Wireless# Guide to Wireless Communications

1. Wireless# Guide to Wireless Communications Chapter 6 High Rate Wireless Personal Area Networks

2. 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 Wireless# Guide to Wireless Communications

3. High Rate WPAN Standards • IEEE is currently working on two standards • IEEE 802.15.3 and 802.15.5 • 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 Wireless# Guide to Wireless Communications

4. 802.15.3 High Rate WPANs • IEEE standard defines the MAC and PHY layers • WiMedia Alliance • Formed to support the development of any necessary higher-layer protocols • And software specifications for 802.15.3 • Potential applications • Connecting digital cameras to printers and kiosks • Connecting laptops to multimedia projectors and sound systems Wireless# Guide to Wireless Communications

5. 802.15.3 High Rate WPANs (continued) • Application characteristics • Require high throughput • Transceiver should be low-power • Cost should be low • Require quality-of-service (QOS) capabilities • Connections should be simple and automatic • Devices should be able to connect to multiple other devices • Security features should be included Wireless# Guide to Wireless Communications

6. WiMedia Protocol Stack • 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 • The lower two layers of the stack (MAC and PHY) • Are implemented in hardware • 802.15.3 PHY layer • Converts data bits into a modulated RF signal • 802.15.3 standard uses the ISM 2.4 GHz band Wireless# Guide to Wireless Communications

7. WiMedia Protocol Stack (continued) Wireless# Guide to Wireless Communications

8. WiMedia Protocol Stack (continued) • 802.15.3 PHY layer (continued) • Supports two different channel plans • A coexistence channel plan • A high-density channel plan • Channels are limited to 15 MHz bandwidth • IEEE 802.15.3 standard specifies five data rates • 11 Mbps, 22 Mbps, 33 Mbps, 44 Mbps, and 55 Mbps • Trellis code modulation (TCM) • Encodes the digital signal so single bit errors can be detected and corrected • Also called error correction (FEC) Wireless# Guide to Wireless Communications

9. WiMedia Protocol Stack (continued) Wireless# Guide to Wireless Communications

10. WiMedia Protocol Stack (continued) • Modulation • See Table 6-2 for modulation techniques • Enhancements • Passive scanning • Dynamic channel selection • Ability to request channel quality information • Link quality and received signal strength indication • Transmit power control • An 802.11 coexistence channel plan • Lower transmit power • Neighbor piconet capability Wireless# Guide to Wireless Communications

11. WiMedia Protocol Stack (continued) Wireless# Guide to Wireless Communications

12. 802.15.3 Network Topology • Piconet coordinator (PNC) • Role assumed by the first device in the area • Provides all of the basic communications timing in a piconet • PNC sends a beacon • The piconet is peer-to-peer • Devices can transmit data directly to each other • The PNC is also responsible for managing QoS • Devices can form a dependent piconet Wireless# Guide to Wireless Communications

13. 802.15.3 Network Topology (continued) Wireless# Guide to Wireless Communications

14. 802.15.3 Network Topology (continued) • Types of dependent piconets • Child piconets • Useful for extending the coverage of a piconet • Neighbor piconets • Allow coexistence with other piconets in the same area Wireless# Guide to Wireless Communications

15. 802.15.3 Network Topology (continued) Wireless# Guide to Wireless Communications

16. 802.15.3 Network Topology (continued) Wireless# Guide to Wireless Communications

17. Additional MAC Layer Functionality • The IEEE 802.15.3 MAC layer functionality • Connection time (association) is fast • Devices associated with the piconet can use a short, one-octet device ID • Devices can obtain information about the capabilities of other devices • Peer-to-peer (ad hoc) networking • Data transport with QoS • Security • Efficient data transfer using superframes Wireless# Guide to Wireless Communications

18. Additional MAC Layer Functionality (continued) Wireless# Guide to Wireless Communications

19. Additional MAC Layer Functionality (continued) • IEEE 802.15.3 superframe structure • A beacon • An optional contention access period (CAP) • The channel time allocation period (CTAP) • Communication in an 802.15.3 piconet • Beacon frame sent by the PNC includes a variable indicating the end of the CAP • Devices can send asynchronous data in the CAP • Devices can request channel time on a regular basis • Requested channel time is called isochronoustime Wireless# Guide to Wireless Communications

20. Additional MAC Layer Functionality (continued) • Communication in an 802.15.3 piconet • Devices can also request channel time for asynchronous communications in the CTAP • Communications use a time division multiple access (TDMA) scheme • Power management • 802.15.3 devices can turn off completely for long periods of time • Without losing their association with the piconet Wireless# Guide to Wireless Communications

21. Additional MAC Layer Functionality (continued) • Power management (continued) • 802.15.3 power-saving methods • Device synchronized power save (DSPS) mode • Piconet synchronized power save (PSPS) mode • Asynchronous power save (APS) mode • Wake superframe • Superframe designated by the PNC • Devices that are in power save mode wake up and listen for frames addressed to them Wireless# Guide to Wireless Communications

22. Additional MAC Layer Functionality (continued) Wireless# Guide to Wireless Communications

23. Additional MAC Layer Functionality (continued) • Power management (continued) • Additional power-saving methods • PNC can set a maximum transmit power level • Devices request a reduction or an increase in their own transmit power • General MAC frame format • All MAC frames include a set of fields that are present in the same order in every frame Wireless# Guide to Wireless Communications

24. Additional MAC Layer Functionality (continued) Wireless# Guide to Wireless Communications

25. Mesh Networking (802.15.5) • Mesh networking • Each device connects to all other devices within range • Effectively creating multiple paths for transmission • Enable WiMedia networks to span an entire building Wireless# Guide to Wireless Communications

26. Mesh Networking (802.15.5) (continued) Wireless# Guide to Wireless Communications

27. Ultra Wide Band (UWB) • Allows new transmission techniques based on UWB to coexist with other RF systems • With minimal or no interference • Characteristics • It transmits low-power, short-range signals • It transmits using extremely short low-power pulses lasting only about 1 nanosecond • It transmits over a band that is at least 500 MHz wide • UWB can send data at speeds of up to 2 Gbps Wireless# Guide to Wireless Communications

28. How UWB Works • UWB PHY • Digital signals need to be spread over a wide band • Using techniques such as FHSS or DSSS • UWB uses short analog pulses for signaling • Does not rely on traditional modulation methods • This technique is called impulse modulation • Biphase modulation • Most common modulation technique used by UWB • Uses a half-cycle positive analog pulse to represent a 1 Wireless# Guide to Wireless Communications

29. How UWB Works (continued) Wireless# Guide to Wireless Communications

30. How UWB Works (continued) • UWB PHY (continued) • Direct-sequence UWB (DS-UWB) • When transmitting pulses that are a nanosecond long • Signal spreads over a very wide frequency band • In the UWB case, the signal spreads over a band that is at least 500 MHz wide • Orthogonal frequency division multiplexing (OFDM) • Commonly referred to as MB-OFDM • Frequency band is divided into five groups containing a total of 14 frequency bands Wireless# Guide to Wireless Communications

31. How UWB Works (continued) Wireless# Guide to Wireless Communications

32. How UWB Works (continued) Wireless# Guide to Wireless Communications

33. How UWB Works (continued) • UWB PHY (continued) • Orthogonal frequency division multiplexing (OFDM) (continued) • Each frequency band is 528 MHz wide • Further divided into 128 frequency channels • Channels are orthogonal • They do not interfere with each another • Data bits are sent simultaneously (in parallel) Wireless# Guide to Wireless Communications

34. IEEE 802.15.3a • Proposed enhancement to 802.15.3 • Uses UWB technology to support higher data rates • For multimedia and imaging applications • Protocol Adaptation Layer (PAL) • Enables wireless FireWire at 400 Mbps • Based on an 802.15.3a/WiMedia platform • Wireless USB (WUSB) version 2 • Based on the WiMedia specifications • Transmits at 480 Mbps at a distance of up to 2 meters Wireless# Guide to Wireless Communications

35. WPAN Challenges • Challenges • Competition Among WPAN Standards • HR WPAN Security • Cost of WPAN Components • Industry Support for WPAN Technologies • Protocol Functionality Limitations • Spectrum Conflict Wireless# Guide to Wireless Communications

36. Competition Among WPAN Standards • 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 • Wireless USB and wireless 1394 (FireWire) have the potential to quickly outpace Bluetooth Wireless# Guide to Wireless Communications

37. HR WPAN Security • Bluetooth security • Bluejacking • Exploits a Bluetooth device’s ability to discover nearby devices and send unsolicited messages • Bluesnarfing • Accesses contact lists and other information without the user’s knowledge • Denial-of-service (DoS) attacks • Flood a Bluetooth device with so many frames that it is unable to communicate Wireless# Guide to Wireless Communications

38. HR WPAN Security (continued) • Security for IEEE 802.15.3 HR WPANs • Based on the Advanced Encryption Standard (AES) • Defines how any two devices can establish a secure communications session • To protect both the information and the integrity of communications at the MAC and PHY layers • 802.15.3 also supports message integrity verification at the MAC layer • Prevents a man-in-the-middle attack Wireless# Guide to Wireless Communications

39. Cost of WPAN Components • Bluetooth currently supports more devices than other WPAN technologies • Industry experts believe that price must be reduced to reach competitive advantage • Does not make economic sense to use a chip that costs $15 to replace a cable that costs $7 Wireless# Guide to Wireless Communications

40. Industry Support for WPAN Technologies • IrDA has had strong industry support for many years • Bluetooth’s support in the networking industry has been, at best, spotty • Industry experts predict that new technologies will be more quickly embraced by manufacturers • Such as 802.15.3 and ZigBee Wireless# Guide to Wireless Communications

41. Protocol Functionality Limitations • Bluetooth protocol suffers from its lack of hand-off capability between piconets • Hand-off • Ability to move from one master or PNC to another • Without getting disconnected from the network • In infrared, roaming is a limitation but not a concern • Since this technology is designed for peer-to-peer communications Wireless# Guide to Wireless Communications

42. Spectrum Conflict • Spectrum conflict • Potential for technologies using the same frequency bands to interfere with each other • Applying UWB technology may significantly reduce or eliminate this issue • UWB can interfere with 802.11a networks • ZigBee and WiMedia products should be able to coexist with 802.11b/g without any serious problems Wireless# Guide to Wireless Communications

43. Summary • IEEE 802.15.3-2003 is a WPAN technology • Optimized for multimedia voice and video signals • The WiMedia protocol stack has two upper layers • One for audio/video and one for data transfer applications • The PHY layer supports two different channel plans • Works in the same ISM band as 802.11b WLANs • 802.15.3 supports peer-to-peer or ad hoc networks • 802.15.3 piconets support child and neighbor piconets Wireless# Guide to Wireless Communications

44. Summary (continued) • Efficient data transmission is accomplished by use of the superframe concept • In 802.15.3, devices can be in one of several power-saving modes • 802.15.5 mesh networking standard extends the capabilities of 802.15.3 networks • Ultra Wide Band is a digital transmission technology • Will soon support very high-speed transmissions at up to 100+ Mbps • UWB transmissions: bandwidth of at least 500 MHz Wireless# Guide to Wireless Communications

45. Summary (continued) • UWB transmits using very short pulses • Challenges for WPANs include speed, security, cost, industry support, interference, and protocol limitations • WPAN devices that are designed to be small and consume very little power have limited processing capabilities and storage Wireless# Guide to Wireless Communications