Protocols Notes
Protocols
Introduction to Non-IP Based Protocols
A personal area network (PAN) is a network that enables communication between devices near a person
They can be wired (USB), or wireless (WPAN) (ZigBee, Bluetooth…)
Its range is a few meters
Bluetooth Wireless Protocol
Bluetooth 5 is revolutionizing IoT.
Offers up to 4x the range, 2x the speed, and 8x the broadcasting message capacity.
Improved coexistence with other technologies.
Bluetooth Low Energy (BLE) is prominent where power consumption is crucial.
BLE remains in sleep mode except when a connection is initiated.
BLE guarantees about 4/5 years of battery life.
Bluetooth 5 increases data transfer bandwidth from 1Mbps to 2Mbps without increased power consumption.
Extended range quadruples from 50 meters to 200 meters, providing robust connections.
Extended range and higher speed cannot be used simultaneously while maintaining low power consumption.
Increased broadcasting message capacity supports larger data packets up to 255 octets.
More efficient use of advertising channels.
Protocols Stack
Controller
Physical Layer (PHY):
Handles analog communications.
Defines modulation and demodulation of analog signals.
Applies source coding to transform signals into digital symbols.
BLE Radio:
Uses the 2.4 GHz ISM band (license-free).
Consists of 40 channels: 3 advertising channels and 37 data channels.
Each channel is 2 MHz width.
Advertising Channels
There are RF channels in BLE, each separated by MHz (center-to-center).
Three are Primary Advertising Channels.
Remaining channels are used for Data Packet transfer during a Connection.
Packets are sent at a fixed interval defined as the Advertising Interval.
Link Layer (LL):
Interfaces directly with the physical layer (PHY).
Implemented as a combination of custom hardware and software.
Hardware part includes CRC generation and verification.
Manages the link state of the radio (master, slave, advertiser, or scanner).
BLE Operation
Five link states:
Advertising: Devices transmit advertising packets on advertising channels.
Scanning: Devices receive advertising on advertising channels without intending to connect.
Active scanning: Link layer listens for advertising PDUs and may request additional information.
Passive scanning: Link layer only receives packets; transmission is disabled.
Initiating: Devices listen for connectable advertising packets and initiate by sending a connect packet.
Connected: Relationship between master (initiator) and slave (advertiser).
Standby: Device in the unconnected state.
Bluetooth Low Energy Discovery Process
Devices use advertising channels to find each other.
One device advertises, and another scans.
Each time a device advertises, it transmits the same packet in each of the three advertising channels.
This sequence is called an advertising event using ADV_IND Advertising Packets.
Advertising and Scanning
Activities occur at regular intervals.
Advertisers and Scanners are not synchronized.
Discovery takes place when advertising and scanning activities overlap.
BLE States
Advertising
Scanning
Connected
To connect two BLE devices:
One device advertises.
The other scans for it and initiates the connection.
Advertising involves broadcasting packets, allowing another scanning device to discover them.
Wireless Coexistence
Improvement in coexistence is with other nearby BLE devices.
The random frequency-hopping scheme decreases the chance of neighboring BLE devices transmitting on the same radio-frequency (RF) channel simultaneously.
Bluetooth 5 allows a user to control multi-devices from Bluetooth-equipped smartphones, headphones, etc.
Bluetooth Hopping
Utilizes frequency-hopping spread spectrum technology to avoid interference.
Signal switches carrier channels rapidly, at a rate of hops per second.
Reduces the possibility of interference.
Zigbee
Wireless technology standard defining communication protocols for short-range communications.
Designed for control and sensor networks.
Low-cost implementation of low power devices with low data rate for short-range wireless communications.
Operates in unlicensed bands including GHz, MHz and MHz.
Zigbee Applications
Home automation: Controller with a software application controls smart devices through a central hub.
Medical data collection
Industrial control systems
Home Automation
Perform control tasks inside a building.
Zigbee Components
Zigbee Coordinator (ZC)
Highly capable device used to form and initiate network functions.
Each network has a single ZC.
Responsible for forming the network by selecting the appropriate channel and security mode.
Trust center authenticates new nodes and distributes network keys.
After network formation, can behave as a ZR.
Zigbee Router (ZR)
Responsible for routing traffic between nodes.
May not sleep and thus, is not suitable for battery-operated devices.
Receives and stores messages intended for their children.
Gatekeepers responsible for allowing new nodes to join the network.
Zigbee End Device (ZED)
Simple endpoint device (e.g., light switch).
Communicates with the coordinator but has no routing logic.
Relays messages that are not targeted to it.
Channel Access
Coordinator assigns one channel to the network for all devices to share.
Channel access methods:
Contention-free method: Coordinator dedicates a specific time slot (GTS) to each device.
Contention-based method: Devices do not need to be synchronized.
CSMA (collision avoidance mechanism) is used.
Device goes into receive mode and detects if there's any signal in the channel.
Transmits data only if the channel is clear; otherwise, backs off for a random time and tries again.
Zigbee Topologies
Star Topology
Simplest/less expensive.
No routers.
End devices cannot communicate directly.
Mesh Topology
Every node (except end devices) is connected with the neighboring node.
Message hops from one device to another.
If a node fails, data can be re-routed using another path.
Tree Topology
Not very different from a mesh configuration.
Routers are not interconnected.
Zigbee Characteristics
Intended for low power consumption applications that do not require large data transfer speeds.
Common applications: home automation, wireless network sensors, smoke or motion sensors, medical data collection, and industrial control systems.
Features:
Devices do not connect individually to the Internet.
Offers low energy consumption.
Range: Up to 75-100 meters indoor and up to 300+ meters (line of sight).
Very low data transfer speeds: kbit/s.
Network join time: ~ msec (Wifi: up to s, Bluetooth up to s).
Number of devices: Up to in theory / in practice.
Low cost products and cheap implementation.
AES cryptographic algorithm.
RF Bands
Three different bands assigned to Zigbee:
Europe: MHz
US/Australia: MHz
Across the World: GHz
Only one channel is selected for use in a network.
Zigbee Benefits
Self-forming: Zigbee network can configure itself automatically.
Self-healing: Zigbee can reconfigure itself dynamically if nodes become faulty, removed, or disabled.
Interoperability: Zigbee modules from different manufacturers can operate together.
Z-Wave
Alternative to WiFi or Bluetooth.
Functions as a mesh network system.
Zigbee is an open protocol managed by the Zigbee Alliance, while Z-Wave is private.
Being closed guarantees that all compatible devices function without any problem between them.
Z-Wave has a greater range than Zigbee (up to m) and usually offers greater stability in connections.
Zigbee supports more connected devices ( compared to just over ).
Z-Wave requires a hub or bridge to connect and manage IoT devices.
Zigbee uses the GHz frequency, so it has no problem to be used in any country.
Z-Wave uses different radio frequencies in different countries, which means we cannot use them in countries where different frequencies are used.
Features:
Requires the use of a bridge or hub device.
Mesh network system.
Devices do not connect individually to the Internet.
Offers low energy consumption.
Maximum reach m.
Very low data transfer speeds, maximum speed of kbit/s.
Mainly for home use, control of household items, sensors, electronic security elements.
It is a closed protocol.
Introduction to IP Based Protocols
Why IP-Based Protocols?
Use of existing infrastructure.
IP-based networks can readily be connected to other IP-based networks without the need for gateways.
6LOWPAN
Combines the latest version of the Internet Protocol (IPv6) and Low-power Wireless Personal Area Networks (LOWPAN).
Allows for the smallest devices with limited processing ability to transmit information wirelessly using an internet protocol.
Newest competitor to ZigBee.
IPV6 provides significant theoretical addressability of or unique addresses.
Well-suited for IoT growth.
Acronym: IPv6 over Low-Power Wireless PAN.
Networking technology or adaptation layer allowing to transport IPv6 packets over small link layer frames, such as those defined by 802.15.4.
More suitable for high density.
No Intermediate gateway.
6LOWPAN Topology
Mesh networks residing on the periphery of larger networks.
Flexible topologies allowing for ad hoc and disjointed networks without any binding to the internet.
Ad-hoc networks can form without requiring Internet connectivity of an edge router.
An edge router (also known as border router) is necessary as it has four functions:
Handles communication to the 6LOWPAN devices and relays data to the internet.
Performs compression of IPv6 headers by reducing a 40-byte IPv6 header and 8-byte UDP headers.
A typical 40-byte IPv6 header can compress to two to 20-bytes depending on usage.
Initiates the 6LoWPAN network.
Exchanges data between devices on the 6LoWPAN network.
Thread
Relatively new networking protocol for IoT based on IPV6 (6LOWPAN).
Principal target is home connectivity and home automation.
Launched in July of 2014 with the formation of the Thread Group Alliance.
Based on the IEEE 802.15.4 protocol and 6LOWPAN.
Commonality with Zigbee and other 802.15.4 variants, but Thread is IP addressable.
Builds on the data and physical layers provided by 802.15.4.
Mesh-based, making it attractive for home lighting systems with up to 250 devices in a single mesh.
By enabling IP addressability in the smallest of sensors and home automation systems, one can reduce power.
Edge router hosting a Thread mesh network doesn't need to process application layer protocols.
IPV6 compliant, and inherently secure with all communications being encrypted using the Advanced Encryption Standard (AES).
Up to 250 nodes can exist on a Thread mesh all with fully encrypted transport and authentication.
A software upgrade allows a pre-existing 802.15.4 device to be Thread compatible.
IEEE 802.11
Standard, popularly known as WiFi, lays down the architecture and specifications of wireless LANS (WLANS).
WiFi or WLAN uses high-frequency radio waves instead of cables for connecting the devices in LAN.
Users connected by WLANS can move around within the area of network coverage.
Architectures
Basic Service Set
Independent Basic Service Set
Distribution System
Topologies
Infrastructure
Station (STA) communicates with a central access point (AP).
AP can be a gateway to other networks (WAN), a router, or a true access point in a larger network.
Known as Infrastructure Basic Set Service (BSS).
This is a star topology.
Ad hoc
Nodes can form an Independent Basic Set Service (IBSS) where each station communicates and manages the interface to other stations.
No access point or a star topology is used in this configuration.
This is a peer-to-peer type of topology.
Distribution system (DS)
Combines two or more independent BSS networks through access point interconnects.
Long-Range Protocols
5G
5th generation of mobile networks, a significant evolution of today's 4G LTE networks.
Designed to meet the very large growth in data and connectivity of today's modern society and the Internet of Things.
Will initially operate in conjunction with existing 4G networks before evolving to fully standalone networks.
Initial 5G services commenced in many countries in 2019, and widespread availability is expected by 2025.
Advantage of 5G is the fast response time referred to as latency.
Latency is the time taken for devices to respond to each other over the wireless network.
3G networks had a typical response time of milliseconds, 4G is around milliseconds, and 5G will be as low as millisecond.
5G delivers continuous connection, greater capacity, and faster speed and response times through:
Better Connection
Designed to work in conjunction with 4G networks using a range of macro cells, small cells, and dedicated in-building systems.
Small cells are mini base stations designed for very localized coverage (typically from 10 meters to a few hundred meters).
Essential for the 5G networks as the mmWave frequencies have a very short connection range.
Increased Spectrum
Initial frequency bands are below 6 GHz (often in the 3.3-3.8 GHz bands).
Additional mobile spectrum above 6 GHz, including the GHz bands (mmWave), provides significantly more capacity.
Massive MIMO
Multiple element base station for greater capacity, multiple users, faster data.
Uses 'massive' MIMO (multiple input, multiple output) antennas that have very large numbers of antenna elements or connections.
More people can simultaneously connect to the network and maintain high throughput.
The overall physical size of the 5G massive MIMO antennas will be similar to 4G.
MQTT Protocol
The Message Queuing Telemetry Transport (MQTT) is a lightweight, publish-subscribe network protocol that transports messages between devices.
Simple messaging protocol designed for constrained devices with low-bandwidth.
Allows you to send commands to control outputs, read and publish data from sensor nodes, and much more.
MQTT Advantages
Distribute information more efficiently.
Increase scalability.
Reduce network bandwidth consumption dramatically.
Reduce update rates to seconds.
Very well-suited for remote sensing and control.
Maximize available bandwidth.
MQTT Broker
Software primarily responsible for receiving all messages, filtering the messages, deciding who is interested in them, and then publishing the message to all subscribed clients.
Software that could be installed on computers, servers, or others.
MQTT Broker Benefits
Eliminate insecure Connections
Easily scales (from few devices to thounsands)
Manages the clients easily
It is like a post-office, instead of sending messages peer to peer, all messages are sent/ received by the broker.
Publish/Subscribe Models
ONE TO MANY: Several clients subscribe to the same topic.
MANY TO ONE: Several clients publish over the same topic, but only one subscriber.
MQTT is a bidirectional messaging protocol, due to the broker role.
All devices in MQTT architecture are less coupled and more secured.
The broker is the central location for security.
TLS Encryption
Username/password
Each client is unaware of other clients
Automatic redundant Backup broker
All MQTT implementations have their clients published data only when there is change in value.
New subscribers got the last data published. So the broker retains the last value published about a topic.
The broker keeps track of all sessions. So if a device looses the connection temporarily, it can easily reconnect with the broker without having to resubscribe to topics.
The broker handles 3 types of messages:
Birth
Death
Last Will and Testament ( when something is wrong with a connection)