ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 190)

Figure 8.16 illustrates how a power strip must be used with a PLC device. A

power strip is inherently a source of noise for PLC devices to which the noise of dis-

turbing devices connected to it must be added. In all cases, it is preferable to connect

the PLC device directly to the wall outlet whenever possible or to connect it to a

“biplite” (two outlet wall power strip).

Network Data Rates

In addition to electromagnetic disturbances, a PLC network is subject to constraints

related to the technology itself. These constraints relate to the data rate that never

corresponds to the expected rate and security.

The theoretical data rate of HomePlug 1.0 networks is between 1 Mbit/s and 14

Mbit/s. The 14-Mbit/s data rate is only a theoretical value roughly corresponding to

a useful throughput of 5 Mbit/s, i.e., 0.625 Mb/s. HomePlug Turbo and AV provide

a theoretical data rate of 5 to 85 Mbit/s and 10 to 200 Mbit/s, respectively, for a use-

ful throughput of 1 to 20 Mbit/s and 5 to 60 Mbit/s, respectively.

The size of the frame headers used in HomePlug and the use of a number of

mechanisms enabling a reliable transmission in an electrical environment mainly

explain this difference. Part of the transmitted data is used for the control and man-

agement of the transmission to make it reliable. Only a fraction of the data rate

emitted by the device corresponds to the conveyance of the data itself.

Useful Throughput Calculation

The useful throughput corresponds to the rate for data transmitted at OSI layer

level n. The useful throughputs of levels 1, 2, 3, and so forth correspond to the rates

Network Data Rates 171

Figure 8.16 Optimum use of power strips and double outlets

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 190