Research On Efficient And Robust Scheduling Mechanism For Millimeter Wave Wireless Backhaul Networks

The millimeter-wave(mmWave)wireless communication with huge bandwidth provides an effective solution to meet the large backhaul traffic demand between base stations(BS)in the small cell densely deployed scenario.The adopted directional antenna and beamforming technology enables the concurrent transmissions between multiple flows.The concurrent transmissions can significantly increase the system throughput,but it may cause higher multi-user interference(MUI)and thus lead to lower transmission rates.Moreover,in the future,millimeter-wave wireless backhaul networks will require multi-gigabit throughputs.In order to ensure the quality of service(QoS),it is necessary to satisfy the QoS requirements of the flows as much as possible.Therefore,when the number of time slot is limited and the number of flows is large,how to efficiently schedule the multiple flows to fully utilize the advantages of concurrent transmission and complete the QoS requirements of the flows as much as possible become an important challenge.Generally,the nodes in the networks are assumed to be half-duplex(HD).In order to meet the QoS requirements of the flows as much as possible,this paper designs a QoS-aware half-duplex concurrent scheduling scheme(QAHD)for the mmWave wireless backhaul networks.The scheme introduces the concept of network global contention graph,aiming at maximizing the number of flows with their QoS requirements satisfied in the network,and considering the MUI between different flows.Simulations show that QAHD can significantly increase the number of flows with their QoS requirements satisfied and the total system throughput compared with other half-duplex solutions.Compared with HD,full-duplex(FD)technology can further increase the spectral efficiency.However,due to the serious self-interference from the transmitting antenna to the receiving antenna at the same node,the FD concurrent scheduling scheme of the flows is more complicated to design.How to introduce the FD technology to the scheduling problem of the mmWave wireless backhaul networks,so that it can further improve the network performance on the basis of effectively solving the self-interference problem,becomes a key issue.For this problem,this paper proposes a QoS-aware full-duplex concurrent scheduling scheme(QAFD)for the mmWave wireless backhaul networks.The scheme considers both the residual self-interference(RSI)and the MUI,and also fully considers the users' QoS requirements.Simulations show that with higher self-interference cancellation level and an appropriate contention threshold,the proposed solution can significantly increase the number of flows with their QoS requirements satisfied and the total system throughput.On the other hand,the mm Wave link is sensitive to the obstacles,and the resulting interruption problem will seriously affect the users'experience.In this case,how to maintain the effective transmission of the blocked flows and the robustness of the network is an important issue.In this regard,this paper proposes a relay-assisted and QoS-aware scheduling scheme(RAQA)for the backhaul networks.It consists of a relay selection algorithm for the blocked flows and a concurrent transmission scheduling algorithm where the backhaul path and the relay path coexist.The relay selection scheme selects non-repetitive relays with high rates,and the concurrent scheduling algorithm pays attention to the difference between the backhaul paths and the relay paths.Simulations show that RAQA can effectively overcome the blockage problem,and at the same time,it can significantly increase the number of flows with their QoS requirements satisfied and the total system throughput compared with other solutions.