1. CWNA Guide to Wireless LANs, Second Edition
Chapter Twelve
Personal, Metropolitan, and Wide Area Wireless Networks

2. Objectives Define a wireless personal area network
List the technologies of a wireless metropolitan area network
Describe the features of a wireless wide area network
Discuss the future of wireless networking
CWNA Guide to Wireless LANs, Second Edition

3. Wireless Personal Area Networks
Wireless networks classified into four broad categories:
Wireless personal area network (WPAN): Hand-held and portable devices; slow to moderate transmission speeds
Wireless local area network (WLAN): i.e., IEEE a/b/g
Wireless metropolitan area network (WMAN): Range up to 50 kilometers
Wireless wide area network (WWAN): Connects networks in different geographical areas
CWNA Guide to Wireless LANs, Second Edition

4. Wireless Personal Area Networks (continued)
Figure 12-1: Wireless network distances
CWNA Guide to Wireless LANs, Second Edition

5. Wireless Personal Area Networks (continued)
Figure 12-2: Point-to-point transmission
CWNA Guide to Wireless LANs, Second Edition

6. Wireless Personal Area Networks (continued)
Figure 12-3: Point-to-multipoint transmission
CWNA Guide to Wireless LANs, Second Edition

7. Wireless Personal Area Networks (continued)
WPANs encompass technology designed for portable devices
PDAs, cell phones, tablet or laptop computers
Low transmission speeds
Three main categories:
IEEE standards
Radio frequency ID (RFID)
IrDA
CWNA Guide to Wireless LANs, Second Edition

8. Bluetooth
Although Bluetooth is one of the most widely anticipated wireless technology of past ten years, its future is uncertain
It holds great promise for sending and receiving radio frequency signals between PDAs, cell phones, and notebook computers, but its acceptance has been much slower than predicted because of technological and economic considerations
CWNA Guide to Wireless LANs, Second Edition

9. What is Bluetooth?
Wireless technology using short-range radio frequency (RF) transmissions
Designed by Ericsson in 1994 for cellular phones
Allows users to connect a wide range of computing and telecommunications devices without cables
Provides on-the-fly connections between devices
CWNA Guide to Wireless LANs, Second Edition

10. How Bluetooth Is Used
Low-powered wireless data and voice transmission technology
Smart technology that can recognize another Bluetooth device within range and automatically synchronize
Examples include cellular telephones that automatically dial Internet Service Provider (ISP), and download to notebook computer in briefcase or send audible message
See Figure 5-1
CWNA Guide to Wireless LANs, Second Edition

11. Bluetooth Scenario
CWNA Guide to Wireless LANs, Second Edition

12. Bluetooth vs. IrDA
Each with pluses and minuses, these two technologies complement one another more than compete with each other
IRDA has limited range and narrow angle
See Figure 5-2
Bluetooth is omnidirectional and can synchronize while user is mobile
See Figure 5-3
CWNA Guide to Wireless LANs, Second Edition

13. IrDA Transmission
CWNA Guide to Wireless LANs, Second Edition

14. Bluetooth Transmission
CWNA Guide to Wireless LANs, Second Edition

15. Bluetooth SIG
Over 2500 hardware and software vendors make up Bluetooth Special Interest Group (SIG)
Develops technical specifications allowing interoperability across devices from different vendors
Administers test facilities to ensure devices conform to standards
Established 11 working subgroups
Working with IEEE to make Bluetooth technology an IEEE standard
CWNA Guide to Wireless LANs, Second Edition

16. How Bluetooth Works Robust radio frequency technology
Overall Bluetooth protocol stack
Lower levels use hardware
Upper levels use software
See Figure 5-4
Specific layers have different functions
CWNA Guide to Wireless LANs, Second Edition

17. Bluetooth Protocol Stack
CWNA Guide to Wireless LANs, Second Edition

18. RF Layer Lowest level of Bluetooth protocol stack
Defines basic hardware that controls radio transmissions functions
Converts data bits into radio signals that are transmitted and received
CWNA Guide to Wireless LANs, Second Edition

19. Radio Module
Only hardware required is single tiny chip called Bluetooth radio module
See Figure 5-5
Added during manufacturing process
Device ready to work right out of the box
Characteristics of radio module
Performs all functions by single chip
As generic as possible
Low-cost
Minimum of supporting off-chip components
CWNA Guide to Wireless LANs, Second Edition

20. Bluetooth Transceiver
CWNA Guide to Wireless LANs, Second Edition

21. Functional Block Design of Bluetooth Transceiver
Figure 5-6 shows functional block design of Bluetooth transceiver
Can interface through various connections
UART (Universal Asynchronous Receiver/ Transmitter) serial port connection
USB (Universal Serial Bus) connection
PCI (Peripheral Component Interface) connection
CWNA Guide to Wireless LANs, Second Edition

22. Functional Block Diagram of a Bluetooth Transceiver
CWNA Guide to Wireless LANs, Second Edition

23. Bluetooth Speed See Table 5-1
Version 1.1 transmits at speed of 1 Mbps
Next generation should send and receive at 2 Mbps
See Table 5-1
CWNA Guide to Wireless LANs, Second Edition

24. Connection Speeds
CWNA Guide to Wireless LANs, Second Edition

25. Power Classes Three Bluetooth power classes
Divisions based on power level measured in milliwatts and maximum distance
See Table 5-2
Most Bluetooth devices are Power Class 2 with a maximum distance of 33 feet or 10 meters
CWNA Guide to Wireless LANs, Second Edition

26. Power Classes
CWNA Guide to Wireless LANs, Second Edition

27. Bluetooth Power Consumption
Since most bluetooth devices are mobile and use battery power, it is essential to conserve power
Bluetooth power consumption measured in milliamps
For data transmission, devices use only 6 milliamps; batteries last for 120 hours
For voice transmission, devices use only 10 milliamps; batteries last for 75 hours
During standby, devices use .3 milliamps; batteries last for 3 months
CWNA Guide to Wireless LANs, Second Edition

28. Modulation Technique
RF layer defines modulation technique
Bluetooth uses two-level Gaussian frequency shift keying (2-GFSK), a variation of frequency shift keying (FSK)
Two different frequencies indicate whether a 1 or a 0 is being transmitted
Amount of frequency variation, called modulation index, is between 280 KHz and 350 KHz
Frequency decreases to represent a 0 and increases to represent a 1
Figure 5-7 shows a 2-GFSK sine wave
CWNA Guide to Wireless LANs, Second Edition

29. 2-GFSK
CWNA Guide to Wireless LANs, Second Edition

30. Baseband Layer Manages physical channels and links Handles packets
Does paging and inquiry to access and inquire about Bluetooth devices in area
CWNA Guide to Wireless LANs, Second Edition

31. Radio Frequency
Bluetooth operates in 2.4 GHz Industrial, Scientific, and Medical (ISM) band
Divides ISM band into 79 different frequencies, called channels, spaced 1 MHz apart
Uses frequency hopping spread spectrum (FHSS)
See Figure 5-8
CWNA Guide to Wireless LANs, Second Edition

32. Bluetooth FHSS
CWNA Guide to Wireless LANs, Second Edition

33. Solving Incompatibilities
Bluetooth version 1.0b defines a second hop count to avoid 2.4 GHz spectrum that some countries have allocated to other purposes
Divides the frequency into 23 channels, making it incompatible with devices that use 79 channels
Bluetooth SIG negotiated with countries to free up 2.4 GHz spectrum
Devices conforming to current 1.1 version use 79 channels and are completely compatible
CWNA Guide to Wireless LANs, Second Edition

34. Conflict with IEEE b
Bluetooth and IEEE b WLANs use same frequency
Several possible solutions
Add special software to WLAN to cause silence when Bluetooth communication is detected
IEEE working on new standard that lets Bluetooth and b devices function better in shared space
CWNA Guide to Wireless LANs, Second Edition

35. Network Topology Two types of Bluetooth network topologies
Piconet
Scatternet
Two Bluetooth devices within range automatically connect
One device is the master, controlling all wireless traffic
The other is the slave, taking commands from the master.
CWNA Guide to Wireless LANs, Second Edition

36. Piconets
A piconet is one master and at least one slave using the same channel
An active slave is sending transmissions
A passive slave is not actually participating
CWNA Guide to Wireless LANs, Second Edition

37. Five Different Modes
Devices in a piconet can be in one of five different modes
Standby—waiting to join a piconet
Inquire—looking for other devices
Page—master device is asking to connect to specified slave
Connected—either active slave or master is connected
Park/Hold—device is part of piconet, but in a low-power state
CWNA Guide to Wireless LANs, Second Edition

38. Bluetooth Addresses and Timing
Each Bluetooth device is preconfigured with addresses used when participating in piconet
See Table 5-3 for three significant addresses
Devices in piconet must change frequencies at same time and in same sequence
Master device’s clock determines timing, called phase, in hopping sequence
See Figure 5-10
CWNA Guide to Wireless LANs, Second Edition

39. Piconet Radio Module Addresses
CWNA Guide to Wireless LANs, Second Edition

40. Bluetooth Time Slots
CWNA Guide to Wireless LANs, Second Edition

41. Connection Process Bluetooth devices use two-step connection process
Inquiry procedure lets a device discover other devices in range and determine their addresses and clocks, as seen in Figure 5-11
The first device within range that responds with its own ID and clock receives a confirmation from the inquiring device, as seen in Figure 5-12
CWNA Guide to Wireless LANs, Second Edition

42. Device A Inquiry
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43. Response and Confirmation
CWNA Guide to Wireless LANs, Second Edition

44. Collision
If two devices simultaneously transmit, a collision occurs and data becomes corrupted
See Figure 5-13
Each device waits a random number of time slots and starts listening for inquiries again.
Device with shorter time will likely receive inquiry, respond, and receive a confirmation
See Figure 5-14
Eventually, inquiring device will learn address and timing of all devices in range
CWNA Guide to Wireless LANs, Second Edition

45. Collision
CWNA Guide to Wireless LANs, Second Edition

46. Response after Random Wait
CWNA Guide to Wireless LANs, Second Edition

47. The Paging Procedure
After inquiry is complete, next step is paging procedure which establishes an actual connection
Unit that establishes a connection automatically becomes master of the piconet
See Figure 5-15
CWNA Guide to Wireless LANs, Second Edition

48. Piconet
CWNA Guide to Wireless LANs, Second Edition

49. Scatternet
Multiple piconets can cover same area with different master and hop sequences
Device can be a member of two or more overlaying piconets
Group of piconets connected together is called a scatternet, as seen in Figure 5-16
Communication among piconets occurs using master device address and clock for each piconet
Bluetooth device can be a slave in several piconets, but master in only one
CWNA Guide to Wireless LANs, Second Edition

50. Scatternet
CWNA Guide to Wireless LANs, Second Edition

51. Bluetooth Frames Bluetooth frame has three parts See Figure 5-17
Access code (72 bits)—used for timing synchronization, paging, and inquiry
Header (54 bits)—used for packet acknowledgement, packet numbering, slave address, type of payload, and error checking
Payload ( bits)—contains data, voice, or both
See Figure 5-17
CWNA Guide to Wireless LANs, Second Edition

52. Bluetooth Frame
CWNA Guide to Wireless LANs, Second Edition

53. Link Manager Protocol (LMP) Layer
Two major duties of Link Manager
Managing piconet
Performing security
Piconet management includes
Regulating steps for attaching and detaching slaves from master
Establishing links between devices
CWNA Guide to Wireless LANs, Second Edition

54. SCO Link
Synchronous connected-oriented (SCO) link is used primarily for voice transmission at a speed of 64 Kbps
Symmetrical point-to-point connection between a master and a single slave
A master can support up to three simultaneous SCO links while slaves can support two or three SCO links
CWNA Guide to Wireless LANs, Second Edition

55. ACL Link
Asynchronous connection-less (ACL) link is used for data transmission
Packet-switched link from one master to all slaves on piconet
Also called point-to-multipoint link
Only one ACL link can exist
CWNA Guide to Wireless LANs, Second Edition

56. Three Kinds of Error Correction Schemes
1/3 rate Forward Error Correction (FEC)
Every bit is repeated three times for redundancy
2/3 rate FEC
Uses mathematical formula to add extra error correction bits to data
Automatic Retransmission Query (ARQ)
Certain data fields are retransmitted continuously until acknowledgement is received or timeout value is exceeded
CWNA Guide to Wireless LANs, Second Edition

57. Four Connection Modes
Active Mode—unit participates on channel
Master schedules transmissions while active slaves listens
Sniff Mode—slave listens to master at reduced rate that uses less power
Hold Mode—master puts slave unit in hold mode where only slave’s internal timer is running
Park Mode—most effective power saving mode
Device is still synchronized to piconet, but it does not participate in traffic
CWNA Guide to Wireless LANs, Second Edition

58. Security LMP layer provides security and encryption services
Security in piconet involves identifying device itself, not who is using device
Three levels of security
Level 1—No security
Level 2—Service-level security is established after connection is made
Level 3—Link-level security is performed before a connection is made
CWNA Guide to Wireless LANs, Second Edition

59. Authentication
Authentication involves verifying that a device should be allowed to join piconet
Bluetooth uses a challenge-response strategy to confirm that other device knows a shared identical secret key
Figure 5-18 illustrates authentication scheme
Version 1.1 improves authentication process by first confirming roles of master and slave before generating response number
CWNA Guide to Wireless LANs, Second Edition

60. Authentication
CWNA Guide to Wireless LANs, Second Edition

61. Encryption
Encoding communications ensures that transmissions cannot be intercepted and decoded
Three encryption modes
Encryption Mode 1—Nothing is encrypted
Encryption Mode 2—Traffic from master to one slave is encrypted, but traffic from master to multiple slaves is not
Encryption Mode 3—All traffic is encrypted
See Figure 5-19
CWNA Guide to Wireless LANs, Second Edition

62. Encryption
CWNA Guide to Wireless LANs, Second Edition

63. Other Layers and Functions
L2CAP is logical link control layer
Responsible for segmenting and reassembling data packets
Uses RFCOMM (Radio Frequency Virtual Communications Port Emulation) data protocol
Provides serial port emulation for Bluetooth data, making it appear to have been sent through computer’s standard serial port
Transmits control information
CWNA Guide to Wireless LANs, Second Edition

64. Bluetooth Issues Many challenges face Bluetooth Cost Limited support
Shortcomings in protocol itself
Positioning in marketplace
Conflicts with other devices in radio spectrum
CWNA Guide to Wireless LANs, Second Edition

65. Cost
Chips have decreased in price to about $15 from a high of over $75
Not advantageous to replace a $7 cable with a $15 chip
Many think cost must come down to about $5 before Bluetooth reaches competitive advantage
CWNA Guide to Wireless LANs, Second Edition

66. Limited Support Bluetooth is caught in “chicken or egg” scenario
Because of low market penetration, Bluetooth is not fully supported by hardware and software vendors
Users reluctant to purchase technology that is not fully supported
Microsoft is “straddling the fence”
Provides Bluetooth support for Pocket PC 2002
Does not support Bluetooth in Windows XP
CWNA Guide to Wireless LANs, Second Edition

67. Protocol Limitations
Major limitation is no hand-off between piconets
Unlike cell phone switching, Bluetooth connection is broken and must be restored with new master when device moves from one piconet area to another
Bluetooth provides less than optimal security by authenticating devices instead of users
Devices cannot determine how function of other devices can be used in cooperating setting
CWNA Guide to Wireless LANs, Second Edition

68. Market Position
Current position is between IEEE x WLANs and cell phones
WLAN is preferred technology for connecting wireless devices to form network
WLAN is mature, robust, flexible, popular technology
Trend today is fewer devices instead of more, and cell phones have integrated capabilities that Bluetooth lacks
CWNA Guide to Wireless LANs, Second Edition

69. Spectrum Conflict
The 2.4 GHz band that Bluetooth uses conflicts with IEEE b WLANs
WLAN may drop connection when detects another device sharing its frequency
Most obvious fix is moving Bluetooth device away from WLAN
Many vendors offer products that let Bluetooth and b WLANs share spectrum
New a WLAN standard uses a different frequency, eliminating the conflict
CWNA Guide to Wireless LANs, Second Edition

70. WPANs: IEEE 802.15.1 (Bluetooth)
Bluetooth uses short-range RF transmissions
Users can connect wirelessly to wide range of computing and telecommunications devices
Rapid and ad hoc connections between devices
adapted and expanded from Bluetooth
Designed for area of about 10 meters
Rate of transmission below 1 Mbps
Two types of network topologies
Piconet
Scatternet
CWNA Guide to Wireless LANs, Second Edition

71. WPANs: IEEE 802.15.1 (continued)
Piconet: When two devices come within range, automatically connect
Master: Controls wireless traffic
Slave: Takes commands from master
Piconet has one master and at least one slave
Active slave: Connected to piconet and sending transmissions
Parked slave: Connected but not actively participating
CWNA Guide to Wireless LANs, Second Edition

72. WPANs: IEEE 802.15.1 (continued)
Figure 12-4: Piconet
CWNA Guide to Wireless LANs, Second Edition

73. WPANs: IEEE 802.15.1 (continued)
Figure 12-5: Slave device detected by a master device
CWNA Guide to Wireless LANs, Second Edition

74. WPANs: IEEE 802.15.1 (continued)
Devices in piconet can be in one of five modes:
Standby: Waiting to join a piconet
Inquire: Device looking for devices to connect to
Page: Master device asking to connect to specific slave
Connected: Active slave or master
Park/Hold: Part of piconet but in low-power state
Scatternet: Group of piconets in which connections exist between different piconets
uses FHSS
CWNA Guide to Wireless LANs, Second Edition

75. WPANs: IEEE 802.15.1 (continued)
Figure 12-6: Scatternet
CWNA Guide to Wireless LANs, Second Edition

76. WPANs: IEEE 802.15.1 (continued)
Table 12-1: Comparison of speed
CWNA Guide to Wireless LANs, Second Edition

77. WPANs: IEEE 802.15.3 Created in response to limitations of 802.15.1
High-rate WPANs
Two main applications:
Video and audio distribution for home entertainment systems
High-speed digital video transfer
High-density MPEG2 transfer between video players/gateways and multiple HD displays
Home theater
PC to LCD projector
Interactive video gaming
High speed data transfer
CWNA Guide to Wireless LANs, Second Edition

78. WPANs: IEEE 802.15.3 (continued)
Differences between and
Quality of Service (QoS)
Security
High data rates
Spectrum utilization
Coexistence
Table 12-2: IEEE security modes
CWNA Guide to Wireless LANs, Second Edition

79. WPANs: IEEE 802.15.3 (continued)
a: Will support data transfers up to 110 Mbps between max of 245 devices at 10 meters
Ultrawideband (UWB)
Intended to compete with USB 2.0 and FireWire
IEEE b task group working on improving implementation and interoperability of
IEEE c task group developing alternative physical layer standard that could increase speeds up to 2 Gbps
CWNA Guide to Wireless LANs, Second Edition

80. WPANs: IEEE
Sometimes preferable to have low-speed, low-power wireless devices
Size can be dramatically reduced
IEEE standard addresses requirements for RF transmissions requiring low power consumption and cost
Table 12-3: IEEE data rates and frequencies
CWNA Guide to Wireless LANs, Second Edition

81. WPANs: IEEE 802.15.4 (continued)
ZigBee Alliance: Industry consortium that promotes standard
Figure 12-7: ZigBee and IEEE
CWNA Guide to Wireless LANs, Second Edition