error correction coding for passive optical networks · 2019. 3. 1. · poninnovation 2,005 2,010...
TRANSCRIPT
-
Error Correction Coding for Passive Optical Networks
Rainer Strobel
2019-02-27
1 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Overview
1 Introduction
2 Error Correction in PON
3 Improved Receiver Architectures
4 Conclusion and Outlook
2 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Passive Optical Networks
Fiber
ONU
OLT
CPE
Splitter ONU
DPU
CPECopper
PON Characteristics
• Fiber access network, fiber to the home (FTTH), but alsofiber to the building/distirbution point (FTTB, FTTdp)
• Point-to-multipoint (P2MP) link between optical linetermination (OLT) and multiple optical network units (ONU)
• No active components between OLT and ONU
• Typical reach 20 km, typical split factor 32
• Low cost electrical/optical components
3 OWHTC2019 2019-02-27 Intel Connected Home Division
-
PON Innovation
2,005 2,010 2,015 2,020100
101
102
NRZEDB?PAM4?
Year
Agg.rate/G
bit/s PON Standards
Modulation
• NRZ used instandard PONs
• EDB, PAM-4discussed forG.HSP
Multiplexing
• TDMA used instandard PONs
• TWDM usedin more recentPONs
Coding
• RS code used inlegacy PONs
• LDPC introduced inIEEE 802.3ca andconsidered for G.HSP
4 OWHTC2019 2019-02-27 Intel Connected Home Division
-
PON Innovation
2,005 2,010 2,015 2,020100
101
102
TDMA TWDMNRZ
Year
Agg.rate/G
bit/s PON Standards
Modulation
• NRZ used instandard PONs
• EDB, PAM-4discussed forG.HSP
Multiplexing
• TDMA used instandard PONs
• TWDM usedin more recentPONs
Coding
• RS code used inlegacy PONs
• LDPC introduced inIEEE 802.3ca andconsidered for G.HSP
4 OWHTC2019 2019-02-27 Intel Connected Home Division
-
PON Innovation
2,005 2,010 2,015 2,020100
101
102
TDMA TWDM
NRZ
Reed-Solomon LDPC
Year
Agg.rate/G
bit/s PON Standards
Modulation
• NRZ used instandard PONs
• EDB, PAM-4discussed forG.HSP
Multiplexing
• TDMA used instandard PONs
• TWDM usedin more recentPONs
Coding
• RS code used inlegacy PONs
• LDPC introduced inIEEE 802.3ca andconsidered for G.HSP
4 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Overview
1 Introduction
2 Error Correction in PON
3 Improved Receiver Architectures
4 Conclusion and Outlook
5 OWHTC2019 2019-02-27 Intel Connected Home Division
-
ONU Receiver Block Diagram
CDR
PhaseError
LDPCDecoder
Decode
PLL
RXClock
LLRCalculation
APD TIA LA
PMD PMA PCS
PON Physical Layer
PCS: Physical Coding Sublayer (LDPC, scrambling, control channel)
PMA: Physical Medium Attachment (digital signal recovery)
PMD: Physical Medium Dependent (optoelectronic conversion)
LDPC Requirements (25G)
• Output bit error rate < 10−12 at 10−2 receive bit error rate
• Low latency ≈ 10µs for wireless front-haul
6 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Binary Receiver Error Probabilities
21 22 23 24 25
10−11
10−9
10−7
10−5
10−3
10−1
Fiber length/km
Biterrorrate
Raw
Coded
0 0.5 1 1.5 2
Unit interval
0
0.5
1
1.5
2
2.5
3
3.5
Am
plitu
de
×10-5
0 1 2
PDF ×105
0
0.5
1
1.5
2
2.5
3
3.5×10-5
• Optical channel cannot bedescribed by a simple binarysymmetric channel (BSC) oradditive white Gaussiannoise (AWGN) channel
• Definition of codingrequirements with raw BERis not convenient
7 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Receiver Optimization - Binary Receiver
0.8 1 1.2 1.4
·10−5
10−3
10−2
10−1
100
Threshold
Biterrorrate
pe(x = 0)
pe(x = 1)pe
py(y = 0) = py(y = 1)
Min. BER
Max. I(x, y)
0.8 1 1.2 1.4
·10−5
0
0.2
0.4
0.6
0.8
1
Threshold
I(x,y)
Threshold Control
• Minimum input BERpoint can be differentfrom optimal LDPCoperating point
8 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Statistical Properties
Errors per Codeword
150 200
10−6
10−4
10−2
100
Errors per codeword
Probab
ility
25G PON
Poisson
• Distribution of errors percodeword influences LDPCperformance
Burst Errors
1 2 3 4 510−10
10−7
10−4
10−1
Number of consecutive errorsProbab
ility
25G PON
Uncorrelated
• Knowledge of burst errorscan be used for decoding
9 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Binary Error Models
px(1) =12
px(0) =12
py(1) =1−pe(1)+pe(0)
2
px|y(1|1) = 1− pe(1)
px|y(0|0) = 1− pe(0)
px|y(0|1) = pe(0)
px|y(1|0) = pe(1)
py(0) =1−pe(0)+pe(1)
2
Memoryless Channel
x ∈ {0, 1}: transmitted symbol;y ∈ {0, 1}: received symbolpe(0), pe(1): Error probability of1 and 0 transmitted
p(01|11)
px(1)
py(0)
px(1)
py(1)
px(0)
py(1)
px(0)
py(0)p(00|01)
p(11|00)p(00|11)
p(11|11)
Binary Channel with Memory
Transition matrix T and statevector p = [pxy(0, 0),pxy(0, 1), pxy(1, 0), pxy(1, 1)]
T
such that pt+1 = Tpt.
10 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Overview
1 Introduction
2 Error Correction in PON
3 Improved Receiver Architectures
4 Conclusion and Outlook
11 OWHTC2019 2019-02-27 Intel Connected Home Division
-
ONU Receiver Implementation
CDR
PhaseError
PLL
RXClock
LLRCalculation
APD TIA LA
Hard Decision Receiver
• Low cost components
• Low power consumption
• Lower FEC performance
ClockRecovery
PhaseError
ADC
PLL
RXClock
LLRCalculation
APD TIA
Soft Decision Receiver
• Analog-to-digital converterrequired
• Higher FEC performance
Binary Receiver/Soft Input
• Derive soft input for LDPCfrom CDR
• Compromise betweencomplexity and powerconsumption
12 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Receiver Optimization - Soft Information
CDR State Informationt+ 12
time
CDRstate s[t]
tt− 2
y[t+1
2]
RXSignal
RXClock
t− 12t− 1t− 3
y[t]y[t−1
2]y[t−1]y[t−
3
2]y[t−2]
−5 0 50
0.2
0.4
LLR
Probab
ility Default
Shifted
• Derive LLR from CDR states
• Optimize sample points
Analog-to-Digital Converter
Amplitude
Zero
ProbDensity
One
−10 −5 0 50
0.2
0.4
LLR
Probab
ility
• Optimize quantizationintervals of ADC
13 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Overview
1 Introduction
2 Error Correction in PON
3 Improved Receiver Architectures
4 Conclusion and Outlook
14 OWHTC2019 2019-02-27 Intel Connected Home Division
-
Conclusion and Outlook
Conclusion
• Coding is a key component for evolving fiber accesstechnologies
• Optimized channel coding requires
good understanding and modeling of the channelinnovative, cost-efficient transceiver designs
Outlook
• Coding in combination with improved modulation formats
• Digital signal processing and error correction coding
• Energy efficient designs for high throughput
15 OWHTC2019 2019-02-27 Intel Connected Home Division
IntroductionError Correction in PONImproved Receiver ArchitecturesConclusion and Outlook