Optimal Radio Resource Partition for Joint Contention- and Connection-Oriented Multi-Channel Access in OFDMA Systems

Orthogonal frequency division multiple access (OFDMA), adopted in the IEEE 802.16e WiMax system, possesses many advantages in the physical layer, but also poses many challenges from the aspect of radio resource allocation. In the IEEE 802.16e WiMax system, a truncated binary backoff algorithm is adopted for resolving the contention in random access, while the time-division OFDMA is used for the connection-oriented access. One interesting radio resource allocation issue in such an OFDMA system is to partition the overall radio resource (bandwidth and time duration) into two portions: one for random access and the other for connection-oriented access. The main contribution of this paper is to design an analytical approach to determine the optimal amount of reserved radio resource in both time and frequency domains for random access with the objective of maximizing the overall efficiency of radio resource while satisfying the delay requirements for supporting real-time services. Furthermore, an analytical model for calculating the access latency and the efficiency of the reserved radio resources is developed.