Shanya Cong

In the existing non-orthogonal multiple access (NOMA) works, ordering users depending on their distances is widely used, which can provide tractable results. However, it is not accurate in dense networks with considering the line-of-sight (LoS)/non-line-of-sight (NLoS) propagation and multipath fading. Hence, the received instantaneous signal power (ISP)-based ordering is investigated in this letter. We derive the probability of the near user in distance-based ordering being the strong user in ISP-based ordering, which is termed as the accuracy probability, and also analyze the respective coverage probabilities. The analytical and simulation results show that the accuracy probability varies with base station (BS) density and the gap between the distance and ISP-based ordering highly depends on the BS density and power allocation coefficient.

Heterogeneous networks (HetNets) are regarded as a promising approach to handle the deluge of mobile data traffic. With the co-channel deployment of small cells, the coverage and capacity of the network will be improved. However, the conventional maximum-received-power (MRP) user association scheme and cross-tier interference issue significantly diminish the performance gain provided by small cells. In this paper, we propose a novel location-aware cross-tier cooperation (LA-CTC) scheme for jointly achieving load balancing and interference mitigation in two-tier HetNets. In detail, we define an inner region for each macro base station (MBS) where the femto base stations (FBSs) will be deactivated, and thereby the users within the inner region will only be served by the MBS. Subsequently, for the users located in the outer region, the proposed scheme only uses coordinated multipoint (CoMP) transmission by two tiers of BSs to eliminate the excessive cross-tier interference suffered by offloaded users, whereas users with good locations are served directly by either a MBS or a FBS. Using tools of stochastic geometry, we derived the analytical expressions for the coverage probability and average rate of a randomly chosen user. Meanwhile, the analytical results were validated through Monte Carlo simulations. The numerical results show that the proposed scheme can improve the performance of networks significantly. Moreover, we compare the performance of the proposed scheme with that of the conventional MRP scheme, the cell range expansion (CRE) scheme and the location-aware cross-tier CoMP transmission (LA-CTCT) scheme in the literature. Numerical comparisons revealed that the proposed LA-CTC scheme outperforms the other three schemes.