________________

Fixed Broadband Wireless - Multipoint

Point to Multipoint Wireless Services

Licensed point to multipoint Microwave systems are relatively new . These systems are not widely used because of the high cost of equipment, and licenses. These systems also face stiff competition from established providers in the dense population areas intended for deployment. If the cost of equipment comes down these systems could be profitable in rural areas where there are no alternative services.

• Multi -channel Multipoint Distribution Service (MMDS) fixed wireless is a transport system operating in the 2.1GHz and 2.5-2.7GHz frequencies, and was originally designed to be a wireless cable TV delivery system. It has recently begun to be used to deliver Internet at up to 3 Mbps, point-to-multipoint, in large metropolitan areas.
  
  
• Local Multipoint Distribution Service (LMDS) fixed wireless is a point -to-multipoint system delivering up to 10 Mbps broadband in the 27.5-29.5GHz and 31.0-31.3GHz spectrum. This system is meant for very dense markets, as it has a short range of 3-5 kilometres, line-of-site. LMDS is particularly vulnerable to rain and snow fade.
  
  
• Satellite Internet service is currently available from some satellite TV services, but is limited by the need to use traditional telephone lines for uplink from the user. New systems using the Ka-band for two-way service are not yet in operation, but will be during 2003. Promoters of these systems estimate that they will be offering 400 Kbps to 5 Mbps Internet access.
  

Unlicensed point to multipoint microwave systems use spectrum reserved for industrial, scientific and medical (ISM) use, and as the name implies, no license is required for its use. Bands of ISM spectrum are at 902 to 928 MHz, 2.4 to 2.483 GHz and 5.750 GHz to 5.825 GHz. Recently another another 300 MHz of unlicensed spectrum has been added between 5.725 GHz and 5.825 GHz, known as the UNII band. In order to avoid interference from other radio installations and devices (X-Ray machines, microwave ovens etc.) using these bands, microwave radios use spread spectrum techniques that rapidly spread their signal between many different frequencies in the band. These radios can operate well as point-to-multipoint links, serving many smaller bandwidth customers with one radio transmitter. Spread spectrum transmissions are inherently secure because their low power output and dynamic frequency shifts.

• Wi-Fi systems were developed to connect users to a LAN inside buildings without cabling to each work station. These systems normally use the 802.11b standard, and transmit in the 2.4 GHz spectrum, although new 802.11a and 802.11g systems are available. These systems have a range of about 300 feet. Lately these products have been used to provide Internet connectivity in public spaces known as "hot spots".
  
  
• Mesh Networks and Packet Relay systems use each customer as a sending and receiving relay station, thus reducing the need for "line-of-site" service transmitters. These systems typically use unlicensed spectrum 2.4 and 5.7 GHz bands. They are just gaining market acceptance and should work well in urban and suburban areas.
  
  
• More to come

Copyright © 2002 CoastWorks Internet

___________________