IoT Radio Protocols for Smart Metering: WM-BUS & LoRa

While new energy needs have emerged, with an increased demand of 50 percent since the 1990s and with a further 30 percent increase expected by 2040, new technologies are providing improved solutions for dealing with energy management. These new telecommunications technologies, therefore, represent a strategic development lever for energy stakeholders because they let them create an interconnected ecosystem, with machine-to-machine (M2M) devices, such as sensors and data concentrators, at its core.

M2M devices are the central link in the energy value chain and must communicate in the appropriate telecommunications protocol. This raises the question of the different technical solutions used for the transmission of information from field equipment. In the case of water and gas applications, wireless technologies are normally used.

We will focus on the following technologies for smart meter reading: Wireless M-Bus, LoRa and LoRaWAN.

Wireless M-Bus Protocol

The Wireless M-Bus (WM-Bus) point-to-point radio protocol, using either 169Mhz or 868Mhz, is traditionally used in smart metering and smart building, particularly for its conditional bidirectional qualities and its relatively moderate consumption.

The WM-Bus is a standardized protocol. This is a fundamental point when it comes to choosing a solution as it ensures compatibility between all the manufacturers.

The Wireless Mbus protocol is based on a private, non-operated network. In order to operate, a Wireless Mbus network requires concentrators (or gateways) that allow connection between all the sensors and a remote information system.

The Wireless Mbus protocol is based on two frequency bands: 868Mhz and 169Mhz. These are both free bands that can be shared with other applications. Regulations have been put in place to ensure equitable sharing. In Europe these regulations are enforced by ARCEP (the French telecommunications and postal regulatory body) and deal with frequency channels, transmission power and bandwidth occupancy rate (duty cycle).

868Mhz is traditionally the band most used. In free field the distances that can be potentially covered between a sensor and the concentrator are of the order of 1 km. Using an 868Mhz radio network inside a building is more complex. Internal partitions can prove a significant obstacle to wave transmission and may require the use of repeaters.

The 169Mhz band has recently been used in Smart Metering applications. The French gas distribution company, GrDF's Gazpar project is one of the first 169Mhz smart metering networks. The 169Mhz frequency offers several advantages. The lower the frequency used, the greater the wave penetration. Hence, inside a building, the distance covered, or the number of floors traversed, is greater at 169Mhz than at 868Mhz.

LoRa Radio Protocol as a Solution

For its part, the LoRa radio protocol, a Low Power Wide Range (LPWA) solution much favored in the industry and energy sectors, is an 868Mhz radio protocol that only describes the physical layer of a device. It is, therefore, necessary to place one or more application layer above this radio layer. With LoRa it is possible to gain 30dB compared to conventional WM-Bus protocols in frequency shifting key (FSK) modulation, giving signals that are 10,000 times smaller. LoRa allows transmission on different channels, thus improving frequency band occupancy time.

The private network and the operated network are the two types of networks that use LoRa or LoRaWAN.

The private network requires its own data concentrators and its own LoRa networks. It is ideal in terms of security and use and can be installed anywhere.

The operated network does not require data concentrators or SIM cards because the operators offer base stations that gather directly from all the field devices.

The answer to the need for optimized, profitable and above all secure energy management, inside a building, for example, coul come from a proprietary solution where LoRa would represent the lower layer and Wireless M-Bus one or more application layers.

The endpoints would communicate in LoRa with the concentrator hub which would contain a LoRa physical layer and a WM-Bus application layer.

This combination of both the LoRa and the WM-Bus protocols could lead to a viable and sustainable solution for smart metering management.