Bluetooth - Comprehensive Presentation

Who is Bluetooth ? ? ?
• HARALD BLUETOOTH
• King of Denmark (940 – 981)
• Unified Danish tribes into a single kingdom
3

By Ericsson in Sweden (1999)
4

History
~Invented in 1994 by Ericsson.
~The company later started working with a larger
group of companies called the Bluetooth Special
Interest Group or “SIG”, to develop the technology
into what it is today.
~Bluetooth is not owned by any one company and is
developed and maintained by SIG.
5

History
The Bluetooth Special Interest Group (SIG) was founded by
• Ericsson,
• IBM,
• Intel,
• Nokia and
• Toshiba
in February 1998 to develop as open specification for
short-range wireless connectivity.
6

Features
• Cable-replacement technology
• Wireless technology for short-range voice and data
communication
• Low-cost and low-power
• Provides a communication platform between a wide
range of “smart” devices
• Not limited to “line of sight” communication 7

. . .
• Universal radio interface for ad-hoc wireless connectivity
• Interconnecting computer and peripherals, handheld
devices, PDAs, cell phones – replacement of IrDA
• Embedded in other devices, goal: 5€/device (2002:
50€/USB bluetooth)
• Short range (10 m), low power consumption, license-free
2.45 GHz ISM
• Voice and data transmission, approx. 1 Mbit/s gross data
rate
8

Technically,
it is a chip to be plugged into computers, printers, mobile
phones, etc.
Designed by taking the information normally carried by the
cable,
transmitting it at a special frequency to a receiver
Bluetooth chip
which will then give information received to these mobile
devices. 9

It comprises of a
base band processor, a radio and an antenna.
The base-band processor converts the data into signals,
the antenna of another blue tooth device, within at least 30
feet distance, receives a transmitted signal in the air.
. . .
10

Bluetooth in Action
Source: http//:www.motorola.com
In the OfficeIn the house
11

Home Security On the Road
12

On your Car
13

Types of Bluetooth Devices
1. Head Set
2. In-Car Bluetooth System
3. Bluetooth Equipped Printer
4. Bluetooth Equipped Web Cam
5. Bluetooth GPS System
6. Bluetooth Key Board 14

Pros
• These have Replaced cables for transferring Information
from one Electronic Device to another one.
• These have decreased Strain like carrying phones while
talking, making hands free to do another work.
• This is cheaply Available.
• It’s Mobility is also very Important as it doesn’t need any
power outlet or Internet connection or any other items.
15

Cons
 Data sent between two Bluetooth devices is very slow
compared with Wi-Fi transfer Rate.
 Range Of a Bluetooth Device is 15-30 feet depending
upon the Device.
 Security is Biggest Disadvantage as transfer takes place
through radio waves and a hacker can easily hack it.
16

Characteristics
1. 2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier
spacing
• Channel 0: 2402 MHz … channel 78: 2480 MHz
• G-FSK modulation, 1-100 mW transmit power
2. FHSS and TDD
• Frequency hopping with 1600 hops/s
• Hopping sequence in a pseudo random fashion, determined by a
master
• Time division duplex for send/receive separation
17

FHSS
• Bluetooth devices use a protocol called (FHHS) Frequency-
Hopping Spread Spectrum .
• Uses packet-switching to send data.
• Bluetooth sends packets of data on a range of frequencies.
• In each session one device is a master and the others are
slaves.
• The master device decides at which frequency data will
travel.
18

. . .
• Transceivers “hop” among 79 different frequencies in the 2.4
GHz baud at a rate of 1600 frequency hops per second.
• The master device tells the slaves at what frequency data will
be sent.
• This technique allows devices to communicate with each other
more securely.
19

Characteristics (Contd.)
3. Voice link – SCO (Synchronous Connection Oriented)
• FEC (forward error correction), no retransmission, 64 kbit/s
duplex, point-to-point, circuit switched
4. Data link – ACL (Asynchronous ConnectionLess)
• Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9
kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet
switched
5. Topology
• Overlapping piconets (stars) forming a scatternet
20

Piconet
M=Master
S=Slave
P=Parked
SB=Standby
M
P
S
22
SB SB
SB
SB
P
P S
S
P

. . .
• A Piconet session is a communication link that must be created
between devices for devices to communicate with each other.
• If two devices come onto contact with each other( 32 feet) the
user will be prompted to initiate a communication session
• Users then can either deny or accept the request to initiate a
session
• Only devices approved by the user can take part in the session
• Data will appear as noise to unauthorized devices (A great
security feature). 23

. . .
• Collection of devices connected in an ad hoc fashion
• One unit acts as master and the others as slaves for the lifetime of the
piconet
• Master determines hopping pattern, slaves have to synchronize
• Each piconet has a unique hopping pattern
• Participation in a piconet = synchronization to hopping sequence
• P device-cannot actively participate , are known and can be reactivated
within some milliseconds
• SB device-do not participate in piconent
• Each piconet has one master and up to 7 simultaneous slaves
• > 200 devices could be parked
24

. . .
• All devices in a piconet hop together
• Master sends its clock and device ID to slaves
• Hopping pattern is determined by device ID (48 bit, unique id)
• Phase in hopping pattern is determined by master’s clock
• Addressing
• Active Member Address (AMA, 3 bit) for active devices
• Parked Member Address (PMA, 8 bit) for parked devices
• SB devices do not need an address
SB
SB
SB
SB
SB
SB
SB
SB
SB
M
S
P
SB
S
S
P
P
SB
















25

Scatternet
• Linking of multiple co-located piconets through the sharing of common
master or slave devices
• Devices can be slave in one piconet and master of another
• Communication between piconets
• Devices jumping back and forth between the piconets
M
S
P
SB
S
S
P
P
SB
M
S
S
P
SB 26

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
Logical Link Control and Adaptation Protocol (L2CAP)Audio
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
RFCOMM (serial line interface)
AT modem
commands
telephony apps.audio apps. mgmnt. apps.
AT: attention sequence
OBEX: object exchange
TCS BIN: telephony control protocol specification – binary
BNEP: Bluetooth network encapsulation protocol
SDP: service discovery protocol
RFCOMM: radio frequency comm.
PPP
28

. . .
Bluetooth Protocol stack is divided into two
parts:
Core specification
Profile specification
29

Core Protocol
Radio: Specification of the air interface, ie frequency,
modulation and transmit power.
Base band: Describes basic connection establishment, packet
format, timing, basic QoS parameters.
Link manager protocol: link setup and management b/w
devices including security functions and parameter negotiation
Logical link control and adaptation protocol (L2CAP):adapt
higher layers to the base band.
Service discovery protocol: Device discovery in close proximity
30

. . .
 Profile specification:
 describes protocols and functions needed to adapt
the wireless Bluetooth technology to legacy and new
applications
 Above L2CAP is the cable replacement protocol
RFCOMM that emulates a serial line interface.
This allows a simple replacement of serial line cables and enables
many applications and protocols to run over bluetooth
 Supports multiple serial ports over a single physical channel 31

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS
BIN
SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
TCS-BIN(telephony control protocol – binary)
Bit oriented protocol
defines call control signaling for establishment of voice and data
calls b/w bluetooth devices
Describes mobility and group management functions
PPP
32

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
PPP
33
 Host controller interface (HCI) b/w baseband and L2CAP provides
 command interface to baseband controller and link manager.
 Access to the hardware status and control registers.
 Can be seen as the hardware and software boundary.

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
PPP
34
 Classical internet appln can use the TCP/IP stack running over Point to
Point Protocol (PPP)or use the Bluetooth network encapsulation
protocol(BNEP)

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
AT: attention sequence
Telephony applns can use AT modem commands as if using a standard modem.
PPP
35

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
 Calendar or business card objects (vCal/vCard)
 can be exchanged using object exchange protocol(OBEX).
PPP
36

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
 Provide support for audio
 Audio applications may directly use the baseband layer after
encoding the audio signals
PPP
37
OBEX
vCal/vCard

Core Protocol
Radio
Base band
Link manager protocol
Logical link control and adaptation protocol (L2CAP)
Service discovery protocol
38

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
PPP
39
Radio layer

Defines carrier frequencies and output power
Design Limitations
Bluetooth devices will be integrated into mobile devices and
thus rely on battery power.
Requires small low power chips that can be built into
handheld devices
Frequency must be available worldwide
Bluetooth has to support multimedia data
40
. . .

FEATURES
Uses license free 2.4 GHz frequency band for world wide
operation
Bluetooth uses frequency hopping/time division duplex
scheme for transmission
Hopping rate= 1600 hops/s
Time b/w 2 hops is called a slot (625 microseconds)
Each slot uses a different frequency
Bluetooth uses 79 hop carriers equally spaces at 1MHz
41
. . .

Bluetooth transceivers are available in three classes:
Power class1:
max power 100mW and minimum power 1 mW ,
100m range without obstacles
Power control is mandatory.
Power class2:
max power 2.5mW, normal power is 1mW and min power is
0.25mW,
10m range.
 Power control is optional.
Power class3: maximum power is 1mW.
42
. . .

Core Protocol
 Radio
• BASE BAND
• Link manager protocol
• Logical link control and adaptation protocol (L2CAP)
• Service discovery protocol
43

Radio
Baseband
Link Manager
Control
Host
Controller
Interface
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
AT modem
commands
PPP
44
Baseband layer

Baseband layer
Performs frequency hopping
Defines physical links and packet formats
In a piconet each device hops to the same frequency
at the same time.
45

Frequency selection during data transmission
(1 slot packets)
• Within each slot the master or any of the slaves may
transmit data in an alternating fashion
• Each data transmission uses one 625 µs slot.
46
S
fk
625 µs
fk+1 fk+2 fk+3 fk+4 fk+5 fk+6
MM M M
t
S S

. . .
Defines 3-slot or 5-slot packets for higher data rate.
If a master or slave sends a packet covering 3 or 5 slots
Here radio transmitter remains in the same frequency until
the packet is transmitted.
No frequency hopping is performed within a packet
After transmission the radio returns to the frequency
required by the hopping pattern.(handle hidden terminal
problem).
Shifting phase even in one device would destroy the
piconet
47

Frequency selection during data transmission
(3,5 slot packets)
fk+3 fk+4fk
fk
fk+5
fk+1 fk+6
fk+6
M
M M
M M
t
t
S S
S
48

Baseband packet format
access code packet header payload
68(72) 54 0-2745 bits
AM address type flow ARQN SEQN HEC
3 4 1 1 1 8 bits
preamble sync. (trailer)
4 64 (4)
49

Access Code
50
• For timing synchronization and piconet identification
• Consists of preamble, synchronization field and trailer
• 64 bit sync is determined from the lower 24 bits of an
address(LAP- lower address part)
access code
68(72)
preamble sync. (trailer)
4 64 (4)

Packet Header
• Packet header
• Features: address, packet type, flow and error control and checksum
• 3-bit active member address : temporarily assigned address to slave.
• Zero values are reserved for broadcast.
• 4-bit type field : determines type of packet : control, asynchronous
,synchronous data.
• 1-bit flow field: flow control mechanism for asynchronous traffic.
• Flow=0-transmission stop
• Flow=1- transmission resume
• SEQN(seq no.) and ARQN (ARQ seq.no) are used for acknowledgement
• 8 bit HEC(Header Error Check):protect packet header
packet header
54
AM address type flow ARQN SEQN HEC
3 4 1 1 1 8 bits
51

Payload
• Upto 343 bytes payload can be transferred
• Structure of the payload field depends on the type of link
52

Physical Links
• Bluetooth offers 2 types of links :
1. Synchronous connection oriented link (SCO)
2. Asynchronous connectionless link(ACL)
53

Synchronous connection oriented link
(SCO)
– Voice connections require symmetrical, circuit switched, point to point
connection.
– Two time slots (forward and return slot) are reserved at fixed intervals
for transmission
– Master supports upto three simultaneous SCO links to the same or
different slaves.
– Slaves support upto two links from different masters or upto three links
from the same master
– SCO carry voice at 64 kbits/s without FEC, with 2/3 FEC or 1/3 FEC
(Forward Error Correction)
54

SCO payload types
payload (30)
audio (30)
audio (10)
audio (10)
HV3
HV2
HV1
DV
FEC (20)
audio (20) FEC (10)
header (1) payload (0-9) 2/3 FEC CRC (2)
(bytes)
55

Asynchronous connectionless link
(ACL)
Data appln require symmetric or asymmetric, packet switched, point
to multipoint transfer scenarios
• Master uses a polling scheme
• Slave may answer only if addressed by the master in the
preceding slot
• Only one ACL link exists b/w master and a slave
• Can carry 1-slot,3-slot or 5-slot packets.
• Data can be protected using 2/3 FEC scheme(helps in noisy
environments with a high link error rate)
• high overhead ,so a fast ARQ scheme is used for reliable
transmission
• Payload is CRC protected except for AUX1 packet 56

ACL Payload types
payload (0-343)
header (1/2) payload (0-339) CRC (2)
header (1) payload (0-17) 2/3 FEC
header (1) payload (0-27)
header (2) payload (0-183)
header (2) payload (0-339)DH5
DM5
DH3
DM3
DH1
DM1
header (1) payload (0-29)AUX1
CRC (2)
CRC (2)
CRC (2)
CRC (2)
CRC (2)
CRC (2)
(bytes)
57

….
• Control packets are available for
• polling slaves
• hopping synchronization
• acknowledgement
• DM1 (data medium rate)& DH1(data high rate) use single slot and 1 byte header
• DM3 & DH3 use three slots
• DM5 & DH5 use five slots
• Medium rates are always FEC protected
• High rates rely on CRC only for error detection
• HV (High Quality Voice) packets use single slot
• DV (Data & Voice)- combined packet where CRC,FEC and payload header are
valid for the data part only
58

Example Data Transmission
59
•One master and two slaves
•Master always uses even frequency slots
•Slaves uses odd slots
•Every 6th slot is used for SCO link b/w M and S
•ACL link uses single or multiple slots

Core Protocol
 Radio
 Base band
• LINK MANAGER PROTOCOL
• Logical link control and adaptation protocol (L2CAP)
60

Link Manager protocol
Manages
various aspects of radio link between a master and slave
current parameter setting of the devices
Enhances baseband functionality but higher layers can still
directly access the baseband
61

Functions of LMP
1. AUTHENTICATION, PAIRING & ENCRYPTION
 basic authentication in baseband
 control the exchange of random numbers and signed responses
 pairing service -to establish an initial trust relationship b/w two
devices that have never communicated before. The result of
pairing is a link key
 not directly involved in the encryption process, but sets the
encryption mode ,key size, and random speed
62

…
2. SYNCHRONIZATION
Precise synchronization is important
Clock offset is updated each time a packet is received from the master
Special synchronization packets can be received
Devices can also exchange timing information related to the time differences
(slot boundaries) between two adjacent piconets
3. CAPABILITY NEGOTIATION
Version of LMP , information about the supported features can be exchanged
devices have to agree the usage of, e.g., multi-slot packets, encryption, SCO
links, voice encoding, park/sniff/hold mode etc.
63

….
4. QUALITY OF SERVICE NEGOTIATION
 poll interval- maximum time between transmissions from a master to a
particular slave, controls the latency and transfer capacity
 quality of the channel – DM or DH
 Number of repetitions for broadcast packets can be controlled
 master can limit the number of slots available for slave’s answers to increase its
own bandwidth
5. POWER CONTROL
 Device can measure the received signal strength
 Depending on this signal level, device can direct the sender of the measured
signal to increase or decrease its transmit power.
64

…
6. LINK SUPERVISION
Control the activity of a link
set up new SCO links or
 may declare the failure of a link
7. STATE AND TRANSMISSION MODE EXCHANGE
Devices might switch the master/slave role,
detach themselves from a connection or
change the operating mode
65

Baseband states of a Bluetooth
device
66
STANDBY MODE
• Every device which
is currently not
participating in a
piconet
• & is not switched
off.
• Low power mode

device
67
Step towards inquiry
mode can be in 2
ways:
Either a device
want to establish a
piconet
Or a device wants
to just listen

device
68
PAGE
• After finding all the
required devices,
master sets up a
piconet
• Depending on
device addresses,
special hopping
sequence is
calculated.
• Slaves answer and
synchronize

device
69
CONNECTION STATE
• Has Active state &
Low Power state
• In Active state –
Slave participates
in the piconet by
listening,
transmitting, and
receiving
• devices can either
transmit data or
are simply
connected.

…
• To save battery power, a Bluetooth device can go into one
of three low power states:
1.Sniff :highest power consumption, listen periodically
2.Hold: stop ACL transmission, SCO still possible by slave,
possibly participate in another piconet
3.Park: lowest duty cycle ,lowest power
consumption,release AMA(Active Member Address), get
PMA(Parked Member Address )
70

Core Protocol
 Radio
 Base band
 Link Manager Protocol
• LOGICAL LINK CONTROL AND ADAPTATION PROTOCOL
(L2CAP)
71

L2CAP-LogicalLinkControl and Adaptation
Protocol
Simple data link control protocol on top of baseband
that offer logical channels b/w Bluetooth devices.
L2CAP is available for ACLs only
Types of logical channels include
– Connection oriented, connectionless and signaling channels
72

. . .
Connectionless: unidirectional channels for broadcast from master to slaves
Connection oriented: bidirectional channels and supports QoS specifications in
each direction.
Signaling: used to exchange signaling messages.
Channel identifier (CID): Channels are identified using CID
– CID=1 for signaling channel.
– CID=2 for connectionless channels.
– CID>=64 for connection oriented channels.(64-65535). 73

L2CAP logical channels
baseband
L2CAP
baseband
L2CAP
baseband
L2CAP
Slave SlaveMaster
ACL
2 d 1 d d 1 1 d 21
signalling connectionless connection-oriented
d d d
74

L2CAP packet formats
length
2 bytes
CID=2
2
PSM
2
payload
0-65533
length
2 bytes
CID
2
payload
0-65535
length
2 bytes
CID=1
2
One or more commands
Connectionless PDU
Connection-oriented PDU
Signalling command PDU
code ID length data
1 1 2 0
Length : Length of payload
75

length
2 bytes
CID=2
2
PSM
2
payload
0-65533
length
2 bytes
CID
2
payload
0-65535
length
2 bytes
CID=1
2
Connectionless PDU
code ID length data
1 1 2 0
PSM : Protocol/Service multiplexer : to identify the higher layer recipient for the payload
76

length
2 bytes
CID=2
2
PSM
2
payload
0-65533
length
2 bytes
CID
2
payload
0-65535
length
2 bytes
CID=1
2
Connectionless PDU
code ID length data
1 1 2 0
code : for command reject, connection request, disconnection response etc.
ID : To match request with reply
Length : length of data
77

Security Components & Protocols
E3
E2
link key (128 bit)
encryption key (128 bit)
payload key
Keystream generator
Data Data
Cipher data
Authentication key generation
(possibly permanent storage)
Encryption key generation
(temporary storage)
PIN (1-16 byte)
User input (initialization)
Pairing
Authentication
Encryption
Ciphering
E3
E2
link key (128 bit)
encryption key (128 bit)
payload key
Keystream generator
PIN (1-16 byte)
78

Core Protocol
 Radio
 Base band
 Link Manager Protocol
 Logical link control and adaptation protocol (L2CAP)
• SERVICE DISCOVERY PROTOCOL
79

SDP – Service Discovery Protocol
• To know what devices or specifically what services are
available in radio proximity
• SDP defines only the discovery of services not their usage.
• Discovered services can be cached and gradual discovery is
possibly.
• Inquiry/response protocol for discovering services
– Searching for and browsing services in radio proximity
– Adapted to the highly dynamic environment
– Can be complemented by others like SLP, Jini, Salutation, …
– Defines discovery only, not the usage of services
– Caching of discovered services
– Gradual discovery 80

SDP – Service Discovery Protocol
• Service record format : all the info. about a service
– Information about services provided by attributes
– list of service attributes
– Attributes are composed of an 16 bit ID (name) and a value
– values may be derived from 128 bit Universally Unique Identifiers
(UUID)
– protocol descriptor list comprises the protocols needed to access this
service
– example service record : URLs for service documentation,
an icon for the service
service name
81

Profiles
• To provide compatibility among the devices offering the
same services, Bluetooth specified many profiles in
addition to the core protocols.
• Without profiles, interoperation between devices from
different manufacturers impossible
• Represent default solutions for a certain usage model
– Vertical slice through the protocol stack
– Basis for interoperability
Profiles
Protocols
Applications
82

Profiles
BASIC PROFILES
• Generic Access Profile
• Service Discovery Application Profile
• Cordless Telephony Profile
• Intercom Profile
• Serial Port Profile
• Headset Profile
• Dial-up Networking Profile
• Fax Profile
• LAN Access Profile
• Generic Object Exchange Profile
• Object Push Profile
• File Transfer Profile
• Synchronization Profile
Profiles
Protocols
Applications
83

Profiles
ADDITIONAL PROFILES
• Advanced Audio Distribution
• PAN
• Audio Video Remote Control
• Basic Printing
• Basic Imaging
• Extended Service Discovery
• Generic Audio Video Distribution
• Hands Free
• Hardcopy Cable Replacement
Profiles
Protocols
Applications
84

Bluetooth - Comprehensive Presentation

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