Downlink throughput evaluation in relay-enhanced variable data rate enabled cells

Cellular system deployment can utilize relays both for the capacity improvement and for the coverage extension. This paper studies the performance of the relay enhanced circular cells via the metrics of throughput mean and variance, number of the relay stations, and outage probability. Single-hop links are used as a reference case. Link throughput varies according to four modulation levels whose coverage areas are calculated according to two different path loss models. A new relay position algorithm is proposed to jointly maximize the non-overlapping coverage of relays and minimize the number of them. The provided numerical examples show that the proposed relay placement scheme outperforms random deployments especially at low relay densities. In general, high relay station densities are required for two-hop communications to approach the average throughput of a single-hop scenario. However, the opportunistic two-hop deployments are beneficial also from the interference management and total network load balancing point of view.