ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Pobierz pdf (Strona 34)

CHAPTER 2

Architecture

PLC, or power line communication, is the generic name for a network technology

that transmits data over electrical wiring. It is the result of extensive research on

high bandwidth data transmission on the power line medium.

The architecture of PLC networks is comparable in many aspects to that of

wired networks, but also to that of Wi-Fi networks, as we will see in this chapter.

HomePlug was the first PLC specification to provide a bit rate between 1 and 5

Mbit/s. Furthermore, HomePlug has implemented new techniques for connecting

devices to the network, as we will examine in detail.

The HomePlug specification is in constant evolution. Multiple revisions have

resulted in higher data rates, which remain limited by the shared nature of the

medium. Additional improvements have been made in the areas of functionality,

service quality, and security. The HomePlug alliance is currently the sole de facto

PLC standard, but as we saw in Chapter 1, the ETSI (European Telecommunica-

tions Standards Institute) and IEEE have started their own standards processes.

This chapter introduces the overall architecture of PLC networks and provides

detailed coverage of the two main layers: the physical layer and the data link layer.

Architecture of Electrical Networks

PLC (Power Line Communications) technology allows data transmission over elec-

trical wiring. The electrical wiring is therefore the medium for data transmission,

corresponding to the physical layer in the OSI model. Unlike other physical commu-

nication media like UTP (Ethernet cable), coaxial cable, fiber optic cable, and so

forth, this role supporting data transmission is not the principal function of the elec-

trical wiring. Data transport is therefore a complementary function to delivery of

electrical power (approximately 110 V/60 Hz in the United States and Japan and

220 V/50 Hz in Europe) by the wiring that powers electrical devices from the public

electrical network.

Electrical networks are classified according to their voltage level, as shown in

Table 2.1.

This classification of electrical networks according to voltage levels allows the

roles of associated organizations to be separated according to their area of responsi-

bility.

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 348 349

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