Distributed Call Admission Control Schemes For QoS Provisioning In OFDMA System

Call admission control (CAC) in wireless networks is an important and a challenging issue. It is the basis of QoS provisioning and the use of resources in wireless network. As a consequence, it influences the performance of wireless network greatly.In this paper, we propose two distributed call admission control schemes for multiservice OFDMA system. The works present a complete mechanism that controls the handoff dropping probability, provides multiservice and ensures requirement of packet delay. In the first proposed call admission control (CAC) scheme, a cell dynamically adjusts optimal new call and handoff acceptance ratios by three steps. First, exchange numbers of calls in handoff area with its adjacent cells. Then, dynamically allocate resource for different types of traffic. Finally, use a Markov queue model and a bidirectional iterative search method (BIS) to calculate the new call and handoff acceptance ratios to obtain a near-maximal network utility which depends on both packets delay and the number of ongoing calls. The second proposed call admission control (CAC) scheme, which is based on the fuzzy logic, also includes three steps. In the first step, base stations exchange numbers of calls in handoff area with its adjacent cells. In the second step, the base stations collect this information and the length of the queue as the input of the fuzzy controller; and then the new call and handoff acceptance ratios can be obtained by inferring and defuzzier. In the third step, the base stations allocate resource for different types of traffic. Simulation results show the performance gain of those proposed schemes.