PhD seminar – 21th, November 2022
Mamoutou Diarra – Inria DIANE team
Title: Enhanced Transport-Layer Mechanisms for MEC-Assisted Cellular Networks.
Abstract: Addressing transport-layer issues in cellular networks is still a hot research topic, despite the fact that a wide range of solutions have been proposed over the last decades. One reason that could explain this phenomenon is the difficulties in the real-world adoption of the proposed solutions as they require either drastic changes in the cellular network protocol stack (in the UE and/or in the base station) or a standardization effort so that TCP headers can include radio information. Another reason is the fact that most of these solutions are effective only in a few scenarios and fail to mitigate the transport-layer issues considered on a global or large scale.
Inspired by these limitations and the growing trend towards Mobile and Multi-Access Edge Computing (MEC), we set out in this thesis to demonstrate that several transport-layer issues in a MEC-enabled 4G/5G network can be mitigated without requiring any modifications in the end-user’s device or in the 4G/5G stack. To this end, we propose novel transport-layer optimization solutions that leverage the MEC Radio Network Information Service (RNIS) and other MEC capabilities to improve some key traditional transport-layer mechanisms such as slow start, steady state behavior, loss detection and flow control mechanisms. We show the efficiency of this approach by first proposing SIGMA, an uplink-oriented Congestion Control Algorithms (CCA) that outperforms BBR and existing CCAs in terms of throughput and delay; then we propose and implement MELD, a loss discrimination algorithm that can improve the throughput of loss-based CCAs by up to 80% in case of wireless/random losses; and lastly we propose RAPID, a RAN-aware Performance Enhancing Proxy (PEP) capable of transparently reducing the increase in delay by a factor of 10 to 50 without lowering the throughput, regardless of the number or the behaviors of the TCP flows sharing the same per-user buffer. Finally, we implement MELD and RAPID in Linux and validate their performance in a real-world 4G network based on OpenAirInterface and FlexRAN.