s-net®

Wireless IoT

s-net® - The technical solution

What are the key facts about s-net®?

s-net® offers an extremely energy-efficient, wireless solution for networking and localization and belongs to the category of Low Throughput Networks (LTN) with multi-hop communication. The following features distinguish s-net®:

Bidirectional multi-hop communication

Due to the continuous, bidirectional accessibility of all nodes and the forwarding of data via intermediate nodes, the s-net® technology enables the supply of radio nodes via battery. With multi-hop communication, network coverage is not limited to the range of one radio node, but rather can extend to buildings or areas

Dynamic structure and self-organization

s-net® offers an independent and temporal organization of all radio nodes participating in the network. This self-organization occurs decentral at the place of communication and thus supports mobile nodes. The dynamic structure and the self-organization of the meshed network ensure a low configuration and maintenance effort as well as high robustness.

Energy-saving radio communication

s-net® realizes an extremely low power consumption of the radio nodes through time synchronization of the network and time-division multiplex communication. This supports battery operation of all radio nodes. For example, if data is transmitted only at hourly intervals, an average power consumption of less than 50 µA can be achieved with s-net®.

Functional principle of s-net® technology

s-net® Funktionsprinzip
© Fraunhofer IIS

The s-net® radio network participants are organized into layer groups. The participants of layer group 1 communicate directly with the master; starting with layer group 2, communication with the master takes place via routers.

Network organization

The communication protocol of s-net® describes three different communication roles: Master, router and end node (see figure).

The master specifies the clock of the synchronous protocol for all other subscribers and defines with its previously configured parameters the communication properties of the network. Router nodes and end nodes can connect to the master node in a self-organizing way to exchange data with it. Router nodes have the ability to provide these network characteristics and the synchronous clock for other subscribers outside the direct radio range of the master. The end nodes do not forward data and are often used as mobile subscriber.

In addition to the communication along the paths specified by the tree structure, s-net® also offers meshed communication possibilities to neighboring subscribers without a detour through the master.

s-net mit zeitlich koordinierten Zugriffsverfahren
© Fraunhofer IIS

s-net® enables reduced energy consumption in time-coordinated access procedures (TDMA) with shorter idle-listening states.

s-net® Zeitliche Organisation
© Fraunhofer IIS

The radio transmission in s-net® only takes place in the three active time ranges Beacon, Data and Meshed Data. The remaining time the radio transceiver can be off state to save energy.

Temporal organization

In contrast to comparable wireless technologies, the idle listening times have been reduced thru s-net® by introducing short activity cycles for sending and receiving (see Figure 1).

Three active time domains are defined in a periodically repeating timeframe for data transmission (see Figure 2). Wireless activities only take place in these time domains. For the rest of the timeframe the radio node can be asleep and thereby save power.

The first active time range is called Beacon domain. Within the Beacon domain, s-net® arranges the beacons of the master and all routers in a temporal collision-free manner. For the transfer of data in the direction of the master, the second active time range is defined as the Data domain. In this period, masters and all routers have their own collision-free time ranges for receiving data from their respective successors.

The third active time domain is the Meshed Data domain. In this time domain the master and each router node periodically transmits information about the network organization additionally to the application data for neighbors. This information are used for the self-organization of the network

.

Hardware reference designs and standard modules of s-net®

Many transceiver ICs can be used for s-net®, thus it is possible to utilize it in different frequency bands. So far, systems for the 433 MHz, 868 MHz and 2.4 GHz bands have been implemented. They allow a fast implementation for feasibility studies and can usually be insert unchanged. Furthermore, they provide a solid starting point for individual product developments, because the system properties, sensors, interfaces or design can be adjusted for customer-specific requirements.