1. (c) 2013 R. Newman University of Florida
HomePlug 1.0 PHY
(c) 2013 R. Newman
University of Florida

2. What is HomePlug 1.0? Broadband PLC for home networking
Open industry standard
4 manufacturers (including Intellon)
Developed in 2000 by Homeplug Powerline Alliance (HPA)
Consortium of chip designers, OEMs, PLC users
Products shipped in 2001
First Ethernet class PLC, most widely available
11 Mbps coded PHY data rate
0ver 10 million units shipped ca. 2010
Comprises
PHY – modulation, coupling, FEC, etc.
MAC – medium access, ARQ, etc.
Bridging – to other PLC networks or to 802.3/11/etc.

3. HP1.0 PHY Orthogonal Frequency Division Modulation Cyclic prefix
Channel adaptation
FEC
Turbo product code
RS/CC concatenated code
Frames
Preamble
Delimiter
PHY body
Physical Carrier Sense (PCS)

4. HP1.0 Transmitter

5. HP1.0 Receiver

6. HP1.0 OFDM 128 evenly spaced carriers 0-25 MHz
5.12 us raw symbol time = 128 cycles 25MHz
256 IFFT samples at 50 MHz clock
Cyclic prefix set to typical delay spread
Reduces ISI
172 IFFT samples, with 8 samples roll-off
3.28 us guard interval
8.4 us total symbol time

7. Transmit Spectrum Mask
Band used by HomePlug 1.0
FCC part 15 rules in North America restricts PSD Depends on frequency (other uses)

8. HP1.0 OFDM Band used is 4.49-20.7 MHz
84 carriers fall in that band (23-106)
8 carriers unused (FCC amateur bands)
76 usable carriers
FCC Part 15 rules limit power spectral density
-50dBm/Hz PSD
Much lower than WiFi
OFDM (and high data rates) possible due to improved processing speeds/capabilities
Good coupling across all power phases
Need only couple to one hot line + neutral

9. HP1.0 Carrier Modulation 76 usable carriers
All modulated with same method
Method depends on channel adaptation
Modulation per carrier
Coherent BPSK (FC)
Differential BPSK (PHY payload)
Differential QPSK (PHY payload)
Up to 14 Mbps raw PHY rate
Physical Carrier Sense (PCS)
based on sync detection

10. HP1.0 PHY Frame Format

11. HP1.0 FEC Turbo product code/copy code Used in Frame Control (FC)
RS/CC concatenated code
Used in PHY Payload
Rate 1/2 and 3/4 code – adapted to channel
Up to 10 Mbps after coding
Robust Performance in presence of noise/jammers
ROBO mode for broadcast/multicast

12. HP1.0 Frame Control FEC Rate ¼ Turbo Product code
Derived from (10,5,4) shortened extended Hamming Code
Redundant Interleaver
4 symbols
1 bit per carrier
Repeat codeword with offsets 0,25,50,75 over the 4 symbols

13. HP1.0 Frame Control Interleaver
… … … … ... … … … … …
… … … … … … … … … 24
… … … … … … … … … … 49
75 76… … … … … … … … … 74
Cutoff for coded bits for 76 carriers
Make table with S rows (one row per symbol)
S = 4 symbols in FC
Fill each row with coded bits
Start row R with bit 25R for R=0,1,…,S
Step T = N/S, N = total coded bits
Fill bits of symbol R with bits from row R
Since BPSK, use first K bits, K = # carriers

14. HP1.0 Data FEC Reed-Solomon Code over GF(28)
23/39 – 238/254 for DBPSK, DQPSK
31/39 – 42/51 ROBO
Derived from systematic (255,239,t=8) or (255,247,t=4) code
Concatenated with Convolutional Code
Constraint length 7
Rate ½ or ¾

15. HP1.0 Convolutional Encoder
Convolutional Code
K=7
Puncture rate ½ code to get ¾ rate code

16. HP1.0 ROBO Mode
Used for broadcast/multicast, or for unicast when conditions are severe
Coherent BPSK on all unmasked carriers
31/39 – 43/51 Reed-Solomon Code
Rate depends on # unmasked carriers
Derived from same codes as DPSK
Convolutional Code
Same as for DPSK
Rate ½ only
Redundant Interleaver makes 4x copy code

17. HP1.0 Channel Adaptation Decide modulation and FEC rate
Determine channel characteristics – Sounding
DBPSK or DQPSK
Convolutional Code Rate (½ or ¾)
Tone Map specifies these, plus
Which carriers to drop (SNR too low)
RS rate adapted to # bits/PHY Tx block
Function of #carriers, bits/carrier, CC rate
PHY transmission block 20 or 40 symbols
139 distinct rates achievable – nearly continuous
1Mbps-14.1 Mbps
Use ROBO if rate is better

18. HP1.0 Channel Adaptation QPSK- ¾ QPSK-½ BPSK-¾ BPSK-½
First determine highest rate R = CM each carrier’s SNR can support
For each combination of coding C and modulation M rate, determine the
number N of carriers that can support it
Then find combination that maximizes the product NR = bits/symbol
e.g., QPSK ¾ has NR = 5x¾x2= QPSK ½ has NR = 15x½x2=15
BPSK ¾ has NR = 22x¾x1=16.5 , BPSK, ½ has NR = 25x½x1=12.5
QPSK

19. HP1.0 PHY PDU Preamble Set pattern of symbols Allows AGC, synch
Frame Control (FC)
Heavily coded, BPSK (low rate)
Very robust
Very few information bits (25)
FC holds info for PHY
Tone Map Index- for demodulation of body
Frame duration (how long to demodulate)

20. HP1.0 Preamble Preamble Sync symbols lack cyclic prefix (repeated)
+ and – forms (– is inverted +)
6 SYNC + symbols (give signal power, phase)
1 ½ SYNC – symbols (give time reference)
Detection used for PCS

21. HP1.0 PHY Frame Format Detect delimiter from preamble, correct FC
SOF FC indicates symbol count, tone map
Pad Frame Body to PHY Tx block boundary
EOF FC delimits end of data frame

22. HP1.0 PHY Transmit Blocks Basic unit of data transmission
20-symbol and 40-symbol PHY Tx Blocks
Frame Length field in SOF FC gives length
In multiples of 20 symbols
Start with as many 40 symbol PTBs as possible
End with zero or one 20 symbol PTB
Note that PHY Transmit Blocks are not numbered or acknowledged individually
Whole MPDU is acknowledged

23. HP1.0 Priority Resolution Slots
Two Priority Resolution Slots (PRS0 and PRS1)
Follow end of a complete transmission (PPDU plus response, if expected) and gap (CIFS)
Signal form is 6 SYNC– symbols
These symbols have no CP, usec. total
Same as preamble, but inverted and shorter
Multiple senders will constructively interfere
Acts like “OR” of priority bits
Priorities CA3=11, CA2=10,CA1=01,CA0=00
Start with MSB
If “1” assert bit, else listen if other STA asserts
If hear a “1” stop process, wait until next PRS0
Slot duration usec to allow processing time

24. HP1.0 PHY Performance