Telecommunications – Radiotelephone system – Including private cordless extension system
Utility Patent
1994-06-24
2001-01-02
Trost, William G. (Department: 2744)
Telecommunications
Radiotelephone system
Including private cordless extension system
C455S403000, C455S518000, C455S574000
Utility Patent
active
06169905
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to a cordless telephone apparatus and a control method thereof and, more particularly, to a digital cordless telephone apparatus in which a telephone communication is made among master stations and remote stations and a control method thereof.
2. Background of the Invention
A digital cordless telephone apparatus is arranged as shown in
FIG. 1
of the accompanying drawings. As shown in
FIG. 1
, a master station
1
serving as a base station is connected to a telephone line network (not shown) and includes an antenna la to make a telephone communication between it and a remote station. As shown in
FIG. 1
, there are prepared a plurality of remote stations, i.e., three remote stations
4
,
5
and
6
which can make a call among them and the master station
1
. The remote stations
4
,
5
and
6
include antennas
4
a,
5
a
and
6
a,
and a radio transmission is made possible among the antenna
1
a
of the master station
1
and the antennas
4
a,
5
a,
6
a
of the remote stations
4
,
5
,
6
.
When the user (telephone subscriber) makes a telephone call between each of the remote stations
4
,
5
and
6
and the master station
1
or the caller connected to the master station
1
through the telephone line network (not shown), the remote station transmits a connection control signal of a predetermined format to the master station
1
side and also transmits audio data that was converted into digital data in a time division manner between it and the master station
1
to make a telephone call.
Digital cordless telephone apparatus employ the TDD system (time-division double system) or TDMA/TDD system (time-division multiplexing access/time-division double system) in which a transmitted signal and a received signal are the same in frequency and a transmission is carried out in a so-called ping-pong fashion.
In the case of the TDD system, as shown in
FIG. 2A
, one channel or one frequency is divided into a transmission slot T and a reception slot R from a time standpoint. The transmission slot T and the reception slot R are alternately repeated and a guard time (not shown) is provided between the transmission slot T and the reception slot R. Each of a duration of the slots T and R is set to be 1 millisecond and the guard time is set to be several 10s of microseconds. Portable telephones (remote stations) use the transmission slot T to communicate with the base station (master station) and the reception slot R to receive a signal from the base station.
In the case of the TDMA/TDD system, as shown in
FIG. 2B
, when a call is made between one remote station and the master station, the transmission slot T and the reception slot R provided within one channel are used only one time per several cycles and other transmission slots T and reception slots R provided within the same channel are used to make a call between other remote station and the master station. The TDMA/TDD system multiplexes the transmission and reception in order to make a communication among a plurality of communication apparatus with one channel.
Since the transmission and the reception are multiplexed as described above, it is possible to effectively use frequency bands prepared for the cordless telephones. When a telephone communication is made as described above, the control signal is transmitted from the master station to each remote station at every predetermined cycle in accordance with a predetermined format. As shown in
FIG. 3A
, for example, a control signal d
1
is transmitted from the master station to the remote station at every 125 milliseconds during 625 microseconds. When any one of remote stations is accessed by the master station through some suitable means, such as an extension call or the like, the master station accesses the target remote station by transmitting an identification No. of the target remote station to the target remote station by means of the control signal Id. When each remote station is placed in the mode (referred to simply hereinafter as “reception standby mode”) so as to be accessed by the control signal from the master station, if the reception unit of the remote station is intermittently energized so as to receive only the control signal at a predetermined cycle, e.g., once per 1.5 seconds as shown in
FIG. 3B
, then a power consumption required when the remote station is in the reception standby mode can be reduced. Fundamentally, the remote station continues receiving each control signal during 625 microseconds. However, in actual practice, considering an actuation time required when the reception unit is actuated, the reception unit of the remote station is controlled so as to receive one control signal during about 10 milliseconds per access. Assuming now that the reception unit is energized to receive one control signal during 10 milliseconds at every 1.5 seconds, for example, then a period of time in which the reception unit is operated becomes about 0.67% and therefore the power consumption can be reduced considerably as compared with that required when the reception unit continues receiving the control signal.
As the system arrangement of such digital cordless telephone apparatus, there is known such one that includes a plurality of master stations as shown in FIG.
4
. As shown in
FIG. 4
, cordless telephone master stations
1
,
2
and
3
are connected to telephone line networks (not shown) separately and include antennas
1
a,
2
a
and
3
a
to make a call among them and remote stations. Remote stations
4
,
5
,
6
,
7
,
8
, . . . are prepared to communicate with the master stations
1
,
2
and
3
. The remote stations
4
,
5
, . . . , can communicate with any of the master stations
1
,
2
and
3
via radio waves to make a call through any one of the master stations
1
,
2
and
3
. With this arrangement, each of the remote stations
4
,
5
, . . . , can make an outgoing call via any one of the master stations
1
,
2
and
3
. Also, each of the remote stations
4
,
5
, . . . , can answer an incoming call when any one of the master stations
1
,
2
and
3
receives the incoming call, thereby the digital cordless telephone apparatus being widely used as a cordless telephone.
Insofar as the remote station can make a call between it and a plurality of master stations, each remote station should receive control signals transmitted from all master stations in its reception standby mode so that the remote station cannot receive the control signal at a predetermined interval in the above-mentioned reception standby mode. Thus, it is impossible to reduce the power consumed required when the remote station is set in the reception standby mode. Specifically, there is the possibility that each of the remote stations
4
,
5
, . . . , will be accessed by all control signals transmitted from all master stations
1
,
2
and
3
. Therefore, each remote station should receive all control signals, such as a control signal transmitted from the first master station
1
, a control signal transmitted from the second master station
2
and a control signal transmitted from the third master station
3
. The master stations
1
,
2
and
3
transmit the control signals cyclically but the control signals transmitted from the three master stations
1
,
2
and
3
are perfectly different from one another. Consequently, a time required when the reception unit of each of the remote stations
4
,
5
, . . . is energized must be extended considerably such that the remote stations
4
,
5
, can receive the control signal transmitted from any master station in their reception standby modes.
Alternatively, if timings at which the control signals are transmitted from all the master stations
1
,
2
and
3
, then it is possible to energize the reception unit of each of the remote stations
4
,
5
, . . . , during a period of each of the detected transmission timings. In this case, however, as compared with the case that the reception unit of each remote station is energized at the timing of the control signal t
Limbach & Limbach L.L.P.
Sony Corporation
Trost William G.
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