1. Powerline Communications: Channel Characterization and Modem Design
Yangpo Gao
Helsinki University of Technology

2. Thesis Contents Table of Contents
Introduction
PLC Technology Background
Channel Measurement and Modeling
Disturbance over PLC
DMT Based PLC Modem Design
Conclusion
Reference
This thesis is part of project “ PLC controlled LEDs for general lighting system”, which is sponsored by TEKES

3. Introduction

4. History of PLC and Motivation of Thesis
What is PLC
PLC – Powerline Communications
Using powerline as transmission medium for data communication
History of PLC
From high voltage (HV) low voltage (LV)
Low data rate high data rate
Control application multimedia data applications
Motivation
Cheap “the last mile” solution
However, worse channel than other wired network
Channel characterization reliable communications

5. PLC Technology Background

6. PLC Technologies Three network levels Efficient coupling
High voltage (110–380 kV)
Medium voltage (10–30 kV)
Low voltage (230/400 V, in the USA 110 V) (my thesis range)
Efficient coupling
Inductive coupling
Conductive coupling
Modulation and error correction
OFDM, DMT
CDMA
FEC

7. EMC Issues EMC --Electromagnetic compatibility
The ability of a device or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances in the form of interferences to any other system in that environment, even to itself.

8. Standardizations PLC standardization bodies International National
Regional
National

9. Channel Measurement and Modeling

10. Transmission Line Theory
A piece of mains cable can be modeled as following figure
Attenuation
constant
phase
Characteristic
impedance
Propagation
constant
R : resistance .
L : inductance.
G : conductance
C : capacitance

11. Channel Measurement Setup
Equipment:
Network Analyzer (NA)
Coupling Circuit
Coupling circuit
Conductive coupling
High pass filter
Galvanic isolation
Over Voltage protection

12. PLC Cable Measurements
Rapid fluctuation caused by impedance mismatch
Maximum of 4 dB attenuation 100 MHz
Cable transversal
Cable Type
Size (mm2)
Vulcanize rubber cable (three-wire)
0.75 1
PVC/PVC cable (three-wire)
PVC/PVC cable (two-wire)
0.5

13. PLC Channel Measurements
Scenario 1: Internet access and distribution
Scenario 2: Home networking
Scenario 1: Network topology is known, or easy to estimate. Channel is simple, and has few multipath components
Scenario 2: Network topology is unknown or it is hard to define. Channel acts as black box. A lot of multipath components

14. Channel Responses
Frequency
Domain
Time
Scenario 1
Scenario 2

15. PLC Channel Modeling
According to PLC channel multipath phenomenon, channel can be modeled as:

16. Disturbance over PLC

17. PLC Noise Noise Classification: Our concentration
Colored background noise
Narrowband noise
Periodic impulsive noise, asynchronous to the main frequency
Periodic impulsive noise, noise, synchronous to the main frequency
Asynchronous impulsive noise
Our concentration

18. Noise Measurement setup
Equipment:
Oscilloscope
Spectrum Analyzer
Coupler

19. Colored Background Noise
Quasi-Static behavior
Statistic information is extracted in table
Can be modeled as: s b c
Max
-94
-80
-0.4
Min
-124
-100
-0.6
Average
-105
-90
-0.5

20. Random Impulsive Noise
Caused by frequency bursts generated by electrical devices connected to the powerline.
Statistic information is extracted

21. Other Disturbance NEXT Formation FEXT Formation
NEXT (Near End crosstalk)
FEXT (Far End crosstalk).
NEXT Formation
FEXT Formation

22. DMT Based PLC Modem Design

23. DMT Technology Discrete Multi-tone Modulation (DMT) Advantages:
Multicarrier technology – combat frequency selective fading
Dynamic bit loading based on SNR – efficient spectrum utilization
High channel capacity

24. DMT Based PLC Modem Design
Simulation environment:
MATLAB SimuLink
MATLAB DSP Blockset
Simulated channel response
Expected result
Bit Error Rate (BER)

25. Simulation and Performance
Optimized bit loading algorithm
Modem performance
PLC vs AWGN
Signal spectrum
after PLC channel
Signal spectrum
before PLC channel

26. Publications Related to My Thesis

27. Publications More information can be found in my publications:
“Channel modeling and modem design for broadband power line communications”, Proceeding of ISPLC 2004, April, Spain
“Broadband characterization of indoor powerline channel”, Proceeding of ISPLC 2004, April, Spain
“Broadband Characterization of Indoor Powerline Channel and Its Capacity Consideration”, Proceeding of ICC 2005, May, Korea

28. Any Questions?
Thank You!