On the Trade-off between Diversity and Delay in Multi-user System: Static and Dynamic Transmission Policies

• Main Authors: Yu-Hsin Lin, 林禹欣
• Other Authors: 蔡志宏
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/9m5bzx

碩士 === 國立臺灣大學 === 電信工程學研究所 === 107 === Reliability, latency, and the number of connected users form the golden triangle of Internet of Things. In this thesis, the fundamental trade-off among them are investigated in the multi-user system with quasi-static MIMO channel. By a cross-layer system model, the overall latency including transmission time at the physical layer as well as queuing delay at the network layer is considered. We study two different scenarios of this problem. First, we focus on the static transmission policy and delay-bound metric. Our goal is to find the optimal policy that can minimize the delay-bound, given that the system error probability is below a prescribed threshold. By taking the problem to the high SNR asymptotic regime, it can be formulated into a convex optimization problem. Hence Karush-Kuhn-Tucker (KKT) conditions can be used to find the optimal solution. The result shows that the parameters of arrival distribution, the prescribed threshold of the error probability, and the number of users determine the choice of the optimal policy. In addition, the overall latency grows super-linearly with the number of users. Then we turn to the dynamic policy and average delay metric. We solve this problem based on Markov decision process. By convexity and symmetry of the value function, we can find the optimal policy. In addition, two algorithms for finding the optimal policy are proposed.