Interference Limit based Resource Allocation for Low Density Signature OFDM in Underlay Cognitive Radio Networks

In underlay cognitive radio, cognitive users (CU) or secondary users (SU) are allowed to use a licensed spectrum band simultaneously with primary users (PU) as long as the overall interference generated is still below PU's interference limit. To accommodate the large number of SU users and manage the interference in each subcarrier, CR system used low density signature orthogonal frequency division multiplexing (LDS- OFDM) as a multiple access scheme. LDS-OFDM allows each user to spreading their symbols on a small set of subcarriers and set the number of users that using the same resources. This paper proposes a radio resource allocation scheme for SU with respect to d e as a number of users that allowed to access subcarrier and the interference threshold required by PU. The simulation results show that the outage probability not only depend on the interference limit (I-L) determined by PU but influenced by the number of subcarriers that can be accessed by SU (d(v)) and the number of users allowed to access a resource (d(c)) as well.