Adaptive subchannel allocation in an OFDMA-based wireless network

Orthogonal frequency division multiplexing (OFDM) is used in both 802.11 and 802.16 (A. Ghosh et al., 2005) wireless network standards and is being evaluated for fourth generation (4G) networks such as those being proposed in the 3GPP and 3GPP2 standards bodies. Its tolerance to frequency selective fading has made it an attractive choice for these broadband wireless networks. In both downlink and uplink directions, resources can be allocated in three dimensions, frequency, time and power. In both cases the resource allocation is performed primarily by the basestation (BS). In this paper we focus on the allocation of downlink resources when such a network is used for quality of service (QoS) applications. Using a utility function framework, we formulate and solve the corresponding optimization problem and use the optimality conditions to design simple, practical algorithms. In doing so we take into account practical details that have not been addressed in previous work