Millimeter-Wave (mmwave) Radio Propagation Characteristics

Transcription

1 Chapter 7 Millimeter-Wave (mmwave) Radio Propagation Characteristics Joongheon Kim Contents 7. Introduction Propagation Characteristics High Directionality Noise-Limited Wireless Systems Propagation Models and Parameters Path Loss Models Millimeter Wave Specific Attenuation Factors Oxygen Attenuation Rain Attenuation Link Budget Analysis Shannon Capacity Based Calculation with Signal-to-Noise Ratio Computation IEEE 8.ad Baseband-Based Calculation in 6 GHz mmwave Channels Concluding Remarks References K6645_C7.indd 46 /5/5 8:33 PM

2 46 Opportunities in 5G Networks AU: The sentence beginning To quantify has been changed. Please check the meaning. AU: The sentence beginning Section 7.4 has been changed. Please check the meaning. 7. Introduction Today, millimeter-wave (mmwave) wireless communication technologies are considered as one of the major elements of fifth-generation (5G) wireless cellular network evolution. This is because mmwave wireless systems can provide an extremely ultrawide channel bandwidth and therefore, a linear increase in achievable data rates with the ultrawide bandwidth. Even though mmwave 5G wireless networks have many benefits based on the ultrawide bandwidth, the propagation of mmwave wireless links is high directional and is also highly attenuated due to its high carrier frequency (from around 3 to 3 GHz). To quantify the directionality and attenuation factors, this chapter provides an intensive summary of the International Telecommunication Union (ITU) standard documents for carrying out research on mmwave radio wave propagation characteristics. The summary includes ITU-standardized antenna radiation patterns, path loss models, mmwave-specific attenuation factors in mmwave wireless systems, and so forth. Based on the given models and parameters, a link budget calculation is performed to identify how much distance is achievable with given threshold data rates in mmwave wireless propagation links. Note that this chapter mainly pays attention to 8, 38, and 6 GHz mmwave wireless channels, which are the most investigated for 5G cellular and peer-to-peer wireless access networks. The remainder of this chapter is organized as follows. Section 7. gives an overview of mmwave characteristics, including high directionality and background noise calculation. Section 7.3 presents propagation models and parameters, including path loss models and mmwave-specific attenuation factors. Section 7.4 presents the link budget calculation results, both theoretical and practical using IEEE 8.ad. Finally, Section 7.5 concludes the chapter. AU: Does intensive here mean extensive or brief? AU: The sentence beginning Therefore has been changed. Please check the meaning. 7. Propagation Characteristics Even though the use of mmwave radio technologies is attractive due to their large bandwidth availability, they have high directionality, which is positive in terms of mmwave network device densification (due to spatial reuse) but negative in terms of beam-tracking overheads (harmful in terms of mobility support []). Therefore, it is necessary to quantify the beamwidth of directional beams. In Section 7.., the directionality of mmwave beams is determined based on an ITU recommendation. In addition, the mmwave system is noise limited, whereas conventional cellular systems are interference limited. Thus, background noise in 8, 38, and 6 GHz mmwave systems is identified in Section High Directionality The directionality of wireless radio propagation depends on antenna types and corresponding parameters. Without loss of generality, this chapter considers ITU-standard K6645_C7.indd 46 /5/5 8:33 PM

3 Millimeter-Wave (mmwave) Radio Propagation Characteristics 463 antenna radiation patterns. The ITU-recommended reference antenna radiation patterns for sharing studies from 4 MHz to about 7 GHz are presented in an ITU recommendation as follows []: G ( ϕθ, ) = Gmax x x < Gmax 5ln x x where: G(φ, θ) is the antenna gain φ and θ are azimuth and elevation angles, where 8 φ 8 and 9 φ 9 x is defined as AU: Is 9 φ 9 correct here or should φ be changed to θ? x = ℵ ℵ α where ℵ and ℵ α can be formulated as ( ) ℵ= cos cosϕ sinθ ℵ α = cosα + sinα ϕ θ bw bw cosθ ϕ + sinθ 3m θ bw ℵ 9 9 ℵ 8 where: φ bw and θ bw are the half power beamwidth (HPBW) in azimuth and elevation planes α = tan (tanθ/sinφ) φ 3m is the equivalent HPBW in the azimuth plane for adjustment of horizontal gains (degrees) Thus, it can be calculated as follows: K6645_C7.indd 463 /5/5 8:33 PM

4 464 Opportunities in 5G Networks ϕ 3m = ϕ ϕ cos 8 ϕ ϕbw th th ϕ ϕ ϕ 9 bw ϕ ϕ sin 8 ϕ + θbw th th 9 ϕ th th ϕ 8 where φ th is defined as the boundary azimuth angle (degrees), that is, φ th =φ bw; φ bw and θ bw can be calculated as follows []: θ bw and we assume φ bw θ bw, that is, ϕ bw 3, = ϕ bw Gmax / max/ θ 3, bw ( G ) Based on these given models, the HPBW values for various G max values are summarized in Table 7.. Based on the models presented in this section, the ITU-standard antenna radiation pattern can be plotted. Figures 7. and 7. present azimuth plane plotting and elevation plane plotting, respectively. Table 7. Beam Directionality G max (dbi) HPBW K6645_C7.indd 464

5 Millimeter-Wave (mmwave) Radio Propagation Characteristics Azimuth G max = 3 dbi G max = 4 dbi G max = 5 dbi Gain (dbi) Angle (degrees) Figure 7. Azimuth plane plotting. 3 Elevation G max = 3 dbi G max = 4 dbi G max = 5 dbi Gain (dbi) Angle (degrees) Figure 7. Elevation plane plotting. 7.. Noise-Limited Wireless Systems The performance of wireless systems with a large channel bandwidth can be affected by background noise levels in the system. In 6 GHz wireless standards (such as IEEE 8.ad and IEEE 8.5.3c), the channel bandwidth is defined as.6 GHz. With a bandwidth of.6 GHz, the background noise can be calculated as follows [3]: n = k T + log BW + L + n dbm B e implementation F K6645_C7.indd 465

6 466 Opportunities in 5G Networks where: n dbm is the background noise on a decibel scale k B T e is the noise power spectral density, which is 74 dbm/hz BW is the channel bandwidth (i.e..6 GHz) L implementation is the implementation loss, assumed by the IEEE 8.ad standard to be db is a noise figure, assumed by the IEEE 8.ad standard to be 5 db n F Then, n dbm = dbm and n m watt = ( ndbm/) where n mwatt is the background noise on a milliwatt scale. Therefore, the background noise is.7 W. In 8 and 38 GHz mmwave wireless systems, the background noise values can be calculated in the same way under the assumption that the channel bandwidths in 8 and 38 GHz are and 5 MHz, respectively. Finally, the background noise value in 8 GHz is dbm (equivalent to.5 W) and the background noise value in 38 GHz is 7.3 dbm (equivalent to 6.9 W). As shown in this calculation, the noise in 6 GHz bands is almost and 4 times higher than the noise in 8 and 38 GHz bands, respectively. 7.3 Propagation Models and Parameters This section explains two major attenuation factors in mmwave wireless channels depending on the distance between transmitter and receiver: path loss models and auxiliary additional attenuation (such as attenuation by oxygen absorption and rain attenuation). The mmwave path loss models are presented in Section 7.3. and the auxiliary additional mmwave attenuation factors in Section Path Loss Models Free-space basic transmission (i.e., line-of-sight [LOS]) loss is determined as a function of the distance between transmitter and receiver [4] on a decibel scale: ( km ) = + + PL d log f n log d where: d km is the distance between transmitter and receiver (kilometers) f stands for the carrier frequency (gigahertz) n is the path loss coefficient, equal to. when f [5] km K6645_C7.indd 466

7 Millimeter-Wave (mmwave) Radio Propagation Characteristics 467 This equation is defined by the ITU. The measurement-based 8 and 38 GHz path loss models are derived as summarized in [6]. The fundamental equation is PL d ( ) = 4πd log λ n + log d X d + σ where: d is the distance between transmitter and receiver (meters) d is the close-in free-space reference distance (set to d = 5 m) λ is the wavelength (.7 mm in 8 GHz and 7.78 mm in 38 GHz) n is the average path loss coefficient over distance and all pointing angles Xσ is a shadowing random variable, which is represented as a Gaussian random variable with zero mean and σ standard deviation n and σ are summarized in Table 7. [7,8] The measurement-based 6 GHz path loss models are presented in IEEE 8.ad standard documents. As defined in [9], a 6 GHz mmwave IEEE 8.ad LOS path loss model is ( ) = + + PL d A log f n log d on a decibel scale, where A = 3.5 db. This value is specific for the selected type of antenna and beam-forming algorithms, which depend on the antenna beamwidth, Table 7. Path Loss Exponent (n) and Standard Deviations of Shadowing Random Variables (σ) Configuration n σ 5 dbi antenna at 38 GHz 3.3 dbi antenna at 38 GHz LOS..3 NLOS LOS. 9.4 NLOS dbi antenna at 8 GHz LOS NLOS Source: Y. Azar et al. 8 GHz propagation measurements for outdoor cellular communications using steerable beam antennas in New York City, in Proceedings of IEEE International Conference on Communications (ICC), Budapest, IEEE, 3. K6645_C7.indd 467

8 468 Opportunities in 5G Networks but for the considered beam range from 6 to, the variance is very small, less than. db. In this equation, n refers to the path loss coefficient, which is set to n =, and f stands for a carrier frequency on a gigahertz scale, set to f = 6. Note that there is no shadowing effect in the LOS path loss model as presented in [9]. The non-line-of-sight (NLOS) model of the 6 GHz mmwave IEEE 8.ad standards is defined as [9] ( ) = PL d A log f n log d Xσ on a decibel scale, where A = 5.5 db is the value for the selected type of antenna and beam-forming schemes. This value depends on the antenna beamwidth, and the variance is very small, less than. db in the considered beam range from 8 to. In this model, n =.6 and f = 6, as previously defined. Finally, X σ stands for the shadowing effects due to NLOS, which can be calculated by Gaussian distribution with zero mean and standard deviation σ, where σ = 3.3 db. The 6 GHz mmwave IEEE 8.ad path loss model in NLOS has a randomness of X σ. LOS and NLOS path loss plotting in 6 GHz mmwave IEEE 8.ad wireless systems is shown in Figure Millimeter Wave Specific Attenuation Factors As stated in [5], there are two mmwave-specific auxiliary attenuation factors: oxygen attenuation and rain attenuation IEEE 8.ad LOS IEEE 8.ad non-los IEEE 8.ad non-los (average) Path loss (db) Distance (m) 5 3 Figure 7.3 Path loss comparison in 6 GHz mmwave IEEE 8.ad standards. K6645_C7.indd 468

9 Millimeter-Wave (mmwave) Radio Propagation Characteristics 469 Standard Attenuation (db/km) Dry 6 6 GHz.3 38 GHz. 8 GHz 3 Carrier frequency (GHz) 3 Figure 7.4 Oxygen attenuation factors in mmwave channels Oxygen Attenuation The signal attenuation in wireless mmwave radio propagation due to oxygen absorption is significant, and it cannot be ignored. Figure 7.4 shows experimental results for wireless radio wave propagation attenuation in mmwave channels. The oxygen attenuation in 8, 38, and 6 GHz is.,.3, and 6 db/km, respectively. As shown in Figure 7.4, the performance degradation in terms of oxygen attenuation in 6 GHz bands is extremely poor. This is the main reason why 6 GHz mmwave bands are left unlicensed []. AU: The sentence beginning Figure 7.4 has been changed. Please check the meaning Rain Attenuation The signal attenuation in wireless mmwave radio propagation due to rainfall is also significant and cannot be ignored. From the table of Rain Climatic Zones in [], rain rate information in millimeters per hour can be obtained for each segmented area. For example, Northern California, Oregon, and Washington in the United States are in ITU Region D. In addition, the heaviest rain area is ITU Region Q (including the middle of Africa). The table is reproduced in this chapter as Table 7.3. It shows that the rain rates in ITU Region D with % outage (i.e., 99% availability) and.% outage (i.e, 99.9% availability) are. and 8 mm/h, respectively, while the rain rates in ITU Region Q with % outage and.% outage are 4 and 7 mm/h, respectively. AU: The sentence beginning The table is reproduced has been changed. Please check the meaning. K6645_C7.indd 469

10 47 Opportunities in 5G Networks AU: Text following caption has been moved to Note at end of Table 7.3. Please verify. Table 7.3 Rain Rates Depending on Rain Climatic Zones Percentage of Time A B C D E F G H J K L M N P Q. < Source: ITU Recommendation, Characteristics of precipitation for propagation modelling, ITU-R PN.837-, 994. Note: Rainfall intensity exceeded (mm/h) (Figures through 3). K6645_C7.indd 47

11 Millimeter-Wave (mmwave) Radio Propagation Characteristics mm/h mm/h Specific attenuation, ϒ R (db/km) mm/h 5 mm/h 5 mm/h.5 mm/h.5 mm/h 6 GHz 38 GHz 8 GHz Frequency (GHz) 5 AU: The sentence beginning The actual impacts has been changed. Please check the meaning. Figure 7.5 Attenuation by rain rates. (Federal Communications Commission (FCC), Office of Engineering and Technology, Bulletin Number 7, 997.) Based on this rain rate information, rain attenuation factors can be obtained [], and measurement-based curves for the specific attenuation in each frequency depending on the rain rate can be obtained, as shown in Figure 7.5 []. Rain attenuation factors in decibels per kilometer can also be obtained (Figure 7.5, Table 7.4). The actual impacts due to oxygen and rain attenuation factors are quantified in Section 7.4 in terms of link budget analysis. 7.4 Link Budget Analysis Based on propagation characteristics, path loss models, and mmwave-specific auxiliary attenuation factors in terms of oxygen absorbance and rain rates, wireless system designers should be able to define the achievable performance. This is why link budget calculation is essential in mmwave systems engineering. In this section, two different types of link budget estimation procedures are presented. In Section 7.4., the Shannon capacity equation is used for estimating achievable data rates with the computation of signal-to-noise ratio (SNR). However, the Shannon capacity is only AU: The two sentences beginning Based on this rain rate information have been changed. Please check the meaning. AU: The sentence beginning Based on propagation characteristics has been changed. Please check the meaning. K6645_C7.indd 47

12 47 Opportunities in 5G Networks Table 7.4 Rain Rates and Their Corresponding Attenuation Factors at 8, 38, and 6 GHz mmwave Frequency Bands Depending on Rain Climatic Zones (for ITU Regions D and Q) Carrier Frequency (GHz) ITU Region Segment 99% Availability (db/km) 99.9% Availability (db/km) 8 D.5.4 Q 4 38 D.6. Q D. 3.5 Q 9 5 achievable when optimum modulation and coding schemes are assumed. Therefore, Section 7.4. presents a more practical approach with existing standards. In the 8 and 38 GHz mmwave frequency bands, there are no standards; practical analysis is not available due to the lack of a standard modulation and coding scheme (MCS) definition. In 6 GHz mmwave channels, IEEE 8.ad is a representative standard. Thus, practical link budget estimation is available with 6 GHz mmwave IEEE 8.ad MCS definition Shannon Capacity Based Calculation with Signal-to-Noise Ratio Computation Based on the well-known Shannon capacity equation, achievable data rates between transmitter and receiver can be calculated as ( ) + Pm RX watt d C( d) = BW log nm watt AU: Please insert a unit of measure for.6 in and.6 at 6 GHz. where: C(d) is the achievable rate when d is the distance between the transmitter and the receiver BW is the channel bandwidth ( MHz at 8 GHz, 5 MHz at 38 GHz, and.6 at 6 GHz) n mwatt is the background noise, calculated as in Section 7.. Pm RX watt ( d) is the receive signal strength at the receiver when d is the distance between the transmitter and the receiver P d m RX watt ( ) can be calculated as K6645_C7.indd 47

13 Millimeter-Wave (mmwave) Radio Propagation Characteristics 473 ( ) = RX ( ( )/) Pm RX PdBm d watt d RX and PdBm ( d) is the receive signal strength at the receiver (when the distance between the transmitter and the receiver is d) in decibels, and this can be calculated as RX P d EIRP PL d O d R d dbm ( ) = ( ) ( ) ( ) where PL(d), O(d), and R(d) stand for path loss (refer to Section 7.3.), oxygen attenuation (refer to Section 7.3..), and rain attenuation (refer to Section 7.3..), respectively, depending on the distance d. In addition, equivalent isotropically radiated power (EIRP) can be calculated as TX TX EIRP = PdBm + GdBi where P TX dbm and G TX dbi are the transmit power and transmit antenna gain, respectively. In this study, fundamental upper bounds will be observed, that is, EIRP limits are considered. In outdoor point-to-point links, the EIRP limit is defined as 8 dbm at 6 GHz mmwave bands, whereas the EIRP limit is 43 dbm at 6 GHz mmwave bands in other applications [3,4]. The achievable rate computation results are plotted as shown in Figures 7.6 and 7.7 at 6 GHz mmwave bands for 5 and m, respectively. Even though this section presents the achievable rates only in 6 GHz bands, the link budget calculation with the Shannon capacity equation can be performed for 8 GHz and 38 GHz mmwave bands in the same way. AU: The sentence beginning The achievable has been changed. Please check the meaning. Achievable rate (Gbps) Distance (m) No rain attenuation ITU Region D (99.% availability) ITU Region D (99.9% availability) ITU Region Q (99.% availability) ITU Region Q (99.9% availability) 5 Figure 7.6 Achievable rates in LOS outdoor point-to-point 6 GHz links. K6645_C7.indd 473

14 474 Opportunities in 5G Networks Achievable rate (Gbps) No rain attenuation ITU Region D (99.% availability) ITU Region D (99.9% availability) ITU Region Q (99.% availability) ITU Region Q (99.9% availability) Distance (m) Figure 7.7 Achievable rates in LOS general 6 GHz links IEEE 8.ad Baseband-Based Calculation in 6 GHz mmwave Channels The achievable rates in the previous section, that is, by Shannon capacity equation based link budget calculation, can only be obtained when optimum modulation formats and coding schemes are available. Therefore, the Shannon capacity based approach is a theoretical upper bound. In this section, practical achievable data rates are calculated based on 6 GHz mmwave IEEE 8.ad baseband parameters (i.e., MCS set). For the IEEE 8.ad MCS-based link budget calculation, the following three steps are required: Step : Computing received signal strength. Step : Finding supportable MCS levels by comparing the receiver sensitivity values in table -3 in the IEEE 8.ad specification and the computed received signal strength in Step. Step 3: Retrieving achievable rates based on the supportable MCS levels. For Step, the received signal strength depending on the distance between the transmitter and the receiver can be obtained by a calculation procedure equivalent to the procedure in Section 7.4.: RX P d EIRP PL d O d R d dbm ( ) = ( ) ( ) ( ) AU: A where list has been created following this equation. Please verify. where: EIRP is the equivalent isotropically radiated power PL(d) is the path loss depending on the distance d O(d) is the oxygen attenuation depending on the distance d R(d) is the rain attenuation depending on the distance d K6645_C7.indd 474

15 Millimeter-Wave (mmwave) Radio Propagation Characteristics 475 Table 7.5 Receiver Sensitivity Values and MCS Matching Receiver Sensitivity (dbm) MCS Index (Mbps) Supportable MCS 78 MCS (7.5) MCS 68 MCS (385) MCS 66 MCS (77) MCS 65 MCS3 (96.5) MCS3 64 MCS4 (55) MCS4 63 MCS6 (54) MCS6 6 MCS5 (5.5), MCS7 (95 ) MCS7 6 MCS8 (3) MCS8 59 MCS9 (5.5) MCS9 55 MCS (38) MCS 54 MCS (385) MCS 53 MCS (46) MCS For Step, the calculated received signal strength values in Step should be compared with the receiver sensitivity values in table -3 in the IEEE 8.ad specification. Table 7.5 shows this matching. As presented in Table 7.5, if the received signal strength is about 7 dbm, for example, MCS is not supportable, because the value is less than the receiver sensitivity value in MCS (i.e., 7 < 68 dbm). Therefore, only MCS is supportable. When the received signal strength is 6.5 dbm, there are two choices: MCS5 and MCS7. In this case, the MCS that can support the higher data rate, MCS7, will be selected. Note that Table 7.5 is organized with single-carrier MCS values, which are mandatory features in IEEE 8.ad. This standard also defines orthogonal frequency multiple duplexing (OFDM)-based MCS and low-power MCS (from MCS3 to MCS4); however, these are optional features and are not included in Table 7.5. Then, final link budget calculation results are plotted as shown in Figures 7.8 and 7.9. Similarly to the plotting in Section 7.4., the MCS-based link budget calculation can be performed only at 6 GHz bands, because there are no standards yet at 8 and 38 GHz mmwave bands. In Step 3, supportable data rates based on the selected MCS values can be directly obtained from Table 7.5. AU: The sentence beginning Table 7.5 has been changed. Please check the meaning. K6645_C7.indd 475

16 476 Opportunities in 5G Networks Achievable rate (Gbps) No rain attenuation ITU Region D (99.% availability) ITU Region D (99.9% availability) ITU Region Q (99.% availability) ITU Region Q (99.9% availability) Distance (m) Figure 7.8 MCS-based rates in LOS outdoor point-to-point 6 GHz links. Achievable rate (Gbps) No rain attenuation ITU Region D (99.% availability) ITU Region D (99.9% availability) ITU Region Q (99.% availability) ITU Region Q (99.9% availability) Distance (m) Figure 7.9 MCS-based rates in LOS general 6 GHz links. Under the additional consideration of the optional OFDM-based MCS and low-power MCS features in addition to the mandatory single-carrier MCS values (from MCS to MCS), Table 7.5 can be revised as shown in Table 7.6, with a similar approach in Step ; corresponding data rates can be derived by Step 3 and plotted as shown in Figures 7. and Concluding Remarks This chapter summarizes the major characteristics of 8, 38, and 6 GHz mmwave wireless radio wave propagation. The directionality of the propagation is numerically formulated and simulated based on standard ITU models. In addition, path loss K6645_C7.indd 476

17 Millimeter-Wave (mmwave) Radio Propagation Characteristics 477 Table 7.6 Receiver Sensitivity Values and MCS Matching (Including Optional OFDM-Based MCS) Receiver Sensitivity (dbm) MCS Index (Mbps) Supportable MCS 78 MCS (7.5) MCS 68 MCS (385) MCS 66 MCS (77, MCS3 (693) MCS 65 MCS3 (96.5) MCS3 64 MCS4 (55), MCS4 (866.5), MCS5 (66) MCS4 63 MCS6 (54), MCS5 (386) MCS6 6 MCS5 (5.5), MCS7 (95), MCS6 (73.5) MCS7 6 MCS8 (3) MCS8 6 MCS7 (79), MCS6 (834) 59 MCS9 (5.5) MCS9 58 MCS8 (77) MCS8 57 MCS7 (), MCS8 (5), MCS9 (668), MCS3 (4), MCS3 (53) 56 MCS9 (3465) MCS9 55 MCS (38) 54 MCS (385), MCS (458) MCS 53 MCS (46), MCS (454.5) MCS 5 MCS (597.5) MCS 49 MCS3 (637) MCS3 47 MCS4 ( ) MCS4 models are presented in LOS, and NLOS situations are provided in the mmwave channels. As well as path loss, mmwave wireless channels also include additional mmwave-specific oxygen and rain attenuation. Based on the mmwave propagation models and parameters provided, a link budget calculation is performed to identify what data rates can be obtained depending on the distance between the transmitter K6645_C7.indd 477

18 478 Opportunities in 5G Networks Achievable rate (Gbps) No rain attenuation ITU Region D (99.% availability) ITU Region D (99.9% availability) ITU Region Q (99.% availability) ITU Region Q (99.9% availability) Distance (m) Figure 7. MCS-based (for both single carrier and OFDM MCS) rates in LOS outdoor point-to-point 6 GHz links. Achievable rate (Gbps) No rain attenuation ITU Region D (99.% availability) ITU Region D (99.9% availability) ITU Region Q (99.% availability) ITU Region Q (99.9% availability) Distance (m) Figure 7. MCS-based (for both single carrier and OFDM MCS) rates in LOS general 6 GHz links. and the receiver of mmwave wireless propagation links. The link budget calculation is performed in two ways: the Shannon capacity equation and IEEE 8.ad MCS-based practical data rate estimation. AU: Au: Please provide the in-text citations for Refs. 5. References. J. Kim and A. F. Molisch, Fast millimeter-wave beam training with receive beamforming, IEEE/KICS Journal of Communications and Networks 6(5): 5 5, 4. K6645_C7.indd 478

19 Millimeter-Wave (mmwave) Radio Propagation Characteristics 479. ITU Recommendation, Reference radiation patterns of omnidirectional, sectoral and other antennas for the fixed and mobile services for use in sharing studies in the frequency range from 4 MHz to about 7 GHz, ITU-R F.336-4, A. F. Molisch, Wireless Communications, nd Edn, New York: Wiley,. 4. ITU Recommendation, A general purpose wide-range terrestrial propagation model in the frequency range 3 MHz to 5 GHz, ITU-R P.-, ITU Recommendation, Propagation data and prediction methods for the planning of short-range outdoor radiocommunication systems and radio local area networks in the frequency range 3 MHz to GHz, ITU-R P.4-7, J. Kim and A. F. Molisch, Quality-aware millimeter-wave device-to-device multi-hop routing for 5G cellular networks, in Proceedings of IEEE International Conference on Communications (ICC), Sydney, IEEE, Y. Azar, G. N. Wong, K. Wang, R. Mayzus, J. K. Schulz, H. Zhao, F. Gutierrez, Jr., D. D. Hwang, and T. S. Rappaport, 8 GHz propagation measurements for outdoor cellular communications using steerable beam antennas in New York City, in Proceedings of IEEE International Conference on Communications (ICC), Budapest, IEEE, T. S. Rappaport, F. Gutierrez, Jr., E. Ben-Dor, J. N. Murdock, Y. Qiao, and J. I. Tamir, Broadband millimeter wave propagation measurements and models using adaptive beam antennas for outdoor urban cellular communications, IEEE Transactions on Antenna and Propagation 6(4): , A. Maltsev, E. Perahia, R. Maslennikov, A. Lomayev, A. Khoryaev, and A. Sevastyanov, Path loss model development for TGad channel models, IEEE 8.-9/553r, 9.. ITU Recommendation, Attenuation by atmospheric gases, ITU-R P.676-, 3.. ITU Recommendation, Characteristics of precipitation for propagation modelling, ITU-R PN.837-, Federal Communications Commission (FCC), Office of Engineering and Technology, Bulletin Number 7, FCC, Operation of unlicensed devices in the GHz band, FCC 3-, J. Kim, Y. Tian, S. Mangold, and A. F. Molisch, Joint scalable coding and routing for 6 GHz real-time live HD video streaming applications, IEEE Transactions on Broadcasting 59(3): 5 5, J. Kim, Y. Tian, A. F. Molisch, and S. Mangold, Joint optimization of HD video coding rates and unicast flow control for IEEE 8.ad relaying, in Proceedings of IEEE International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), Toronto, IEEE,. 6. J. Kim and A. F. Molisch, Enabling gigabit services for IEEE 8.ad-capable highspeed train networks, in Proceedings of IEEE MTT-S Radio and Wireless Symposium (RWS), Austin, TX, IEEE, J. Kim, Y. Tian, S. Mangold, and A. F. Molisch, Quality-aware coding and relaying for 6 GHz real-time wireless video broadcasting, in Proceedings of IEEE International Conference on Communications (ICC), Budapest, IEEE, J. Kim, A. Mohaisen, and J-K. Kim, Fast and low-power link setup for IEEE 8.5.3c multi-gigabit/s wireless sensor networks, IEEE Communications Letters 8(3): , J. Kim, Elements of next-generation wireless video systems: Millimeter-wave and device-to-device algorithms, PhD Dissertation, University of Southern California, Los Angeles, CA, 4. AU: Please provide page numbers for ref. 6. AU: Please provide page numbers for ref. 7. AU: Please provide page numbers for ref. 5. AU: Please provide page numbers for ref. 6. AU: Please provide page numbers for ref. 7. K6645_C7.indd 479

20 48 Opportunities in 5G Networks AU: Please provide page numbers for ref... J. Kim and E-S. Ryu, Quality of video streaming in 38 GHz millimetre-wave heterogeneous cellular networks, IET Electronics Letters 5(): 56 58, 4.. J. Kim and S-N. Hong, Dynamic two-stage beam training for energy-efficient millimeter-wave 5G cellular systems, Telecommunication Systems 59():, 5.. J. Kim, L. Xian, A. Maltsev, R. Arefi, and A. S. Sadri, Study of coexistence between 5G small-cell systems and systems of the fixed service at 39 GHz band, in Proceedings of IEEE MTT-S International Microwave Symposium (IMS), Phoenix, AZ, IEEE, 5. K6645_C7.indd 48