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

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

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 802.11a/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

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

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

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

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 802.15 standards Radio frequency ID (RFID) IrDA CWNA Guide to Wireless LANs, Second Edition

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

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

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 email to notebook computer in briefcase or send audible e-mail message See Figure 5-1 CWNA Guide to Wireless LANs, Second Edition

Bluetooth Scenario CWNA Guide to Wireless LANs, Second Edition

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

IrDA Transmission CWNA Guide to Wireless LANs, Second Edition

Bluetooth Transmission CWNA Guide to Wireless LANs, Second Edition

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

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

Bluetooth Protocol Stack CWNA Guide to Wireless LANs, Second Edition

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

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

Bluetooth Transceiver CWNA Guide to Wireless LANs, Second Edition

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

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

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

Connection Speeds CWNA Guide to Wireless LANs, Second Edition

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

Power Classes CWNA Guide to Wireless LANs, Second Edition

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

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

2-GFSK CWNA Guide to Wireless LANs, Second Edition

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

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

Bluetooth FHSS CWNA Guide to Wireless LANs, Second Edition

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

Conflict with IEEE 802.11b Bluetooth and IEEE 802.11b WLANs use same frequency Several possible solutions Add special software to 802.11 WLAN to cause silence when Bluetooth communication is detected IEEE working on new standard that lets Bluetooth and 802.11b devices function better in shared space CWNA Guide to Wireless LANs, Second Edition

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

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

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

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

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

Bluetooth Time Slots CWNA Guide to Wireless LANs, Second Edition

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

Device A Inquiry CWNA Guide to Wireless LANs, Second Edition

Response and Confirmation CWNA Guide to Wireless LANs, Second Edition

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

Collision CWNA Guide to Wireless LANs, Second Edition

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

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

Piconet CWNA Guide to Wireless LANs, Second Edition

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

Scatternet CWNA Guide to Wireless LANs, Second Edition

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 (0-2745 bits)—contains data, voice, or both See Figure 5-17 CWNA Guide to Wireless LANs, Second Edition

Bluetooth Frame CWNA Guide to Wireless LANs, Second Edition

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

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

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

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

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

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

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

Authentication CWNA Guide to Wireless LANs, Second Edition

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

Encryption CWNA Guide to Wireless LANs, Second Edition

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

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

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

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

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

Market Position Current position is between IEEE 802.11x 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

Spectrum Conflict The 2.4 GHz band that Bluetooth uses conflicts with IEEE 802.11b 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 802.11b WLANs share spectrum New 802.11a WLAN standard uses a different frequency, eliminating the conflict CWNA Guide to Wireless LANs, Second Edition

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 802.15.1 adapted and expanded from Bluetooth Designed for area of about 10 meters Rate of transmission below 1 Mbps Two types of 802.15.1 network topologies Piconet Scatternet CWNA Guide to Wireless LANs, Second Edition

WPANs: IEEE 802.15.1 (continued) Piconet: When two 802.15.1 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

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

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

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 802.15.1 uses FHSS CWNA Guide to Wireless LANs, Second Edition

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

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

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

WPANs: IEEE 802.15.3 (continued) Differences between 802.15.3 and 802.15.1 Quality of Service (QoS) Security High data rates Spectrum utilization Coexistence Table 12-2: IEEE 802.15.3 security modes CWNA Guide to Wireless LANs, Second Edition

WPANs: IEEE 802.15.3 (continued) 802.15.3a: 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 802.15.3b task group working on improving implementation and interoperability of 802.15.3 IEEE 802.15.3c task group developing alternative physical layer standard that could increase speeds up to 2 Gbps CWNA Guide to Wireless LANs, Second Edition

WPANs: IEEE 802.15.4 Sometimes preferable to have low-speed, low-power wireless devices Size can be dramatically reduced IEEE 802.15.4 standard addresses requirements for RF transmissions requiring low power consumption and cost Table 12-3: IEEE 802.15.4 data rates and frequencies CWNA Guide to Wireless LANs, Second Edition

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