Cooperative communications with HARQ in a wireless mesh network based on 3GPP LTE

This paper presents some results of the FP7 ICT-LOLA (achieving LOw LAtency in wireless communications) project on the design of a clusterized wireless mesh network based on 3GPP LTE. First, we focus on the new MAC/PHY structure proposed. Then, the concept of virtual link is presented for inter-cluster communications combining MAC layer forwarding, hybrid automatic repeat request (HARQ) and cooperative communications with Decode and Forward (DF). The goal of a virtual link is to enable low latency data transfer in inter-cluster communications. The virtual link solution is studied by simulations thanks to OpenAirInterface which integrates LTE MAC and PHY layer procedures, as well as adaptations needed for the LOLA wireless mesh network. Simulation results show that the proposed distributed solution smoothly adapts to the link conditions. A loss in throughput efficiency is the price to be paid in certain configurations for the distributed operation of the virtual link. Nevertheless, the technique helps in reducing the average number of transmissions thus contributing to improve the latency of the system.