QoS Provisioning in 802.11 WLAN Coupled with UMTS Network

This paper aims to provide Quality of Service (QoS) for IEEE 802.11 Wireless Local Area Network (WLAN) system integrated with UMTS cellular network. Due to heterogeneous QoS metrics in WLAN and cellular network, our scheme jointly considers the characteristics of the link and network layers. We adopt a scheduling algorithm called IIT (Inserting Idle Time) in the link layer to reduce the packet loss ratio for Variable-Bit-Rate services (VBR). Specifically, the IIT scheduling algorithm allocates the idle system time to VBR services to accommodate the bursts, while satisfying required transmission delay and bandwidth of all RT services. Considering future WLAN coupled with UMTS cellular network, we propose a policy-based call admission control (CAC) scheme at the network layer. Based on different interworking policies, the proposed CAC provides the long-term QoS by limiting the number of admitted connections, while differentiating the services according to their priorities. Detailed analysis is given by taking into account several key statistical factors, such as traffic model, the ratio between the contention free period (CFP) and the contention period (CP), handoff rate. Performance is evaluated through simulation. Simulation results demonstrate that our proposed joint scheme is effective in terms of both system resource utilization and QoS provisioning.