doc.: ieee 802.15-15-0875-00-007a project: ieee p802.15 ......vol.52, no.5, pp.44-51 (2014). ... 0...

Volker Jungnickel Slide 1

doc.: IEEE 802.15-15-0875-00-007a

Submission

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: Discussion on Channel Model for B4 Date Submitted: November 9, 2015 Source: V. Jungnickel, D. Schulz, J. Hilt, C. Alexakis, M. Schlosser, A. Paraskevopoulos, L. Grobe, R. Freund Company: Fraunhofer HHI Address: Einsteinufer 37, 10587 Berlin, Germany, Voice: +49 30 31002 768 mail: [email protected] Re: Agenda for Monday Nov. 9, PM2 session

Abstract: Fudan University proposed that an additional channel model should be developed for scenario B4. Fraunhofer provides insights into recent work on that issue as a basis for discussion.

Purpose: Discussion Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

Photonic Networks and Systems

Volker Jungnickel et al.: Discussion on Channel Model for B4

Low-cost short-range backhaul

Initial results

Long-term outdoor measurements

Model for optimized link design

Results with optimized link design

Conclusions

Outline

2



Low-cost short-range backhaul

3

Increasing amounts of data over mobile networks

Small cells are the main capacity scaling factor

V. Jungnickel et al., ”The role of small cells, coordinated multipoint, and massive MIMO in 5G,” IEEE Communications Magazine, Special Issue on 5G Wireless Communication Systems: Prospects and Challenges, vol.52, no.5, pp.44-51 (2014).

5G: Up to 50/10 indoor/outdoor small cells per sector Urban areas (Germany): Typical inter-site distance is 500 m Small-cell backhaul distance is 50-250 m High line-of-sight probability

New idea: Use LED-based optical wireless link as low-cost backhaul solution for small radio cells

V. Jungnickel, D. Schulz, N. Perlot, K.-D. Langer, W. Störmer, „Optical Wireless as a Low-Cost Small-Cell Backhaul Solution,” 8. ITG Fachtagung Photonische Netze und Systeme, Berlin, 1.-2. April 2014



Laser vs. LED

4

Laser: Gaussian beam profile Sensitive against misalignment Needs tracking

LED: Flat-top beam profile Easy alignment No more tracking is needed Very robust link Lamp posts, etc.



Initial results

5

20 40 60 80 100100150200250300350400450500

Dat

a ra

te [M

bit/s

]

Distance [m]

20 18 16 14 12 10 8 6Electrical SNR [dB]

3”, f=10/8,5 cm lens at Tx/Rx

Single-color infrared LED

7x7 mm² emitting area

14 mm effective PD diameter

7x7 m² beam area at 100 m

More focused beam

Better usage of optical bandwidth



Long-term outdoor experiment

6

Evaluate the impact of fog and sunlight

Measured both, visibility range and data rate

5-month trial during winter term Nov. 2014 – April 2015

Visibility range OW Link



Cumulative long-term statistics

7

Cumulative statistics of visibility and data rate for 5 months

Visibility was never below 180 m High availability for short distances

Rate adaptation: Data rate was for On average more than 100 Mbit/s 99% more than 39 Mbit/s 99,9% more than 22 Mbit/s More than 6 Mbit/s at any time

No outage at all Thanks to rate-adaptive system concept

0 25 50 75 100 1250,0

0,2

0,4

0,6

0,8

1,0

Prob

abili

ty (D

ata

rate

< A

bsci

ssa)

Data rate [Mbps]

0 250 500 750 1000 1250 1500 1750 20000,000

0,005

0,010

0,015

0,020

0,025

0,030

Prob

abili

ty (V

isib

ility

< A

bsci

ssa)

Visibility [m]



Model for optimized link design

8

- LED power, active area, beam width - Focal length and diameter of lens

- Visibility range - Shot noise due to sunlight

- Received power - PD area, sensitivity - Focal length and diameter of lens - Rx bandwith

Model computes finally the electrical SNRel at the receiver Use modified Shannon‘s formula C = B*log2(1+SNRel/Γ) Determine empirical parameter Γ from system measurements



New 1 Gb/s baseband chip

9

0 250 500 750 1000 1250 15000

100

200

300

400

500

600

500Mb/s baseband chip 1Gb/s baseband chipN

et D

ata

rate

[Mbi

t/s]

Frame Size [Byte]

0 250 500 750 1000 1250 15000

10

20

30

40

50

Cut

-thro

ugh

Late

ncy

[ms]

Frame Size [Byte]

500 Mb/s baseband chip 1 Gb/s baseband chip

2.3x

Standard RFC 2544 test electrical back-to-back measurements Electrical gross data rate ~950 Mb/s Optical gross data rate ~850 Mb/s

Throughput results Is smaller for smaller frame sizes Max. reached for frame size ≥ 512 byte 230% more net throughput

Latency results (10±1) ms for 500 Mb/s chip for frame

size ≥ 512 byte < 2 ms for 1 Gb/s chip, independent of

the frame size



Results with optimized backhaul link

10

4” f=10 cm lenses at Tx and Rx, single-color IR LED 1x1 m² at 100 m higher SNR New baseband chip Higher throughput, lower latency

0 50 100 150 200 2500

200

400

600

800

1000

Gro

ss D

ata

Rat

e [M

b/s]

Distance [m]

optimized LED backhaul link original LED backkhaul link



Summary

11

Initial work using LED-based optical wireless link for the backhaul of small radio cells (WiFi, LTE).

Long-term outdoor trial indicates the impact of fog and sunlight.

Mathematical model of the link was developed to figure out optimized link parameters, goal was 1 Gbps over 100 m within available analog bandwidth (180 MHz).

Optimized link with new baseband chip (using 100 MHz bandwidth only) achieved around 500 Mbps over 100 m.

Potential towards 10G lies in replacing LED with lasers (high bandwidth).

WDM is regarded critical as it increases receiver complexity.



Impact of visibility

12

Attenuation due to fog is main limiting factor Visibility is essential parameter Use well-known Kim‘s formula: 17 dB loss if visibility is equal to distance

𝛾 𝜆 = 3.91

𝑉𝜆550

−𝑞 𝑘𝑚−1

𝐺𝐴𝐴𝐴[𝑑𝑑] = 10log (𝑒−𝛾 𝜆 𝐿)

1.6 501.3 6 50

0.16 0.34 1 60.5 0.5 1

0 0.5

V kmkm V km

q V km V kmV km V km

V km

> < <= + < < − < <

<

I. I. Kim, B. McArthur , E. Korevaar, "Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications".

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 220

2

4

6

8

10

12

14

16

18

Visibility [km]

Atm

osph

eric

Los

s in

100

m [d

B]



Impact of fog

13

Reduced visibility leads to higher atmospheric losses

Fixed-rate FSO link Total outage Where link margin is not enough

Rate adaptive OW link Reduced rate No more outage is observed Enhanced link availability

04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:000

500

1000

1500

2000

Visi

bilit

y [m

]

Time

0

25

50

75

100

125900

950

1000

Dat

arat

e [M

bps]

OW Link 100 m

FSO Link 500 m Visibility



Impact of sunlight

14

𝑃𝑏,𝜆 = 𝐿𝜆(𝜆)𝛢𝑟𝛺𝑝𝑟 = 𝐿𝜆(𝜆)𝛢𝑟𝜋sin2(𝐹𝐹𝑉2

)

Max. spectral radiance at 780-830 nm: Lλ = 2 Wm-2sr-1nm-1

Example: Ø 75mm , FOV=9°, Ep(780-830nm)=0,6 A/W, Lλ = 2 Wm-2sr-1nm-1 Pb=8.5 mW Ib=5,1mA

𝐼𝑏 = � 𝐸𝑝 𝜆 𝑃𝜆(𝜆)𝑑𝜆𝜆2

𝜆1



Impact of sunlight

15

Scattered sunlight leads to Shot noise Rx saturation (if strong) Use sun cap

Direct sunlight leads to outage Rare event If both, Tx and sunlight are inside the Rx field-of-view (FOV) Minimize the FOV Use optical band-pass filter

00:00 04:00 08:00 12:00 16:00 20:00 24:0020

40

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Dat

a ra

te [M

bps]

Time

0

250

500

750

1000

1250

1500

1750

2000

2250

Vis

ibilit

y [m

]

OW Link 100 m

Visibility

doc.: ieee 802.15-15-0875-00-007a project: ieee p802.15 ......vol.52, no.5, pp.44-51 (2014). ... 0...

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