1 Introduction
This document describes features, parameters and setting possibilities of the NB-SI2 module, which is used for
reading of either consumption meters with pulse output (water meters, electrometers, gas-meters. . . ), or two-state
sensors (e.g. door contacts, flood detectors, fire detectors, electronic seals...etc.) and for radio-transmission of the
data from connected meters/sensors to the superior remote reading system via data services of NB-IoT operator.
1.1 NB-IoT mobile data services
Mobile data services NB-IoT are global data services provided by some operators of GSM services. The
services are focused on the communication with a huge quantity of devices, that transfer only an extremely limited
volume of data. Networks with such purpose and features are commonly labeled as ”Internet of Things”, or by its
acronym ”IoT”. NB-IoT (”Narrow Band Internet of Things”) is an open standard developed by 3GPP organization
(3rd Generation Partnership Project) which is concerned with standardization in the GSM network development.
NB-IoT is a cellular technology based on the LTE, that was developed specially for wireless communication with
terminals of IoT category, that produces only limited volume of data, but they are miniature, inexpensive, with
a very low energy consumption and they are commonly installed in the places with high demands on the signal
coverage. Typical example of such device is a reading module of the water/gas/electro-meter installed in the
basement without electricity, that should be able to run reliably many years on the internal battery even in weak
signal conditions, where other services fail.
NB-IoT technology maximally utilizes technological infrastructure of LTE data services in licensed radio band.
Combination of narrow frequency band and the most advanced modulation techniques enable increasing of receiver
sensibility to the -135 dBm level, so that an existing infrastructure of mobile operator provides global coverage
with high signal penetration even in build-up urban areas. Thus, the service is available in the places, where IoT
category devices are typically installed - in shafts, distribution boards and cellars.
Terminal devices are identified in the network by standard SIM of GSM operator. Global system of SIM evidence and
single communication standard enable providing of international services (roaming). Bi-directional communication
is carried by standard Internet protocol with UDP transport layer. Messages are transferred from the GSM operator
network to the IoT-terminal operator through the designated data gateway (Access Point - AP) either to public
Internet, or to operator’s private IP network (i.e. same way as any similar mobile data services). Addressing and
routing details depend on the network configuration and policy of particular GSM operator. Typical example of
addressing and routing is a solution, when the GSM network automatically assigns private IP addresses to IoT
terminals, IP-packets with messages are routed through the private IP network to a single Access Point, where
they are re-addressed and resend through a single pre-arranged public IP-address to the public Internet. The IoT
terminal assigns packets by target server public IP-address, that is preset in its configuration. Target system can
identify original source of the message by using of device unique identifier (IMEI), which is a requisite part of the
message content.
1.2 Module usage
The NB-SI2 module can be used either for remote reading of one or two consumption meters with pulse output, or
for monitoring of up to two two-state sensors. It is possible to combine both type of usage.
When using for remote reading of consumption meters (water meters, gas meters, electro-meters...), up to
two meters with standard pulse (”SI”) output can be connected to the module. The meters can be of different
kind, with different quantities and units and with different conversion rates. The module continuously registers
incoming pulses (generated by meters) into its internal counters, with using of preconfigured multipliers/divisors
converts current status of each counter into the required output value and broadcasts info-messages with current
statuses of connected meters in form of radio-messages of NB-IoT service provided by GSM operator (hereinafter
”INFO-message”).
When using for remote monitoring of sensor statuses (door contacts, flood detectors, fire detectors, electronic
seals..), up to two two-state sensors with ”off/on” (”0/1”) outputs can be connected to the module. The sensors
can be of different kind, with different type of output and different logic of signaling. The module continuously
monitors status of each sensor and in case of change sends immediately alarm message (message of ”TRAP” type
) to the superior system. The module stores status of the input into internal counter and transmits information
about the current status of connected sensors in regular INFO-messages.
Content of INFO-messages is configurable, it could contain current statuses of connected meters/sensors, current
statuses of embedded temperature/humidity sensors, as well as previously measured ”historical” readings stored in
NB-SI2 1
