An HMM prediction and throttling-based call admission control scheme for wireless multimedia networks
With the increase in data transmission for wireless networks, multimedia services are gaining popularity in next-generation cellular networks. If the appropriate information exists for Call admission control (CAC) schemes, the terms of quality of service (QoS), such as call dropping probability (CDP), and call blocking probability (CBP) will be kept as low as possible, and higher system utilization can be achieved. Unfortunately, it is difficult to obtain such information owing to user indeterminate mobility. In this paper, the proposed scheme reduces the CDP with a statistical method, called Hidden Markov Models (HMM), that is suitable for solving a dynamic situation has been introduced and applied to the CAC scheme. The prediction of user mobility can be modeled and solved as an optimal-state sequence problem for the HMM. The proposed CAC method that adopts the prediction result of user mobility can reserve appropriate bandwidths for a handoff call in advance, thus, the CDP will be kept below a lower level. Moreover, the throttle flag that indicates the usage of bandwidth in each cell is proposed to prevent the new call request from being dropped in the adjacent cells if handoff is needed, and then the CDP will be further lowered. Besides, the CBP will also be kept relatively low since the proposed method can reserve the suitable bandwidths in the appropriate cells but not reserve stationary ones which are always adopted by traditional CAC methods for each cell. The simulation results show that the proposed method can meet CDP and CBP requirements, and the system utilization can also be improved.
throttle call admission control qos call dropping probability call blocking probability hidden markov models handoff