Interference mitigation for whitespaces networks

Abstract

As the demand for spectrum increases and frequency bands become more congested especially in densely populated urban centres,  spectrum managers are following diverse approaches to sharing frequencies: using administrative methods including in band sharing,  licensing such as leasing and spectrum trading, and the unlicensed spectrum commons combined with the use of low power radios or  advanced radio technologies including ultra-wideband and multi-modal radios. When a band already licensed to an operator is shared  with others it is known as overlay spectrum sharing. For example, a spectrum band used for TV distribution in one geographical area  could be used for an application such as broadband wireless access in another area without any risk of interference, despite being  allocated on a national basis. Spectrum sharing is required when sufficient demand for spectrum exists, causing congestion, and the  technical means exist to permit different users to coincide; and other means for adjusting spectrum use and assignment have become  burdensome and costly undermining the goals of economic and technical efficiency. This paper investigates the interference mitigation  schemes that deal with the problem of coexistence between primary and reconfigurable radio networks, while avoiding cross network  interference to the primary licensed network and ensuring the expected quality of service in a network. To mitigate this interference, we  describe a simulation study of the cognitive femtocells using cognitive radio techniques. Simulation results shows that frequency bands  that are being shared by some users by maintaining geographic separation ensures strict adherence to operational constraints prevent  interference between services. Spectrum sharing typically involves more than one user sharing the same band of spectrum for different  applications or using different technologies. Dynamic spectrum access techniques enable broadband services in the TVWS spectrum  without interfering with existing broadcast and other incumbent services.