Pulse or digital communications – Spread spectrum – Frequency hopping
Reexamination Certificate
2001-02-20
2004-10-12
Chin, Stephen (Department: 2634)
Pulse or digital communications
Spread spectrum
Frequency hopping
Reexamination Certificate
active
06804289
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a wireless communication system in which switching is performed among terminals or between terminals and a public line in wireless fashion, as well as to a method of controlling this system.
2. Description of the Related Art
Wireless communication is rapidly becoming more widespread and is finding use in a variety of fields. Telephone exchanges are no exception, and systems have been proposed in which communication between a main unit having a switching function and wireless telephones dedicated to the system (hereinafter referred to as wireless telephones) is performed in wireless fashion.
A wireless telephone exchange according to the prior art will now be described.
<System Architecture>
In a conventional wireless communication system, wireless transmission for low-power analog cordless telephones is employed for wireless communication between extension terminals and the main unit. Specifically, the modulation adopted is frequency modulation, two control channels and 87 voice channels can be used and the communication that is possible is 1:1 (point-to-point). In order that a wireless extension terminal may communicate with the main unit, a connecting device for the wireless extension terminal is required.
At the start of communication, first the voice channel to be used is decided by the control channel, a transition is then made to the voice channel and communication is continued using this channel.
Each component of the conventional wireless communication system and the basic operation thereof will now be described.
<Construction of Main Unit>
FIG. 34
is a block diagram showing the architecture of a conventional wireless communication system and the construction of a main unit thereof. A main unit J
1
, which is the principal component of an exchange system, accommodates a plurality of outside lines and a plurality of terminals and is adapted to switch calls among these. In order that a wireless terminal (referred to as a wireless telephone below) J
3
to which a connecting device J
2
is connected in point-to-point fashion can be accommodated in the system, the connecting device J
2
is placed under the control of the main unit J
1
and wirelessly controls the wireless terminal to establish a wireless transmission link. The wireless telephone J
3
is a terminal for communicating, via the connecting device J
2
, with an outside line accommodated in the main unit J
1
and with extensions.
The main unit J
1
accommodates a PSTN (an existing public telephone network) J
4
, which is one outside line network, a PSTN line J
5
, which is an outside line from the PSTN J
4
, and an SLT (single line telephone) J
6
, which is one terminal connected to the main unit J
1
.
The internal construction of the main unit J
1
will now be described.
As shown in
FIG. 34
, a CPU (J
101
) lies at the heart of the main unit J
1
and supervises overall control of the main unit, inclusive of control of switching. The control program of the CPU (J
101
) is stored in the ROM J
102
. A RAM (J
103
) stores various data for control of the CPU (J
101
) and provides a work area for various computations.
A communication channel unit J
104
switches calls (by time division switching) under the control of the CPU (J
101
). A PSTN line i/f (J
105
) performs PSTN line control, such as incoming call detection, selection-signal transmission and DC loop closure, under the control of the CPU (J
101
), in order to accommodate the PSTN line J
5
. An SLT i/f (J
106
) performs current feed, loop detection, selection-signal reception and call-signal transmission under the control of the CPU (J
101
) in order to accommodate the SLT (J
6
).
A telephone unit J
107
has a handset, dialing keys, a speech circuit and a display, etc., for functioning as an extension multi-function telephone under the control of the CPU (J
101
) when the supply of power to the main unit is normal, and for functioning as an SLT in the event of a power failure. A tone transmission circuit J
108
transmits various tones, such as a PB signal, dial tone and incoming call tone. A connecting device i/f (J
109
) sends and receives a voice signal and control signal to and from the connecting device J
1
under the control of the CPU (J
101
) in order to accommodate the connecting device J
2
.
<Construction of Connecting Device>
FIG. 35
is a block diagram showing the construction of the connecting device J
2
in the conventional wireless communication system. As shown in
FIG. 35
, the connecting device J
2
has a CPU (J
201
) for controlling the overall connecting device, inclusive of control of the communication channel and wireless portions. A ROM (J
202
) stores the control program of the CPU (J
201
), and an EEPROM (J
203
) stores the call code (system ID) of the system. Furthermore, a RAM (J
204
) stores various data for control of the CPU (J
201
) and provides a work area for various computations.
A main unit i/f (J
205
) sends and receives a voice signal and control signal to and from the main unit J
1
under the control of the CPU (J
201
). A PCM codec J
206
, which is under the control of the CPU (J
201
), converts a PCM-coded speech signal from the main unit i/f (J
205
) to an analog voice signal, transmits the analog voice signal to a voice processing LSI (J
207
), converts an analog voice signal from the voice processing LSI (J
207
) to a PCM code and transmits the PCM code to the main unit i/f (J
205
).
Under the control of the CPU (J
201
), the voice processing LSI (J
207
) receives a demodulated signal from a wireless unit J
208
, described below. If the received signal is control data, the voice processing LSI performs an A/D conversion and sends the converted data to the CPU (J
201
). If the received signal is a voice signal, the voice processing LSI executes processing such as descrambling and decompression and outputs the processed data to the PCM codec (J
206
). At the same time, the voice processing LSI subjects control data transmitted from the CPU (J
201
) to a D/A conversion, transmits the analog data to the wireless unit J
208
, subjects a voice signal from the PCM codec (J
206
) to scrambling such as scrambling and compression and transmits the processed signal to the wireless unit J
208
.
Under the control of the CPU (J
201
), the wireless unit J
208
executes processing in such a manner that the control data and voice signal from the voice processing LSI (J
207
) can be modulated and wirelessly transmitted, transmits the processed signals to the wireless telephone J
3
, demodulates a signal received from the wireless telephone J
3
, extracts control data and a voice signal and transmits the results to the voice processing LSI (J
207
).
<Construction of Wireless Telephone>
FIG. 36
is a block diagram showing the construction of the wireless telephone J
3
accommodated in the conventional wireless communication system. As shown in
FIG. 36
, the wireless telephone J
3
has a CPU (J
301
) for controlling the wireless telephone J
3
, inclusive of wireless control and call control. A ROM (J
302
) stores the control program of the CPU (J
301
), and an EEPROM (J
303
) stores the call code (system ID) of the system and a sub-ID of the wireless telephone J
3
. A RAM (J
304
) stores various data for control of the CPU (J
301
) and provides a work area for various computations.
A communication channel unit J
305
inputs and outputs speech signals to and from a handset J
308
, microphone J
309
and speaker J
310
under the control of the CPU (J
301
). Under the control of the CPU (J
301
), a voice processing LSI (J
306
) receives a demodulated signal from a wireless unit J
307
. If the received signal is control data, the voice processing LSI performs an A/D conversion and sends the converted data to the CPU (J
301
). If the received signal is a voice signal, the voice processing LSI executes processing such as descrambling and decompression and outputs the processed data to the communication channel unit J
305
. The voice process
Chin Stephen
Kim Kevin
Morgan & Finnegan , LLP
LandOfFree
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