Lightweight Inter-Cluster Synchronization Scheme for Femtocell Network

Abstract

A femtocell is a small cellular base station recently developed which designed for use in residential or small business environments. Femtocell technology has drawn considerable attention as a cost-effective mean to improve cellular coverage and capacity. Data loading and offloading to the macro Base Station (mBS) is supported through internet backhaul (IP broadband network) which exhibits the uniqueness of this technology. However the IP broadband network is usually owned and managed by third party and not by the mobile operator, which complicated the synchronization. Synchronization is one of the most significant issues in femto-cellular networks to guarantee an acceptable clock offset and skew, which leads to severe interference between femtocell BSs and/or between femtocells BS and macrocell BSs, where both are working in same frequency under a licensed spectrum. Recently some existing algorithms and techniques have been developed in order to synchronize the clocks, and one of them (more recent) MS-Assisted Receiver-Receiver Time Synchronization Strategy for femtocell. But this strategy is not fully covered in all situations if there has no Mobile Station for a long time in any of fBS network and make network overhead by generating the message flooding for a large number of fBS node. In this research, lightweight synchronization scheme is proposed which functions through intra-cluster and inter-cluster synchronization scheme and added between them as enhancement intermediate nodes selection if the Cluster Head cannot see neighbor CH and by using the Hybrid Wireless Mesh Protocol (HWMP) to select one intermediate node, and so we get the best way to access neighboring CH to update clocks and synchronize the clusters. The proposed scheme provides high scalability and works in a decentralized manner which can support a large number of fBS networks with a satisfactory performance level in term of synchronization accuracy. The proposed lightweight inter-cluster synchronization scheme is compared with the MS-Assisted Receiver-Receiver time synchronization strategy for femtocells. The analytical results show that synchronization accuracy can be achieved up to 60% higher than MS-Assisted Receiver-Receiver time synchronization strategy for femtocells.