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RTCP CRAHN: A Renovated Transport Control Protocol for Cognitive Radio Ad Hoc Networks

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Cognitive Radio networks take into consideration about the users to transmit in the licensed spectrum bands, as long as the capability of the licensed User’s band is not degraded. Meanwhile, variation in vacant spectrum with time and frequent spectrum sensing undertaken by the cognitive radio users has a noticeable effect on the upper layer protocol capabilities, such as at the transport layer. During the allotment of unlicensed users there occurs a scheduling problem which increases the delay. This paper investigates the scheduling problem, and proposes RTCP CRAHN, a TCP-friendly protocol. A scheduling algorithm is being proposed to decrease the delay and increase the throughput. An analysis of the expected throughput in TCP CRAHN is provided, and simulation results reveal significant improvements by using our approach.
Keywords: Cognitive radio, scheduling, licensed user, spectrum sensing, TCP
New wireless technologies are rapidly permeating all aspects of commercial and social life, thus ever increasing the demand for higher bandwidth availability under heavy traffic loads. These technologies must co-exist in the same RF spectrum in a non-interfering manner. The prevailing policy for managing this coexistence of multiple wireless technologies in the RF domain is to statically allocate the available spectrum. A static allocation separates different RF services in frequency, for the purpose of alleviating interference and contention, while providing quality of service. All useful spectrums from 3 KHz to 300GHz are already licensed for exclusive use to various entities with only a very small portion of it left for unlicensed use. Because the spectrum is already allocated, new wireless technologies find it increasingly hard to operate in unlicensed bands, where they face significant contention and interference from other services. This situation is typically termed as spectrum scarcity, referring to the unavailability of any useful spectrum bands that can be allocated. However, studies of the spectrum scarcity problem by various regulatory bodies around the globe, including the Federal Communication Commission in the United States of America and Of Com in the United Kingdom have shown that this problem is the artifact of the spectrum management policy. Further, these studies indicate the under utilization of the already allocated spectrum. In fact, according to the FCC, the temporal and geographical variations in the utilization of the assigned spectrum range from 15% to 85% the signal strength distribution over a large portion of the wireless spectrum. Defined radios, also known as Cognitive Radios, named due to their sensing and adaptability capabilities. According to a CR is a radio that can change its transmitter parameters based on interaction with the environment in which it operates.


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