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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.
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