On relay selection to maximize coverage region for cooperative cellular networks with multiple fixed and unfixed relays

The performance of a relay-based cooperative cellular network is affected by the relay location. Many efforts have been made in the literature for optimal relay placement from various perspectives and with different assumptions. A small group of research work focuses on maximizing coverage region of cooperative relaying networks by finding optimal relay location within network. In this paper, we propose a simple relay selection technique in a cooperative cellular network with the objective of maximizing coverage region of cellular network. We consider the condition in which we have two types of relays in the network, fixed and unfixed relays. The fixed relays are the relay stations which are installed at the optimal location to achieve maximum coverage region, and unfixed relays are network users which can act as relays, too. Our purpose is to select the superior relay node from these fixed and unfixed potential relay nodes. To this end, we consider three criteria in our relay selection scheme. These criteria are relay location, source-to-relay (S2R) channel's gain and relaying strategy. We use two mathematical multiple criteria decision making methods to select the “best” relay node among available ones. The methods are verified by numerical results. Numerical results show that the proposed schemes effectively rank the potential relay nodes based on their superiority.