bluetooth: 1.applications, technology
DESCRIPTION
Bluetooth: 1.Applications, Technology. And Performance. Bluetooth. A cable replacement technology 1 Mb/s symbol rate Range 10+ meters Single chip radio + baseband at low power & low price point ($5). Why not use Wireless LANs? - power - cost. 802.11. Replacement for Ethernet - PowerPoint PPT PresentationTRANSCRIPT
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Bluetooth: 1.Applications, Technology
And Performance
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Bluetooth
A cable replacement technology 1 Mb/s symbol rate Range 10+ meters Single chip radio + baseband
at low power & low price point ($5)
Why not use Wireless LANs?- power- cost
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802.11
Replacement for Ethernet Supported data rates
11, 5.5, 2, 1 Mbps; and recently up to 20+Mbps @ 2.4 GHz up to 54 Mbps in 5.7 GHz band (802.11 a)
Range Indoor 20 - 25 meters Outdoor: 50 – 100 meters
Transmit power up to 100 mW Cost:
Chipsets $ 35 – 50 AP $200 - $1000 PCMCIA cards $100 - $150
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Cordlessheadset
Emerging Landscape
Which option is technically superior ? What market forces are at play ? What can be said about the future ?
802.11 Bluetooth
LAN AP
802.11b for PDAs Bluetooth for LAN
access
New developments areblurring the distinction
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Bluetooth working group history
February 1998: The Bluetooth SIG is formed promoter company group: Ericsson, IBM, Intel, Nokia,
Toshiba
May 1998: Public announcement of the Bluetooth SIG
July 1999: 1.0A spec (>1,500 pages) is published December 1999: ver. 1.0B is released December 1999: The promoter group increases to 9
3Com, Lucent, Microsoft, Motorola
March 2001: ver. 1.1 is released Aug 2001: There are 2,491+ adopter companies
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Bluetooth: Today and Tomorrow
Will Bluetooth become a household name?
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New Applications
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Synchronization
User benefits Automatic synchronization of
calendars, address books, business cards
Push button synchronization Proximity operation
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Cordless Headset
User benefits Multiple device access Cordless phone benefits Hands free operation
Cordlessheadset
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Usage scenarios examples
Data Access Points Synchronization Headset Conference Table Cordless Computer Business Card Exchange Instant Postcard Computer Speakerphone
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BluetoothTechnical overview and
Protocol
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Bluetooth Specifications
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Single chip with RS-232,USB, or PC card interface
A hardware/software/protocol description An application framework
HC
I
Applications
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Interoperability & Profiles
ProfilesP
roto
cols
Applications
Represents default solution for a usage model
Vertical slice through the protocol stack
Basis for interoperability and logo requirements
Each Bluetooth device supports one or more profiles
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Bluetooth Profiles (in version 1.2 release)
Generic Access (discovery of Bluetooth devices) Service Discovery (establish connection and Discover available services
and connects devices) Cordless Telephone Intercom Serial Port Headset Dial-up Networking Fax LAN Access Generic Object Exchange Object Push File Transfer Synchronization
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Bluetooth Protocol Stack
Composed of protocols to allow Bluetooth devices to locate each other and to create, configure and manage both physical and logical links that allow higher layer protocols and applications to pass data through these transport protocols
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Con
trol
Applications
Transport Protocol Group
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Bluetooth Radio Specification
RF
Baseband
AudioLink Manager
L2CAP
Data Con
trolSDP RFCOMM
IP
Applications Composed of protocols to allow
Bluetooth devices to locate each other and to create, configure and manage both physical and logical links that allow higher layer protocols and applications to pass data through these transport protocols
Radio Frequency (RF) Sending and receiving modulated bit streams
Baseband Defines the timing, framing Flow control on the link.
Link Manager Managing the connection states. Enforcing Fairness among slaves. Power Management
Logical Link Control &Adaptation Protocol Handles multiplexing of higher level protocols Segmentation & reassembly of large packets Device discovery & QoS
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RF - Unlicensed Radio Spectrum
902 Mhz
928 Mhz
26 Mhz 83.5 Mhz 125 Mhz
2.4 Ghz
2.4835 Ghz5.725 Ghz
5.785 Ghz
cordless phonesbaby monitorsWireless LANs
802.11BluetoothMicrowave oven
802.11aHyperLan
33cm 12cm 5cm
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RF - Bluetooth radio link
frequency hopping spread spectrum 2.402 GHz + k MHz, k=0, …, 78 1,600 hops per second
GFSK modulation 1 Mb/s symbol rate
transmit power 0 dbm (up to 20dbm with power control)
. . .
1Mhz
1 2 3 79
83.5 Mhz
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GFSK Differences & Advantages over FSK Modulation Q: What are the physical Differences between an FSK & GFSK
Modulator, and how do their results vary? A1: An FSK Modulator is much the same as a GFSK Modulator,
but GFSK uses a Gaussian filter as well. In a GFSK modulator everything is the same as a FSK modulator except that before the baseband pulses (-1, 1) go into the FSK modulator, it is passed through a gaussian filter to make the pulse smoother so to limit its spectral width
A2: Gaussian filtering is one of the very standard ways for reducing the spectral width, it is called Pulse Shaping. If we use -1 for fc-fd and 1 for fc+fd, once when we jump from -1 to 1 or 1 to -1, the modulated waveform changes rapidly, which introduces large out-of-band spectrum. If we change the pulse going from -1 to 1 as -1, -.98, -.93 ..... .96, .99, 1, and we use this smoother pulse to modulate the carrier, the out-of-band spectrum will be reduced.
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Middleware Protocol Group
Middleware Protocol Group
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Con
trol
Applications
Middleware Protocol Group
Additional transport protocols to allow existing and new applications to operate over Bluetooth. Packet based telephony control signaling protocol also present. Also includes Service Discovery Protocol.
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Middleware Protocol Group (contd.)
Service Discovery Protocol (SDP)Means for applications to discover device info, services and its characteristics.
TCP/IP Network Protocols for packet data communication, routing
RFCOMM(Radio Frequency Communications) Cable replacement protocol, emulation of serial ports over wireless network
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Application Group
Application Group
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Con
trol
Applications
Consists of Bluetooth aware as well as un-aware applications.
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Review FormatAnd Power Mode
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Master - Slave
MasterDevice in Piconet whose clock and hopping sequence are used to synchronize all other devices (slaves) in the Piconet.It also carries out Paging procedure and also Connection Establishment.
Slaves Units within the piconet that are syncronized to the master via its clock and hopping sequence.After connetion establishment, Slaves are assigned a temporary 3 bit member address to reduce the no. of addresing bits required
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Piconets
Point to Point LinkMaster - slave relationshipBluetooth devices can function as masters or slaves
PiconetIt is the network formed by a Master and one or more slaves (max 7).Each piconet is defined by a different hopping channel to which users synchronize to.Each piconet has max capacity (1 Mbps).Hopping pattern is determined by the master.
m s
s s s
m
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Piconet Structure
Master
Active Slave
Parked Slave
Standby
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Physical Link Types
Synchronous Connection Oriented (SCO)Point to Point Full Duplex between Master & SlaveEstablished once by master & kept alive till released by MasterTypically used for Voice connection ( to guarantee continuity )Master reserves slots used for SCO link on the channel to preserve time sensitive information
Asynchronous Connection Link (ACL)It is a momentary link between master and slave.No slots are reserved.It is a Point to Multipoint connection.Symmetric & Asymmetric links possible
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Packet Types
Controlpackets
Data/voicepackets
ID*NullPollFHSDM1
Voice data
HV1HV2HV3DV
DM1DM3DM5
DH1DH3DH5
Access Code
Header
Payload
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Packet Structure
72 bits 54 bits 0 - 2744 bits
DataVoice CRC
No CRCNo retries
header
ARQ
FEC (optional) FEC (optional)
Access Code
Header Payload
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Access Code
PurposeSynchronization DC offset compensation Identification Signaling
TypesChannel Access Code (CAC)
• Identifies a piconet.
Device Access Code (DAC) • Used for signalling procedures like paging and response paging.
Inquiry Access Code (IAC) • General IAC is common to all devices, Dedicated IAC is for a
dedicated group of Bluetooth devices that share a common characteristic.
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Packet Header
Addressing ( 3 bits )
Packet type (4 bits )
Flow Control ( 1 bit )
1-bit ARQ
Sequencing ( 1 bit )
HEC ( 8 bit ) For filtering retransmitted packets
Verify header integrity
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Connection State Machine
Standby
Inquiry Page
Connected
Transmit data
Park Hold Sniff
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Connection State Machine (contd.)
Inquiry ScanA device that wants to be discovered will periodically enter this mode and listen for inquiry packets.
InquiryDevice sends an Inquiry packet addressed to GIAC or DIACTransmission is repeated on the inquiry hop sequence of frequencies.
Inquiry ResponseWhen an inquiry message is received in the inquiry scan state, a response packet (FHS) containing the responding device address must be sent after a random number of slots.
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Connection State Machine (contd.)
Inquiry Response
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Connection State Machine (contd.)
PageThe master uses the clock information, about the slave to be paged, to determine where in the hop sequence, the slave might be listening in the page scan mode. The master sends a page message
Page ScanThe page scan substate can be entered by the slave from the standby state or the connection state. It listens to packets addressed to its DAC.
Page ResponseOn receiving the page message, the slave enters the slave page response substate. It sends back a page response consisting of its ID packet which contains its DAC, at the frequency for the next slot from the one in which page message was received.
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Security
Security MeasuresLimited/Restricted Access to authorized users.Both Link Level Encryption & Authentication.Personal Identification Numbers (PIN) for device access.Long encryption keys are used (128 bit keys).These keys are not transmitted over wireless. Other parameters are transmitted over wireless which in combination with certain information known to the device, can generate the keys.Further encryption can be done at the application layer.
Security valuesDevice Address-PublicAuthentication Key(128 bits)-PrivateEncryption Key(8-128 bits)-PrivateRandom Number
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Frequency Hop Spread-Spectrum
Bluetooth channel is represented by a pseudo random hopping sequence through the entire 79 RF frequencies
Nominal hop rate of 1600 hops per second
Channel Spacing is 1 MHz
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Time-Division Duplex Scheme
Bluetooth devices use a Time-Division Duplex (TDD) scheme Channel is divided into consecutive slots (each 625 s) One packet can be transmitted per slot Subsequent slots are alternatively used for transmitting and
receiving Strict alternation of slots b/t the master and the slaves Master can send packets to a slave only in EVEN slots Slave can send packets to the master only in the ODD slots
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Review of basic concepts
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RF
Baseband
AudioLink Manager
L2CAP
Data Con
trol
Baseband
RFCOMMSDPIP
Applications
RF
Baseband
AudioLink Manager
L2CAP
Data Con
trolSDP RFCOMM
IP
Applications
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Bluetooth Physical link
Point to point link master - slave relationship radios can function as masters or slaves m s
ss
m
s
Piconet Master can connect to 7 slaves Each piconet has max capacity =1 Mbps hopping pattern is determined by the master
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Connection Setup
Inquiry - scan protocol to learn about the clock offset
and device address of other nodes in proximity
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Inquiry on time axis
Slave1
Slave2
Master
Inquiry hoppingsequence
f1 f2
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Piconet formation
Master
Active Slave
Parked Slave
Standby
Page - scan protocol to establish links with
nodes in proximity
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Addressing
Bluetooth device address (BD_ADDR) 48 bit IEEE MAC address
Active Member address (AM_ADDR) (see power mode) 3 bits active slave address all zero broadcast address
Parked Member address (PM_ADDR) (see power mode) 8 bit parked slave address
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Piconet channel
m
s1
s2
625 sec
f1 f2 f3 f4
1600 hops/sec
f5 f6
FH/TDD
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Multi slot packets
m
s1
s2
625 µsec
f1
FH/TDD
Data rate depends on type of packet
f4 f5 f6
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Physical Link Types
m
s1
s2
SCO SCO SCO
Synchronous Connection Oriented (SCO) Link slot reservation at fixed intervals
Asynchronous Connection-less (ACL) Link Polling access method
SCO SCO SCOACL ACL ACLACL ACL ACL
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Packet Types
Controlpackets
Data/voicepackets
ID*NullPollFHSDM1
Voice data
HV1HV2HV3DV
DM1DM3DM5
DH1DH3DH5
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Packet Format
72 bits 54 bits 0 - 2744 bitsAccess code
Header Payload
DataVoice CRC
No CRCNo retries
625 µs
master
slave
header
ARQ
FEC (optional) FEC (optional)
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Access Code
Synchronization DC offset compensation Identification Signaling
Access code
Header Payload
72 bits
Purpose
Channel Access Code (CAC) Device Access Code (DAC) Inquiry Access Code (IAC)
Types
X
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Packet Header
Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8)
Access code
Header Payload
54 bits
Purpose
Encode with 1/3 FEC to get 54 bits
Broadcast packets are not ACKed
For filtering retransmitted packets
18 bitstotal
ss
m
s
16 packet types (some unused)
Max 7 active slaves
Verify header integrity
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Voice Packets (HV1, HV2, HV3)
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Data Packet Types
DM1
DM3
DM5
DH1
DH3
DH5
2/3 FEC
No FEC
Symmetric Asymmetric
108.8 108.8 108.8
258.1 387.2 54.4
286.7 477.8 36.3
Symmetric Asymmetric
172.8 172.8 172.8
390.4 585.6 86.4
433.9 723.2 57.6
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Inter piconet communication
Cell phone Cordlessheadset
Cordless
headset
Cell phone
Cordlessheadset
Cell phone
mouse
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Scatternet
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Scatternet, scenario 2
How to schedule presence in two piconets?
Forwarding delay ?
Missed traffic?
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Baseband: Summary
TDD, frequency hopping physical layer Device inquiry and paging Two types of links: SCO and ACL links Multiple packet types (multiple data rates with
and without FEC)
Baseband Baseband
L2CAPL2CAPLMPLMP
Physical
Data link
Device 2Device 1
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Link Manager Protocol
Setup and management of Baseband connections
• Piconet Management• Link Configuration• Security
LMP
RF
Baseband
AudioLink Manager
L2CAP
Data Con
trolSDP RFCOMM
IP
Applications
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Piconet Management
Attach and detach slaves Master-slave switch Establishing SCO links Handling of low power modes ( Sniff, Hold, Park)
req
response
Paging
Master
Slaves
s
m
s
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Low power mode (hold)
Slave
Hold duration
Hold offset
Master
Hold Mode
By this capacity can be made free to do other things like scanning, Slave temporarily (for Thold sec) does not support ACL packets on the channel (possible SCO links will still be supported).
paging, inquiring, or attending another piconet.
The slave unit keeps its active member address (AM_ADDR)
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Low power mode (Sniff)
Master
Slave
Sniff period
Sniff offset
Sniff duration
Sniff Mode (Traffic reduced to periodic sniff slots)This is a low power mode in which the listening activity of the slave is reduced.
In the sniff mode, the slave listens for transmissions only at fixed intervals Tsniff, at the offset slot Dsniff for Nsniff times. These parameters are given by the
LMP in the master when it issues the SNIFF command to the slave.
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Low power mode (Park)
Master
Slave
Beacon interval
Beacon instant
Park Mode (Power saving + keep more than 7 slaves in a piconet) This is a very low power mode with very little activity. The slave however, stays synchronized to the channel. The parked slaves regularly listen for beacon signals at intervals decided by the
beacon structure communicated to the slave during the start of parking. The parked slave has to be informed about a transmission in a beacon channel
which is supported by the master to keep parked slaves in synchronization and send them any other information.
Any message to be sent to a parked member are sent over the broadcast channel. Communication via broadcast LMP messages.
It also helps the master to have more than seven slaves
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Connection establishment & Security
Goals Authenticated access
Only accept connections from trusted devices
Privacy of communication prevent eavesdropping
Constraints Processing and memory
limitations $10 headsets, joysticks
Cannot rely on PKI Simple user experience
LMP_host_conn_req
LMP Accepted
Security procedure
Paging
Master
Slave
LMP_setup_complete
LMP_setup_complete
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Authentication
Authentication is based on link key (128 bit shared secret between two devices)
How can link keys be distributed securely ?Verifier
Claimant
challenge
response
accepted
Link key Link key
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Pairing (key distribution)
Pairing is a process of establishing a trusted secret channel between two devices (construction of initialization key K init)
Kinit is then used to distribute unit keys or combination keys
Random number
Kinit
PIN + Claimant address
Randomnumber
PIN + Claimantaddress
Randomnumber
Verifier Claimant
Kinit
challenge
response
accepted
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Link Manager Protocol Summary
Piconet management Link configuration
Low power modes QoS Packet type selection
Security: authentication and encryption
Baseband Baseband
L2CAPL2CAPLMPLMP
Physical
Data link
Device 2Device 1
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L2CAP
Logical Link Control andAdaptation Protocol
L2CAP provides• Protocol multiplexing• Segmentation and Re-assembly• Quality of service negotiation
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Applications
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Why baseband isn’t sufficient
Baseband
• Baseband packet size is very small (17min, 339 max) • No protocol-id field in the baseband header
IP RFCOMM IP RFCOMM
reliable*, flow controlled
MultiplexingdemultiplexingMTU
in-sequence, asynchronous link
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IP RFCOMM
Need a multiprotocol encapsulation layer
IP RFCOMM
reliable*, in-order, flow controlled, ACL link
Desired features• Protocol multiplexing• Segmentation and re-assembly• Quality of service
What about• Reliability?• Connection oriented or connectionless?• integrity checks?
unreliable, no integrity
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Segmentation and reassembly
Length Payload
Basebandpackets
start ofL2CAP
continuationof L2CAP
continuationof L2CAP
CRC CRC CRC
• cannot cope with re-ordering or loss• mixing of multiple L2CAP fragments not allowed• If the start of L2CAP packet is not acked, the rest should be discarded
min MTU = 48672 default
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Serial Port Emulation using RFCOMM
Serial Port emulation on top of a packet oriented link• Similar to HDLC• For supporting legacy apps
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Applications
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Serial line emulation over packet based MAC
L2CAP
Design considerations framing: assemble bit stream into
bytes and, subsequently, into packets transport: in-sequence, reliable
delivery of serial stream control signals: RTS, CTS, DTR
RFCOMM
L2CAP
RFCOMM
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GOALS
IP over Bluetooth V 1.0
Internet access using cell phones Connect PDA devices & laptop
computers to the Internet via LAN access points
RF
Baseband
AudioLink Manager
L2CAP
Data
SDP RFCOMM
IP
Applications
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LAN access point profile
SecurityAuthenticationAccess control
Efficiencyheader and data compression
Auto-configurationLower barrier for deployment
Why use PPP?
Access Point
Baseband
L2CAP
RFCOMM
PPP
IP
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Inefficiency of layering
Emulation of RS-232 over the Bluetooth radio link could be eliminated
L2CAP
RFCOMM
rfc 1662
PPP
IP
L2CAP
RFCOMM
rfc 1662
PPP
IP
Palmtop LAN access point
packet oriented
packet oriented
byte oriented
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Terminate PPP at LAN access point
PPP server function at each access point management of user name/password is an issue roaming is not seamless
Bluetooth
RFCOMM
PPP
IP
Bluetooth
RFCOMM
PPP
IP
ethernet
Palmtop Access Point
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L2TP tunneling
Tunneling PPP traffic from access points to the PPP server 1) centralized management of user name/password 2) reduction of processing and state maintenance at each access
point 3) seamless roaming
Bluetooth
RFCOMM
PPP
IP
Palmtop Access Point
Bluetooth
RFCOMM
PPP
IP
ethernet
IP
UDP
ethernet
IP
UDP
PPP server
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Seamless roaming with PPP
AP1
Server
AP2
MAC level registration MAC level handoff
REQ1
RPL2 REQ
3
RPL4
CLR5
palmtopPPP PPP
PPP
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BluetoothCurrent Market
Outlook
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Market Forcasts for year 2005
Units sold annually Revenue Chip price
1.4 bn
$ 5.4 bn
$ 3.6 995 m
$ 4.4 bn
$ 4.4
$ 2.02
$ 4.3 bn
$ 2.2 bn
2.1 bn
1.5 bn
Cahners In-stat (2000 forcast)
revised (2001 forcast)
Merrill Lynch (2000 forcast)
revised (2001 forcast)
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Value to carriers: Synchronization and Push
More bits over the air Utilization of unused capacity
during non-busy periods Higher barrier for switching
service providers
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Value to carriers: Cell phone as an IP gateway
More bits over the air Enhanced user experience
Palmpilot has a better UI than a cell phone
Growth into other vertical markets
Will Pilot and cell phone eventually merge?
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Value to carriers: Call handoff
More attractive calling plans Alleviate system load during peak periods Serve more users with fewer resources
Threat or opportunity?
Cordless base
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Biggest challenges facing Bluetooth
Interoperability Always a challenge for any new technology
Hyped up expectations Out of the box ease of use Cost target $5 Critical mass RF in silicon Conflicting interests – business and engineering
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References
[1] IEEE 802.11, “Wireless LAN MAC and Physical Layer Specification,” June 1997.
[2] Hirt, W.; Hassner, M.; Heise, N. “IrDA–VFIr (16 Mb/s): modulation code and system design.” IEEE Personal Communications, vol.8, (no.1), IEEE, Feb. 2001.
[3] Lansford, J.; Bahl, P. “The design and implementation of HomeRF: a radio frequency wireless networking standard for the connected home.” Proceedings of the IEEE, IEEE, Oct. 2000.
[4] Specification of Bluetooth System, ver. 1.0, July 1999
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References (cnt)
[5] Haartsen, J.C. “The Bluetooth radio system.”, IEEE Personal Communications, IEEE, Feb. 2000.
[6] Haartsen, J.C. ‘Bluetooth towards ubiquitous wireless connectivity.’, Revue HF, Soc. Belge Ing. Telecommun. & Electron, 2000. p.8–16.
[7] Rathi, S. “Bluetooth protocol architecture.” Dedicated Systems Magazine, Dedicated Systems Experts, Oct.–Dec. 2000.
[8] Haartsen, J.C.; Mattisson, S. “Bluetooth–a new low–power radio interface providing short–range connectivity.” Proceedings of the IEEE, IEEE, Oct. 2000.
[9] Gilb, J.P.K “Bluetooth radio architectures.” 2000 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium Digest of Papers, Boston, MA, USA, 11–13 June 2000.
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References (cnt)
[10] N. Benvenuto, G. Cherubini, “Algoritmi e circuiti per le telecomunicazioni”, Ed. Libreria Progetto.
[11] The Bluetooth Special Interest Group, Documentation available at http://www.bluetooth.com/
[12] IEEE 802.15 Working Group for WPANs™; http://www.manta.ieee.org/groups/802/15/
[13] Barker, P.; Boucouvalas, A.C.; Vitsas, V. “Performance modelling of the IrDA infrared wireless communications protocol.” International Journal of Communication Systems, vol.13, Wiley, Nov.–Dec. 2000.
[14] Tokarz, K.; Zielinski, B. “Performance evaluation of IrDA wireless transmission.” 7th Conference on Computer Networks, Zakopane, Poland, 14–16 June 2000.
[15] ETSI RES, “Digital European Cordless Telecommunications (DECT), Common interface Part 1: Overview,” ETS 300 175–1, 1996.
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Synchronization using a Beacon (infrastructure)
beacon interval
tmedium
accesspoint
busy
B
busy busy busy
B B B
value of the timestamp B beacon frame
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Synchronization using a Beacon (ad-hoc)
tmedium
station1
busy
B1
beacon interval
busy busy busy
B1
value of the timestamp B beacon frame
station2
B2 B2
random delay