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Wireless Guide to Wireless Communications

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Wireless Guide to Wireless Communications

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

    2. Wireless# Guide to Wireless Communications 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

    3. 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

    4. 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

    5. 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

    6. 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

    7. Wireless# Guide to Wireless Communications 7

    8. 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)

    9. Wireless# Guide to Wireless Communications 9

    10. 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

    11. Wireless# Guide to Wireless Communications 11

    12. 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

    13. Wireless# Guide to Wireless Communications 13

    14. 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

    15. Wireless# Guide to Wireless Communications 15

    16. Wireless# Guide to Wireless Communications 16

    17. 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

    18. Wireless# Guide to Wireless Communications 18

    19. 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 isochronous time

    20. 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

    21. 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

    22. Wireless# Guide to Wireless Communications 22

    23. 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

    24. Wireless# Guide to Wireless Communications 24

    25. 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

    26. Wireless# Guide to Wireless Communications 26

    27. 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

    28. 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

    29. Wireless# Guide to Wireless Communications 29

    30. 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

    31. Wireless# Guide to Wireless Communications 31

    32. Wireless# Guide to Wireless Communications 32

    33. 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)

    34. 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

    35. 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

    36. 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

    37. 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

    38. 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

    39. 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

    40. 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

    41. 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

    42. 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

    43. 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

    44. 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

    45. 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

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