LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Frequency Reuse

Cellular networks have had always to deal with the interference-capacity tradeoff. Allowing every cell to use all the available spectrum bands boosts the overall system capacity. At the same time, such setup also raises the interference experienced by the cell-edge users to intolerable levels. Consequently, the QoS requirements of these users will not be guaranteed, worsening the overall system fairness. To strike a balance between these two, the notion of Frequency Reuse (FR) is used. In FR, the set of available bands is equally divided between a few neighboring cells, referred to as a cluster. As a result, the system capacity is kept at acceptable levels while the inter-cell interference is significantly reduced.

Nevertheless, full FR, where the entire available spectrum bands are allocated to every cell, remains an attractive option provided that some interference mitigation mechanism is adopted. In fact, full FR can also be applied among the different sectors of the same cell. However, this scenario is prone to higher levels of inter-sector interference especially when the radiation patterns of the different sectors' antennas overlay. Unfortunately, FR cannot be fully realized in practice since inter-cell interference is unavoidable. However, the cell edge problem can be efficiently mitigated through fractional FR. Briefly described, fractional FR divides the available spectrum into a number of segments. Full FR is applied to one of these segments at the cell-center, ...