Resume and Starting-Over-Again Retransmission Strategies in Cognitive Radio Networks
Sandra Lirio, A. Felipe, Genaro Hernndez-Valdez · InTech eBooks · 2011
Retransmission strategiesTwo different retransmission strategies can be used to handle interrupted secondary calls: the Resume (RR) and Start-Over-Again (SOAR) retransmission strategies.In the Resume retransmission strategy, SU transmits its information starting at the point it was preempted.That is, in this strategy the SU does not need to transmit again the information bits transmitted before its previous connection was interrupted.The Resume retransmission strategy can be easily and directly implemented when automatic repeat request-based error control protocols 1 (i.e., Stop-and-wait ARQ, Go-Back-N ARQ, Selective Repeat ARQ, Hybrid ARQ) are used as the receiver must acknowledge received packets.On the other hand, in the Start Over Again retransmission strategy each time a secondary call is interrupted, SU retransmits its information starting at the initial point no matter that some part of its information was transmitted in its previous connection.Contrary to the Resume strategy, the Start Over Again retransmission strategy does not require a control protocol and, therefore, it is simpler.Under the assumption that service (or call holding) time for SU calls is negative exponentially distributed, authors in (Tang & Mark, 2007;Tang & Mark, 2008), (Tang & Mark a; 2009) have developed system level models for the performance evaluation of cognitive radio networks with the RR strategy.In a related work (Tang & Mark, 2009), the RR strategy is analyzed under the assumption that service time of SUs is phase-type distributed.However, the RR strategy is neither evaluated under different traffic conditions nor the effect of characteristics of the SU service time is investigated.To the best of the authors' knowledge, the performance of cognitive radio networks with the SOAR retransmission strategy has been neither analyzed nor evaluated in the literature.Therefore, the performance of the RR and SOAR strategies has not been compared either.All these important tasks are addressed in this Chapter.