Capacity Enhancement Using Reversed-Pair TDD Frame in OFDMA Femto-Cell Systems

Demanding on higher data rate in wireless communications, femto-cell has been proposed to implement that with a low cost. The femto-cell can be realized by deploying a femto-base-station connected to the core network via a wired-backhaul. Through the wired-backhaul, a downlink and uplink data packets are delivered to the femto-base-station and the core network, respectively. Although the femto-cell with a low transmission power has a small cell coverage, co-channel interference problem between macro-cell and femto-cell has been an important research issue to deploy the femto-cell in the real world since the femto-cell reuses the macro-cell spectrum. As a solution to the co-channel interference problem, we propose a new time-division-duplex (TDD) frame structure called reversed-pair frame (RPF). The RPF consists of two TDD frames with a reversed order of downlink and uplink. Using the RPF and a wired-backhaul-delivered downlink data, capacity enhancement can be achieved through a simple interference mitigation process. We evaluate the performance of the RPF through analyzing the capacity of the two-user case, which is applied to multi-user case. The results show that adopting the RPF in a OFDMA femto-cell systems greatly enhances the uplink capacity of both the macrocell and the femto-cell, and even downlink capacities of them than using the conventional TDD frame.