Abstract
Femtocell technology has been gaining popularity as an inexpensive means of enhancing cellular coverage and capacity. However, under co-channel deployment—expected to be commonplace due to high spectrum costs—femtocells may incur harmful interference to existing macrocells, and vice versa. To alleviate this problem, This paper proposes a new architecture called HandOver-driven Femtocell Interference Management (HO-FIM) that offloads macrocells by handing macrocell users over to “hybrid-access” femtocells that allow the access of both subscribed and unsubscribed users. This use of handovers adds a new degree-of-freedom for solving the interference problem, thus overcoming the capacity limit of the existing approaches that exploit radio resource coordination only. A new challenge associated with this approach is how to minimize handovers while reaching a desired system condition due to the inevitable service interruptions that accompany handovers. This paper proposes to overcome this challenge by triggering handovers only when needed and, once triggered, to find an optimal sequence to reach a target system condition with minimal handovers. This paper designs a greedy per-user control algorithm that has a fine control granularity and thus enables convergence to an optimal solution. The in-depth evaluation of the paper shows that HO-FIM improves the service quality of both macro- and femtocell users; in an example simulation scenario, HO-FIM is shown to improve the signal-to-interference and noise ratios (SINRs) of macro- and femtocell users by up to 23.3 and 2.9 dB, respectively, on average, compared to the case of no handovers.
Highlights
There has been a growing interest in femtocell technology, which promises cost-effective enhancement of indoor network coverage and capacity to meet increasing demands for bandwidth-hungry data services within home or enterprise environments [1]
This paper proposes to meet this challenge by triggering handovers only when absolutely needed and, once triggered, to find an optimal handover sequence to reach a target system condition with minimal handovers
Thirty macrocell users and thirty femtocells are distributed in the macrocell
Summary
There has been a growing interest in femtocell technology, which promises cost-effective enhancement of indoor network coverage and capacity to meet increasing demands for bandwidth-hungry data services within home or enterprise environments [1]. A significant capacity improvement is expected to be achieved with femtocells via their enhanced spatial reuse of spectrum resources. A key challenge faced by femtocell technology is how to protect macrocell user services from femtocell interference when macro- and femtocells are allocated the same frequency band for economic reasons, called co-channel deployment, while exploiting spatial reuse of channel resources within femtocells. Co-channel deployment of macro- and femtocells is expected to be commonplace due to the high cost of the licensed spectrum. Under this co-channel deployment, transmissions within femtocells may cause harmful interference to user services within macrocells, and vice versa, as reported by
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