A self-adapted modulation and encoding method in orthogonal frequency division multiplexing system

Abstract

The invention discloses a self-adapting modulating and coding method in orthogonal frequency division multiplexing system, it includes: the first step, setting original time window; the second step, obtaining adapted time window based on time window parameter; the third step, based station evaluates average 1/EVM value and standard difference of down sending time window; the forth step, inquiring AMC judging graph to obtain corresponding modulating and coding modee based on average 1/EVM value and standard difference; the fifth step, evaluating error code ratio, and comparing with expected error code ratio: if evaluated error code ratio <= expected error code ratio, turn to step six; If else, adjust time window parameter, turn to step two; the sixth step, modulate and code. The invention can obtain modulating and coding mode which fits for current channel, increases actual effect of AMC, decreases possibility of interrupt of system, increases spectrum efficiency, at the same time error ratio can be decreased.

Description

technical field [0001] The invention relates to the field of modulation and coding in wireless communication, in particular to an adaptive modulation and coding method in an Orthogonal Frequency Division Multiplexing (OFDM, Orthogonal Frequency Division Multiplexing) system. Background technique [0002] An important feature of wireless channels is multipath propagation, which causes received signals to overlap each other, resulting in inter-symbol interference. When the transmission rate is high, the shorter the signal duration is, the wider the corresponding bandwidth is. If the signal bandwidth exceeds the channel coherent bandwidth, the time dispersion characteristic of the channel will cause frequency selective fading to the received signal. [0003] Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing) technology can better solve this problem. OFDM divides the channel into many orthogonal sub-channels in the frequency domain. The carr...

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Problems solved by technology

But in fast time-varying environments, fixed time windows may make it difficult to track fast fading channels with a predefined update period

In other words, the update period is relatively large, and the current CQI may not be valid for the next transmission with actual feedback delay

In addition, the above method uses the average RSSI of the signal received within the time window to determine the modulation, demodulation and coding scheme (MCS, Modulation and Coding Schemes) corresponding to the changing channel, without considering the channel fluctuation

[0008] In fact, the fluctuation error of the received signal RSSI will lead to the selection of an inappropriate modulation scheme. As a result, the signal modulation and coding methods are improperly selected, which wastes the system capacity or causes an increase in the bit error rate.

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