ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 72)

the number of possible PLC stations in the same PLC network (16 stations for

HomePlug 1.0 and 1.1 and 250 stations in HomePlug AV). Some values are

reserved for the ROBO mode or for particular implementations of the HomePlug

1.0 standard.

Segment Bursting and Contention-Free Access

Two particular modes, segment bursting and contention-free access, are used to

have access to a higher priority on the PLC network in order to send the successive

segments of a service block without waiting for mandatory contention windows

before transmitting the frames.

In the case of segment bursting, PLC stations with priority level CA3 can set the

CC (Contention Control) parameter to 1. It is then possible for the source station to

transmit two consecutive segments without waiting for a high contention value.

This mode improves the performance and can prove useful for applications of the

VoIP type demanding a particular priority exception.

Figure 3.21 illustrates the functionality of segment bursting, which makes it

possible for a PLC device to transmit a series of service blocks with maximum prior-

ity (CA3).

In the case of contention free access (CFA), the source station is allowed to send

all the segments with priority CA3 and to transmit seven consecutive MPDU by set

ting the CC field to 1.

Transmission Channel Functionalities 53

Figure 3.19 Tone map management between PLC devices

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 72