Cooperative Communications in Satellite Networks: Techniques and Challenges

Cooperative communications in satellite networks have been paid much attention recently, which can potentially enhance the network's performance. In this technique, several satellite nodes work together to transmit and receive the signal cooperatively, leading to increased spectral efficiency, improved reliability, and coverage. This paper reviews current research efforts in satellite networks concerning cooperative communications, including techniques employed and state-of-the-art challenges. Space-time coding is one of the principal tools of cooperative communications, where information is spread over multiple paths by multiplexing the signals from individual satellites. This counteracts the adverse effects of several impairments on satellite links, including fading, interference, and path loss. Distributed beamforming to improve received signal strength and (some) interference reduction, using arrays of antennas in multiple satellites. Besides, some challenges are faced by single satellite networks for interpreting cooperative communications. These are satellite synchronization, channel estimation, power allocation, and dealing with interferences. In addition, integrating cooperative communications with current satellite network architecture and protocols poses extra challenges. Cooperative communications bring various advantages to satellite networks but also introduce several technical challenges. Additional studies are required to tackle such issues and enhance the operational capabilities of cooperative satellite systems.