Wireless# Guide to Wireless Communications 6-1 Chapter 6 High Rate Wireless Personal Area Networks At a Glance Instructor’s Manual Table of Contents Overview Objectives Teaching Tips Quick Quizzes Class Discussion Topics Additional Projects Additional Resources Key Terms Technical Notes for Hands-On Projects Wireless# Guide to Wireless Communications 6-2 Lecture Notes Overview Chapter 6 defines a high rate wireless personal area network (HR WPAN). Students will learn about the different HR WPAN standards and their applications. Next, students will see how WiMedia and UWB work. Chapter 6 also outlines the issues facing WPAN technologies. Finally, students will review the security features of each HR WPAN technology. Objectives Define a high rate wireless personal area network (HR WPAN) List the different HR WPAN standards and their applications Explain how WiMedia and UWB work Outline the issues facing WPAN technologies Describe the security features of each HR WPAN technology Teaching Tips High Rate WPAN Standards 1. Mention that the IEEE is currently working on two additional standards for WPANs: the IEEE 802.15.3 and 802.15.5 standards. 2. Explain that the IEEE 802.15.3 standard defines the specifications for HR WPANs supporting speeds of 11, 22, 33, and up to 55 Mbps in the 2.4 GHz ISM band. Teaching For more information about the IEEE 802.15.3 and 802.15.5 standards, visit: Tip http://grouper.ieee.org/groups/802/15/. 802.15.3 High Rate WPANs 1. Mention that IEEE standard only defines the MAC and PHY layers for WPANs. 2. Explain that the WiMedia Alliance was formed to support the development of any necessary higher-layer protocols and software specifications for 802.15.3. Describe some of the potential applications for this standard. Wireless# Guide to Wireless Communications 6-3 3. Describe the characteristics required by 802.15.3 applications: a. Require high throughput b. Transceiver should be low-power c. Cost should be low d. Require quality-of-service (QOS) capabilities e. Connections should be simple and automatic f. Devices should be able to connect to multiple other devices g. Security features should be included Teaching For more information about the IEEE 802.15.3 standard, visit: Tip www.ieee802.org/15/pub/TG3.html. WiMedia Protocol Stack 1. Explain that the WiMedia group defined two different architectures for the upper layers of the protocol stack. One is used for multimedia audio/visual applications and the other for data transfer applications. Use Figure 6-1 to illustrate your explanation. 2. Describe the 802.15.3 PHY layer. This layer is responsible for converting data bits into a modulated RF signal. The 802.15.3 standard uses the ISM 2.4 GHz band and supports two different channel plans: a. A coexistence channel plan b. A high-density channel plan 3. Mention that the channels are limited to 15 MHz bandwidth. Use Table 6-1 to describe the supported channel plans. 4. Explain that the IEEE 802.15.3 standard specifies five data rates: 11 Mbps, 22 Mbps, 33 Mbps, 44 Mbps, and 55 Mbps. This standard uses trellis code modulation (TCM) technology that encodes the digital signal so single bit errors can be detected and corrected. This technique is also referred to as forward error correction (FEC). Teaching Read more about trellis code modulation at: Tip http://en.wikipedia.org/wiki/Trellis_modulation. 5. Use Table 6-2 to describe the various modulation techniques supported by the IEEE 802.15.3 standard. Wireless# Guide to Wireless Communications 6-4 6. Mention that because 802.15.3 operates in the same 2.4 GHz unlicensed band as other standards, to prevent interference, the PHY layer includes a number of enhancements, including: a. Passive scanning b. Dynamic channel selection c. Ability to request channel quality information d. Link quality and received signal strength indication e. Transmit power control f. An 802.11 coexistence channel plan g. Lower transmit power h. Neighbor piconet capability 802.15.3 Network Topology 1. Define a Piconet Coordinator (PNC) as a role assumed by the first device in the area that provides all of the basic communications timing in a piconet. The PNC is also responsible for managing QoS. Use Figure 6-2 to illustrate your explanation. 2. Explain that devices can form a dependent piconet. Use Figure 6-3 and Figure 6-4 to describe the two types of piconets: a. Child piconet b. Neighbor piconet Additional MAC Layer Functionality 1. Describe the MAC layer functionality as explained in this section. 2. Explain that efficient data transfer is accomplished using superframes. Use Figure 6-5 to illustrate your explanation. 3. Describe the structure of a superframe in the 802.15.3 standard. 4. Explain the general communication process in an 802.15.3 piconet, as described in this section. 5. Explain that one of the best power management methods included in the 802.15.3 standard is the ability of devices to turn off completely for long periods of time without losing their association with the piconet. 6. Describe the three main 802.15.3 power-saving methods: a. Device synchronized power save (DSPS) mode b. Piconet synchronized power save (PSPS) mode c. Asynchronous power save (APS) mode 7. Define a wake superframe as a superframe designated by the PNC, in which devices that are in power save mode wake up and listen for frames addressed to them. Use Figure 6-6 to show the use of wake superframes. Wireless# Guide to Wireless Communications 6-5 8. Describe the following two additional power-saving methods: a. PNC can set a maximum transmit power level b. Devices request a reduction or an increase in their own transmit power 9. Explain that all MAC frames include a set of fields that are present in the same order in every frame. Use Figure 6-7 to show the general MAC frame format. Mesh Networking (802.15.5) 1. Define the IEEE 802.15.5 as a proposed standard for mesh networking, in which each device connects to all other devices within range, effectively creating multiple paths for transmission. Use Figure 6-8 to illustrate a mesh networking. Quick Quiz 1 1. The ____________________ was formed to support the development of any necessary higher-layer protocols and software specifications for 802.15.3 and to perform various other administrative functions. Answer: WiMedia Alliance 2. ____________________ capabilities allow devices to request more channel access time in order to prioritize high-volume, time-sensitive traffic, such as voice stream. Answer: Quality-of-service (QOS) Quality-of-service QOS 3. The ____________________ is the device that provides all of the basic communications timing in a piconet. Answer: piconet coordinator (PNC) piconet coordinator PNC 4. The frame check sequence (FCS) is a 32-bit ____________________ field, a common technique for detecting data transmission errors. Answer: cyclic redundancy check (CRC) cyclic redundancy check CRC Ultra Wide Band (UWB) 1. Explain that UWB allows new transmission techniques based on UWB to coexist with other RF systems with minimal or no interference. Wireless# Guide to Wireless Communications 6-6 2. Describe some of the main characteristics of UWB, including: a. It transmits low-power, short-range signals b. It transmits using extremely short low-power pulses lasting only about 1 nanosecond c. It transmits over a band that is at least 500 MHz wide d. UWB can potentially send data at speeds of up to 2 Gbps Teaching For more information about Ultra Wide Band, visit: Tip http://en.wikipedia.org/wiki/Ultra_wideband. How UWB Works 1. Mention that normally, digital signals need to be spread over a wide band using techniques such as FHSS or DSSS. UWB uses short analog pulses for signaling, and does not rely on traditional modulation methods. This technique is called impulse modulation. Define biphase modulation as the most common modulation technique used by UWB. Biphase modulation uses a half-cycle positive analog pulse to represent a 1. Use Figure 6-9 to illustrate the UWB impulse modulation and the biphase modulation. 2. Describe the following two additional modulation techniques: a. Direct-sequence UWB (DS-UWB) b. Orthogonal frequency division multiplexing (OFDM) 3. Explain that DS-UWB takes advantage of the fact that when transmitting pulses that are a nanosecond long, the signal naturally spreads over a very wide frequency band. In the UWB case, the signal spreads over a band that is at least 500 MHz wide. Use Figure 6- 10 to illustrate your explanation. 4. Explain that in orthogonal frequency division multiplexing (OFDM), commonly referred to as MB-OFDM, the frequency band is divided into five groups containing a total of 14 frequency bands. Use Table 6-3 to describe the MB-OFDM frequency band allocation. 5. Mention that each frequency band is 528 MHz wide, further divided into 128 frequency channels. These channels are orthogonal, meaning that they do not interfere with each another. Teaching Read more about OFDM at: http://en.wikipedia.org/wiki/OFDM. Tip IEEE 802.15.3a 1. Define IEEE 802.15.3a as a proposed enhancement to 802.15.3 that uses UWB technology to support higher data rates for multimedia and imaging applications. Wireless# Guide to Wireless Communications 6-7 2. Explain that the Protocol Adaptation Layer (PAL) enables wireless FireWire at 400 Mbps, based on an 802.15.3a/WiMedia platform. 3. Mention that the 802.15.3a standard also defines wireless USB (WUSB) version 2, based on the WiMedia specifications and transmitting at 480 Mbps at a distance of up to 6 feet (2 meters). Teaching For more information about the IEEE 802.15.3a standard, visit: Tip www.ieee802.org/15/pub/TG3a.html. WPAN Challenges This section explains challenges faced by WiMedia and UWBWPAN technologies. Competition Among WPAN Standards 1. Explain that IEEE 802.15.3 and .3a are positioned to compete with Bluetooth for market share. It will take a few years before 802.15.3 products begin to appear on the market. 2. Mention that wireless USB and wireless 1394 (FireWire) have the potential to quickly outpace Bluetooth. HR WPAN Security 1. Explain the following security problems that affect Bluetooth technology: a. Bluejacking b. Bluesnarfing c. Denial-of-Service (DoS) attack Teaching Read more about Bluejacking at: http://en.wikipedia.org/wiki/Bluejacking. Tip Teaching Read an article about the risks of Bluesnarfing at: Tip http://news.zdnet.co.uk/communications/wireless/0,39020348,39145881,00.htm. 2. Explain that the security for IEEE 802.15.3 HR WPANs is based on the Advanced Encryption Standard (AES) and defines how any two devices can establish a secure communications session to protect both the information as well as the integrity of communications at the MAC and PHY layers. Wireless# Guide to Wireless Communications 6-8 Teaching For more information about the Advanced Encryption Standard (AES), visit: Tip http://en.wikipedia.org/wiki/Advanced_Encryption_Standard. 3. Mention that IEEE 802.15.3 also supports message integrity verification at the MAC layer that prevents a man-in-the-middle attack. Cost of WPAN Components 1. Describe the economic problems faced by Bluetooth technology, as explained in this section. Industry Support for WPAN Technologies 1. Explain that IrDA has enjoyed strong industry support for many years, while Bluetooth’s support in the networking industry has been, at best, spotty. 2. Mention that industry experts predict that new technologies like 802.15.3 and ZigBee will be more quickly embraced by manufacturers. Protocol Functionality Limitations 1. Explain that Bluetooth protocol suffers from its lack of hand-off capability between piconets. Define hand-off as the ability of a device to move from one master or PNC to another without getting disconnected from the network. 2. Describe the limitations in infrared communications. In infrared, roaming is a limitation but not a concern, since this technology is designed for peer-to-peer communications. Spectrum Conflict 1. Define spectrum conflict as the potential for technologies using the same frequency bands to interfere with each other. Applying UWB technology may significantly reduce or eliminate this issue. 2. Mention that UWB can interfere with 802.11a networks. ZigBee and WiMedia products should be able to coexist with 802.11b/g without any serious problems. Quick Quiz 2 1. ____________________ attacks flood a Bluetooth device with so many frames that it is unable to communicate. Answer: Denial-of-service (DoS) Denial-of-service DoS Wireless# Guide to Wireless Communications 6-9 2. ____________________ is a symmetric key encryption mechanism introduced by the National Institute of Standards and Technology (NIST) in the United States. Answer: Advanced Encryption Standard (AES) Advanced Encryption Standard AES 3. ____________________ is the ability of a device to move from one master or PNC to another without getting disconnected from the network in a network that extends beyond the communications range of each device that controls the communications. Answer: Hand-off 4. ____________________ is the potential for technologies using the same frequency bands to interfere with each other to the extent that they sometimes perform poorly when used within close range of each other. Answer: Spectrum conflict Class Discussion Topics 1. What is a piconet? 2. What are the benefits of using message integrity verification at the 802.15.3 MAC layer? Additional Projects 1. Ask your students to write a one-page report listing various applications for ultra wide band (UWB). 2. Ask your students to write a one-page report explaining a man-in-the-middle attack. They can use the Internet to research for information about this type of attack. Additional Resources 1. IEEE 802.15: http://en.wikipedia.org/wiki/IEEE_802.15.1 2. WiMedia Alliance: www.wimedia.org/en/index.asp 3. Ultra Wideband (UWB) Technology: www.intel.com/technology/comms/uwb/ 4. UWB Forum: www.uwbforum.org/ Wireless# Guide to Wireless Communications 6-10 5. Orthogonal Frequency Division Multiplexing (OFDM) Forum: www.caba.org/standard/ofdm.html 6. EEE 802.15 Working Group for WPAN: http://grouper.ieee.org/groups/802/15/ 7. Bluejacking: www.bluejacking.info/index.html 8. Bluesnarfing: http://en.wikipedia.org/wiki/Bluesnarfing 9. Advanced Encryption Standard: www.utimaco.us/encryption/aes.html Key Terms Advanced Encryption Standard (AES) — A symmetric key encryption mechanism introduced by the U.S. National Institute of Standards and Technology. biphase modulation — Modulation that uses a half-cycle positive analog pulse to represent a 1 and a half-cycle negative analog pulse to represent a 0. channel time allocation (CTA) — Periods of time allocated by the PNC to a specific device for prioritizing communications in a WPAN. See also management channel time allocation (MCTA). channel time allocation period (CTAP) — The superframe component used for communications between the PNC and other devices. child piconets — Separate piconets with their own ID; the child PNC is a member of the original or parent piconet. contention access period (CAP) — A mechanism used to communicate commands or any asynchronous data that may be present in a superframe. The CAP is also used to allow devices that are not yet part of a piconet to send a request to the PNC to join the piconet. cyclic redundancy check (CRC) — A common technique for detecting data transmission errors. denial-of-service (DoS) — A type of security attack on a networked device in which the attacker sends so many frames to a single device that the device is unable to communicate with other devices. hand-off — The ability of a device to move from one master or PNC to another without getting disconnected from the network in a network that extends beyond the communications range of each device that controls the communications. impulse modulation — A digital transmission technique employed by UWB in which the polarity of a single analog pulse (one-half of a sine wave) represents a binary digit 1 or 0. isochronous — The channel time in synchronous transmissions. management channel time allocation (MCTA) — Time periods used for communication between the devices and the PNC. Wireless# Guide to Wireless Communications 6-11 man-in-the-middle attack — A security attack in which a hacker captures frames, alters them, and then retransmits them to the intended receiver or another device on the network. mesh networking — A network topography in which each device connects to all other devices within range. message integrity — A process of adding certain encrypted random data to each communications session so that the receiver can verify that the message has not been tampered with, after being transmitted. neighbor piconets — Separate piconets that have their own PNC, but that depend on the original piconet’s PNC to allocate a private block of time when their devices are allowed to transmit. orthogonal frequency division multiplexing (OFDM) — A transmission technique in which the frequency band is divided into a number of frequencies (called sub- frequencies or channels) that do not interfere with each other. piconet coordinator (PNC) — A device that provides all of the basic communications timing in an 802.15.3 piconet. Protocol Adaptation Layer (PAL) — A set of protocol implementation rules that will enable wireless FireWire at 400 Mbps, based on an 802.15.3a/WiMedia platform. quality of service (QoS) — A feature of some PANs that allows devices to request more channel access time in order to prioritize high-volume, time-sensitive traffic, such as a voice stream. spectrum conflict — The potential for technologies using the same frequency bands to interfere with each other to the extent that they sometimes perform poorly when used within close range of each other. superframe — A mechanism for managing transmissions in a piconet. The superframe is a continually repeating frame containing a beacon, contention access periods, channel time allocation periods, and management time allocation periods. trellis code modulation (TCM) — A method of encoding a digital signal in a way that permits single bit errors to be detected and corrected. wake superframe — The superframe designated by the PNC in which devices that are in power save mode will wake up and listen for frames addressed to them. WiMedia Alliance — An association of manufacturers and interested organizations formed to promote the implementation of the IEEE 802.15.3 standard and provide various support activities. Technical Notes for Hands-On Projects Project 6-1: This project requires a Web browser and an Internet connection. Project 6-2: This project requires a Web browser and an Internet connection.
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