X-TCP: A Cross Layer Approach for TCP Uplink Flows in mmWave Networks

TL;DR

This paper proposes a cross-layer TCP congestion control method for mmWave networks that improves uplink performance by estimating physical layer data rates, reducing latency and recovery time.

Contribution

It introduces a novel cross-layer approach that adjusts TCP congestion window based on physical layer estimations for mmWave uplink flows.

Findings

Reduces latency by avoiding buffer overflows.

Achieves quicker recovery after RTO events.

Outperforms existing TCP algorithms in mmWave scenarios.

Abstract

Millimeter wave frequencies will likely be part of the fifth generation of mobile networks and of the 3GPP New Radio (NR) standard. MmWave communication indeed provides a very large bandwidth, thus an increased cell throughput, but how to exploit these resources at the higher layers is still an open research question. A very relevant issue is the high variability of the channel, caused by the blockage from obstacles and the human body. This affects the design of congestion control mechanisms at the transport layer, and state-of-the-art TCP schemes such as TCP CUBIC present suboptimal performance. In this paper, we present a cross layer approach for uplink flows that adjusts the congestion window of TCP at the mobile equipment side using an estimation of the available data rate at the mmWave physical layer, based on the actual resource allocation and on the Signal to Interference plus Noise Ratio. We show that this approach reduces the latency, avoiding to fill the buffers in the cellular stack, and has a quicker recovery time after RTO events than several other TCP congestion control algorithms.