Wireless Guide to Wireless Communications Chapter 6 High

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

Objectives • Define a high rate wireless personal area network (HR WPAN) • List the different HR WPAN standards and their applications • Explain how Wi. Media and UWB work • Outline the issues facing WPAN technologies • Describe the security features of each HR WPAN technology Wireless# Guide to Wireless Communications 2

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 3

802. 15. 3 High Rate WPANs • IEEE standard defines the MAC and PHY layers • Wi. Media 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 4

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 5

Wi. Media Protocol Stack • Wi. Media 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 6

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

Wi. Media 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 8

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

Wi. Media 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

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

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 Qo. S • Devices can form a dependent piconet Wireless# Guide to Wireless Communications 12

802. 15. 3 Network Topology (continued) Wireless# Guide to Wireless Communications 13

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 14

802. 15. 3 Network Topology (continued) Wireless# Guide to Wireless Communications 15

802. 15. 3 Network Topology (continued) Wireless# Guide to Wireless Communications 16

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 Qo. S – Security – Efficient data transfer using superframes Wireless# Guide to Wireless Communications 17

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

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 Wireless# Guide to Wireless Communications 19

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 20

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 21

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

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 23

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

Mesh Networking (802. 15. 5) • Mesh networking – Each device connects to all other devices within range – Effectively creating multiple paths for transmission – Enable Wi. Media networks to span an entire building Wireless# Guide to Wireless Communications 25

Mesh Networking (802. 15. 5) (continued) Wireless# Guide to Wireless Communications 26

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 27

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 28

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

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 30

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 do not interfere with each another • Data bits are sent simultaneously (in parallel) Wireless# Guide to Wireless Communications 33

IEEE 802. 15. 3 a • 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 Fire. Wire at 400 Mbps – Based on an 802. 15. 3 a/Wi. Media platform • Wireless USB (WUSB) version 2 – Based on the Wi. Media specifications – Transmits at 480 Mbps at a distance of up to 2 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. 3 a 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 (Fire. Wire) 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 (Do. S) 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 • Ir. DA 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 Zig. Bee 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. 11 a networks • Zig. Bee and Wi. Media products should be able to coexist with 802. 11 b/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 Wi. Media 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. 11 b 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