Page 173 - From Smart Grid to Internet of Energy

150 From smart grid to internet of energy

FIG. 4.11 A PHY frame example for ITU-T Rec. G.9904. (From Narrowband orthogonal fre-
quency division multiplexing power line communication transceivers for PRIME networks, ITU-
T Rec. G.9904, October 2012. [Online] Available: http://www.itu.int/rec/T-REC-G.9904 (Fig. 7-
2), with permission.)

TABLE 4.7 PHY layer parameters of the ITU G.9904 PRIME standard
Sampling frequency (kHz) 250
FFT size 512
Carrier spacing (Hz) 488
Number of subcarriers 97
Used frequency band (kHz) 42–89
Pilot carrier number in the PHY 13
header
Cyclic prefix (μs) 192
Mapping schemes DBPSK, DQPSK, D8PSK
Forward error correction Convolutional code (with ½ rate and 7 constraint
length)
Interleaver Per symbol
Preamble length (ms) 2.048
Header length (ms) 4.48
Max payload length (ms) 63 2.24 ¼ 141.12

4.4.3.2 MAC layer
The MAC frames are used by the G.9904 devices for accessing the channel,
which are defined depending on the mixed time intervals. A typical MAC frame
structure is illustrated in Fig. 4.12. The channel access method in MAC layer is
characterized employing both CSMA/CA and time-division multiplexing
(TDM). The nodes on a network are able to access channel through shared