1 Introduction
This document describes features, parameters and setting possibilities of the WB169-RFE-R communication gate-
way, which is used for receiving of radio messages from the devices for remote reading of consumption meters
working in the communication system Wireless M-BUS (hereinafter referred as WMBUS) in the 169 MHz band and
for transmitting of these messages over a standard IP network (Internet) to a central collecting system.
1.1 Wireless M-BUS Communication Protocol
Wireless M-BUS is the communications protocol described by international standards EN 13757-4 (physical and
link layer) and EN 13757-3 (application layer), which is intended primarily for radio transmission of remote reading
values from consumption meters and sensors. Protocol Wireless M-BUS (hereinafter ”WMBUS”) is based on a
standard M-BUS definition (uses the same application layer as M-BUS standard), but is adapted for data transfer
via radio signals.
Communications via WMBUS protocol works in Master-Slave mode, where ”Master” is a collecting data device,
”Slave“ is a providing data device. Slave device could be integrated or external radio module transmitting data
from the meter/sensor. The communications protocol WMBUS defines several communication modes (simplex or
duplex). If working in simplex mode a ”Slave” device only transmits messages to ”Master” that these messages
receives. If working in ”bidirectional” mode, it is possible to use a back channel from ”Master” device to ”Slave”
device for ”Request” type of messages, that can contain e.g. request for the change of slave’s configuration.
Wireless M-BUS communications protocol partially supports repeating of the messages. If receiving from some
”Slave” device is not possible because of the low level of radio signal, the messages can be re-transmitted (repeated)
by appointed element of the radio network (repeater or slave with such functionality). Each repeated message is
marked as ”repeated message” so as not to be repeated again.
1.2 Module usage
The WB169-RFE-R module is intended for data transfer from the consumption meters (water meters, gas meters,
electricity meters, calorimeters) and a central computer application that receives and processes the data. The
module receives radio messages coded according to the Wireless M-BUS EN 13757-3 and EN 13757-4 standard for
the 169 MHz band, checks their correctness, encodes (”repacks”) them into IP/UDP frames and sends them to the
configured IP address and a central application port number. Inside the IP/UDP frames the data are coded by
using of Softlink’s proprietary ”NEP” protocol, so that the WB169-RFE-R module can be used for those central
applications only, which use ”NEP” coding system.
If the WB169-RFE-R module is setup for working in the N2 bidirectional communication mode, it could
transmit Wireless M-BUS messages of ”Request” type addressed to any subordinate module supporting N2 mode.
These messages can be used for remote changing of parameters of the subordinate ”Slave” device. Broadcasting of the
back-channel message for a particular ”Slave” device is under way during 500 ms long back-channel communication
window that opens immediately after transmitting of ”User Data” message from the device. During this time period
the ”Slave” activates its receiver so as to be able to receive a ”Request” message (if transmitted). Receiving of the
back-channel message is confirmed by ”Acknowledgment” type of message.
Management of ”Request” type of messages must be implemented into the central application software. These
messages addressed to the particular ”Slave” are transferred to the WB169-RFE-R module through the IP/UDP
protocol with using of ”NEP” coding. WB169-RFE-R module stores the ”Request” messages (that contain also
the lifetime period of each message) into its memory tables and after receiving of next ”User Data” message
from the ”Slave” device transmits the back-channel message within the communication window. If the message
is confirmed by receiving of ”ACK” message from the ”Slave”, the message is removed from the WB169-RFE-R
memory table. If ”ACK” message does not come, ”Request” is sent again during next window until its lifetime
period is elapsed. WB169-RFE-R module can keep just one message in the memory table, so if the module receives
another ”Request” message from the central application, stored message is replaced by new one so that only the
last message is transferred to the ”Slave”. ”Request” messages are coded by using of common M-Bus principles and
the coding system must be implemented in the central application as well as in the ”Slave” device in a specular
manner. The WB169-RFE-R module performs just transferring of the messages.
The basis of the module is a microcomputer with the Linux operating system, which is equipped with one 10/100
Mb/s Ethernet communication port, four USB (Universal Serial Bus) ports and one COM/CMOS config-
uration port. Communication ports are used for the following purposes:
•10/100 Mb/s Ethernet port – the main communication port intended for communication with the central
application over IP-network;
WB169-RFE-R (WB169-RFG-R, WB169-RFW-R) 1
