TCP over Satellite-to-Unmanned Aerial/Ground Vehicles Laser Links: Hybla or Cubic?

Satellite-based Internet access for the whole globe, a newly emerging market, has recently received much attention from both academia and industry. In this paper, we present an analytical investigation of transmission control protocol (TCP), which is the most popular protocol for various Internet applications, in free-space optical (FSO) communications based low earth orbit (LEO) satellite systems. Specifically, the throughput performance of the potential deployed TCP variants for high-speed and long-distance of FSO-based satellite networks, namely TCP Hybla and TCP Cubic, are analyzed. Additionally, the incremental redundancy hybrid automatic repeat request (IR-HARQ) protocol is employed to enhance the system performance over satellite-to-vehicles FSO links. The numerical results quantitatively demonstrate the impact of atmospheric turbulence on the TCP throughput and show that TCP Cubic outperforms Hybla in the low error-rate conditions while Hybla provides the better performance when the transmission errors happen more frequently. Monte Carlo simulations are also performed to validate the accuracy of theoretical derivations.