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Highly efficient iterative code multi-user detection method for OFDM system

A multi-user detection and multi-user technology, applied in the field of iterative coding multi-user detection, can solve problems such as multi-user demodulation difficulties

Inactive Publication Date: 2009-07-01
TSINGHUA UNIV
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Problems solved by technology

But after the received signal passes through FFT (fast Fourier transform), on each subcarrier, only one complex value is output, which causes new difficulties for multi-user demodulation, which is also the solution of the multi-user demodulation algorithm proposed in this patent application one of the difficulties

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  • Highly efficient iterative code multi-user detection method for OFDM system
  • Highly efficient iterative code multi-user detection method for OFDM system
  • Highly efficient iterative code multi-user detection method for OFDM system

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[0103] Assume that in the OFDM system, there are 1024 subcarriers, and there are two users whose modulation mode is 16QAM, that is, K′=2, K=4, N=1024. Assumption: Each user adopts a 1 / 2 code rate Turbo code.

[0104] The sending end workflow of User 1 and User 2 is the same, and the steps are as follows:

[0105] (1) The user's coder performs Turbo coding on the user's information bits. Since the number of subcarriers is 1024 and 16QAM modulation is used, the length of each coded block is 4096;

[0106] (2) The interleaver interleaves the encoded bits output by the encoder, and outputs the interleaved encoded bits to the modulation mapper. User 1 and User 2 use different generation seeds in order to generate different random interleaving patterns. For example, the generation seeds of user 1 and user 2 are 100 and 1000 respectively;

[0107] (3) The transmitting end adopts 16QAM and Gray mapping modulation mode on all subcarriers, and maps 4096 coded bits to 1024 subcarriers...

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Abstract

The efficient iterative coding multi-user detection method used in the OFDM system belongs to the technical field of coding multi-user detection, and is characterized in that it is a method that uses interleaving patterns to distinguish users and iterates between joint multi-user demodulation and single-user decoding detection method. At the same time, it proposes a fast method for calculating the maximum a posteriori probability of coded bits for multi-user demodulators, in which a maximum a posteriori probability of coded bits is constructed using the equivalent user modulation symbol vector as an argument to calculate the maximum The measurement function of the posterior probability, using the characteristics of this function, can avoid a large amount of computation for calculating the function values ​​of all modulation symbol vectors. Finally, according to the function values ​​of all modulation symbol vectors, the maximum a posteriori probability of each user coded bit is calculated. It has the advantage of greatly reducing the amount of calculation in the multi-user demodulator while improving the spectrum efficiency and user capacity, which is convenient for practical use.

Description

technical field [0001] The present invention generally relates to the coded multi-user detection problem in OFDM (orthogonal frequency division multiplexing, orthogonal frequency division multiplexing) system, and the present invention particularly relates to an iterative coded multi-user detection method for improving the spectrum efficiency and user capacity of the OFDM system. Background technique [0002] In modern wireless communication systems, in order to obtain higher transmission reliability, when sending an information sequence, it is usually coded first, then modulated and sent out, while the receiver performs the opposite process of the sending end, first demodulates, and then to decode. The purpose of adding coding is to enable the system to have error detection and error correction capabilities by adding redundancy. The traditional data detection process at the receiving end is to first make a judgment on the received signal in the demodulation unit, such as "...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04J11/00H03M13/00
Inventor 周世东李云洲姚彦王京
Owner TSINGHUA UNIV
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