Gigabit Home Networking (G.hn) is a specification for wired home networking that supports speeds up to 2 Gbit/s and operates over four types of legacy wires: telephone wiring, coaxial cables, power lines and plastic optical fiber. Some benefits of a multi-wire standard are lower equipment development costs and lower deployment costs for service providers (by allowing customer self-install). G.hn offers enhanced immunity to power line disturbances compared to other connection technologies. It serves as a bridge, connecting older systems prevalent in industrial settings with modern technologies that can revolutionize operations. While many machines and devices have transitioned to wireless, wired legacy systems remain integral for communication in industrial contexts. In the industrial realm, swift and dependable connectivity is crucial for seamless machine-to-machine interactions. Absence of this can lead to operational halts or reduced service quality. G.hn stands as a pivotal infrastructure for time-sensitive and safety-critical tasks, boasting strong features that support vital communications and a network's ability to auto-recover.

History

G.hn was developed under the International Telecommunication Union's Telecommunication Standardization sector (the ITU-T) and promoted by the HomeGrid Forum and several other organizations. ITU-T Recommendation (the ITU's term for standard) G.9960, which received approval on October 9, 2009, specified the physical layers and the architecture of G.hn. The Data Link Layer (Recommendation G.9961) was approved on June 11, 2010. Prominent organizations, including CEPca, HomePNA, and UPA, who were creators of some of these interfaces, rallied behind the latest version of the standard, emphasizing its potential and significance in the home networking domain. Moreover, the ITU-T extended the technology with multiple input, multiple output (MIMO) technology to increase data rates and signaling distance. This new feature was approved in March 2012 under G.9963 Recommendation. The development and promotion of G.hn have been significantly supported by the HomeGrid Forum and several other organizations. The technology was not only designed to address home-networking challenges but also found applications beyond this initial scope, showcasing its versatility and potential in the networking domain.

Technical specifications

Technical overview

G.hn specifies a single physical layer based on fast Fourier transform (FFT) orthogonal frequency-division multiplexing (OFDM) modulation and low-density parity-check code (LDPC) forward error correction (FEC) code. G.hn includes the capability to notch specific frequency bands to avoid interference with amateur radio bands and other licensed radio services. G.hn includes mechanisms to avoid interference with legacy home networking technologies and also with other wireline systems such as VDSL2 or other types of DSL used to access the home. OFDM systems split the transmitted signal into multiple orthogonal sub-carriers. In G.hn each one of the sub-carriers is modulated using QAM. The maximum QAM constellation supported by G.hn is 4096-QAM (12-bit QAM). The G.hn media access control is based on a time division multiple access (TDMA) architecture, in which a "domain master" schedules Transmission Opportunities (TXOPs) that can be used by one or more devices in the "domain". There are two types of TXOPs:

Optimization for each medium

Although most elements of G.hn are common for all three media supported by the standard (power lines, phone lines and coaxial cable), G.hn includes media-specific optimizations for each media. Some of these media-specific parameters include:

Security

G.hn uses the Advanced Encryption Standard (AES) encryption algorithm (with a 128-bit key length) using the CCMP protocol to ensure confidentiality and message integrity. Authentication and key exchange is done following ITU-T Recommendation X.1035. G.hn specifies point-to-point security inside a domain, which means that each pair of transmitter and receiver uses a unique encryption key which is not shared by other devices in the same domain. For example, if node Alice sends data to node Bob, node Eve (in the same domain as Alice and Bob) will not be able to easily eavesdrop their communication. G.hn supports the concept of relays, in which one device can receive a message from one node and deliver it to another node farther away in the same domain. Relaying becomes critical for applications with complex network topologies that need to cover large distances, such as those found in industrial or utility applications. While a relay can read the source and target addresses, it cannot read the message's content due to its body being end-to-end-encrypted.

Profiles

The G.hn architecture includes the concept of profiles. Profiles are intended to address G.hn nodes with significantly different levels of complexity. In G.hn the higher complexity profiles are proper supersets of lower complexity profiles, so that devices based on different profiles can interoperate with each other. Examples of G.hn devices based on high complexity profiles are Residential Gateways or Set-Top Boxes. Examples of G.hn devices based on low complexity profiles are home automation, home security and smart grid devices.

Technical parameters

The chart depicts a summary of the crucial technical specifications of the G.hn standard. Many of these technical elements are consistent across different physical media, with variations seen in areas such as Tone Spacing and frequency ranges. This uniformity is essential as it allows silicon manufacturers to produce a singular chip capable of implementing all three media types, leading to cost savings. Presently, G.hn chipsets are compatible with all three media types. This compatibility allows system manufacturers to create devices that can adjust to any wiring type simply by modifying a software configuration in the equipment.

Spectrum

The G.hn spectrum depends on the medium as shown in the diagram below:

Protocol stack

G.hn specifies the physical layer and the data link layer, according to the OSI model. The interface between the Application Entity and the Data Link Layer is called A-interface. The interface between the Data Link Layer and the physical layer is called Medium Independent Interface (MII). The interface between the physical layer and the actual transmission medium is called Medium Dependent Interface (MDI).

Support

HomeGrid Forum

The HomeGrid Forum is a non-profit trade group promoting G.hn. HomeGrid Forum members include:

Vendors

Vendors promoting G.hn include MaxLinear, ReadyLinks Inc, Lantiq, devolo AG, microprocessor manufacturer Intel, system-on-a-chip vendor Sigma Designs, and Xingtera, which announced a product in January 2013. The first live public demonstration of G.hn interoperability was shown at CES, January 10–13, 2012 by Lantiq, Marvell Technology Group, Metanoia, and Sigma Designs.

Service providers

On February 26, 2009, as part of a HomePNA press release, AT&T (which makes use of wireline home networking as part of its U-Verse IPTV service) expressed support for the work developed by ITU-T creating standards for home networking, including G.hn. Service providers like AT&T promoted G.hn for: Other service providers that are contributors to the work ITU-T Study Group include British Telecom, Telefónica, and AT&T.

Equipment vendors

In April 2008, during the first announcement of HomeGrid Forum, Echostar, a manufacturer of set-top boxes for the service provider market, expressed its support for the unified standard:

Consumer electronics

In March 2009, Best Buy (which is the largest retailer of consumer electronics in the United States) joined the board of directors of HomeGrid Forum and expressed its support for G.hn. Panasonic, one of the largest manufacturers of consumer electronics, is also a contributor member of HomeGrid Forum.

Analysts

In 2008, several marketing firms promoted G.hn and made optimistic predictions.

Other organizations

In July 2009, HomeGrid Forum and DLNA signed a liaison agreement "setting the stage for collaboration between the two organizations and the approval of G.hn as a DLNA-recognized Physical Layer technology". In June 2010, Broadband Forum and HomeGrid Forum signed an agreement to deliver a compliance and interoperability testing program for products using G.hn technology. The Broadband Forum will support HomeGrid Forum's validation of G.hn products, their promotion of product conformance and interoperability, and help expedite the total time to market for HomeGrid Forum Certified products. In May 2011, both organizations jointly announced the first open G.hn plugfest.

Related standards

ITU G.9970 (also known as G.hnta) is a Recommendation developed by ITU-T that describes the generic architecture for home networks and their interfaces to the operators' broadband access networks. ITU G.9972 (also known as G.cx) is a Recommendation developed by ITU-T that specifies a coexistence mechanism for home networking transceivers capable of operating over power line wiring. The coexistence mechanism would allow G.hn devices which implement G.9972 to coexist with other devices implementing G.9972 and operating on the same power line wiring. ITU G.9991 (also known as G.vlc) is a Recommendation developed by ITU-T that specifies the PHY and DLL for High speed indoor visible light communication transceivers, used in applications such as Li-Fi. G.vlc reuses the PHY and DLL of G.hn, enabling the same chips to be used for both applications.

Residential applications

The major motivation for wired home networking technologies was IPTV, especially when offered by a service provider as part of a triple play service, voice and data service offering such as AT&T's U-Verse. Smart grid applications like home automation or demand side management can also be targeted by G.hn-compliant devices that implement low-complexity profiles.

Industrial applications

G.hn technology facilitates the connection of devices across various network types using different wiring options, including coax, phone lines, power lines, and optical fiber. Initially designed for home networking, its applications expanded to encompass a broad spectrum of industrial scenarios. The ITU-T endorsed G.hn technology stands out as today's most adaptable and dependable network backhaul for multi-gigabit connectivity, spanning from residential and business applications to industrial and smart grid scenarios. G.hn is consistently advancing across various media, including coax, copper pairs, powerlines, and plastic optical fibers, as well as LiFi communication systems using visible light, ultraviolet, and infrared spectrums. This supports the industry's digital transformation. HomeGrid Forum members champion the worldwide adoption of G.hn, a unified networking technology with multiple sources.