OPTIMAL DISTRIBUTED SCHEDULING ALGORITHM FOR COOPERATIVE COMMUNICATION NETWORKS
Mehdi Salehi Heydar Abad
Electronics Engineering, MSc. Thesis, 2015
Assoc. Prof. Dr. Özgür Erçetin (Thesis Advisor), Prof. Dr. Eylem Ekici (Thesis Co Advisor), Assoc. Prof Dr. Özgür Gürbüz, Assoc. Prof Dr. Müjdat Çetin
Assoc. Prof Dr. Kerem Bülbül
Date & Time: January 5th, 2015 – 3:30 PM
Keywords: Wireless Scheduling, Resource Allocation, Cooperative communication, Throughput Optimal
There has been an enormous interest towards cooperative communication in recent years. Cooperative communication plays a significant role in providing a reliable communication in wireless networks. Cooperative communication helps overcome fading and attenuation in wireless networks. Its main purpose is to increase the communication rates across the network and to increase reliability of time varying links. It is known that wireless communication from a source to a destination can benefit from the cooperation of nodes that overhear the transmission.
In this thesis we consider problem of resource allocation in cooperative network consisting of Primary User (PU) and (N-1) Secondary Users (SUs), operating in a shared wireless medium. In our network scenario, PU's dedicated channel suffers from fading. PU, in order to overcome fading and attenuation, grants access of its dedicated channel to other SUs conditioned on their cooperation. Whenever PU's dedicated channel is OFF, its packet can be relayed through SU's. Our ultimate goal is to design a distributed algorithm to achieve optimal throughput properties.
Maximum Weight Scheduling can achieve throughput optimality by exploiting opportunistic gain in general network topology with fading channels. Despite the advantage of opportunistic scheduling, this mechanism requires that the existing central scheduler is aware of network conditions such as channel state and queue length information of users. We break this assumption by considering that only individual information is available at each user. We design a Carrier Sense Multiple Access (CSMA) based algorithm which only uses individual queue length information. We derive exact capacity region of the cooperative network for two user scenario thus establishing superiority of the cooperative network over non cooperative network. Then we prove throughput optimality of our proposed algorithm for two scenarios; first being a cooperative network consisting of N user with only PU having fading channel and second a two user scenario where all existing links suffer from fading.