Practical Feedback Design based OFDM Link Adaptive Communications over Frequency Selective Channels

In ideal OFDM adaptive transmissions, each sub-carrier can get an independent adaptive mode according to the Channel State Information (CSI). The awfully large amount of CSI feedback and signalling transmissions will be a serious problem in adaptive OFDM systems. This paper focuses on the practical feedback and adaptive signalling designs of adaptive OFDM systems. Based on the characteristics of frequency selective channels, a Dynamic Neighboring Subcarrier Grouping Scheme (DNSGS) is proposed to cut down the feedback and adaptive signalling overhead, and to simplify the implementation of adaptive OFDM systems. Then the capacity of DNSGS based OFDM systems is also given. The simulation results powerfully show that the scheme designed in this paper is flexible enough for different kinds of communication environments, and can effectively cut down the feedback and signalling overhead with rather limited performance penalty. Besides, DNSGS outperforms the existing grouping schemes greatly.