ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 108)

Figure 5.3 illustrates the respective times of these various OFDM blocks.

The complete frame time is defined by adding the various OFDM symbol block

times. The maximum possible transmission speed and the bit rate concerning the

data link layer can be calculated in this way.

With a 2,705-byte frame, the maximum transmission speed is obtained in the

following way:

Bit rate

PHY_MAX

= 2,705 × 8 bits/1,534.86 μs = 14.1 Mbit/s

With an Ethernet data frame with a maximum length of 1,500 bytes, the maxi-

mum bit rate is the following:

Bit rate

PHY_MAX

= 1,500 × 8 bits/1,534.86 μs = 7.81 Mbit/s

Table 5.2 summarizes the maximum theoretical transmission speeds in the

HomePlug 1.0 standard. As we’ll see in part II of the book, these values are lower in

practice.

Physical Layer Frames 89

Figure 5.3 Complete HomePlug 1.0 frame OFDM symbol block times

Table 5.2 Maximum Transmission Speed According to Modulation Technique

MODE

ERROR CORRECTION CODE (FORWARD

ERROR CORRECTION)

MAXIMUM

TRANSMISSION SPEED

IN THEORY (Mbit/s)

DQPSK ¾ ¾ convolution code and Reed-Solomon code 14.1

DQPSK ½ ½ convolution code and Reed-Solomon code 9.19

DBPSK Convolution code and Reed-Solomon code 4.59

ROBO (DBPSK

½), repetition of

each bit four times

½ convolution code and Reed-Solomon code 1.02

1 2 ... 103 104 105 106 107 108 109 110 111 112 113 ... 348 349

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 108