Wireless reading

Wireless meter reading over wM-Bus

wM-Bus is the wireless counterpart of M-Bus. The meter broadcasts its data at intervals and a collector picks the telegrams up. In existing buildings where cable cannot be pulled, it is the most common route to remote reading.

At a glance

Standard: EN 13757-4
Frequency: 868 MHz commonly; 169 MHz for longer range
Modes: S, T and C modes; one-way and two-way variants
Security: AES-based telegram encryption; key stored per meter

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What is wM-Bus?

wM-Bus (wireless M-Bus) is wireless meter communication standardised in EN 13757-4. In Europe the 868 MHz licence-free band is the common choice; some deployments use 169 MHz where longer range matters more than data rate.

It works differently from wired M-Bus: the meter does not wait to be asked. It broadcasts a short telegram on its own schedule and a collector or receiver listens and records. Because the meter spends most of its life asleep, battery life can exceed a decade.

Telegrams can be encrypted. For meters that broadcast encrypted data, the device key must be known to the system — without it the telegram cannot be decoded. NovuSoft keeps the key on the meter record and decodes automatically.

How it works

Reading with wM-Bus, step by step

The path from installation to an index landing in the panel.

The meter broadcasts
Depending on its mode, the meter transmits a short telegram every few seconds or minutes. The telegram carries the meter identity, index and status.
A collector receives it
A collector placed inside the building listens for every meter within range. The same meter may be heard many times a day; the system keeps the most recent valid reading.
The telegram is decoded
For encrypted broadcasts the device key stored on the meter record is used. The decoded data is split into index, status and error fields.
Data reaches the panel
The collector forwards what it has gathered over the central connection; indexes are archived and become available to the billing engine.
Coverage is monitored
Meters not heard for a long time are listed. Signal level and last-heard time reveal coverage problems or a dying battery early.

Technical summary

Standard: EN 13757-4
Frequency: 868 MHz commonly; 169 MHz for longer range
Modes: S, T and C modes; one-way and two-way variants
Security: AES-based telegram encryption; key stored per meter
Transmission: Meter broadcasts on its own; the collector listens
Battery life: Device dependent; deployments beyond ten years are common
Range: Depends on structure; concrete and shafts reduce it sharply

Choosing

When is wM-Bus the right choice?

There is no single right path for every building. These two lists are the criteria we apply during a site survey.

Good fit

Existing buildings where cable cannot be pulled
Projects avoiding renovation cost and disruption
Buildings with scattered meter positions
Deployments that need to go live quickly

Poor fit

Points where meters sit inside thick reinforced concrete or metal shafts and coverage struggles
Operators unwilling to manage a battery replacement schedule

In NovuSoft

How wM-Bus reading is managed in the panel

Supporting a protocol is not enough; what the data means and what happens when a meter cannot be read must be defined too.

Encrypted telegram decoding

The device key is held in the inventory; encrypted broadcasts are decoded automatically and the index goes straight into the archive.

Signal and last-heard tracking

Signal level and the time a meter was last heard are tracked, so a coverage problem or a dying battery surfaces well before period close.

One panel with wired meters

Some blocks can run wired M-Bus while others run wM-Bus in the same project. Both write to the same archive and enter the same billing engine.

Unknown device alerts

Devices heard in range but not defined in the system are collected in a separate list — broadcasts from a neighbouring building never mix into your project data.

Frequently asked questions

Questions about wM-Bus

What is the difference between wM-Bus and M-Bus?

Both share the same data model; the difference is the physical layer. M-Bus runs on a two-wire cable and meters answer when asked. wM-Bus is wireless and the meter broadcasts on its own. If cabling is possible M-Bus is more stable; if not, wM-Bus is far more practical.

Is wireless reading secure?

Telegrams can be protected with AES-based encryption; without the key the content cannot be decoded. NovuSoft stores the key on the meter record and decodes server side.

Will we know when a meter battery runs out?

Yes. The battery status field in the telegram is read, and meters that have not been heard for a long time are listed separately. Both signals let you plan replacement rather than discover it at period close.

Will we also read the neighbouring building's meters?

Broadcasts in range may be heard, but only meters defined in your project are processed. Undefined devices appear in a separate list and never enter the calculation.