Performance Comparison of Random Subcarrier Access and Spectrum Harvesting with ARQ Retransmission and Probing Type of Cognitive Radio Networks

Abstract: In cognitive radio (CR) systems, one of the main implementation issues is spectrum sensing. This paper considers an orthogonal frequency-division multiplexing (OFDM)- based CR spectrum sharing system that assumes random access of primary network subcarriers by secondary users (SUs) and absence of the PU‟s spectrum utilization information, i.e., no spectrum sensing is employed to acquire information about the PU‟s activity or availability of free subcarriers which is termed as Random Subcarrier Access (RSA) Scheme. This paper obtains the performance of the random access scheme in terms of capacity of the subcarrier collisions by assuming an interference power constraint at PUs to protect their operation. This paper also considers a method entitled Spectrum Harvesting with ARQ Retransmission and Probing (SHARP) which is based on spectrum sharing system where the secondary pair listens to the primary ARQ feedback to glean information about the primary channel. Two varieties of spectrum sharing, named conservative and aggressive SHARP, are introduced. The performance of RSA scheme and SHARP scheme is compared.

Keywords: OFDM-based cognitive radio, random access, spectrum sharing, ARQ, average capacity.