What is DLMS and how it would benefit of NR+? - Wirepas

What is DLMS and how it would benefit of NR+?

Author:
Jani Vehkalahti

The DLMS User Association and Wirepas will collaborate to define a reliable and secure way to support the DLMS protocol over NR+ mesh networks. A new profile is key to providing reliability and interoperability in future implementations of NR+ over DLMS and mixed networks, for example, DLMS over the cellular. 

What is DLMS?

DLMS is the suite of standards developed and maintained by the DLMS User Association. First published in 1999, it was adopted in 2002 by the International Electrotechnical Commission (IEC) and the European Committee for Standardization (CEN) organizations in its series of IEC 62056 standards for smart metering. Recently it was adopted in 2019 by the ANSI, the American National Standard Institute. It has been widely adopted, with over several hundred million meters worldwide, using the DLMS/Companion Specification for Energy Metering (COSEM) standard.

DLMS supports various wired and wireless communication standards, including cellular, Wi-SUN, PLC, Zigbee, WMBus, LoRa, and Prime-PLC. Its flexibility to offer an application layer independent from the media layer enables utilities and end users to have the same application over any one communication technology or a mix of many.

Why add DECT NR+ to the list of DLMS communication profiles? 

Increasing features of advanced metering infrastructure (AMI) demand more performance from communication technology. There’s also the trend of favoring wireless communication in large-scale electricity smart metering deployments worldwide. Reading meters every 15 minutes is becoming a minimum requirement everywhere. This means that over 300 bytes of data are typically transferred per meter to a cloud every 15 minutes.  

Especially in emerging countries, we see increasing downlink traffic due to the prepayment meters. Why? In developing countries, consumers load very small prepayments, as small as 5 Indian rupees ($0.06). After the balance is used, the meter turns off the electricity. Users expect that after loading their next 5 rupees, the meters will turn on immediately. This means that the network must be capable of handling thousands of simultaneous events with low latencies in highly populated city areas.   

Firmware and software updates over the air (OTA) must be sufficient at any network scale. Normally there are two firmware images to be updated: meter firmware and network interface card (NIC) firmware. NIC might also require an additional update of application processor software. Typically, smart meter firmware is between 512 kB and 1 MB. NIC card firmware usually varies from less than 128 kB to over 1 MB. 

Emerging countries do have an extreme density of people in the city area. It is crucial that connectivity technology supports a high density of devices and support the coexistence of other networks to provide reliability of communication.  

DECT NR+ was developed and standardized to meet all requirements mentioned above. Throughput of the network, latencies, OTA, and co-existence of wireless networks drove NR+ also to become part of 5G defined by ITU.  

Technologies like LTE-M can also meet requirements when there is sufficient cellular coverage. Especially metering rooms in urban areas have the challenge of connecting hundreds and even over a thousand meters in the basement of the building.  

Non-router devices like water and gas meters can enjoy low-power NR+ profiles, reaching over 10 years of battery life with a smaller battery than any cellular technology. Even smaller than with LoRa when comparing the same data profile (data loads and frequency intervals).

Why is NR+ over DLMS important for smart metering?  

With DLMS over NR+ profile, utilities can benefit from the security and all mechanisms of DLMS with bidirectional support to push messages and get commands, and moreover, from the security of network transmissions thanks to NR+. Together new IPv6-based profile will provide superior reliability and interoperability between DLMS meters. 

The first profile uses an international non-licensed 1900 MHz spectrum dedicated to DECT and NR+ devices. The frequency band does allow 23 dBm to transmit power without duty-cycle limitations. The coexistence of wireless networks is handled by implementing the standard, which defines listening before talking, automatic transmit power, and HARQ, to mention a few. The physical layer requirements of the NR+ are a subset of cellular LTE-M radio hardware make its link budget superior. 

So here we are, trying to combine two great things.

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