arXiv subjects

Christopher Slezak

Publications and source records attributed to Christopher Slezak.

5 recordsLinked to original sources

arXiv2020

Beamformed mmWave System Propagation at 60GHz in an Office Environment

Millimeter wave wireless systems rely heavily on directional communication in narrow steerable beams. Tools to measure the spatial and temporal nature of the channel are necessary to evaluate beamforming and related algorithms. This paper presents a novel 60~GHz phased-array based directional channel sounder and data analysis procedure that can accurately extract paths and their transmit and receive directions. The gains along each path can also be measured for analyzing blocking scenarios. The sounder is validated in an indoor office environment.

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arXiv2019

Power Efficient Discontinuous Reception in THz and mmWave Wireless Systems

Discontinuous reception (DRX), where a user equip-ment (UE) temporarily disables its receiver, is a critical power saving feature in modern cellular systems. DRX is likely tobe particularly aggressively used in the mmWave and THzfrequencies due to the high front end power consumption. A keychallenge of DRX in these frequencies is that individual links are directional and highly susceptible to blockage. MmWave and THz UEs will therefore likely need to monitor multiple cells in multiple directions to ensure continuous reliable connectivity.This work proposes a novel, heuristic algorithm to dynamically select the cells to monitor to attempt to optimally trade-off link reliability and power consumption. The paper provides preliminary estimates of connected mode DRX mode consumption using detailed and realistic statistical models of blockers at both 28 and 140 GHz. It is found that although blockage dynamics are faster at 140 GHz, reliable connectivity at low power can be maintained with sufficient macro-diversity and link prediction

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arXiv2018

Empirical Effects of Dynamic Human-Body Blockage in 60 GHz Communications

The millimeter wave (mmWave) bands and other high frequencies above 6~GHz have emerged as a central component of Fifth-Generation (5G) cellular standards to deliver high data rates and ultra-low latency. A key challenge in these bands is blockage from obstacles, including the human body. In addition to the reduced coverage, blockage can result in highly intermittent links where the signal quality varies significantly with motion of obstacles in the environment. The blockages have widespread consequences throughout the protocol stack including beam tracking, link adaptation, cell selection, handover and congestion control. Accurately modeling these blockage dynamics is therefore critical for the development and evaluation of potential mmWave systems. In this work, we present a novel spatial dynamic channel sounding system based on phased array transmitters and receivers operating at 60 GHz. Importantly, the sounder can measure multiple directions rapidly at high speed to provide detailed spatial dynamic measurements of complex scenarios. The system is demonstrated in an indoor home-entertainment type setting with multiple moving blockers. Preliminary results are presented on analyzing this data with a discussion of the open issues towards developing statistical dynamic models.

cs.IT↗

arXiv2018

Understanding End-to-End Effects of Channel Dynamics in Millimeter Wave 5G New Radio

A critical challenge for wireless communications in the millimeter wave (mmWave) bands is blockage. MmWave signals suffer significant penetration losses from many common materials and objects, and small changes in the position of obstacles in the environment can cause large variations in the channel quality. This paper provides a measurement-based study of the effects of human blockage on an end-to-end application over a mmWave cellular link. A phased array system is used to measure the channel in multiple directions almost simultaneously in a realistic indoor scenario. The measurements are integrated into a detailed ns-3 simulation that models both the latest 3GPP New Radio beam search procedure as well as the internet protocol stack. The measurement-based simulation illustrates how recovery from blockage depends on the path diversity and beam search.

cs.IT↗

arXiv2017

60 GHz Blockage Study Using Phased Arrays

The millimeter wave (mmWave) frequencies offer the potential for enormous capacity wireless links. However, designing robust communication systems at these frequencies requires that we understand the channel dynamics over both time and space: mmWave signals are extremely vulnerable to blocking and the channel can thus rapidly appear and disappear with small movement of obstacles and reflectors. In rich scattering environments, different paths may experience different blocking trajectories and understanding these multi-path blocking dynamics is essential for developing and assessing beamforming and beam-tracking algorithms. This paper presents the design and experimental results of a novel measurement system which uses phased arrays to perform mmWave dynamic channel measurements. Specifically, human blockage and its effects across multiple paths are investigated with only several microseconds between successive measurements. From these measurements we develop a modeling technique which uses low-rank tensor factorization to separate the available paths so that their joint statistics can be understood.

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