Femtocell Network Synchronization

Presently, femtocell technology is emerging for cellular wireless networks, which have rapidly engrossed the cellular industry. The main advantage of femtocell to the mobile operators is a reduction of cost and an improvement of the signal quality in indoor coverage, which is also considered a possible path to the Fixed–Mobile Convergence (FMC) goal. Femtocell extends network coverage and delivers high-quality mobile services inside residential and business buildings through broadband networks (i.e. ADSL). Femtocell Access Points (FAP) or Home Base Stations (HBS) are intended to serve small number of users (i.e. 4 users) and cover about 30-square meters, similar to existing WiFi access points. However, femtocell introduces new challenges to the telecom industries in terms of handoff between femto and microcells, interference management, localization, and synchronization. Among all of these challenges, synchronization is considered as the cornerstone for the femtocells to function properly. The problematic issue in femtocell synchronization is that all the data and control traffic travels through an IP broadband network. The IP broadband network is usually owned and managed by a third party and not by the mobile operator which can complicate the synchronization. Unsynchronized FAPs may cause harmful interference and wrong handover dictions. In this chapter, the authors investigate and overview the current femtocell synchronization techniques and make comparisons between them. Possible improvements and recommendations for each method have been identified. Future research areas and open issues are also discussed.