Throughput and Latency of Millimeter-Wave Networks : Performance Analyses and Design Principles

Sammanfattning: Nowadays, the ever-increasing demands on higher data rates and better serviceperformance have posed extremely huge challenges to the existing wireless communicationswithin sub-6 GHz bands, mainly due to the spectrum scarcity in lowerfrequency bands. In recent years, the millimeter-wave (mm-wave) technology, as apromising candidate to meet the aforementioned demands, have attracted extensiveresearch attention, and has been regarded as one of the key enablers for theforthcoming the 5th generation (5G) mobile communications. The main featuresof mm-wave communications include: abundant spectral resources, high penetrationloss, severe path loss, weak multi-path effects, and narrow antenna beams, andthese particular features make the potential challenges and solutions with mm-wavediffer a lot from those in the conventional 6-GHz systems.It is known that the high throughput and the low latency are two critical qualityof-service (QoS) aspects in future mobile networks, while the related research withmm-wave are fairly recent and insufficient in the past few years. Motived by theurgent needs for further development and the blanks remained in previous works,in this doctoral thesis, we investigate the throughput and the latency in mm-wavenetworks through conducting performance analyses and identifying design principles,with the objective of seeking clues for improving the QoS of mm-wave wirelesscommunications in practice.Our main research regarding throughput and latency in mm-wave networksthat are included in this doctoral thesis can be categorized from the following threeaspects:(i) Throughput of mm-wave relay networks: For indoor scenarios, we study thehalf-duplex (HD) relaying with mm-wave in the presence of random linkblockages, where a distance-based routing algorithm is proposed to maximizethe throughput. For outdoor scenarios, focusing on a two-hop amplifyand-forward (AF) relay network in the HD or the full-duplex (FD) mode, weinvestigate the impacts of beamwidth, ground reflections, and self-interferencecoefficient on the throughput, where Gaussian-type directional antenna modeland two-ray channel model are jointly adopted.(ii) Latency analysis via stochastic network calculus: With the aid of stochasticnetwork calculus, we derive upper bounds for the probabilistic delay tokeep track of the latency performance of buffer-aided mm-wave networks. We mainly study mm-wave systems designed in tandem or parallel manners,and also consider a hybrid design that combines the tandem and parallelschemes in a flexible manner. Moreover, the capability of achieving low-latencymm-wave communications is characterized and investigated in terms of effectivecapacity, and the comparison among different transmission schemes isconducted to identify the respective strengths and proper conditions for theirapplications.(iii) Traffic allocation for low-latency mm-wave systems: Traffic allocation schemesfor low latency in buffer-aided mm-wave networks are investigated. Due tothe use of buffers, the delay optimization problem hereby differs from thosewithout buffers, where the conventional graph-based network optimizationtechniques become intractable. We demonstrate the impacts of different trafficallocation schemes on the latency. For multi-hop networks with multipleparallel channels in each hop, we consider both local and global traffic allocationschemes, quantify their resulting end-to-end (E2E) latencies, and analyzethe respective strengths and weaknesses.