OFDMA femtocells: A self-organizing approach for frequency assignment

Abstract

This work presents 2 novel approaches for the self-organization of Orthogonal Frequency Division Multiple Access (OFDMA) femtocells, in which the femtocell is able to dynamically sense the air interface and tune its sub-channel allocation in order to reduce inter-cell interference and enhance system capacity. In the sensing phase, these techniques make use of either messages broadcast by the femtocells or measurements reported by the users, while in the tuning phase, they provide a good solution for the frequency assignment problem.Results shows that it is recommend to use information collected at the user position (measurement reports), when devising selforganization algorithms for tuning the parameters of femtocells.

Interference Mitigation in CR-Enabled Heterogeneous Networks

“…By utilizing RBs with acceptable channel quality, the impact of frequency selected fading can be alleviated. Similarly, as all cells only utilize unoccupied RBs by neighboring cells, interference can also be rejected [5], [8], [14], [18], [20], [24], [43]- [45]. Following this concept, a particular solution known as the almost blank subframe (ABS) solution is proposed in Enhanced Inter-cell Interference Coordination (eICIC) in 3GPP LTE-Advanced [3].…”

“…By performing periodical channel measurement in UEs and reporting the measurement results to its serving BS [14], [20], [46], the serving BS can analyze and acquire the activity and the channel condition about immediate environment of the radio resource usages in neighboring cells, which facilitates the interference mitigation. However, performing measurement quite consumes power in UEs.…”

“…Based on the global energy function in (14), the local energy function of the sth femtocell can be obtained by…”

“…To tackle this issue, a multitude of efforts has been recently proposed to study the downlink spectrum-sharing problems between macrocells and small cells considering cross-tier interference mitigation [5]- [13], among small cells considering intra-tier interference mitigation [14]- [18], and both [19]- [24]. Spectrum sharing among heterogeneous cells is typically achieved via cooperation or coexistence [25].…”

Hybrid frequency allocation scheme for capacity improvement in densely deployed small cells

“…Considering the uplink capacity and interference cancelation problems in CDMA-based hierarchical networks, the uplink capacity and time-hop (TH)-based CDMA interference cancelation technology are proposed and analyzed with the outage probability constraints of macrocell and femtocell in co-channel frequency deployment scenario [16]. Furthermore, in OFDMA-based hierarchical networks, selfconfiguration-and self-optimization-based interference cancelation schemes are proposed to solve the interference problems in co-channel and orthogonal frequency allocation schemes in [17] and [18].…”