Abstract
Heterogeneous cellular networks, due to its multi-tier topological structure, provide significant improvements in terms of increased data rates and cell coverage. However, there are important intra-tier and inter-tier interference management problem to be solved. In this paper, we model a two-tier uplink heterogeneous network, which include a macrocell and K overlaid femtocells. Meanwhile we constitute a heterogeneous configuration that each femto BS is equipped with two antennas and the macro BS is equipped with A (2 ≤ A ≤ 2 K ) antennas. We proved that the sum-DoF outer bound of the network is 4 K 2 /4 K ‒ A , and the DoF outer bound for the femtocell and macrocell is (2 K ‒ A )/(4 K ‒ A ) and A /(4 K ‒ A ) respectively. Moreover, we present the achievable scheme, which is based on interference alignment. The simulation results show that the sum rate of the whole HetNet increases as the number of macro BS’s antennas increases.
Highlights
As Heterogeneous Network (HetNet) [1] provides flexible and efficient topology to effectively improve spectral efficiency and avoid coverage holes, modern cellular network deployments are transitioning from largely homogeneous deployments to highly heterogeneous networks comprised of different low-cost low-power base station nodes (LPN) such as picocells, femtocells and distributed antenna systems [24]
The LPNs provide better quality of service (QoS) for mobile devices in comparison with a conventional one-tier cellular network, they bring a serious cross-tier interference between tier-1 and tier-2 when they share the same licensed band [5]. To both fully exploit the possible gains through HetNet deployments and control the interference between tiers, we need to utilize the differences in base station types and change the conventional single-layer homogenous networks approach to include these differences
Interference alignment, as an advanced beamforming technique has been utilized in a variety of networks, such as K user point-to-point interference channel [6], X channel [7] and conventional cellular downlink networks [8]
Summary
As Heterogeneous Network (HetNet) [1] provides flexible and efficient topology to effectively improve spectral efficiency and avoid coverage holes, modern cellular network deployments are transitioning from largely homogeneous (one-tier) deployments to highly heterogeneous networks (two-tier) comprised of different low-cost low-power base station nodes (LPN) such as picocells, femtocells and distributed antenna systems [24]. The LPNs provide better quality of service (QoS) for mobile devices in comparison with a conventional one-tier cellular network, they bring a serious cross-tier interference between tier-1 and tier-2 when they share the same licensed band [5]. To both fully exploit the possible gains through HetNet deployments and control the interference between tiers, we need to utilize the differences in base station types and change the conventional single-layer homogenous networks approach to include these differences.
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