Opportunistic Scheduling in Decentralized OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is emerging as a key modulation scheme for future high speed packets based wireless transmission systems. In a wireless multiuser network system, when an opportunistic scheduling is employed in the OFDM system with adaptive modulation, it may encounter implementation problems due to the need for a large amount of channel information. In this paper we propose a decentralized scheduling scheme to exploit multiuser diversity (MUDiv) in OFDM systems. Users access the channel using a simple variation of the ALOHA random access protocol, termed channel-aware/collision-limited ALOHA. Based on the channel quality, users randomly transmit a request packet with a probability p. When a collision occurs, collided users will retransmit a request packet with probability p. We present an analytical analysis of the average system throughput (average spectral efficiency). We compare our proposed scheduling scheme with the proposed scheduling scheme , the optimal selective diversity scheduling scheme (centralized scheduling), and the round-robin scheduling scheme.