Normal networks are designed to use coaxial cable, cat5 twisted pair cable, or even fiber optic cable. These cabling options provide clean, noise-free network environments dedicated solely to networking. Considering that phonelines were originally designed to only carry voice traffic, being able to run a network over regular household phonelines is pretty impressive.
Household phoneline wiring doesn't match the traditional spoke and wheel or chain network topologies. Home phonelines have a random tree topology with nodes everywhere in the house. Every unused phone jack isn't terminated. Recall that with 10Base2 networks, missing a terminator disables the entire network. Phoneline network technology must deal with the lack of termination along with signal noise from various household appliances. Phoneline networking systems also have to share the home phoneline with voice and DSL services.
Intel's AnyPoint system maintains a 1Mbps network over regular phonelines. Don't worry about not being to play multiplayer Starcraft or Quake 2. Phoneline networking technology uses standard Ethernet technology modified for the home phoneline environment. All normal networked programs will work on an AnyPoint network.
AnyPoint won't interfere with voice and DSL services. Thanks to Frequency Division Multiplexing, each communications service operates on its own frequency range. Phoneline networks operate in the 5.5MHz to 9.5MHz range, normal voice data operates in the 20Hz to 3.4kHz range, and DSL uses the 25kHz to 1.1MHz range.
How does Intel do it?
With Tut System's HomeRun technology:
Tut 1 Mbit/s technology is implemented using straightforward IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access/Collision Detect) methods for multiple access to a common communication's medium--the foundation of Ethernet. In simple terms, it's a 1 Mbit/s Ethernet over phoneline. This is an important design criterion, since it allows the HomePNA network to leverage the tremendous amount of Ethernet compatible software, applications, and existing hardware in the market today.
Transmitting data accurately over the random phoneline topology as detailed earlier is only part of the problem. To achieve high-speed data throughput, one must encode as much data as possible (instead of single pulse-bits) in each signal pulse. To accomplish this, multiple data bits are encoded into each pulse. Tut's unique and patented technology accomplishes this--delivering multiple bits in every pulse.
The core technology in the implementation is the Time Modulation Line Coding Method developed by Tut. This is the key to Tut's ability to transmit data on an arbitrary topology of unterminated wires found in homes. Tut's patented line coding mechanism incorporates an adaptive circuit which, by design, has the ability to adapt to varying noise. Within each network interface, the receiver circuit adapts to varying noise levels that might appear on the line. In addition, the transmitting circuit can vary its level of output signal strength. Both transmit and receive circuits continually monitor line conditions and adjust their settings accordingly.