Wireless M-Bus (EN 13757): The European Standard for Heat and Water Meter Wireless Communication

Wireless M-Bus is the dominant wireless communication standard for heat meters, water meters, and gas meters in Europe. If you are deploying or integrating walk-by, drive-by, or fixed-network AMR in the EU, you will encounter it. Here is everything you need to know.

What is M-Bus?

M-Bus (Meter Bus) was originally defined as a wired protocol for reading utility meters over a two-wire bus — defined in EN 13757-2. Wireless M-Bus (wM-Bus) is the radio extension defined in EN 13757-4, operating in the 868 MHz (Europe) and 433 MHz ISM bands.

The standard is maintained by the OMS Group (Open Metering System) and the M-Bus User Group, which publish the OMS specification as a profile on top of EN 13757.

EN 13757 Series Structure

Part	Title	Relevance
EN 13757-1	Data exchange	General data exchange principles
EN 13757-2	Wired M-Bus	Physical + data link layer for wired meter bus
EN 13757-3	Dedicated application layer	Data structure, DIFs/VIFs, telegram format
EN 13757-4	Wireless meter readout	Radio layer: frequencies, modes, telegram structure
EN 13757-5	Relay function	Repeater/relay devices in wM-Bus networks
EN 13757-6	Local bus for meter readout (M-Bus)	Local bus extension
EN 13757-7	Transport and security services	Encryption, authentication, key management

Wireless M-Bus Modes

The mode defines the frequency, modulation, data rate, and communication pattern:

Mode	Frequency	Data Rate	Use Case
T1	868.95 MHz	100 kbps	Meter → collector, unidirectional. Most common for drive-by and walk-by AMR. Fast telegrams, short on-air time.
T2	868.95 / 869.525 MHz	100 / 32.768 kbps	Bidirectional T-mode. Collector can acknowledge.
C1	868.95 MHz	100 kbps	Compact unidirectional. Similar to T1 but with different preamble — used by some newer meters.
C2	868.95 / 869.525 MHz	100 / 50 kbps	Compact bidirectional.
S1	868.3 MHz	32.768 kbps	Stationary unidirectional. Fixed-network installations. Longer range than T-mode.
S2	868.3 / 869.525 MHz	32.768 kbps	Stationary bidirectional.
N1/N2	169 MHz	2.4–4.8 kbps	Long-range, high penetration for underground/basement meters. ETSI 169 MHz band.
R2	868.33 MHz	4.8 kbps	Relay mode for repeaters.

Telegram Structure

A wM-Bus telegram is compact and field-efficient:

[L] [C] [M] [A] [CI] [Payload...]
 1    1   2   6    1     variable

L  = Length (total telegram length - 1)
C  = Control field (direction, function: SND-NR, SND-UD, REQ-UD1...)
M  = Manufacturer ID (2 bytes, encoded as 3-letter code)
A  = Address (6 bytes: ID 4 bytes + version 1 byte + device type 1 byte)
CI = Control Information (payload type: 0x78 = no header, 0x7A = short header...)

The payload uses DIF/VIF records (Data Information Field / Value Information Field) — a self-describing format that encodes both the data type and the physical quantity in each record.

OMS: The Interoperability Profile

The Open Metering System (OMS) specification builds on EN 13757 to define:

Mandatory telegram content for each meter type (heat, water, gas, electricity)
Encryption using AES-128 in CBC or CTR mode (Mode 5/7)
Key management procedures
Collector and concentrator requirements

OMS certification ensures that a meter from manufacturer A can be read by a collector from manufacturer B — the same interoperability promise that DLMS CTT provides for electricity meters.

Security: AES-128 Encryption Modes

Mode	Algorithm	Authentication	Notes
Mode 0	None	No	Legacy, do not use for new deployments
Mode 4	DES (obsolete)	No	Deprecated
Mode 5	AES-128 CBC	Via 2-byte CRC	Most widely deployed. Provides confidentiality. Weak authentication.
Mode 7	AES-128 CBC	Yes (8-byte MAC)	Recommended for new deployments. Strong authentication + encryption.
Mode 13	AES-128 GCM	Yes (full AEAD)	Strongest. Required by some national programmes (e.g. Netherlands DSMR P1).

Practical Deployment: Walk-By vs Fixed Network

Walk-by / Drive-by (T1/C1 mode): meter broadcasts a telegram every 8–64 seconds. A technician walks or drives past with a handheld or vehicle-mounted collector. Simple, low-cost, no fixed infrastructure. Suitable for quarterly reads.

Fixed network (S1/S2 or LoRa bridge): concentrators mounted on poles, buildings, or substations collect telegrams continuously. Enables daily or hourly reads. Many utilities use a LoRaWAN or NB-IoT backhaul to connect concentrators to the HES.

Key Vendors

Diehl Metering — leading wM-Bus module manufacturer, OMS-certified
Kamstrup — wM-Bus on MULTICAL heat meters and FLOWIQ water meters
Itron — wM-Bus in Cyble sensor series for gas and water
Landis+Gyr — wM-Bus modules for heat and water meters
Amber Wireless / Microchip — wM-Bus radio modules for OEM integration