y physical layer are provided in Section 6.5. The second air interface mode that is, 625K-MC (625 kiloHertz-spaced MultiCarrier) mode is described in Section 6.5. The 802.20 network architecture and air interface performance aspects are described in Sections 6.7 and 6.8 respectively. In the last two sections the status of 802.20 within the industry and concluding remarks are listed in Sections 6.9 and 6.10 respectively. Next Generation Mobile Communications Ecosystem: Technology Management for Mobile Communications Saad Z. Asif © 2011 John Wiley & Sons, Ltd. ISBN: 978-0-470-74746-9 Next Generation Mobile Communications Ecosystem Table 6.1 Physical layer parameters Characteristics Target Value (for 1.25 MHz paired FDD and 2.5 MHz unpaired TDD) Spectrum <3.5 GHz Mobility Up to 250 km/hr Spectral Efficiency (sustained) > 1 bps/Hz/cell Sectors per Cell 3 sectors per cell (6 or more sectors as well) Peak user data rate (DL) > 1 Mbps Peak user data rate (UL) > -300 kbps Peak aggregate data rate per cell (DL) >4 Mbps Peak aggregate data rate per cell (UL) >800 kbps Doppler Spread >400 Hz Delay Spread Tolerance 10 microseconds Frequency reuse Sources: Bolton et al. C 2007 IEEE [1], IEEE 2004 [2] and 2003 [3] MBWA Requirements and Characteristics The key technical attributes for MBWA set by IEEE 802.20 WG are as follows: Packet based air interface optimized for the transport of IP based services. Operations in licensed bands below 3.5 GHz. Peak data rates per user in excess of 1 Mbps. Support for various vehicular mobility classes up to 250 km/h in a MAN environment. Higher spectral efficiencies and lower latencies than the existing mobile systems. The IEEE 802.20 standard specifications take a modular approach and the modular or layered approach means that there is clear separation of functionality in the system between the user, data and control. The air interface supports a layered architecture where physical and MAC layers have clear responsibilities. The physical and MAC will make up the services that specify what sh