On the move with TCP in current and future mobile networks

Mobile wireless networks constitute an indispensable part of the global Internet, and with TCP being the dominating transport protocol on the Internet, it is vital that TCP works equally well over these networks as over wired ones. This paper evaluates the performance of TCP NewReno and TCP CUBIC with respect to responsiveness to bandwidth variations related to different user movements. The evaluation complements previous studies on 4G mobile networks in two important ways: It primarily focuses on the behavior of the TCP congestion control in medium-to high-velocity mobility scenarios, and it not only considers the current 4G mobile networks, but also low latency configurations that move toward the potential delays in 5G networks. The results show that while the two TCP versions give similar goodput in scenarios where the radio channel quality continuously decreases, CUBIC gives a significantly higher goodput in scenarios where the quality continuously increases. This is due to CUBIC probing more efficiently for additional bandwidth. The results also show that these differences becomes much smaller for the low latencies of 5G networks, and it is seen that significant differences in such settings only occur when a continuously deteriorating radio channel is combined with large fluctuations of available bandwidth.