Capacity Increase of Multi-hop Cellular WLANs Exploiting Data Rate Adaptation and Frequency Recycling

The use of intermediate terminals for relaying traffic in infrastructure based wireless systems promises improvements in capacity, energy efficiency and coverage. This paper studies the possibility to increase capacity using intermediate mobile terminals as relayers, especially when using a second frequency to perform relaying in addition to a cell’s primary frequency. This second frequency is obtained by “recycling” it from neighboring cells. These recycled frequencies are used at a reduced transmission power only in the interior of the cell, close to the access point. We show the trade-off between increased transmission parallelism in one cell and increased interference from other neighboring cells. We present algorithms that solve the two-frequency relaying problem, combining routing, scheduling and data rate adaptation while maintaining fairness in the system. For some combinations of primary and secondary frequency assignments (“macro” and “micro” frequency reuse patterns), we obtained up to 40% gain in capacity.