Power and subcarrier allocation for OFDMA femto-cell based underlay cognitive radio in a two-tier network

Abstract

In this paper, the problem of subcarrier allocation, and power allocation is addressed in an OFDM-based two-tier femto-cell network comprising of a conventional macro-cell and multiple femto-cells. The macro-cell users near the femto-cell causes significant interference to the femto-cell users as well gets interfered by the femto-cell transmissions. We present a subcarrier and power allocation method in underlay femto-cell network while keeping the total interference to macro-cell users under acceptable levels. We maximize the multiple femto-cell users throughput by jointly allocating subcarriers to users within a femto-cell, and also power allocation, under the constraints of cross-tier interference between macro-cell and multiple femtocells as well as interference among femto-cells. Then, based on this subcarrier and power allocation the performance of the twotier network is analysed with capacity as the performance metric.

On the Optimisation of Practical Wireless Indoor and Outdoor Microcells Subject to QoS Constraints

“…Along with a number of advantages achieved with cell division approaches, the deployment of microcells raises a critical issue in cellular networks when the overlapping frequencies of different cells in the same area cause considerable interferences [13,14]. The overlapping coverage also implies the wastage of resources, whereas a smaller number of cells could be used to maintain the same coverage area.…”

Downlink interference minimization in cooperative cognitive LTE-femtocell networks

“…In fact, the interference problem can be extremely intractable in a dense deployment scenario due to the lack of spectrum resources. Given that, various interference management strategies have been proposed to address this issue including for instance, collaborative resource allocation [7], fractional frequency reuse (FFR) [8,9], directional beamforming [10], cognitive radio approach [11], and power control [12][13][14][15][16][17]. Among variety of methods, power control has been extensively researched and used as an effective interference mitigation solution for both cross-tier and co-tier interference.…”

“…In [16], resource allocation in open access OFDMA femtocell networks has been studied, while a new resource allocation method is proposed to reduce cross-tier interference and improve performance of both neighboring macrocell users and femtocell users. In [17], a subcarrier and power allocation method has been presented to manage cross-tier interference in underlay femtocell networks. Basically, these papers only take the interference power as a constraint rather than an optimization objective.…”

“…In that case, they may not be applicable when the situations vary. Moreover, [15,16], and [17] all tackled power control problem in a distributed manner due to the self-organizing feature of femtocell networks, and they all involved CR technology to mitigate the interference efficiently.…”

“…Moreover, the interference threshold varies a lot under different circumstances, which means that the power allocation algorithms taking the interference as a constraint may be not very effective in a more realistic setting. Additionally, most prior studies [14][15][16][17] address either cross-tier or co-tier femtocell interference in isolation under the assumption that the other kind of interference is already well resolved. In this paper, a new interference mitigation scheme is presented to address both co-tier and cross-tier interference problem for future cognitive LTE-femtocell networks.…”