`
`DECLARATION OF Alex Planidin
`
`I, Alex Planidin, hereby declare as follows:
`
`1.
`
`I am a Freelance Vendor at TransPerfect, Inc.
`
`2.
`
`I submit this declaration to certify the accuracy of the English translation the
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`Swedish front matter attached to Peter Ekstrom’s Masters Thesis. The thesis itself was already
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`in English when it was given to me.
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`3.
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`My statements are based on personal knowledge and my review of the front
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`matter of the Masters Thesis that is written in Swedish and its Swedish-to-English translation. If
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`called as a witness about the facts contained in these statements, I could testify competently
`
`based on such personal knowledge and the investigation I have conducted.
`
`4.
`
`Attached as Exhibit A is a true and accurate copy of Peter Ekstrom’s Masters
`
`Thesis, including the front matter that is written in Swedish I did not review the substance of the
`
`Thesis itself.
`
`5.
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`Attached as Exhibit B is a true and accurate copy of an English translation of
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`front matter preceding Peter Ekstrom’s Masters Thesis.
`
`6.
`
`The English translation of the front matter is a true and accurate translation from
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`Swedish into English. I have no other opinions or statements regarding the Peter Ekstrom’s
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`Masters Thesis.
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`7.
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`All statements made herein of my own knowledge are true, and all statements
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`made on information and belief are believed to be true. Further, I am aware that these statements
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`are made with the knowledge that willful false statements and the like so made are punishable by
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`fine or imprisonment, or both, under 18 U.S.C. § 1001. I declare under penalty of perjury that to
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`the best of my knowledge, the foregoing is true and correct.
`
`

`

`8.
`
`I also understand that by submitting this declaration I may be asked to appear for
`
`a deposition asking me questions limited to the material in my declaration. With my signature
`
`below, I agree to make reasonable efforts to make myself available for such a deposition at a
`
`reasonable place and time of my choosing.
`
`* * *
`
`I declare under penalty of perjury that the foregoing is true and correct to the best
`
`of my knowledge. Executed on January 25, 2018 in London, United Kingdom
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`Alex Planidin
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`
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`Exhibit A
`
`Exhibit A
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`Jaguar Land Rover
`Exhibit 1012
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`Page 003
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`

`

`Examensarbete
`LiTH-ITN-KTS-EX--02/21--SE
`
`
`
`
`
`
`Audio over Bluetooth and
`MOST
`
`
`
`
`Peter Ekström &
`Fredrik Hoel
`
`2002-03-07
`
`
`
`
`
`Department of Science and Technology
`Linköping University
`SE-601 74 Norrköping, Sweden
`
`Institutionen för teknik och naturvetenskap
`Linköpings Universitet
`601 74 Norrköping
`
`

`

`
`LiTH-ITN-KTS-EX--02/21--SE
`
`Audio over Bluetooth and
`MOST
`
`
`Examensarbete utfört i kommunikationssystem
`vid Linköpings Tekniska Högskola, Campus Norrköping
`
`
`Peter Ekström
`Fredrik Hoel
`
`
`
`
`
`Handledare: Thomas Söderqvist
`Examinator: Johan M Karlsson
`
`Norrköping den 2002-03-07
`
`
`
`
`
`
`
`
`
`

`

`Avdelning, Institution
`Division, Department
`
`Institutionen för teknik och naturvetenskap
`Department of Science and Technology
`
`Datum
`Date
`
`2002-03-20
`
`Språk
`Language
`
`Rapporttyp
`Report category
`
`Svenska/Swedish
`X Engelska/English
`
`_ ________________
`
`Licentiatavhandling
`X Examensarbete
`C-uppsats
`D-uppsats
`Övrig rapport
`
`ISBN
`____________________________________________
`_________
`ISRN LiTH-ITN-KTS-EX--02/21--SE
`_________________________________________________________________
`ISSN
`Serietitel och serienummer
`Title of series, numbering
`___________________________________
`
`_ ________________
`
`URL för elektronisk version
`
`Titel
`
`Title
`
`Ljud över Bluetooth och MOST
`
`Audio over Bluetooth and MOST
`
`Författare
`Authors
`Peter Ekström and Fredrik Hoel
`
`Sammanfattning
`I detta examensarbete studeras möjligheten att ansluta standardprodukter trådlöst till MOST, ett multimedianätverk för fordon. Den trådlösa
`tekniken som analyseras är Bluetooth. Rapporten beskriver teoretiskt hur MOST ska integreras med Bluetooth via en gateway och tar även upp
`olika framtida scenarier som möjliggörs med hjälp av denna gateway. Lösningen beskriver hur en förbindelse kan upprättas och ljuddata överföras
`från en ljudkälla till MOST-nätet med hjälp av Bluetooth-teknik.
`
`Abstract
`In this Master Thesis the possibility of connecting standard products wirelessly to MOST, a multimedia network for vehicles, is investigated. The
`wireless technique analysed is Bluetooth. The report theoretically describes how MOST could be integrated with Bluetooth via a gateway. Future
`scenarios that are made possible by this gateway are also described. The solution describes how a connection could be established and how the
`synchronous audio is transferred from a Bluetooth sound source to the MOST network.
`
`Nyckelord
`Trådlös, Bluetooth, MOST, samplingsfrekvenskonvertering, interpolation
`
`Keywords
`Wireless, Bluetooth, MOST, sample rate conversion, interpolation
`
`II
`
`

`

`Abstract
`
`In this Master Thesis the possibility of connecting standard products wirelessly to
`MOST, a multimedia network for vehicles, are investigated. The wireless technique
`analysed is Bluetooth. The report theoretically describes how Bluetooth could be
`integrated with MOST via a gateway. Future scenarios that are made possible by this
`gateway are also described. The solution presents how a connection could be
`established and how the synchronous audio is transferred from a Bluetooth sound
`source to the MOST network.
`
`As a sound source equipment supporting the Bluetooth Headset Profile is used. It
`communicates with the MOST network via a gateway. As the recipient of the system,
`a speaker module connected to MOST is used.
`
`The gateway task when transmitting audio, using synchronous data, is to convert the
`sample rate of the audio stream from 8 kHz used in the Bluetooth system to 48 kHz
`used in MOST. This is done by interpolation and filtering. Several different methods
`for this are described and compared.
`
`The key issue in this report is the sample rate conversion between the two systems
`sample frequencies.
`
`III
`
`

`

`Sammanfattning
`
`I detta examensarbete studeras möjligheten att ansluta standardprodukter trådlöst till
`MOST, ett multimedianätverk för fordon. Den trådlösa tekniken som analyseras är
`Bluetooth. Rapporten beskriver teoretiskt hur Bluetooth ska integreras med MOST via
`en gateway och tar även upp olika framtida scenarier som möjliggörs med hjälp av
`denna gateway. Lösningen beskriver hur en förbindelse kan upprättas och ljuddata
`överföras från en ljudkälla till MOST-nätet med hjälp av Bluetooth-teknik.
`
`Som ljudkälla används utrustning som stöder ’Bluetooth Headset Profile’. Den
`kommunicerar via en gateway med MOST-nätet. Som mottagare i systemet finns en
`högtalarmodul ansluten till MOST.
`
`form av synkron data, är gatewayens uppgift att
`i
`Vid överföring av ljud,
`samplingskonvertera ljudströmmen från 8 kHz som används i Bluetooth-delen till 48
`kHz som används på MOST. Detta sker med interpolation och filtrering. Flera olika
`metoder för detta redovisas och jämförs.
`
`Huvuduppgiften i rapporten är samplingskonverteringen mellan de olika systemens
`samplingsfrekvenser.
`
`IV
`
`

`

`Preface
`
`This report presents the results of our Master Thesis performed at Volvo
`Technological Development Corporation.
`
`We would like to thank all of the people supporting us during our work in the
`department of Infotronics at Volvo Technological Development. We would also like
`to thank our examiner Johan M Karlsson at Linköping University of Technology. A
`special thanks goes to Thomas Söderqvist for his invaluable support and his great
`knowledge of both the Bluetooth and the MOST technologies.
`
`Göteborg, Mars 1, 2002
`
`Peter Ekström and Fredrik Hoel
`
`V
`
`

`

`Contents
`
`2
`
`1
`
`INTRODUCTION ............................................................................................1
`1.1
`BACKGROUND .............................................................................................1
`1.2 METHOD .....................................................................................................1
`LIMITATIONS ...............................................................................................1
`1.3
`STRUCTURE OF THE THESIS..........................................................................2
`1.4
`BLUETOOTH ..................................................................................................3
`INTRODUCTION............................................................................................3
`2.1
`2.1.1
`The name ............................................................................................3
`2.1.2
`The product.........................................................................................3
`ORGANISATION ...........................................................................................4
`2.2
`CHARACTERISTICS.......................................................................................4
`2.3
`2.3.1
`Network topology................................................................................6
`THE BLUETOOTH PROTOCOL STACK.............................................................6
`2.4
`2.4.1
`Baseband ............................................................................................7
`2.4.2
`Link Manager .....................................................................................8
`2.4.3
`Host Controller Interface (HCI)..........................................................8
`2.4.4
`L2CAP ................................................................................................8
`2.4.5
`RFCOMM ...........................................................................................8
`PROFILES.....................................................................................................9
`2.5
`2.5.1
`Generic Access Profile (GAP).............................................................9
`2.5.2
`Serial Port Profile (SPP)...................................................................10
`2.5.3
`Service Discovery Application Profile (SDAP) ..................................10
`2.5.4
`Generic Object Exchange Profile (GOEP) ........................................10
`2.5.5
`Headset Profile (HP) ........................................................................10
`2.5.6
`Telephony Control protocol Specification (TCS) ...............................11
`2.5.7
`Dial Up Networking Profile (DUNP) ................................................11
`2.5.8
`LAN Access Profile (LANAP) ............................................................11
`2.5.9
`Fax Profile (FaxP)............................................................................11
`FUTURE.....................................................................................................12
`2.6
`3 MOST .............................................................................................................13
`INTRODUCTION..........................................................................................13
`3.1
`ORGANISATION .........................................................................................14
`3.2
`CHARACTERISTICS.....................................................................................15
`3.3
`3.3.1
`Bandwidth.........................................................................................15
`3.3.2
`Control data......................................................................................16
`3.3.3
`Asynchronous data............................................................................16
`3.3.4
`Synchronous data..............................................................................16
`3.4 MOST SYSTEM SERVICES .........................................................................17
`3.4.1
`NetServices .......................................................................................17
`3.4.2
`FBlocks.............................................................................................18
`3.4.3
`Low Level System Service..................................................................19
`FUTURE.....................................................................................................21
`3.5
`
`VI
`
`

`

`5
`
`6
`
`4
`
`DIGITAL SIGNAL PROCESSING ..............................................................22
`SAMPLING .................................................................................................22
`4.1
`4.1.1
`Aliasing.............................................................................................23
`4.2
`PCM.........................................................................................................23
`SAMPLE RATE CONVERSION........................................................................24
`4.3
`4.3.1
`Converting with arbitrary numbers ...................................................24
`4.3.2
`Polyphase structure ..........................................................................25
`FILTER ......................................................................................................26
`4.4
`4.4.1
`Filter characteristics.........................................................................26
`4.4.2
`Different types of filters.....................................................................27
`4.4.3
`Digital filters.....................................................................................28
`INTERPOLATION METHODS .........................................................................30
`4.5
`4.5.1
`Linear interpolation ..........................................................................30
`4.5.2
`Sinc interpolation..............................................................................31
`4.5.3
`FFT interpolation .............................................................................31
`4.5.4
`Zero-filling interpolation...................................................................32
`SYSTEM DESIGN OF AUDIO SOURCE ....................................................33
`FUNCTIONAL REQUIREMENTS.....................................................................34
`5.1
`AUDIO REQUIREMENTS ..............................................................................34
`5.2
`SYSTEM DESIGN OF GATEWAY..............................................................35
`SPECIFIC GATEWAY...................................................................................35
`6.1
`6.1.1
`Higher Level Gateway approach.......................................................36
`CONTROL DATA .........................................................................................37
`6.2
`6.2.1
`Establishing synchronous connection from Bluetooth headset ...........38
`6.2.2
`Disconnecting from Bluetooth headset ..............................................39
`6.2.3
`Establishing synchronous connection from MOST.............................40
`6.2.4
`Disconnecting from MOST................................................................41
`SYNCHRONOUS AUDIO...............................................................................42
`6.3
`6.3.1
`Bluetooth part ...................................................................................42
`6.3.2
`SRC part ...........................................................................................42
`6.3.3
`MOST part........................................................................................45
`GENERAL GATEWAY..................................................................................46
`6.4
`6.4.1
`Scenarios ..........................................................................................46
`IMPLEMENTATION......................................................................................49
`6.5
`6.5.1
`Results ..............................................................................................49
`CONCLUSION...............................................................................................51
`CONTROL DATA .........................................................................................51
`7.1
`SYNCHRONOUS AUDIO...............................................................................51
`7.2
`FUTURE WORK...........................................................................................52
`7.3
`REFERENCES.......................................................................................................53
`ABBREVIATIONS ................................................................................................55
`APPENDIX A: FREQUENCY SPECTRUMS......................................................57
`
`7
`
`VII
`
`

`

`1 Introduction
`
`The aim of this Thesis is to design a gateway between Bluetooth and MOST, Media
`Oriented Systems Transport. The gateway shall be able to handle control data to
`initiate a synchronous link and to route synchronous audio sent from Bluetooth to
`MOST.
`
`1.1 Background
`MOST is already an established technology in the automotive industry and Bluetooth
`is becoming more and more interesting. Combining those techniques would bring the
`possibilities further to another level where the applications in the vehicle can connect
`wirelessly. As a step in this evolution Volvo Technological Development is interested
`in developing competence in this area.
`
`1.2 Method
`The method used throughout this Master Thesis has been an iterative process. The
`first thing done was a target plan. It contained the different goals, a time plan etc.
`Then a literature study was made in which the Bluetooth and MOST technologies
`were studied. Previous reports in the area of Bluetooth, performed at Volvo
`Technological Development, were read [20, 21]. The task was separated into smaller
`tasks where the solution ideas were backed up by more thorough studies of
`specifications, books and articles. In the later part of the Master Thesis the area of
`Digital Signal Processing (DSP) was investigated. Finally the results and the solutions
`along with the descriptions of the different technologies were written down in this
`Thesis.
`
`1.3 Limitations
`There is no implementation description of the achieved solutions to this task. The
`work is done on a theoretical level were the possibility of interconnecting Bluetooth
`with MOST is investigated.
`
`Security and error handling are areas that have to be considered more careful in a real
`system implementation.
`
`1
`
`

`

`1.4 Structure of the Thesis
`Chapter 2, 3 and 4 are descriptions of the technologies of Bluetooth, MOST and DSP
`respectively. Those chapters could be skipped if the reader is familiar with those
`areas.
`
`Chapter 5 describes the system design of the audio source.
`
`In chapter 6 a specific gateway for this Master thesis is discussed as well as the
`descriptions of how control data and synchronous audio is supposed to be handled by
`this gateway. A general Bluetooth-MOST gateway and some future scenarios for this
`are also presented in this chapter.
`It ends by a description of a simplified
`implementation done.
`
`Chapter 7 contains the conclusions and includes the future works of this report.
`
`The appendix consists of frequency spectrums from interpolation simulations.
`
`2
`
`

`

`2 Bluetooth
`
`This chapter will describe an overview of the Bluetooth history, organization and
`technology. The Bluetooth specification 1.1 has been the main source of this chapter.
`
`2.1 Introduction
`The Bluetooth technology has quite an exiting history though the idea of Bluetooth
`came up as late as 1994. Because of its origin, Bluetooth is strongly associated with
`Scandinavian culture and history.
`
` %0 3,20
`
`The engineers named the technology to honour the tenth century Viking king of
`Denmark. His name was Harald Blåtand, which translates into English as Harold
`Bluetooth. Harold became known as the king who united Denmark and Norway and
`christened the Vikings in his kingdom. Due to Harold’s talent for diplomacy the
`Ericsson engineers thought it would be a good name for a technology that will unite
`the data- and telecommunications industry. Bluetooth has gathered multinational
`companies into the Bluetooth SIG (Special Interest Group).
`
` %0 574/:.9
`
`The technology was primary meant to be a cable replacement between different kinds
`of devices. Ericsson had 1994 a short link radio vision where they desired a power
`efficient and platform independent radio module. This cable replacement technology
`was going to have the following preferences:
`
`• Be perfect for mobile devices (small, low power, low cost, low weight)
`• Have short range distance
`• Guarantee interoperability
`• Open specification
`• Ad hoc connectivity
`
`The engineering work started 1995 but it was not until 1997 when Ericsson realized
`that they had to collaborate with other large companies if this technology was going to
`be a widespread success. Ericsson established Bluetooth SIG founder group together
`with Intel, IBM, Nokia and Toshiba. Gradually the SIG grew and the SIG promoter
`group was formed with the founders, 3COM, Lucent, Microsoft and Motorola [24].
`The collaboration between that many large companies has made Bluetooth an open
`standard.
`
`3
`
`

`

`2.2 Organisation
`Bluetooth SIG today consists of different member levels. From the beginning the
`Bluetooth name was a trademark owned by the Ericsson telephone company.
`Nowadays the Bluetooth name is owned by the Bluetooth SIG. The membership is
`divided into four levels:
`
`• Promoters
`• Associates
`• Adopters
`• Early Adopters
`
`The tasks of the different member levels are described in Figure 1.
`
`Program
`Management Board
`
`Promoter
`
`Associate
`
`Early Adoptor
`
`Independent
`
`Regulatory
`
`Legal Committee
`
`Management Service
`
`Marketing
`
`Qualification Board
`
`RF Regulations
`
`China Regulations
`
`Test and Interop
`
`Architecture Review
`Board
`
`Subgroups
`
`BTAB
`
`Aviation Regulations
`
`Security Regulations
`
`Japan Regulations
`
`Technical
`Working Groups
`
`Expert Groups
`
`Errata Owner and
`Review pool
`
`BQA
`
`BQB
`
`Figure 1: Bluetooth SIG structure
`
`2.3 Characteristics
`The Bluetooth radio is transmitting on the globally unlicensed frequency starting at
`2,402 GHz and stopping at 2,480GHz. Bluetooth uses a frequency hop technology
`with 79 hops displaced by 1 MHz. The maximum hopping rate is 1600 hops per
`second. The frequency hopping procedure follows a scheme generated by the master
`(see 2.3.1). Frequency hopping helps the Bluetooth radio to avoid interference with
`other devices [1].
`
`is easy to implement Bluetooth everywhere without complications with
`It
`governmental, military or other kind of frequency restrictions. One complication is
`that Bluetooth transmits on the same frequency as other products like microwave
`4
`
`

`

`ovens and WLAN adapters. This could lead to undesired interference [22].
`In a Bluetooth network 8 devices can be simultaneously active. This is called a
`piconet. To connect more devices it is possible to connect up to 10 piconets into a
`scatternet [25]. The gross data rate is 1 Mbps but the net data rate is maximum 432,6
`kbps symmetric duplex and 723,2 kbps asymmetric duplex. For voice it is possible to
`have 3 simultaneous synchronous duplex connections per piconet. The Bluetooth
`technology specifies 3 power classes presented in Table 1.
`
`Power Class Maximum Output Power
`1
`100 mW (20 dBm)
`2
`2.5 mW (4 dBm)
`3
`1 mW (0 dBm)
`
`Range
`~100 meters
`~35 meters
`~10 meters
`
`Table 1:Bluetooth Power Classes
`
`The range values in Table 1 depend on the antenna construction and if the devices are
`in line of sight or not. It is only the power that is specified in the specification [13].
`
`When Bluetooth is transmitting voice it does not resend lost or corrupt packages.
`There are three formats supported for the air-coded signal: A-Law, µ-Law and CVSD.
`The logarithmic encodings (A-Law and µ-Law) are not yet supported by any Profile
`but are implemented for eventual future use. The audio subsystem is described in
`chapter 5.2.
`
`CVSD is the most common encoding format in Bluetooth devices. It is a robust voice
`encoding format that follows the waveform of the signal and is very resistant to bit
`errors. The bit-errors are noticeable as background-noise. When the bit-error rate
`increases there will be more background-noise. Figure 2 shows a CVSD encoded
`signal trying to follow the original continuous signal.
`
`1 1 0 0 0 0 0 1 0 1 1 1 1 1 1 0 0 0 0 1 0
`
`Figure 2: CVSD encoded signal
`
`5
`
`

`

` 0947 94544
`
`The Bluetooth devices within the range of communication can build up a so-called ad
`hoc network. In difference to many other wireless systems, which have stationary
`transceivers, all Bluetooth devices in the network are equal except from the Master,
`which provides the clock etc. The different topologies are shown in Figure 3.
`
`Slave
`Master
`
`Single-slave
`piconet
`
`Multi-slave
`piconet
`
`Scatternet
`
`Figure 3: Bluetooth topology structures
`
`2.4 The Bluetooth Protocol Stack
`The Bluetooth specification contains a protocol stack that defines how the devices are
`supposed to locate, connect to and exchange data with each other. Figure 4 shows the
`Bluetooth stack mapped towards the OSI (Open Systems Interconnect) reference
`model [2].
`
`Application
`Presentation
`
`Session
`
`Transport
`
`Network
`
`Datalink
`
`Physical
`
`OSI Reference Model
`
`Applications
`
`RFCOMM/SDP
`
`L2CAP
`Host Controller Interface (HCI)
`
`Link Manager
`
`Baseband
`
`Radio
`
`Bluetooth
`
`Figure 4: OSI -Bluetooth
`
`In the following chapter the Bluetooth stack components will be described, starting
`with the Bluetooth Baseband and ending with the Bluetooth Profiles. The radio
`properties is mentioned in the chapter 2.3.
`
`6
`
`

`

` ,80-,3/
`
`The Baseband supports both synchronous and asynchronous data [9]. The
`synchronous link can contain both audio and data while the asynchronous link carries
`data and coded audio and video. Data packets can be provided with different kind of
`error correction. HEC, FEC and CRC are previously explained and they are mainly
`used for asynchronous data. The SCO (Synchronous Connection Oriented) links
`allows point-to-point communication between the slave and the master and the ACL
`(Asynchronous ConnectionLess) links also allows point-to-multipoint communication
`between the master and the slaves in the piconet. There are numerous functions that
`the Baseband handles. The main function is to control the link. Some of the other
`functions are:
`
`• Clock supplying
`• Frequency hop selection
`• Paging and inquiry
`• Security algorithms
`
`As mentioned above there are two different kinds of links: ACL and SCO links. These
`two link types have different kind of packets in the Baseband protocol. When an SCO
`link is established the audio data is put in the voice field. The voice field has fixed
`length and no header. The voice can be High-quality voice (HV) or Data Voice (DV).
`The HV field has a length of 240 bits and the DV field has 80 bits. The asynchronous
`data field is divided into three segments: payload header, payload body and a CRC
`code. The Baseband packet can also mix ACL and SCO packets. The Baseband
`packet structures are illustrated in Figure 5.
`
`54 bits
`72 bits
`Accesscode Header
`
`0 - 2745 bits
`Payload
`
`Payload Header
`
`Payload data
`
`CRC
`
`ACL packet and payload structure
`
`54 bits
`72 bits
`Accesscode Header
`
`0 - 240 bits
`Payload
`
`SCO packet structure
`Figure 5: Bluetooth Baseband packet structure
`
`The data- and voice transfer is designed to be robust. The data packets can have the
`following error correction and detection:
`
`reQuest)
`
`that automatically resends corrupt
`
`• ARQ (Automatic Repeat
`packages.
`• FEC (Forward Error Correction), which is a technique that is used to obtain
`optimal performance. It provides more bandwidth efficient ways to improve
`the bit error rate.
`• CRC (Cyclic Redundancy Checksum) for detecting bit errors.
`• HEC (Header Error Correction) a CRC function performed on the header.
`
`7
`
`

`

` 3 ,3,07
`
`To manage a Bluetooth link between the devices in the network the Link Manager is
`used. It handles the establishment of the ACL and the SCO links. The Link Manager
`governs also things like security, power, QoS (Quality of Service), transmission
`scheduling etc.
`
` 489 4397407 39071,.0 $%
`
`The HCI provides a command interface to the Baseband and the Link Manager. It also
`makes the hardware status and control registers accessible. In some systems where
`there are two main processors the HCI is the link between the systems. If a system has
`an embedded stack the HCI is not present. The interface is meant to provide a uniform
`way to access the Baseband capabilities. This simplifies the integration for different
`manufactures. The important
`issue is
`to create a driver
`that handles
`the
`communication between the hardware integrated layers and the layers above such as
`L2CAP etc.
`
` !
`
`The Bluetooth specification includes a Logical Link Control and Adaptation Protocol
`(L2CAP). The L2CAP provides higher-level protocols with multiplexing and packet
`segmentation and reassembly (SAR). L2CAP permits higher-level protocols and
`applications to transmit and receive data ACL packets up to 64 kilobytes. SCO links
`are not supported in L2CAP. They are supported by the Baseband.
`
`One of the most important L2CAP functions is protocol multiplexing. The protocol
`multiplexing is essential because of the separation of the upper layers. The data packet
`has to go through L2CAP because the Baseband protocol does not support a type field
`to identify higher protocols like SDP (Service Discovery Protocol), RFCOMM and
`TCS (See section 2.5.6). The other main function is SAR that divides the higher-level
`packets before transmission and then reassembles the packages after reception. The
`SAR is used to improve efficiency by supporting a maximum transmission unit
`(MTU) using larger packets than the largest Baseband packet.
`
`Another function that L2CAP handles is QoS. During the connection process L2CAP
`allows exchange of information regarding QoS between the Bluetooth devices. The
`L2CAP ensures that the QoS contracts are enforced.
`
` # 
`
`The Bluetooth is a standard for replacing cables. The RFCOMM protocol emulates a
`serial cable using the RS-232 nine-circuit serial port standard [2]. RFCOMM relies on
`the Baseband to provide reliable sequenced data streams. The data stream rate will be
`limited where there are physical serial ports involved. If there are just Bluetooth
`devices in the network, RFCOMM will deliver the highest possible data rate.
`RFCOMM is included in many of the Bluetooth Profiles.
`
`8
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`

`

`2.5 Profiles
`To make the Bluetooth standard universal the Bluetooth SIG identified various usage
`models. The different usage models are implemented in so called “profiles”. A profile
`defines specific messages and procedures used to implement a feature. Some features
`are mandatory, others are optional and some may be conditional. In the Bluetooth SIG
`there are many workgroups, in which new profiles are developed. In Figure 6 the
`Bluetooth profile hierarchy is illustrated [14].
`
`Generic Access Profile
`
`Telephony Control Protocol Specification
`
`Service Discovery Application Profile
`
`Cordless Telephony Profile
`
`Intercom Profile
`
`Serial Port Profile
`
`Dial-Up Networking Profile
`
`FAX Profile
`
`Headset Profile
`
`LAN Access Profile
`
`Generic Object Exchange
`
`File Transfer Profile
`
`Object Push Profile
`
`Synchronisation Profile
`
`Figure 6: Bluetooth Profile Hierarchy
`
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`
`This profile is the most basic of the Bluetooth profiles. All the other profiles are based
`upon it and use its facilities. The GAP defines procedures for Bluetooth devices when
`they want to connect, discover identities, set up security etc. There are four different
`modes of operation defined [10]:
`
`• Discoverability (non-discoverable, limited discoverable and general
`discoverable)
`• Connectability (connectable and non-connectable)
`• Pairability (pairable and non-pairable )
`• Security (non-secure, service level enforced security and link level enforced
`security)
`
`There are also other parameters that are governed by this profile. Preferences like
`Bluetooth device name, Bluetooth PIN and Class of Device are set to simplify the
`communication and the user interface. The parameters set in the GAP are called
`common parameters and must be supported in every Bluetooth device in order to
`work in a Bluetooth network.
`
`9
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`

` $07, !479 !7410 $$!!%
`
`Bluetooth was from the beginning and is still a technology for cable replacement. The
`serial port profile provides RS-232 cable emulation and is based upon GSM standard
`GSM 07.10 which allows multiplexing of numerous serial connections over one link.
`It is not just computers, PDA’s and cellular phones that uses the SPP. Profiles like
`Headset, Dial Up Networking and Generic Object Exchange are built upon the SPP.
`
`To provide a virtual serial port the SPP depends on the lower layers in the Bluetooth
`stack hierarchy. RFCOMM is used to create an L2CAP channel. There are numerous
`steps t