First Advisor

Ehsan Aryafar

Term of Graduation

Winter 2024

Date of Publication


Document Type


Degree Name

Doctor of Philosophy (Ph.D.) in Computer Science


Computer Science




fairness, FBDT, mmWave, MPTCP, near far problem, wireless network



Physical Description

1 online resource (xv, 99 pages)


MmWave Radio Access Technology (RAT) is a promising technology for wireless communication due its large bandwidth and is already being deployed in 5G cellular and emerging WiFi technologies. MmWave systems use highly directional beams with narrow beamwidths to overcome the high path loss associated with their frequency bands. A mmWave radio can be used either in a standalone mode (where all radios use the same technology) or simultaneously with other technologies such as LTE and low frequency WiFi in a communication mode commonly referred to as integrated mode. This thesis proposes two methods to optimize mmWave RAT performance in both standalone and integrated modes. First, we address the problem of mmWave link establishment in the standalone mode, which is part of the initial access of the MAC layer. We show that when multiple clients try to establish a link, there exists a severe power imbalance among competing clients' beams, as clients naturally have different orientations and are at different distances from the same access point. This beam power imbalance coupled with poor contention protocols results in poor fairness in dynamic systems with multiple clients. We then introduce a joint power control and contention adaptation mechanism to enhance fairness. Second, we focus on integrated mode and show that existing transport layer solutions such as MPTCP that utilize multiple links simultaneously can have very poor performance when a mmWave RAT is deployed due to susceptibility of mmWave links to mobility and blockages such as human, objects (vehicles, walls, vehicles, animals etc.,). We then propose the design of Forward and Backward Data Transmission (FBDT) protocol, a novel multi-path transport layer solution that can get the summation of individual rates across RATs despite system dynamics. We have implemented FBDT in the Linux kernel and show substantial improvement in throughput against state-of-the-art schemes, e.g, 2.5x gain in a dual-RAT scenario (WiFi and WiGig) when the client is mobile. Further, we extend FBDT to more than two radios and demonstrate that its throughput performance scales linearly with the number of RATs, in contrast to multi-path TCP, whose performance degrades with an increase in the number of RATs. We evaluate the performance of FBDT on different traffic classes and demonstrate (i) 2-3 times shorter file download times, (ii) up to 10 times shorter streaming times and 10 dB higher video quality for progressive download video applications, and (iii) up to 9 dB higher viewport quality for interactive mobile VR applications, when our viewport maximization framework is employed along with FBDT.


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