Adaptive Modulation For OFDM Signals

OFDM信号的自适应调制。OFDM通信信道的子带信噪比变化可达30db。为了优化OFDM信号的带宽效率，需要使所选择的调制技术（如M-ary QAM）适应子频带中可用的信噪比。以这种方式，高质量信道传输最高的比特率，而低质量信道容纳最低的比特率。最终的结果是，通信链路的容量不必受到最坏情况设计的限制。

Adaptive Modulation For OFDM Signals. The sub band Signal To Noise Ratio in an OFDM communications channel varies by as much as 30 dB. In order to optimise the bandwidth efficiency of OFDM signalling it is desirable to adapt the chosen modulation technique such as M-ary QAM to the SNR available in sub bands. In this way high quality channels transmit the highest bit rates, whilst low quality channels accommodate the lowest bit rates. The net result is that the capacity of the communications link does not have to be limited by designing for worst case conditions.