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To achieve reliable small cell millimeter-wave wireless backhauls, this study installs small cell base stations (SBSs) on overhead messenger wires to gain flexibility in physical deployments of SBSs ensuring in the line-of-sight connections between SBSs and gateway BSs. These installations pose challenges in aligning directional beams, whereby complicated wind-forced dynamics in on-wire SBSs require frequent beam training, and consequently, a large signaling overhead. To address this, this study aims at demonstrating the feasibility of learning-based beam tracking where a beam tracking policy is learned a priori to fix beam misalignment caused by the wind-forced dynamics. Because wind-forced dynamics in SBSs can be three-dimensional (3D), the proposed beam tracking newly exploits the 3D position/velocity of the SBS as state information. As a solution to fix beam misalignment, the beam tracking policy is learned via deep reinforcement learning wherein the 3D information and beam direction are regarded as a state and an action, respectively, and the received signal power at a gateway BS is maximized. The simulation results depict the feasibility of learning an appropriate beam tracking policy to prevent beam misalignment induced by wind-forced 3D dynamics in on-wire SBSs.

Network coding is a promising technique for improving system performance in wireless multihop networks. In this paper, the throughput and fairness in single-relay multi-user wireless networks are evaluated. The carrier sense multiple access with collision avoidance (CSMA/CA) protocol and network coding are used in the medium access control (MAC) sublayer in such networks. The fairness of wireless medium access among stations (STAs), the access point (AP), and the relay station (RS) results in asymmetric bidirectional flows via the RS; as a result the wireless throughput decreases substantially. To overcome this problem, an autonomous optimization of minimum contention window size is developed for CSMA/CA and network coding to assign appropriate transmission opportunities to both the AP and RS. By optimizing the minimum contention window size according to the number of STAs, the wireless throughput in single-relay multi-user networks can be improved and the fairness between bidirectional flows via the RS can be achieved. Numerical analysis and computer simulations enable us to evaluate the performances of CSMA/CA and network coding in single-relay multi-user wireless networks.

Network coding is a promising technique for improving system performance in wireless multihop networks. In this paper, the throughput and fairness in single-relay multiuser wireless networks are evaluated. The carrier sense multiple access with collision avoidance (CSMA/CA) protocol and network coding are used in the medium access control (MAC) sublayer in such networks. The fairness of wireless medium access among stations (STAs), the access point (AP), and the relay station (RS) results in asymmetric bidirectional flows via the RS; as a result the wireless throughput decreases substantially. To overcome this problem, an autonomous optimization of minimum contention window size is developed for CSMA/CA and network coding to assign appropriate transmission opportunities to both the AP and RS. By optimizing the minimum contention window size according to the number of STAs, the wireless throughput in single-relay multi-user networks can be improved and the fairness between bidirectional flows via the RS can be achieved. Numerical analysis and computer simulations enable us to evaluate the performances of CSMA/CA and network coding in single-relay multi-user wireless networks.