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A Control Method of State Metric Overflow in Turbo Code Decoder

A state measurement and control method technology, applied in the direction of error correction/error detection by combining multiple code structures, can solve problems such as increased delay, large amount of calculation, and impact on decoder throughput, so as to prevent state measurement overflow , Improve the operation speed and reduce the amount of operation

Inactive Publication Date: 2011-12-07
TSINGHUA UNIV
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Problems solved by technology

[0004] This method requires a normalization operation at each step, and the normalization operation needs to wait until all the state metrics at the current moment have been calculated, and the amount of calculation is large, which increases the delay and makes the decoder Throughput suffers greatly

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  • A Control Method of State Metric Overflow in Turbo Code Decoder
  • A Control Method of State Metric Overflow in Turbo Code Decoder
  • A Control Method of State Metric Overflow in Turbo Code Decoder

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Embodiment Construction

[0025] The present invention will be described in detail below in conjunction with examples.

[0026] Using radix-2Turbo code, the state metric is 7bit quantized, then the value range of the state metric is [-64, 63], assuming that the threshold T is 48, and C is 8, it is determined by judging the size of the state metric before 2 beats The magnitude of the correction value.

[0027] A method for controlling state metric overflow in a Turbo code decoder, comprising the following steps:

[0028] 1) Determine the correction value Δ of the branch metric of the current shot according to the magnitude of the logarithmic metric value of each state n times before and before the current time k recursion, and the logarithmic metric value is the forward state metric α k-n (s) or backward state metric β k+n (s), n=2, specifically adopt the following method:

[0029] When recursively forward,

[0030]

[0031] When recursively backward,

[0032]

[0033] Among them, T is the se...

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Abstract

The invention relates to an overflow control method for a state metric of a Turbo code decoder. A correction value delta of a branch metric of a current beat is determined according to logarithm metric sizes of all states before n times that are obtained by recursions from a current time k; a branch metric of the current time k is calculated and is corrected; and finally, a state metric of the current time k is calculated according to the corrected branch metric and amplitude limiting is carried out; when the calculated result is larger than a maximum max, the value of the state metric is max; when the calculated result is less than a minimum min, the value of the state metric is min; and the state metric that has been processed by the amplitude limiting is used for a next recursion. According to the invention, it can be ensured that state metrics of forward and backward recursions during a MAP decoding algorithm process of a Turbo code will not overflow; determination operations can be completed in advance; it is allowed to realize anti-overflow control by a pipelining method. Therefore, an influence of an anti-overflow operation on a recursion speed of a state metric can be reduced, so that a recursion speed during hardware realization can be improved and a decoding throughput capacity can be enhanced.

Description

technical field [0001] The invention belongs to the communication field or the mobile communication field, and in particular relates to a state metric overflow control method in a turbo code decoder. Background technique [0002] Turbo codes have been widely used since they were proposed in 1993. It uses soft output iterative decoding to approximate maximum likelihood decoding, and obtains performance close to the limit of channel capacity. In the protocol of the long term evolution (Long Term Evolution, LTE) project proposed by 3GPP, the turbo code is adopted as the channel coding mode. [0003] Turbo decoding adopts soft-output iterative decoding, and its decoder structure is composed of two-stage soft-input and soft-output (SISO) decoding units DEC1 and DEC2. When decoding, the soft output (external information) generated by DEC1 decoding is used as the input of DEC2, and DEC2 decodes this information as a priori information, and also obtains a soft output, which is use...

Claims

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Application Information

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IPC IPC(8): H03M13/29
Inventor 周世东关安福张秀军孙引陈翔肖立民李云洲
Owner TSINGHUA UNIV
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