Self-organizing Femtocell Networks Research Articles

A Consensus-Based Coverage Algorithm For Self-Organizing Femtocell Networks

In this letter, a consensus-based distributed coverage algorithm is proposed for self organization in two-tier femtocell networks. One key feature of the algorithm is that it achieves fairness among users in terms of signal quality without relying on any predefined target values. The stability of the proposed algorithm is investigated using quadratic Lyapunov functions, which also allow us to analyze its convergence rate properties. The simulation results are not only in agreement with the theoretical analysis, but also demonstrate significant improvement in terms of overall network performance.

Handling interference in self-organizing femtocell networks through frequency-polarization diversity

The next generation heterogeneous networks are expected to offer higher data-rate and better QoS to the customers by leveraging smaller cells like femtocells and making use of orthogonal frequency division multiple access. However, uncoordinated dense deployment of femtocells in macrocell network pose unique challenges involving cross-tier interference and resource management which results in significant degradation of the system performance. As part of addressing these challenges for the successful integration of both technologies, this paper proposes the deployment of a self-organizing femtocell network that employs an opportunistic smart frequency reuse technique ---cross polarized complementary frequency allocation (CPCFA). It exploits the frequency and polarization diversity to mitigate interference in two-tier femto-macro networks. In this work, a strategy combining the adoption of reverse frequency allocation and orthogonal polarized transmission is analyzed as a potential solution for maximizing spectral efficiency and minimizing interference in the existing heterogeneous networks. Focus of the current work is on downlink transmission where the traffic is high and the deployment of femtocell is more beneficial. The results of analytic and simulation studies prove that CPCFA increases the scope for an easily implementable, remarkable opportunity in the context of two-tier femto-macro network that can substantially increase the system capacity as well as cell coverage without additional network complexities.

COD: A Cooperative Cell Outage Detection Architecture for Self-Organizing Femtocell Networks

The vision of Self-Organizing Networks (SON) has been drawing considerable attention as a major axis for the development of future networks. As an essential functionality in SON, cell outage detection is developed to autonomously detect macrocells or femtocells that are inoperative and unable to provide service. Previous cell outage detection approaches have mainly focused on macrocells while the outage issue in the emerging femtocell networks is less discussed. However, due to the two-tier macro-femto network architecture and the small coverage nature of femtocells, it is challenging to enable outage detection functionality in femtocell networks. Based on the observation that spatial correlations among users can be extracted to cope with these challenges, this paper proposes a Cooperative femtocell Outage Detection (COD) architecture which consists of a trigger stage and a detection stage. In the trigger stage, we design a trigger mechanism that leverages correlation information extracted through collaborative filtering to efficiently trigger the detection procedure without inter-cell communications. In the detection stage, to improve detection accuracy, we introduce a sequential cooperative detection rule to process spatially and temporally correlated user statistics. Numerical studies for a variety of femtocell deployments and configurations demonstrate that COD outperforms the existing scheme in both communication overhead and detection accuracy.

Distributed joint resource and power allocation in self-organized femtocell networks: A potential game approach

Femtocells, which are widely deployed within a macrocell, are considered to be a novel technology that leads to the escalation of indoor coverage and capacity. However, due to lack of coordination between the femtocell and the macrocell, designing a distributive resource and power allocation is a challenging task. In this study, a potential game (PG)-theoretic approach is proposed for joint resource and power allocation (JRPA), which is demonstrated to exhibit unique Nash Equilibrium. Specifically, femto-base stations, which are considered as the players of the PG, learn the strategies in terms of resource and power allocation by taking into account the interest of other entities. To this end, the utility function of players is designed such that it minimizes the impact interference and the satisfaction for improving the femtocell capacity, without jeopardizing the macrocell performance. Precisely, the utility function incorporates all the sources of interference such as co-tier and cross-tier, and also the reward of each player in terms of capacity. The proposed PG-based JRPA is solved by employing the better response dynamics, which selects the resources and the power levels by utilizing a particle swarm optimization-constriction factor model. The performance of PG-based JRPA is analyzed in regard to average femtocell capacity and system capacity. Additionally, two different traffic cases are considered: high load traffic and low load traffic. For the sake of comparison, random allocation is employed. Simulation results are carried out in terms of the performance metrics, which includes convergence, min-max capacity, varying resource blocks, femtocell density and fairness. The results illustrate the superior performance of the proposed PG in terms of the aforementioned performance metrics.

On-Demand Resource-Sharing Mechanism Design in Two-Tier OFDMA Femtocell Networks

Femtocells are a promising technology to improve network performance with short-range, low-power, and cost-beneficial small base stations. There will be many prospective benefits by applying the femtocell technique to wireless communication standards such as the Global System for Mobile Communications (GSM), WiMAX, and Long-Term Evolution. This paper studies two main design issues in orthogonal frequency-division multiple-access (OFDMA) femtocell networks, i.e., resource sharing and femtocell access control. Unlike other previous works, our presented analysis encompasses modeling wireless users' selfish characteristic and private traffic information. In addition, this provides a more comprehensive perspective on self-organizing femtocell networks, where users optimize their performance in a distributed manner. Our contributions are threefold: 1) We design a resource allocation mechanism that gathers selfish users' true private traffic information. 2) The proposed mechanism achieves efficient and fair resource sharing. 3) Based on the proposed mechanism, we create incentives for subscribers to share their femtobase stations with general users. This further improves the overall system performance.