Capacity of OFDMA-Based WirelessMAN
Orthogonal frequency division multiple access (OFDMA) has emerged as one of the prime multiple-access schemes for broadband wireless networks. The OFDMA scheme can be derived from a generic broadband multicarrier framework. The basic idea of multicarrier modulation is to divide the transmitted bitstream into sub-streams and send these over parallel narrowband subchannels. An important performance measure in multicarrier multiple access is the sum rate capacity. The chapter discusses the sum rate optimality of OFDMA in uplink multicarrier systems with a finite number of subchannels. It examines the OFDMA optimality in both uplink and downlink multiple-input multiple-output (MIMO) multicarrier systems with a finite number of subcarriers. For the general MIMO channels, it is difficult to derive the optimal solution analytically. Exhaustive search is needed to determine OFDMA achievable rates. The chapter explores the OFDMA optimality in uplink and downlink MIMO systems with a finite number of subcarriers.