2G Cellular Satellite Paging 1000 km Mobility Figure 1.0-3 Current technologies in the wireless landscape provide a range of choices, from high-bandwidth fixed systems to wide area systems supporting low to moderate data rates. CHAPTER 1.0 Introduction A Generic Wireless System Attenuation Interference Blockage TRANSMITTER Multipath RECEIVER TRANSMITTER Interception Figure 1.0-4 A generic wireless system. Inherent weaknesses of the wireless medium are offset by its flexibility and support for mobility. lower-cost, unlicensed equipment, operating in the 2.4 techniques and made available by resellers in the range GHz industrial, scientific, and medical (ISM) or 5 GHz of 20 kbps to 2 Mbps. According to the Global VSAT unlicensed national information infrastructure (U-NII) Forum [3], there are over 500,000 VSAT terminals in- bands. stalled worldwide. Point to multipoint Free space optical Local multipoint distribution system (LMDS) and mul- A fairly recent arrival on the scene is free space optical tichannel multipoint distribution service (MMDS) are (FSO) communications, which shares characteristics carrier-grade technologies intended for wireless Internet with both point-to-point RF and fiber optic technologies. access and general communication services. Spectrum As in point-to-point systems, a focused signal carries has been allocated for these systems in several super high high-throughput bitstreams between two points; as in frequency (SHF) bands, offering tens of megabits per fiber optics, a laser or light-emitting diode (LED) is used second of throughput. Along these lines, the Institute of to generate the optical signal that carries the information. Electrical and Electronic Engineers (IEEE) 802.16 Operating with no spectrum license, and with speeds working group is developing a family of standards for in excess of 1 Gbps, FSO offers an attractive choice for wireless metropolitan area networks (MANs). The tech- some backhaul and LAN extension applications. One nology provides a competitor to cable modem and DS