Mobility management and eICIC in LTE femtocells
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LTE-Long Term Evolution was proposed in Release 8 by Third Generation Partnership Project (3GPP) with a new Radio Access Network (RAN) and an Evolved Packet Core (EPC) Network to provide a smooth migration to 4G network. The number of mobile subscribers and data usage have increased exponentially since the roll-out of LTE because of new higher capacity LTE air-interface. This has created new challenges for the network operators to provide a satisfactory quality of service to the mobile users especially in indoor scenarios. One solution to provide better indoor user experience in a cost effective manner is use of femtocells which were introduced in 3GPP LTE, Release 8. Femtocells are short ranged indoor small cells, which share the same spectrum with macrocell and could have a limited user access. Higher data rate, improved indoor coverage, QoS and longer battery life could be achieved with the deployment of femtocells. Nonetheless, the plug-and-play capability and lower cost of these small cells pose huge interference problems in uplink and downlink when installed in dense urban areas and in an unplanned way. Interference management and handover are two important factors to be considered while implementing LTE network with femtocells. The use of hard handover in 3GPP LTE and LTE-A systems coupled with the absence of a direct signaling interface between macrocell and femtocell may cause call drops and delay in mobility management. The objective of this research is to address the challenges posed by handover performance and interference mitigation in LTE system with femtocells. In this work, a speed based handover algorithm is proposed, simulated in LTE-SIM and optimized by introducing Almost Blank Sub-Frames (ABSF) and Cell Range Expansion (CRE) interference coordination schemes. Simulation results show that, better user experience can be achieved in terms of delay, fairness, reduced number of call-drops while maximizing the throughput.
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