Cognitive Radio Networking with Cooperative Relaying and Energy Harvesting

Cognitive radio networks with energy harvesting result in efficient use of both energy and spectrum. By using cooperative relaying, another feature can be achieved, which is the high diversity gain. In this paper, an energy harvesting underlay cognitive radio relaying network is investigated. In this underlay cognitive radio scheme, secondary users are allowed to access the spectrum, respecting a certain primary interference threshold. The secondary nodes employ decode-and-forward relaying in order to maximize the total received data by optimizing their transmit powers. In this context, both the secondary source and relay harvest energy from renewable sources and store it in finite batteries. They are also capable of buffering data in infinite capacity buffers. We derive closed form expressions for transmit power of secondary source and relay that maximize the secondary network throughput. Projected subgradient method is used to find the power allocated to the secondary network. Numerical simulations are conducted to study the performance of the proposed system. Comparisons are made between the proposed system and other conventional scenarios, and it is observed that when the required signal-to interference-plus-noise ratio (SINR) at the primary receiver is high, the proposed harvesting- based scheme and conventional-based scheme perform similarly.