Efficient MAC Protocol for Subcarrier-Wise Rate Adaptation over WLAN

While bit-loading algorithms over wireless systems have been extensively studied, the development of a protocol which implements bit-loading-based rate adaptation over wireless systems has not been highlighted. The design of such a protocol is not a trivial problem, due to the overhead associated with the feedback information. In this paper, a novel protocol is proposed to provide an efficient way to implement subcarrier-wise rate adaptation in OFDM-based wireless systems. When receiving a Ready-To-Send (RTS) packet, the receiver determines the number of bits to be allocated on each subcarrier through channel estimation. This decision is delivered to the sender using an additional OFDM symbol in the Clear-To-Send (CTS) packet. That is, bit-allocation over subcarriers is achieved using only one additional OFDM symbol. The protocol enhances the channel efficiency in spite of the overhead of one additional OFDM symbol.