'IEEE Personal Feb~~r1~~0
`Commun1ctit1i
`
`~
`
`Petitioner's Exhibit 1005
`Page 001
`
`

`

`FEBRUARY 2000 VOL. 7 NO. 1
`
`< ~~ :::; ;~::1 EE Personal
`' ~ <; ommun1cal1ons
`
`,~~ 0
`
`Page 11
`
`Pa9e20
`
`6
`Guest Editorial:
`Connectivity and Application Enablers for
`Ubiquitous Computing and Communications
`Chatschik Bisdikian, Jaap C. Haartsen, and Parviz Kermani
`
`8
`Remembering Mark Weiser: Chief Technologist Xerox PARC
`Roy Want
`
`11
`lrDA: Past Present and Future
`Stuart Williams
`
`20
`HomeRF Wireless Networking for the Connected Home
`Kevin J. Negus, Adrian P. Stephens, and Jim Lansford
`
`28
`The Bluetooth Radio System
`Jaap C. Haartsen
`
`37
`Paving the Way for Personal Area Network Standards:
`An Overview of the IEEE P802. 75 Working Group for
`Wireless Personal Area Networks
`Thomas M. Siep, Ian C. Gifford, Richard C. Braley, and Robert F. Heile
`
`44
`System Support for Mobile, Adaptive Applications
`Brian Noble
`
`Page44
`
`Cover illustration: The Stock
`Market
`
`2
`
`Editor's Note - 4
`Index to Articles: 1999 - 50
`
`IEEE Personal Communications • Fel:>ruazy 2000
`
`Petitioner's Exhibit 1005
`Page 002
`
`

`

`EDITOR'S NOTE
`
`J t is my utmost honor and privilege
`
`to serve our 1£Jit,· Personal Communications
`community starting with this issue of our
`magazine. Al first, on behalf of our Editorial
`Board and the IEEE Communications Soci(cid:173)
`ety, I would like to extend my sincere grati(cid:173)
`tude to Tom La Porta. who served as
`Editor-in-Chief from 1997 to 1999. Tom will
`continue to help and guide us as a senior
`advisor of the magazine. It will be hard to
`match the high level of leadership quality he
`has established, and I count on him, our
`founding Editor-in-Chief, Hamid Ahmadi,
`our Advisory Board, technical editors, and
`the IEEE editorial team to help me carry my
`responsibility as the new Editor-in-Chief.
`In my view, this is the most exiting time in our area;
`we are starting a new millennium with tremendous anticipa-
`
`tion of tbe possibilities and potentials wire(cid:173)
`less and mobile technologies will bring to us.
`It is expected that by 2003 the number of
`cellular subscribers will be equal to the
`number of wired phone subscribers. Obvi(cid:173)
`ously, new evolving architectures and stan(cid:173)
`dards, such as GPRS and EDGE, and
`third-generation systems will play a major
`role in this transition, enabling a high-speed,
`ubiquitous wireless Internet. After all, it will
`be a totally new world when one billion peo(cid:173)
`ple carry a personal gateway to the Internet
`with integrated voice and data support.
`Today, wireless technologies have crossed
`the cost, integration, and power consump(cid:173)
`tion barriers, and are a key factor in defini.ng new directions
`not only in enterprise but also in consumer markets. Sec(cid:173)
`ond-generation cellular technologies are leading this front,
`
`MAHMOUD
`NAGHSHINEH
`
`Director of Ma2azines
`Mark J. Karol. Lucent Tcclmologies., USA
`Editor-in-Chief
`Mahmoud Naghshineh. IBM Research. USA
`Senior Advisors
`Hamid Ahmadi, AT&T L.a:,s, USA
`Thomas F. La Pona, Lucent Technologies, USA
`Advisory Board
`Donald Cox. Stanford University, USA
`David Goodman, Rutgers University, USA
`Jorma Lilleberg, Nolda. Finland
`Kaveh Pahlavan, Worcester Polytechnic
`Institute, USA
`Mahadev Satyanarayanan, CMU, USA
`IEEE Vehicular Technology Liais on
`Theodore Rappaport, Virginia Tech, USA
`IEEE Computer Society liaison
`Mike Uu, Ohio State University, USA
`Technical Editor,
`Umesh Amin, AT&T Wirele$ Service;, USA
`B. R. Badrinoth. Rutgers University. USA
`Prnvin Bhogwat, lBM Research, USA
`Kwang-Cheng Chen, Tsing Hua Univ., Taiwan
`Si Tak Stanley Chia. AirTouch International. UK
`Andrea Goldsmith. Caltech, USA
`Paul Gough. Philips Research. UK
`D8\1de Grillo, Fonclazione Ugo Bordoni, Italy
`Jaap Haansen, Ericsson, Sweden
`Tokeshi Hattori, NTT, Japan
`Ravi Jain. Bellcore. USA
`Joseph Kahn, UC Berkeley, USA
`Parviz Kermani. IBM Research. USA
`Richard uiMaire. IBM Research. USA
`Murray Mazer, Open Group Research Inst., USA
`Sergio Palazzo, Univcrsny of Catania. Italy
`Ramachandran Ramjee, Lucent Technologies.
`Bell Labs, USA
`Bill Schilit, Fl( Palo Alto uib, Inc .. USA
`Thomus Y. C. Woo, Luc"nt Technolog~es, USA
`Yaco, Yacobi, Microsoft Corp., USA
`Michele Zorzi. University of CA San Diego. USA
`Department Editors
`Book Reviews
`Seshadri Mohan, Bcllcore, USA
`Conference Rcvit.~v
`Thoma, Y. C. Woo, Lucent Technologies, USA
`Scanning tire Lirt..70.ture
`Yi-Bing Lin, National Chiao Tung Univ .. Taiwan
`IEEE Pro duction Slaff
`Joseph Milizzo, Mana~cr, Print &
`Electronic Pubhshmg
`Catherine Kemelmacher, Production Editor
`Eric Levine, Advertising Sales Manager
`Joaone O'Rourke. Staff Assistant
`Susan Lange. Layout Editor
`Jennifer Porcello, Editorial Assistant
`
`IEEE Personal
`Commun1cat1ons
`
`+iii I fihii il·iiih i 13, 11+1
`
`2000 Communica tio n s So ciety
`Board o f Governors
`
`Officers
`J. Roberto De Marca. l'r,•sidem
`Thomas J. Plevyak, Past Pr.:sitle111
`Curtis A. Siller. VP-Teclt11ical Ac//viries
`Horst Bessai. VP-Member.ihip Services
`Dougl'1S N. Zuckerman, Vl'(cid:173)
`Member.ilup OC1•elopmell{
`Federico Tosco, VP-Society Relations
`Harvey Freeman, Treasurer
`John M. Howell, Secretary
`
`Members-at-Large
`Class of 2000
`Gerhard Fenweis
`Paul Hartmann
`Michael Kincaid
`William R. Robinson
`Class of 200 I
`L1ura Cerchia
`Leonard Cimini
`Roberta Cohen
`William Tranter
`Class of 2002
`Tomonori Aoyama
`Alex Gelman
`Roch Guerin
`ByeongLce
`
`2000 IEE[ Officers
`Bruce A. Ei~nstein. Prestdem
`Joel B. Snyder, Presidem-Elea
`David J. Kemp, Sern:ta1y
`David A. Conner, Treasurer
`Kenneth R. L:tker, /'asr Pre,i<lell{
`Daniel J. Senese, Execwive Dire<lor
`Tom Rowbotham, Direcror. Division Ill
`
`• IEEE
`
`IEEE Personal Communications - The Maga(cid:173)
`zine of Wireless Communications and
`Nett, orking (ISSN 1070-9916) is published
`himosthly by The Institute of Elcctricul ttnd
`Etcc1ronics Engineer&. Inc. Hc:1clqu:ttten; addtcss:
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`4
`
`IEEE Personal Commumcations • February 2000
`
`Petitioner's Exhibit 1005
`Page 003
`
`

`

`Abstract
`,\ few year,, ago it wa, recognized that the , ision of a trul) low--co,t. low-power radio-based cable replacement was feasible. Such a uhiquitous
`lmk would provide the basis for portable devices to communicate together in an ad hoc fashion b) creating personal area networh which have
`similar advantages to their office environmcn1 countcrpun, 1he local area network. Bluetooth'" is an cfforl by a consorlium of companies to
`design a royalty-free technology specification enabling this vi,10n. This article describes the radio system behind the Bluetooth concept. Designing
`an ad hoc radio system for worldwide usage poses several challenges. The article describes the critical sy,tcm characteristics and motivates the
`design choices that have been made.
`
`The Bluetooth Radio System
`
`J AAP C . HAARTSEN, E RICSSON RADIO SYSTE MS B .V.
`
`1 o ,he los, dc~•des. pmg,= ;,
`
`microelectronics and very large scale integration (VLSI) tech(cid:173)
`nology has fostered the widespread use of computing and
`communication devices for commercial usage. The success of
`consumer products like PCs. laptops. personal digital assis(cid:173)
`tants (PDAs). cell phones. cordless phones. and their periph(cid:173)
`erals has been based on continuous cost and size reduction.
`Information transfer between these devices has been cumber(cid:173)
`some, mainly relying on cables. Recently. a new universal
`radio interface has been developed enabling electronic devices
`to communicate wirelessly via short-range ad hoc radio con(cid:173)
`nections. The Blucwoth technology - which has gained the
`support of leading manufacturers like Ericsson. Nokia, IBM,
`Toshiba. Intel. and many others -
`eliminates the need for
`wires, cables, and the corresponding connectors between cord(cid:173)
`less or mobile phones, modems. headsets, PDAs. computers,
`printers, projectors, and so on. and paves the way for new and
`completely different devices and applications. The technology
`enables the design of low-power, small-sized, low-cost radios
`that can be embedded in existing (portable) devices. Eventual(cid:173)
`ly. these embedded radios will lead toward ubiquitous connec(cid:173)
`tivity and truly connect everything to everything Radio
`technology will allow this connectivity to occur without any
`explicit user interaction.
`This article describes the basic design and technology
`trade-offs which have led to the Bluetooth radio system. We
`describe some fundamental issues regarding ad hoc radio sys(cid:173)
`tems. We give an overview of the Bluetooth system itself with
`the emphasis on the radio architecture. It explains how the
`system has been optimized to support ad hoc connectivity. We
`also describe the Bluetooth specification effort.
`Ad Hoc Radio Connectivity
`The maJority of radio systems m commercial use toda) are
`based on a cellular radio architecture. A mobile network estab(cid:173)
`lished on a wired backbone infrastructure uses one or more
`base stations placed at strategic positions to provide local cell
`coverage; users apply portable phones, or more generic mobile
`terminals, to access the mobile network; the terminals main(cid:173)
`tain a connection to the network via a radio link to the base
`stations. There is a strict separation between the base stations
`and the terminals. Once registered to the network. the tenni(cid:173)
`nals remain locked to the control channels in the network, and
`connections can be established and released according to the
`control channel protocols. Channel access. channel allocation.
`traffic control. and interference minimization are neatly con-
`
`trolled by the base stations. Examples of these conventional
`radio systems arc the public cellular phone systems like Glob(cid:173)
`al System for Mobile Communications (GSM), D-AMPS, and
`IS-95 [ 1-3], but also private systems like wireless local area
`network (WLAN) systems based on 802.11 or IIIPERLAN l
`and HIPERLAN II 14-6]. and cordless systems like Digital
`Enhanced Cordless Telecommunications (DECT) and Person(cid:173)
`al Handyphone System (Pl IS) (7, 8].
`In contrast. in truly ad hoc systems. there is no difference
`between radio units; that is. there arc no distinctive base sta(cid:173)
`tions or terminals. Ad hoc connectivity is based on peer com(cid:173)
`munications. There is no wired infrastructure to support
`connectivity between portable units: there is no central con(cid:173)
`troller for the units to rely on for making interconnections; nor
`is there support for coordination of communications. In addi(cid:173)
`tion, there is no intervention of operators. For the scenarios
`envisioned by Bluctooth, it is highly likely that a large number
`of ad hoc connections will coexist in the same area without any
`mutual coordination; that is, tens of ad hoc links must share
`the same medium at the same location in an uncoordinated
`fashion. This is different from ad hoc scenarios considered in
`the past, where ad hoc connectivity focused on providing a sin(cid:173)
`gle (or very few) network(s) between the units in range (4, 5].
`For the Bluetooth applications, typically many independent
`networks overlap in the same area. This will be indicated as a
`scatter ad hoc environment. Scatter ad hoc environments con(cid:173)
`sist of multiple networks. each containing only a limited num(cid:173)
`ber of units. The difference between a conventional cellular
`environment. a conventional ad hoc environment. and a scatter
`ad hoc environment is illustrated in Fig. I. Tbe environmental
`characteristics the ad hoc radio system has to operate in have a
`major impact on the following fondamental issues:
`• Applied radio spectrum
`• Determining which units arc available to connect to
`• Connection establishment
`• Multiple access scheme
`• Channel allocation
`• Medium access control
`• Semce prioritization (i.e .. voice before data)
`• (Mutual) interference
`• Power consumption
`Ad hoc radio system have been in use for some time. for
`example. walky-talky systems used by the military. police. fire
`departments, and rescue teams in general. However, the Blue(cid:173)
`tooth system is the first commercial ad hoc radio system envi(cid:173)
`sioned to be used on a large scale and widely available to the
`public.
`
`28
`
`1070-9916 00 $10.(JO O 2000 IEEE
`
`IEEE Personal Communication, • February 2lKHl
`
`Petitioner's Exhibit 1005
`Page 004
`
`

`

`, . : : ..
`
`,,
`'
`'
`
`\ •
`
`I
`
`•
`
`•
`
`/
`
`...... ---
`•
`
`... - - - - . .
`
`.
`
`'
`
`I
`,
`',
`I
`
`I
`I
`
`' ' '
`
`,,-.-·
`• • •• ' .
`•••
`•
`•
`.. .. I ' ,•
`•
`'' ' .
`' ' ' '
`.. •
`• ,
`'
`'
`'·,.~ ,/
`
`,
`
`(b)
`
`'
`
`I
`
`'
`..,
`
`I
`\~ ...... , ...
`.....
`/
`
`•
`I
`;
`.. -- ... ~ t ... ,'"
`..,"~...
`
`.,. ,-
`
`\- -
`
`-
`
`.. •.,....
`
`•
`•
`.
`•
`'
`' \'
`........
`........ _ -....
`... .. __ _
`(a)
`
`Bluetooth Radio System Architecture
`
`In th.is section the technical background of the Bluetooth
`radio system is presented. It describes the design trade-offs
`made in order to optimize the ad hoc functiona lity and
`addresses the issues listed above.
`Radio Spectrum
`The choice of radio spectrum is first determined by the Jack
`of operator interaction. The spectrum must be open to the
`public without the need for licenses. Second, the spectrum
`must be available worldwide. The first Bluetooth applications
`are targeted at the traveling businessperson who connects
`his/her portable devices wherever he/she goes. Fortunately,
`there is an unlicensed radio band that is globally available.
`This band, the Industrial, Scientific, Medical (lSM) band, is
`centered around 2.45 GHz and was formerly reserved for
`some professional user groups but has recently been opened
`worldwide for commercial use. In the United States, the band
`ranges from 2400 to 2483.5 MHz. and the FCC Part 15 regu(cid:173)
`lations apply. ln most parts of Europe,' the same band is
`available under the ETS-300328 regulations. ln Japan, recent(cid:173)
`ly the band from 2400 to 2500 MHz has been allowed for
`commercial applications and has been harmonized with the
`rest of the world. Summarizing. in most countries of the
`world, free spectrum is available from 2400 MHz to 2483.5
`MHz, and harmonization efforts are ongoing to have this
`radio band available truly worldwide.
`The regulations in different parts of the world differ. How(cid:173)
`ever, their scope is to enable fair access to the radio band by
`an arbitrary user. The regulations generally specify the
`spreading of transmitted signal energy and maximum allow(cid:173)
`able transmit power. For a system to operate globally, a radio
`concept has to be found that satisfies all regulations simulta(cid:173)
`neously. The result will therefore be the minimum denomina(cid:173)
`tor of all the requirements.
`Interference Immunity
`Since the radio band is free to be accessed by any radio trans(cid:173)
`mitter as long as it satisfies the regulations, interference
`immunity is an important issue. The extent and nature of the
`interference in tbc 2.45 GHz TSM band cannot be predicted.
`Radio transmitters may range, for example, from 10 dBm
`baby monitors to 30 dBm WLAN access points. With high
`probability, the different systems sharing the same band will
`not be able to commun.icate. Coordination is therefore not
`possible. More of a problem arc the high-power transmitters
`covered by the FCC part J8 rules which include, for example,
`microwave ovens and lighting devices. These devices fall out(cid:173)
`side the power and spreading regulations of part 15, but still
`coexist in the 2.45 GHz ISM band. In addition to interference
`from external sources, co-user interference must be taken into
`account, which resuJts from other Bluetooth users.
`Interference immunity can be obtained by interference
`suppression or avoidance. Suppression can be obtained by
`coding or direct-sequence spreading. However, the dynamic
`range of the interfering and intended signals in an ad hoc,
`uncoordinated radio environment can be huge. Taking into
`account the distance ratios and power differences of uncoordi(cid:173)
`nated transmitters, near-far ratios in excess of 50 dB are 110
`exception. With desired user rates on the order of 1 Mb/s and
`beyond. practically attained coding and processing gains are
`inadequate. Instead. interference avoidance is more attractive
`
`t 111 France am/ Spain the exact loc111io11 of the band differs, 1111d the band
`is smaller.
`
`(c)
`
`• Figure 1. Topologies for: a) cellular radio systems with squares
`representing stationary base stations: b) conventional ad hoc
`systems; and c) scatter ad hoc systems.
`
`since the desired signal is transmitted at points in frequency
`and/or time where interference is low or absent. Avoidance in
`time can be an alternative if the interference concerns a
`pulsed jammer and the desired signal can be interrupted.
`Avoidance in frequency is more practical. Since the 2.45 GHz
`band provides about 80 MHz of bandwidth and most radio
`systems are band-limited, with high probability a part of the
`radio spectrum can be found where there is no dominant
`interference. Filtering in the frequency domain provides the
`suppression of the interferers ar other parts of the radio band.
`The filter suppression can easily arrive at 50 dB or more.
`Multiple Access Scheme
`The selection of the multiple access scheme for ad hoc radio
`systems is driven by the lack of coordination and the regula(cid:173)
`tions in the ISM band. Frequency-division multiple access
`(FDMA) is attractive for ad hoc systems since channel orthog(cid:173)
`onality only relies 011 the accuracy of the crystal oscillators in
`the radio units. Combined with an adaptive or dynamic chan(cid:173)
`nel allocation scheme. interference can be avoided. Unfortu(cid:173)
`nately, pure FDMA does not fulfill the spreading
`requirements set in the ISM band. Time-division multiple
`access (TOMA) requires strict time synchronization for chan(cid:173)
`nel orthogonality. For multiple collocated ad hoc connections.
`maintaining a common timing reference becomes rather cum(cid:173)
`bersome. Code-division multiple access (CDMA) offers the
`best properties for ad hoc radio systems since it provides
`spreading and can deal with uncoordinated systems. Direct
`sequence (DS)-CDMA is less attractive because of the near(cid:173)
`far problem which requires coordinated power control or
`excessive processing gain. In addition, as in TDMA. DS(cid:173)
`CDMA channel orthogonality requires a common timing ref(cid:173)
`erence. FinalJy, for higher user rates, rather high chip rates
`are required, which is less attractive because of the wide
`bandwidth (interference immunity) and higher current con(cid:173)
`sumption. Frequency-hopping (FH)-CDMA combines a num(cid:173)
`ber properties which make it the best choice for ad hoc radio
`systems. On average the signal can be spread over a large fre(cid:173)
`quency range, but instantaneously only a small bandwidth is
`occupied, avoiding most of the potential interference in the
`ISM band. The hop carriers are orthogonal, anti the interfer(cid:173)
`ence on adjacent hops can effectively be suppressed by filter-
`
`lr:.EE Personal Communications • Fcbmary 2000
`
`29
`
`Petitioner's Exhibit 1005
`Page 005
`
`

`

`A [. I
`
`f(k)
`
`B
`
`1
`
`625 µs
`
`l
`
`1
`i•
`- - - - - -... --'------'----------) t
`.
`
`share the same channel. Bluetooth has been
`designed to allow a large number of independent
`channels, each channel serving only a limited num-
`ber of participants. With the considered modulation
`scheme. a single Fil channel in the ISM band only
`supports a gross bit rate of I Mb/s. This capacity has
`to be shared by all participants on the channel. The(cid:173)
`oretically, the spectrum with 79 carriers can support
`79 Mb.'s. In the user scenarios targeted by Bluc(cid:173)
`tooth. it is highly unlikely that all units in range
`need to share information among all of them. By
`using a large number of independent 1 Mb/s chan-
`nels to which only the units arc connected that real(cid:173)
`ly want to exchange information. the 80 MHz is exploited
`much more effectively. Due to nonorthogonality of the hop
`sequences, the theoretical capacity of 79 Mb/s cannot be
`reached, but is at least much larger than 1 Mb/s.
`An FH Bluetooth channel is associated with a piconet. tu.
`mentioned earlier. the piconct channel is defined by the identi(cid:173)
`ty (providing the hop sequence) a nd system clock (providing
`the hop phase) of a master unit. All other units participating in
`the piconet are slaves. Each Bluctooth radio unit has a free(cid:173)
`running system or native clock. There is not a common timing
`reference, but when a piconet is established, the slaves add off(cid:173)
`sets to their native clocks to synchronize to the master. These
`offsets arc released again when the piconet is cancelled, but can
`be stored for later use. Different channels have different mas(cid:173)
`ters and therefore also different hopping sequences anti phases.
`The number of units that can participate on a common channel
`is deliberately limited to eight (one master and seven slaves) in
`order to keep a high-capacity link between all the units. It also
`limits the overhead required for addressing. Bluetooth is based
`on peer communications. The master/slave role i~ only amibut(cid:173)
`ed to a unit for the duration of the piconet. When the piconct
`is cancelled. the master and slave roles arc cancelled. Each unit
`can become a master or slave. By definition. the unit that estab(cid:173)
`lishes the piconel becomes the master.
`In addition to defining the piconet. the master also controls
`the traffic on the piconet and takes care of access control.
`Access is completely contention free. The short dwell time of
`625 µsonly allows the transmission of a single packet. A con(cid:173)
`tenrion-bascd access scheme would provide too much over(cid:173)
`head and is not efficient in the short dwell time Bluetooth
`applies. I n Bluetooth, the master implements centralized con(cid:173)
`trol; only communication between the master and one or more
`slaves is possible. The time slots arc alternately used for mas(cid:173)
`ter transmission and slave transmission. In the master trans(cid:173)
`mission. the master includes a slave addniss of the unit for
`which the information is intended. I n order to prcvcnc colli(cid:173)
`sions on the channel due to multiple slave transmissions. the
`master applies a polling technique: for each slave-to-master
`slot. the master decides which slave is allowed to transmit. This
`decision is performed on a per-slot ha,is: on ly the slave
`addressed in the master-to- slave slot directly preceding the
`slave-to-master slot is allowed to transmit in this slave-to-mas(cid:173)
`ter slot. If the master has information to send to a specific
`slave. this slave is polled implicitly anti can return information.
`If the master has no information to send. it has to poll the
`slave explicitly with a short poll packet. Since the master
`schedules the traffic in both the uplink and downlink, intelli(cid:173)
`gent scheduling algorithms have to be used that take into
`account Lhc slave characteristics. The master control effectively
`prevents collisions between the participants on the piconet
`channel. Independent collocated piconcts may interfere when
`they occasionally use the same hop carrier. A type of ALOHA
`is applied: information is transmitted without checking for a
`clear carrier (no listen-before-talk). If the information is
`
`f(k + 1)
`
`f(k + 2)
`
`: .•
`
`____ .___ ____________ .__ __ ~_, t
`
`• Figure 2. A11 i1111Strt1tio11 of the Fl I TDD clw1111el applied i11 8/uetooth.
`
`ing. The hop sequences will not be orthogonal (coordination
`of hop sequences is not allowed by the fCC rules anyway),
`but narrowband a nd co-user interference is experienced as
`short interruptions in the communications. which can be over(cid:173)
`come with measures at higher-layer protocols.
`Bluetooth is based on FH-CDMA. In the 2.45 GHz ISM
`band. a set of 79 hop carriers have been defined at a I MHz
`spacing." The channel is a hopping channel with a nominal
`hop dwell time of 625 µs. A large number of pseudo-random
`hopping sequences have been defined. The particular
`sequence is determined by the uni1 that controls the Fl-I chan(cid:173)
`nel. which is called the master. The native clock of the master
`unit also defines the phase in the hopping sequence. All other
`participants on the hopping channel are slaves: they use the
`master identity to select the same hopping sequence and add
`time offsets to their respective native clocks to synchronize to
`the frequency hopping. In the time domain, the channel is
`divided into slots. The minimum dwell time of 625 µs corre(cid:173)
`sponds to a single slot. To simplify implementation, full(cid:173)
`duplex communications is achieved by applying time-division
`duplex (TOD). This means that a unit alternately transmits
`and receives. Separation of transmission and reception in time
`effectively prevents crosstalk between the transmit anti receive
`operations in the radio transceiver, which is essential if a one(cid:173)
`chip implementation is desired. Since transmission and recep(cid:173)
`tion take place at different time slots. transmission and
`reception also take place at different hop carriers. Figure 2
`illustrates the FH/TDD channel applied in Bluetooth. Note
`that multiple a d hoc links will make use of different hopping
`channels with different hopping sequences and may have mis(cid:173)
`aligned slot timing.
`The Modulation Scheme
`In the ISM band. the signal bandwidth of FIi systems is limit(cid:173)
`ed to I Ml lz. For robustness. a binary modulation scheme was
`chosen. With the above-mentioned bandwidth restriction, the
`data rates arc limited to about I Mb/s. For FH systems and
`support for bursty data traffic, a noncohercnt detection
`scheme is most appropriate. Bluctooth uses Gaussian-shaped
`frequency shift keying (FSK) modulation with a nominal mod(cid:173)
`ulation index of k = 0.3. Logical ones are sent as positive fre(cid:173)
`quency deviations, logical zeroes as negative frequency
`deviation~. Demodulation can simply be accomplished by a
`limiting FM discriminator. This modulation scheme allows the
`implementation of low-cost radio units.
`Medium Access Control
`Bluetooth has been optimized to allow a large number of
`uncoordinated communications to take place in the same
`a rea. Unlike other ad hoc solutions where all units in range
`
`1 C111Tently. for France a11tl Spain a reduced set of 23 hop carriers has been
`defined at a I .".fl /z carrier spacing.
`
`30
`
`IEEE Personal Communications • Fchruary 2000
`
`Petitioner's Exhibit 1005
`Page 006
`
`

`

`54 bits
`
`0-2745 bits
`,--------------------,
`
`Packet
`header
`
`Payload
`
`Access
`code
`
`• Figure 3. The format of packets applied in Bluetooth.
`
`have been defined, as will be further explained later. The
`interpretation of packet type is different for synchronous and
`asynchronous links. Currently, asynchronous links support
`payloads with or without a 2/3-rate FEC coding scheme. In
`addition, on these links single-slot, three-slot, and five-slot
`packets are available. The maximum user rate that can be
`obtained over the asynchronous link is 723.2 kb/s. In that
`case, a return link of 57.6 kb/scan still be supported. Link
`adaptation can be applied on the asynchronous link by chang(cid:173)
`ing the packet length and FEC coding depending Oil link COil·
`ditions. The payload length is variable and depends on the
`available user data. However, the maximum length is limited
`by the minimum switching time between RX and TX. which
`is specified at 200 µs. This switching time seems large, but
`allows the use of open-loop voltage controlled oscillators
`(VCOs) for direct modulation and provides time for packet
`processing between RX and TX; this is also discussed later.
`For synchronous links, only single-slot packets have been
`defined. The payload length is fixed. Payloads with 1/3-rate
`FEC, 2/3-rate, or no FEC are supported. The synchronous
`link supports a full-duplex link with a user rate of 64 kb/sin
`both directions.
`
`Physical Link Definition
`The Bluetooth link supports both synchronous services such
`as voice traffic, and asynchronous services such as bursty data
`traffic. Two physical link types have been defined:
`• The synchronous connection-oriented (SCO) link
`• The asynchronous connectionless (ACL) link
`The SCO link is a point-to-point link between the master
`and a single slave. The link is established by reservation of
`duplex slots at regular intervals. The ACL link is a point-to(cid:173)
`mu ltipoint link between the master and all the slaves on the
`piconet. The ACL link can use all of the remaining slots on
`the channel not used for SCO links. The traffic over the
`ACL link is scheduled by the master. T he slotted structure
`of the piconet channel allows effective mixing of the syn(cid:173)
`chronous and asynchronous links. An example of a channel
`
`f(k + 1)
`
`f(k + 2)
`
`f(k + 3)
`
`f(k + 4)
`
`f(k + 5)
`
`' I
`
`'
`
`TX
`
`RX
`
`f(k)
`
`TX
`
`RX
`
`f(k + 3)
`
`RX
`
`I
`
`'
`
`TX
`
`RX
`
`f(k + 4)
`
`f(k + 5)
`
`I
`
`TX
`
`RX
`
`------:-:--------~-f(-~-+-5)"""7
`
`received incorrectly, it is retransmitted at the next
`transmission opportunity (for data only). Due to the
`short dwell time, collision avoidance schemes are
`less appropriate for FH radio. For each hop, differ(cid:173)
`ent contenders are encountered. Backoff mecha(cid:173)
`nisms are therefore less efficient.
`Packet-Based Communications
`The Bluetooth system uses packet-based transmission: the
`information stream is fragmented into packets. In each slot,
`only a single packet can be sent. All packets have the same
`format, starting with an access code, followed by a packet
`header, and ending with the user payload (Fig. 3).
`The access code has pseudo-ralldom properties and is used
`as a direct-sequence code in certain access operations. The
`access code includes the identity of the piconet master. All pack(cid:173)
`ets exchanged on the channel are identified by this master iden(cid:173)
`tity. Only if the access code matches the access code
`corresponding to the piconet master will the packet be accepted
`by the recipient. This prevents packets sent in one piconet false(cid:173)
`ly being accepted by units of another piconet that happens to
`land on the same hop carrier. In the receiver, the access code is
`matched against the anticipated code in a sliding correlator.
`This correlator provides the direct-sequence processing gain.
`The packet header contains link control in