ould be delivered to an IP-based layer or to a switching layer. The MAC layer should be optimized to support multiple specific physical implementations [1,2]. The physical and MAC layers desired characteristics are shown in Tables 6.1 and 6.2 respectively. The 802.20 Standard The IEEE 802.20 standard specifies the physical and medium access control layers of an air inter- face for interoperable mobile broadband wireless access systems, operating in licensed bands below Table 6.2 MAC layer parameters Characteristics Target Value Number of Active Users per Sector/Cell Transition from Active On to Active Hold State <100 ms Transition Time from Active Hold State to Active On State <50 ms Transition Time from Active Hold State to Inactive Sleep State <100 ms Access Time from Inactive Sleep State to Active On State <200 ms Paging Signal Periodicity <100 ms Paging Signal Duration <1 ms Minimum Scheduling Interval <2 ms UL Request Time <10 ms Inter-Sector/Cell Handoff Time <200 ms Sources: Bolton et al. C 2007 IEEE [1], IEEE 2004 [2] and 2003 [3] IEEE 802.20 Mobile-Fi 3.5 GHz. The system is optimized for IP-data transport, with peak data rates per user in excess of 1 Mbps. It was developed to meet the unique requirements for supporting high speed data services while at the same time maintaining full user mobility (up to 250 km/h). The standard is unique in the sense that it doesn't need to comply with any previous radio air interface; the work was initiated and completed from the ground up. The standard has used specific references from the ATIS standard "ATIS High Capacity - Spatial Division Multiple Access (HC-SDMA) Standard (ATIS-0700004-2005)` and TIA 3GPP2 UMB (Ultra Mobile Broadband) air interface specifications. The standard has specified two modes of operation namely Wideband mode and 625k-MC mode. The Wideband mode can operate in both FDD and TDD duplex modes. The 625k-MC mode on the other hand is designed with 625 kHz carrier bandwidth supporting aggregation of multiple carriers for TDD operation only. The stan