SCIENCE CHINA Information Sciences, Volume 63 , Issue 8 : 180301(2020) https://doi.org/10.1007/s11432-019-2832-1

## In-building coverage of millimeter-wave wireless networks from channel measurement and modeling perspectives

• AcceptedMar 16, 2020
• PublishedJul 15, 2020
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### Abstract

To progress cost-effective deployment of millimeter-wave (mmWave) wireless networks for indoor users, the prediction of indoor-to-indoor (I2I) and outdoor-to-indoor (O2I) coverage based on field measurement studies is of great interest to the future generation mobile communication system. First, measurements in I2I and O2I scenarios, which have advantages in terms of achieving a fair comparison of channel characteristics across different mmWave bands and bandwidths, are performed. Next, the developed dual-slope path loss model with a break-point distance is found to well fit omnidirectional and directional measured I2I data, especially at 39.5 GHz, revealing that the transition from lit or shadow regions to totally blocked regions is abrupt. Combined with space-time propagation characteristics, the indoor blockage effect on path loss and angular spread is investigated, therein being essential for the design of beam-steering and tracking algorithms. Double-directional measurement results show that most dominant paths arrive along the line-of-sight path, and only a few in-building reflections can be detected in higher frequency bands. Based on the joint analysis of channel measurement and modeling results, several mmWave network design and in-building coverage enhancement insights are presented.

### Acknowledgment

This work was supported in part by National Key RD Program of China (Grant No. 2018YFB180- 1101), National Natural Science Foundation of China (Grant Nos. 61960206006, 61671145), and Key RD Program of Jiangsu Province of China (Grant No. BE2018121).

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• Figure 1

(Color online) Illustration of a potential mmWave indoor and outdoor cooperative cellular network for in-building coverage, including a highly directional beam in outdoor-to-indoor channels and a wide beam in indoor-to-indoor channels.

• Figure 2

(Color online) General plan view of O2I scenario. The TX is mounted on the rooftop of Building A3, and indoor RXs are located on the third floor of Building A5, which are all in the illuminated area.

• Figure 3

(Color online) Layout of indoor TX and RX locations, where the red dots and green triangles represent the TX and RX locations for the indoor measurements, respectively.

• Figure 4

(Color online) Comparison of the measured directional PDPs for I-RX 5 at 27.5 GHz with bandwidths of 200 (black line) and 600 MHz (gray line).

• Figure 5

(Color online) Measured directional and omnidirectional path loss for all I-RX locations, as well as their fitting results. The gray crosses represent the top 80 directional path loss values over all 720 antenna pointing angle combinations (10 AoD $\times$ 36 AoA $\times$ 2 EoA), the blue diamonds represent the path with the strongest received power, i.e., the lowest directional path loss, and the black squares represent omnidirectional path loss. (a) and (b) represent 27.5 GHz with RF bandwidths of 200 and 600 MHz, respectively, as well as (c) and (d) in 39.5 GHz band.

• Figure 6

(Color online) Double-directional APS at 27.5 GHz. (a) and (b) for RX 30 with bandwidths of 200 and 600 MHz, respectively, as well as (c) and (d) for RX 5 and (e) and (f) for RX 28.

• Figure 7

(Color online) Excess losses relative to free space path losses for all O-RX locations. (a) and (b) at 27.5 GHz with bandwidths of 200 and 600 MHz, respectively, as well as (c) and (d) at 39.5 GHz.

• Figure 8

(Color online) Double-directional path loss distributions in the AoA-AoD plane with sounding bandwidth of 200 MHz. (a) 27.5 GHz, O-RX 1; (b) 27.5 GHz, O-RX 2; (c) 39.5 GHz, O-RX 1; (d) 39.5 GHz, O-RX 2.

• Figure 9

(Color online) Power ratio of the combined directional beam to the total varying with the number of strongest paths in combination.

• Table 1

Table 1Antenna specifications for mmWave O2I and indoor channel measurements

Parameter Value
Carrier frequency 27.5 GHz 39.5 GHz
TX/RX ant. HPBW$^{\rm~a)}$ ang9.5Az.)/ang9.5El.) ang9.5Az.)/ang9.5El.)
TX/RX ant. gain 25.6 dB 27.7 dB
Pol. combination V-V
TX ant. azimuth angle  O2I: ang60 with increment of ang10; Indoor: ang90 with increment of ang10
TX ant. elevation angle O2I: $-$ang10; Indoor/penetration: ang0
RX ant. azimuth angle  O2I/Indoor: ang360 with increment of ang10
RX ant. elevation angle$^{\rm~b)}$  O2I: $-$ang10 ang0 ang10; Indoor: ang0 ang10
• Table 2

Table 2Path loss model parameters in indoor NLOS setting at 27.5 and 39.5 GHz with $d_{\text{BP}}=16.7$ m for part 1 and $d_{\text{BP}}=44.7$ m for part 2

 Frequency $\text{(GHz)}$
 $B$ $\text{(MHz)}$
ScenarioThe CI path loss modelDual-slope path loss model
 Case 1 Best direction
 Case 1 Omnidirection
 Case 2 Best direction
 Case 2 Omnidirection
 Case 2 Best direction
 Case 2 Omnidirection
$\alpha_0$ $\sigma_0$ $\alpha_0$ $\sigma_0$ $\alpha_0$ $\sigma_0$ $\alpha_0$ $\sigma_0$ $\alpha_1$ $\beta_1$ $\sigma_1$ $\alpha_1$ $\beta_1$ $\sigma_1$
27.5200Part 1 3.54.22.92.54.84.34.23.42.4 19.7 3.6 2.4 17.3 1.6
Part 2 8.5 22.1 1.3 9.6 20.3 1.6
600Part 1 3.53.92.92.34.83.94.23.32.5 19.7 3.3 2.2 17.7 1.4
Part 2 9.8 20.4 0.3 10.0 19.9 1.0
39.5200 Part 1 3.8 4.6 3.2 2.8 5.2 4.4 4.6 2.9 2.9 21.7 3.6 2.5 21.7 1.9
600 Part 1 3.8 5.5 3.1 3.0 5.2 4.7 4.6 3.2 3.0 22.3 4.1 2.0 22.4 1.7
• Table 3

Table 3Statistics of composite delay and angular spreads in indoor NLoS setting at 27.5 and 39.5 GHz

Frequency (GHz)27.539.5
$B$ (MHz)200600200600
ScenarioCase 1 Case 2 Case 1 Case 2 Case 1 Case 2 Case 1 Case 2
 Composite DS $(\log_{10}({\rm~s}))$
$\mu$ $-$7.2 $-$7.4 $-$7.1 $-$7.2 $-$7.3 $-$7.5 $-$7.2 $-$7.4
$\sigma$ 0.11 0.12 0.06 0.04 0.06 0.09 0.05 0.08
 Composite ASA $(\log_{10}(^\circ))$
$\mu$ 1.6 1.7 1.6 1.7 1.5 1.6 1.6 1.7
$\sigma$ 0.13 0.03 0.13 0.04 0.13 0.08 0.13 0.06
 Composite ASD $(\log_{10}(^\circ))$
$\mu$ 1.3 1.1 1.3 1.1 1.3 1.1 1.3 1.1
$\sigma$ 0.09 0.16 0.09 0.16 0.09 0.09 0.09 0.08
• Table 4

Table 4Statistics of O2I omnidirectional channel parameters for O-RXs inside the office

Frequency (GHz)27.539.528[33] 28[42]
Bandwidth (MHz)200 600 200 600 400 0.02
 BEL (dB)
Maximum 33.3 32.1 38.6 38.9
Minimum 16.1 15.1 20.91 19.3
Average 27.5 25.9 32.3 32.8 22.7 17.1
Standard 5.3 4.6 4.9 4.9 1.2 2.8
$\rho_{{\rm~BEL},d_{\rm~in}}$ 0.54 0.49 0.33 0.28
 ASA $(^\circ)$
Average 83.9 79.1 78.8 63.5 37.5
Standard 52.6 57.5 51.2 58.8
 ASD $(^\circ)$
Average 7.6 7.3 7.2 6.8
Standard 2.0 2.1 2.2 3.0

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