Wimax standards and Security The Wimax

Summary

We have discussed the main mobility functions defined in the IEEE 802.16e standard: power-saving mechanism, HO operation, and paging and location update.
First, the IEEE 802.16e system provides three types of power-saving mecha- nisms. PSC I is used for nonreal-time services and provides a truncated binary exponential algorithm to decide the size of the sleep window, which is suitable for services with burst traffic attribute. PSC II is used for real-time services and provides periodic sleep and listening intervals, taking into account the traffic characteristics of real-time services. PSC III is used for multicast or manage- ment message transmission and provides an efficient sleep mechanism for aperiodic and continuous services.
Second, the IEEE 802.16e system provides a basic HO operation and enhanced mechanisms for fast and seamless HO. Network topology acquisi- tion makes it possible for an MS to acquire information about the properties and quality of a channel from neighboring BSs before an actual handover. To obtain information about the network topology, the MS receives a network topology advertisement message from its serving BS and conducts scanning process and optional association with its neighboring BS. Basic HO opera- tion is performed in the sequence cell reselection, HO decision and initiation, synchronization to target BS downlink, ranging, termination with a serving BS, and network entry. For a smooth HO, the sequential signaling proce- dure among the MS, serving BS, and target BSs is performed and an accurate decision algorithm is required. In addition, MDHO and FBSS support a fast

and seamless HO, because they enable diversity combining and soft HO. However, this operation places many requirements on the BS and MS.

Third, the IEEE 802.16e system provides paging and location update oper- ations. Paging mechanism allows an MS to operate in idle mode. The MS only updates its location and checks a paging message periodically when in idle mode. This mechanism offers advantages with respect to an MS’s energy con- servation and the reduction of used radio resources. Location update should be performed between an MS and a target BS to manage the location of the MS during idle mode operation. Network reentry is conducted when an MS wants to exit from idle mode. Network reentry follows a general network entry procedure, following which the MS can operate normally with a BS.