Wireless Communications

Low Rate Wireless Personal Area Networks

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Objectives

• Describe a wireless personal area network (WPAN)

• List the different WPAN standards and their applications

• Explain how IrDA, Bluetooth, and ZigBee work

• Describe the security features of low-rate WPAN technology

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What is a WPAN?

• Wireless personal area network (WPAN)– Group of technologies that are designed for short-

range communications– Eliminates the need for wires or cables to

interconnect multiple devices

• Applications for WPAN technology include:– Synchronizing PDAs, cellular, and Smartphones– Home control systems (smarthome)– Cordless telephones– Portable device data exchange

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What is a WPAN? (continued)

• Applications for WPAN technology include (continued):– Industrial control systems– Location — smart tags used to locate people at home

or at the office– Security systems– Interactive toys– Inventory tracking

• Advantages– WPAN devices use very little power– Short range helps maintain security and privacy

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Infrared WPANs (IrDA)

• Most common infrared connection today – Based on the IrDA specifications

• IrDA specifications– Define both physical devices and network protocols

• IrDA devices’ characteristics– Provide walk-up connectivity– Provide a point-to-point method of data transfer

• Between only two devices at a time

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Infrared WPANs (IrDA) (continued)

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Infrared WPANs (IrDA) (continued)

• Serial Infrared (Version 1.0)– Designed to work like the standard serial port on a PC– Uses a UART (Universal Asynchronous

Receiver/Transmitter)• Microchip that also controls a computer’s serial interface

• Fast Infrared (FIR) (Version 1.1)– Extends the data rate to 4 Mbps– When two IrDA devices first communicate

• They both transmit using SIR

• Then they shift to FIR speed

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RF WPANs

• Offer functionality beyond that of IR devices

• Include– Bluetooth– 802.15.4 (ZigBee)

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IEEE 802.15.1 and Bluetooth

• Industry specification– Bluetooth Special Interest Group (SIG)

• Defines small-form-factor, low-cost wireless radio communications

• IEEE licensed this wireless technology– To adapt and copy a portion of the specification as the

base material for 802.15.1

• 802.15.1 standard– Approved in March 2, 2002– Fully compatible with Bluetooth version 1.1

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Bluetooth Protocol Stack

• Bluetooth RF layer– Defines how the basic hardware that controls the radio

transmissions functions– Data bits (0 and 1) are converted into radio signals

and transmitted

• Radio module– A single radio transmitter/receiver (transceiver)– Only hardware required for Bluetooth to function– Bluetooth can transmit at a speed of up to 1 Mbps– Bluetooth version 2.0 transmits at 2 or 3 Mbps

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Bluetooth Protocol Stack (continued)

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Bluetooth Protocol Stack (continued)

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Bluetooth Protocol Stack (continued)

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Bluetooth Protocol Stack (continued)

• Network topologies (continued)– Scatternet

• Group of piconets in which connections exist between different piconets

– To communicate in each different piconet• Device must use the master device address and clock

of that specific piconet

– Bluetooth device can be a slave in several piconets • But can be a master in only one piconet

– A master and slave can switch roles in a piconet

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Bluetooth Link Manager Layer (continued)

• Link between Bluetooth devices (continued)– Bluetooth power usage (continued)

• Power-saving modes

– Active

– Sniff

– Hold

– Park

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Low Rate WPAN Security• Security should be of little concern with WPANs• One of the most serious concerns is social

engineering• Designing security in WPANs

– Much more difficult task than in other networking technologies

• Public key infrastructure (PKI)– Unique security code, or key, provided by a certificate

authority

• Certificate authority– Private company that verifies the authenticity of users

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Security in Infrared WPANs

• Limited to the line-of-sight characteristic of this type of connection

• IrDA specification makes no provision for encrypting data or protecting the connection– Users may encrypt a file before exchanging it

• IrDA devices support open access– So that anyone can transmit files without first notifying the

device’s owner• Open access can be a major security concern• Bluetooth provides security at the LMP layer

– Using authentication• Authentication is based on identifying the device itself• Authentication scheme is a challenge-response strategy• Encryption is the process of encoding communications

– And ensures that the transmissions cannot be easily intercepted and decoded

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Summary

• The most common infrared connection today is based on the IrDA standard– IrDA devices cannot send and receive at the same

time– IrDA is easy to use

• Bluetooth is a wireless technology that uses short-range radio frequency (RF) transmissions– Supported by over 2,500 hardware and software

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