1. Internet of Things
Amr El Mougy
Alaa Gohar

2. Independent BLE sensors
Layers of the IoT
Applications
Middleware
Processing Layer
High-end computational devices
Internet
Aggregation Layer
RFID reader
M2M
comm.
Smartphone
Gateways
Sensing Layer
Wireless Sensor Networks
Independent BLE sensors
Human emotions

3. Sensors Other Peripherals Sensor Node Battery Board
Microcontroller
Communication Module
Sensors

5. The Sensing Layer Sources of different types of information
Available sensors can detect a wide range of parameters and are connected to a wireless transceiver
Expected to be deployed in 10s of billions by 2020
These “sensor nodes” are typically required to remain operational for long durations (months or even years)
They are also small in size and thus have limited processing, memory, and energy capabilities
ZigBee
BLE
RFID

6. Radio Frequency Identification (RFID)
A system that consists of a tag that stores a limited amount of information (few KB) and a reader that obtains this information
Fast, low cost, unique identification of items
Uses RF which does not require line of sight (key advantage over barcode)
Other advantages over barcode:
Stores more data
Can be read from longer distances

7. Types of Tags Passive: No battery, draws power from RF
Very small storage (~1KB)
Small reading range (few metres)
Very cheap
Typically write-once/read-many times
Tag remains readable for a long time, often exceeds product lifetime
Active:
Small battery
Bigger storage (few hundred KBs)
Longer range (few hundred metres)
Not cheap
Typically re-writable
Larger size
Tag expires when battery dies

8. Automatic checkout at the grocery store
RFID Applications
Automatic checkout at the grocery store
Library management
Access control
Supply chain

9. Communication Process
RFID sends activation command that powers nearby tags
Tags respond with their data
Some material (metal, plastic, cardboard) can have negative effects on the RF signal

10. Collision Problems Reader collision
Multiple readers try to read the same tag at the same time
Tag cannot differentiate between readers’ signals and cannot respond
The challenge is that tags are very simple  no collision avoidance protocols can be implemented on them
Solution: implement protocols at the reader.
Ex: Readers can have different frequencies or work in different time slots. Alternatively, readers send beacons to announce their intention to transmit

11. Collision Problems Tag collision
Multiple tags receive the activation signal and respond
Reader receives reports from multiple tags  all readings are lost
Challenge is that tags are quite simple and cannot have protocols
Solution  hardware modification
The solutions general force tags to not transmit whenever they hear the reader
Transmissions can be probabilistic or selective

12. Sensor Networks

13. Network Topologies

14. The Wireless Signal A wireless signal is affected by three factors:
Attenuation due to distance
Shadowing due to large objects
Multipath fading due to small objects

15. Sensor Technology BLE ZigBee WiFi ANT RF4CE IrDA Range 10m 200m 300m
Throughput
1 Mbps
255 kbps
100 Mbps
60 kbps
1 Gbps
Delay
2.5 ms
20 ms
1.5 ms ~0
25 ms
Power efficiency
0.153 μW/bit
186
μW/bit
μW/bit
0.71 12
Power consumption
12.5 mA
40 mA
116 mA
17 mA
10 mA
Comments
No sleep cycle
Which one is more suitable for direct user interaction?

16. Applications
No longer true

17. Bluetooth
Bluetooth is the brand name for the family of standards known as
It was designed initially to replace wired cables
The name comes from the former king of Denmark who unified his country
Standard
Data Rate
Spectrum
Range
Comments
V1.0 and v1.0B
Not successful, had many flaws
V1.1 (2002)
Fixed many of the errors of the previous versions
V1.2 (2005)
1 Mbps
2.4 GHz
1m, 10m, 100m
V2.0 (2004),
V2.1 (2007) + EDR
3 Mbps
V3.0 + HS (2009)
24 Mbps
WiFi links are used for data communication
V4.0 BLE (2011)
1~2 Mbps
Very low power consumption
V5.0 (2016)
2 Mbps
4x range
Higher message capacity

18. Logos

19. Traditional Bluetooth
Traditional Bluetooth is connection oriented. When a device is connected, a link is maintained, even if there is no data flowing.
Sniff modes allow devices to sleep, reducing power consumption to give months of battery life.
Peak transmit current is typically around 25mA.
Even though it has been independently shown to be lower power than other radio standards, it is still not low enough power for coin cells and energy harvesting applications

20. Traditional Bluetooth Architecture
Communication uses Master – Slave architecture
Time is divided into slots and the master controls who transmits in each slot
A set of one master and its slaves is called a Piconet
No direct communication between slaves
Two or more joined Piconets is called a Scatternet
Parked Slaves
Master
Active Slaves

21. Connected State - Transmission Modes
Asynchronous Connection-Less (ACL) mode
One ACL can exist between any two devices
Even slots are for master transmissions and odd slots are for slave
Synchronous Connection-Oriented (SCO) mode
Reserved channel bandwidth and slots between master and slaves
A master can support up to 3 SCO links
A slave can support 3 SCOs from one master or 2 SCOs from different masters
No retransmissions
Used for voice communications

22. Transmission modes

23. Bluetooth High Speed Connections are established using Bluetooth
Data is transferred using WiFi channels
Backward compatible with other Bluetooth devices
Consumers benefit from the way they use Bluetooth while benefiting from high speed WiFi connections

24. Bluetooth Low Energy
A new radio, new protocol stack, new profile architecture
It’s designed to run from coin cells
It is a radio standard for a new decade, enabling the Internet of Things
Features:
Mostly new PHY
New advertising mechanism, for ease of discovery & connection
Asynchronous connection-less MAC: used for low latency, fast transactions (e.g. 3ms from start to finish)
New Generic Attribute Profile to simplify devices and the software that uses them.
Asynchronous Client / Server architecture
Designed to be LOWEST cost and EASY to implement

25. Bluetooth Low Energy
For Bluetooth low energy, data throughput is not a meaningful parameter. It does not support streaming.
It has a data rate of 1Mbps, but is not optimised for file transfer.
It is designed for sending small chunks of data (exposing state).
It’s good at small, discrete data transfers.
Data can triggered by local events.
Data can be read at any time by a client.
Interface model is very simple (GATT)
Generic Gateways (optimized for the IoT):
Devices that support BLE Gateway functionality provide a transparent pipe from a device to an IP address.
Middleware at the IP address can access the device directly as if it were a collector talking to it locally.
The Gateway device plays no part other than in acting as a pipe.

26. Protocol Stack Low Complexity 1 packet format
2 PDU types – depending on Advertising / Data Channel
7 Advertising PDU Types
7 Link Layer Control Procedures
Useful Features
Adaptive Frequency Hopping
Low Power Acknowledgement
Very Fast Connections
Devices can advertise for a variety of reasons:
To broadcast promiscuously
To transmit signed data to a previously bonded device
To advertise their presence to a device wanting to connect
To reconnect asynchronously due to a local event

27. The ATT Protocol
A Bluetooth packet is called an attribute. The ATT protocol defines the attributes
Each attribute is defined using three fields:
16-bit handle: a sequence number of the attribute
Universally unique ID (UUID): an identifier specified by the application or GATT
A value: the content of the packet. Can be of any length (Beacons specify 31 bytes)
ATT features include searching for all attributes with the same UUID and getting all attributes within a specific range of handles
ATT is client-server

28. The GATT Protocol
GATT defines how ATT attributes are grouped together to provide meaningful services
This is done by specifying a range of handles that belong to the same UUID (ex: all handles belonging to UUID 0x2816 are temperature readings
GATT is also able to specify characteristics for the readings (ex: all readings with UUID 0x2816 are temperature with unit Celsius and were taken on 9 Feb 2016). These are read only parameters

31. The GAP Protocol
GAP is about interoperability. It defines how different devices are going to implement specific functions
Thus, the GAP profiles specify how nodes will operate (discover, connect, etc.) to serve a particular application
It defines the topology of the BLE network

32. Roles Broadcaster (advertiser): Broadcast advertisements
Observer (scanner): Listen for advertisements. Can connect to an advertiser.
Central (master): Communicates with the device in slave role, defining timings and transmissions.
Peripheral (slave): A device connected to a master. Can have only one master at the same time.

33. Active States

34. GAP States A Broadcaster cannot enter the Scanning state.
An Observer cannot enter the Advertising State.

35. Scanning State
The way to detect other Bluetooth nodes is to scan looking for slave messages (called advertisements). Some parameters should be configured to allow scanning in the desired way.
Some functions have been implemented to easily scan for other devices, defining time, number of devices to discover, etc.
Parameters must be configured before doing a scan. The parameters are defined inside the General Access Profile (GAP) of the module. It is not possible to change scanning parameters while scanning, so the user must stop scanning before making any change.
General Access Profile mode:
There are three possible states regarding visibility of BLE devices, so the scan can filter the devices by this state. The possible choices are:
Limited discoverable: Discover only slaves which have the limited discoverable mode enabled.
Generic discoverable: Discover slaves which have limited discoverable mode or generic discoverable mode enabled.
Observation: Discover all devices (default).

36. Scanning State
Parameters to be defined include: scan interval, scan window, and passive/active scanning:
In passive scanning, the BLE module just listens to other node advertisements. When one of these advertisements is detected, the module reports the discovered device. Normally, the advertisement contains information like discoverability and connectability modes, TX power level, MAC address of the node (called advertiser) or application data.
On the other hand, in active scanning the module will request more information once an advertisement is received, and the advertiser will answer with information like friendly name and supported profiles. The advertisement packets are configurable as is described in next sections.
In addition, BLE has an option to accept advertisements only from specific nodes (called the whitelist)
The transmission power can be set to one of 16 ranges
BLE, like many other standards, provides RSSI measurements. The higher the RSSI, the stronger the received signal
Can be used for indoor localization

37. Advertising State
Advertising is a process used for BLE modules to send data to other BLE devices.
This data is packed in advertisements, which are modifiable by the user, so they represent an easy way of sending data without the need of connecting first.
The advertisements contain information about address of the advertiser, discoverability and connectability modes, TX power level, application data, etc.
They can be built according to the Bluetooth standard or customized by the user to send its own data.
Configuring advertisements: Visibility - GAP discoverable modes
This specifies who can see the advertisements of the BLE module
Non discoverable: Device is not advertising
Limited discoverable: Device will be visible using limited discoverable scanning mode
General discoverable: Device will be visible using general discoverable scanning mode

38. Advertising State
Configuring advertisements: Connectability - GAP connectivity modes
A flag inside the advertisements states who can connect to this node
Non connectable: Device is not connectable by others
Direct connectable: Device can be connected by only one node
Indirect connectable: Device can be connected by any node
Configuring advertisements: Responses to scan requests
Defines an advertisement policy to specify if the module will respond to scan requests and allow connections
All: Responds to scan requests from any master, allows connection from any master.
WhiteList scan: Responds to scan requests from whitelist only, allows connection from any master.
WhiteList connect: Responds to scan requests from any master, allows connection from whitelist only.
WhiteList all: Respond to scan requests from whitelist only, allows connection from whitelist only.
Time between advertisements is configurable
Maximum size of advertisement is 31 bytes
Custom payload can be defined, but if compatibility with BLE is required, a specific format must be used
Advertisements can be normal (when state is anything but non-discoverable) or a scan response