بهينه سازي تخصيص توان در سيستم هاي مخابراتي همكارانه مجهز به برداشتگر انرژي در حضور رله

چكيده انگليسي :

Optimal Power Allocation for Relay based Cooperative Communication Systems with Energy Harvesting Marzieh Ajirak m ajirak@gmail com January 11 2016 Department of Electrical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree Master of Science MSc Language FarsiSupervisor Mohammad Javad Omidi Assoc Prof omidi@cc iut ac ir AbstractThe rapid growth in wireless devices and the spread of wireless communication systems has increased thedemand for energy sources Therefore reliable energy sources should be provided to guarantee effective per formance of wireless networks Although energy storages and batteries provide a convenient solution they cannot be used as the sole power source in the long run Moreover in some cases battery replacements can bechallenging and expensive or in some areas impossible In recent years energy harvesting EH technologieshas emerged as a promising method to power the nodes of a wireless communication network Energy harvest ing communication are able to harvest ambient energy from their surrounding environment and are thereforeless dependent to non renewable energy sources and can enjoy a prolonged lifetime The rechargeable bat tery in an energy harvesting transmitter or receiver can serve as the primary or a backup power source Theidea of using renewable ambient energy sources rises the possibility of having green communication networks Using energy harvesting devices in communication systems changes the nature of the challenges faced whendesigning optimal performance schemes for such networks The main challenge in the design of energy harvest ing communications systems is that the available energy at any time instance is essentially a random variable In other words the ambient energy becomes available at the nodes in random quantities and at random timesthroughout the communication horizon Hence optimal transmission policies that account for the time varyingavailable energy must be designed so that the network can exploit this random ambient energy arrivals in themost efficient way This thesis investigated the problem of designing optimal transmission policies for energyharvesting cooperative communication systems We considered a decode and forward relay network with anenergy harvesting source and an energy harvesting relay We consider the direct link between source and thedestination as well The throughput maximization problem over a finite horizon of N transmission blocks isinvestigated In the first part of this thesis we examined the problem of total throughput maximization for theenergy harvesting network in the offline setting In this case we assumed that the information of the energy har vesting and channel fading profiles are available prior to the beginning of the transmission The results obtainedin this part serve as the performance upper bound for the energy harvesting communication system under con sideration In the second part of this thesis we considered the more practical online setting where the energyarrival information and the channel states information is known causally For this case dynamic programmingcan be used which is the conventional approach for solving stochastic control problems Dynamic program ming in general has a high computational complexity we used a method based on Markov decision processesto obtain power optimal transmission policies In MDP formulation we have considered discrete state spacefor the system Furthermore the transmission power was chosen from a set of discrete and finite power levels This approach makes the problem tractable to be solved Implementing the MDP formulation needs certaincomputational and memory requirements so there has been some suboptimal solutions The optimal and alsosuboptimal methods are simulated to obtain the power levels The performance of the introduced schemes areevaluated using computer simulations and are compared to existing methods which address the same problem Keywords1 Energy Harvesting 2 Cooperative Commu

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بهينه سازي تخصيص توان در سيستم هاي مخابراتي همكارانه مجهز به برداشتگر انرژي در حضور رله

بهينه سازي محدب , فرآيند تصمصم گيري ماركوف