A Millimeter Wave Future:

The Renaissance of Wireless Communications

Prof. Theodore (Ted) S. Rappaport Radio Club of America Annual Symposium

New York, NY

November 18, 2016

2016 NYU WIRELESS G. R. MacCartney, S. Sun, T. S. Rappaport, et. al. “Millimeter Wave Wireless

Communications: New Results for Rural Connectivity,” All Things Cellular'16: 5th

Workshop on All Things Cellular Proceedings, in conjunction with ACM MobiCom,

Oct. 7, 2016. https://arxiv.org/pdf/1608.05384v2.pdf

Mobile Traffic Growth

© 2016 T.S. RAPPAPORT 2

Source: Ericsson Traffic Measurements (Q4 2015)

Excludes DVB-H, WiFi, or Mobile WiMax, VoIP is included in data

traffic

Ericsson: 45%+ CAGR

Source: Intel, Sept. 2013

More “Realistic” Models • New Users Are Not “Power Users”

• Modified Rate Plans

• Innovation Bursts

Wireless Data Rates per Generation

3

Plot of generational data rates for 3G, 4G, and 5G networks.

Millimeter Wave spectrum is needed to meet 5G demand .

© 2016 T.S. RAPPAPORT

Wireless Carrier Frequencies Have Not Kept Pace Moore’s Law in the Past 40 Years

4

1976 2016 Increase

Personal Computer

Clock Speed

1 MHz 5 GHz 5,000x

Personal Computer

Memory Size

256 KB 500 GB 2,000,000x

Cellular Phone

Carrier Frequency

850 MHz 2.5 GHz 3x

© 2016 T.S. RAPPAPORT

Spectrum Explosion: Wireless Renaissance

5

AM Radio

FM Radio

TV Broadcast

Wi-Fi

60GHz

Spectrum

Cellular

77GHz

Vehicular

Radar

Active CMOS

IC

Research

T. S. Rappaport, et. al., Millimeter Wave

Wireless Communications,

Pearson/Prentice Hall, c. 2015

Shaded Areas =

Equivalent Spectrum!

© 2016 T.S. RAPPAPORT

mmWave Wavelength Visualization – 60 GHz

6

5 millimeters

16 antennas

Integrated

Circuit

Source: F. Gutierrez, S. Agarwal, K. Parrish, and T.S. Rappaport, “On-Chip Integrated Antenna

Structures in CMOS for 60 GHz WPAN Systems,” IEEE Journal on Selected Areas in

Communications, vol. 27, no. 8, October 2009, pp. 1367 – 1377.

© 2016 T.S. RAPPAPORT

Key Challenges: Range/Capacity/Cost

7

Friis’ Law: • Free-space channel gain ∝ λ2, but antenna gains ∝ 1/ λ2 • Upshot: For fixed physical size antennas in free space, frequency does not matter! • Path loss can be overcome with antenna beamforming, independent of frequency!

Shadowing: Significant transmission losses will occur: • Brick, concrete > 35 dB • Human body: Up to 35 dB • But channel is rich in scattering and reflection, even from people! Enabler!

Millimeter wave works! NLOS propagation uses reflections and scattering • Rappaport, et. al, “Millimeter wave mobile communications for 5G cellular: It will work!” IEEE Access, May 2013

© 2016 T.S. RAPPAPORT

Exploding the Myths of Millimeter Waves

• 60 GHz, 183 GHz, 325

GHz, and 380 GHz for

short-range apps.

• Other frequencies

have little air loss

compared to < 6 GHz

• Worldwide agreement

on 60 GHz! WRC19? T. S. Rappaport, et. al., Millimeter Wave Wireless Communications, Prentice-Hall c. 2015.

9

Accurate path loss models needed

• FCC 16-89 offers up to 28 GHz of new spectrum

• Urban mobile, and Urban/Rural backhaul

becomes interesting with multi-GHz bandwidth

spectrum (data access and fiber replacement)

• Weather and rain pose issues, but antenna

gains and power can overcome

• mmWave is the first mobile spectrum where

adaptive antenna gains will overcome weather

Heavy Rainfall @ 28 GHz

6 dB attenuation @ 1km

T. S. Rappaport et al. Millimeter Wave Mobile Communications for 5G Cellular: It

Will Work! IEEE Access, vol. 1, pp. 335–349, May 2013.

Federal Communications Commission, “Spectrum Frontiers R&O

and FNPRM: FCC16-89,” July. 2016. [Online]. Available: https:

//apps.fcc.gov/edocs public/attachmatch/FCC-16-89A1 Rcd.pdf

NYU WIRELESS: Where it all started

10 © 2016 T.S. RAPPAPORT

28 GHz Measurements in 2012 Dense Urban NYC Environments

11

• 4 TX sites

•33 RX sites

• Pedestrian and vehicular

traffic

• High-rise buildings, trees,

shrubs

• TX sites:

• TX-COL1 – 7 m

• TX-COL2 – 7 m

• TX-KAU – 17 m

• TX-ROG – 40 m

• RX sites:

• Randomly selected near

AC outlets

• Located outdoors in

walkways Rappaport, T.S.; Shu Sun; Mayzus, R.; Hang Zhao; Azar, Y.; Wang, K.; Wong, G.N.;

Schulz, J.K.; Samimi, M.; Gutierrez, F., "Millimeter Wave Mobile Communications

for 5G Cellular: It Will Work!," IEEE Access, no. 1, pp.335-349, May 2013.

© 2016 T.S. RAPPAPORT

28 GHz Channel Sounder

12

TX Hardware

RX Hardware

Y. Azar, G. N. Wong, K. Wang, R. Mayzus, J. K.

Schulz, H. Zhao, F. Gutierrez, D. Hwang, T. S.

Rappaport, “28 GHz Propagation Measurements for

Outdoor Cellular Communications Using Steerable Beam

Antennas in New York City,” 2013 IEEE International

Conference on Communications (ICC), June 9-13, 2013.

T.S. Rappaport,et. al.,”Wideband Millimeter Wave

Propagation Measurements and Channel Models for

Future Wireless Communication System Design, IEEE

Trans. Comm., Vol. 63, No. 9. Sept. 2015. G.MacCartney, et. al., “Indoor Office Wideband

Millimeter Wave Propagation Measurements and Channel

Models at 28 and 73 GHz for ultra-dense 5G Wireless

networks,” IEEE Access, Vol. 3. November 2015.

© 2016 T.S. RAPPAPORT

73 GHz Channel Sounder

13

TX Hardware

RX Hardware

T.S. Rappaport,et. al.,”Wideband Millimeter Wave Propagation Measurements and Channel Models for

Future Wireless Communication System Design, IEEE Trans. Comm., Vol. 63, No. 9. Sept. 2015.

G.MacCartney, et. al., “Indoor Office Wideband Millimeter Wave Propagation Measurements and Channel

Models at 28 and 73 GHz for ultra-dense 5G Wireless networks,” IEEE Access, Vol. 3. November 2015.

© 2016 T.S. RAPPAPORT

Measurements show Millimeter Wave is Revolutionary! Highly directional, only major signal loss is in the “first meter” of propagation

14

Signals arrive within 2 to 5 “lobes” in NYC over

many azimuth angles in Non Line of Sight (NLOS)

Rappaport, T.S.; Shu Sun; Mayzus, R.; Hang Zhao; Azar, Y.; Wang, K.; Wong, G.N.;

Schulz, J.K.; Samimi, M.; Gutierrez, F., "Millimeter Wave Mobile Communications

for 5G Cellular: It Will Work!," Access, IEEE , vol.1, no., pp.335,349, 2013

© 2016 T.S. RAPPAPORT

15

NYU WIRELESS provides Open-source Simulation and Modeling Software Suite For Global Development of 5G Millimeter Wave Wireless Networks

M. Samimi, et. al., “3-D Statistical Channel

Model for Millimeter-Wave,” IEEE

International Conf. on Communications (ICC),

May 2015.

M. Samimi, et. al, “Statistical Channel Model

with Multi-Frequency and Arbitrary Antenna

Beamwidth for Millimeter-Wave Outdoor

Communications,” IEEE Global

Communication Conf. (Globecom), Dec. 2015

M. Samimi, T.S. Rappaport, “3-D Millimeter-

Wave Statistical Channel Model for 5G

Wireless System Design,” IEEE Microwave

Theory and Techniques, Vol. 64, No. 7, pp.

2207-2225, July 2016

Downloads include real world data from

28 GHz and 73 GHz, and many

resources

Publically Available:

http://nyuwireless.com/5g-millimeter-

wave-channel-modeling-software/

or

http://bit.ly/1WNPpDX

© 2016 T.S. RAPPAPORT

16

3GPP/ITU Path Loss Model Flaws > 6 GHz

• Path Loss Data Sources: 30 studies over 5 years, 2 – 73 GHz in 5 cities: o UMa: Aalborg University/Nokia (measured at 2, 10, 18, 28 GHz), NYU/UTA(measured at 38 GHz)

o UMi: NYU (measured at 28, 73 GHz)

o InH: Qualcomm (2.9, 29, 60 GHz), NYU (28, 73 GHz)

o Urban Macrocell (UMa), Urban Microcell (UMi), Indoor Hotspot (InH) environments

We found that 3GPP and ITU channel models are not based on physics.

We asked: Can we use simple physics-based models that isolate the first

meter of propagation loss instead of current 3GPP ABG models?

And we asked: How do 3GPP models perform at different

distances/frequencies than measured?

“WOW! 3GPP models have big errors!” They need to be based in physics.

S. Sun et al., "Investigation of prediction accuracy, sensitivity, and parameter stability of large-scale propagation path loss models for 5G wireless communications," IEEE Transactions on

Vehicular Technology, vol. 65, no. 5, pp. 2843-2860, May 2016. http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7434656

17

• Alpha-Beta-Gamma (ABG) Model used by 3GPP/ITU

• NYU Close-In Free Space Reference Distance (CI) Model with 1 m reference

• MMSE method minimizes shadow fading standard deviation σ

• ABG model: o Only valid over the distance range of d and frequency range of f

o Three parameters (α, β, and γ) need to be optimized

• CI model: o n is path loss exponent (PLE)only one parameter to optimize

o stable and accurate outside of measurement distance and frequency range

3GPP Channel Models

UMi, UMa, and InH scenarios

S. Sun et al., "Investigation of prediction

accuracy, sensitivity, and parameter

stability of large-scale propagation path

loss models for 5G wireless

communications," IEEE Transactions on

Vehicular Technology, vol. 65, no. 5, pp.

2843-2860, May 2016.

http://ieeexplore.ieee.org/stamp/stamp.jsp?

arnumber=7434656

32.4 dB @ 1 GHz = 32.4 + 20 log (1)

72.4 dB @ 100 GHz = 32.4 + 20 log (100) =

18

Modeling Performance of ABG and CI Models

ABG and CI modeling parameters in the UMa and UMi scenarios across different frequencies and distances in

the NLOS environment http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7434656

Fit to Measured Data: Comparable! Note CI uses one parameter, ABG uses 3 parameters

Sometimes the 3GPP ABG model uses unrealistic values, not based on physics

n

Channel Modeling for mmWave bands

19

T. S. Rappaport, et. al., "Wideband

Millimeter-Wave Propagation

Measurements and Channel Models for

Future Wireless Communication System

Design," in IEEE Transactions on

Communications, vol. 63, no. 9, pp. 3029-

3056, Sept. 2015.

NYU proposed a global standard for channel modeling: a 1 meter “free space” close-in reference distance to properly account for frequency-dependent path loss from 500 MHz to 100 GHz (> 2 OOM). Adopted as “optional” in 3GPP TR38.900

© 2016 T.S. RAPPAPORT

20

Example of model inaccuracies in 3GPP

“legacy ABG” approach

The currently approved 3GPP model (ABG on left) has noticeable errors at close-in distances.

3GPP (ABG on left) predicts much less path loss compared with free space in first 100 m (10 dB).

Optional close-in (CI) ref. distance models (center and right) do not have this problem.

S. Sun et al., "Investigation of prediction accuracy, sensitivity, and parameter stability of large-scale propagation path loss models for 5G wireless

communications," IEEE Transactions on Vehicular Technology, vol. 65, no. 5, pp. 2843-2860, May 2016.

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7434656

21

Example of 3GPP model inaccuracies

The ABG model underestimates

path loss at short distances, and

overestimates path loss (i.e.,

underestimates interference) at

large distances (e.g. >500 m)

compared with the CI model

The CI/CIF models are more

conservative and accurate when

analyzing interference-limited

systems at large distances and

more realistic when modeling signal

strengths at close-in distances.

S. Sun et al., "Investigation of prediction accuracy, sensitivity, and parameter stability of large-scale propagation path loss models for 5G wireless

communications," IEEE Transactions on Vehicular Technology, vol. 65, no. 5, pp. 2843-2860, May 2016.

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7434656

• 3GPP RMa LOS path loss model

• 3GPP RMa NLOS path loss model

22

3GPP TR38.900 Rural Macrocell (RMa)

3GPP TR 38.900 for > 6 GHz

Adopted from ITU-R M.2135

Long & confusing equations!

Not physically based

Numerous parameters

Confimed by mmWave data? 3GPP, “Technical specification group radio access network; channel

model for frequency spectrum above 6 GHz (release 14),” 3rd

Generation Partnership Project (3GPP), TR 38.900 V14.1.0, Sept.

2016. [Online]. Available: http://www.3gpp.org/DynaReport/38900.htm

ITU, “Guidelines for evaluation of radio interface technologies for IMT-

Advanced,” Geneva, Switzerland, REP. ITU-R M.2135-1, Dec. 2009.

G. R. MacCartney, et. al.,“Millimeter Wave Wireless Communications:

New Results for Rural Connectivity,” All Things Cellular'16: 5th

Workshop on All Things Cellular Proceedings, in conjunction with ACM

MobiCom, Oct. 7, 2016 https://arxiv.org/pdf/1608.05384v2.pdf

23

3GPP RMa Model has errors like ABG

EXAMPLE: We ran current ITU/3GPP path

loss model using Monte Carlo simulations

(before the breakpoint). Example: 6 GHz.

KEY OBSERVATION: Existing 3GPP RMa

NLOS path loss model underestimates path

loss well below free space value at close-in

distances within 50 m, and has obvious errors

(NLOS should be much lossier than free

space) in first 500 meters.

For 6 GHz, CI model using n=2 (LOS) and

n=2.8 (NLOS) predicts much more accurately

for first several hundred meters at 6 GHz with

same std. dev. and improved stability as

shown for CI models, see:

http://ieeexplore.ieee.org/document/7434656/

24

World’s first Rural Macrocell (RMa)

Measurements Above 6 GHz

No careful measurements had ever been published for Rural mmWave!

Conducted Rural Experiments in Riner, Virginia with 190 dB measurement range

TX power 14.7 dBm (29 mW) and equivalent 80 MHz bandwidth channel at 73 GHz

14 LOS locations, 17 NLOS locations, 5 outages

33 m to 10.8 km for LOS scenarios

3.4 km to 10.6 km for NLOS scenarios

TX location: top of mountain ridge (~110m above terrain), fixed downtilt of 2º

TX and RX antennas: 27 dBi of gain and 7º azimuth and elevation half-power beamwidth

Distances over 10 km routinely achieved for head mounted RX, even in NLOS!

G. R. MacCartney, S. Sun, and T. S. Rappaport, Y. Xing, H. Yan, J. Koka, R. Wang, and D. Yu,

“Millimeter Wave Wireless Communications: New Results for Rural Connectivity,” All Things

Cellular'16: 5th Workshop on All Things Cellular Proceedings, in conjunction with ACM MobiCom,

Oct. 7, 2016. https://arxiv.org/pdf/1608.05384v2.pdf

25

73 GHz TX Equipment in Field

26

TX View of Horizon

View to the North

from Transmitter.

Note mountain on

left edge, and the

yard slopes up to

right, creating a

diffraction edge with

TX antenna if TX

points too far to the

right.

TX beam headings

and RX locations

were confined to the

center of the photo

to avoid both the

mountain and the

right diffraction edge

G. R. MacCartney, et. al.,

“Millimeter Wave Wireless

Communications: New

Results for Rural

Connectivity,” All Things

Cellular'16: 5th Workshop on

All Things Cellular

Proceedings, in conjunction

with ACM MobiCom,, 2016.

https://arxiv.org/pdf/1608.05

384v2.pdf

27

Schematic of TX Location and Surroundings

Close-up

around the TX

(not drawn to scale)

TX antenna:

Placed on porch of the house

No obstructions or diffraction edges

31 m from the house (TX) to mountain edge

2º downtilt – avoids diffraction by mountain edge

TX about 110 m above terrain

Provided ~11 km measurement range

28

Map of RMa Locations @ 73 GHz

TX Location

LOS Scenario

NLOS Scenario

TX Azimuth Angle

of View (+/- 10º of

North) to avoid

diffraction from

mountain on left

and yard slope

on right

29

73 GHz RX Equipment in Field

30

RX 5 LOS Location: 6.93 km

LOS with one tree blocking

31

RX 15 LOS Location: 3.44 km

LOS with one tree blocking

32

RX 23 NLOS Location: 5.72 km

Hills and foliage

create NLOS scenario

33

RX 26 LOS Location: 7.67 km

TX location at house – LOS location

34

73 GHz RMa Path Loss Data and Models

Diamonds are LOS locations with partial diffraction from

TX azimuth departure angle from close-in mountain edge

on the right, causing diffraction loss on top of free space

35

Rural Macrocell (RMa) for 5G

mmWave communication links will be useful to rural distances > 10 km (RMa).

Existing 3GPP LOS RMa path loss models are not proven, not defined above 9.1

GHz due to the breakpoint. Proposed CI path loss model (already optional for

UMa, UMi, InH), is simple, accurate, verified. Further NYU work is including a TX

height factor in the PLE.

Proposal: 3GPP and ITU RMa models, or make the CI RMa path loss models

optional . This is based on measurements and physics, 1 m to 10 km and carrier

frequencies of 500 MHz to 100 GHz. Ideal for RMa TR 38.900 3GPP:

G. R. MacCartney, S. Sun, T. S. Rappaport, Y. Xing, H. Yan, J. Koka, R. Wang, and D. Yu, “Millimeter Wave Wireless Communications: New Results for

Rural Connectivity,” All Things Cellular'16, 5th Workshop on All Things Cellular Proceedings, in conjunction with ACM MobiCom , Oct. 7, 2016.

https://arxiv.org/pdf/1608.05384v2.pdf

© T.S. Rappaport 2014

5G System Simulations: SNR

• Simulation assumptions:

• 200m ISD (1W, 50 dB total Ant. gain)

• 3-sector hex BS

• 20 / 30 dBm: UL/DL power

• 8x8 antenna at BS

• 4x4 (28 GHz), 8x8 (73 GHz) at UE

• A new regime: • High SNR on many links!

• Better than current macro-cellular

• Interference is non dominant

S. Rangan, T. S. Rappaport, and E. Erkip,

“Millimeter-Wave Cellular Wireless Networks:

Potentials and Challenges,” Proceedings of the

IEEE, vol. 102, no. 3, pp. 366-385, March 2014.

© T.S. Rappaport 2014

Comparison to Current LTE

• Initial 5G results (very conservative) show significant gain over LTE w/ 1 GHz TDD

• Further gains with spatial mux, subband scheduling and wider bandwidths

System

antenna

Duplex

BW

fc

(GHz)

Antenna Cell throughput

(Mbps/cell)

Cell edge rate

(Mbps/user, 5%)

DL UL DL UL

mmW 1 GHz

TDD

28 4x4 UE

8x8 eNB

1514 1468 28.5 19.9

73 8x8 UE

8x8 eNB

1435 1465 24.8 19.8

Current

LTE

20+20

MHz FDD

2.5 (2x2 DL,

2x4 UL)

53.8 47.2 1.80 1.94

~ 25x gain ~ 10x gain

10 UEs per cell, ISD=200m,

hex cell layout

LTE capacity estimates from 36.814

M. R. Akdeniz, ,Y. Liu, M. K. Samimi, S. Sun, S. Rangan, T. S. Rappaport,

E. Erkip, “Millimeter Wave Channel Modeling and Cellular Capacity

Evaluation,” IEEE. J. Sel. Areas on Comm., July 2014

© T.S. Rappaport 2014

Results by Nokia for 73 GHz

* Assumes RF BW of 2.0 GHz, NCP-SC Modulation (2X BW from NYU study)

* Symbol Rate 1.536 Gigasymbols/sec (50 X LTE)

* Access Point Array: 4 sectors, dual 4X4 polarization

* Ideal Channel State estimator and Fair Scheduler

* Beamforming using uplink signal

Simulation Results at mobile user (UE):

4X4 array: 3.2 Gbps (15.7 Gbps peak), 19.7% outage

8X8 array: 4.86 Gbps (15.7 Gbps peak), 11.5% outage

Outage can be reduced by denser cells, smart repeaters/relays

A. Ghosh ,T. A. Thomas ,M. Cudak, R. Ratasuk, P. Moorut, F. W. Vook, T. S. Rappaport, G. R. MacCartney, Jr., S. Sun, S. Nie, “Millimeter Wave

Enhanced Local Area Systems: A High Data Rate Approach for Future Wireless Networks,” IEEE J. on Sel. Areas on Comm., July 2014.

The Renaissance of Wireless is at hand

•mmW mobile offers 1000x capacity over 4G/LTE

•Experimental confirmation in NYC, Texas in 2011-2014

◦ 200 m cell radius very feasible using only 1 Watt

◦ Much greater range (>450 m) through beam combining

◦ Simulations show multi-Gbps mobile data is viable

Rural measurements show > 10 km possible

◦ NYU WIRELESS announces Open-Source Statistical Spatial Channel Model software suite for 5G

◦ Complete simulator, extensive resources, field data at:

◦ http://nyuwireless.com/5g-millimeter-wave-channel-modeling-software/

◦ http://bit.ly/1WNPpDX

39 © 2016 T.S. RAPPAPORT

40

Acknowledgment

Acknowledgement to our

NYU WIRELESS Industrial

Affiliates and NSF

Grants: 1320472, 1302336, and

1555332

41

Questions

Thank You

42

References

1. G. R. MacCartney, S. Sun, T. S. Rappaport, Y. Xing, H. Yan, J. Koka, R. Wang, and D. Yu, “Millimeter Wave Wireless Communications: New

Results for Rural Connectivity,” All Things Cellular'16: 5th Workshop on All Things Cellular Proceedings, in conjunction with ACM MobiCom,

Oct. 7, 2016.

2. S. Sun et al., "Investigation of Prediction Accuracy, Sensitivity, and Parameter Stability of Large-Scale Propagation Path Loss Models for 5G

Wireless Communications," in IEEE Transactions on Vehicular Technology, vol. 65, no. 5, pp. 2843-2860, May 2016.

3. Aalto University, BUPT, CMCC, Nokia, NTT DOCOMO, New York University, Ericsson, Qualcomm, Huawei, Samsung, Intel, University of

Bristol, KT Corporation, University of Southern California, “5G Channel Model for Bands up to 100 GHz”, Dec. 6, 2015. Technical report.

4. 3GPP. Technical specification group radio access network; channel model for frequency spectrum above 6 GHz. TR 38.900, 3rd Generation

Partnership Project (3GPP), September 2016, V.14.1.0.

5. 3GPP. New measurements at 24 GHz in a rural macro environment. Technical Report TDOC R1-164975, Telstra, Ericsson, May 2016.

6. K. Haneda et al. 5G 3GPP-like channel models for outdoor urban microcellular and microcellular environments. In 2016 IEEE 83rd Vehicular

Technology Conference (VTC2016-Spring), May 2016.

7. K. Haneda et al. Indoor 5G 3GPP-like channel models for office and shopping mall environments. In 2016 IEEE International Conference on

Communications Workshops (ICCW), May 2016.

8. International Telecommunications Union. Guidelines for evaluation of radio interface technologies for IMT-Advanced. REP. ITU-R M.2135-1,

Geneva, Switzerland, Dec. 2009.

9. Y. Ohta et al. A study on path loss prediction formula in microwave band. Technical report, IEICE Technical Report, A P2003-39, Mar. 2003.

10. S. Sakagami and K. Kuboi. Mobile propagation loss predictions for arbitrary urban environments. Electronics and Communications in Japan,

74(10):17–25, Jan. 1991.

11. S. Ichitsubo et al. Multipath propagation model for line-of-sight street microcells in urban area. IEEE Transactions on Vehicular Technology,

49(2):422–427, Mar. 2000.

12. International Telecommunications Union. Proposed propagation models for evaluating radio transmission technologies in IMT-Advanced.

Technical Report Document 5D/88-E, Jan. 2008.

13. T. S. Rappaport. The wireless revolution. IEEE Communications Magazine, 29(11):52–71, Nov. 1991.

14. T. S. Rappaport. Wireless Communications: Principles and Practice. Prentice Hall, Upper Saddle River, NJ, second edition, 2002.

15. T. S. Rappaport et al. Millimeter Wave Mobile Communications for 5G Cellular: It Will Work! IEEE Access, 1:335–349, May 2013.