ieee comsoc technical sub-committee on backhaul...

IEEE ComSoc Technical sub-Committee onBackhaul/fronthaul Networking

and Communications (TCBNC) Blog

Issue 1, December 2017

IEEE ComSoc Technical sub-Committee on Backhaul/fronthaul Networking and Communications Blog 1

Contents

1 Chair’s Message 2

2 Introduction to the feature topic 4

3 Interview with Dr. Amitava Ghosh 6

4 Interview with Prof. David J. Love 10



Chair’s Message

Muhammad Zeeshan Shakir

University of the West of Scotland, Scotland, Email: [email protected]

Dear TCBNC Members:

Millimeter wave (mmWave) technology and its ap-plication to the wireless backhaul for future networkis considered as one of the most sought-after researchtopics today. I am very delighted to introduce you aninaugural issue of TCBNC Blog with special cov-erage on “MmWave Backhaul Networks: Opportu-nities and Challenges”. This special issue includesvirtual interviews with Dr. Amitava Ghosh fromNokia, Bell Labs and Prof. David J. Love form Pur-due University. On behalf of the TCBNC executivecommittee members and our community members,I would like to extend our sincere appreciation toDr. Amitava Ghosh and Prof. David J. Love for thisopportunity to interpret their vision about feasibilityof mmWave technology for enabling future wirelessbackhaul network.

I am very much sure that you will be excited toread through the interesting discussions on oppor-tunities and challenges related to mmWave-enabledwireless backhaul networks and find the virtual in-terviews valuable to understand the rapidly changingresearch and development landscape in this domain;to learn future application use cases and associatedchallenges; and finally, to get leads on some recentwork and open problems.

I would like to express my special thanks to Dr.Omid Semiari form Georgia Southern University andDr. Syed Ali Raza Zaidi from University of Leeds,UK for serving as editors to this special issue andputting every effort to turn it into reality.

I would like to take this opportunity to welcomeany suggestions from the community members tomake TCBNC Blog more informative and inter-esting. You are welcome to either write to me [email protected] or approach any ofthe editors.

Best regards,Muhammad Zeeshan ShakirChair IEEE ComSoc TCBNC

Muhammad Zeeshan Shakir isan Assistant Professor at the Uni-versity of the West of Scotland(UWS), UK. Before joining UWSin Fall 2016, he has been workingat Carleton University, Canada,Texas A&M University, Qatarand KAUST, Saudi Arabia on var-

ious national and international collaborative projects.Most of his research has been supported by industrypartners such as Huawei, TELUS and sponsored by



local funding agencies such as Natural Sciences andEngineering Research Council of Canada (NSERC),Qatar National Research Fund (QNRF) and KAUSTGlobal Research Fund (GCR). His research inter-ests include design, development and deploymentof diverse wireless communication systems, in-cluding hyper-dense heterogeneous small cell net-works, Green networks and 5G technologies such asD2D communications, Networked-flying platforms(NFPs) and IoT. He has published more than 75 tech-nical journal and conference papers and has con-tributed to 7 books, all in reputable venues. He isan editor of 2 research monographs and an author ofa book entitled Green Heterogeneous Wireless Net-works published jointly by Wiley and IEEE Press.He has been/is serving as a Chair/Co-Chair/Memberof several workshops/special sessions and techni-cal program committee of different IEEE flagshipconferences, including Globecom, ICC, VTC andWCNC. He is an Associate Technical Editor ofIEEE Communications Magazine and has served as alead Guest Editor/Guest Editor for IEEE Communi-cations Magazine, IEEE Wireless Communicationsand IEEE Access. He is serving as a Chair of IEEEComSoc emerging technical committee on back-haul/fronthaul networking and communications. Heis a Senior Member of IEEE, an active member ofIEEE ComSoc and IEEE Standard Association.



Feature Topic: Millimeter Wave BackhaulNetworks: Opportunities and Challenges

Editors: Omid Semiari1 and Syed Ali Raza Zaidi2

1Georgia Southern University, GA, USA, Email: [email protected]

2University of Leeds, UK, Email: [email protected]

The proliferation of emerging wireless services –including virtual reality (VR), intelligent transporta-tion systems (ITS), among others – with stringentquality-of-service (QoS) requirements have strainedthe capacity of wireless networks. To address thischallenge, many innovative ideas have been pro-posed in past decades, such as the dense deploy-ment of small cells, multi-antenna communications,leveraging new frequency bands; to significantly in-crease the capacity and coverage at wireless accessnetworks.

Despite the substantial effort to address the traf-fic management challenges at the wireless access,none of the new wireless services turn into realitywithout providing a fast, reliable, and cost-effectivebackhaul/fronthaul connectivity. In particular, formany applications with stringent latency and de-lay requirements (such as ITS), optimizing the end-to-end (E2E) performance – across wireless accessand backhaul – is essential to meet the target QoSrequirements (e.g., sub-milliseconds E2E latency).Such an E2E design mandates new backhaul solu-tions that: first provide large capacity to managethe substantial traffic requested by the end users;

and second, support backhaul connectivity to largenumber of small cell base stations – as foreseen inthe fifth generation (5G) wireless networks – whilemaintaining low capital expenditures (CAPEX) andoperating expenditures (OPEX).

In this regard, operating at high-frequency bands(above 6 GHz), particularly at millimeter wave(mmWave) frequencies (30-300 GHz) is viewed byboth academia and industry as an enabling solu-tion to address the aforementioned challenges of 5Gbackhaul network. In fact, mmWave backhaul tech-nology offers promising features, including: 1) Highdata rates and small over-the-air latency by exploit-ing the large available bandwidth at mmWave fre-quencies; 2) Relatively less implementation chal-lenges compared with mmWave utilization at the ac-cess networks, due to the fixed location of base sta-tions; 3) Higher capability for spectrum reuse, com-pared with sub-6 GHz microwave backhaul, due tohighly directional backhaul links; 4) Small form-factor for transceivers that makes mmWave technol-ogy suitable for dense deployments at the street-levelurban furniture such as lamp posts.

Nonetheless, mmWave backhaul faces several



key challenges, such as short-range mmWave links(which can dictate mesh backhaul architecture withmulti-hop backhaul connections), reliability (due tosusceptibility to rain attenuation, blockage, amongother factors), more complexity and overhead at thecontrol plane for establishing directional links, dy-namic resource management in self-backhauling ar-chitectures, and new deployment regulations (e.g.,to control radiation impact on human body), amongother challenges.

In this special issue, we focus on mmWavebackhaul technology as the feature topic where weconduct interviews with two key researchers in thisfield. In particular, we discuss the opportunities,challenges, main solutions, and open problemspertaining the mmWave backhaul in 5G networks.We hope that this effort be useful for our readers,especially to those who are new in this field ofresearch.

Omid Semiari is an AssistantProfessor at the Electrical Engi-neering Department at GeorgiaSouthern University. He receivedthe BSc and MSc degrees inelectrical engineering from theUniversity of Tehran, in 2010and 2012, respectively, andthe PhD degree from Virginia

Tech, in 2017. His research interests include wire-less networks, millimeter wave communications,context-aware resource allocation, matching theory,and machine learning. In 2014, Dr. Semiari hasworked as an intern at Bell Labs, in Stuttgart, onanticipatory, context-aware resource management incellular networks. In 2016, he has joined QualcommCDMA Technologies for a summer internship,working on LTE-Advanced modem design. Dr.Semiari is the recipient of several research fellow-ship awards, including DAAD (German Academic

Exchange Service) scholarship and NSF studenttravel grant. He has actively served as a reviewerfor flagship IEEE Transactions and conferencesand participated as the technical program com-mittee (TPC) member for a variety of workshopsat IEEE conferences, such as ICC and GLOBECOM.

Syed Ali Raza Zaidi is currentlya University Academic Fellow(Assistant Professor) at the Uni-versity of Leeds. He receivedhis B.Eng degree in informationand communication system engi-neering from the School of Elec-tronics and Electrical Engineer-

ing, NUST, Pakistan in 2008. He was awarded theNUSTs most prestigious Rectors gold medal for hisfinal year project. From September 2007 till August2008, he served as a Research Assistant on a col-laborative research project between NUST, Pakistanand Ajou University, South Korea. In 2008, he wasawarded overseas research student scholarship alongwith Tetley Lupton and Excellence Scholarships topursue his PhD at the School of Electronics and Elec-trical Engineering, University of Leeds, U.K. He wasalso awarded with COST IC0902, DAAD and RoyalAcademy of Engineering grants to promote his re-search. Dr. Zaidi was a visiting research scien-tist at Qatar Innovations and Mobility Centre fromOctober to December 2013. He is also UK Lia-sion for the European Association for Signal Pro-cessing (EURASIP). He has been serving as co-chairof several special sessions/workshops and symposiain flagship conferences, such as ICC, VTC, CAMADetc. Dr. Zaidi has served as Lead Guest Editor forIET Signal Processing SI on Recent Advances inSignal Processing for 5G Wireless Networks, Editorfor IEEE Communication Letters. He is currentlyAssociate Technical Editor for IEEE Communica-tion magazine.



Interview with Dr. Amitava GhoshNokia, Bell Labs, Email: [email protected]

1) Millimeter wave (mmWave) communicationis seen as a cornerstone technology for next-generation wireless networks, especially to sup-port wireless backhaul. Could you please elab-orate why mmWave backhaul has attracted somuch attention in recent years?

Nokia: mmWave has much more challengingpropagation than traditional cellular bands with re-duced intersite spacing of base stations and mak-ing signals more susceptible to blockage. Fur-ther, the availability of large chunks of bandwidthmake mmWave spectrum suitable for backhaul com-munication having multi-Gbps transfer capacity tosupport both access and backhaul. Recently, 5GmmWave technology is being used for both accessand backhaul and also for integrated access andbackhaul (IAB).

2) Could you please explain typical use case sce-narios of mmWave backhaul (urban vs. rural, in-door vs. outdoor)?

Nokia: Currently, mmWave backhaul links havebeen used mainly for outdoor scenarios. An ex-ample, will be fixed service wireless backhaul sta-tions (WBSs) @ 70 GHz bands used for high fre-quency trading. WBSs are non-uniformly distributedover space, and specifically they tend to have higherdensity near city centers while they become very

sparsely deployed in suburban areas. Another exam-ple would be the backhauling of lamp post deployedin smart city 5G small cell network. In the future,mmWave backhaul will be used to mitigate the lim-its of existing fiber networks connecting a high den-sity mmWave access network through a select fewegress points. mmWave backhaul will be used, inNorth America for example, at 28 GHz and 39 GHzin the short term and higher bands in the future. Inaddition to future 5G networks, mmWave backhaulcan also be used to provide transport connectivity tothe existing legacy mobile systems.

3) Could we expect to see a wide use of mmWavebackhaul in near future? If applicable, pleaseelaborate on the timeline that standardizationbodies and operators have in mind to deploy thefirst generation of mmWave backhaul networks.

Nokia: mmWave outdoor deployment for appli-cations like Last 200 meters to home and Hot SpotDeployment in urban micro scenarios require densedeployments right from the initial phases to getsufficient coverage. It is economically not feasi-ble to provide fiber connectivity to each site untilthe new radio deployments become mature. Self-backhauling, using the same antenna arrays to dy-namically switch between access and backhaul, withoptimized scheduling and dynamic TDD enablingdeployment cost reduction and improving system



performance is needed for making mmWave a fea-sible technology for 5G. The 3GPP study item onIntegrated Access and Backhaul (IAB) will start inJanuary 2018 with standardization in Rel-16 time-frame. It is expected that the first generation 5GIAB technology will be deployed around 2021-2022timeframe.

4) One of the key requirements of backhaul net-works is reliability. Given that mmWave commu-nication is both limited in range and susceptibleto blockage, how mmWave technology can over-come these limitations and provide a reliable andseamless backhaul support?

Nokia: It is true that mmWave should overcomepathloss, blocking, high penetration and diffractionloss. This can be achieved with higher densificationwherein shadowing is mitigated with base station di-versity and rapidly rerouting around obstacles whenuser device is shadowed by an opaque obstacle inits path. The pathloss and blockage at mmWave areovercome by large number of antenna arrays and bymeshed backhaul connections. Wireless mesh net-work (WMN) backhaul with built-in self-organizingnetwork features like on-demand route re-selectionand load balancing will provide fast recovery fromlink failures/blockages and from traffic congestionsituations via the alternative path provided by themesh topology. Another issue for mmWave backhaullinks is to design beam steering algorithms whichtake into account imperfections like pole sway etc.

5) Beyond reliability, are there any other chal-lenges for realizing the mmWave backhaul (e.g.,coexistence with the wired or microwave back-haul)?

Nokia: The other challenge of 5G integrated ac-cess and backhaul systems is that they should co-

exist with incumbents at various mmWave bands.As an example, 28GHz has Fixed Satellite Ser-vices (FSS) as an incumbent globally and is usedfor Earth-to-space gateway-type services in USA. At70 GHz, there are primarily fixed service wirelessbackhaul stations (WBSs) and the 5G mmWave sys-tems should co-exist with these WBS’s. Nokia hasdone detailed co-existence studies @ 28 and 70 GHzbands with the incumbents and recommended to theregulators on how interference from incumbents tothe 5G integrated access and backhaul systems canbe addressed.

6) Could you please briefly introduce the most re-cent research project that you have done for ad-dressing the challenges of mmWave backhaul?

Nokia: We have been involved in several projectsrelated to mmWave. First and foremost Nokia is ac-tively involved in shaping the 3GPP NR specificationboth for mmWave and sub 6 GHz spectrum. Nokiaalso developed a 70 GHz Proof-of-Concept systemfor both backhaul and access. Specifically, we havedeveloped i) multi-hop meshed backhaul network tostudy effect of beam steering, pole sway etc. us-ing lens antenna, ii) Access network which achievesa peak rate of 15 Gbps and includes features likelow latency, dynamic TDD and rapid re-routing us-ing lens antenna and phased arrays. Nokia has atthe latest Mobile World Congress introduced a newcompact 10Gbps E band radio as part of the NokiaWavence Microwave portfolio, which will be sooncommercially available for deployments. Finally, weare working on IAB which is a study item in 3GPPand will be standardized in Rel-16.

7) Beyond your own work, are there any resourcesthat you would like to recommend, especially tothose who are new in this field and want to learnmore about the mmWave backhaul?



Nokia: There is a rich literature on mmWave back-hauling some of which are listed below:

a. S. Singh, M. N. Kulkarni, A. Ghosh, and J.G. Andrews, “Tractable model for rate in self-backhauled millimeter wave cellular networks,”IEEE J. Sel. Areas Commun., vol. 33, no. 10,pp. 21962211, Oct. 2015.

b. S. Hur, T. Kim, D. J. Love, J. V. Krogmeier,T. Thomas, A. Ghosh et al., “Millimeter wavebeamforming for wireless backhaul and accessin small cell networks,” IEEE Trans. Commun.,vol. 61, no. 10, pp. 43914403, Oct. 2013.

c. C. Dehos, J. L. Gonzlclez, A. D. Domenico, D.Ktlenas, and L. Dussopt, “Millimeter-wave ac-cess and backhauling: The solution to the expo-nential data traffic increase in 5G mobile com-munications”.

d. Z. Gao, L. Dai, D. Mi, Z. Wang, M. A. Imran,and M. Z. Shakir, “MmWave massive-MIMO-based wireless backhaul for the 5G ultradensenetwork,” IEEE Wireless Commun., vol. 22,no. 5, pp. 1321, Oct. 2015.

e. S. Nie, G. R. MacCartney, S. Sun, and T. S.Rappaport, “28 GHz and 73 GHz signal out-age study for millimeter wave cellular and back-haul communications,” in Proc. IEEE Int. Conf.Commun. (ICC), 2014, pp. 48564861.

f. M. Cudak, T. Kovarik, T. A. Thomas, A. Ghosh,Y. Kishiyama, and T. Nakamura, “ExperimentalmmWave 5G cellular system,” in Proc. IEEEGlobecom Workshops, Dec. 2014, pp. 377381.

g. J.Salmelin, and E.Metsl. “LTE Backhaul”.Chichester, WS, UK: Wiley, 2016

h. M. Shariat, M. Dianati, K. Seppanen, T.Suihko, J. Putkonen, and V. Frascolla, “En-abling wireless backhauling for next generation

mmWave networks,” in 2015 European Confer-ence on Networks and Communications (Eu-CNC). IEEE, jun 2015, pp. 164168.

i. Z. Du, K. Aronkyto, J. Putkonen, J. Kapanen,E. Ohlmer, D. Swist, “5G E-band BackhaulSystem Measurements in Urban Street-LevelScenarios,” submitted to European MicrowaveWeek, Germany, Nuremberg, 10-12 October2017.

j. Z. Du, K. Aronkyto, J. Putkonen, J. Kapanen, E.Ohlmer, D. Swist, “5G Backhaul System Evalu-ations,” European Conference on Networks andCommunications (EuCNC), Oulu, Finland, 12-15 June 2017.

k. P. Wainio and K. Seppanen, “Self-optimizinglast-mile backhaul network for 5G small cells,”in 2016 IEEE International Conference onCommunications Workshops (ICC). IEEE, may2016, pp. 232239.

l. K. Seppanen, J. Kilpi, J. Paananen, T. Suihko, P.Wainio, and J. Kapanen, “Multipath routing formmWave WMN backhaul,” in 2016 IEEE Inter-national Conference on Communications Work-shops (ICC). IEEE, may 2016, pp. 246253.

m. J. Kilpi, K. Seppanen, T. Suihko, J. Paananen,D. T. Chen, and P. Wainio, “Link schedulingfor mmWave WMN backhaul,” in 2017 IEEEInternational Conference on Communications(ICC). IEEE, may 2017, pp. 17.

n. R. Kalimulin, A. Artemenko, R. Maslennikov,J. Putkonen, and J. Salmelin, “Impact of mount-ing structures twists and sways on point-to-point millimeter-wave backhaul links,” in 2015IEEE International Conference on Communica-tion Workshop (ICCW). IEEE, jun 2015, pp.1924.



o. Juha Ala-Laurinaho, Jouko Aurinsalo, AkiKarttunen, Member, IEEE, Mikko Kaunisto,Antti Lamminen, Juha Nurmiharju, Antti V.Risnen, Fellow, IEEE, Jussi Sily, Pekka Wainio“Two-Dimensional Beam-Steerable IntegratedLens Antenna System for 5G E-Band Ac-cess and Backhaul” IEEE Transactions on Mi-crowave Theory and Techniques (Volume: 64,Issue: 7, July 2016)

p. J. Ala-Laurinaho, A. Karttunen, and A. Raisa-nen, “A mm-wave integrated lens antenna forE-band beam steering,” in Antennas and Prop-agation (EuCAP), 2015 9th European Confer-ence on, 2015, pp. 12.

8) What are the most important open problemsand future research directions towards realizingthe mmWave backhaul solution?

Nokia: The most important problems formmWave backhaul are as follows:

a. How to overcome shadowing due to obstaclesand foliage.

b. Physical layer solutions to support wirelessbackhaul links with high spectral efficiency

c. Self-organizing mesh for wireless backhaul andintegrated access and backhaul

d. How to compensate for pole sway using novelbeamforming algorithms/alignment techniques.

e. Light pole integrated mmWave backhaul solu-tions supporting smart city digital ecosystem in-cluding various sensors and other devices

f. Cost effective implementations includingequipment size, ease of deployment andmaintenance

g. For integrated access and backhaul

a. Topology management for single-hop/multi-hop and redundant connectivity

b. Route selection and optimization

c. Dynamic resource allocation between thebackhaul and access links

h. 5G ultra dense meshed mobile fronthauling andbackhauling @ Ultra-high mmWave band (130-174GHz) for smart cities and enterprise connec-tivity.

Amitabha (Amitava)Ghosh is a Nokia Fel-low and Head, SmallCell Research at NokiaBell Labs. He joinedMotorola in 1990 after

receiving his Ph.D in Electrical Engineering fromSouthern Methodist University, Dallas. Sincejoining Motorola he worked on multiple wirelesstechnologies starting from IS-95, cdma-2000,1xEV- DV/1XTREME, 1xEV-DO, UMTS, HSPA,802.16e/WiMAX and 3GPP LTE. Dr. Ghosh has 60issued patents, has written multiple book chaptersand has authored numerous external and internaltechnical papers. He is currently working on 3GPPLTE-Advanced and 5G technologies. His researchinterests are in the area of digital communications,signal processing and wireless communications. Heis a Fellow of IEEE, recipient of 2016 IEEE StephenO. Rice and 2017 Neal Shephard prize, member ofIEEE Access editorial board and co-author of thebook titled “Essentials of LTE and LTE-A”.



Interview with Prof. David J. LoveSchool of Electrical and Computer Engineering, Purdue University, Email: [email protected]

1) Millimeter wave (mmWave) communicationis seen as a cornerstone technology for next-generation wireless networks, especially to sup-port wireless backhaul. Could you please elab-orate why mmWave backhaul has attracted somuch attention in recent years?

With the exponential growth in wireless data de-mand, operators and original equipment manufactur-ers have begun to look beyond the customary sub-6 GHz bands, which are used by nearly all wire-less broadband applications. The millimeter wavebands, roughly defined as the bands in 20-100 GHz,have been lightly used for commercial applicationsso far. These bands offer the potential to havemulti-gigahertz of new spectrum available for 5Gand beyond. This is an enormous bandwidth increasefor commercial communications and could lead tonewer and better ways to address the growth in datarequirements. In comparison, most studies I haveseen show that there is less than 1GHz of spectrumavailable for licensed broadband today. Of course,millimeter wave has been underutilized for a reason.There are a number of propagation challenges thatmust be overcome. Only recently have hardware ad-vances made transceivers in these bands cost effec-tive.

2) Could you please explain typical use case sce-narios of mmWave backhaul (urban vs. rural, in-

door vs. outdoor)?

Millimeter wave deployments would have themost impact in small cell (i.e., less than 100-500 me-ters) settings. This matches nicely with urban de-ployments. It could be used in either indoor or out-door scenarios. If used indoor, the operator wouldlikely have to be cognizant of propagation challengeswithin the building. Distances could increase in ruralor semi-urban settings.

3) Could we expect to see a wide use of mmWavebackhaul in near future? If applicable, pleaseelaborate on the timeline that standardizationbodies and operators have in mind to deploy thefirst generation of mmWave backhaul networks.

While much talk has focused on millimeter waveaccess, I believe backhaul may enable practical net-work deployments. A backhaul deployment wouldallow for a more closely controlled link, extremelyhigh throughputs, and lower costs. Wireless back-haul could offer reliabilities that compare well withfiber. I believe the most widely used backhaul de-ployment will be self-backhauling, where an oper-ator takes a portion of its spectrum and uses it forbackhaul. This kind of architecture would allow flex-ible small cell deployments with cells connected inan ad hoc manner.

3GPP currently has a study item on Integrated Ac-



cess and Backhaul, which is very exciting. Histori-cally, access and backhaul designs have been strictlypartitioned. 5G and beyond systems, however, mighthave access and backhaul links that are adaptive toeach other and share many design features across thecommunication layers.

From what I understand, millimeter wave back-haul deployments might be seen around the sametime as millimeter wave access deployments, asmany manufacturers have already started designingfor the emerging standard. There has been much dis-cussion about possible 5G NR deployments in 2019.

4) One of the key requirements of backhaul net-works is reliability. Given that mmWave commu-nication is both limited in range and susceptibleto blockage, how mmWave technology can over-come these limitations and provide a reliable andseamless backhaul support?

From what I understand, blockage is more of a se-rious problem in access deployments than in back-haul deployments. Nevertheless, millimeter wavecan overcome these challenges at the physical layerby using larger numbers of antennas than have beenused in previous sub-6 GHz deployments. These an-tennas will allow the transmitter to steer one or morenarrow beams to maximize rate and reliability. Atthe higher layers, millimeter wave deployments willleverage deployment topologies that can adapt to linkblockages or outages in some backhaul links.

5) Beyond reliability, are there any other chal-lenges for realizing the mmWave backhaul (e.g.,coexistence with the wired or microwave back-haul)?

I believe latency is the key challenge. If millime-ter wave backhaul must achieve latencies lower than

those found in LTE, a multi-hop backhauled smallcell deployment will be challenging. There are alsoquestions on what kind of distances operators will tryto deploy. Wired backhauls clearly offer many ben-efits, but operators will have problems scaling wiredbackhaul deployments.

Another issue is electromagnetic exposure. Theskin and the eye absorb millimeter wave signalsquickly. I am not sure how regulatory bodies willhandle millimeter wave access and backhaul connec-tions. The standard specific absorption rate (SAR)regulations in their current form are likely not appli-cable to millimeter wave. More work is necessary toaddress this.

6) Could you please briefly introduce the most re-cent research project that you have done for ad-dressing the challenges of mmWave backhaul?

We have done a substantial amount of work onbeam design and beam alignment. The research ad-dresses how a base station can correctly point itsbeam at a user equipment with one or more antennas.The beam design problem becomes important whenthe system is required to only use a finite number ofpossible beamformers or precoders.

Most recently, my students and I have been work-ing on a National Science Foundation (NSF) projectrelated to millimeter wave networks. The researchteam includes faculty at Purdue, Texas A&M, andthe US Naval Academy. We are looking at physi-cal layer, medium access layer, and network layerenhancements that could work together to supporta highly adaptive (and programmable) millimeterwave system.

My students and I are also working on transmitarchitectures that can adapt to EM exposure con-strained wireless systems. As I mentioned, if theEM exposure regulatory issues are severe, figuringout how to adapt the multiple antenna signal to these



constraints will be critical. This research is fundedby the NSF and jointly conducted by Purdue, NotreDame, and the University of Illinois.

7) Beyond your own work, are there any resourcesthat you would like to recommend, especially tothose who are new in this field and want to learnmore about the mmWave backhaul?

We published an early paper in this area:S. Hur, T. Kim, D. J. Love, J. V. Krogmeier, T.Thomas, A. Ghosh, “Millimeter Wave Beamformingfor Wireless Backhaul and Access in Small Cell Net-works,” IEEE Transactions on Communications, vol.61, no. 10, pp. 4391-4403, Oct. 2013.

There are also multiple IEEE CommunicationsMagazine articles available on millimeter wave,backhaul, and 5G NR.

8) What are the most important open problemsand future research directions towards realizingthe mmWave backhaul solution?

I personally believe that the largest open prob-lem is understanding how millimeter wave systemsshould be regulated. Whatever regulations are en-forced will have tremendous impact on system de-sign and widespread acceptance of these devices.

There are also a large number of issues related tolatency and multi-point deployments. Achieving lowlatencies will be challenging with self-backhaulednetworks.

David J. Love (S’98 - M’05- SM’09 - F’15) received theB.S. (with highest honors),M.S.E., and Ph.D. degrees inelectrical engineering from theUniversity of Texas at Austinin 2000, 2002, and 2004, re-spectively. During the sum-mers of 2000 and 2002, he was

with Texas Instruments, Dallas, TX. Since August2004, he has been with the School of Electrical andComputer Engineering at Purdue University, wherehe is now a Professor. He leads the College of En-gineering Preeminent Team on Efficient SpectrumUsage. He has served as an Editor for the IEEETransactions on Communications, an Associate Edi-tor for the IEEE Transactions on Signal Processing,and a guest editor for special issues of the IEEE Jour-nal on Selected Areas in Communications and theEURASIP Journal on Wireless Communications andNetworking. His research interests are in the designand analysis of communication systems and MIMOarray processing. Dr. Love is an inventor on approx-imately 30 U.S. patent filings, 27 of which have is-sued.

Dr. Love has been recognized as an IEEE Fel-low and Thomson Reuters Highly Cited Researcher(2014,2015). He is a Fellow of the Royal Statisti-cal Society and inducted into Tau Beta Pi and EtaKappa Nu. Along with his co-authors, he won bestpaper awards from the IEEE Communications So-ciety (2016 IEEE Communications Society StephenO. Rice Prize), the IEEE Signal Processing Society(2015 IEEE Signal Processing Society Best PaperAward), and the IEEE Vehicular Technology Society(2009 IEEE Transactions on Vehicular TechnologyJack Neubauer Memorial Award). He has receivedmultiple IEEE Global Communications Conference(Globecom) best paper awards. He was the recipi-ent of the Purdue HKN Outstanding Teacher Awardin Fall 2010, Purdue ECE Graduate Student Associ-ation Outstanding Faculty Award in Fall 2013, andthe Purdue HKN Outstanding Professor Award inSpring 2015 and Fall 2017. He was an invited par-ticipant to the 2011 NAE Frontiers of EngineeringEducation Symposium and 2016 EU-US NAE Fron-tiers of Engineering Symposium. In 2003, Dr. Lovewas awarded the IEEE Vehicular Technology Soci-ety Daniel Noble Fellowship.


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