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Special Topics in Optical Engineering II (15/1) 유병민
Paper review
Special Topics in Optical Engineering II (15/1) 유병민
Content
1. Background
2. Introduction
3. Physical layer performance
① Wireless PANs
② Wireless LANs
③ Wireless MANs/WANs
4. External modulated link modeling (OFDM over fiber)
5. Higher-layer protocol issue
6. Complete sensor network
7. Broadband 60GHz RoF systems
8. Conclusion
Special Topics in Optical Engineering II (15/1) 유병민
Background (Computer Network)
• PAN (Personal Area Network): Area about one person (<10m)
Wireline: USB, FireWire
Wireless: Bluetooth, UWB, ZigBee
• LAN (Local Area Network): Area about building
Wireline: Ethernet (TCP/IP)
Wireless: wireless LAN (IEEE 802.11)
• MAN (Metropolitan Area Network): area about a few city
ATM, FDDI, SMDS
• WAN (Wide Area Network): Network between countries/continents
Special Topics in Optical Engineering II (15/1) 유병민
Background (802.11 standard)
• 802.11: Standard specification of Wireless Local Area Network (LAN)
to compensate wireline LAN(Ethernet)
801.11a: 5 GHz band, 54 Mb/s maximum (OFDM)
801.11b: 2.4 GHz band, 11 Mb/s maximum
801.11g: same data rate with 801.11a, 2.4 GHz band
• 802.11n (2009.10): to improve 802.11a, 802.11g (600 Mb/s)
4 MIMO stream
Physical layer, MAC layer, Frame aggregation
Special Topics in Optical Engineering II (15/1) 유병민
Background (RoF)
- RoF: radio signals are carried over fiber-optic cable
- A single antenna can receive any and all signals
Advantage of RoF
Low attenuation
Low complexity
Lower cost
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
• Ultrawideband (UWB): interest in PANs (1 Gb/s)
Coexistence with other wireless service
Low radiate power
Low probability of interception
• Experiment types
Impulse-radio (IR): High definition audio, video content in FTTH network.
A. IR-UWB: External modulator, SSMF is used
B. IR-UWB: VCSEL (upconversion (8.5 GHz 62, 66 GHz))
C. MB-OFDM UWB: MMF, VCSEL(850 nm operation)
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
A. IR-UWB over fiber
1.25 Gb/s Gated optical pulse
Optical pulse train Monopulse shaped
6.6 GHz
IR-UWB transmission in FTTH demonstration setup
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
A. IR-UWB over fiber
• −10 dB bandwidth: 3.2 GHz (5~8.2 GHz)
• Stringent equivalent isotropic radiated power (EIRP) limits
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
A. IR-UWB over fiber 20 GHz MZM
IR-UWB transmission in FTTH demonstration setup
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
A. IR-UWB over fiber
• 10-9 BER: to 50 km of SSMF (RoF of 1.25 Gb/s IR-UWB)
Special Topics in Optical Engineering II (15/1) 유병민
Monocycle spectrum at baseband
after fiber transmission
8.5 GHz upconverted spectrum
after fiber transmission
RoF Link Experiment: PANs
B. IR-UWB over SSMF and upconversion
• 3dB bandwidth: 1.7 GHz (800 MHz – 2.5 GHz)
• LPF (5.2 GHz): reduce spurious power
• Upconversion: USB (9.3 – 11 GHz with 8.5 GHz LO)
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
C. MB-UWB over fiber
• ECMA 368 standard based: Ultra wide band PHY and MAC standard
• VCSEL: modulation
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: PANs
C. MB-OFDM UWB over fiber
MB-OFDM UWB EVM results for different MMF lengths
• ECMA-368 standard requirements: 18.84% EVM
Special Topics in Optical Engineering II (15/1) 유병민
Typical implementation of RoF system
RoF Link Experiment: LANs
A. 802.11a and upconversion
• IR−UWB signal (PAN-a) is used
• 5.1 GHz band 802.11a signal, 2m of SSMF
• fLO = 2 GHz, fRF = 1.1 GHz
• VCSEL: modulation (E/O conversion)
• Target: Minimum EVM
EVM depending on Ibias, PLO and PRF
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: LANs
B. MMF links for 802.11g
• Low-cost MMF RoF for 802.11g standard
(2.4 GHz, 64 QAM OFDM, 54 Mb/s over 100 m)
• Low-cost approach: IM-DD (intensity modulation – direct detection) technique
Radio over MMF using IM-DD for WLANs
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: LANs
B. MMF links for 802.11g
• EVM requirement (IEEE 802.11g): 5.4 %
• 50 nm MMF: 2.5 % EVM up to 600 m fiber length
• RF power ⬆ : distortion, EVM ⬆
EVM as function of RF power level
for 2.4 GHz & 300 m RoF link
EVM as function of fiber length
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: MANs and 3G
• High data rate, many users: reduction cell size
802.16 WiMAX, 3G mobile communications,
(with picocellular system design)
• RoF: Proposed for such systems
• MMF: moderate distance transmission (~hundreds of meters)
• Experiment
RoF experiments for WiMAX and 3G systems
Low-cost, 850 nm VCSEL, MMF
Special Topics in Optical Engineering II (15/1) 유병민
Measurement setup for WiMAX over MMF
RoF Link Experiment: MANs and 3G
A. WiMAX over fiber
EVM (left) conformance (right) of WiMAX measurement
• 3.5 MHz 64-QAM 3/4 WiMAX signal with 3.5 GHz band (fiber length < 400 m)
• Standard spectral mask(red line), measurement result (yellow line)
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: MANs and 3G
B. 3G and adjacent channel leakage
Experimental setup of multi system transport over a VCSEL multimode fiber link
Special Topics in Optical Engineering II (15/1) 유병민
RoF Link Experiment: MANs and 3G
• EVM requirement: 12.5 %
• Adjacent channel leakage ratio(ACLR)
50 dB at 10 MHz offset, 45 dB at 5 MHZ
Noise floor is dominant until 0 dBm VCSEL input power
EVM (left) results of a VCSEL multimode fiber link ACLR measurement
B. 3G and adjacent channel leakage
Special Topics in Optical Engineering II (15/1) 유병민
External modulated link modeling (OFDM over fiber)
• Key aspect of RoF system: modulation format, OFDM
• Behavior of OFDM signal in RoF for WLAN
• Simulation model: 802.11a WLAN signals
MZM RoF system model
Special Topics in Optical Engineering II (15/1) 유병민
External modulated link modeling (OFDM over fiber)
MSE depending on MZM modulation index
• Modulation index (𝛤MZM) < 0.45: MSE < 10-3
• 𝛤MZM > 0.45: MSE Rapidly increased
• SNR: also rapidly increased from 0.45 𝛤MZM
Signal amplitude and output intensity
Special Topics in Optical Engineering II (15/1) 유병민
External modulated link modeling (OFDM over fiber)
BER dependence on fiber length Receiver performance with FEC
• BER with/without error correction, fiber length
• Forward error correction (FEC): constraint length of 7
• −16 to −14 dBm input power: 10-3 to 10-4 BER (1 km, without FEC)
• Performance gain: 4 dBm (using FEC)
• 2~3 dBm loss in 1 km length of SSMF
4 dBm
Special Topics in Optical Engineering II (15/1) 유병민
High Layer Protocol Issue
• MAC, TCP, UDP protocol: performance degradation
system performance depending on High layer protocol
Variation of throughput using basic access
Variation of throughput using RTS/CTS
(Request to Send / Clear to Send)
• Throughput < data rate: control overhead (1 Mb/s control bit)
• RTS/CTS: More control data reduce throughput
• Steadily reduce as fiber length increase: waiting times, lost
• 5~7% FER (Frame error rate): 5.5 Mb/s
A. Impact of the 802.11 MAC
Special Topics in Optical Engineering II (15/1) 유병민
High Layer Protocol Issue
B. Impact on TCP/UDP
Signal amplitude and output intensity
• MAC: provide retransmission retransmission at TCP layer (x)
• UDP: alternative transport protocol to TCP (confirm step isn’t it)
Special Topics in Optical Engineering II (15/1) 유병민
Sensor Network
• Wireless indoor communication system: sensor area network
• Low data rate (20~200 kb/s) 802.15.4, extremely low power consumption
• 250 kb/s, 4 bit symbol
Maximum fiber length: 86.4 km(ask time out: 54 symbol)
• 84 km fiber length: about 0 time-out probability
Time-out uncertainty due to clock jitter
Special Topics in Optical Engineering II (15/1) 유병민
Broadband 60 GHz RoF System
• 12.5 Gb/s data with 60
GHz band
• DC bias: Vπ
For DSB-SC signal
• NRZ-OOK data
modulation
• Detection with 70 GHz PD
Schematic of 60 GHz RoF setup
Special Topics in Optical Engineering II (15/1) 유병민
Broadband 60 GHz RoF System
• Error-free broadband wireless communication up to 12.5 Gb/s
• Error-free: at -46 dBm received power, 10.3125 Gb/s at 40 m
BER after 2.5 m data transmission BER levels for multi Gbit data transmission
after 20 and 40 m data transmission
Special Topics in Optical Engineering II (15/1) 유병민
Broadband 60 GHz RoF System
• Extending wireless path length to the ~km (outdoor experiment)
• 60GHz band attenuation in free-space: 15.5 dB/km
• 10-9 BER at 12.5 Gb/s: < 1100 m (99% link availability)
< 800 m (99.99% link availability)
< 500 m (99.999% link availability)
Maximum wireless path lengths
Special Topics in Optical Engineering II (15/1) 유병민
Conclusion
1. Physical layer performance
① Wireless PANs
② Wireless LANs
③ Wireless MANs/WANs
2. External modulated link modeling
3. Higher-layer protocol issue
4. Sensor network
5. Broadband 60GHz RoF systems
Special Topics in Optical Engineering II (15/1) 유병민
Paper review
High-Speed Circuits and Systems Lab, Yonsei Univ.
Byung-Min Yu
Special Topics in Optical Engineering II (15/1) 유병민
Reference