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Rate-adaptive method based on rateless codes and high-order qam adaptive demodulation

A rate-adaptive, rateless code technology, applied in the field of information communication, can solve the problems of delimiting the decision-making area when the modulation is not given, restricting the use of high-order modulation constellations, and high computational complexity, so as to avoid the lag of channel state information and inaccurate problems, reducing system complexity and feedback overhead, and the effect of low computational complexity

Active Publication Date: 2018-12-28
CHONGQING UNIV OF POSTS & TELECOMM
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Problems solved by technology

The first type of method needs to determine the area where each received symbol is located to determine the demodulated bits. The computational complexity of demodulation is high, especially when high-order modulation constellations are used, and the existing literature does not give the use of orders above 16. The scheme for delimiting the decision-making area during modulation; the second type of method needs to calculate the preset demodulation threshold. Although this method has low complexity in demodulation, the relevant literature only gives a modulation order of up to 16 When the demodulation threshold is calculated, there is no threshold calculation scheme for higher-order modulation, which limits the use of high-order modulation constellations, and accordingly limits the ability to adapt to channel changes

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  • Rate-adaptive method based on rateless codes and high-order qam adaptive demodulation
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  • Rate-adaptive method based on rateless codes and high-order qam adaptive demodulation

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Embodiment Construction

[0026] The present invention is done following analysis in conjunction with accompanying drawing.

[0027] In adaptive demodulation, whether to demodulate or delete is decided according to the logarithmic likelihood ratio LLR of each bit. let b i is the i-th bit in the modulation symbol s. After the receiving end receives the modulation symbol superimposed with channel noise, that is, the received symbol r, b i The LLR can be calculated by

[0028]

[0029] where p(·) represents the probability density function. The absolute value of the LLR represents b i The higher the value of the judgment credibility, the higher the possibility of making a correct judgment.

[0030] Square M-QAM modulation can be equivalent to two mutually orthogonal In Pulse Amplitude Modulation (PAM), the in-phase component and the quadrature component carry the same number of information bits. If using figure 1 When the Gray-mapped 256-QAM constellation is shown, each modulation symbol s con...

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Abstract

The invention discloses a rate adaptation method based on rateless codes and high-order QAM adaptive demodulation. A fixed modulation and coding scheme is adopted for a transmitting terminal, multiple demodulation modes are adopted for a receiving terminal, and different numbers of bits are demodulated from a received symbol. The decoding complexity constraint and the channel utilization rate are comprehensively considered, the corresponding demodulation mode and the decoding codeword length of the rateless error correcting codes are selected according to the channel quality, and rate adaptive adjustment is achieved. In the method, the modulation order is not limited, and the method is applicable to all square QAM planispheres. According to the scheme, efficient utilization of channels is considered, and meanwhile the decoding complexity is considered, so that the scheme is practical.

Description

technical field [0001] The invention belongs to the fixed modulation and coding method of the sending end in the field of information communication, and the receiving end comprehensively considers the decoding complexity constraint and the channel utilization rate, and realizes the self-adaptive adjustment method of the rate in combination with the rateless error correction code. Background technique [0002] Adaptive Modulation and Coding (AMC) is one of the link adaptation technologies in the communication system, which consists of two parts: adaptive coding and adaptive modulation. In a system using AMC technology, the receiving end estimates the channel and feeds back the estimated channel state information to the sending end, and the sending end dynamically changes the modulation and coding methods based on this to adapt to different channel qualities. channel resources while meeting the quality of service requirements of different businesses. Although adaptive coding ...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L1/00
CPCH04L1/0002H04L1/004
Inventor 雷维嘉宋海娜
Owner CHONGQING UNIV OF POSTS & TELECOMM
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