13
SELF-COEXISTENCE AND SECURITY IN COGNITIVE RADIO NETWORKS
13.1 INTRODUCTION
Recent experimental studies have demonstrated that wireless spectrum suffers from overutilization in some bands and underutilization in others over different points in time and space [1]. This results in a great amount of white space (unused bands) being available dynamically that can potentially be used for both licensed and unlicensed services. It is then intuitive that static spectrum allocation may not be the optimal solution for efficient spectrum sharing and usage. In static spectrum allocation, a large number of the radio bands are allocated to the television, government, private, and public safety systems. However, the utilization of these bands is significantly low. Often, the usage of spectrum in certain networks is lower than anticipated, while other bands suffer from crisis because the demands of their users exceed the network capacity. Though it might be argued that the implementation and administration of static allocation policy is very easy, the fact remains that the current allocation policy is ineffective and the penalty trickles down as an increased cost to the end users.
Static spectrum allocation often also faces issues due to the modification in existing technologies. For example, in case of VHF and UHF bands reserved for television broadcast in the United States, allocation of 6 MHz per TV channel was based on the ...
