International Journal of Computer Applications (0975 – 8887) Volume 27– No.4, August 2011 1 Handoff Management in Green FEMTOCELL Network K.Sethom Ben Reguiga Systel Lab, University of Carthage Tunisia F. Mhiri Systel Lab, University of Carthage Tunisia R.Bouallegue Systel Lab, University of Carthage Tunisia ABSTRACT Integrated femtocell/macrocell networks, comprising a conventional cellular network overlaid with femtocells, offer an economically appealing way to improve coverage, quality of service, and access network capacity. The key element to successful femtocells/macrocell integration lies in its self- organizing capability. Provisioning of quality of service is the main technical challenge of the femtocell/macrocell integrated networks, while the main administrative challenge is the choice of the proper evolutionary path from the existing macrocellular networks to the integrated network. In this paper, we propose a new Autonomic Architecture with self organizing capabilities based on the election of a Femtocell cluster Head (FH) for each group of Femtocell APs. The FH will be responsible to dynamically adjust the network overall coverage to save FAP energy and provide better QoS to users. Further it uses an advanced decision algorithm for intelligent handovers. General Terms Wireless Networking, Algorithms. Keywords Femtocells, Indoor Wireless Coverage, Self-Organizing Capability, Handoff, interference. 1. INTRODUCTION Femto-access points (FAPs) are low-power, small-size home- placed Base Stations (also known as Home NodeB or Home eNodeB) that create islands of increased capacity in addition to the capacity provided by the cellular system. These areas of increased capacity are referred to as femtocells. Femtocells operate in the spectrum licensed for cellular service providers. The key feature of the femtocell technology is that users require no new equipment (UE). Among the benefits of femtocell are low-cost deployment, reduced transmission power, backward compatibility with the macrocellular technology, portability of devices, and scalable deployment. Due to an interest from operators (such as the NGMN (Next Generation Mobile Network) Alliance) and standardization bodies (such as 3GPP, Femto Forum, Broadband Forum, 3GPP2, IEEE 802.16m, WiMAX Forum, GSMA, ITU-T, and ITU-R WP5D), integrated femtocell/macrocell is expected to be a major part of the IMT-Advanced network architecture [1]. From the wireless operator point of view, the most important advantage of the integrated femtocell/macrocell architecture is the ability to offload a large amount of traffic from the macrocell network to the femtocell network. This will not only reduce the investment capital, the maintenance expenses, and the operational costs, but will also improve the reliability of the cellular networks. The provision of QoS in femtocellular networks is more difficult than for the existing macrocellular networks due to the large number of neighboring FAPs and the possible interference conditions among the femtocells and between macrocells and femtocells [2]. The QoS of femtocellular networks is influenced by procedures such as resource allocation, interference management, handover control... From among the many QoS issues, we propose hereafter a solution for power and handoff management in femtocell networks based on a distributed and adaptative algorithm between different cluster heads. 2. THE CLUSTER ARCHITECTURE The power and resource allocation in femtocell environment is complex [3]. For that purpose, we propose a new architecture based on the “Femtocell Cluster” concept. Each group of FAPs will form a cluster and a FemtoHead has to be elected. The Head will act as the manager of the cluster. Fig. 1. Femtocell Cluster Architecture The Femtocell network will be organized in clusters as illustrated in the figure Fig. 1. FAPs communicate together by wired links. Otherwise, in case of outages, wireless transmission is employed. This method has several advantages: o Traffic in the backbone will be reduced. o It can also optimize the overall coverage to reduce the power, the resource allocation and the unwanted Handover on floor. o It can cover a floor area with support for soft handover Users can access the network according to three priority levels; L1, L2, and L3: o L1 which is the higher one aims to identify the indoor owner of the Femtocell AP. o L2 for users belonging to the current Femtocell provider but not connected to their indoor FAP. o And L3 for any external user. Cluster Head