چكيده به لاتين
Energy suply for low-cost wireless communication nodes is one of the challenges of wireless communication networks. Powering or charging the batteries of these nodes, are infeasible or uneconomic in many places (like wireless sensor networks) using power networks. On the other hand, the use of batteries for wireless sensor networks, internet of things or hazardous environments, has some problems. A solution for powering such nodes, is the use of a cognitive base station (or access point). The base station, with the radio frequency waves, can transmit the energy needed to low-cost sensor nodes and prevent them from recharging the battery, directly. On the other hand, there is no direct connection between the transmitter and receiver in some of the primary (licensed) communications networks, such as wireless sensors embedded in the human body, due to the fading, shaddowing or a large distance from the given receiver. In this case, these nodes embedded in the human body (or nodes in other networks without energy) can use secondary nodes as relays and, as a reward, put their spectrum on those secondary nodes for a short time.
Our goal in this thesis is to maximize the sum throughput of secondary nodes that are used as relay in the connection of the primary transmitter and receiver to meet the primary user rate. In this connection, secondary nodes act as a virtual multi-input multi-output relay system for primary nodes. In this system, the base station (or access point) uses multiple antennas to send energy to secondary nodes and receive data from them, which is the innovation in the proposed model.
To achieve the goal of this thesis, allocation of power resources, sending time, and also the beamforming and relay selection must be performed. The formulation of this optimization problem and its solution is provided to a thesis innovation. Simulation results show that the sum throughput of secondary nodes (provided the minimum rate of 1.5 nats /s /Hz for primary transmitter) is increased from 0.9 nats /s /Hz, in the single-antenna base station mode to 4.2 nats /s /Hz, in multiple antennas base station mode.
Key words: Resource Allocation, Cognitive Radio, Relay System, Energy Harvesting.
