Minimizing Weighted Sum Age of Information with Open-Loop Cyclic Scheduling

We study the scheduling problem in a status update system composed of an arbitrary number of information sources with different service time distributions and weights for the purpose of minimizing the weighted sum age of information (AoI). In particular, we study open-loop schedulers which rely only on the statistics (specifically, only on the first two moments) of the source service times, in contrast to closed-loop schedulers that also make use of the actual realizations of the service times and the AoI processes in making scheduling decisions. Open-loop scheduling policies can be constructed off-line and are simpler to implement compared to their closed-loop counterparts. We consider the generate-at-will (GAW) model, and develop an analytical method to calculate the exact AoI for the probabilistic and cyclic open-loop schedulers. In both cases, the server initiates the sampling of a source and the ensuing transmission of the update packet from the source to the server in an open-loop manner; either based on a certain probability (probabilistic scheme) or according to a deterministic cyclic pattern (cyclic scheme). We derive the optimum open-loop cyclic scheduling policy in closed form for the specific case of N=2 sources and propose well-performing heuristic cyclic schedulers for general number of sources, i.e., N>2. We study the proposed cyclic schedulers against probabilistic schedulers and several existing methods in the literature to validate their effectiveness.Comment: 10 pages, 5 figure

Kablosuz ağlarda enerji-gecikme ödünleşiminin kuyruk sistemi analizi

Cataloged from PDF version of article.Thesis (M.S.): Bilkent University, Department of Electrical and Electronics Engineering, İhsan Doğramacı Bilkent University, 2018.Includes bibliographical references (leaves 46-50).Energy-efficiency of wireless communication systems has been an important research topic in recent years. For such a system, a transmission profile is described by the transmission power and the modulation and coding scheme (MCS) to be used for packet transmission. For a given channel condition, higher order MCSs offer higher throughput at the expense of requiring more transmission power. Average power consumption of the system can be reduced by using lower order MCSs at the expense of increased queuing delays. Using this observation, the goal of this study is the development of transmission profile selection policies so as to minimize the average power consumption while meeting a statistical delay constraint for a wireless link. For the purpose of assessing the proposed policies, the system is modeled as an M/M/1 queue where transmission speeds of packets are dynamically selected based on the queuing delay already experienced by them. This setting is shown to give rise to a multi-regime Markov uid queue model which is used to obtain the waiting time distributions of packets as well as the average power consumption. In the numerical examples, proposed pro- file selection policies are evaluated for different system parameters using realistic transmission profiles obtained from LTE simulations. A proposed energy-aware profile selection policy is shown to consistently outperform all other proposed policies in terms of energy-efficiency whereas a reasonable performance is also obtained with a simpler-to-implement policy.by Ege Orkun Gamgam.M.S