver 2, and controls the signal indicating this detection result. Add to Part 1. When the control unit 1 receives a signal indicating that the electric field strength is not equal to or higher than the threshold value, it determines that the control channel is in an empty state.Then, when the control unit 1 attempts to transmit a control signal, If the control channel is vacant, the transmitter 3 is operated on the control channel.This allows the non-1i1 ffi phone to transmit control signals.

However, in FIG. 2, for example, contact! &Sou@22
-1 and Kumasenden i,! 1lff! If a call signal is sent and received between amget22-3 and na=wn23-3 on a call channel with carrier frequency f1, then these carrier waves are Interfering with the following equation (1) or (
A radio wave with a frequency fR as shown in 2') is generated.

2f - f2 = fR... (1) 2f2 - f1
= f, (2) If this frequency fR is approximately equal to the carrier frequency of the control channel, the inorganic telephone I! The receiver 2, which has been set to the control channel 23-2, tunes the reception power of the frequency FR from the reception antenna 6 to I. For this reason, the received electric field strength detection enclosure 8
detects that the received electric field strength is greater than or equal to a preset threshold. As a result,! 1.1170 part 1 determines that the control channel is not in an empty state, and this empty state?
! Telephone tF123-2 will no longer be able to send control signals.

(Problem to be Solved by the Invention) In this way, in the conventional cordless telephone device, when the carrier waves of multiple communication channels interfere and the frequency of this interference wave is approximately equal to the carrier wave frequency of the control channel, the interference wave There is a problem in that the S-less telephone receiving the signal determines that the control channel is not available, and is unable to transmit the control signal.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cordless telephone device that can reliably determine whether a control channel is idle.

(Structure of the Invention) (Means for Solving the Problems) The present invention provides a method for transmitting and receiving control signals between a connection device and a 4I-free telephone station using a control channel among a plurality of wireless channels. A reception electric field for detecting whether the reception electric field strength in the 1b11 channel is equal to or higher than a preset threshold in the idle channel determination method of the cordless telephone V, which determines whether or not it is in an idle state. When it is detected by the intensity detection means, the frame synchronization detection means for detecting the frame synchronization signal included in the 1lIIJn Shintan, and the received electric field strength detection means that the received electric field strength is not more than a threshold value,
and if the frame synchronization detection means does not detect a frame synchronization signal even if the reception field strength detecting means detects that the received field strength is equal to or higher than the threshold value, the control channel is in an empty state. and a determining means that determines that the connection device and the! 11'R
The present invention is characterized in that it is provided in at least one of the talking devices.

(Function) According to the present invention, when the carrier waves of each AM channel other than the control channel interfere and the frequency of this interference wave is approximately equal to the carrier wave frequency of the control channel, this causes the received electric field strength for the control channel. Even if it is detected that the frame synchronization signal is greater than or equal to the threshold value, if the frame synchronization signal is not detected, it is determined that the control channel is in an empty state.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cordless telephone device to which the present invention is applied! 15 of the 1411 phone? There is a block diagram 1 showing an example.

This embodiment is constructed by adding a frame synchronization demodulation circuit 11 to the conventional mless telephone shown in FIG. ff13. Incidentally, in FIG. 1, parts having the same functions as the conventional II-less telephone shown in FIG. Further, the radio telephone of this embodiment is used as each of the radio telephones 23-1 to 23-n in FIG.

Now, for example, the Sa telephone 23-1 shown in FIG.
Nia(t8111JIIIW 1 Ha uke(ffi2el
It is operated with 111Ul-Yannel. The reception a2 receives the reception input from the reception antenna 6 and applies the I-modulated output for the 13m channel to the reception field strength detection circuit 8 and the frame synchronization demodulation circuit 11, respectively.

Here, if the control 0@"5 is being transmitted or received by any of the other YA line telephones 1123-2 to 23-n, the received field strength detection circuit 8 of the wireless telephone 23-1 Based on the demodulated output of !2, it is detected that the received electric field strength for the control crane channel is equal to or higher than a preset threshold, and a signal indicating this is applied to the 1lJID section 1.Furthermore, the frame synchronization demodulation circuit 11 inputs the demodulated output of the receiver 2, that is, the control@bow, and applies the frame synchronization signal included in this control signal to the control unit 1.The control unit 1 applies the frame synchronization signal included in this control signal to the control unit 1. When a signal indicating that the intensity is above the threshold value and a frame synchronization signal are respectively input, it is determined that the control channel is not in an empty state.
Even if part 1 tries to transmit 1blJ III @e, the control channel is not free, so no a =
Filling machine 23-1 II! The I'W-ke state is maintained.

Next, each of the other wireless telephones 1123-2 to 23-n “
None of them is transmitting or receiving the control I@ signal, and for example, the carrier waves of the communication channels used for each ga'R telephone 23-2 and 23-3 interfere with each other, and this causes the control channel to If an interference wave with a frequency approximately equal to the carrier frequency of the wireless Ti W 1123-1
! , Oit 6 Uke 111211, 2 Fs 7
The received input of the interference wave from the antenna 6 is demodulated, and the demodulated outputs are applied to a received field strength detection circuit 8 and a frame synchronization demodulation circuit 11, respectively. Received field strength detection four-way 8
detects that the received field strength is above the threshold based on this demodulated output, and transmits a signal indicating this to 1blJID.
Add to Part 1. Further, even if the frame synchronization demodulation circuit 11 inputs the demodulated output that does not include a frame synchronization signal, it does not send out a frame synchronization@no, and the received electric field strength of the 613111 part 1 is higher than the threshold value. However, the frame synchronization signal is not input, and the control channel is therefore determined to be in an empty state. Then, when the control unit 1 attempts to transmit the control tIO signal,
Since the control channel is vacant, the transmitter 3 is operated on the control channel. As a result, this wireless telephone 23-
1 can send control wJ@tan.

Next, no other! ! If none of the telephones 1123-2 to 23-rl are transmitting or receiving control signals and no interference waves with a frequency approximately equal to the carrier frequency of the control channel are generated, the received electric field at the radio telephone 23-1 The strength detection circuit 8 detects that the received electric field strength is not above the threshold value based on the demodulated output of the receiver 4g1l12, and sends a signal q indicating this to the control unit 1. The control unit 1 determines that the control channel is vacant since this signal indicates that the received field strength is not equal to or higher than the threshold value. Thereby, when the control unit 1 wants to transmit a control signal, it can operate the transmitter 3 on the control channel.

In this way, in this embodiment, frame synchronization is performed on the demodulated output for the control channel even if the received electric field strength for the υJllll channel is not equal to or higher than the threshold value, and even if the received electric field strength for the control channel is equal to or higher than the threshold value. If no signal is included, it is determined that the control channel is in an empty state.

In this embodiment, the radio telephone is equipped with a received field strength detection circuit, a frame synchronization demodulation circuit, a control section, etc., and these are provided in the connecting device or the connecting device and the Retsu III telephone, so that the connecting device can The connecting device and the wireless telephone may determine whether the control channel is free.

〔Effect of the invention〕

As explained above, according to the present invention, since the frame synchronization signal included in the $ control (H number) is detected, the frame synchronization signal is detected even if the received electric field strength for the control channel is equal to or higher than the threshold value. It is possible to provide a cordless telephone V device that can reliably determine that a control channel is free if no signal is detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an MS telephone in a cordless telephone device to which the present invention is applied. 1...Control unit, 2...Receiver, 3...Transmission^, 4
... Transmitter, 5... Transmitting antenna, 6... Receiving antenna, 7... Receiver, 8... Reception field strength detection circuit, 11... Frame synchronization demodulation circuit, 21-1~ 21
-n: Wired line, 22-1 to 22-n: Connection device, 23-1 to 23-m: Wireless telephone.

Claims (1)

[Scope of Claims] A connection device connected to a wired line, and a wireless telephone connected to the connection device via a wireless line, wherein one of a plurality of wireless channels is transmitted between the connection device and the wireless telephone. An empty channel determination method for a cordless telephone device that determines whether or not the control channel is idle when transmitting and receiving control signals through the control channel,
Received field strength detection means for detecting whether received field strength on the control channel is equal to or higher than a preset threshold; and frame synchronization detection means for detecting a frame synchronization signal included in the control signal. If the received electric field strength detecting means detects that the received electric field strength is not equal to or higher than the threshold value, and even if the received electric field strength detection means detects that the received electric field strength is equal to or higher than the threshold value, At least one of the connecting device and the radio telephone includes determining means for determining that the control channel is free when the frame synchronization signal is not detected by the frame synchronization detecting means. An empty channel determination method for cordless telephone equipment.