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Chapter 7. HomePNA > HomePNA 1.0

7.1. HomePNA 1.0

The idea of an existing telephone wiring–based home network system was originated from Tut System. Matt Taylor, the founder of Tut System, worked with his engineers to develop a proper signaling method over the home telephone wiring system. They had constructed a patch panel with telephone cables of different lengths to emulate some worst-case topologies. They found that the channel dispersion becomes a major impairment when the pulse-signaling rate approaches 200 kHz. To carry more information bits per signaling symbol while avoiding extensive signal processing, the PPM was used. In a PPM system, the time interval between adjacent pulses is slightly different depending upon the encoded information. The next pulse's position starts when the reflection becomes negligible. A number of next pulse positions are located to represent data bits to be transmitted. Two positions can be used to carry 1 bit, four positions carry 2 bits, eight positions carry 4 bits, and so on. Furthermore, Tut Systems' HomePNA 1.0 proposal has used the Run Length Limited (RLL) codes to increase the coding efficiency by about 10%.

7.1.1. Summary of HomePNA 1.0 Specifications

The HomePNA 1.0 signaling method can be analyzed by examining its general frame structure as shown in Figure 7.1. A HomePNA 1.0 transmitter encapsulates the binary information of an Ethernet packet by adding a header to it. The header consists of eight synchronization symbols followed by two data training symbols and a Proprietary Communication (Reserved), or PCOM, period. This header replaces the preamble and Start Frame Delimiter of the Ethernet packet. Symbol 0 is the null synchronization symbol consisting of two pulses. Symbols 1 through 4 carry transceiver Access ID (AID) information. With each AID symbol carrying 2 bits, a total of 8 bits are allocated for AID. This leads to 256 different AID combinations. Symbols 5 and 6 are used for transmitting remote control management commands across the network. Symbol 7 is a silence interval. On the other hand, many more data bits are encoded into an equivalent synchronization symbol interval. Because of the run length encoding, there is no exact timing boundary for every data-bits-carrying symbol. The end symbol is a nonvalid data symbol with the pulse position anywhere beyond those defined for data symbols. Training symbols and the PCOM period (all zeros by default) are defined by operation procedures through the management layer.


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