elengths and transmission capabilities as fiber. Commercial FSO systems use either the 1550 nm or the 780 to 850 nm spectrum, with a few systems being designed for 10,000 nm operation. FSO does not require frequency spectrum and thus operational expenses are significantly lower. Such systems can also be used as a backup for microwave radios and thus make the network more resilient. FSO systems are quite susceptible to fog conditions. Other factors affecting FSO performance include scintillation, window attenuation, alignment or building motion, and solar interference and line of sight Next Generation Mobile Communications Ecosystem obstructions. FSO is essentially a 3 nine's technology giving a typical 1 km range, with higher availability at the expense of range reduction. The details on FSO can be found in [9]. 7.3.5 Local Multipoint Distribution System (LMDS) Local Multipoint Distribution Service (LMDS) is a fixed PMP wireless service typically using spectrum in the 26-31.3 GHz and 40.5-42.5 range depending on the country of use. At these frequencies, the range is limited to about 5 km, hence the use of "local" in LMDS. LMDS requires LOS and its range is highly dependent on rain conditions. The IEEE 802.16-2001 standard was initiated to primarily target LMDS band and the solutions available can support TDM, IP, ATM, and SO on, traffic. This standard was published in 2002, and it specifies the air interface for wireless metropolitan area networks (WMANs) in the 10-66 GHz spectrum. The signals at these frequencies are quite susceptible to rain that changes slowly in time. This susceptibility can be addressed by inserting a rain fade margin into the link budget in order to satisfy an availability of 99.9 to 99.99%. Fade Margin is added to compensate for losses that occurred due to rain. Fade margin is a design allowance that provides for sufficient system gain or sensitivity to accommodate expected fading, for the purpose of ensuring that the required quality of service is maintained. LMDS is widely used in Europe