Power control in two-tier femtocell networks

Abstract

In a two tier cellular network -comprised of a central macrocell underlaid with shorter range femtocell hotspots -cross-tier interference limits overall capacity with universal frequency reuse. To quantify near-far effects with universal frequency reuse, this paper derives a fundamental relation providing the largest feasible cellular Signal-to-Interference-Plus-Noise Ratio (SINR), given any set of feasible femtocell SINRs. We provide a link budget analysis which enables simple and accurate performance insights in a two-tier network. A distributed utility-based SINR adaptation at femtocells is proposed in order to alleviate cross-tier interference at the macrocell from cochannel femtocells. The Foschini-Miljanic (FM) algorithm is a special case of the adaptation. Each femtocell maximizes their individual utility consisting of a SINR based reward less an incurred cost (interference to the macrocell). Numerical results show greater than 30% improvement in mean femtocell SINRs relative to FM. In the event that cross-tier interference prevents a cellular user from obtaining its SINR target, an algorithm is proposed that reduces transmission powers of the strongest femtocell interferers. The algorithm ensures that a cellular user achieves its SINR target even with 100 femtocells/cell-site, and requires a worst case SINR reduction of only 16% at femtocells. These results motivate design of power control schemes requiring minimal network overhead in two-tier networks with shared spectrum.

Interference Mitigation in CR-Enabled Heterogeneous Networks

“…Consequently, two nodes physically locating closely to each other do not suggest severe interference to/from each other if a small transmission power is adopted in both nodes. Such concept motivates considerable efforts [10], [12], [17], [40]- [42] to avoid harmful interference to the victim by controlling the transmission power in the aggressor based on the physical distance to the victim in the HetNet. However, in state-of-the-art cellular networks such as LTE and LTEAdvanced, adaptive power control is only applied in uplink communications, while a fixed power level is adopted by downlink communications to avoid complexity in BSs.…”

UMTS Multi-Service Uplink Capacity and Interference Statistics of Femtocells

“…To quantify near-far effects with universal frequency reuse, work [11] derived a fundamental relation providing the largest feasible cellular Signal-toInterference-Plus-Noise Ratio (SINR), given any set of feasible femtocell SINRs. It provided a link budget analysis which enables simple and accurate performance insights in a two-tier network.…”

Investigation on Power Control Algorithm in Joint Control Method of Autonomous Cell Association and Power Control for Heterogeneous Networks

“…In [11], both centralized and distributed solutions are proposed to achieve the target signal-to-interference plus noise ratio (SINR). In [12], a game-theoretic method is applied to distributed SINR adaptation. In [13], a distributed transmission power control algorithm with Particle Swarm Optimization is developed to ensure the target SINR.…”