FBDT: Sum-Throughput Achieving Transport Layer Solution for Multi-RAT Networks

Emerging mobile applications give rise to new bandwidth-hungry and latency-sensitive traffic classes that challenge existing wireless systems. Addressing them requires innovative approaches such as simultaneous data transmission across multiple Radio Access Technologies (RATs), e.g., WiFi and WiGig. However, existing transport layer multi-RAT traffic aggregation schemes, e.g., multi-path TCP, suffer from Head-of-Line (HoL) blocking and sub-optimal traffic splitting across the RATs that severely penalize their performance. In this paper, we investigate the design of FBDT, a novel multi-path transport layer solution that for the first time can achieve the sum of the throughput rates across the individual RATs network paths, despite their channel conditions' dynamics. We have implemented FBDT in the Linux kernel and show substantial improvement in throughput relative to state-of-the-art schemes, e.g, 2.5x gain in a dual-RAT scenario (WiFi and WiGig) when the client is mobile. Second, we extend FBDT to more than two radios and demonstrate that its throughput performance scales linearly with the number of RATs, in contrast to multi-path TCP, whose performance degrades with an increase in the number of RATs. We evaluate the performance of FBDT on different traffic classes and demonstrate: (i) 2-3 times shorter file download times, (ii) up to 10 times shorter streaming times and 10 dB higher video quality for progressive download video applications, and (iii) up to 9 dB higher viewport quality for interactive mobile VR applications, when our viewport quality maximization framework is employed along with FBDT.