Cross-layer dynamic subcarrier allocation in multiuser OFDM system with MAC layer diverse QoS constraints

Multiuser OFDM (MU-OFDM) is widely applied nowadays to provide diverse Quality of Service (QoS) for multiple users. Subcarrier allocation according to the instantaneous channel state information (CSI) in MU-OFDM system has been well studied while the research of allocating subcarriers to each user constrained by diverse QoS requirements still remains large space undisclosed. In this paper, in order to meet users´ diverse QoS requirements in MU-OFDM system, we propose a cross-layer dynamic subcarrier allocation algorithm where users´ MAC layer diverse QoS requirements and the subcarrier allocation at PHY layer are jointly considered. The MAC layer queue status is modeled as a finite-state Markov chain (FSMC), using which the QoS constraints are transformed to the minimal PHY layer data rate requirement of each user. A sub-optimal dynamic subcarrier allocation algorithm is then proposed not only to satisfy the PHY layer data rate but also to significantly reduce the computational burden, aiming at maximizing system capacity. Finally, we verify the proposed cross-layer algorithm by simulations.