β-PSR: A Partial Spectrum Reuse scheme for two-tier heterogeneous cellular networks

In this paper, we consider a Partial Spectrum Reuse (PSR) scheme, namely “β-PSR”, to improve spectrum efficiency of two-tier heterogeneous cellular networks, in which each micro Base Station (BS) occupies a uniform portion β of the whole system spectrum randomly and independently. We analyze the optimal PSR factor β to minimize service outage probability, which is not in an explicit form. Then a closed-form limit of the PSR factor is derived when the ratio of the user data rate requirement over the system bandwidth is approaching zero. This limit is an explicit function of the traffic intensity, the macro/micro BS density and their transmit power. Our numerical results also show that for most current rate requirements, the optimal PSR factor is well approximated by our derived limit. This motivates the design of an adaptive PSR scheme with near-optimal performance, which only depends on statistical network information.1.