Jong Yeol Ryu | Searcharxiv

arXiv2021

Non-Terrestrial Networks for UAVs: Base Station Service Provisioning Schemes with Antenna Tilt

By focusing on unmanned aerial vehicle (UAV) communications in non-terrestrial networks (NTNs), this paper provides a guideline on the appropriate base station (BS) service provisioning scheme with considering the antenna tilt angle of BS. Specifically, two service provisioning schemes are considered including the inclusive-service BS (IS-BS) scheme, which makes BSs serve both ground users (GUs) and aerial users (AUs) (i.e., UAVs) simultaneously, and the exclusive-service BS (ES-BS) scheme, which has BSs for GUs and BSs for AUs. By considering the antenna tilt angle-based channel gain, we derive the network outage probability for both IS-BS and ES-BS schemes, and show the existence of the optimal tilt angle that minimizes the network outage probability after analyzing the conflict impact of the antenna tilt angle. We also analyze the impact of various network parameters, including the ratio of GUs to total users and densities of total and interfering BSs, on the network outage probability. Finally, we analytically and numerically show in which environments each service provisioning scheme can be superior to the other one.

eess.SP↗

arXiv2017

Exploiting Trust Degree for Multiple-Antenna User Cooperation

For a user cooperation system with multiple antennas, we consider a trust degree based cooperation techniques to explore the influence of the trustworthiness between users on the communication systems. For the system with two communication pairs, when one communication pair achieves its quality of service (QoS) requirement, they can help the transmission of the other communication pair according to the trust degree, which quantifies the trustworthiness between users in the cooperation. For given trust degree, we investigate the user cooperation strategies, which include the power allocation and precoder design for various antenna configurations. For SISO and MISO cases, we provide the optimal power allocation and beamformer design that maximize the expected achievable rates while guaranteeing the QoS requirement. For a SIMO case, we resort to semidefinite relaxation (SDR) technique and block coordinate update (BCU) method to solve the corresponding problem, and guarantee the rank-one solutions at each step. For a MIMO case, as MIMO is the generalization of MISO and SIMO, the similarities among their problem structures inspire us to combine the methods from MISO and SIMO together to efficiently tackle MIMO case. Simulation results show that the trust degree information has a great effect on the performance of the user cooperation in terms of the expected achievable rate, and the proposed user cooperation strategies achieve high achievable rates for given trust degree.

cs.IT↗