Exploiting multiple paths and diversity in wireless networks for high goodput and low latency

Abstract

Wireless networks suffer from high packet loss-rates and variations in delay and bandwidth. This makes it difficult for conventional transport protocols like TCP to operate efficiently over such networks. We presented Multi-Path LOss Tolerant transport protocol (MPLOT) in [1] to counter such lossy and volatile conditions. MPLOT uses multiple paths for data transfer such that at an aggregate level, the volatilities of individual paths are averaged out to yield a smooth stable transmission. MPLOT also employs Forward Error Correction (FEC), which adapts to the changing conditions in the network, to control the amount of re-transmissions. We showed in [1] that MPLOT is able to achieve significantly higher goodput (data rate) than traditional TCP-SACK even with packet losses as high as 50%. The goodput attained by MPLOT actually increases with the number of paths (while the total bandwidth across paths remains fixed). However, a protocol that yields high goodput and a high delay cannot be used by several applications that not only demand a high goodput, but a low packet delay as well(e.g. Skype). In this paper, we aim to show that MPLOT can be used for applications that need low delay. We show that MPLOT is able to use multiple paths effectively to yield a low average packet delay with small variation in the lossy and volatile conditions. We also study how MPLOT behaves with conventional TCP flows in lossless conditions. We then study the conditions under which MPLOT is able to reduce transfer time of small sized files (lOKb-100Kb), which is important for interactive web applications.