tailieunhanh - Báo cáo hóa học: " An Optimal Medium Access Control with Partial Observations for Sensor Networks"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: An Optimal Medium Access Control with Partial Observations for Sensor Networks | EURASIP Journal on Wireless Communications and Networking 2005 4 505-522 2005 R. Cristescu and S. D. Servetto An Optimal Medium Access Control with Partial Observations for Sensor Networks Razvan Cristescu Center for the Mathematics of Information California Institute of Technology Caltech 13693 Pasadena CA91125 USA Email razvanc@ Sergio D. Servetto School of Electrical and Computer Engineering College of Engineering Cornell University 224 Philips Hall Ithaca NY 14853 USA Email servetto@ Received 10 December 2004 Revised 13 April 2005 We consider medium access control MAC in multihop sensor networks where only partial information about the shared medium is available to the transmitter. We model our setting as a queuing problem in which the service rate of a queue is a function of a partially observed Markov chain representing the available bandwidth and in which the arrivals are controlled based on the partial observations so as to keep the system in a desirable mildly unstable regime. The optimal controller for this problem satisfies a separation property we first compute a probability measure on the state space of the chain namely the information state then use this measure as the new state on which the control decisions are based. We give a formal description of the system considered and of its dynamics we formalize and solve an optimal control problem and we show numerical simulations to illustrate with concrete examples properties of the optimal control law. We show how the ergodic behavior of our queuing model is characterized by an invariant measure over all possible information states and we construct that measure. Our results can be specifically applied for designing efficient and stable algorithms for medium access control in multiple-accessed systems in particular for sensor networks. Keywords and phrases MAC feedback control controlled Markov chains Markov decision processes dynamic programming stochastic stability. 1. .