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Chapter 7. HomePNA

Chapter 7. HomePNA

Original Ethernet transceivers, such as those of 10BaseT, were based on simple line codes without signal processing and coding techniques. Consequently, dedicated (point-to-point) copper transmission media (twisted pair) needs to be installed. Using advanced signal-processing and -coding techniques provides dedicated twisted pair wiring more transmission capability and enables a home network to be built on a relatively low transmission quality in-house telephone wiring. The in-house wiring is usually of Category 3 cable quality or worse, sometimes without much twist. Furthermore, most in-house telephone wiring has a star daisy-chain topology. With a few wiring branches connected at the telephone service entrance point, all telephone jacks are interconnected at different locations of these branches. This star daisy-chain topology produces many more reflections compared with that of point-to-point topology. Signal-processing techniques such as channel equalization are very effective at compensating channel distortions caused by reflections. Much like the original coaxial cable–based Ethernet, a home network using in-house wiring as its transmission medium transmits packets on demand. Therefore, the enabling echo cancellation technique necessary for the full-duplex operation is not required.

After standards are established for DSL systems, many companies rushed ahead competing for the most effective realization of practical systems. Some other companies looked around for alternative markets applying the general idea and similar technology. Companies such as Tut Systems and Epigram, now a home network division of Broadcom, found the in-house wiring a very attractive transmission medium to which to apply advanced transceiver technologies. After extensive internal development by many companies, an industrial consortium called HomePNA was formed to promote the in-house wiring-based transmission technologies. Tut Systems' Pulse Position Modulation system was selected as the HomePNA 1.0 line code [1]. Although no extensive signal-processing techniques were used, the PPM line code is relatively effective at combating impairments such as reflection and noise commonly found in this particular home environment. Epigram's QAM line code was later selected as the standard for HomePNA 2.0 [2]. Adaptive equalization and spectrum reuse through FDQAM (Frequency Diverse QAM) enable HomePNA 2.0 to achieve a transmission throughput of up to 10 Mbps over common in-house telephone wiring. Through the duplication of the HomePNA 1.0 mechanism, HomePNA 2.0 is also backward-compatible. Home PNA 2.0 transceivers can talk to previously deployed HomePNA 1.0 transceivers.


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