Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-06-02
2001-07-10
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S528000
Reexamination Certificate
active
06259710
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of wireless telecommunication. More specifically, the present invention relates to the digital enhanced cordless telecommunications (DECT) system.
BACKGROUND ART
Within the field of wireless telecommunications systems there exists a system referred to as the digital enhanced cordless telecommunications (DECT) system. Within the DECT system, a user of a cordless portable telephone handset is able to communicate with a user of another telecommunication device by way of a fixed base station utilizing wireless communication. To enable the cordless telephone handset and the base station to communicate within the DECT system, a radio interface is utilized.
Within the radio interface of the DECT system, there are two communication channels utilized during communication between a cordless telephone and a base station. One of the channels is commonly referred to as the slow C-plane and is used for transmitting control data at a maximum rate of 2 kilobits per second (kBit/s). This control data enable the communication devices to remain synchronized, among other things. The other channel is typically referred to as the U-plane and is used for transmitting user data, which can include either voice data produced by a user of a cordless telephone or digital data generated, for example, by a modem of a computer system. The voice data is transmitted through the U-plane at a rate of 32 kBit/s while the digital data is transmitted through at a rate of up to 80 kBit/s. It should be appreciated that the user data (U-plane data) and the control data (slow C-plane data) can be concurrently transmitted between a base station and a cordless telephone within the DECT system.
There are some situations (e.g., during the initial setup of a call) where the need arises to transfer control data at a faster data rate than is possible through the slow C-plane. As such, the DECT standard additionally defines a fast C-plane transmission mode which enables the transmission of control data at a data rate of either 25.6 kBit/s or 64 kBit/s. The fast C-plane transmission mode, as defined by the DECT standard, involves the U-plane and fast C-plane sharing the same field within the communication frames of the system. As such, during transmission of control data through the fast C-plane, user data cannot be transmitted through the U-plane. In other words, fast C-plane data and U-plane data cannot be transmitted concurrently. A typical prior art circuit for implementing and controlling the transmission of fast C-plane data and U-plane data is discussed below with reference to FIG.
1
.
FIG. 1
is a block diagram of a prior art switching circuit
100
conventionally used within a cordless telephone of the DECT system for transmission of user data
102
through the U-plane and of control data
104
through the fast C-plane. As described above, user data (U-plane data)
102
and control data (fast C-plane data)
104
are not simultaneously transmitted. As such, switching circuit
100
is implemented to transmit either user data
102
or control data
104
. Furthermore, switching circuit
100
is implemented to grant transmission priority to control data
104
. For instance, when switching circuit
100
is transmitting user data
102
and it receives control data
104
, the transmission of user data
102
is suspended in order to begin transmission of control data
104
. Additionally, the transmission of user data
102
remains suspended until the transmission of the control data
104
is completed. The detailed manner in which switching circuit
100
operates is described below.
Switching circuit
100
of
FIG. 1
is able to receive both user data
102
and control data
104
. The received user data
102
are stored within a U-plane first-in first-out (FIFO) buffer memory
106
, while the received control data
104
are stored within a C-plane FIFO buffer memory
108
. An E/U-multiplexer (Mux)
112
, as defined within the DECT standard, receives both the user data
102
output from U-plane buffer
106
and the control data
104
output from C-plane buffer
108
. It should be appreciated that the function of E/U-Mux
112
is to transfer either the user data
102
or the control data
104
into a DECT channel buffer
114
. C-plane buffer
108
controls the operation of E/U-Mux
112
by asserting or de-asserting a signal
110
. For instance, upon receiving control data
104
, C-plane buffer
108
asserts signal
110
, causing E/U-Mux
112
to transfer control data
104
into DECT channel buffer
114
. Conversely, if there are no control data
104
within C-plane buffer
108
, it de-asserts signal
110
, causing E/U-Mux
112
to transfer user data
102
into DECT channel buffer
114
. In this manner, transmission priority is granted to control data
104
.
The function of DECT channel buffer
114
of
FIG. 1
is to encode whichever it receives of the user data
102
or the control data
104
to be transmitted in a time division multiple access (TDMA) format. Then DECT channel buffer
114
either outputs user data
102
through the U-plane as an air channel data stream
116
. Or DECT channel buffer
114
outputs control data
104
in the fast C-plane transmission mode as an air channel data stream
116
.
There is a disadvantage associated with the prior art fast C-plane transmission mode described above with reference to switching circuit
100
of FIG.
1
. The disadvantage occurs during voice connections wherein the fast C-plane transmission mode noticeably degrades the quality of the voice signals of a user of a cordless telephone within the DECT system. This degradation in voice signal quality is caused by the suspension of the transmission of U-plane voice data in order to transmit fast C-plane data. Consequently, this results in a gap within the voice signal data stream.
Thus, what is desired is a system which enables the fast C-plane transmission mode to be utilized during cordless telephone voice connections within the DECT system without degrading or disturbing the quality of the voice signals. The present invention provides this advantage.
DISCLOSURE OF THE INVENTION
The present invention includes a system that enables fast C-plane transmission mode during cordless telephone voice connections within the digital enhanced cordless telecommunications (DECT) system without degrading the voice quality. In order to perform this fast C-plane transmission mode during voice connections, one embodiment of the present invention, located within a cordless telephone handset, utilizes a silence detector circuit to determine the periods of silence within the voice data transmitted through the U-plane. By determining the periods of silence within the U-plane voice data, the present invention is able to direct the control data to be transmitted through the fast C-plane during the periods of silence. As such, the control data are able to be transmitted within the fast C-plane transmission mode without degrading or disturbing the quality of the voice data transmitted through the U-plane. Therefore, the present invention improves the fast C-plane transmission mode during cordless telephone voice connections within the DECT system.
Specifically, one embodiment of the present invention is a fast C-plane transmission mode switching circuit utilized within a cordless telephone handset of a DECT system. The switching circuit includes a first buffer device that is coupled to receive and store control data utilized within the DECT system. Furthermore, the switching circuit includes a second buffer device that is coupled to receive and store user data which is also utilized within the DECT system. A multiplexer circuit is coupled to the outputs of the first and second buffer devices in order to output the control data or the user data. A silence detector circuit is also coupled to receive the user data, and it generates an output signal when a period of silence is detected within the user data. The output signal from the silence detector circuit controls whether the multiplexer circuit o
Kizou Hassan
Tran Thien
VLSI Technology Inc.
Wagner , Murabito & Hao LLP
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