How to set up an IoT network to get associated data from the sensor to the Cloud? – part IV

Thomas Steen Halkier – CEO of NeoCortec, and Zoltan Kiss – Head of R&D at Endrich Bauelemente Vertriebs

In this paper we conclude the discussion of the different possibilities to collect sensor data and get them into the Cloud using the E-IoT ecosystem, which has recently been using NeoCortec’s revolutionary NeoMesh protocol for having an ad-hoc, real low-power, sub-GHz mesh WLAN to collect data locally and gateway it to the Internet from a single access point.

NeoMesh – reliability and security

As we have already explained, NeoMesh offers the possibility to create a large wireless ad-hoc network with thousands of nodes, which are all battery-operated, all acting as routers, coordinators, and end-devices as single items, with no need of repeaters, while there is a redundancy in the signal path. Now it is time to talk about the reliability and the security aspects of this solution.

In the NeoMesh network, the exchange of payload data between nodes relies on local ACK/NACK, with package transfer retries in case of failure. The ACK/NACK employs CRC checking with a 32-bit checksum, ensuring a high probability of error-free received and acknowledged packages. NeoMesh also supports end-to-end acknowledgment, automatically notifying the source node upon successful delivery at the destination.

Strong encryption

To further enhance reliability, NeoMesh employs frequency hopping, spreading communication across the entire frequency band and avoiding heavily used channels, while also improving noise immunity. Reliability is not only a matter of ensuring that data is delivered to the destination, but it also implies that the correct data is delivered. CRC checking as previously discussed is good for making sure there are no bit errors, but it does not guarantee that payload data was not generated by a malicious source. Reliability and security are often mixed up when discussing networking, however they are fairly different properties.

Strong encryption is integral to NeoMesh, with data exchanged between nodes encrypted using industry standard AES128, and a challenge-response handshake implemented for fully acknowledged communication, preventing playback attacks, and ensuring secure payload data exchange.

Securing the communication link

NeoMesh has two strong features built into the core of the protocol stack which increase the reliability even further by securing the communication link:

• All data exchanged between nodes in the network, as well as the complete RF communication, are encrypted using industry standard AES128. The key for the AES, is the network key which is programmable by the system configurator and stored securely in each module;
  
  
• When using fully acknowledged communication between the source and the destination, there is an automatic challenge-response handshake implemented, which ensures that a destination node will only accept payload data from another node (source) if the data includes the correct response to a challenge given by the destination.

This challenge-response authentication is unique to NeoMesh and is handled completely seamless by the protocol stack. It prevents the so-called playback attacks where a malicious device records a previously sent payload package which may contain a certain control function like "unlock door" or any similar. The perpetrator later retransmits (plays back) the message which would unlock the door. With challenge response authentication this is not possible.

What kind of smart sensor devices are available as PoC products at the E-IoT family?

The ideal sensor device for point-to-point communication is the mini-E-IoT board by Endrich. It combines several sensors, such as temperature, humidity, acceleration, ambient light- and magnetic field sensors, with а gyroscope and а microphone. The built-in GNSS module offers outdoor localization services. The communication protocol being used is either a cellular NB-IoT/LTE-M (LPWA) or a 2G GSM technology, depending on the service availability. Data is directly sent by the sensor node to the E-Cloud or any other public cloud services using an UDP or a MQTT protocol. Some of the models offer USB charging, others use wireless charging method for the on-board lithium-ion battery. In cases where no battery is needed, the USB connector can be used to power the device.

In case of using the multipoint-to-point sensor organization, the ideal node is the local WLAN sensor module built around the NeoCortec MESH modem. This module is optimized for battery operation, featuring wireless charging for the on-board lithium polymer cell. The product exists with optimal low-power consumption using the internal ARM Cortex M0+ MCU built into the NC1000 mesh module, other version offers an external low-power MCU and a further feature connector for external I2C and analogue sensors.

What gateway solutions can be used in the multipoint-to-point topology?

In the case of using a local WLAN of smart sensors, the topology needs one of the E-IoT NeoMesh-LPWA gateways. There are several task-specific gateways created for, amongst others, industrial, agricultural and demonstration purposes. They feature wired interfaces and the ability to be integrated into the NeoMesh, at the same time using cellular communication to the cloud. The most general-purpose gateway device has only NeoMesh and LPWA connectivity on board.

Building into the NeoMesh, this device constantly collects the data arriving from one of the sensor nodes. After decoding them it creates the JSON telegram required by the E-Cloud service and uses the LPWA (NB-IoT/LTE-M) cellular network to get them into the cloud. It offers a fall back to 2G when LPWA services are unavailable. Powered from mains via the USB-C connection, the gateway device offers an affordable, sustainable, and stabile way of collecting data from the possibly large sensor mesh and connecting that to the Internet of Things.

Another, more enhanced version of the gateway is equipped with a legacy LTE modem, with higher bandwidth. It offers the possibility of either using the WiFi-Smart feature for indoor localization or gathering location information from the GSM towers in case GNSS services could not be used.

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