MS to conserve power and operational resources. The Idle State further benefits the network and the BS by providing a simple method for alerting the MS to pending downlink traffic, and additionally by eliminating airlink and network handover CHAPTER 4 IEEE 802. 16m System Operation and State Diagrams signaling for an inactive MS. The base stations are divided into logical clusters called paging groups. The purpose of these logical groupings is to create a contiguous coverage area where an MS without uplink transmission can be paged in the downlink on availability of any traffic in the BS queue for that MS. The size of paging groups should be large enough SO that most terminals will remain within the same paging group most of the time and small enough SO that the paging overhead is reasonable. A BS may be a member of one or more paging groups. Thus, there are different groupings of base stations with varying paging cycles and paging offsets. The concept of different paging cycles, paging offsets, and listening intervals for mobile stations is illustrated in Figures 4-7 and 4-8. It is shown that different mobile stations may have negotiated different values of paging offset and paging cycle with the serving base station. The grouping of the base stations provides support for the geographical requirements of Idle State operation and additionally may support differentiated and dynamic QoS requirements and scalable load-balancing. The paging groups are identified by a unique 16-bit Paging Group ID (PGID) in the network [6,7]. Figure 4-9 shows an example of four paging groups defined over multiple base stations arranged in a hexagonal grid. The location management, i.e., the process of identifying and tracking a mobile station in the network, consists of location update and paging procedures. The location update is a procedure in which the MS periodically informs the network of its current location. The location is defined as an area that is served by a group of base stations belonging to the same paging group. The net