Relay Routing and Scheduling for Capacity Improvement in Cellular WLANs

In classical infrastructure-based wireless systems, all mobile terminals communicate directly with the access point. In such systems, the transmission capacity, i.e., the amount of traffic successfully communicated to/from the access point, is important. This paper studies the possibility to increase this capacity by using mobile terminals as intermediate relays. These relays reduce the communication distance and hence mobile terminals can send their traffic at a maximum data rate while maintaining a target packet error rate and transmission power limit. We present algorithms that solve the relaying problem combining routing, scheduling and adaptive modulation. A crucial aspect is the fair sharing of resources in both direct and relaying systems; two different modes of fairness are identified. For one fairness mode, relaying can improve capacity by up to 30%. In addition, relaying allows to add additional resources, namely frequencies, to a cell, resulting in almost a doubling of capacity.