Designs of Access Mechanisms in IEEE 802.16e Mobile Systems

Abstract

In this paper, we first propose a call admission control algorithm for IEEE 802.16e mobile WiMAX system. We then design the handover mechanism according to the general handover procedure specified by the IEEE 802.16e-2005 standard. Performance evaluations via simulations are conducted to compare the system performance for the network with or without handover procedures employed. It is also found that the transmission quality is subject to the modulation rate change significantly in the mobile environments. The proposed mechanisms are shown to reduce connection blocking rate and packet dropping rate effectively to enhance the efficiency of the mobile WiMAX system. Polling Service), nrtPS (Non Real-time Polling Service), and BE (Best Effort). The UGS is designed to support real-time service flow that generates fixed-size data periodically, such as T1/E1, VoIP without silence suppression. The ertPS is designed to represent real-time service flow that generates ON-OFF type data on the periodical interval, such as VoIP with silence suppression. The rtPS is designed to support real-time service flow that generates variable size data, such as video streaming services. The nrtPS is designed to support non real-time service flow that generates variable size data, such as FTP. The BE is designed to support best effort service, such as email. In the mobile WiMAX environment, the handover procedure occurs when the MS moves into the service range of another BS. Two HO (handover) processes are defined in IEEE 802.16e-2005 standard: the hard handover process and the soft handover process. The hard handover is also called break-before-make handover. The MS starts connections with target BS only after disconnecting service with the serving BS. On the other hand, the soft handover is also called make-before-break handover. The MS starts connections with target BS before disconnecting service with the serving BS. In this paper, the QoS mechanisms for the employment in the mobile WiMAX environment are proposed. We compare the performance of various traffic type data with or without handover procedures in the mobile WiMAX environment via simulations. The connection blocking probability and packet dropping rate under various scenarios are investigated. The rest of this paper is organized as follows. Related