Introduction
The digitalization of the energy supply requires powerful communication solutions in order to transmit consumption data securely and reliably. Two standards are particularly widespread in Europe: Local Metrological Network (LMN) as a wired solution and Wireless M-Bus (wM-Bus) as a wireless alternative. While LMN scores with a stable and secure connection, wM-Bus offers greater flexibility. But which technology is the better choice for modern smart metering infrastructures?
What is LMN? – The wired alternative for smart metering
The Local Metrological Network (LMN) is a wired communication solution that was specially developed for intelligent metering systems (iMSys) in Germany. It is used for the secure and robust transmission of consumption data between metering devices and the connected smart meter gateways. Communication takes place via the wired LMN protocol, which was specially developed for secure operation in smart metering systems.
Benefits of LMN
High reliability: Wired communication is less sensitive than wireless alternatives to external interference such as radio interference or electromagnetic fields.
No battery dependency: LMN devices can be supplied with power via the bus lines and are therefore battery-independent.
Scalability for larger networks: LMN enables the stable and simple connection of several meters via a bus structure.
Disadvantages of LMN:
High installation effort: Cabling often requires structural measures, especially in existing buildings. With existing RJ45 cabling with free cables, however, this problem can be solved with a suitable RJ45 extender.
Less flexible for retrofitting: If there is no existing infrastructure, retrofitting can be more expensive and complex than a wireless solution.
Potential differences between buildings: When connecting two buildings, potential differences can occur that cannot be compensated for by LMN cables.
wM-Bus – The flexible solution for smart metering
Wireless M-Bus (wM-Bus) is a radio technology for wireless meter communication. It uses license-free frequency bands (usually 868 MHz) and enables bidirectional data transmission between smart meters and a gateway.
wM-Bus is particularly suitable for retrofit solutions in existing buildings, as no new cables need to be laid. Radio communication offers a cost-effective alternative, particularly in apartment buildings or where meter locations are difficult to access.
Benefits of wM-Bus:
Simple installation: Ideal for retrofitting, as no cabling is required.
Flexibility: Radio modules can be easily connected to different meters and repositioned as required.
Disadvantages of wM-Bus:
Limited range and susceptibility to interference: Walls and other obstacles can affect signal quality.
Challenges with stability: Wireless signals are potentially more susceptible to interference than wired alternatives. Interference is also harder to find and fix.
Comparison: LMN vs wM-Bus – Which technology is better?
Although LMN generally requires more installation effort, it offers significantly more reliable and interference-free communication compared to wM-Bus. While wireless systems are susceptible to signal attenuation due to walls or electromagnetic interference, the wired LMN connection remains stable and ensures secure and continuous data transmission.
In terms of flexibility, however, the wM-Bus scores highly. Retrofitting a wireless system is easier and more cost-effective than retrofitting cabling, particularly in existing buildings or in installation locations that are difficult to access. However, anyone who prefers a low-maintenance solution with long-term stability should opt for LMN, as it does not require regular battery changes. With a suitable RJ45 extender, the existing network of network cables in existing buildings can also be used for wired data transport in the Local Metrological Network.
Conclusion: When is LMN the better choice?
LMN is particularly suitable for new buildings and larger infrastructures where stable and interference-free communication is required. Extended LMN technology is also required to use the existing network cable infrastructure. LMN is established as the standard for the connection between smart meter gateways and metering devices, particularly in the German smart metering rollout.
wM-Bus, on the other hand, is ideal for existing buildings where retrofitting cabling or the use of network cables would be too expensive or impractical.
Ultimately, the choice between LMN and wM-Bus depends on the structural conditions and long-term costs. Anyone looking for a low-maintenance and fail-safe solution is better off with LMN.
