Boosting TCP & QUIC Performance in mmWave, Terahertz, and Lightwave Wireless Networks: A Survey

Emerging wireless systems target to provide multi-Gbps data rates for each user, which can be achieved by utilizing ultra-wide channels available at mmWave, terahertz, and lightwave frequencies. In contrast to the traditional spectrum below 6 GHz, these high-frequency bands raise many issues, complicating their usage. For example, because of high signal attenuation and blockage by obstacles, the data rates in a high-frequency band may quickly vary by several orders of magnitude. This peculiarity is often considered a challenge for modern transport layer protocols, such as Transmission Control Protocol (TCP) or Quick UDP Internet Connections (QUIC). Their key component is the Congestion Control Algorithm (CCA), which tries to determine a data sending rate that maximizes throughput and avoids network congestion. Many recent studies show that the performance of the existing CCAs significantly degrades if mobile devices communicate with high-frequency bands and propose some solutions to address this problem. The goal of this survey is twofold. First, we classify the reasons for poor TCP & QUIC performance in high-frequency bands. Second, we comprehensively review the solutions already designed to solve these problems. In contrast to existing studies and reviews that mainly focus on the comparison of various CCAs, we consider solutions working at different layers of the protocol stack, i.e., from the transport layer down to the physical layer, as well as cross-layer solutions. Based on the analysis, we conclude the survey with recommendations on which solutions provide the highest gains in high-frequency bands.