From Proposition 1, Proposition 2, and Remark 4, it is evident that the coverage probability for both D2D and cellular tiers, and consequently the network ASR and EE, depend on the ratio of P d and P c.
Some results concerning the asymptotic behavior of the batteries are derived in Section 5. Simulation results are presented in Section 6, and finally, conclusions are drawn in Section 7. Let us consider a Downlink (DL) cellular multi-tier Single-Input Single-Output (SISO) system composed of several BSs.
To fully exploit the network capacity, the HCN is modeled as a K-tier cellular network where each tier's base stations (BSs) have different properties.
In a multi-tier cellular communication system, the interference from one tier to another, denoted as cross-tier interference, is a limiting factor for the system performance.
In order to cope with the cross-tier interference in two-tier cellular networks, interference mitigation schemes by employing dynamic radio resource management (including resource partitioning, allocating, and scheduling), power control, handover, cognitive radio have been reported.
Consider the case when the inter-cell user association is employed in a N-tier cellular network which consists of N spatially and spectrally coexisting tiers, and each tier is distinguished by its transmit power, cell density, and data rate [29].
Some analysts said they were worried that tighter margins in the cellphone unit and stiff competition in lower to middle tier cellular handset market could upset the company's noteworthy turnaround in the last few years.
Nevertheless, efficient two-tier power control and resource allocation faces several additional design challenges compared to their single-tier cellular counterparts.
Finally, we have considered only the time-domain interference management scenario for two-tier cellular networks without CA. However, it was demonstrated in [6] that the overall throughput performance of a two-tier network with CA is significantly improved if joint interference management and cell association is performed in both time and frequency domains.
Figure 1 Cell structure for two-tier cellular network.
