Lecture 02 Types of Wireless Systems and Networks
Types of Wireless Systems and Networks
WSN - Wireless Sensor Network
Large number of self‐powered small sensing nodes which gather information or detect special events and communicate wirelessly with the end goal of handing over their processed data to a base station.
3 main components
in a WSN: the sensor, the processor, and the radio for wireless communication.
Have the potential to be everywhere
, on roads, in our homes and offices, forests, battlefields, disaster struck areas, and underwater.
Potential for the third wireless revolution ”Internet of Things”, i.e. utilizing wireless sense and control technology to monitor, predict and respond to natural disasters, traffic, hospitals etc.
Technology for D2D (device to device) and M2M (machine to machine) applications
Sensors range from camera, microphone, physiological sensors, highly integrated with signal processing capability and intelligence to microsensors for image, acoustic, seismic, pressure etc. sensing
A sensor node, also known as a mote, is capable of performing some processing, gathering sensory information and communicating with other connected nodes in the network
A mote is a node but a node is not always a mote
Predominant standards used in WSN: ₋
ZigBee based on 802.15.4 and has a fixed data‐rate of 250 kbit/s. ₋
ZigBee IP: Enriches IEEE 802.15.4 by adding network and security layers and an application framework for a full IPv6‐based wireless mesh networking solution and provides seamless Internet connections to control low‐power, low‐cost devices.
Zigbee 3.0, 6LoWPAN, WirelessHART
Extended range of sensing which improves data quality
Fault tolerance due to redundancy in data from different sensors
Distributed processing of large amounts of sensor data
Scalability to large scale deployment and ease of use:
Relatively inexpensive and can be easily scattered over large areas
Collaboration of different types of sensors to perform a larger sensing task
Highly dynamic and harsh environments
Communication and Sensor nodes failure and addition of new nodes
Distributed computation protocol and wireless comm paradigm required
Power consumption constraints for nodes using batteries or energy harvesting
When you dont have a centrlaized system it means that the network is very dynamic, sensors can fail and so on.
Area, Earth, Environmental and Habitat monitoring: Air quality, water quality, waste water, forest fire, landslide, earthquake, flood, micro‐climate and wildlife monitoring.
Military surveillance and Home security
Chemical/biological agents monitoring and detection (London, Stockholm, Brisbane monitor concentration of dangerous gases)
Surveillance and reconnaissance (use of sensors to detect enemy intrusion in the military)
Industrial monitoring (eg. Machine health monitoring of inaccessible location, moving parts, hazardous areas)
Industrial sense and control applications
wireless link reliability
Types of Wireless Networks
Ad hoc Networks
Self –configuring, infrastructure‐less wireless networks
Multi‐hop peer‐to‐peer networks
If nodes cannot directly reach destination, intermediate nodes must relay messages to destination
Widely used where connectivity of all nodes is not guaranteed
Only solution if no infrastructure is available
Widely used in military applications
Requires algorithms and incurs overhead for efficient message routing and control
Increase delivery latency due to multiple hop delay incurred
Hybrid (Centralized or Peer‐to‐peer)
Unicast, multicast and broadcast networks
Opposed to centralized network where we have base station and then accesspoints, the ad hoc networks means no infrastructure – we are all on the same level peer to peer. No one plans the network for you, that means that there might not be a communication path, so I will just forward to that person I can reach and are linked too, and hope that THAT person will forward the packets to the next nearest to the destination node. multi hop communication.
Ad Hoc ‐ Wireless Mesh Networks
Similar to Ad Hoc, but more static/permanent, with little or no mobility of router nodes
Less resource constraints (energy, processing power) compared to Ad Hoc
The trend now is to use wifi mesh systems. We set up some nodes that has better ressources lets say like our phones. They are used as hubs to connect to the individual users that can be very mobile.
Developing Countries: Wireless mesh networks are useful in countries without a widespread wired infrastructure, such as telephone service or even electricity. Solar‐powered nodes can be connected to one cellular or satellite Internet connection, which could keep a whole village online.
Isolated Locations, Rugged Terrain which are too far off the grid for traditional high‐speed Internet service providers. A series of nodes would be mounted from the nearest available wired access point out to the hard‐to‐reach area.
Temporary Venues: Construction sites can capitalize on the easy set‐up and removal of wireless mesh networks. Mesh nodes can be moved around and supplemented as the construction project progresses.
Ad hoc - MANET - Mobile Ad hoc Networks
collection of wireless mobile nodes forming a temporary network without the aid of any centralized administration or station
Autonomous and infrastructure‐less
Multi‐hop routing (Nodes are data source, data sink and router)
Dynamic network topology – Nodes join and leave
Energy constrained operation (sensors and mobile devices have limited power)
Bandwidth constrained variable capacity links
Limited physical security
Self‐creation, self‐organization and self‐administration
When problem you have to handle is the network topology because it is very dynamic She gives the example with the iphone and xiaomi. The iphone is more powerful. So very different devices in the same ad hoc (peer to peer) network causes problems Engineering problems – how do you handle people that come and go, how do you know when they leave. How do I make sure that it is energy efficient. All the links, resources,
Challenges to network protocol designs on all layers of the protocol stack
Physical layer must deal with rapid changes in link characteristics
Media access control (MAC) layer needs to:
allow fair channel access
minimise packet collisions
deal with hidden and exposed terminals
Amidst changing neighbouring nodes, or nodes sleeping to reduce energy drain with no coordination/cooperation among nodes
Network layer, nodes need to discover one another and cooperate to compute the routes
Transport layer must be capable of handling packet loss and delay characteristics that are very different from wired networks
Applications should be able to handle possible disconnections and reconnections
Frequency of route changes is a function of node mobility
Tradeoff between route change frequency and maintenance overhead
A dense network provides greater route alternatives, shorter paths, less chance of partition and greater aggregate throughput
Quality of Service (QoS) Challenges due to
Link variability and disruption
How often are you going to update your route change? The thing is that when you update it takes time – that is the cost.
Slide 16, lecture 2
Slide 18-19, lecture 02
WSN - Wireless Sensor Network
Slide 22-24 lecture 02-03...
Types of Wireless Systems
WPAN - Personal Area Network
Networks create themselves in ad hoc manner when devices are within range, no independent pre‐existing networks
Devices discover one another
Provides wireless connectivity up to 10m or so
Hands‐free headset, wireless mouse, wireless printer
Eg. NFC (Near Field Communication), Bluetooth, IrDA (Infra Red Data Association), WiFi
WLAN - Local Area Network
Created by users
Centralized: wireless local area data networks
Peer‐to‐peer: MAC/PHY for ad hoc networks
Summary at slide 6, lecture 02
WAN - Wide Area Network
Created by cellular carriers
Cellular telephony, satellite, metropolitan area data networks (GSM, GPRS, EDGE, LTE)
Centralized topology with Base Stations connected to Backbone network
Mobile terminals communicate with the base stations