Handoffs in hierarchical macro/femto networks and an algorithm for efficient handoffs

Abstract

The surest way to increase the system capacity of a wireless link is by getting the transmitter and receiver closer to each other, which creates the dual benefits of higher-quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hot spots, distributed antennas, or relays. A less expensive alternative is the recent concept of femtocells also called home base stations which are data access points installed by home users to get better indoor voice and data coverage. In macro/femto hierarchical networks, one of the biggest challenges is ensuring efficient handoffs. Here in this thesis, we first evaluated received signal strength at mobile user using different path loss models (indoor and outdoor) which is the main criterion for performing handoff. We also obtained the interference and SINR scenarios for handoff performance. Then we derived some basic handoff parameters like handoff probability, radio link failure rate, ping-pong handoff for macro/femto environment. Finally we proposed an algorithm for efficient handoff. The main idea of the proposed algorithm is to combine the values of received signal strength from a serving macro BS and a target femto BS in the consideration of large asymmetry in their transmit powers. Numerical results show that there is a significant gain in view of the probability that the user will be assigned to the femtocell while keeping the same level of the number of handoffs.