Wireless communcation
- WPAN: Wireless Personal area
- WLAN: Wireless local area
- WMAN: Wireless metropolitan - For the city
- WWAN: WIreless Wide area network
The difference is the range
WPAN
- Reaches varies from a few centimeters to a few meters
There are two classes:
- IP based
- Non IP bassed
Non ip based WPAN
- Bluetooth: Wireless technology standard for exchanging data between fixed and mobile devices over short distances using short wavelength ultra high frequenct radio waves in the ISM bands
- ZigBee: Specification for a suite of high level communcation protocols used to create WPAN with small, low poer digital radios. Zigbee is a low power, low data rate and close proximity wireless ad hoc network using ism 2.4 ghx in most places
Bluetooth:
- Low power wireless connectivity technology
- Ultra low power bluetooth
Blue tooth communication process
- Comprised of two wireless tech systerm:
- Basic rate
- Low energy
- Nodes can be either advertisers or scanner
- Advertisers: Devices transmitting advertiser packets
- Scanners: Device Receiving advertiser packet without the intention to connect
- Initiators: Devices attempting to form a connection
- advertiser sends advertisements.
- scanner receives advertisements.
- initiators connect in response to a scanned advertisement.
Wireless headphoen advertise, iphone is initiator to connect to that advertisment
Events
- Advertisments: Broadcast to scanning devices altering them of the wish to either pair or relay a message in the advertisment packet
- COnnecting: Process of pairing device and hsot
- Peridoic scanning
Process
- Advertise issues connectable agent
- Listern can become initiator by making connection request
- Advertiser determins if its wishes to form connection
- COnnection is form the advertising event ends
- Init called master
- Advertiser is now call slave
- The connection is termed a piconet
BLE connection
State:
- Initiating
- Connected
- Standby
BLE Profile - Generic access profile (GAP)
- Controls connection and advertising in bluetooth
- Device roles: Peripheral IOT Device and Centrea
- Advertise data
- Peripheral wants to send data to more than one device to a time
BLE Profile: Generic Attribute Profile (GATT)
- Defines the way that two BLE devices transfer data back and forth using concepts using Services and characteristics
- Makes use of a generic data protocol: Attribute protocol (ATT)
- ATT is used to store services, characteristics and related data in a simple lokuptable using 16 bit ID for each retry
- GATT comes into play once the connection has been established
Server-client relationship
- Peripheral is the GATT Server that holds ATT lookup data, services and characteristics
- Phone is the GATT client that sends request to the server
GATT
- Transaction are started by client who gets response by server
- periphareal suggest a connection interval to the device during connection
Services
- USe to break data up
- Service can have more than one characteristics
- Each service have a unique numeric ID called a UUID
Characteristics
- Encapsulate a single data point
- Each characterics has a predefined 16bit or 128 but UUID
-
Characteriics can read write notifry property
- Read: Central reads a data from a peripheral chara
- Notify: Peripheral infoms central device that a new data value is available in a specific chara
- Write: central writes a data in a peripheral chara
Transaction property
- Read property: Read the temperature
- Write property: How to react to the change
- Notify property: Notify the change
Zigbee
- WPAN protocol based on IEEE 802.15.4 foundation targeted for commercial and residential IoT networking that is constrained by cost, power and space
- Low power wireless mesg networking
Components
- Single ZC
- ZC can behave like ZR after connecting
ZR (Zigbee router)
- Not necessarily needed
- Optional
- Handles some load of mesh
ZED (Zigbee end devices)
- End point device
- Can communcicate with router or controller
- Cannout route
- e.g light switch, thermostate
Data traffic
- Periodic data: Delievered at a rate defined by application
- Sensor preiodically transmitting
- Intermeittent data: Application or external stimulus occurs at random rate
- light switch
- Repetitive low latency data: Allocate time slots
- computer mouse or keyboard
Topo
Benefits of IP
- Ubiquity
- IP stacks are provided by nearly every operating system and every medium
- IP specifies the exact format for all data communications and the rules used to communicate, acknowldege
- Standard basded
- Scability
- IP has demostrated scale and adoption
- IPV6 could provided a unique IP address to every atom
- Reliable
- Assumes data is not guaranteed to be delivered
- Packet is treated as independent
- IP is connectionless because each packet is treated independently
- IP is best effort delivery
IP based WPAN
- Low power RF communcation system doest not need high bandidth
- Simplest of sensor can act as network citizen
6LoWPan TOPO
- Similiar to zigbee
- Mesh netowkrs residing on the periphery of larger networks
- Topo are flexible
- Can be connected to the backbone or internet using edge routers
Nodes movement
- Nodes are free to move and reorganised/reassembled in a mesg
- A node can move and associate with a different age router in a multi home scenario or even move between different 6lowWan meshes
WAN
- Long range communication
- Connects the local network containing the IoT devices to the internet
- Long range communciation is usually a service, it has a subscription to a carrier providing cellular tower and infrastructure improvements
Cellular connectivity
- Seperation of frequencies from neighbours neartest
- honey comb structure: Make sure that each of the frquency cannot interfere with the other holes
- No two similiar frquencies are within one hex space from each other
- But there is possible to have intererences in hex spaces with different colour
Connectivity of IOt Devices to internet
- Different from consumer based cellular devices
- Smartphone pulls info off internet
- IOT, data can be sparse and arrive in burst
- Maj of adata is generated by tge devices and travel over iplink