Venkatesh T.G.

Cognitive radio networks (CRN) rely upon dynamic spectrum access that allows spectrum to be used efficiently. The role of the medium access control (MAC) protocol in CRN is to distribute efficiently the spectrum among the users. We propose a MAC protocol for cognitive wireless local area network (WLAN) that allows an unlicensed secondary user (SU) to opportunistically access and transmit data on the licensed channel owned by the primary user (PU). The proposed MAC protocol is an adaptation of IEEE 802.11 distributed coordination function. Extensive performance evaluation of the cognitive WLAN MAC protocol has been carried out as follows. First, a Markov chain model of the cognitive WLAN MAC protocol is developed. By solving our model we derive saturated throughput, packet delay, channel busy probability, conditional collision probability of SU, and interference to PU. Extension of our model for the case of multiple PUs under lightly loaded condition is also carried out. Further, we analyze the energy efficiency of the cognitive WLAN MAC protocol. We calculate the optimal sensing time interval for the SUs and the corresponding sensing energy incurred by the SUs. Effect of imperfect channel sensing on the performance of the proposed protocol is investigated. We validate our model by comparing the analytical results with simulation.

We present an analytical model for the access during the Service Periods (SP) of the IEEE 802.11ad Hybrid Medium Access Control protocol. As a performance measure of this protocol, we derive the worst case and average delay faced by the SP packets. We show that as the arrival rate of the SP packets increases, the delay increases linearly till a point, beyond which it grows exponentially. Further, we extend the model to variable length of beacon interval, and random allocation of SPs to the nodes. We show how a network designer can do optimal allocation of the SP and the CBAP duration to achieve a tradeoff between SP delay and CBAP throughput. We further extend our analysis for the case of heterogeneous system. Our analytical results are compared with simulation and the results show a good match.

Recent advances in physical layer technologies, allows simultaneous reception of multiple packets by a node. This promising technology is called Multi-Packet Reception (MPR). In this paper, we analyze a modified IEEE 802.11 DCF based medium access control (MAC) protocol for Wireless Local Area Network (WLAN) with nodes having MPR capability. Our protocol modifies the backoff mechanism of the IEEE 802.11 DCF so that the backoff process quickly adapts to the prevailing traffic conditions while leveraging MPR. A Markov chain model for the backoff process of the nodes with MPR capability has been derived. Further a Markov chain model to capture the state of the MPR channel has been derived. Solving the Markov chains for stationary probabilities, we derive the saturated throughput and energy efficiency of our protocol. Effect of the number of nodes, MPR capability, contention window size, and sensing errors on the saturation throughput has been investigated. Proposed analytical model has been validated through extensive simulations. Our investigation has the potential to aid in the development of next generation WLAN MAC protocol.