Bluetooth:%20%20%201.Applications,%20Technology

1
Bluetooth 1.Applications, Technology

• And Performance

2
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
3
802.11

• Replacement for Ethernet
• Supported data rates
• 11, 5.5, 2, 1 Mbps and recently up to 20Mbps _at_
  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

4
Emerging Landscape
Bluetooth
802.11
Cordless headset
LAN AP

• Which option is technically superior ?
• What market forces are at play ?
• What can be said about the future ?

5
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 (gt1,500 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

6
Bluetooth Today and Tomorrow

• Will Bluetooth become a household name?

7
New Applications
8
Synchronization

• User benefits
• Automatic synchronization of calendars, address
  books, business cards
• Push button synchronization
• Proximity operation

9
Cordless Headset
Cordless headset

• User benefits
• Multiple device access
• Cordless phone benefits
• Hands free operation

10
Usage scenarios examples

• Data Access Points
• Synchronization
• Headset
• Conference Table
• Cordless Computer
• Business Card Exchange
• Instant Postcard
• Computer Speakerphone

11
BluetoothTechnical overview and Protocol
12
Bluetooth Specifications
Applications
SDP
RFCOMM
Audio
L2CAP
Link Manager
Baseband
RF

• A hardware/software/protocol description
• An application framework

13
Interoperability Profiles

• 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

14
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

15
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

Applications
SDP
RFCOMM
Audio
L2CAP
Link Manager
Baseband

Transport Protocol Group
RF
16
Bluetooth Radio Specification

• 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

17
RF - Design considerations
Noise, interference
power
spectrum
Recovered data signal
Data signal x(t)
cost
Goal

• high bandwidth
• conserve battery power
• cost lt 10

18
RF - EM Spectrum
S/W radio
FM radio
TV
TV
AM radio
cellular
?
X rays
Gamma rays
visible
UV
infrared
?
1 MHz
1 kHz
1 GHz
1 THz
1 PHz
1 EHz
Propagation characteristics are different in each
frequency band
19
RF - Unlicensed Radio Spectrum
?
12cm
5cm
33cm
26 Mhz
83.5 Mhz
125 Mhz
902 Mhz
2.4 Ghz
5.725 Ghz
2.4835 Ghz
5.785 Ghz
928 Mhz
802.11 Bluetooth Microwave oven
802.11a HyperLan
cordless phones baby monitors Wireless LANs
20
RF - Bluetooth radio link
1Mhz
. . .
79
1
2
3
83.5 Mhz

• frequency hopping spread spectrum
• 2.402 GHz k MHz, k0, , 78
• 1,600 hops per second
• GFSK modulation
• 1 Mb/s symbol rate
• transmit power
• 0 dbm (up to 20dbm with power control)

21
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 fcfd, 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.

22
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.
Applications
SDP
RFCOMM
Middleware Protocol Group
Middleware Protocol Group
Audio
L2CAP
Link Manager
Baseband
RF
23
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

24
Application Group
Applications
Application Group
SDP
RFCOMM
Consists of Bluetooth aware as well as un-aware
applications.
Audio
L2CAP
Link Manager
Baseband
RF
25
Review Format And Power Mode
26
Master - Slave

• Master
• Device 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

27
Piconets

• Point to Point Link
• Master - slave relationship
• Bluetooth devices can function as masters or
  slaves
• Piconet
• It 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
28
Piconet Structure
29
Physical Link Types

• Synchronous Connection Oriented (SCO)
• Point to Point Full Duplex between Master Slave
• Established once by master kept alive till
  released by Master
• Typically 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

30
Packet Types
Data/voice packets
Control packets
Voice
data
ID Null Poll FHS DM1
HV1 HV2 HV3 DV
DH1 DH3 DH5
DM1 DM3 DM5
Access Code
Header
Payload
31
Packet Structure
54 bits
0 - 2744 bits
72 bits
Access Code
Header
Payload
Data
header
Voice
CRC
No CRC No retries
ARQ

FEC (optional)
FEC (optional)
32
Access Code

• Purpose
• Synchronization
• DC offset compensation
• Identification
• Signaling
• Types
• Channel 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.

33
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
34
Connection State Machine
Inquiry
Page
Standby
Connected
Transmit data
Park
Hold
Sniff
35
Connection State Machine (contd.)

• Inquiry Scan
• A device that wants to be discovered will
  periodically enter this mode and listen for
  inquiry packets.
• Inquiry
• Device sends an Inquiry packet addressed to GIAC
  or DIAC
• Transmission is repeated on the inquiry hop
  sequence of frequencies.
• Inquiry Response
• When 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.

36
Connection State Machine (contd.)

• Inquiry Response

37
Connection State Machine (contd.)

• Page
• The 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 Scan
• The 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 Response
• On 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.

38
Security

• Security Measures
• Limited/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 values
• Device Address-Public
• Authentication Key(128 bits)-Private
• Encryption Key(8-128 bits)-Private
• Random Number

39
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

40
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

41
Review of basic concepts
42
Baseband
Applications
SDP
RFCOMM
Audio
L2CAP
Link Manager
Baseband
RF
43
Bluetooth Physical link

• Point to point link
• master - slave relationship
• radios can function as masters or slaves

44
Connection Setup

• Inquiry - scan protocol
• to learn about the clock offset and device
  address of other nodes in proximity

45
Inquiry on time axis
f1
f2
Slave1
Master
Slave2
46
Piconet formation

• Page - scan protocol
• to establish links with nodes in proximity

47
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

48
Piconet channel
FH/TDD
f1
f3
f4
f5
f2
f6
m
s1
s2
625 ?sec
1600 hops/sec
49
Multi slot packets
FH/TDD
f1
f4
f5
f6
m
s1
s2
625 µsec
Data rate depends on type of packet
50
Physical Link Types

• Synchronous Connection Oriented (SCO) Link
• slot reservation at fixed intervals

• Asynchronous Connection-less (ACL) Link
• Polling access method

m
s1
s2
51
Packet Types
Data/voice packets
Control packets
Voice
data
ID Null Poll FHS DM1
HV1 HV2 HV3 DV
DH1 DH3 DH5
DM1 DM3 DM5
52
Packet Format
54 bits
72 bits
0 - 2744 bits
Access code
Header
Payload
header
Data
Voice
CRC
No CRC No retries
ARQ
FEC (optional)
FEC (optional)
625 µs
master
slave
53
Access Code
72 bits
Access code
Payload
Header
Purpose

• Synchronization
• DC offset compensation
• Identification
• Signaling

X
54
Packet Header
54 bits
Access code
Payload
Header
Purpose

• Addressing (3)
• Packet type (4)
• Flow control (1)
• 1-bit ARQ (1)
• Sequencing (1)
• HEC (8)

16 packet types (some unused)
Broadcast packets are not ACKed
For filtering retransmitted packets
Verify header integrity
total
18 bits
Encode with 1/3 FEC to get 54 bits
55
Voice Packets (HV1, HV2, HV3)
240 bits
54 bits
72 bits
366 bits
Access code
Header
30 bytes
Payload
HV1
10 bytes
1/3 FEC
20 bytes
HV2
2/3 FEC
30 bytes
HV3
56
Voice Packets (HV1, HV2, HV3)
57
Data rate calculation DM1 and DH1
72 bits
54 bits
240 bits
366 bits
Access code
30 bytes
Header
Dir Size Freq Rate
? 17 1600/2 108.8
? 17 108.8

? 27 172.8
? 27 172.8
Payload
625 µs
1
2
58
Data rate calculation DM3 and DH3
72 bits
54 bits
1626 bits
1500 bits
Access code
187 bytes
Header
Dir Size Freq Rate
? 121 1600/4 387.2
? 17 54.4

? 183 585.6
? 27 86.4
Payload
1875 µs
1
2
3
4
59
Data rate calculation DM5 and DH5
72 bits
54 bits
2870 bits
2744 bits
Access Code
343 bytes
Header
Dir Size Freq Rate
? 224 1600/6 477.8
? 17 36.3

? 339 723.2
? 27 57.6
Payload
625 µs
3125 µs
1
2
3
4
5
6
60
Data Packet Types
Asymmetric
Symmetric
108.8 108.8 108.8
258.1 387.2 54.4
286.7 477.8 36.3
2/3 FEC
Asymmetric
Symmetric
172.8 172.8 172.8
390.4 585.6 86.4
433.9 723.2 57.6
No FEC
61
Inter piconet communication
Cordless headset
Cell phone
Cell phone
Cordless headset
62
Scatternet
63
Scatternet, scenario 2
How to schedule presence in two piconets?
Forwarding delay ?
Missed traffic?
64
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)

65
Link Manager Protocol

• Setup and management
• of Baseband connections
• Piconet Management
• Link Configuration
• Security

66
Piconet Management

• Attach and detach slaves
• Master-slave switch
• Establishing SCO links
• Handling of low power modes ( Sniff, Hold, Park)

Paging
req
Master
Slave
response
67
Low power mode (hold)
Hold offset
Slave
Hold duration
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)

68
Low power mode (Sniff)
Sniff offset
Sniff duration
Slave
Sniff period
Master

• 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.

69
Low power mode (Park)
Slave
Beacon instant
Beacon interval
Master

• 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

70
Connection establishment Security

• Goals
• Authenticated access
• Only accept connections from trusted devices
• Privacy of communication
• prevent eavesdropping

Paging
LMP_host_conn_req

• Constraints
• Processing and memory limitations
• 10 headsets, joysticks
• Cannot rely on PKI
• Simple user experience

LMP Accepted
Security procedure
Master
Slave
LMP_setup_complete
LMP_setup_complete
71
Authentication

• Authentication is based on link key (128 bit
  shared secret between two devices)
• How can link keys be distributed securely ?

challenge
response
Claimant
Verifier
accepted
Link key
Link key
72
Pairing (key distribution)

• Pairing is a process of establishing a trusted
  secret channel between two devices (construction
  of initialization key Kinit)
• Kinit is then used to distribute unit keys or
  combination keys

PIN Claimant address
PIN Claimant address
Claimant
Verifier
Random number
challenge
Random number
Random number
response
accepted
Kinit
Kinit
73
Link Manager Protocol Summary

• Piconet management
• Link configuration
• Low power modes
• QoS
• Packet type selection
• Security authentication and encryption

74
L2CAP
Logical Link Control and Adaptation Protocol
Applications
SDP
RFCOMM
Data

• L2CAP provides
• Protocol multiplexing
• Segmentation and Re-assembly
• Quality of service negotiation

Audio
L2CAP
Link Manager
Baseband
RF
75
Why baseband isnt sufficient
reliable, flow controlled
Baseband
in-sequence, asynchronous link

• Baseband packet size is very small (17min, 339
  max)
• No protocol-id field in the baseband header

76
Need a multiprotocol encapsulation layer
IP
RFCOMM
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?

77
Segmentation and reassembly
Payload
Length
Baseband packets
CRC
CRC
CRC
start of L2CAP
continuation of L2CAP
continuation of L2CAP

• 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 48 672 default
78
Multiplexing and Demultiplexing
IP
RFCOMM
IP
RFCOMM
Circuit or connection-less ?
Why is L2CAP connection oriented ?

• Baseband is polling based
• Bandwidth efficiency
• - carry state in each packet Vs. maintain it at
  end-points
• Need ability for logical link configuration
• MTU
• reliability (Flush timeout option)
• QoS (token bucket parameter negotiation)

79
L2CAP Channels
CID
Payload
Length
signaling channel
master
Slave 1
Slave 3
01
01
01
01
CID
CID
CID
CID
CID
CID
data channel
CID
01
Signaling channel CID does not uniquely
determine the identity of the source L2CAP entity
Signaling channel for 1) connection
establishment 2) channel configuration 3)
disconnection
CID
01
Slave 2
80
L2CAP connection an example
Target
Initiator
L2CAP_ConnectReq
Establishment
L2CAP_ConnectRsp
L2CAP_ConfigReq
Configuration
L2CAP_ConfigRsp
MTU, QoS reliability
L2CAP_ConfigReq
L2CAP_ConfigRsp
Data transfer
L2CAP_DisconnectReq
Termination
L2CAP_DisconnectRsp
81
L2CAP Packet Format (Connectionless)
Not fully developed yet.
82
L2CAP Summary
Design constraints

• Simplicity
• Low overhead
• Limited computation and memory
• Power efficient

Assumptions about the lower layer

• Reliable, in-order delivery of fragments
• Integrity checks on each fragment
• Asynchronous, best effort point-to-point link
• No duplication
• Full duplex

Service provided to the higher layer

• Protocol multiplexing and demultiplexing
• Larger MTU than baseband
• Point to point communication

83
Bluetooth Service Discovery Protocol
Applications
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband
RF
84
Example usage of SDP

• Establish L2CAP connection to remote device
• Query for services
• search for specific class of service, or
• browse for services
• Retrieve attributes that detail how to connect to
  the service
• Establish a separate (non-SDP) connection to use
  the service

85
Serial Port Emulation using RFCOMM
Applications
SDP
RFCOMM
Data

• Serial Port emulation on top of a packet oriented
  link
• Similar to HDLC
• For supporting legacy apps

Audio
L2CAP
Link Manager
Baseband
RF
86
Serial line emulation over packet based MAC
RFCOMM
RFCOMM
L2CAP
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

87
IP over Bluetooth V 1.0
Applications
SDP
RFCOMM
GOALS
Data

• Internet access using cell phones
• Connect PDA devices laptop computers to the
  Internet via LAN access points

Audio
L2CAP
Link Manager
Baseband
RF
88
LAN access point profile
IP
Access Point
PPP
RFCOMM
L2CAP
Baseband
89
Inefficiency of layering
Palmtop
LAN access point
IP
IP
packet oriented
PPP
PPP
rfc 1662
rfc 1662
byte oriented
RFCOMM
RFCOMM
packet oriented
L2CAP
L2CAP

• Emulation of RS-232 over the Bluetooth radio link
  could be eliminated

90
Terminate PPP at LAN access point
Palmtop
Access Point
IP
IP
PPP
ethernet
PPP
RFCOMM
RFCOMM
Bluetooth
Bluetooth

• PPP server function at each access point
• management of user name/password is an issue
• roaming is not seamless

91
L2TP tunneling
Palmtop
Access Point
PPP server
IP
IP
PPP
PPP
RFCOMM
RFCOMM
Bluetooth
Bluetooth

• 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

92
Seamless roaming with PPP
Server
AP1
AP2
MAC level registration
palmtop
93
IP over Bluetooth v 1.1 BNEP
Access Point
IP
Bluetooth Network Encapsulation Protocol (BNEP)
provides emulation of Ethernet over L2CAP
BNEP

• BNEP defines
• a frame format which includes IEEE 48 bit MAC
  addresses
• A method for encapsulating BNEP frames using
  L2CAP
• Option to compress header fields to conserve
  space
• Control messages to activate filtering of
  messages at Access Point

L2CAP
Baseband
94
Bluetooth Current Market Outlook
95
Market Forcasts for year 2005
Cahners In-stat (2000 forcast)
revised (2001 forcast)
Merrill Lynch (2000 forcast)
5.4 bn
revised (2001 forcast)
4.4 bn
2.1 bn
4.3 bn
1.4 bn
2.2 bn
4.4
1.5 bn
995 m
3.6
2.02
Revenue
Units sold annually
Chip price
96
Bluetooth Value chain
Wireless Carriers
Conspicuously missing
Stack providers
Software vendors
Integrators
Silicon
Radio
97
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

98
Value to carriers Cell phone as an IP gateway
Will Pilot and cell phone eventually merge?

• More bits over the air
• Enhanced user experience
• Palmpilot has a better UI than a cell phone
• Growth into other vertical markets

99
Value to carriers Call handoff
Cordless base
Threat or opportunity?

• More attractive calling plans
• Alleviate system load during peak periods
• Serve more users with fewer resources

100
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

101
References

• 1 IEEE 802.11, Wireless LAN MAC and Physical
  Layer Specification, June 1997.
• 2 Hirt, W. Hassner, M. Heise, N. IrDAVFIr
  (16 Mb/s) modulation code and system design.
  IEEE Personal Communications, vol.8, (no.1),
  IEEE, Feb. 2001.
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104
Synchronization using a Beacon (infrastructure)
beacon interval
B
B
B
B
access point
busy
busy
busy
busy
medium
t
B
value of the timestamp
beacon frame
105
Synchronization using a Beacon (ad-hoc)
beacon interval
B1
B1
station1
B2
B2
station2
busy
busy
busy
busy
medium
t
B
value of the timestamp
beacon frame
random delay