Multi-satellite relay transmission in 5G: Concepts, techniques, and challenges

The demands of 5G mobile communications, such as higher throughput and lower latency in future communications, has promoted more advanced communication technologies and heterogeneous network integration. Satellite communication has been recently considered as a key part of 5G for the benefits of meeting the availability and ubiquitous coverage requirements targeted by 5G. As a potential 5G technology, multi-satellite cooperative transmission systems have been studied, as they can provide the high throughput brought by virtual multiple-input multiple-output structures. In this article, we briefly review the concepts and techniques of multi-satellite cooperative transmission systems in 5G. Moreover, the architectures of two multi-satellite relay transmission systems based on TDMA and NOMA are introduced. In particular, we focus more on the performance evaluation and research challenges of the TDMAbased architecture to explore its system optimizing approach. Finally, to exploit the full potential of multi-satellite systems in 5G networks, future trends and challenges are discussed.