Analysis of TCP Performance in 5G mm-wave Mobile Networks

Abstract

Millimeter-wave (mm-wave) bands are projected to play an essential role in 5G mobile networks in supporting the increasing demands for higher data rates. Communications at mm-wave frequency bands pose unique challenges. The high variability in channel quality due to high propagation loss and unfavorable atmospheric absorption can only be overcome by the use of highly directional antennas. This results in a much higher degree of spatial reuse and lower interference if compared with omni-directional communications at lower frequencies. However, the high directionality may cause communication blockages as the channel may appear and disappear because of beam misalignments. While significant research efforts have investigated challenges and aspects of physical (PHY) and medium access control (MAC) layers, the impact of the unique features of mm-wave systems on transport layer still requires attention. In this article, we focus on analyzing the behavior of congestion control protocols and study their impact on system-level performance. Through extensive simulations, we show the effect of different type of blockages on the design of congestion control protocol in presence of handovers and when small, medium and long flows coexist. Protocols like CUBIC that target high-throughput performance benefit significantly by joint optimization of link layers buffers and timeouts. While the optimization foster prompt reaction to short-term blockages and make them ideal for small and medium flows, their performance significantly decrease when obstacles degrade the channel quality for longer time periods. Hybrid-designs like YeAH are more robust to blockages, but fail to recover fast and achieve the link capacity after timeouts