Fast demodulation method

A demodulation method and fast technology, applied in digital transmission systems, electrical components, error prevention, etc., can solve the problems of low demodulation efficiency, high hardware cost, and high computational complexity

Active Publication Date: 2010-10-06
北京万海云科技有限公司
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  • Abstract
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Problems solved by technology

It can be seen that the computational complexity of the algorithm is quite high, which makes the demodulation efficiency low and the hardware cost high

Method used

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Embodiment Construction

[0041] The core idea of ​​the present invention is: adopt M (M=2 n , n is a natural number, that is, every n consecutive bits are represented by a symbol) In a communication system with quadrature amplitude modulation, when demodulating at the receiving end, for each received symbol y′=y I '+jy Q ', when calculating the logarithmic likelihood ratio LLR of each output bit u in the n output bits corresponding to y', the simplified LLR formula is used for calculation. The derivation process of the simplified LLR formula is as follows:

[0042] For the ideal LLR calculation formula shown in formula 2, only items containing the first specified symbol are reserved in the numerator, and only items containing the second specified symbol are reserved in the denominator, so as to obtain a simplified LLR formula; wherein, the first specified symbol is u=1 on the constellation diagram and the symbol corresponding to the constellation point with the minimum Euclidean distance from y', an...

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Abstract

The invention discloses a fast demodulation method. The method comprises the following steps of: making sure that M is equal to 2n and n is a natural number in a communication system using M-bit orthogonal amplitude modulation; and calculating log-likelihood ratio (LLR) of each output bit at a receiving end by using a simplified LLR formula, wherein only an item including a first specified symbol is retained in the numerator of an ideal LLR formula and only an item including a second specified symbol is retained in the denominator of the ideal LLR formula so as to obtain the simplified LLR formula; the first specified symbol is the symbol corresponding to a constellation point on a constellation diagram with a specified bit of 1 and having the minimum Euclidean distance with a receiving symbol; and the second specified symbol is the symbol corresponding to the constellation point on the constellation diagram with the specified bit of 0 and having the minimum Euclidean distance with the receiving symbol. Through the technical scheme, the method greatly reduces the complexity for calculating the LLR of the output bit, improves the demodulation efficiency, and also reduces the hardware cost.

Description

technical field [0001] The invention relates to the technical field of mobile communication, in particular to a fast demodulation method. Background technique [0002] At present, the modulation methods used in Time Division-Synchronous Code Division Multiple Access (TD-SCDMA, Time Division-Synchronous Code Division Multiple Access) systems mainly include quadrature phase shift keying (QPSK), 16-bit quadrature amplitude modulation (16QAM) and 64-bit quadrature amplitude modulation (64QAM). As a new feature of High Speed ​​Packet Access Evolution (HSPA+), 64QAM has higher requirements for the realization of physical layer calculations. [0003] In the 64QAM modulation mode, every 6 consecutive bits are expressed as a complex symbol x. figure 1 It is the constellation diagram of 64QAM adopted in the existing TD-SCDMA system. exist figure 1 In the complex plane shown, the horizontal axis represents the real part (Re), the vertical axis represents the imaginary part (Im), an...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/38H04L1/00
Inventor 李军赵训威
Owner 北京万海云科技有限公司
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