High Rate Wireless Personal Area Networks
Wireless Communications Chapter High Rate Wireless Personal Area Networks 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 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 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 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 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 WiMedia Protocol Stack (continued) Wireless# Guide to Wireless Communications 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 WiMedia Protocol Stack (continued) Wireless# Guide to Wireless Communications 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 10 How UWB Works (continued) Wireless# Guide to Wireless Communications 31 How UWB Works (continued) Wireless# Guide to Wireless Communications 32 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 not interfere with each another • Data bits are sent simultaneously (in parallel) Wireless# Guide to Wireless Communications 33 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 – Based on the WiMedia specifications – Transmits at 480 Mbps at a distance of up to meters Wireless# Guide to Wireless Communications 34 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 35 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 36 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 37 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 38 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 39 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 40 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 41 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 42 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 43 Summary (continued) • Efficient data transmission is accomplished by use of the superframe concept • In 802.15.3, devices can be in one of several powersaving 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 44 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 45 ... the same area Wireless# Guide to Wireless Communications 14 802.15.3 Network Topology (continued) Wireless# Guide to Wireless Communications 15 802.15.3 Network Topology (continued) Wireless# ... frequency bands Wireless# Guide to Wireless Communications 30 How UWB Works (continued) Wireless# Guide to Wireless Communications 31 How UWB Works (continued) Wireless# Guide to Wireless Communications... multimedia projectors and sound systems Wireless# Guide to Wireless Communications 802.15.3 High Rate WPANs (continued) • Application characteristics – – – – – – Require high throughput Transceiver should