Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1998-08-03
2002-12-03
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S342000, C714S758000
Reexamination Certificate
active
06490260
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to digital mobile telecommunication systems and, more particularly, to a transmitter with increased throughput of user information between a mobile telecommunication terminal and a base station.
2. Description of the Related Art
A Code Division Multiple Access (CDMA) system sets an n-bit random pattern (spread code) of “0s” and “1s” and transmits a message stream of that pattern and an inverted pattern at a bit rate n times the message bit rate. As the CDMA system transmits a message at the high bit rate, the width of the frequency spectrum is spread. Therefore, the CDMA system is sometimes referred to as a spread spectrum system.
A mobile telecommunication terminal, which is a subscriber or personal communication terminal, provides telecommunication services for the user by radio communication with a base station.
A conventional transmitter of the mobile telecommunication terminal and the base station in a typical CDMA system is illustrated in FIG.
1
. The transmitter includes a voice encoder
10
, a Cyclic Redundancy Check (CRC) encoder
12
, a tail bit inserter
14
, a Forward Error Correction (FEC) encoder
16
, an interleaver
18
, a symbol repeater
20
, and a digital modulator
22
.
In operation, voice or data information coded by voice encoder
10
is applied to CRC encoder
12
and tail bit inserter
14
. The CRC encoder
12
CRC-encodes the applied voice or data information and adds the CRC-encoded result to the voice or data information. The tail bit inserter
14
inserts tail bits (fixed value bits) into the applied voice or data information. The CRC encoder
12
and tail bit inserter
14
perform the above operations in the time unit of a frame. The CRC-encoded result and the tail bits are added to the voice or data information to detect a transmission error of a traffic channel frame upon transmitting or receiving traffic channel data in the time unit of a frame.
Referring to
FIG. 2
, the structure of a traffic channel frame in which the CRC-encoded result and the tail bits are added to the voice or data information by CRC encoder
12
and tail bit inserter
14
is shown. The traffic channel frame is comprised of I data (voice) bits corresponding to the voice information generated by voice encoder
10
, F CRC bits generated by CRC encoder
12
via a polynomial which uses the voice information bits, and T tail bits consisting of “0s”.
For example, in an IS-95 system, a traffic channel frame of 9600 bps voice data is comprised of 192 bits during a frame of 20 ms in duration. The 192 bits are employed as follows: 172 voice information bits, 12 CRC bits, and 8 tail bits. A traffic channel frame of 4800 bps voice data is comprised of 96 bits during a frame of 20 ms. The 96 bits are employed as follows: 80 voice information bits, 8 CRC bits, and 8 tail bits.
The traffic channel frame illustrated in
FIG. 2
is applied to an Radio Frequency (RF) transmitter after being processed by FEC encoder
16
, interleaver
18
, symbol repeater
20
and digital modulator
22
, and carrier-modulated.
The FEC encoder
16
is a convolutional encoder for correcting a bit error in the receiver generated during radio transmission. The interleaver
18
is a block interleaver that performs interleaving to prevent a burst error which may be generated on a mobile telecommunication radio transmission channel. The symbol repeater
20
adjusts the symbol rate of the interleaved traffic channel frame. The digital modulator
22
consists of a direct sequence (DS) spread spectrum device, a data modulator, and a digital low pass filter for increasing the efficiency of a frequency band.
Meanwhile, the receiver receives the traffic channel frame and corrects an error through a digital demodulator, a de-interleaver, and a Viterbi decoder having a FEC decoding function. The error-corrected voice information is applied to a CRC encoder which is identical to that used in the transmitter. The receiver compares CRC bits obtained by the CRC encoder with CRC bits within the received traffic channel frame. If they are equal to each other, then no errors are considered to be present in the transmitted traffic channel frame. However, if they are not equal, then an error(s) is considered to be present in the traffic channel frame.
Thus, the CRC bits are inserted into the traffic channel frame together with the voice information in order to determine whether or not there are errors in the traffic channel frame. As such, the throughput of the voice information is decreased by a number of bits equal to the number of CRC bits. For instance, in the IS-95 system of 9600 bps voice data, since there are 12 CRC bits out of the total 192 bits during the frame time of 20 ms, the throughput of the voice information decreases by 6.25 percent (i.e., 12/192×100). Similarly, in the IS-95 system of 4800 bps voice data, the throughput of the voice information decreases by 8.33 percent (i.e., 8/96×100).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a transmitter for increasing the throughput of traffic information in a mobile communication system by transmitting CRC bits through a control channel frame.
It is another object of the present invention to provide a method for increasing the throughput of traffic information in a mobile communication system by transmitting CRC bits through a control channel frame.
In one aspect of the invention, a transmitter for increasing information throughput in a digital mobile telecommunication system is provided. The transmitter includes: means for implementing error correction with respect to a traffic channel frame having user service information to generate CRC bits for the user service information of the traffic channel frame; and means for inserting the CRC bits into a control channel frame, wherein the traffic channel frame and the control channel frame having the inserted CRC bits are transmitted at a radio frequency.
In another aspect of the invention, a method for increasing information throughput in a transmitter of a digital mobile telecommunication system is provided. The method includes the steps of: implementing error correction with respect to a traffic channel frame having user service information to generate CRC bits for the user service information of the traffic channel frame; and inserting the CRC bits into a control channel frame, wherein the traffic channel frame and the control channel frame having the inserted CRC bits are transmitted at a radio frequency.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
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Dilworth & Barrese LLP
Hyun Soon-Dong
Nguyen Chau
Samsung Electronics Co,. Ltd.
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