Conventional coverage and capacity from a high altitude platform (HAP) over an extended coverage area suffer significantly from inter-cell interference (ICI), antenna beam broadening, and uneven cell loading, which results in poor edge performance. In this paper, we show how a single antenna array on a HAP can be used to mitigate against these and achieve ubiquitous coverage by forming two tiers of a homogeneous contiguous cellular structure. We propose separate algorithms that implement the two-tier architecture with many antenna beams, which are used to form cells, and associate users with an appropriate cell and tier. A user associates with the cell and tier, which offer the best carrier power-to-noise ratio (CNR) and carrier power-to-interference-plus-noise ratio (CINR) respectively. The performance of the architecture, which is evaluated using simulation, is compared with a typical one-tier architecture. The results show that the two-tier architecture achieves over 30% higher user throughput and enhances throughput fairness and edge-of-cell connectivity by centralising as many users as possible within cells compared to the typical one-tier architecture. These benefits are better exploited by ensuring spectrum orthogonality between the two tiers.

In this paper, we propose a scheme for beam-pointing from a high altitude platform (HAP) for contiguous coverage delivery within an extended service area. The scheme, which illuminates cells, considers the broadening of beams on the ground from the HAP-based antenna array. A predetermined degree of overlap is introduced between neighbouring cells to minimize user outages when moving between cells. In order to evaluate the performance of the scheme, users are randomly distributed at a density of λ users/km2over a service area of radius R. We compare the cell overlap, users' carrier-to-noise ratio (CNR), and carrier-to-interference-plus-noise ratio (CINR) with those of other cell-pointing schemes. The results show that cell overlap is better managed using our proposed schemes. In addition, the proposed scheme significantly improves user CNR and CINR, achieving a CINR improvement of 5-15dB compared with the other schemes.