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A Soft Demodulation Method of Quadrature Amplitude Modulation

A technology of quadrature amplitude modulation and soft demodulation, applied in the field of communication, can solve the problem that the accuracy of soft demodulation information and storage capacity are difficult to achieve a good balance

Active Publication Date: 2017-04-19
NATIONZ TECH INC
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  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

[0005] The invention provides a QAM soft demodulation method, which solves the problem that it is difficult to achieve a better balance between the accuracy of soft demodulation information and storage capacity in the prior art

Method used

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  • A Soft Demodulation Method of Quadrature Amplitude Modulation
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  • A Soft Demodulation Method of Quadrature Amplitude Modulation

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Embodiment Construction

[0020] The soft mapping method of QAM can be deduced as follows: mark time k, bit set {u k,i}, i=1,2,3...m is mapped to the real number pair {A of the constellation mapping plane k ,B k}, and the in-phase branch and quadrature branch X of the demodulator receiving data k , Y k It can be expressed as:

[0021] x k =a k A k +NI k Y k =a k B k +NQ k

[0022] where a k It is a Rayleigh random variable under Rayleigh fading channel and 1 under Gaussian white noise channel.

[0023] Among them, NI k and NQ k is the mean is 0 and the variance is Gaussian noise, and they are independent of each other.

[0024] Then the soft output of each bit, that is, the logarithmic likelihood ratio LLR (Logarithm of Likelihood Ratio) is:

[0025]

[0026] Using Bayesian criterion, and since P{u k,i =1}=P{u k,i =0}, the above formula gets:

[0027]

[0028] If the divisor of the QAM mapping is an even power of 2, the in-phase signal X n and the quadrature signal Y n In...

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Abstract

The invention discloses a flexible demodulation method for orthogonal amplitude modulation. The method includes the steps of figuring out an approximate flexible modulation output value LLRapproximate, obtained after demodulation, of each bit according to the real part Rdata or the imaginary part Idata of data to be demodulated, looking up a preset lookup table to find a flexible demodulation modification value LLRD-Normalized of each bit, and figuring out a final flexible demodulation output value LLROutput of each bit according to the approximate flexible modulation output value LLRapproximate of each bit and the flexible demodulation modification value LLRD-Normalized of each bit. According to the technical scheme, a perfect flexible demodulation method of a QAM is provided.

Description

technical field [0001] The invention relates to the communication field, in particular to a soft demodulation method of Quadrature Amplitude Modulation (QAM). Background technique [0002] QAM is a signal modulation method widely used in communication systems in recent years. In the modulation process, QAM uses the amplitude and phase of the carrier signal to represent different digital bit codes at the same time, and combines the multi-ary system with the orthogonal carrier technology to greatly improve the frequency band utilization. For example, China Mobile Multimedia Broadcasting (CMMB), a mobile TV industry standard officially promulgated by the State Administration of Radio, Film and Television in 2006, adopts a 16QAM modulation method. [0003] When demodulating data at the receiving end, commonly used QAM demodulation methods include hard demodulation and soft demodulation. Hard demodulation is to force the judgment of constellation points into corresponding modul...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L27/38
Inventor 陈烽
Owner NATIONZ TECH INC
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