HomePlug is the family name for various power line communications specifications that support networking over existing home electrical wiring. Several specifications exist under the HomePlug moniker, with each offering unique performance capabilities and coexistence or compatibility with other HomePlug specifications.
Some HomePlug specifications target broadband applications such as in-home distribution of low data rate IPTV, gaming, and Internet content, while others focus on low-power, low throughput, and extended operating temperatures for applications such as smart power meters and in-home communications between electric systems and appliances. All of the HomePlug specifications were developed by the HomePlug Powerline Alliance, which also owns the HomePlug trademark.
|Common name||IEEE standard|
|Common name||ITU-T recommendation|
|G.hn/HomeGrid||G.9962 (Management Plane)|
|G.hn/HomeGrid||G.9964 (PSD Management)|
The HomePlug Powerline Alliance was formed to develop standards and technology for enabling devices to communicate with each other, and the Internet, over existing home electrical wiring. One of the greatest technical challenges was finding a way to reduce sensitivity to the electrical noise that is inevitably present on power lines. Whenever an appliance is turned on or off, it creates electrical noise that can interfere with data transfer through the wiring. Noise sensitivity was problematic in early powerline technology, though later versions have solved this problem. Also, early powerline technology could not reliably communicate across different electrical phases. HomePlug solved this problem by increasing the communication carrier frequencies so that the signal is conveyed by the neutral conductor, which is common to all phases.
The first HomePlug specification, HomePlug 1.0, was released in June 2001. The HomePlug AV specification, which was released in 2005, increased physical layer (PHY) peak data rates from 14 to 200 Mbit/s. The HomePlug Green PHY specification was released in June 2010 and targets Smart Energy and Smart Grid applications as an interoperable "sibling" to HomePlug AV with lower cost, lower power consumption and decreased throughput. (HomePlug Command and Control low frequency specification was released in 2007, but later deprecated and replaced by HomePlug Green PHY.)
On September 30, 2010, the IEEE’s 1901 Broadband Powerline Standard was approved and HomePlug AV, as baseline technology for the FFT-OFDM PHY within the standard, is now ratified and validated as an international standard. The HomePlug Powerline Alliance is a certifying body for IEEE 1901 products. The three major specifications published by HomePlug (HomePlug AV, HomePlug Green PHY and HomePlug AV2) are interoperable and compliant. 
As of November 2011, there are 4 chip vendors that are shipping interoperable HomePlug AV chipsets with IEEE 1901 support (Broadcom, Qualcomm Atheros, Sigma Designs, and SPiDCOM) and millions of units are shipped each month throughout the world. Many HomePlug AV products are shipping from key vendors such as TP-LINK, ATRIE Technology P Limited, Cisco, devolo, ZyXEL, D-Link, Logitech, NETGEAR and Western Digital. Major IPTV service providers such as France Telecom, British Telecom, and Deutsche Telekom are also shipping large volumes of HomePlug products. In November 2011, the HomePlug Green PHY specification was adopted by 7 key American and German automobile companies, Ford, General Motors, Audi, BMW, Daimler, Porsche, and Volkswagen, as a connectivity standard for Plug-In Electrical Vehicle.
Newer versions of HomePlug support the use of Ethernet in bus topology. This is achieved by means of OFDM modulation that enables several distinct data carriers to coexist in the same wire. Also, HomePlug's OFDM technology can turn off (mask) any sub-carriers that overlap previously allocated radio spectrum in a given geographic region, thus preventing interference. In North America, for instance, HomePlug AV only uses 917 of 1155 sub-carriers.
The major benefit of powerline networking is that users can easily establish a network using a home's existing electrical wiring as the communication medium. There is no need to drill holes in walls or ceilings to route new wiring and, as a result, installation is quick, easy and relatively inexpensive. Powerline networking is an easily accomplished networking method for AC-powered devices, which by necessity must already be near power outlets.
Because AC power lines necessarily run to every device drawing a substantial number of watts, HomePlug is particularly relevant to home control and home area networks. Unlike any other control technology, no additional wire or wireless connection is required to get 100-1000 megabit speeds at low latency to every AC device. The HomePlug Green PHY specification addresses these purposes but also scales to faster, higher-power, lower-latency HomePlug AV and HomePlug AV2 - making HomePlug the logical technology for such control networks. For electric vehicle charging, the SAE J1772 standard plug-in electric vehicle charger also requires HomePlug Green PHY (see below) to establish communications over a powerline before the vehicle can begin to draw any charging power.
All commercial HomePlug implementations meet the AES-128 encryption standard specified for advanced metering infrastructure by the US FERC. Accordingly, these devices are suitable to deploy as utility grade meters off the shelf with appropriate software.
As of late 2012, the most widely deployed HomePlug devices are "adapters", which are standalone modules that plug into wall outlets (or power strips or extension cords) and provide one or more Ethernet ports. In a simple home network, the Internet gateway router connects via Ethernet cable to a powerline adapter, which in turn plugs into a nearby power outlet. A second adapter, plugged into any other outlet in the home, connects via Ethernet cable to any Ethernet device (e.g., computer, printer, IP phone, gaming station). Communications between the router and Ethernet devices are then conveyed over existing home electrical wiring. More complex networks can be implemented by plugging in additional adapters as needed. A powerline adapter may also be plugged into a hub or switch so that it supports multiple Ethernet devices residing in a common room.
Increasingly, the functionality found in standalone adapters is being built into end devices such as power control centers, digital media adapters, and Internet security cameras. It is anticipated that powerline networking functionality will be embedded in TVs, set-top boxes, DVRs, and other consumer electronics, especially with the emergence of global powerline networking standards such as the IEEE 1901 standard, ratified in September 2010.
Several manufacturers sell devices that include 802.11n, HomePlug and four ports of gigabit ethernet connectivity for under US$100. Several are announced for early 2013 that also include 802.11ac connectivity, the combination of which with HomePlug is sold by Qualcomm Atheros as its Hy-Fi hybrid networking technology, an implementation of IEEE P1905. This permits a device to use wired ethernet, powerline or wireless communication as available to provide a redundant and reliable failover - thought to be particularly important in consumer applications where there is no onsite expertise typically available to debug connections.
The first HomePlug specification, HomePlug 1.0, provides a peak PHY-rate of 14 Mbit/s. It was first introduced in June, 2001 and has since been replaced by HomePlug AV. 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.
HomePlug 1.0 Turbo adapters comply with the HomePlug 1.0 specification but employ a faster, proprietary mode that increases the peak PHY-rate to 85 Mbit/s.
The HomePlug AV specification, which was introduced in August 2005, provides sufficient bandwidth for applications such as HDTV and VoIP. HomePlug AV offers a peak data rate of 200 Mbs at the physical layer, and about 80 Mbs at the MAC layer. HomePlug AV devices are required to coexist, and optionally to interoperate, with HomePlug 1.0 devices.
Utilizing adaptive modulation on up to 1155 OFDM sub-carriers, turbo convolution codes for error correction, two-level MAC framing with ARQ, and other techniques, HomePlug AV can achieve near the theoretical maximum bandwidth across a given transmission path. For security reasons, the specification includes key distribution techniques and the use of 128 bit AES encryption. Furthermore, the specification's adaptive techniques present inherent obstacles to eavesdropping and cyber attacks.
The HomePlug AV2 specification was introduced in January 2012, it is interoperable with HomePlug AV and HomePlug GreenPHY devices and is IEEE 1901 standard compliant. It features gigabit-class PHY-rate, support for MIMO PHY, repeating functionalities and power saving modes.   Can use the bandwidth from 30-86 MHz as additional bandwidth. The first generation are generally considered to be 20% faster than HomePlug AV 500, it is often sold as HomePlug 600. They do not support MIMO, but only single streams due to the Atheros chipset architecture (QCA7450/AR1540). October 2013 Qualcomm announced the QCA7500 with support for 2x2 MIMO which supposedly will double data transfer rates. Devolo from Germany has made proprietrary improvements on the standard, and are using the ground wire in addition to phase and null.
HomePlug Green PHY
The HomePlug Green PHY specification is a subset of HomePlug AV that is intended for use in the smart grid. It has peak rates of 10 Mbit/s and is designed to go into smart meters and smaller appliances such as HVAC thermostats, home appliances and plug-in electric vehicles so that data can be shared over a home network and with the power utility. High capacity broadband is not needed for such applications; the most important requirements are low power and cost, reliable communication, and compact size. GreenPHY uses up to 75% less energy than AV. The HomePlug Powerline Alliance worked with utilities and meter manufacturers to develop this 690-page specification. HomePlug Green PHY devices are required to be fully interoperable with devices based on HomePlug AV, HomePlug AV2 and IEEE 1901 specification.
HomePlug Access BPL
Access Broadband Power Line (BPL) refers to a to-the-home broadband access technology. The HomePlug Alliance formed the HomePlug Access BPL Working Group, whose first charter was to develop the Market Requirements Document (MRD) for a HomePlug Access BPL specification. The Alliance made an open invitation to the BPL industry to participate in the development of or provide input for consideration in the MRD. After several months of collaboration between utilities, ISPs and other BPL industry groups, the MRD was completed in June 2005. HomePlug's work on the Access BPL was subsequently contributed and merged into the IEEE 1901 standard.
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. If you do not change this password, an attacker can use their own homeplug device to detect yours, and then use the default password to access and change settings such as the encryption key used.
On many new powerline adapters that come as a boxed pair, a unique security key has already been established and the user does not need to change the password, unless using these with existing powerline adapters, or adding new adapters. Some manufacturers supply adapters with security key buttons on them, allowing users to easily set unique security keys by plugging each unit in one at a time and pressing the button on the front (see more detailed instructions that come with the units).
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 (Ethernet side) 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. The HomePlug AV standard uses 128-bit AES, while the older versions use the less secure DES.
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 . 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.
HomePlug AV, GP and AV2 are fully interoperable, and will also interoperate with IEEE 1901 devices. HomePlug 1.0 devices do not interoperate with HomePlug AV devices. Although it is technically possible to achieve such backward compatibility, doing so is not economically feasible because of the high cost of circuitry that would have to support different Forward error correction (FEC) techniques and feature sets.
HomePlug devices will not interoperate with devices that employ other powerline technologies, such as Universal Powerline Association (UPA), HD-PLC, or G.hn. In the case of G.hn, it was deemed prohibitively expensive to implement both HomePlug's turbo coding forward error correction and G.hn's low density parity check (LDPC).
HomePlug devices are not compatible with certain power strips, surge protectors, and uninterruptible power supplies incorporating filters, which block the high-frequency signal. In such cases, the installer must plug devices directly into building electrical receptacles. If a spare power point is not available, a double adapter can be used in many cases with the incompatible device on one side and the HomePlug device on the other.
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- HomePlug AV 500 Adapter Roundup
- HomePlug AV2 Technology
- HomePlug GreenPHY Overview
- HomePlug GreenPHY Specs
- EDN, Voices: Intellon’s Mark Hazen on the HomePlug AV powerline-networking alternative
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