TABLE OF CONTENTS Sai Shankar, N
Corporate R&D Systems Engineering,
Qualcomm Incorporated,
San Diego, CA 92121, USA
Cognitive radio devices have been considered as a key technology for next-generation of wireless communication. These devices can opportunistically utilize the wireless spectrum to achieve better individual device/user performance and improve the overall spectrum-utilization efficiency. However, allowing opportunistic use of the wireless spectrum creates new problems such as peaceful coexistence with other wireless technologies as well as understanding the influence of interference that each of these networks can create. In this chapter we model the efficiency of the cognitive radios from the Medium Access Control (MAC) analytically and study the improvement that cognitive radios can get compared to conventional radios. Then we consider the effect of peaceful coexistence with different types of cognitive radios and also consider a simple spectrum sensing protocol which is a function of the primary utilization and required opportunity.
Wireless networks are regulated today by government agencies wherein spectrum is allocated to a particular application. Such a static allocation has resulted in immense spectrum crunch in some parts of the spectrum and non-usage in some other parts of the spectrum. As a result the average spectral utilization is very low over most of the bands. Since spectrum is a natural resource, any wastage in spectrum impedes the growth of wireless technologies and augments the need for opportunistic usage of spectrum. Cognitive radios are seen as a way to mitigate this low spectral usage. These radios sense the medium and...
