Near-Optimal Scheme for Cognitive Radio Networks With Heterogeneous Mobile Secondary Users

In this paper, we study the throughput and delay scaling laws for cognitive radio network with static primary users and heterogeneous mobile secondary users coexist in the unit planar region for both without base-station case and with base-station case. The primary network consists of n randomly and uniformly distributed static primary users with higher priority to access the spectrum. The secondary network consists of m = (h + 1)n^1+ϵ heterogeneous mobile secondary users with h = O(log n)1 and ϵ > 0, which should access the spectrum opportunistically. Each secondary user moves within a circular region, centered at its home-point with a restricted speed. The moving region of each mobile SU is n-α, where α is a random variable following the discrete uniform distribution with h + 1 different values, ranging from 0 to α₀(α₀ > 0). We propose a scheme which consists of routing and scheduling schemes and show that the primary network and secondary network can achieve near-optimal throughput and delay scalings if we increase the heterogeneity of secondary users. In this near-optimal condition, both the primary network and part of the secondary network can achieve constant throughput and delay scalings except for poly-logarithmic factor. Furthermore, we study the case that there are n^β uniformly distributed static base-stations (BSs) where β > 0 and propose the corresponding scheme for PUs, SUs and BSs. Finally, the theoretical results indicate that if β is large enough, BSs can improve the throughput and delay performance by relaying packets through cable backhaul.