PowerLAN

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Powerline Communication (PLC) orPowerline forshort, also calledPowerLANby some manufacturers, describes a technology thatusesexistingelectrical linesin thelow-voltage networkto set up a localnetworkfordata transmission, so that no additional cabling is necessary.

As of 2019 there are three globally dominant standards:

IEEE-1901-FFT and IEEE-1901-wavelet use a very similar MAC frame format, which is introduced with a beacon, and differ essentially in the modulation used and the QoS levels (4 vs. 8). ITU G.hn, on the other hand, uses largely the same modulation methods as IEEE-1901-FFT, but has a MAC frame format that does not require a beacon and instead uses a map communicated in the previous frame (figure), in which the structure of the following Mac -Frame is communicated to all receiving stations. The three standards are therefore incompatible with one another and cannot exchange data with one another. This is particularly confusing for users of power network adapters if a manufacturer offers devices with different standards that have a similar design on the outside but are nonetheless incompatible with one another, such as the devices in the dLAN series from Devolo that use IEEE -1901-FFT and the devices of the MAGIC 2 series from the same manufacturer, which are based on ITU G.hn.

Data can be transmitted with a maximum of 2000 Mbit / s with a range of up to 300 m via adapters according to the Homeplug or IEEE-1901-FFT standard, while adapters according to the ITU-G.hn standard can transfer 2400 Mbit / s gross with a range of up to 500 m.

functionality

dLAN 200 AVplus adapter of devolo with sockets by looping and up to 200 Mbit / s transfer rate

From a technical point of view, the PowerLAN is a carrier frequency system that is implemented using an adapter . These are plugged into a socket and connected to an end device (e.g. a PC, printer or game console) via a built-in Ethernet interface. The data signal of the connected device is modulated by the transmitting adapter in the high frequency range , usually between 2  MHz and 68 MHz, on the power line and demodulated again by the receiving adapter . From the point of view of the power grid, Powerlan signals are disturbances which, if installed correctly, are within the tolerance limits for electromagnetic compatibility and have no effect on the power supply.

With PowerLAN, the electrical lines available in a household with a voltage of 230 V and 50 Hz or 60 Hz are also used to transmit data. With the help of orthogonal frequency division multiplexing (OFDM) already used in other transmission methods (e.g. xDSL or WLAN ), a large number of signals are phase- and amplitude-modulated simultaneously on a carrier frequency ( frequency division multiplex method ). The frequency spectrum available depending on the transmission standard is divided into channels in order to reduce the susceptibility to interference or to enable appropriate countermeasures ( error correction and interleaving processes ). The modulated data is then sent to the receiver via the power line, where the carrier frequencies are separated from the power supply and demodulated using a bandpass .

The devices based on the homeplug standard, which are particularly widespread in the private sector, achieve typical gross transmission rates of 14 Mbit / s (Homeplug), 85 Mbit / s (Homeplug Turbo), 200 Mbit / s (Homeplug AV), 600 Mbit / s (IEEE 1901) and 1200 Mbit / s. The maximum range of home plug adapters on power lines is 300 meters. The standards Homeplug AV (200 Mbit / s) and IEEE 1901 (600 Mbit / s) are compatible with each other.

The low-voltage networks used are often three-phase networks with three outer conductors , a neutral conductor and a protective conductor, whereby the outer conductors (phases) are usually distributed across different areas within residential units. PowerLAN uses the wire pair phase / neutral conductor and recently also the protective conductor. Depending on other factors, such as line length, attenuation and possibly sources of interference, the data modulated onto the power line via PowerLAN is available at least on circuits of this phase within the residential unit. However, since the transmission takes place in the high-frequency range, it may a. through parallel cables for crosstalk , whereby the signals are also available in other conductors. This is accompanied by an attenuation of the signal strength, which is reflected in a reduced range and a lower transmission bandwidth. Phase couplers can be used for a desired, as undamped as possible signal bridging between two circuits .

hardware

The transmission is technically implemented with the help of adapters that are connected to the power supply on the one hand and to a device to be networked via a built-in Ethernet connection on the other (e.g. a PC, a printer, a game console or a webcam ). There are different designs according to different PowerLAN standards from various manufacturers, for example as an adapter or in combination with a WLAN access point . For professional use, more powerful devices are also available that provide transmission options via other media (e.g. coax or twisted pair lines ) as well as functions for data prioritization and hierarchical network topologies .

PowerLAN bridges can only communicate if they are on the same line conductor . To enable communication via different external conductors, PowerLAN hubs also exist . B. be attached to a mounting rail in a group distributor. There are also phase couplers that connect the outer conductors for the carrier signals. For some time now, powerline adapters with integrated PoE have also been on the market, which then control the PoE end devices connected behind them with data and power via the powerline carrier signal.

Network topologies

PowerLAN networks in the private sector usually have a peer-to-peer - network topology , i. In other words, each adapter communicates with each other on an equal basis, without any particular hierarchy. In order to be able to better control the data transmission and optimize the bandwidth distribution, some PowerLAN standards now assign the role of a central coordinator (CCo) to a specific adapter . This synchronizes the data traffic and dynamically divides the available total bandwidth among all participants in the network.

PowerLAN modems for professional use often also support a master-slave network architecture. An adapter (master) controls the entire data traffic of the stations (slaves) connected to it. The advantage of this topology is the encapsulation of the individual end devices connected to the slave adapters (peer-to-peer isolation). This prevents third parties from accidentally gaining access to them, e.g. B. when networking a hotel via coax and power lines.

particularities

Interference

Due to the high-frequency transmission, a PowerLAN can cause interference to other services in the same frequency band , which manufacturers of corresponding adapters counter by adapting the transmission power . Since the data is freely distributed within the transmission range of a PowerLAN (comparable to the availability of data via radio with WLANs), data security must be guaranteed with the help of encryption methods.

As a PowerLAN network works as a carrier frequency system, the conductors act like antennas that radiate the high-frequency signal. In principle, radio services, such as taxi radio , amateur radio or shortwave radio, can therefore be disrupted in the respective frequency band . In the private sector, PowerLANs often consist of only a few (<10) participants with a total range of less than 300 meters. Therefore, the signal levels of modern adapters are very small (significantly lower than, for example, a mobile phone , in a WLAN or with Bluetooth ). In addition, notch filters are used to reduce or completely suppress the transmission power in PowerLANs in certain frequency ranges in order to avoid influencing other known services. In order for PowerLAN adapters to be sold and operated in the European Union , they must also be CE-compliant .

In addition, the common PowerLAN procedures - like VDSL2 - work in the HF range . If the PowerLAN system is operated in the immediate vicinity of the DSL modem (as is often the case) , this can result in the DSL connection being broken.

Attenuation effects and interference

In contrast to networking via the widespread Ethernet, where the data throughput remains consistently high within the maximum line length of 100 meters per segment, the maximum transmission power in the PowerLAN depends on attenuation effects and interference that can negatively affect the range and transmission performance. The signal is attenuated via the length of the power line used for data transmission, the number of adapters in the PowerLAN and components or parts on the way from the transmitter to the receiver. These include cable connections (e.g. junction boxes), switches in multiple sockets, surge protection filters , but above all residual current circuit breakers and electricity meters . A higher attenuation leads to a lower bandwidth available for data transmission. Too much attenuation can prevent PowerLAN adapters from being able to exchange data with one another at all.

In addition, certain components or devices can interfere with a PowerLAN from the outside, e.g. B. by dimmers , ballasts or power supplies, drills, vacuum cleaners, etc. Although modern adapters use error correction methods to counter such interference, the data throughput still suffers in these cases.

Data security in the company

Within the maximum transmission range of a PowerLAN, the data modulated onto the lines is freely distributed in the power grid, i.e. This means that they can be received at any socket with the help of an appropriate adapter. Because of the crosstalk described or the coupling of several phases, the transmission signal can still be received outside of your own home, so that unauthorized third parties could possibly gain access to your own network. This problem also occurs with wireless networks (WLANs in which the data can generally be received via radio within the transmission range).

In order to restrict access to a PowerLAN and to prevent unwanted eavesdropping on the transmitted data, they can be encrypted with a password . Only adapters with the same password can then still communicate with each other. A PowerLAN must be set up accordingly once. While the DESpro process was used for data encryption with older adapters , more modern modems use more advanced cryptosystems, such as AES with 128 bits.

Theoretical and effective transfer rates

The theoretical data transfer rate of a network is seldom reached in practice. This depends first of all on the number of participants and the amount of data transmitted simultaneously by them, i. that is, the total bandwidth is shared between all devices in the network. However, depending on the transmission method and medium, there are other parameters that can be held responsible, such as coding and error correction methods, but also a possible dependence on the transmission power as well as possible interference. Even with modern WLAN transmission methods, a significantly lower net throughput can be observed in practice. The following table shows the various theoretical data transmission rates compared to the actually achievable throughput rates:

Procedure Gross throughput [Mbit / s] Net throughput [Mbit / s]
Fast Ethernet 0100 094.93 (data rate via TCP / IP)
Homeplug Turbo 0085 034
Homeplug AV 0200 090
Homeplug AV / IEEE 1901 0600 260
Homeplug AV2 / IEEE 1901 1200 350

Standardization and Compatibility

Since there has not yet been any official standardization of the procedures for data transmission via the low-voltage network, several proprietary, manufacturer-driven concepts have emerged over time, some of which are incompatible with one another: ITU G.hn (successor to DS2 from the Spanish manufacturer of the same name), IEEE 1901 ( Merger of Panasonic AV and Homeplug ). Homeplug (AV) / IEEE 1901 is particularly widespread in private households.

Procedure Link rate [Mbit / s] Frequency range [MHz]
Home plug 14th 4-20
Homeplug Turbo 85 4-20
Homeplug AV 200 2-30
DS2 AV 200 2-30
Homeplug AV / IEEE 1901 600 2-68
Homeplug AV2 / IEEE 1901 1500 30-68

An IEEE working group has been dealing with the standardization of PowerLAN for several years. After some setbacks, a proposal in the form of a combined Panasonic / home plug concept was made in October 2007, which was adopted in December 2008. In February 2009 technical sub-groups were formed and testing began. In July 2009, a first draft version of the IEEE P1901 standard was presented, which was published in January 2010. After further refinements were made in the course of 2010, the new standard was adopted on September 30, 2010 and finally published on December 30, 2010. Products based on the standard have been available on the market since the beginning of 2011. These are compatible with the HomePlug AV standard and offer a theoretical connection rate of 500 Mbit / s. HomePlug AV 2 has been available as a further standard since January 2012. Similar to the G.hn standard, this also uses MIMO technology, promises, at least theoretically, 1.5 Gbit / s and is compatible with Home Plug AV / IEEE 1901.

Parallel to the IEEE standard developed International Telecommunication Union (ITU) has its own standard called G.hn . This takes into account the data transmission via conventional, already existing power, telephone, network and cable television lines at a speed of up to 1 Gbit / s. This procedure is also known as the “homegrid standard”. The standardization process was completed in June 2010. Chips that work according to this standard are already available. The manufacturer Devolo presented commercially available products with the G.hn standard under the brand name Magic at the 2018 International Consumer Electronics Fair .

Individual evidence

  1. ↑ Powerline. In: heise.de. Retrieved February 14, 2015 .
  2. ↑ Powerline basics: network over the power line; Secure WLAN alternative. In: chip.de. 2015, accessed February 14, 2015 .
  3. ↑ Internet via power line: current powerline adapters being tested; Scope of services, installation, problems. In: netzwelt.de. Retrieved February 14, 2015 .
  4. ↑ dLAN registered trademark of Devolo. Retrieved May 5, 2018 .
  5. ↑ Powerline adapter for 2000 Mbit / s gross. In: Heise online . January 5, 2017. Retrieved December 19, 2017 .
  6. ↑ How does a powerline adapter work. In: SignalBoost.de. Retrieved June 20, 2015 .
  7. ↑ http://www.computerwoche.de/a/vernetzung-ueber-die-stromleitung-das-muessen-sie-wissen,3090783,2
  8. ↑ Powerline: a low-radiation WLAN alternative? - Article on the pros and cons of PowerLAN - Retrieved August 15, 2013
  9. ↑ Christof Windeck: Create a clear path . In: c't . No. 22 , 2010, p. 107–109 ( paid online version ).
  10. ↑ Marco Dettweiler: Through the power grid into the Internet. In: Frankfurter Allgemeine Zeitung . December 6, 2013, accessed December 6, 2013 .
  11. ↑ golem.de accessed on August 30, 2019
  12. ^ Marius Strobl: Standardization of Powerline Communication by IEEE and ITU-T . GRIN Publishing, Munich 2013, ISBN 978-3-656-49752-3 ( grin.com ).
  13. ↑ No agreement on the home network standard in the IEEE . Tom's Network Guide. July 25, 2008. Archived from the original on January 22, 2010. Retrieved on March 11, 2011.
  14. ↑ Megan Novak: HomePlug / Panasonic Merged Proposal Takes the First Step in Becoming a Worldwide Standard through the Efforts of the IEEE P1901 Work Group. (No longer available online.) In: www.homeplug.org . October 30, 2007, archived from the original on September 27, 2013 ; accessed on October 22, 2010 (English).
  15. ↑ IEEE Confirms Baseline for Broadband-Over-Power Line Standard ( Memento from June 2, 2010 in the Internet Archive ), IEEE
  16. ^ IEEE 1901 Draft Standard Announcement ( Memento of February 17, 2010 in the Internet Archive )
  17. ↑ IEEE Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications . IEEE Standards Association, December 30, 2010, ISBN 978-0-7381-6472-4 , doi : 10.1109 / IEEESTD.2010.5678772 .
  18. ↑ HomePlug® Powerline Alliance Announces AV2 Specification for Next-Generation Broadband Speeds over Powerline Wires . (PDF; 1.2 MB)
  19. ↑ United Nations ITU-T's G.hn Approved as Global Standard for Wired Home Networking . HomeGrid press release of June 11, 2010
  20. ↑ Oliver Nickel: Devolo's Powerline adapters manage 2,400 Mbit / s gross. In: Golem. Golem Media GmbH, August 17, 2018, accessed on October 15, 2018 .