mmWave Measurement of RF Reflectors for 5G Green

Research ArticlemmWave Measurement of RF Reflectors for5G Green Communications

Tao Hong 1 Jin Yao1 Cong Liu 1 and Fei Qi 2

1School of Electronics and Information Engineering Beihang University Haidian District Beijing China2China Telecom Corporation Limited Beijing Research Institute Beijing China

Correspondence should be addressed to Tao Hong hongtaobuaaeducn

Received 29 November 2017 Accepted 3 April 2018 Published 15 May 2018

Academic Editor Michel Kadoch

Copyright copy 2018 TaoHong et alThis is an open access article distributed under the Creative CommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In recent years with the energy consumption and environmental degradation science and technology embarked on a path ofsustainable development In this situation 5G green communication system has been widely used This paper introduces theapplication of RF reflectors to 5GmmWave where line-of-sight (LoS) blockage is a major hindrance for the coverage In particularwe investigate the lab measurement of RF reflectors which is a critical step from the theory to the practice Furthermore throughthe lab measurement a 3D near-field range migration (RM) imaging algorithm forMIMO array configuration is proposed and thesampling scheme is improved to save the computation time while providing high-quality images

1 Introduction

In 5G communications energy efficiency has become amatter of prime importance for wireless networks A greatdeal of research has been done in the past to reduce energyconsumption Resource allocation heterogeneous networkdeployment transmission scheme optimization and thedevelopment of energy-efficient algorithms have become thefocus of research Small Cell deployment is a widely acceptedstrategy in the industry to achieve various performance andefficiency indicators for the future 5G system Howeverthe deployment of Small Cell base stations generally hasproblems in maintenance and insufficient site resourcesThis paper proposes a method of using the RF reflectorreflecting only the existing wave without additional energyconsumption reducing land occupation savingmaintenanceresources and having higher commercial utilization value

Compared to traditional active repeaters the universalinterest candidates of passive repeaters (PRs) have beeninevitably utilized inmassivemultiple-input-multiple-output(MIMO) system with amultitude of advantages of lower costof maintenance manufacturing and operation

In order to experimentally discuss the information capac-ity of MIMO in multipath environment a PR includes a

power combiner a planar Yagi-Uda antenna and a four-element folded-patch antenna (FPA) array [1 2] The discus-sion results demonstrate that the performance of broad-anglescattering and polarization transition can be implementedSimultaneously the received power and channel capacityof the system gain an achievement that the four-unit PRcan improve the propagation channel in wireless accesssystem

Existing research proposes a system of MIMO channeloperation with tunable passive repeater [3] The PR has amultitude of antennas and a phase-shifter function existsbetween these antennas The elements of the PR can be con-trolled so that a maximized MIMO channel capacity can begained [4] Experimental results can reveal the effectivenessof the proposed passive repeater

Reflect-array antenna is a flat low-profile reflector includ-ing a planar array of microstrip patch elements to reflectthe special beam direction and shape with certain tuningwhen primary source illuminates it [5 6] Compared withconventional parabolic reflector antenna the planar reflect-array plays a more significant role in the MIMO system forthe ability to surface-mount the reflect-array in virtue of itsconvenient deployment lower cost of manufacturing smallvolume low mass and so forth

HindawiWireless Communications and Mobile ComputingVolume 2018 Article ID 8217839 10 pageshttpsdoiorg10115520188217839

2 Wireless Communications and Mobile Computing

(N)(1)

(1)

(1)

(M)

(L)

Variable phase shifters

Tx antennas (T)

Rx antennas (R)

Passive repeater (P)

H０４

H２０

Figure 1 The channel transmission procedure with passive repeater

Reflectors can be used commonly to improve the prop-agation channel conditions and the ability is exhibitedprominently in inherently bad-conditioned environmentMost researches show that PR can improve theMIMO systemperformance becauseMIMOhasmultiple streams to transferrequiring multiple paths [7] In terms of passive repeaterthere is no amplifier and there is no oscillator in the repeater

The use of reflector in MIMO system has opened up anew line of thinking that propagation channel can be changedintentionally for example moving objects To pursue higherperformance gain and drive greater system operational effi-ciency a more active method is required

The mmWave communications utilize the 30ndash300GHzfrequency band with rich spectrum resources for multigi-gabit transmissions which is one of the most promisingtechnologies for 5G [8 9] In [10ndash12] it is shown thatby using a highly oriented antenna array the millimeter-wave band can be allocated to cellular communicationsHigher frequencies lead to higher bandwidth Advanced RFbeamforming techniques using high-gain advanced antennasat millimeter-wave frequencies and MIMO digital beam-forming technology support the development of RF reflectors[13 14] Therefore the study of this paper is based on themillimeter-wave band

The mmWave indoor propagation simulation for real-lifeoffice environments was presented by using 3D shooting-and-bouncing ray tracing and measurement in paper Whatismore the non-line-of-sight (NLoS) channel environment isimproved by devising the new passive repeaters in mmWavefrequency bands and at the same time the repeaters areembodied in the ray tracing procedure

Currently Pozar et al proposed that a broadband reflect-array can be regarded as a PR to solve the problem of blindareas [15] Nevertheless if a very large scattering angle wastested in the case of a physical limitation of the reflect-arraythe aperture efficiency of the reflect-array was reduced to alower rank greatly

2 Basics of Reflect-Array as 5G Repeater

21 Passive Repeater Principle Figure 1 demonstrates theproposed passive repeater In this scheme there are 119873

and 119872 antennas at the transmitter (119879) and receiver (119877)respectively Assume that the signal on the direct path fromthe transmitter to the receiver is weak The PR (119875) locatesamong 119871 antennas The channel matrices from 119879 to 119875 andfrom 119875 to 119877 are denoted by HPT and HRP respectively

The phase shift at the passive repeater is given by

Θ = (1198901198951205791 0d0 119890119895120579119871) (1)

the channel from 119879 to 119877 is denoted by119867 = 119867RPΘ119867PT (2)

where [1205791 120579119871] describes the number of the phase shifts at119871 antennasAs mentioned above the proposed tunable passive

repeater scheme is quite feasible When the number ofantennas available is sufficient the value of the phase shift ispossible to be discrete and binary for example [0 180] degActually some phase shift patterns are randomly assigned toRx which can observe the throughput of the system And Rxfeeds back the best from all those patterns to the repeaterEven if the binary phase shifters are applied a multiple ofphase patterns (2119871) exist Some patterns have no occasionto be tested for pretty good one is allowed and it does nothave to be the best With computational efficiency geneticalgorithm (GA) is so popular due to the readily availablesuboptimal solution Thus GA can ensure the maximumchannel capacity and throughput by deciding which phasepattern is chosen

Figure 2(a) illustrates that there are three kinds of pathconsisting of penetrated paths diffracted paths and reflectedpaths in NLoS area As illustrated in Figure 2(c) all ofthese paths are used in ray tracing simulation In thesepaths a passive repeater is used and a reradiated path isadded to solve the problem that these paths have largelosses in NLoS path Figure 2(b) illustrates a reradiated pathgenerated by the passive repeater The new procedure forthe ray tracing simulation of passive repeater is shown in

Wireless Communications and Mobile Computing 3

WALL

WALL

Tx

Rx

Diffracted pathReflected path

Penetrated path

(a)

WALL

WALL

Tx

Rx


Penetrated path

Reradiated path by passive repeater

(b)

Tx

Rx

Diffracted pathReflected pathPenetrated path

(c)

Tx

Rx

Diffracted pathReflected pathPenetrated pathDirect path + Repeater pattern+ Reradiated path

(d)

Figure 2 Propagation procedure with or without passive repeater

Side viewPower combiner

layerGround plane

layer substrate

Patch 1 Patch 2 Patch 3 Patch 4

y

Patc

h 1

Patc

h 2

Patc

h 3

Patc

h 4

Power combiner

Ground plane Top view (Substrate is not shown here)

y

Yagi-Udaantenna

z

x

A B C D

3135 mm 39mm110 mm

110

mm

75mm

Figure 3 Configuration of one-unit PR

Figure 2(d) Reradiated paths can be acquired by using thebistatic radar cross section (RCS) patterns and the receivingpower of the passive repeater [9] All of paths consistingof direct paths diffracted paths penetrated paths reflectedpaths and reradiated paths can be combined via postprocess-ing

The configuration of the one-unit passive repeater isillustrated in Figure 3 consisting of a power combiner aplanar Yagi-Uda antenna and a four-element FPA arrayBecause of their compact size the FPA elements locate onthe top side of the substrate which are chosen the same asSet 1 in [2] Balance between the antennasrsquo size and gain


Feed source

Reflected equipment Ground

u0

rmn

Rmn

Figure 4 Configuration of microstrip reflect-array

is a significant and versatile design Therefore when highgain is of main focus in industry and academia other flatantenna types with slightly larger sizes can also be chosen tobe satisfied

The most common Yagi-Uda arrays are fabricated withone driven element and two directors and the ground planelies on 025 away from the patch andmerely acts as a reflector[12] In addition the corrugated periodic ground layer withthe appropriate parameters can improve the antenna gain bysupporting or suppressing some of the sidelobes in the H-plane The bottom side power combiner is connected to theinput port of the flat-bottomed antennaThe feed probe of thepatch element passes through the hole in the ground planeand is connected to the input port of the power combiner

In fact the incident wave can point in any directionthrough the PR reflection When receiving the FPA arraythe received electromagnetic (EM) wave can be transmittedto the Yagi-Uda antenna [16] Reference [5] revealed moredetails about the PR

22 Reflect-Array Principle Each element in the PR needs tobe specifically designed to generate the beam in a specificdirection by scattering the incidentwave by appropriate phasecompensation Figure 4 illustrates the structure of a standardmicrostrip reflect-array Because of effect from the reflectedelements the reradiated field was formed by the dipoles in arandom direction

119864 (119906) = 119872sum119898=1

119873sum119899=1

119865 (997888rarr119903 119898119899 sdot 997888rarr119903 119891) 119860 (997888rarr119903 119898119899 sdot 0) 119860 ( sdot 0)sdot exp minus1198951198960 [10038161003816100381610038161003816997888rarr119903 119898119899 minus 997888rarr119903 11989110038161003816100381610038161003816 + 997888rarr119903 119898119899 sdot ] + 119895120601119898119899 (3)

where 119865 is defined as the feed pattern function and 119860 isdefined as the pattern function of the parasitic dipole elementThe position vector for the 119898119899th element is defined by 997888rarr119903 119898119899and for the feed horn antenna is defined by 997888rarr119903 119891 The desiredmain-beam pointing direction of the reflect-array is definedby 0 The phase that is required for the scattered field fromthe 119898119899th element is defined by 120601119898119899

In order for the aperture distribution to reach the desireddirection 0 the condition is described by120601119898119899 minus 1198960 (119877119898119899 + 997888rarr119903 119898119899 sdot 0) = 2119901120587 119901 = 0 plusmn1 plusmn2 (4)

where the distance from the 119898119899th array element to the feedsource is defined by 119877119898119899 that is 119877119898119899 = |997888rarr119903 119898119899 minus 997888rarr119903 119891|1198960 is the wave number and the expression is 1198960 = 1205960119888with 1205960 defined as the working frequency of the frequencyselective surface (FSS) ground

Inwireless communications it is a big deal for eliminatingthe blind spots of base station antennas in a complex streethigh-building district and many occlusions area Typicallyradio frequency (RF) boosters have the ability to enlarge thecellular coverage area while standard RF boosters have highcost of transceivers power supplies cables and so forth andare limited in installation areas [17]

Because of the blockage of the building the signalreceived for a part of users from BS is poor Considering thispoint the signal received for a part of users who are in theocclude areas can be enhanced via using a passive repeater asshown in Figure 5The gray area and the green area representthe area occupied by the building and the area reflected by thepassive repeater respectively

In the actual situation the channel environment is time-varying and becomes relatively complex by moving objectsrough surfaces or sharp edges of objects (such as cars leavesand lampposts) In complex streets from the transmitterto the receiver in the wireless communication process thefrequency of the signal projected on the moving car will beoffset and the scattering phenomenon will affect the wirelesscommunication shown in Figure 6

3 3D Near-Field RM Imaging Algorithm

In the MIMO configuration the 3D image reconstructionprocess can be accomplished analogically on 2D imaging thatis the backscattered data is coherently integrated over the


eNBShadowing

area

Shadowingarea

Buildings

Figure 5 Reviving the signal of shadowing area

scattering

Figure 6 Scattering in complex channel environment

two spatial coordinates of the 2D aperture and measured fre-quency band The antenna array produces spherical waves inthe near field Considering the influence of spatial resolutionand sampling interval this paper uses time slot interpolationto determine a dedicated time and phase to obtain evenlyspaced data [18]

The improved sampling method proposed in this papereffectively solves the problem that the traditional 3D imagingsampling time is too long and saves a lot of sampling timeunder the premise of reducing image distortion [19]

Figure 7 presents a 2D linear MIMO imaging geometrystructure In thewave field of the continuouswave theMIMOarray composed of the transmitting antenna and the receivingantenna illuminates the target plane located near the arrayaperture

In the imaging process shown in Figure 7 the scanningrange is [119871119883 119871119883] the sampling interval is Δ119883 and the stepfrequency of the sampling point is 119891 The target positionis set to (119883 119885) the transmitting antenna and the receivingantenna are located at (119883Tx 0) (119883Rx 0) respectively wherethe subscript in the formula represents the axis119909119910Thereforethe transmit and receive phase delays are 2119896119877 where 119896 =2120587119891119888 119877 = 119877Tx + 119877Rx 119877Tx = radic119883 minus (119883Tx)2 + 1198852 and 119877Rx =radic119883 minus (119883Rx)2 + 1198852

Let the received signal be 119904(119883Tx 119883Rx 119896) and the tar-get reflectivity is 120590(119883 119885) Consider the spreading loss119904(119883Tx 119883Rx 119896) can be expressed as119904 (119883Tx 119883Rx 119896) = 14120587119877Tx119877Rx

120590 (119883 119885)


O

xy

zO

Target zone

Rx antennaTx antenna

Tx antenna

antenna array

y x

R４Ｒ

R２Ｒ

z0

RX

array

Figure 7 2D linear MIMO imaging geometry structure

sdot exp (minus119895119896 (119877Tx + 119877Rx)) (5)

where 119877Tx represents the distance from the transmitter to thetarget and similarly 119877Rx represents the receiverrsquos distance

The Fourier transform is performed on the receivedsignal 119904 (119896119883minus119879 119896119883minus119877 119896) = 14120587120590 (119883 119885) sdot 119865 (119896119883minus119879 119896)

sdot 119865 (119896119883minus119877 119896) (6)

where

119865 (119896119909minus119879 119896) = int exp (minus119895119896119909minus119879119877Tx)119877Tx

119889119883Tx

= 1198952120587119896119911minus119879 exp (minus119895119896119911minus119879 sdot 119885 minus 119895119896119909minus119879 sdot 119883)119865 (119896119909minus119877 119896) = int exp (minus119895119896119909minus119877119877Rx

)119877Rx

119889119883Rx

= 1198952120587119896119911minus119877 exp (minus119895119896119911minus119877 sdot 119885 minus 119895119896119909minus119877 sdot 119883)119896119909 = 119896119909minus119879 + 119896119909minus119877119896119911 = radic1198962 minus 1198962119909minus119879 + radic1198962 minus 1198962119909minus119877

(7)

The above analysis applies to the correspondingtransceiver pair of a single scattering point the followingformula is used to represent the total received wave field119887 (119896119909minus119879 119896119909minus119877 119896) = ∬ 119904 (119896119909minus119879 119896119909minus119877 119896) 119889119909 119889119911

= minus 120587119896119911minus119879119896119911minus119877sdot ∬ 120590 (119883 119885) sdot exp (minus119895119896119909119883 minus 119895119896119911119885) 119889119909 119889119911(8)

So the reflection rate of 2D imaging is calculated as

120590 (119883 119885) = ∬ 119887 (119896119883 119896119885) 119890(119895119896119909119883+119895119896119911119885)119889119896119909119889119896119911= 119894119891119891119905 119887 (119896119883 119896119885) (9)

where

119887 (119896119883 119896119885) = minus119896119909minus119879119896119911minus119879120587 119887 (119896119909 119896119911) (10)

The above algorithmic model describes the specific pro-cess of 2D imaging Similarly a three-dimensional data arraycan be obtained for each pair of transceivers at each samplingpoint which is easily generalized to the 3D range Figure 8shows a MIMO array 3D imaging geometry

So the reflectivity map of 3D imaging is calculated as

120590 (119909 119910 119911) = 181205873∭ ∭ [119904 (119909 119910 119896 1199110) 119890(1198951198961199111199110)]sdot exp [minus119895 (119896119909119909 + 119896119910119910 + 119896119911119911)] 119889119909 119889119910 119889119911sdot exp [minus119895 (119896119909119909 + 119896119910119910 + 119896119911119911)] 119889119896119909 119889119896119910 119889119896119911

(11)

The backscattered data set obtained during the imagingprocess is represented by 119904(119909 119910 119896 1199110) Figure 9 is a completeflow diagram of 3D MIMO-RMA image reconstruction

4 Numerical Simulation andSpatial Sampling Scheme

Figure 10 shows the target used in the numerical simulationThe target includes 27 scattering points and the distancebetween the target center and the antenna array is 075mThe area of the antenna array is 1m times 1m the transmittingantenna and the receiving antenna are separated by 05 cmThe frequency ranges from 8 to 12GHz sampling a total of101 points with a step of 40MHz


O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target

Frequency Sweep and 2-D


track

track

y

x

zone

z0

plane track

O

Figure 8 3D MIMO array imaging geometry structure

Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT

3-D imagereconstruction

s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)

Figure 9 MIMO 3D image reconstruction procedure

Using the proposed MIMO-RMA to reconstruct 3Dreflectivity images the simulation results are shown in Fig-ure 11 The processing time is about 15 s and the dynamicrange is set to 20 dB

Conventional sampling methods usually take severalhours to sample azimuth and elevation angles [20] Still basedon 1m times 1m antenna and 05m sampling step the traditionalsampling scheme requires 2 hours of processing time The

Table 1 Comparison among different schemes

Scheme (a) (b) (c) (d) (e) (f)Dynamic range (dB) 14 3 7 45 5 85Sampling time (min) 120 2 41 2 2 46

improved sampling scheme can save a lot of time and siximproved sampling schemes are as follows in Figure 12

In the simulation experiment we use dynamic rangeand spatial sampling time as the standard to measure theperformance of each sampling scheme

41 Dynamic Range Figure 13 shows the point scatteringmodel which contains 10 sets of scattering points with thesame reflectance For the model the numerical simulationresults of the six sampling schemes are shown in Figure 14

Through the analysis of the results in addition to Fig-ure 14(b) other sampling programs can produce a corre-sponding dynamic range of high-resolution images Scheme(b) lacks the sampling process in the elevation directioncausing some scattering points to be unrecognizable (a) hasa large dynamic range The actual situation often requiresdynamic range conditions of not less than 6 dB so scheme(c) and scheme (f) can be applied for practical use

42 Spatial Sampling Time In different operating systemsthe spatial sampling time may be different A typical systemconsists of a network analyzer that determines the single scantime from the IF bandwidth and the scan point For examplein the N5247A system set the IF bandwidth of 10 KHz andset the 401 scanning points the single scan point of a singlescan time is 155ms [21] The dynamic range and samplingprocessing time of the six sampling schemes are listed inTable 1


Scattering Points Model

x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)

Figure 10 Scattering points model

3-D Reflectivity Map

x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)

Figure 11 3D reflectivity map

O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)

Figure 12 Six spatial sampling schemes


(01 minus03 03)

(02 0 minus02)

(015 minus015 minus015)

(03 minus03 0)(0 minus02 minus01)

(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)



Scheme (a) with dynamic range 14 dB

x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)

Scheme (b) with dynamic range 3 dB

x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)

Scheme (c) with dynamic range 7 dB

x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)

Scheme (d) with dynamic range 45 dB

x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)

Scheme (e) with dynamic range 5 dB

x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)

Scheme (f) with dynamic range 85 dB

x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)

Figure 14 (a) Scheme (a) 14 dB (b) Scheme (b) 3 dB (c) Scheme (c) 7 dB (d) Scheme (d) 45 dB (e) Scheme (e) 5 dB (f) Scheme (f)85 dB

5 Conclusion

In this paper we combine the laboratory measurement of5G RF reflector with the theoretical algorithm to studythe application of RF reflector in solving the line-of-sightblocking problem in millimeter-wave frequency band Anda 3D near-field range migration (RM) imaging algorithmfor MIMO array configuration is proposed The algorithmcan effectively reduce the image distortion and reconstructthe high-quality image Finally by improving the samplingscheme the sampling time is greatly shortened which makesthe whole algorithm more practical

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this paper

References

[1] L Wang S-W Qu J Li Q Chen Q Yuan and K SawayaldquoExperimental investigation of MIMO performance using pas-sive repeater in multipath environmentrdquo IEEE Antennas andWireless Propagation Letters vol 10 pp 752ndash755 2011

[2] S S Yang and KM Luk ldquoWideband folded-patch antennas fedby L-shaped proberdquoMicrowave and Optical Technology Lettersvol 45 no 4 pp 352ndash355 2005

[3] L Zheng and D N C Tse ldquoDiversity and multiplexinga fundamental tradeoff in multiple-antenna channelsrdquo IEEETransactions on Information Theory vol 49 no 5 pp 1073ndash1096 2003

[4] QH Spencer A L Swindlehurst andMHaardt ldquoZero-forcingmethods for downlink spatial multiplexing inmultiuserMIMOchannelsrdquo IEEE Transactions on Signal Processing vol 52 no 2pp 461ndash471 2004


[5] S-W Qu Q-Y Chen Q Chen J Li Q Yuan and K SawayaldquoDualantenna system for elimination of blindness in wirelesscommunicationsrdquo Prog Electromagn Res C vol 21 pp 87ndash972011

[6] B Kim H Kim D Choi Y Lee W Hong and J Park ldquo28 GHzpropagation analysis for passive repeaters in NLOS channelenvironmentrdquo in Proceedings of the 9th European Conference onAntennas and Propagation EuCAP 2015 Lisbon Portugal May2015

[7] J Huang and R J Pogorzelski ldquoA ka-band microstrip reflec-tarray with elements having variable rotation anglesrdquo IEEETransactions on Antennas and Propagation vol 46 no 5 pp650ndash656 1998

[8] W Roh J-Y Seol J Park et al ldquoMillimeter-wave beamformingas an enabling technology for 5G cellular communications the-oretical feasibility and prototype resultsrdquo IEEECommunicationsMagazine vol 52 no 2 pp 106ndash113 2014

[9] T Rappaport S Sun R Mayzus et al ldquoMillimeter wave mobilecommunications for 5G cellular it will workrdquo IEEE Access vol1 pp 335ndash349 2013

[10] G R Maccartney J Zhang S Nie and T S Rappaport ldquoPathloss models for 5G millimeter wave propagation channels inurban microcellsrdquo in Proceedings of the IEEE Global Commu-nications Conference (GLOBECOM rsquo13) pp 3948ndash3953 IEEEAtlanta Ga USA December 2013

[11] S Rajagopal R Taori and S Abu-Surra ldquoSelf-interferencemitigation for in-band mmWave wireless backhaulrdquo in Pro-ceedings of the 2014 IEEE 11th Consumer Communications andNetworking Conference CCNC 2014 pp 551ndash556 LasVegas NVUSA January 2014

[12] J A Zhang S Hay and Y J Guo ldquoDirectional antennasfor point-to-multipoint millimetre wave communicationsrdquo inProceedings of the 6th IEEE-APS Topical Conference onAntennasand Propagation in Wireless Communications IEEE APWC2016 pp 204ndash207 aus September 2016

[13] J G Andrews S Buzzi and W Choi ldquoWhat will 5G berdquo IEEEJournal on Selected Areas in Communications vol 32 no 6 pp1065ndash1082 2014

[14] R Taori and A Sridharan ldquoPoint-to-multipoint in-bandmmwave backhaul for 5G networksrdquo IEEE CommunicationsMagazine vol 53 no 1 pp 195ndash201 2015

[15] D M Pozar S D Targonski and H D Syrigos ldquoDesign ofmillimeter wave microstrip reflectarraysrdquo IEEE Transactions onAntennas and Propagation vol 45 no 2 pp 287ndash296 1997

[16] J Li and P Stoica ldquoMIMO radar with colocated antennasrdquo IEEESignal Processing Magazine vol 24 no 5 pp 106ndash114 2007

[17] P N Vasileiou E D Thomatos K Maliatsos and A GKanatas ldquoAdaptive basis patterns computation for electronicallysteerable passive array radiator antennasrdquo in Proceedings of the2013 IEEE 77th Vehicular Technology Conference VTC Spring2013 Dresden Germany June 2013

[18] J M Lopez-Sanchez and J Fortuny-Guasch ldquo3D radar imagingusing rangemigration techniquesrdquo IEEETransactions onAnten-nas and Propagation vol 48 no 5 pp 728ndash737 2000

[19] A Ferretti C Prati and F Rocca ldquoPermanent scatterers in SARinterferometryrdquo IEEE Transactions on Geoscience and RemoteSensing vol 39 no 1 pp 8ndash20 2001

[20] N Li Y Zhou J Xu and C Hu ldquoA novel method of planar threedimensional synthetic aperture radar imagingrdquo in Proceedingsof the 2012 8th International Symposium on CommunicationSystems Networks and Digital Signal Processing CSNDSP 2012pol July 2012

[21] J Zhao and Z Dong ldquoEfficient Sampling Schemes for 3-D ISARImaging of Rotating Objects in Compact Antenna Test RangerdquoIEEE Antennas and Wireless Propagation Letters vol 15 pp650ndash653 2016

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(N)(1)

(1)

(1)

(M)

(L)

Variable phase shifters

Tx antennas (T)

Rx antennas (R)

Passive repeater (P)

H０４

H２０

Figure 1 The channel transmission procedure with passive repeater

Reflectors can be used commonly to improve the prop-agation channel conditions and the ability is exhibitedprominently in inherently bad-conditioned environmentMost researches show that PR can improve theMIMO systemperformance becauseMIMOhasmultiple streams to transferrequiring multiple paths [7] In terms of passive repeaterthere is no amplifier and there is no oscillator in the repeater

The use of reflector in MIMO system has opened up anew line of thinking that propagation channel can be changedintentionally for example moving objects To pursue higherperformance gain and drive greater system operational effi-ciency a more active method is required

The mmWave communications utilize the 30ndash300GHzfrequency band with rich spectrum resources for multigi-gabit transmissions which is one of the most promisingtechnologies for 5G [8 9] In [10ndash12] it is shown thatby using a highly oriented antenna array the millimeter-wave band can be allocated to cellular communicationsHigher frequencies lead to higher bandwidth Advanced RFbeamforming techniques using high-gain advanced antennasat millimeter-wave frequencies and MIMO digital beam-forming technology support the development of RF reflectors[13 14] Therefore the study of this paper is based on themillimeter-wave band

The mmWave indoor propagation simulation for real-lifeoffice environments was presented by using 3D shooting-and-bouncing ray tracing and measurement in paper Whatismore the non-line-of-sight (NLoS) channel environment isimproved by devising the new passive repeaters in mmWavefrequency bands and at the same time the repeaters areembodied in the ray tracing procedure

Currently Pozar et al proposed that a broadband reflect-array can be regarded as a PR to solve the problem of blindareas [15] Nevertheless if a very large scattering angle wastested in the case of a physical limitation of the reflect-arraythe aperture efficiency of the reflect-array was reduced to alower rank greatly

2 Basics of Reflect-Array as 5G Repeater

21 Passive Repeater Principle Figure 1 demonstrates theproposed passive repeater In this scheme there are 119873

and 119872 antennas at the transmitter (119879) and receiver (119877)respectively Assume that the signal on the direct path fromthe transmitter to the receiver is weak The PR (119875) locatesamong 119871 antennas The channel matrices from 119879 to 119875 andfrom 119875 to 119877 are denoted by HPT and HRP respectively

The phase shift at the passive repeater is given by

Θ = (1198901198951205791 0d0 119890119895120579119871) (1)

the channel from 119879 to 119877 is denoted by119867 = 119867RPΘ119867PT (2)

where [1205791 120579119871] describes the number of the phase shifts at119871 antennasAs mentioned above the proposed tunable passive

repeater scheme is quite feasible When the number ofantennas available is sufficient the value of the phase shift ispossible to be discrete and binary for example [0 180] degActually some phase shift patterns are randomly assigned toRx which can observe the throughput of the system And Rxfeeds back the best from all those patterns to the repeaterEven if the binary phase shifters are applied a multiple ofphase patterns (2119871) exist Some patterns have no occasionto be tested for pretty good one is allowed and it does nothave to be the best With computational efficiency geneticalgorithm (GA) is so popular due to the readily availablesuboptimal solution Thus GA can ensure the maximumchannel capacity and throughput by deciding which phasepattern is chosen

Figure 2(a) illustrates that there are three kinds of pathconsisting of penetrated paths diffracted paths and reflectedpaths in NLoS area As illustrated in Figure 2(c) all ofthese paths are used in ray tracing simulation In thesepaths a passive repeater is used and a reradiated path isadded to solve the problem that these paths have largelosses in NLoS path Figure 2(b) illustrates a reradiated pathgenerated by the passive repeater The new procedure forthe ray tracing simulation of passive repeater is shown in


WALL

WALL

Tx

Rx


Penetrated path

(a)

WALL

WALL

Tx

Rx


Penetrated path


(b)

Tx

Rx


(c)

Tx

Rx


(d)



layerGround plane

layer substrate


y

Patc

h 1

Patc

h 2

Patc

h 3

Patc

h 4

Power combiner


y

Yagi-Udaantenna

z

x

A B C D

3135 mm 39mm110 mm

110

mm

75mm





Feed source


u0

rmn

Rmn






119864 (119906) = 119872sum119898=1

119873sum119899=1











eNBShadowing

area

Shadowingarea

Buildings


scattering







120590 (119883 119885)


O

xy

zO

Target zone


Tx antenna

antenna array

y x

R４Ｒ

R２Ｒ

z0

RX

array





sdot 119865 (119896119883minus119877 119896) (6)

where


119889119883Tx


)119877Rx

119889119883Rx


(7)




120590 (119883 119885) = ∬ 119887 (119896119883 119896119885) 119890(119895119896119909119883+119895119896119911119885)119889119896119909119889119896119911= 119894119891119891119905 119887 (119896119883 119896119885) (9)

where





(11)





O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target



track

track

y

x

zone

z0

plane track

O


Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT


s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)













x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



WALL

WALL

Tx

Rx


Penetrated path

(a)

WALL

WALL

Tx

Rx


Penetrated path


(b)

Tx

Rx


(c)

Tx

Rx


(d)



layerGround plane

layer substrate


y

Patc

h 1

Patc

h 2

Patc

h 3

Patc

h 4

Power combiner


y

Yagi-Udaantenna

z

x

A B C D

3135 mm 39mm110 mm

110

mm

75mm





Feed source


u0

rmn

Rmn






119864 (119906) = 119872sum119898=1

119873sum119899=1











eNBShadowing

area

Shadowingarea

Buildings


scattering







120590 (119883 119885)


O

xy

zO

Target zone


Tx antenna

antenna array

y x

R４Ｒ

R２Ｒ

z0

RX

array





sdot 119865 (119896119883minus119877 119896) (6)

where


119889119883Tx


)119877Rx

119889119883Rx


(7)




120590 (119883 119885) = ∬ 119887 (119896119883 119896119885) 119890(119895119896119909119883+119895119896119911119885)119889119896119909119889119896119911= 119894119891119891119905 119887 (119896119883 119896119885) (9)

where





(11)





O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target



track

track

y

x

zone

z0

plane track

O


Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT


s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)













x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



Feed source


u0

rmn

Rmn






119864 (119906) = 119872sum119898=1

119873sum119899=1











eNBShadowing

area

Shadowingarea

Buildings


scattering







120590 (119883 119885)


O

xy

zO

Target zone


Tx antenna

antenna array

y x

R４Ｒ

R２Ｒ

z0

RX

array





sdot 119865 (119896119883minus119877 119896) (6)

where


119889119883Tx


)119877Rx

119889119883Rx


(7)




120590 (119883 119885) = ∬ 119887 (119896119883 119896119885) 119890(119895119896119909119883+119895119896119911119885)119889119896119909119889119896119911= 119894119891119891119905 119887 (119896119883 119896119885) (9)

where





(11)





O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target



track

track

y

x

zone

z0

plane track

O


Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT


s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)













x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



eNBShadowing

area

Shadowingarea

Buildings


scattering







120590 (119883 119885)


O

xy

zO

Target zone


Tx antenna

antenna array

y x

R４Ｒ

R２Ｒ

z0

RX

array





sdot 119865 (119896119883minus119877 119896) (6)

where


119889119883Tx


)119877Rx

119889119883Rx


(7)




120590 (119883 119885) = ∬ 119887 (119896119883 119896119885) 119890(119895119896119909119883+119895119896119911119885)119889119896119909119889119896119911= 119894119891119891119905 119887 (119896119883 119896119885) (9)

where





(11)





O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target



track

track

y

x

zone

z0

plane track

O


Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT


s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)













x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



O

xy

zO

Target zone


Tx antenna

antenna array

y x

R４Ｒ

R２Ｒ

z0

RX

array





sdot 119865 (119896119883minus119877 119896) (6)

where


119889119883Tx


)119877Rx

119889119883Rx


(7)




120590 (119883 119885) = ∬ 119887 (119896119883 119896119885) 119890(119895119896119909119883+119895119896119911119885)119889119896119909119889119896119911= 119894119891119891119905 119887 (119896119883 119896119885) (9)

where





(11)





O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target



track

track

y

x

zone

z0

plane track

O


Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT


s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)













x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



O

x

y

z

Vertical

Horizontal

Rx and Txantennas

Target



track

track

y

x

zone

z0

plane track

O


Backscattered data

Cross-range 2-D FFT

Filtering

Stolt interpolation

3-D IFFT


s(x y k z0)

F(kx ky k z = z0)

F(kx ky k z = 0)

F(kx ky kz)

(x y z)













x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)



x (m)

02

03

02

minus02

minus01

01

minus03

0

0

0

02

minus02minus02

y (m)

z (m

)


O

x

y

z

(a)

O

x

y

z

(b)

O

x

y

z

(c)

O

x

y

z

(d)

O

x

y

z

(e)

O

x

y

z

(f)



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



(01 minus03 03)

(02 0 minus02)



(0 minus01 02)

(0 01 0)(minus02 02 01)

(minus03 015 015)

(minus015 005 03)

x (m)02

02

0

0

0

02

minus02

minus02

minus02

y (m)

z (m

)




x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(a)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(b)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)(c)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(d)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(e)


x (m)02

02

0

0

0

02

minus02

minus02

minus02y (m)

z (m

)

(f)


5 Conclusion




References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia






















RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


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