An implementing method for shortening critical path of Turbo decoder

Abstract

The invention relates to a method for processing digital signals used in the fields of communication and electronics, in particular to a method for realizing shortening of the key path of a Turbo decoder. The present invention seeks the minimum value for the old state metric when alternately decoding the input signal; subtracts the minimum value from the newly calculated state metric. Since the two steps of calculating the minimum value of the old state metric and calculating the new state metric are carried out at the same time, compared with the traditional metric normalization method, the critical path is greatly shortened, making it possible to design a high-speed Turbo decoder . The simulation shows that the performance difference between the method of the present invention and the traditional method for normalization processing is not more than 0.1dB.

Description

technical field [0001] The invention relates to a method for processing digital signals used in the fields of communication and electronics, in particular to a method for shortening the critical path of a Turbo decoder, in particular to a method for shortening the critical path of a Turbo decoder through normalization processing. critical path method. Background technique [0002] Recently, the application of Turbo codes in FEC of cellular systems has attracted attention. Turbo codes are parallel or serial concatenated cyclic convolutional codes. The encoding is iterative. Its performance in AWGN and Rayleigh fading channels is close to the Shannon limit. [0003] Turbo codes have excellent error correction performance and are suitable for high-speed data transmission services that do not require high decoding delays. They can increase system capacity and reduce requirements for transmission power. [0004] In the WCDMA system, the Turbo code is used in the uplink and downl...

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Problems solved by technology

[0010] The common disadvantage of these two normalization operations is that the critical path is greatly extended, because the delay in finding the minimum value in multiple state path metrics is relatively large

For example, when a WCDMA system performs Turbo decoding, there are 8 state metrics. In order to find their minimum value within one clock cycle, at least three levels of comparators are required, and the bit width of each comparator is about 10 bits. It can be seen that the minimum The value delay is quite large, and the normalization operation can only be performed after the minimum value is found, and then a new branch metric is added, that is to say, the operation of finding the minimum value and other operations occur sequentially in time and cannot be completed in parallel , thus directly leading to the extension of the critical path

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