In Focus: The Where, Who and What of the 3.65 GHz Band

The FCC adopted the rules for the 3.65 – 3.7 GHz band in May 2007, a good nine years after it first proposed to allocate the band to non-Government fixed services on a primary basis. This timeline coincided with parallel development of WiMAX where equipment based on the fixed version of the standard (IEEE 802.16d) first came to market in 2005. In this post, I look at deployments in this band especially as it called for certain features to accommodate co-existence between different systems. But first, here’s a very brief overview of some of the regulatory features.

The 3.65 GHz band is licensed on non-exclusive basis; hence, it is referred to often as semi or lightly licensed. Operators obtain a license from the FCC and register their systems parameters and coordinates in a database (a license can be obtained for nominal fee of $260 for 10 years). Operators have the responsibility to minimize the potential of interference to deployed systems. The process to resolve interference is left to the operators themselves. The FCC requires that all systems implement a contention based protocol (CBP) which would stop transmission if the system detects transmissions from other systems. Two modes are defined: restricted mode describes the ability to detect interference from products of similar contention technology, and un-restricted mode which describe the ability to detect interference from product with dissimilar contention technology. Restricted mode systems are allowed to operate in the lower 25 MHz of the band, while un-restricted mode systems are allowed to use the full 50 MHz. The transmission power is limited to 1W/MHz EiRP for base and fixed stations.

The 3.65 GHz band was used for Fixed Satellite Services (FSS) space-to-earth operations. There are 86 grandfathered earth stations today that are protected by a 150 km radius exclusion zone and three Federal radiolocation stations protected by an 80 km radius exclusion zone. Deployment within an exclusion zone requires coordination and agreement with the earth station operator.

3.65 GHz System Deployment Map.

Today, there are just over 24,600 systems deployed in the US. Deployments also occur in exclusion zones (11%), except in the vicinity of two exclusion zones in Main and Washington State. There are also deployments in the Gulf of Mexico, in oil and gas applications. The majority of the deployed systems, 81%, are based on WiMAX, compliant with either 802.16d (fixed) or 802.16e-2005 (mobile). The remaining 19% is based on WiFi and other proprietary implementations. The main vendors are listed below with the majority of systems sold are from GE MDS (smart grid applications) and Motorola. The highest concentration of systems is in the Houston area with over 4700 deployed systems that mainly belong to the smart grid deployment by CenterPoint Energy where 3.65 GHz WiMAX-based systems are used to backhaul traffic from smart meter aggregation nodes. CenterPoint leads in the number of deployed systems with over 5400 system.

3.65 GHz Band System Vendors

Note: systems includes both base stations and CPEs.