Secure Data Transmission in Cooperative Modes: Relay and MAC
  Cooperation in clouds provides a promising technique for 5G wireless networks, supporting higher data rates. Security of data transmission over wireless clouds could put constraints on devices; whether to cooperate or not. Therefore, our aim is to provide analytical framework for the security on the physical layer of such setup and to define the constraints embodied with cooperation in small size wireless clouds. In this paper, two legitimate transmitters Alice and John cooperate to increase the reliable transmission rate received by their common legitimate receiver Bob, where one eavesdropper, Eve exists. We provide the achievable secure data transmission rates with cooperative relaying and when no cooperation exists creating a Multiple Access Channel (MAC). The paper considers the analysis of different cooperative scenarios: a cooperative scenario with two relaying devices, a cooperative scenario without relaying, a non-cooperative scenario, and cooperation from one side. We derive analytical expressions for the optimal power allocation that maximizes the achievable secrecy rates for the different set of scenarios where the implication of cooperation on the achievable secrecy rates was analyzed. We propose a distributed algorithm that allows the devices to select whether to cooperate or not and to choose their optimal power allocation based on the cooperation framework selected. Moreover, we defined distance constraints to enforce the benefits of cooperation between devices in a wireless cloud. 
Samah A. M. Ghanem and Munnujahan Ara
cs.IT math.IT