Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1998-11-19
2001-09-18
Baker, Stephen M. (Department: 2784)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S795000
Reexamination Certificate
active
06292920
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to transmission rate judgment methods and their apparatuses.
2. Description of the Related Art
Recently, with drastically growing demands for terrestrial mobile communications such as car telephones and portable telephones, great importance is attached to a technology to allow effective utilization of frequencies to secure capacities for as many subscribers as possible with limited frequency bands. As one of multiple access systems for effective utilization of frequencies, the code division multiple access (CDMA) system is attracting attention. The CDMA system is a multiple access system that utilizes a spread spectrum communication technology, capable of achieving the excellent communication quality through its wideband and sharp correlation characteristics using pseudo noise (PN) series, etc. Terrestrial mobile communication systems using the CDMA system are described, for example, in U.S. Pat. No. 4,901,307.
A mobile communication system using the CDMA system can increase its system capacity by introducing variable rate transmission. For example, in variable rate voice CODEC, the data rate changes in units of a 20 msec section, called “frame” in accordance with the voice activity. Transmitting only the amount of information necessary to send the corresponding voice signal in each frame makes it possible to reduce interference to other users and increase the system capacity as well.
On the transmitting side, after voice coding, the system adds a CRC bit to check the frame quality, for example, and performs convolutional coding. The convolutional-coded data are repeated according to the data rate and have frames of the same length irrespective of the data rate. After being subjected to processing such as block interleave, spreading and modulation, the data are transmitted.
Then, a conventional transmission rate judgment apparatus is explained with reference to drawings.
FIG. 1
is a block configuration diagram of a conventional transmission rate judgment apparatus.
In
FIG. 1
, the conventional transmission rate judgment apparatus judges a transmission rate using variable rate decoding section
501
. This variable rate decoding section
501
comprises derepeating section
502
that combines or adds repeated symbols in accordance with the rate to be demodulated, Viterbi decoding section
503
that performs Viterbi decoding on the output symbol of derepeating section
502
and outputs decoded data, and CRC checking section
504
that performs a CRC check on the Viterbi-decoded data. It also comprises convolutional coding section
505
that performs convolutional coding on the output of Viterbi decoding section
503
and symbol error number counting section
506
that calculates the number of symbol errors in a frame using the output of derepeating section
502
and the output of convolutional coding means
505
. It further comprises rate judgment section
507
that judges the rate based on the CRC check result and the reliability and the number of symbol errors of Viterbi decoding.
The sections from derepeating section
502
to symbol error number counting section
506
can perform processing according to multiple anticipated data rates, for example, full rate, ½ rate, ¼ rate and ⅛ rate. Since the data rate varies from one frame to another, the system performs this processing for all rates or some rates, and estimates and judges the transmission rate.
Then, the rate judgment procedure is explained with reference to FIG.
2
and FIG.
3
.
FIG. 2
is a flow diagram showing the procedure for decoding a received symbol and judging the rate. As shown in
FIG. 2
, after performing the respective processing from derepeating section
502
to symbol error number counting section
506
for all anticipated rates (step
601
), the system makes a judgment according to the result (step
602
). In step
602
, this method makes a judgment using the quality information of all rates, that is, the CRC check results, Viterbi decoding reliability and number of symbol errors of all rates.
FIG. 3
is a flow diagram showing the procedure for judging the rate through decoding of each rate and quality judgment. As shown in
FIG. 3
, the system carries out processing from derepeating section
502
to symbol error number counting section
506
sequentially starting from a specific rate and makes a judgment in the process. In step
701
, it carries out processing from derepeating section
502
to symbol error number counting section
506
for the rate with the largest quantity of information (full rate), and in step
702
it makes a judgment based on the quality information of the full rate. If the judgment result is acceptable, the system judges it as a full rate (step
710
) and the process ends here. If the judgment result is not acceptable, the system carries out processing from derepeating section
502
to symbol error number counting section
506
for a ½ rate which has half the quantity of information of the full rate (step
703
) and in step
704
it makes a judgment based on the quality information of the ½ rate. Rate judgment is continued in this way repeating the same sequential processing.
However, the conventional transmission rate judgment apparatus above needs to perform decoding for all rates or multiple rates, having the problem of increasing the amount of processing and hence increasing power consumption. For battery-operated apparatuses, for example portable terminals in particular, an increase in power consumption leads to a decrease of conversation time and waiting time.
SUMMARY OF THE INVENTION
The present invention has been implemented taking account of the problem above and it is an objective of the present invention to provide a transmission rate judgment method and an apparatus for it that will reduce the amount of average decoding processing, making it possible to reduce power consumption.
The present invention detects the number of received symbol repetitions, determines the priority order of transmission rates in decoding the received signal based on this symbol repetition number and decodes the received symbol at this determined transmission rate.
This configuration allows decoding to be carried out starting from a rate which is most likely to be the transmission rate of the received symbol, making it possible to omit unnecessary decoding processing. This results in a reduction of power consumption.
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patent: 5627845 (1997-05-01), ASANO et al.
patent: 5689511 (1997-11-01), Shimazaki et al.
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patent: 5883923 (1999-03-01), Shimazaki
patent: 5917837 (1999-06-01), Stein
patent: 5978428 (1999-11-01), Hayashi
patent: 6108372 (2000-08-01), Tidemann, Jr. et al.
patent: 6111912 (2000-08-01), Cohen et al.
patent: 763902 (1997-03-01), None
patent: 8-130535 (1996-05-01), None
patent: 9501548 (1997-02-01), None
patent: 9-98150 (1997-04-01), None
patent: 95/01032 (1995-01-01), None
English Language Abstract of JP 8-130535.
English Language Abstract of JP 9-98150.
Baker Stephen M.
Greenblum & Bernstein P.L.C.
Matsushita Electric - Industrial Co., Ltd.
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