Nessum. Nessum, previously HD-PLC (short for 'High Definition Power Line Communication'), is a communication technology standardized by the Institute of Electrical and Electronics Engineers (IEEE). It is standardized as IEEE 1901-2020. 
The standard is to be used to communicate data over wired and wireless media using high frequencies between ~500kHz and ~56 MHz bands. The Nessum Alliance is the certifying body for compatibility between Nessum-based communication devices.

Overview 
Nessum offers two types of communication: wired (Nessum WIRE) and wireless (Nessum AIR).

Wired communication 
Nessum WIRE can be used for various types of wires such as power lines, twisted pair wiring, coaxial cables, and telephone lines. The communication distance can range between tens of meters to several kilometers depending on the use case. In addition, when an automatic relay function called multi-hop (ITU-T G.9905) is utilized, a maximum of 10 stages of relay is possible to extend the range, and support various network topologies (Ring, Star, Bus, MESH). With a maximum physical speed of 1 Gbps and effective throughput ranging from several Mbps to several hundred Mbps, this technology is used to reduce network construction costs and complexity by utilizing the existing lines or dedicated lines.

Wireless communication 
Nessum wireless communication is called Nessum AIR. It uses magnetic field communication for short range communication. The communication distance can be controlled in the range of a few centimeters to 100 centimeters. Maximum physical speed is 1 Gbps, with an effective speed of 100 Mbps.

Technical overview

Physical layer (PHY) 
The physical layer uses Wavelet OFDM (Wavelet Orthogonal Frequency Division Multiplexing), while a guard interval is required in ordinary OFDM systems. The Wavelet OFDM system eliminates the guard interval and increases the occupancy rate of the data portion, thereby achieving high efficiency. In addition, due to the bandwidth limitation of each subcarrier, the level of sidelobes is set low, which facilitates the formation of spectral notches. This minimizes interference with existing systems and allows for flexible compliance with frequency utilization regulations. Furthermore, Pulse-Amplitude Modulation (PAM) is used for each subcarrier, and the optimal number of modulation multi-levels is set according to the conditions of the transmission path, thereby improving transmission efficiency. The frequency band used can be selected from among standardized patterns.

Data link layer (MAC) 
The data link layer manages quality of service and other control functions using control frames "beacons" broadcast periodically by the parent to all terminals in the network. The basic media access methods are Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA) and Dynamic Virtual Token Passing (DVTP), which dynamically assign transmission rights to terminals in the network and avoid collisions, The system uses a collision avoidance mechanism.

Specification and features 
There are essentially two different types of HD-PLC: HD-PLC Complete and HD-PLC Multi-hop. They are incompatible.

HD-PLC Complete 
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This is for high speed applications such as TV, AV, and surveillance cameras. 

The major technical features include: 

 IEEE 1901 full compliant
 QoS by the priority control
 CSMA/CA and DVTP(Dynamic Virtual Token Passing) supported
 Concurrent multi-AV stream, VoIP, and file transfer and file transfer supported using IP packet classification
 Multi-network access at priority CSMA/CA with network synchronization

HD-PLC Multi-hop 

Source:

This is for long-distance applications such as smart meter, building network, factory, energy management, and IoT devices. 

The major technical features include: 

 ITU-T G.9905 multihop technology

Common features 
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 Uplinking/downlinking through 432 of 26 MHz (between 1.8 MHz and 28 MHz) bandwidth subcarriers with Wavelet OFDM
 Maximum 240 Mbit/s PHY rate
 Multilevel modulation for each subcarrier which suits the properties of the power line transmission channel and allows for the best transmission speed
 Subcarrier masking with the arbitrary number which can comply with the rules in each country
 Forward error correction (FEC) which enables effective frame transmission
 Channel estimation launch system with change detector for cycle and transmission channel
 HD-PLC network bridging compatible to Ethernet address system
 Advanced encryption with 128 bit AES

4th-generation HD-PLC (HD-PLC Quatro Core technology) 
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We now come to communication speed issues like high-definition video images (4K/8K) or in some cases multi hop technology is not enough to reach an isolated and distant PLC terminal. HD-PLC Quatro Core has been designed to solve these problems. This technology is an improvement on the conventional HD-PLC in both communication distance and speed. It achieves to double conventional HD-PLC's communication distance by adopting a communication band of 1/2 or 1/4 of conventional HD-PLC band and achieves to offer a maximum physical line transmission rate of 1 Gbit/s by using an expanded communication band 2 or 4 times the conventional HD-PLC band.

This evolution of the standard therefore offers either an extended range in a larger building, at the cost of a lower data rate, or a higher data rate, but achievable over shorter distances than in the previous version of the standard.

Use cases 
There are a few strengths of using HD-PLC technology on existing wires.

 Expectable higher speed performance

 Cost reduction on network construction by existed infrastructure

 Support the area where the radio waves is difficult to be reached

 Wire saving by sharing power lines and communication lines

Typical use case include: 

 HVAC systems
 Building Automation
 Photovoltaic (solar) panel communications
 Smart metering

 Meter to grid communications
 Smart street lighting
 Surveillance camera systems
 Video entry systems
 Communications in tunnels
 Robot wiring optimisation

Nessum Alliance 
Nessum Alliance was established in September 2007 as a voluntary association, originally under the name of "HD-PLC Alliance". In October 2023, the HD-PLC Alliance was renamed the Nessum Alliance.  

Nessum Alliance is a certifying body for compatibility between communication devices that comply with the international standard IEEE 1901-2020. Associated organisations are the Japanese Telecommunication Technology Committee (TTC) The Taiwanese Industrial Technology Research Institute and the IEEE Standards Association.

At the outset of 2025 the Nessum Alliance listed 37 member companies and organisations.

History 
This technology is based on HD-PLC, a type of power line communication developed by Panasonic in the early 2000s. HD-PLC was developed for room-to-room transmission of audio and video data at the time, but later began to be used not only for power lines but also for coaxial lines and twisted pair lines, and even for wireless communication. The name "power line communication" did not match the reality of the situation. In September 2023, Panasonic Holdings Corporation changed the name of HD-PLC to Nessum.

See also
BACnet
Power line communication
HomePlug
G.hn
HomePNA
IEEE 1901
KNX
LonWorks

References

External links 
 Nessum Alliance

Computer networking