Wireless Communications & Adhoc Networks

Jokhio Sultan Salahuddin Kohistani07CS24

Computer Communication & Network Management

Department of Computer Systems EngineeringMUET Jamshoro

Agenda Wireless Communications◦ Introduction◦ Generations of Wireless Communications◦ EM spectrum◦Modes/Types◦Wireless Computer Networks◦ Techniques◦ Security◦ Ad hoc Networks

Contents

Wireless Communication Wireless Computer Networks Wireless LANs Spread Spectrum LANs IEEE 802.11 Architecture Specification Standard

Adhoc Networks

AGENDA

Wireless ◦Without wires or without physical conducting material or

carrier.◦Unguided Medium

Communication◦ Information propagation from source to destination.

Hence, Wireless Communication;◦ Transfer of information over a distance without utilizing

electrical conductors or "wires".

Wireless Communications (Introduction)

Wireless Communications (Generations)

Wireless Communications (Generations)

Wireless Communications (4Generation)

Wireless Communications (Electromagnetic Spectrum)

Far Distant (Larger Range) Communication◦ Cellular/Mobile Communications◦Wireless Computer Networks◦ Radar Communication◦ Satellite Communication◦ Broadcasting (Analog/Digital)

TVs Radios

Wireless Communications (Modes/Types)

Near (Shorter Distance) Communication◦Bluetooth◦Infrared

Wireless Communications (Modes/Types)

Wireless Local Area Networks (WLANs)

Wireless Wide Area Networks (WWANs)

Wireless Communications (Computer Networks)

A LAN with every end device/node having wireless access to share hardware, software and other devices and Resources.

Wireless Communications (Computer Networks: WLANs)

other devices

End devices

End devices

End devices

Infrared (IR) LANs

Spread Spectrum LANs

Wireless Communications (Computer Networks: WLANs: Transmission Techniques)

Limited to single room◦ b/c waves does not penetrate opaque walls

GHz to 400 THz Excellent potential for data transmission◦ Keyboard, mouse, Printers, and end devices can

communicate◦Original standard data rate of 75 kbps for a distance up

to 8 m. ◦The recent standard defines a data rate of 4 Mbps.

Wireless Communications (Computer Networks: WLANs: Transmission Techniques:

Infrared LANs)

IEEE 802.11 committee Standards Makes use of Spread Spectrum transmission

techniques. Most Popular type of WLAN Usable without having to go to licensing procedure◦Operates in ISM [Industrial, Scientific, and Medical {902-

928MHz (915MHz), 2.4-2.4835GHz (2.4GHz), 5.725-5.825GHz(5.8GHz)}] microwave band.

◦Higher the frequency, Higher the potential Bandwidth.

Wireless Communications (Computer NWs: WLANs: Transmission Techniques: Spread

Spectrum LANs)

Wireless Communications (Computer NWs : : : IEEE 802.11 Standard)

Access Point (AP) Basic Services Set (BSS) Coordination Function Distribution System Extended Services Set (ESS) MAC protocol data Unit (MPDU) MAC service Data Unit (MSDU) Station/Node/End Device

Wireless Communications (Computer NWs : : : IEEE 802.11 Components)

Access Point (AP)◦ Also called Wireless Access point (WAP) or central Base

Station.◦ a device that allows wireless communication devices to

connect to a wireless network using Wi-Fi, Bluetooth or related standards.

◦WAP or AP connects to router or any other Layer 3 device◦ Can perform switching function b/w wireless devices◦Wired devices can also be connected to it

Wireless Communications (Computer NWs : : : : Access Point)

Wireless Communications (Computer NWs : : : : Access Point)

A typical Wireless Access Point

Basic Services Set (BSS)◦Building block of a wireless LAN.◦ is made of stationary or mobile wireless stations and an

optional central base station, also known as the access point (AP).

*A BSS without an AP is called an ad hoc network A BSS with an AP is called an infrastructure network.

Wireless Communications (Computer NWs : : : : Basic Services Set)

Access Point is Optional Without Access point stations still can

communication

Wireless Communications (Computer NWs : : : : Basic Services Set)

Coordination Function◦ logical function◦Uses CSMA techniques with CA◦Determines when a station is permitted to transmit

and may able to receive the PDU. Distribution Function◦ A system used to interconnect

A set of BSSs & integrated LAN to create ESS

Wireless Communications (Computer NWs : : : : Coordination and Distribution Function)

An Extended service set (ESS) ◦ is made up of two or more BSSs with APs. In this case, the

BSSs are connected through a distribution system, which is usually a wired LAN.

◦ The distribution system connects the APs in the BSSs. ◦ IEEE 802.11 does not restrict the distribution system;

it can be any IEEE LAN such as an Ethernet.

Wireless Communications (Computer NWs : : : : Extended Services set)

MAC Protocol Data Unit (MPDU)◦ The unit of data exchanged b/w two peer MAC entities using the

services of the physical layer.

MAC Protocol Data Unit (MSDU) ◦ Information that is delivered to the user.

Stations ◦ Any device that contains an IEEE 802.11 conformant MAC and

Physical layer.

Wireless Communications (Computer NWs : : : : MPDU, MSDU & Stations)

Wireless Communications (Computer NWs : : : : Collecting All)

ESS

IEEE 802.11x LAN

Wireless Communications (Computer NWs : : : : CSMA/CA)

ESS

Carrier Sense Multiple Access with Collision Avoidance CSMA/CA

Increase in Portable Devices Simplicity and Flexibility Reliable and Secure Higher Data Rates, Speed and Reach Technology Cost Savings Trend

Wireless Communications (Computer NWs : : : : Why Wireless..?)

Data less secure

The waves could be damaging to our health

Modulation technique required for efficient transmission.

Wireless Communications (Computer NWs : : : : Why not Wireless)

Authentication◦ A function that determines whether a Station is allowed to

participate in network communication.

Implementing network encryption Security Protocols◦WEP (Wireless Equivalency protocol)◦WPA (Wireless Protected Access)

Wireless Communications (Security)

Data is In Air◦ Even with Encryption creative minded hackers can sniff

your data and corporate confidential information.

◦Even with encryption, the data between client and AP’s are available for anyone to capture.

◦Danger for Humanity…

Wireless Communications (Issues)

An Adhoc network is a peer-to-peer network (no central device) set up temporarily to meet some immediate needs.

When all station are mobile stations, with no connection to other BSSs, the BS is called IBSS(Independent BSS), some times referred as Ad hoc network…

In simple words, it is decentralized network…

Wireless Communications (Adhoc Networks)

Wireless Communications (Adhoc Networks)

For Me & rest of the class, Are you feeling like it after all..?

◦Welcome Questions!

The End (Thanks for bearing me!)

?

The World Wide web (Internet)◦ Wikipedia-The Free Encyclopedia

http://www.wikipedia.org/en◦ IEEE

http://www.ieee.org◦ ACM

http://www.acm.org Books◦ Computer Networks

Tanebaum S. Andrew 4th ed.◦ Data Communications and Networking

Forozon A. Behrouz 4th ed.◦ Data and Computer Communications

Stallings William 6th ed.

References