Cognitive Networks: Towards Self-Aware Networks

13.1. Introduction

In recent years, the proliferation of spectrum-based services and devices for uses such as cellular communication, public safety, wireless LAN and TV broadcast has forced society to become highly dependent on radio spectrum. This dependency and explosive growth in demand for radio resources is propelled by a host of factors: the economy has moved towards the communication-intensive service sector; the workforce is increasingly mobile; and consumers have been quick to embrace the convenience and increased effciency of the multitude of wireless devices available today.

In the United States, the Federal Communication Commission (FCC) regulates access to spectrum. These regulations have led to reservation of spectrum chunks for specific purposes; for example, 824–849 MHz and 1.85–1.99 GHz frequency bands are reserved for licensed cellular and personal communications services (PCS) and require a valid FCC license, whereas 902–928 MHz, 2.40–2.50 GHz, 5.15–5.35 GHz and 5.725–5.825 GHz frequency ranges are reserved as free-for-all unlicensed bands ^[]. This strict long-term spectrum allocation as shown in Figure 13.1 is space and time invariant and any changes to it happen under strict FCC control.

Considering the increase in demand for freely available, i.e., unlicensed radio spectrum, it is clear that the necessary radio spectrum will not be available in the future, due to the limited nature of radio resources in the current unlicensed frequency bands. Since many services ...