3. Communication Standards and Technologies Flashcards
What does RFD stand for?
Reduced function device.
Explain what point-to-point communication is.
A single node or sensor can exchange data with only one gateway (dedicated link).
Explain point-to-multipoint communication.
A single node can communicate with multiple nodes in the network at the same time.
Name the four famous network topologies.
Mesh, star, ring, bus.
Explain mesh topology.
In a mesh network topology, there is a point-to-multipoint communication link between a device and other devices in the network so that the data can hop from one node to another before it reaches the gateway. The sensor nodes in a mesh network can serve either as an endpoint, to transmit their own captured data, or repeaters, which relay data received from other nodes or sensors. In a full mesh network, all homogeneous nodes are fully interconnected to each other and have relaying function. In a full mesh network, all nodes can implement the full protocol functions and serve as a coordinator.
In partial mesh networks, only selected nodes have the repeater function to relay the messages. The RFD sensor nodes are the endpoints that can only transmit their data to the sensor nodes with relaying functions. Full mesh topology is uncommon in IoT networks, because in most IoT applications, the messages captured by the endpoint sensors do not need to be distributed among other nodes. Rather, the data should be transmitted to the destination (gateway). Moreover, since in full mesh topology all sensor nodes need to be in their range, the effective coverage of the network is limited.
Explain star topology.
In a star network topology, which is simpler and cheaper to deploy than mesh topology, every sensor node establishes a point-to-point communication link with a central coordinating node (i.e., a hub or gateway) that typically has the full protocol stack functions. The following figure shows the star topology.
Name four IoT network protocols.
MQTT: Message Queue Telemetry Transport
CoAP: Constrained Application Protocol
HTTP: Hypertext Transport Protocol
AMQP: Advanced Message Queuing Protocol
Explain MQTT QoS (Quality of Service).
QoS level 0: Unreliable, fire-and-forget model, messages aren’t duplicated or acknowledged.
QoS level 1: Reliable, delivered at least once, and might be duplicated.
QoS level 2: Reliable, data is delivered without duplications.
What do TCP, IETF, UDP, DTLS, and TLS stand for?
Transmission control protocol, internet engineering task force, User Data protocol, Datagram Transport Layer Security, and transport layer security.
What are the two message types used by CoAP?
- Confirmable message (CON), which can be mapped with QoS level one of MQTT. It is a reliable message where the client keeps sending the message until it gets an acknowledgement message (ACK) with the same ID from the server.
- Non-confirmable messages (NON), which can be mapped with QoS level zero of MQTT. It is an unreliable message in which its receipt is not acknowledged by the server.
Name two messaging types in AMQP.
One messaging type used in AMQP is called the unsettle format, which is like MQTT QoS level zero. The other type is settle format, which is a reliable messaging model similar to MQTT QoS level one.
how do we determine what set of suitable technologies to use to get data from the sensors to the gateway? What questions do we ask?
- What is the report range?
- What is the report frequency?
- What is the throughput (How fast does the data need to be transmitted?)?
- What is the message size?
- What is the power consumption?
- What is the latency?
- What is the mobility?
- What is the cost?
Name and explain two wired IoT technologies.
Ethernet: Connects IoT devices to the internet via cables and ethernet switches. High data rates and ultra-low latency.
Power-Line Communications (PLC): Using OFDM (Orthogonal Frequency division multiplexing), an advanced modulation technique, it is possible to connect IoT devices to the internet through power lines, minimizing the cost of cable infrastructure.
Name and explain wireless IoT technologies.
Short-range technologies: near field communication (NFC), Bluetooth, ZigBee, Z-Wave, Thread, WirelessHART, and Wi-Fi. Of these technologies, Bluetooth, ZigBee, and Wi-Fi.
Low-Power Wide Area (LPWA): Long range, low power consumption, either unlicensed (LoRAWAN and Sigfox) or licensed spectrum (LTE-M and NB-IoT).
