Throughput-Enhanced Communication Approach for Subscriber Stations in IEEE 802.16 Point-to-Multipoint Networks

The IEEE 802.16 standard for wireless metropolitan area networks (WMANs) is designed to satisfy various demands for high capacity, high data rate, and advanced multimedia services (Abichar et al., 2006). The medium access control (MAC) layer of IEEE 802.16 networks supports both point-to-multipoint (PMP) and mesh modes for packet transmission (IEEE Std. 802.16-2004, 2004). Based on the application requirements, it is suggested in the standard that only one of the modes can be exploited by the network components within the considered time intervals, and the PMP mode is considered the well-adopted one. In the PMP mode, packet transmission is coordinated by a base station (BS) which is responsible for controlling the communication with multiple subscriber stations (SSs) in both downlink (DL) and uplink (UL) directions. All the traffic within an IEEE 802.16 PMP network can be categorized into two types, including inter-cell traffic and intra-cell traffic. For the inter-cell traffic, the source-destination pair of each traffic flow are located in different cells. On the other hand, the intra-cell traffic is defined if they are situated within the same cell. The inefficiency within the PMP mode occurs while two SSs are intended to conduct packet transmission, i.e., the intra-cell traffic between the SSs. It is required for the data packets between the SSs to be forwarded by the BS even though the SSs are adjacent with each others. Due to the packet rerouting process, the communication bandwidth is wasted which consequently increases the packet-rerouting delay. In order to alleviate the drawbacks resulted from the indirect transmission, a directly communicable mechanism between SSs should be considered in IEEE 802.16 networks. Several direct communication approaches have been proposed for different types of networks. The direct-link setup (DLS) protocol is standardized in the IEEE 802.11z draft standard to support direct communication between two SSs in wireless local networks (IEEE P802.11zTM/D5.0, 2009). However, the DLS protocol is designed as a contention-based mechanism, which does not guarantee the access of direct link setup and data exchanges between two SSs. The dynamic slot assignment (DSA) scheme for Bluetooth networks is proposed in (Zhang et al., 2002) and (Cordeiro et al., 2003), which is primarily implemented based on the characteristics of the Bluetooth standard. Since frame structures and medium access mechanisms are different among these wireless communication technologies, both the DLS protocol and DSA scheme cannot be directly applied to IEEE 802.16 networks. 2