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HomePlug Powerline Alliance

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The HomePlug Powerline Alliance was founded in 2000 to promote and standardize networking over power lines. The alliance is the largest and oldest powerline networking trade association with 73 members, and has developed successive specifications for both broadband applications such as HDTV and low-speed command and control applications such as home security. It has certified over 170 products from multiple vendors.

Operation

The installation of a powerline network is mainly plugging in the powerline device and connecting it to the device you want on the network. A typical installation starts with connecting a powerline adapter to a router with a Ethernet cable, and then plugging the powerline adapter into the nearest power outlet. To add other devices to the network simply plug in a powerline adapter to an outlet near the device to be connected, and connect that device to the adapter via Ethernet. The powerline adapter can also be plugged into a hub or switch when multiple devices (computers, printers, IP phones, etc.) need to be connected in a single room.

Due to problems with early (pre-HomePlug 1.0) powerline technology propagating signals effectively across electrical phases in a house, there is a perception that powerline is an unreliable solution which only works in newer houses, or over short distances. This problem was effectively solved with HomePlug 1.0, and succeeding specifications such as HomePlug AV have made further improvements in whole home coverage.

Among other things, HomePlug allows the use of Ethernet in bus topology, which is very desirable in some circumstances. This is achieved by use of advanced OFDM modulation that allows co-existence of several distinct data carriers in the same wire. The use of OFDM also allows turning off (masking) one or more of the sub-carriers which overlap previously allocated radio spectrum in a given geographic region. In North America, for instance, HomePlug AV only uses 917 of 1155 sub-carriers.[1]

Security

Since signals may travel outside the user's residence or business and be eavesdropped on, HomePlug includes the ability to set an encryption password. The HomePlug specification requires that all devices are set to a default out-of-box password — although a common one. Users should change this password.

To simplify the process of configuring passwords on a HomePlug network, each device has a built-in master password, chosen at random by the manufacturer and hard-wired into the device, which is used only for setting the encryption passwords. A printed label on the device lists its master password.

The data at either end of the HomePlug link is not encrypted (unless an encrypted higher-layer protocol such as TLS or IPsec is being used), only the link between HomePlug devices is encrypted.

Since HomePlug devices typically function as transparent network bridges, computers running any operating system can use them for network access. However, some manufacturers only supply the password-setup software in a Microsoft Windows version; in other words, enabling encryption requires a computer running Windows [1]. Once the encryption password has been configured, Windows will no longer be needed, so in the case of a network where all computers run other systems a borrowed laptop could be used for initial setup purposes.

Versions

The HomePlug powerline alliance has defined the following specifications:

  • HomePlug 1.0 — Released June 2001 — Specification for connecting devices via power lines in the home. Theoretical speed of 14 Mbit/s.
  • HomePlug AV — Released December 2005 — Designed for transmitting HDTV and VoIP around the home. Theoretical PHY datarate of up to 189 Mbit/s.[1]
  • HomePlug Access BPL (BPL) — under development — A working group to develop a specification for to-the-home connection.
  • HomePlug Command & Control (HPCC) — Released October 9, 2007 — It's a low-speed, very low-cost technology intended to complement the alliance's higher-speed powerline communications technologies. The specification enable advanced, whole-house control of lighting, appliances, climate control, security and other devices.

1.0

The original HomePlug 1.0 specification allows for speeds up to 14 Mbit/s half-duplex.

On May 28, 2008 Telecommunications Industry Association (TIA) incorporated HomePlug 1.0 powerline technology into the newly published TIA-1113 international standard. TIA-1113 defines modem operations on user-premises electrical wiring. The new standard is the world's first multi-megabit powerline communications standard approved by an American National Standards Institute (ANSI)-accredited organization.

Many old 85 Mbit/s devices are erroneously referred to be HomePlug. They are instead based on Intellon's proprietary 85 Mbit/s Turbo mode. The error is induced by the fact that INT5500 Chip Set is compatible with both HomePlug 1.0 specifications and Intellon Turbo technology and the two technology are called HomePlug 1.0 with Turbo on the whole.

AV

The HomePlug AV specification was designed to provide sufficient bandwidth for applications such as HDTV and VoIP. Utilizing adaptive modulation on up to 1155 OFDM sub-carriers, turbo convolution codes for error correction, two-level MAC framing with ARQ,[2] and other techniques, HomePlug AV can achieve near the theoretical maximum bandwidth across a given transmission path.[1] Key distribution techniques and the use of 128 bit AES encryption are specified as mandatory in the specification. Furthermore, even the interception of data exchanged between HomePlug AV devices poses a "significant challenge" for an attacker due to the adaptive techniques used to modulate the signal between two given points.[3][4]

According to the HomePlug AV specification, HomePlug AV devices may interoperate with Homeplug 1.0 devices, but this support is optional. It is mandatory for HomePlug AV devices to coexist with HomePlug 1.0 devices.

Command & Control

Command & Control is a lower-speed specification intended for applications such as HVAC or lighting control.

Interoperability

The alliance certifies products for HomePlug compliance. Devices marked with the certification mark will interoperate with each other. However, they will not work with other powerline technologies from Panasonic or DS2 which offer similar speeds.

According to the organization, existing HomePlug (1.0, Turbo, GP, AV, AV2) devices will not interoperate with products based on the new G.hn standard (for power lines, phone lines and coaxial cables) developed by ITU-T. On March 2009, Rob Ranck (then president of HomePlug) said during an interview with EE Times:

The heart of the issue is that HomePlug uses turbo coding forward error correction while G.hn is proposing low density parity check (LDPC). The two are incompatible and supporting both techniques would make HomePlug chips large and expensive, Ranck said.

— EE Times, "Debate breaks out over home net standards", March 2009, [5]

Differences in Forward error correction (FEC) are also one of the reasons why HomePlug 1.0 devices do not interoperate with HomePlug AV devices:

Though it is possible to build a backward-interoperable device, the complexity would be prohibitively expensive to our customers. Such a device would have to include the ability to switch between FEC techniques and many other features, which places cost at an unworkable level.

— EDN, "Voices: Intellon’s Mark Hazen on the HomePlug AV powerline-networking alternative", [6]

Coexistence

HomePlug, along with other organizations such as CEPCA, UPA and HD-PLC, is participating in developing the IEEE P1901 standard for powerline communications. P1901 defines a set of multiple non-interoperable PHY and MAC specifications and a coexistence protocol between them. Although different P1901 devices may not interoperate, they will coexist with each other.[7]

See also

References

  1. ^ a b c Katar, S. (2006). "Harnessing the potential of powerline communications using the HomePlug AV Standard" (PDF). RF Design: 16–26. Retrieved 2008-01-06. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  2. ^ Katar, Srinivas. "Efficient Framing and ARQ for High-Speed PLC systems" (PDF). Retrieved 2008-01-07. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Newman, Richard. "HomePlug AV Security Mechanisms" (PDF). Retrieved 2008-01-06. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ Newman, Richard. "Protecting Domestic Power-line Communications" (PDF). Retrieved 2008-01-06. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ Debate breaks out over home net standards
  6. ^ EDN, Voices: Intellon’s Mark Hazen on the HomePlug AV powerline-networking alternative
  7. ^ Recent Developments in the Standardization of Power Line Communications within the IEEE, (Stefano Galli et al, IEEE Communications Magazine, July 2008), provides an overview of P1901 PHY/MAC proposal
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