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State metric bit wide control method and device for Turbo code decoder

A state measurement and control method technology, applied in the direction of error correction/detection, encoding, code conversion, etc. using convolutional codes, can solve problems such as overflow and degraded Turbo code decoding performance, reduce the number of operations, and simplify complexity degree of effect

Active Publication Date: 2006-05-24
XUANPU INDUSTRY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in order to ensure the performance of the Turbo code decoder, there must be certain requirements for the number of quantized bits in the operation, that is, the number of bits in the operation should not be too small, otherwise the forward and backward path metrics will overflow, and the Turbo code will be greatly deteriorated. decoding performance, which is in contradiction with the implementation scale and operation speed

Method used

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  • State metric bit wide control method and device for Turbo code decoder
  • State metric bit wide control method and device for Turbo code decoder
  • State metric bit wide control method and device for Turbo code decoder

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Embodiment approach

[0037] The present invention provides a kind of state measurement bit width control method and device used in a Turbo code decoder, which comprises the following steps:

[0038] Step 1, the forward and reverse path metric calculation unit utilizes the Max-Log-MAP algorithm to calculate the initial forward path metric and the backward path metric:

[0039] α ^ k ( m ) = log [ α k ( m ) ] = = max m ′ ( x k u k i + y k ...

specific Embodiment

[0059] The input data bit width of the WCDMA system Turbo code decoder is 6 bits, and the bit width of the external information generated by the SISO decoder is 10 bits. If the normalization algorithm of the present invention is not used, the required bit width of the forward and backward path metrics is at least 24 bits, so as to ensure that no overflow occurs when calculating α and β. If the normalization algorithm provided by the present invention is adopted, the simulation results show that when the bit width of the forward and backward path metrics is 8 bits, the decoding performance of the Turbo code can be guaranteed to have no loss basically.

[0060] The present invention provides a method and device for controlling the state metric bit width in a Turbo code decoder, which controls the calculation results of each step in the forward and reverse path metric calculations within a very limited range, thereby making the calculation The number of digits is greatly reduced,...

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Abstract

The method makes all measured state values positive generated from forward directed and inverted recursion procedures of MAP decoding algorithm for Turbo codes. Thus, simple normalizing operation can be adopted to reduce bit width of measured state value. Moreover, implementation of hardware is simpler according the measured state values calculated by the disclosed method. When calculating measured path values through forward directed and inverted recursion procedures, the method adds specific offset to the calculation so that all measured path values obtained are positive. Using minimal value in all measured path values in current moment carries out normalization for all measured path values. Advantages are: reducing bit width of measured state values without influence on performance of decoder of Turbo code; reducing area of chip. The invention also lowers complexity of hardware for realizing recursion procedures.

Description

technical field [0001] The invention relates to a method and device for controlling the bit width of a state metric in a Turbo code decoder. Background technique [0002] The principle of the Turbo code is based on the modification of the algorithm and structure of the traditional concatenated code. The introduction of the inner interleaver makes the positive feedback of iterative decoding well eliminated. The turbo code encoder is composed of two recursive systematic convolutional codes (recursive systematic convolutional codes, referred to as RSC codes), an inner interleaver and a deleter. Figure 1 The structure of Turbo code encoder in cdma2000 system is given. According to the different puncture forms of the deleter, the coding rate of the Turbo code can vary from 1 / 6 to 1 / 2. Considering the complexity of decoder implementation and decoding performance, Turbo codes are generally decoded using an iterative maximum a posteriori (MAP) decoding algorithm. Due to the high ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03M13/29H03M13/00H03M13/23H03M13/27H04L1/00
Inventor 单鸣
Owner XUANPU INDUSTRY CO LTD