Alpha Omega Wireless Blog

Licensed Microwave Wireless Backhaul

Posted by Joe Wargo on Wed, Apr 14, 2010 @ 03:34 PM

Licensed microwave wireless backhaul is also known as fixed wireless backhaul. A microwave link is a point to point wireless bridge or a point to multipoint wireless bridge used for wireless Ethernet backhaul. Microwave backhaul is becoming more popular for wireless Ethernet bridge applications as a result of noise interference in unlicensed wireless spectrum (U-NII Band).

The term "Microwave" is a broad term that covers the UHF (Ultra High Frequency with frequencies between 300MHz and 3GHz) to the EHF (Extremely High Frequency with frequencies between 30GHz to 300GHz). Licensed microwave wireless Ethernet bridge systems operate in the SHF (Super High Frequency with frequencies between 3GHz to 30GHz) and the EHF bands. Typical licensed microwave link frequencies used for wireless backhaul operate within 3.65GHz WiMax (as a point to multipoint wireless backhaul), 4.9GHz public Safety, 6GHz, 11GHz, 18GHz, 23GHz bands and the 80GHz millimeter wave E-band.  Microwave link example

For example: a licensed microwave point to point wireless Ethernet bridge that operates in 23GHz band will have a licensed frequency channel to transmit on and a channel to receive on. One end of the wireless link being channelized on the low end of the 23GHz band and the other end of the wireless link channelized on the high end of the 23GHz band.

Licensed Microwave link

To operate a licensed microwave wireless radio system one must obtain a license from the FCC by performing frequency coordination, filing a public notice (PCN), and submitting an application (601 form) with the FCC. This process is to ensure that no one else is already operating on the same frequency or a frequency that will inject interference on existing systems. Getting a license to operate a microwave link is inexpensive and can be obtained in the matter of weeks. Licensed microwave link operators are permitted exclusive use of part of the band on a particular azimuth over an assigned geographic area. If licensed radios encounter interference, it is typically resolved with the assistance of the regulatory body.

A fixed wireless microwave link can go distances up to 50+ miles and provide data rates of 10Mbps full duplex to GigE Full Duplex (gigabit wireless). Licensed microwave backhaul radios provide security from the risk of interference from other RF systems. Interference can degrade a radio system's performance and in some cases even prevent the system from functioning at all. Licensed microwave wireless systems can be engineered to provide predictable reliability of 99.999% uptime.

Licensed microwave wireless radio systems are typically built and designed for long term solutions. The wireless bridge hardware is designed to provide carrier grade performance (high bandwidth and low latency). Unlike many of the Atheros (Wi-Fi) chipset based wireless Ethernet bridge systems many use, licensed microwave link systems use actual transceivers and receivers hardware that do not have high IP packet overhead. Because a microwave link is licensed and is not to inject and interference on other licensed microwave backhaul operators in the area they must have LOS (line of sight) and not cause heavy multipath. This is a common question of why licensed microwave radios don't use OFDM or MIMO and why they can't be used in NLOS (non line of sight) applications. In a NLOS wireless link application radios that use OFDM or MIMO take advantage of multipath for their connectivity.

Prior to considering a licensed microwave backhaul a wireless site survey and a proper wireless path calculation should be performed. As with any point to point wireless backhaul system a certified expert should perform the wireless installation. When an organization needs a carrier grade network connection where fiber is not an option or is too expensive, a point to point wireless licensed microwave link is a cost effective solution.

Tags: General, Wireless 101, Licensed wireless, Point to Point Wireless