Variable transmission bit rate discrimination method and apparatus

• US 5,638,408 A
• Filed: 11/13/1995
• Issued: 06/10/1997
• Est. Priority Date: 11/14/1994
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Takaki, Tetsuya
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US08/555,890
• Time in Patent Office: 575 Days
• Field of Search: 375/262, 375/341, 375/340, 375/377, 371/43
• US Class Current: 375/341
• CPC Class Codes: H03M 13/3961 Arrangements of methods for branch or transition metric calculation
• CPC Class Codes: H03M 13/41 using the Viterbi algorithm or Viterbi processors
• CPC Class Codes: H03M 13/6502 Reduction of hardware complexity or efficient processing
• CPC Class Codes: H04B 7/264 for data rate control
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0046 Code rate detection or code type detection H04L1/0038 takes precedence; detection of the data rate H04L25/0262; for packet format H04L1/0091
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 25/0262 Arrangements for detecting the data rate of an incoming signal

Abstract

The invention provides a variable bit rate discrimination method and apparatus wherein a transmission bit rate of data received by a mobile station in a mobile communication which employs a spectrum spreading method can be discriminated readily to realize reduction in time required for decoding processing and miniaturization in circuit scale. A variable bit rate including four different transmission bit rates is used as a transmission rate of a traffic channel from a base station to a mobile station, and transmission data are encoded using convolutional encoder for error correction and transmitted. In the mobile station, received data are decoded for the four individual transmission bit rates using Viterbi decoders to obtain path metric values which are sum totals of errors of the received data. Then, one of the transmission bit rates which exhibits a lowest one of the path metric values is selected as a bit rate used for transmission of the transmission data. Consequently, after Viterbi decoding, no further encoding is required.

Claims

1. A method of discriminating a variable bit rate in a mobile communication system, wherein four transmission bit rates are used for a transmission rate of a traffic channel from a base station to a mobile station and transmission data are encoded using a convolutional encoder for error correction and are transmitted, the method comprising the steps of:

decoding, in the mobile station, received data for the four individual transmission bit rates using Viterbi decoders to obtain path metric values which are sum totals of errors of the received data, together with results of decoding for the transmission bit rates;

comparing the four path metric values in magnitude with each other; and

selecting one of the four transmission bit rates which exhibits a lowest path metric value as a bit rate at which the transmission data have been transmitted.

2. A variable bit rate discrimination apparatus for a mobile communication system, wherein said variable bit rate including four different transmission bit rates is used as a transmission rate of a traffic channel from a base station to a mobile station and transmission data are encoded using convolutional encoder for error correction and transmitted, said variable bit rate discrimination apparatus being provided in the mobile station, said variable bit discrimination apparatus comprising:

means for demodulating received data from the base station and despreading a spectrum of the received data;

means for descrambling the received data based on information passed on thereto from the base station on a synchronization channel;

means for block interleaving the descrambled received data to restore an original order of the received data;

received symbol adders for adding the block interleaved received data of the individual transmission bit rates by repetition symbol rates corresponding to the transmission bit rates;

calculators for calculating branch metrics for use for Viterbi decoding based on the thus added received data;

Viterbi decoders for performing Viterbi decoding based on values of the thus calculated branch metrics and outputting results of the decoding and path metric values for the individual transmission bit rates;

a comparator for comparing the path metric values outputted from said Viterbi decoders with each other in magnitude and selecting and outputting a lowest one of the path metric values; and

a switch for selecting, in response to an output of said comparator, one of output terminals of said Viterbi decoders from which the received data of the transmission bit rate having the lowest path metric value are outputted and connecting the selected output terminal to an information source decoder for information bits of the received data.

3. A variable bit rate discrimination apparatus for a mobile communication system, wherein said variable bit rate including four different transmission bit rates is used as a transmission rate of a traffic channel from a base station to a mobile station and transmission date are encoded using convolutional encoder for error correction and transmitted, said variable bit rate discrimination apparatus being provided in the mobile station, said variable bit discrimination apparatus comprising:

demodulation to demodulate received data from the base station and despreading a spectrum of the received data;

descrambler to descramble the received data based on information passed on thereto from the base station on a synchronization channel;

block interleaver to block interleave the descrambled received data to restore an original order of the received data;

received symbol adders for adding the block interleaved received data of the individual transmission bit rates by repetition symbol rates corresponding to the transmission bit rates;

calculators for calculating branch metrics for use for Viterbi decoding based on the thus added received data;

Viterbi decoders for performing Viterbi decoding based on values of the thus calculated branch metrics and outputting results of the decoding and path metric values for the individual transmission bit rates;

a comparator for comparing the path metric values outputted from said Viterbi decoders with each other in magnitude and selecting and outputting a lowest one of the path metric values; and

a switch for selecting, in response to an output of said comparator, one of output terminals of said Viterbi decoders from which the received data of the transmission bit rate having the lowest path metric value are outputted and connecting the selected output terminal to an information source decoder for information bits of the received data.