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A high-order qam demapping method for narrowing the search range aided by channel estimation

A search range and channel estimation technology, applied to baseband system components, multi-carrier systems, etc., can solve problems such as difficult soft information calculation formulas, unsatisfactory bit error performance, and small calculation load

Inactive Publication Date: 2017-01-11
CHANGAN UNIV
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Problems solved by technology

But for high-order QAM, because the algorithm needs to judge the inflection point of each bit to fit the LLR curve, it consumes a lot of resources and time
Moreover, the algorithm has errors for each approximation, which will reduce the performance of the system
[0006] Document 4 "QAM Soft Demodulation Algorithm Implementation and Performance Analysis in HSDPA [China New Communications, 2010: 48-50]" proposed a simplified LLR algorithm based on the boundary method, which has a small amount of calculation, but the bit error performance is not ideal
For high-order QAM, the higher the order, the more constellation points, and the more boundaries, it is difficult to determine the corresponding soft information calculation formula

Method used

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  • A high-order qam demapping method for narrowing the search range aided by channel estimation
  • A high-order qam demapping method for narrowing the search range aided by channel estimation
  • A high-order qam demapping method for narrowing the search range aided by channel estimation

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Embodiment

[0071] Usually, in order to improve system performance, channel coding is effectively combined with high-order modulation techniques. Taking 3GPP2Turbo code as an example, the generator polynomial is (15, 13) 8 (in octal), the code rate is 1 / 3, the information bit length is 570, the decoding algorithm uses the Max-Log-MAP algorithm, 8 iterations, and the maximum number of simulation frames is 10 6 .

[0072] Figure 2 shows the bit error rate performance comparison between 4096-QAM and 1024-QAM under different search ranges and different SNR conditions. It can be seen from Figure 2 that for 4096-QAM, when the SNR is high (such as 19dB), J≤8, the search range is too small, so that the bit error performance is too different from the full set search result, and the BER is increased by 3 More than an order of magnitude; when J≥10, the bit error performance is basically acceptable. For 1024-QAM, the same conclusion can be obtained, when J=8, the same bit error performance as that...

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Abstract

The invention discloses a channel-estimation assisted search range narrowing high-order QAM (Quadrature Amplitude Modulation) demapping algorithm and aims to evaluate contribution of a reference constellation point to demapping by a soft-decision contribution factor and narrow a search range into the reference constellation point with larger soft-decision contribution so as to reduce complexity of high-order QAM demapping. According to the algorithm, the channel estimation information is sufficiently utilized to assist an self-adaptive selection search range, so that the search range is greatly narrowed, the complexity of high-order QAM demapping is effectively reduced, excellent balance between algorithm complexity and performance is realized, and a foundation for expanding a high-order QAM application scene is laid.

Description

technical field [0001] The invention relates to a high-order QAM demapping algorithm for narrowing the search range aided by channel estimation. Background technique [0002] Modulation and demapping technology is a core technology of the communication system, which has a decisive impact on the performance of the communication system. The task of QAM de-mapping is to calculate the best estimate of the transmitted data, and the output of de-mapping can be hard-decision digital bits, or an effective measurement value of soft-decision digital bits at the sending end. Generally, soft-decision demapping and channel decoding (such as Turbo code, LDPC, etc.) work together to further reduce the bit error rate of transmission based on the principle of minimizing the influence of channel noise. [0003] Document 1 "Comparison of Soft Output Algorithms for High-Order Modulation [Journal of Beijing University of Posts and Telecommunications, 2003, 26(1): 82-85]" studied the LogMap algo...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L27/34H04L25/02
Inventor 徐娟姚如贵南花妮高凡琪朱礼亚
Owner CHANGAN UNIV