IT602 • Wireless and Mobile Computing

Unit 3 WLAN, HIPERLAN and Bluetooth

Complete exam-oriented notes on IEEE 802.11 architecture, 802.11a/b/g, protocol layers, MAC management, HIPERLAN and Bluetooth.

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1. Introduction to Wireless LAN

A Wireless Local Area Network connects devices within a limited area using radio waves instead of physical cables.

Advantages

  • Mobility
  • Easy installation
  • Flexible expansion
  • Reduced cabling
  • Support for portable devices

Limitations

  • Interference
  • Security threats
  • Variable signal strength
  • Shared bandwidth

2. IEEE 802.11 LAN Architecture

IEEE 802.11 defines standards for wireless local area networks.

Main Components

  • Station: device with wireless capability.
  • Access Point: connects wireless stations with the distribution system.
  • BSS: Basic Service Set.
  • IBSS: Independent Basic Service Set or ad hoc network.
  • ESS: Extended Service Set formed by connected BSSs.
  • Distribution System: interconnects access points.
Station --\ Access Point ---- Distribution System ---- Access Point Station --/ /-- Station \-- Station

3. IEEE 802.11a, 802.11b and 802.11g

StandardBandMaximum Data RateTechnique
802.11a5 GHz54 MbpsOFDM
802.11b2.4 GHz11 MbpsDSSS
802.11g2.4 GHz54 MbpsOFDM

Comparison

  • 802.11a offers less interference but shorter range.
  • 802.11b provides lower speed but wider compatibility.
  • 802.11g combines 2.4 GHz coverage with higher speed.

4. IEEE 802.11 Protocol Architecture

Logical Link Control | MAC Layer | Physical Layer Convergence Procedure | Physical Medium Dependent Layer

The MAC layer manages access to the shared medium, while the physical layer performs transmission, modulation and radio signaling.

5. IEEE 802.11 Physical Layer

Functions

  • Signal transmission and reception
  • Modulation and coding
  • Carrier sensing
  • Channel selection
  • Data-rate control

Techniques

  • Frequency Hopping Spread Spectrum
  • Direct Sequence Spread Spectrum
  • Infrared transmission
  • Orthogonal Frequency Division Multiplexing

6. IEEE 802.11 MAC Layer

The MAC layer controls access to the shared wireless channel and provides reliable frame delivery.

Coordination Functions

  • DCF: Distributed Coordination Function based on CSMA/CA.
  • PCF: Point Coordination Function using centralized polling.

CSMA/CA Working

  1. Station senses the channel.
  2. If idle, it waits for an inter-frame space.
  3. A random backoff value is selected.
  4. Frame is transmitted when the counter reaches zero.
  5. Receiver sends acknowledgement.

RTS/CTS

Request to Send and Clear to Send reduce the hidden-terminal problem.

7. MAC Management

Association

A station connects with an access point and becomes a member of its BSS.

Reassociation

A station changes from one access point to another.

Disassociation

The relationship between a station and access point is terminated.

Authentication

The station proves its identity before joining the network.

Power Management

Stations may enter sleep mode and wake periodically to receive buffered frames.

Scanning

  • Passive scanning
  • Active scanning

8. HIPERLAN

HIPERLAN stands for High Performance Radio Local Area Network. It was developed as a high-speed European WLAN standard.

Features

  • High data rate
  • Support for multimedia traffic
  • Quality of Service
  • Centralized channel access
  • Operation in the 5 GHz band

Protocol Architecture

Higher Layers | Convergence Layer | Data Link Control | MAC Sublayer | Physical Layer

9. HIPERLAN Physical, Access Control and MAC Sublayers

Physical Layer

  • Radio transmission
  • Modulation
  • Channel coding
  • Synchronization

Access Control Sublayer

Controls medium access, scheduling and resource allocation.

MAC Sublayer

  • Frame creation
  • Addressing
  • Error detection
  • Priority handling
  • Quality-of-Service support

10. Bluetooth User Scenarios

Bluetooth is a short-range wireless technology used to connect personal devices.

Common Scenarios

  • Wireless headset
  • File transfer
  • Keyboard and mouse
  • Phone-to-car connection
  • Personal area networking
  • Smart home and IoT devices

Piconet and Scatternet

  • Piconet: small network controlled by one central device.
  • Scatternet: two or more interconnected piconets.

11. Bluetooth Physical Layer

  • Operates in the 2.4 GHz ISM band.
  • Uses frequency hopping to reduce interference.
  • Divides the channel into time slots.
  • Supports short-range, low-power communication.
  • Uses adaptive frequency hopping in newer implementations.
Device A )) Frequency-Hopping Radio Link (( Device B

12. Bluetooth MAC Layer

The Bluetooth MAC function is mainly handled by the baseband and link-management procedures.

Functions

  • Device addressing
  • Time-slot control
  • Frequency-hop synchronization
  • Connection establishment
  • Error control
  • Power management
  • Security support

Link Types

  • SCO: synchronous connection-oriented link for voice.
  • ACL: asynchronous connectionless link for packet data.

Unit 3 Summary

  • IEEE 802.11 defines WLAN architecture and operation.
  • A BSS contains stations and may include an access point.
  • 802.11a, b and g differ in band, speed and modulation.
  • The MAC layer uses CSMA/CA and acknowledgement.
  • MAC management includes association, authentication and power saving.
  • HIPERLAN provides high-speed WLAN and QoS support.
  • Bluetooth creates short-range personal networks using frequency hopping.

Important RGPV Exam Questions

Long Answer Questions

  1. Draw and explain IEEE 802.11 LAN architecture.
  2. Compare IEEE 802.11a, 802.11b and 802.11g.
  3. Explain IEEE 802.11 protocol architecture.
  4. Explain the IEEE 802.11 physical layer.
  5. Explain the IEEE 802.11 MAC layer and CSMA/CA.
  6. Explain MAC management functions.
  7. Draw and explain HIPERLAN protocol architecture.
  8. Explain HIPERLAN physical, access control and MAC sublayers.
  9. Explain Bluetooth user scenarios, piconet and scatternet.
  10. Explain Bluetooth physical and MAC layers.

Short Answer Questions

  1. Define BSS.
  2. What is ESS?
  3. What is DCF?
  4. What is RTS/CTS?
  5. Define HIPERLAN.
  6. What is a piconet?
  7. What is SCO?
  8. What is ACL?
Exam Strategy: Prepare architecture diagrams, standard comparison tables and step-by-step CSMA/CA working.

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Frequently Asked Questions

IEEE 802.11 is a family of standards for wireless local area networks.
A BSS is one basic wireless service area, while an ESS connects multiple BSSs through a distribution system.
It helps avoid collisions because wireless stations cannot reliably detect collisions while transmitting.
HIPERLAN is a European high-performance wireless LAN standard.
A piconet is a small Bluetooth network in which one central device coordinates connected devices.