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HomePlug 1.0 PHY

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

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HomePlug 1.0 PHY

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

  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 • (100,25,16) 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 0 1 2 … … … … ... … … … … 74 75 … ... 98 99 25 26 27… … … … … 74 75 … … 99 0 1 … … 24 50 51 52… … … … … 99 0 … … 24 25 … … … 49 75 76… … 99 0 … … 24 25 … … 49 50 … … … 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=7.5 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, 30.72 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 35.84 usec to allow processing time

  24. HP1.0 PHY Performance

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