Throughput/delay performance of secondary user in spectrum underlay

In this paper, we propose a scheme to evaluate throughput delay performance of secondary users (SUs) in a cognitive radio (CR) CDMA network. Specifically, we develop a simulation test bed for analyzing performance of a SU in a single cell, where both SUs and primary users (PUs) are present. CR users or SUs belong to an infrastructure less ad hoc network, which coexists with a primary radio network (PRN), forming pair wise links. We assume spectrum underlay type of spectrum sharing, where SUs transmit in presence of PUs maintaining a predefined interference limit for PRN. A SU transmits packetized data for its corresponding receiver. A stop and wait ARQ protocol at MAC layer has been assumed for packet transmission. Further, we evaluate performance of a SU in terms of retransmission rate, packet error rate. Effects of various network and channel parameters such as cell radius, standard deviation of shadow fading on the above mentioned performance metrics are indicated.