EC312 Lesson 24: Wireless Technologies
Objectives:
a. Define Wireless Local Area Network (WLAN) and Personal Area Networks (PAN) and
some of the technologies and their applications.
b. Discuss the standards for Wi-Fi 802.11 and the history of the different protocols and
their specific characteristics.
c. Describe the differences between Blutooth and Wi-Fi and their advantages and
disadvantages.
d. Describe the differences between Blutooth and ZigBee.
e. Perform a Man in the Middle Attack Lab using 3 Xbees .
Communication is going wireless with the all of the smart mobile devices such as laptops,
cellular phones, PDA, tablets etc. We will not concentrate on the cell phone technologies
(Chapter 20). The history and development of the different generations of digital cell phone
technology is really interesting technically. At this point you all have the background to
understand the ideas of multiple access techniques for cell phone subscribers (CDMA=DSSS)
and the bandwidth constraints, which dictate new modulation schemes (/4-DQPSK), but we
won’t be including them in this discussion.
In order to move our networks from wires to wireless and to stream data wirelessly among
the mobile devices, a number of protocols have been formulated such as Wi-Fi, Bluetooth,
Zigbee, NFC etc. Using these technologies users can exchange all sorts of information at high
speeds. The speed of data transfer and the reliability of the data exchanged depends on the
application. These data exchange protocols have significantly different rule stacks and vary a lot
in terms of range, power, device application etc.
Chapter 21 (Wireless Technologies) in our book outlines the more widely used wireless
systems and applications besides cell phones. And it is a very good resource for this topic, so the
notes that follow provide an outline of the material, but we will emphasize mainly Wi-Fi,
Bluetooth, and ZigBee.
Range vs data rate: common wireless technologies
Wireless LAN
 Local-area networks (LANs) within a company or an organization are still interconnected
mainly by CAT5 or CAT6 twisted pair.
 Wireless extensions and even complete wireless LANs have become more common now
that reliable, low-cost wireless modems are available.
 Wireless is a great way to expand an existing network.
What makes the wireless LAN so appealing is that it offers flexibility, convenience, and
lower costs.
Hardware of Wireless LANs
 The hardware devices in a wireless LAN are the access point or the
gateway/router and the radio modems in the PCs.
 The access point is a box containing a transceiver that interfaces to an existing
LAN by way of CAT5/6 wiring.
 It gets its dc operating power via the twisted-pair cabling.
 The IEEE 802.3af standard related to furnishing dc power over the network cable
is referred to as Power over Ethernet (PoE).
 The other PCs and devices link to the gateway/router wirelessly.
Wireless LAN Standards
 One standard for wireless LANs has emerged as the most flexible, affordable, and
reliable.
 Known as the IEEE 802.11 standard, it is available in multiple forms for different
needs.
 The earliest useful and most widely adopted version of the 802.11 standard is
802.11
RF (Radio Frequency) Used for WLAN
900 MHz legacy
2.4 GHz ISM Band (Industrial, Scientific, and Medical)
5 GHz UNII Band (Unlicensed National Information Infrastructure)
 Infrared
Limited Use due to poor propagation.
IEEE802.11b
 Frequency Range – 2.4 GHz ISM Band (bandwidth of 83.5MHz)
 Theoretical Data Rate – 11 Mbps
In Reality achieve 4 Mbps
Increasing range or noise causes the rate to automatically drop off to 5.5, 2, or 1
Mbps, which helps ensure a reliable connection despite the lower speed.
Data Rate Loss due to MAC Layer Inefficiencies
 Signal Technique –access method-Direct Sequence Spread Spectrum with Single Carrier
 Production Began in 1999
 Was the most Common WLAN in use
 11 Channels in the 2.4GHz ISM band, 22 MHz per channel
 1 Watt Max Power Output
IEEE802.11a
 Frequency Range – 5 GHz UNII Band
 Theoretical Data Rate – 54 Mbps
In Reality achieve 38 Mbps
 Signal Technique – Orthogonal Frequency Division Multiplexing with multiple carriers
 Production Began in 2001
 Quickly replacing 802.11b due to Higher Data Rate
 12 Channels, 20 MHz per channel
 30 mW Max Power Output
The newest standard is the IEEE802.11n version.
 Frequency Range – 2.4 GHz ISM Band
 Theoretical Data Rate – 600 Mbps
 Signal Technique – Orthogonal Frequency Division Multiplexing with multiple carriers
 A primary feature of this standard is the use of multiple-input multiple-output (MIMO)
antenna systems to improve reliability of the link.
APs for 802.11n use two or more transmit antennas and three or more receive antennas. The
wireless nodes use a similar arrangement. In each case multiple transceivers are required for the
AP and the node.
MIMO systems reduce multipath problems and extend the range and reliability of the
wireless link.
Wireless LAN Standards: Wireless Security
 The 802.11 standard also includes provision for encryption to protect the privacy of
wireless users.
 Since radio signals can literally be picked up by anyone with an appropriate receiver,
those concerned about privacy and security should use the encryption feature built into
the system.
 The basic security protocol is called Wired Equivalent Privacy (WEP) and uses the
RC4 encryption standard and authentication.
 WEP may be turned off or on by the user. It does provide a basic level of security;
however, WEP has been cracked by hackers and is not totally secure from the most
high-tech data thieves.
 Two stronger encryption standards called Wi-Fi Protected Access (WPA) and WPA2
are also available in several forms to further boost the encryption process.
 The IEEE also has a security standard called 802.11i that provides the ultimate in
protection.
WLAN Terms
 Basic Service Set – A number of wireless stations that constitutes a WLAN
 Basic Service Area- the coverage area of the stations in the BSS
 Extended Service Set – A group of BSS’s
 Distribution System – A Network that interconnects different BSS’s
 Access Point - a device that is capable of connecting non WLAN traffic with wired LAN
traffic
 Association - the process that a station must complete in order to join an AP
WLAN considerations
Personal-Area Networks-PANs
 A personal-area network (PAN) is a very small network that is created informally or on
an ad hoc basis.
 A PAN typically involves two or three nodes, but some systems permit many nodes to be
connected in a small area.
 PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth, a standard developed by the cell
phone company Ericsson for use as a cable replacement.
 Bluetooth is a digital radio standard that uses frequency-hopping spread spectrum (FHSS)
in the unlicensed 2.4-GHz ISM band.
 Three levels of transmission power have been defined, depending upon the application.
 Bluetooth transceivers are available as single-chip transceivers that interface to the device
to be part of a PAN.
 Bluetooth transceivers send out search signals and then listen for nearby Bluetoothequipped devices.
 If another Bluetooth device comes into range, the two Bluetooth devices automatically
interconnect and exchange data.
 These devices form what is called a piconet, the linking of one Bluetooth device that
serves as a master controller to up to seven other Bluetooth slave devices.
 Bluetooth devices can also link to other piconets to establish larger scatternets.
Bluetooth piconet with scatternet link.
Up to seven devices can be actively connected.
Bluetooth and WiFi are different standards for wireless communication.
Bluetooth technology is useful when transferring information between two or more devices
that are near each other when speed is not an issue, such as telephones, printers, modems
and headsets. It is best suited to low-bandwidth applications like transfering sound data
with telephones (i.e. with a Bluetooth headset) or byte data with hand-held computers
(transferring files) or keyboard and mice.
Wi-Fi is better suited for operating full-scale networks because it enables a faster
connection, better range from the base station, and better security (if configured properly)
than Bluetooth.
Comparison chart
Bluetooth
Wifi
2.4 GHz
2.4, 3.6, 5 GHz
Low
High
Low ( 800 Kbps )
High (11 Mbps )
Bluetooth SIG
IEEE, WECA
It is less secure
Security issues are already being debated.
1994
1991
Mobile phones, mouse, keyboards, office and
industrial automation devices
Notebook computers, desktop computers, servers, TV,
Latest mobiles.
Bluetooth adaptor on all the devices
connecting with each other
Wireless adaptors on all the devices of the network, a
wireless router and/or wireless access points
5-30 meters
With 802.11b/g the typical range is 32 meters indoors
and 95 meters (300 ft) outdoors. 802.11n has greater
range. 2.5GHz Wi-Fi communication has greater range
than 5GHz. Antennas can also increase range.
Low
High
Fairly simple to use. Can be used to connect up
to seven devices at a time. It is easy to switch
between devices or find and connect to any
device.
It is more complex and requires configuration of
hardware and software.
Latency
200ms
150ms
Bit-rate
2.1Mbps
600 Mbps
Frequency
Cost
Bandwidth
Specifications
authority
Security
Year of
development
Primary Devices
Hardware
requirement
Range
Power
Consumption
Ease of Use
ZigBee: Another PAN
 ZigBee is the commercial name for another PAN network technology based on the IEEE
802.15.4 wireless standard.
 Like Bluetooth, it is a short-range technology with networking capability.
 It was designed primarily for commercial, industrial, and home monitoring and control
applications.
 ZigBee is designed to operate in the license-free spectrum.
 There are three basic bands and versions (below).
 Data rates are low, but most applications are simply transmitting sensor data or making
simple on/off operations.
 ZigBee’s virtue is its versatile networking capability.
 The standard supports three topologies: star, mesh, and cluster tree. The most commonly
used are the star and mesh.
 These network topologies are made up of three types of ZigBee nodes:
ZigBee coordinator (ZC)
ZigBee router (ZR)
ZigBee end device (ZED).
 ZigBee can address a wide range of wireless needs.
 It was designed primarily for monitoring and control.
 Monitoring refers to looking at a wide range of physical conditions, especially
temperature, humidity, pressure, the presence of light, speed, and position information.
 Control refers to the sending of command signals to initiate some action.
 Typically commands are used to turn things off and on, such as lights, motors, solenoids,
relays, and other devices.
 Popular applications of ZigBee include:
Monitoring and controlling lights;
Heating, ventilating, and air conditioning (HVAC) systems in large buildings;
Industrial monitoring and control in factories, chemical plants, and manufacturing operations.
Automatic electric and gas meter reading.
Medical uses, such as wireless patient monitoring.
Automotive sensor systems.
Military battlefield monitoring.
Consumer applications such as home monitoring and control, remote control of other objects,
and security.
XBee microcontroller will be used in our Lab to run ZigBee protocol
Features
 802.15.4/Multipoint network topologies
 250 Kbs data transmission
 Pulse Width Modulation (PWM) unit
 6 channel Analog to Digital converter
 9 Digital Inputs/Outputs
 Built-in networking
 Sleep mode (awake on event)
 Can talk one-to-one, or one-to-many
 Very low power operation
 64 bit address
 Automatically form a network without user intervention
 ZigBee protocol takes care of retries, acknowledgements and data message routing
 Ability to self-heal the network (message rerouting)
XBee Serial Communications