WIRELESS CONNECTIVITY & SENSORS
ANR001 - Metis-II Repeater Mode
1 Introduction
Starting with firmware version 2.8.0 the Metis-II include a feature to enable receiving, buffering,
delaying and forwarding radio frames better known as single-hop unidirectional repeater func-
tionality.
WE order code Former order code Description
260702118300x AMB8626-M-TR 868 MHz wM-BUS module 14dBm, T&R,
Firmware 2.7.0
2607021183010 AMB8626-M-RP-TR 868 MHz wM-BUS module 14dBm, T&R,
Firmware 2.8.0
Table 1: Metis-II Ordering information
The European Standard EN13757 and the OMS Group Specification give information on how
a single-hop unidirectional repeater shall be implemented and what radio frames shall be sup-
ported by the repeater.
Our implementation will enable the repeater mode only on a very specific configuration set of
the wM-Bus module as introduced later.
Using the repeater mode requires careful attention of the user regarding local
regulatory requirements. Especially the duty cycle requirements need to be
adhered to.
For example by realizing a suiting host implementation in the user’s end system
that implements duty cycle restriction.
2 Motivation
By means of the repeater mode a module or USB stick can be utilized to enhance the effec-
tive radio range of wireless M-BUS meters within the repeater’s range. This will happen for
frames that follow EN13757-3:2013 and EN13757-4:2013 as well as OMS Specification Vol-
ume 2 Generation 4 V4.1.2. In essence this applies to all wM-BUS frames that have a hop
counter field at a location described in the standard and also have a C-Field of either SND-NR
or SND-IR, which are only to be used in direction meter to other (uplink).
As the size of the hop counter field is limited to 1 bit it is not possible to provide multiple hops
in a standard compliant way. Therefore the hop counter must be ’0’ in the received frame and
will be set to ’1’ by the repeater to indicate that the message was repeated.
A frame already having the hop counter ’1’ when being received by a repeater will be discarded.
To be able to find the hop counter inside a frame the repeater parses and checks parts of the
radio frame upon reception. Currently the following frame structures and conditions are imple-
mented in the firmware, listed in the order of priority they will be tested and applied:
3
Version 1.4, July 2023 www.we-online.com/wcs
