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AWS Auctions Spawn Spectrum Shuffle

By Asad Zoberi, microwave area product manager, Radio Frequency Systems

The recently concluded 2006 auctions of advanced wireless services (AWS) spectrum will create specific backhaul challenges. Although the “new” 1700 and 2100 MHz spectrum will provide bandwidth for commercial mobile phone carriers hoping to deploy third-generation (3G) services, the incumbents already using these bands for wireless backhaul applications must quickly find new backhaul routes in order avoid disruption of existing services.

The spectrum being auctioned by the Federal Communications Commission (FCC) comprises the 1710-1755 MHz band, currently used by federal government organizations, and the 2110-2150 MHz band, allocated to nongovernment organizations.

The new licensees, who will foot the bill for backhaul relocation, are likely to want to liberate the spectrum right away. There could even be a measure of transitional frequency sharing, providing there's no interference generated. Whatever the case, speed of deployment will be a key factor in the choice of a new backhaul mechanism.

Backhaul Case-by-Case

Incumbents have several backhaul options: lease of existing T1 lines, deployment of fiber networks, utilization of existing microwave backhaul systems in neighboring bands, or relocation of wireless backhaul services to different bands. Most likely, these options will be considered on a case-by-case basis. Each link will be assessed in terms of interference, available infrastructure and available capacity.

the options, microwave radio links remain the most flexible. Although T1 lines present a speedy solution, they incur ongoing leasing costs that dramatically increase overall cost of the system. Fiber networks are fast and high capacity, but are difficult and expensive to deploy, especially over rugged terrain, and are more susceptible to natural disasters. Microwave links, on the other hand, can cover great distances without incurring extra cost, can be deployed quickly, and offer payback periods of as little as two years. Furthermore, with microwave backhaul, users have total control of the system.

The frequency bands specified by the FCC for microwave backhaul relocation are illustrated in Figure 1. Federal government incumbents currently using the 1710-1755 MHz band can opt to use existing systems in the 1750-1850 MHz band or deploy new systems in the 4 or 7 GHz bands. Similarly, nongovernment incumbents (2110-2150 MHz) can use existing 2450-2483 MHz systems or move to the 6, 10, 11 or 18 GHz bands. The decision lies in the desired application.

Digital Opportunity

Although it might be faster and more cost-effective to use existing microwave antenna systems, they might already be capacity limited or consist of old equipment. This is really a huge opportunity to upgrade to digital technology, where capacity is much less an issue. The 4, 6 and 7 GHz bands are, for the most part, ideal for high-capacity, long-distance microwave links; while the higher frequency bands are more applicable for links over medium or short distances.

Although incumbents of the 1700 and 2100 MHz bands are still confronted by a lot of unknowns, there are already many solutions available to meet their backhaul relocation needs.

For more information contact TESSCO at
800-472-8063 or email us today.

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