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Title: Wireless Personal Area Networks (WPAN)


1
IT351 Mobile Wireless Computing
Wireless Personal Area Networks (WPAN) Part-2
IEEE802.15 Bluetooth
  • Objectives
  • To introduce Ad Hoc networking and discuss its
    application domain.
  • To provide a detailed study of the Bluetooth
    Wireless Technology including its architecture
    and protocol.

2
Outline
  • Motivation
  • History
  • Application and usage scenarios
  • Network architecture
  • Piconets
  • Scatternets
  • Protocol stack
  • Core protocols
  • Cable replacement and telephony control protocols
  • Profiles
  • Packet structure
  • Future developments
  • Wi-Fi vs. Bluetooth

3
Bluetooth - Motivation
  • A technology that aims at ad-hoc piconets -- LAN
    with very limited coverage without the need for
    infrastructure
  • To connect small devices in close proximity
    (about 10 m)
  • The envisaged gross data rate is 1 Mbits/s
  • Both asynchronous (data) and synchronous (voice)
    services
  • Transceiver should be very cheap
  • Low power consumption chip
  • Replace IrDA and solve its main problems
  • limited range 2m for built-in interfaces
  • line of sight
  • usually limited to two users, only point-to-point
    connections are supported
  • no internet working functions
  • has no MAC
  • Big advantage COST

4
Bluetooth
  • History
  • 1994 Ericsson (Mattison/Haartsen) initiated
    MC-link (multi communicator link) project
  • Renaming of the project Bluetooth according to
    Harald Blåtand Gormsen son of Gorm, King of
    Denmark in the 10th century
  • 1998 foundation of Bluetooth SIG,
    www.bluetooth.org
  • 1999 erection of a rune stone at Ercisson/Lund
    -)
  • 2001 first consumer products for mass market,
    spec. version 1.1 released
  • 2005 5 million chips/week
  • Special Interest Group
  • Original founding members Ericsson, Intel, IBM,
    Nokia, Toshiba
  • Added promoters 3Com, Agere (was Lucent),
    Microsoft, Motorola
  • gt 10000 members
  • Common specification and certification of
    products
  • Same time, an IEEE study group for a WPAN
    specifications started IEEE802.15 Requirements
    fulfilled by Bluetooth

5
History and hi-tech
1999 Ericsson mobile communications AB reste
denna sten till minne av Harald Blåtand, som fick
ge sitt namn åt en ny teknologi för trådlös,
mobil kommunikation.
6
and the real rune stone
Located in Jelling, Denmark, erected by King
Harald Blåtand in memory of his parents. The
stone has three sides one side showing a
picture of Christ.
Inscription "Harald king executes these
sepulchral monuments after Gorm, his father and
Thyra, his mother. The Harald who won the whole
of Denmark and Norway and turned the Danes to
Christianity."
This could be the original colors of the
stone. Inscription auk tani karthi kristna
(and made the Danes Christians)
Btw Blåtand means of dark complexion (not
having a blue tooth)
7
Bluetooth Was Originally a Cable-Replacement
Technology
8
In the Office
You arrive at the office
While in a meeting,
When inspecting equipment,
9
On the road
You arrive at the airport
You enter the airport waiting lounge,
You get on the rent-a-car bus,
10
Bluetooth - overview
  • Consortium Ericsson, Intel, IBM, Nokia, Toshiba
  • Scenarios
  • connection of peripheral devices
  • loudspeaker, joystick, headset
  • support of ad-hoc networking
  • small devices, low-cost
  • bridging of networks
  • e.g., GSM via mobile phone - Bluetooth - laptop
  • Simple, cheap, replacement of IrDA, low range,
    lower data rates, low-power
  • Worldwide operation 2.4 GHz
  • Available globally for unlicensed users
  • Resistance to jamming and selective frequency
    fading
  • FHSS over 79 channels (of 1MHz each), 1600hops/s
  • Coexistence of multiple piconets like CDMA
  • Links synchronous connections and asynchronous
    connectionless
  • Interoperability protocol stack supporting
    TCP/IP, OBEX, SDP
  • Range 10 meters, can be extended to 100 meters
  • Documentation over 1000 pages specification
    www.bluetooth.com

11
Bluetooth
  • 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
    (already lt 1)
  • Short range (10 m), low power consumption,
    license-free 2.45 GHz ISM
  • Voice and data transmission, approx. 1 Mbit/s
    gross data rate
  • Supports open-ended list of applications
  • Data, audio, graphics, videos

One of the first modules (Ericsson).
12
Characteristics
  • 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
  • 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
  • Voice link SCO (Synchronous Connection
    Oriented)
  • FEC (forward error correction), no
    retransmission, 64 kbit/s duplex, point-to-point,
    circuit switched
  • 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
  • Topology
  • Overlapping piconets (stars) forming a scatternet

13
(No Transcript)
14
Bluetooth Application Areas
  • Data and voice access points
  • Real-time voice and data transmissions
  • Cable replacement
  • Eliminates need for numerous cable attachments
    for connection
  • Ad hoc networking
  • Device with Bluetooth radio can establish
    connection with another when in range
  • Developed in late 90s
  • V1.2 ? 1Mbps
  • V2.0 ? 3Mbps
  • V3.0 ? 24Mbps

15
Bluetooth Architecture
  • Piconets and Scatternets
  • Piconet is the basic unit of networking
  • One master device and seven slaves
  • Slave can only communicate with its Master
  • Slave can be master of another piconet
  • This is called a scatternet

Piconet 1
Piconet 2
Slave
Master
Master
Scatternet
16
Piconets and Scatternets
  • Piconet
  • Basic unit of Bluetooth networking
  • Master and one to seven slave devices
  • Master determines channel and phase
  • Scatternet
  • Device in one piconet may exist as master or
    slave in another piconet
  • Allows many devices to share same area
  • Makes efficient use of bandwidth

17
Piconet
  • Collection of Bluetooth devices connected in an
    ad hoc fashion and synchronizes to a master node
  • One unit acts as master and the others as slaves
    for the lifetime of the piconet
  • All devices have the same network capabilities
  • The node establishing the piconet automatically
    becomes the master
  • Master determines hopping pattern, slaves have to
    synchronize
  • Each piconet has a unique hopping pattern
  • Participation in a piconet synchronization to
    hopping sequence
  • Each piconet has one master and up to 7
    simultaneous slaves (gt 200 could be parked)
  • Parked device is an inactive device (can be
    reactivated in milliseconds)
  • Standby device do not participate in piconet
  • If a parked device wants to communicate and there
    are 7 active slaves, then one of the slaves has
    to switch to park mode

P
S
S
M
P
SB
S
P
SB
PParked SBStandby
MMaster SSlave
18
Forming a piconet
  • All devices in a piconet hop together
  • Master gives slaves its clock and device ID
  • Hopping pattern determined by device ID (48 bit,
    unique worldwide)
  • Phase in hopping pattern determined by clock
  • Addressing
  • Active Member Address (AMA, 3 bit, 8 nodes) for
    all active nodes
  • Parked Member Address (PMA, 8 bit, 256) for
    parked nodes
  • SB devices do not need address

?
?
P
S
?
?
?
SB
SB
S
?
?
?
M
P
SB
?
?
?
?
SB
SB
SB
S
?
?
?
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SB
P
SB
SB
?
?
SB
SB
19
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
  • Master-slave can switch roles
  • Communication between piconets
  • Devices jumping back and forth between the
    piconets
  • Overlapping piconets experience collisions

Piconets (each with a capacity of 720 kbit/s)
P
S
S
S
P
P
M
M
SB
S
MMaster SSlave PParked SBStandby
P
SB
SB
S
20
Bluetooth Network Architecture
21
Piconets Scatternets
M
S
S
S
S
S
S
S
M/S
S
S
S
S
S
S
S
S
22
Bluetooth Standards
  • Details of various layers of Bluetooth protocol
    architecture
  • Bluetooth v1.1 ratified in 2002 as IEEE 802.15.1
  • Bluetooth v2.0 goes to up to 3Mbps 2004
  • Bluetooth v2.1 adopted July 2007
  • Wibree, an ultra low power Bluetooth technology
    adopted as part of the Bluetooth specification
    2007.
  • Bluetooth v3.0 adopted April 2009. up to 24Mbps

23
Protocol Architecture
  • Bluetooth is a layered protocol architecture
  • Core protocols
  • Cable replacement and telephony control protocols
  • Adopted protocols (using profiles)
  • Core protocols
  • Radio
  • Baseband
  • Link manager protocol (LMP)
  • Logical link control and adaptation protocol
    (L2CAP)
  • Service discovery protocol (SDP)

24
Protocol Architecture
  • Cable replacement protocol
  • RFCOMM
  • Telephony control protocol
  • Telephony control specification binary (TCS
    BIN)
  • Adopted protocols
  • PPP
  • TCP/UDP/IP
  • OBEX
  • WAP

25
Bluetooth protocol stack
vCal/vCard
NW apps.
telephony apps.
audio apps.
mgmnt. apps.
Control
TCS BIN
SDP
OBEX
TCP/UDP
AT modem commands
IP
BNEP
PPP
Audio
RFCOMM (serial line interface)
Logical Link Control and Adaptation Protocol
(L2CAP)
Host Controller Interface
Link Manager
Baseband
Radio
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.
26
Protocol stack (core protocols)
  • Bluetooth Radio
  • 2.4 GHZ frequency band
  • Defines modulation (FSK), frequency, power
  • Baseband
  • FHSS with 1600 hops/s, 79 channels, FSK
  • FHSS provides resistance to interference and
    multipath effects
  • CDMA between different piconets (hopping sequence
    from the node MAC address)
  • Access in piconet polling-based FH-TDD

27
Protocol stack (core protocols)
  • Two different kinds of physical links
  • Synchronous Connection oriented (SCO) for audio
  • Asynchronous ConnectionLess (ACL) transmission
    of data
  • Audio interfaces directly with the baseband.
    Each voice connection is over a 64Kbps SCO link.

28
Protocol stack (core protocols)
  • Host Controller Interface provides a uniform
    method of access to the baseband, control
    registers, etc through USB, PCI, or UART
  • Link Manager
  • Responsible for link set-up between BT devices
  • Set-up security functions like authentication and
    encryption
  • Synchronization between device clocks
  • Control and negotiate the baseband packet size
  • Control the power mode and duty cycle of BT radio
    and the connection states of BT nodes in a
    piconet
  • Mode management
  • switch master/slave role
  • change hold, sniff, park modes (low power mode)

29
Protocol stack (core protocols)
  • L2CAP Logical Link Control and Adaptation
    Protocol
  • Adapts to upper layer protocols
  • Protocol multiplexing
  • RFCOMM, SDP, telephony control
  • Segmentation and reassembly
  • QoS flow specification
  • Group abstraction
  • Create/close group, add/remove member
  • Provides two alternative services to upper-layer
    protocols
  • Connectionless service
  • Connection-oriented service A QoS flow
    specification is assigned in each direction
  • Exchange of signaling messages to establish and
    configure connection parameters
  • Service Discovery Protocol
  • locates the characteristics/profile of devices
    in the local area

30
Protocol Stack
  • Telephony Control Specification (TCS)
  • defines the call control signaling for the
    establishment of speech and data calls between
    Bluetooth devices
  • RFCOMM (cable replacement)
  • provides emulation of serial links

31
Bluetooth Adopted Protocols Profiles
  • Adopted Protocols
  • Standards from other bodies that are supported
  • PPP (Point to Point Protocol)
  • TCP/UDP/IP
  • OBEX (OBject EXchange), e.g. vCard
  • WAP (Wireless Application Protocol)
  • Usage models and profiles define how these are
    integrated

32
Bluetooth Adopted Protocols Profiles
  • Profiles
  • Specifications of how to support applications
  • Specify which parts of the total specification
    are mandatory, optional, or not applicable
  • No point having all functionality in all chips
  • Helps interoperability between vendors
  • Two main types
  • Wireless Audio
  • Cable replacement

33
Bluetooth Profiles
File Transfer
Headset Application
OBEX
Audio
AT commands
SDP
SDP
RFCOMM
RFCOMM
L2CAP
L2CAP
34
Establishing a connection BT States
  • Standby unconnected but awake
  • Inquiry listening or wanting to connect
  • Page setting up connections
  • Active Connected or Transmitting

35
Inquiry Procedure
  • Goal aims at discovering other neighboring
    devices
  • Potential master or inquiring node identifies
    devices in range that wish to participate
  • Transmits ID packet with inquiry access code
    (IAC)
  • Sends an inquiry message (packet with only the
    access code). This message is sent over a subset
    of all possible frequencies.
  • Listen for inquiry response
  • Occurs in Inquiry state
  • Device receives inquiry to be discovered node
  • Enters an inquiry_scan mode
  • When hearing the inquiry_message enter an
    inquiry_response mode send a Frequency Hop Sync
    (FHS) packet with address and timing information
  • Moves to page scan state
  • After discovering the neighbors and collecting
    information on their address and clock, the
    inquiring node can start a page routine to setup
    a piconet

36
Page Procedure
  • Goal e.g., setup a piconet after an inquiry
  • Paging node (master)
  • uses devices address to calculate a page
    frequency-hopping sequence
  • Sends a page message (i.e., packet with only
    Device Access Code (DAC) of paged node)
  • Repeated until a response is received
  • When a response is received send a FHS message to
    allow the paged node to synchronize
  • Paged node (slave)
  • Listens on its hopping sequence
  • When receiving a page message, send a
    page_response and wait for the FHS of the pager
  • When receiving, slave moves to connection state

37
Slave Connection State Modes
  • Active participates in piconet
  • Listens, transmits and receives packets
  • the device is uniquely identified by a 3bits
    AM_ADDR and is fully participating
  • Sniff only listens on specified slots
  • Hold does not support ACL packets
  • Reduced power status
  • May still participate in SCO exchanges
  • Park does not participate on piconet
  • Still retained as part
  • of piconet
  • Release AM_ADDR,
  • but have PM_ADDR
  • Low Power
  • Park (PM_Address) still a member of piconet,
    loses AM_Address
  • Hold (AM_Address) not active but wants to keep
    AMA
  • Sniff (AM_Address) listens to parts of the
    signals for activity

38
Summary of States of a Bluetooth device
standby
unconnected
inquiry
page
connecting
detach
connected AMA
transmit AMA
active
park PMA
hold AMA
sniff AMA
low power
Standby do nothing Inquire search for other
devices Page connect to a specific
device Connected participate in a piconet
Park release AMA, get PMA Sniff listen
periodically, not each slot Hold stop ACL, SCO
still possible, possibly participate in another
piconet
39
Example (without security)
  • A Person in a hotel wants to access her email
    over a BT enabled PDA. The device will
    automatically carry out the following steps
  • Inquiry
  • The device initiate an inquiry to find out
    access points (Masters) within its range
  • All nearby access points respond with their
    addresses
  • The device picks one out of the responding
    devices
  • Paging
  • The device will invoke paging procedure
  • It synchronizes with the access point in terms of
    clock, phase and frequency hop
  • Link establishment
  • The LMP will establish a link with the master
  • ACL link will be used (email)

40
Example (cont.)
  • Service discovery
  • The LMP will use SDP to discover what services
    are available at the master (email access to the
    host possible?)
  • Assume the service is available, else it would
    stop
  • Other available services will be presented to the
    user
  • L2CAP channel
  • With information obtained from SDP, an L2CAP
    channel will be created to the master
  • RFCOMM channel
  • An RFCOMM channel will be created over The L2CAP
    channel. This emulates serial port so
    applications can run without modifications
  • Network Protocols
  • The network protocols like TCP/IP can now send
    and receive data over the link

41
Bluetooth Establishing a connection
42
Wi-Fi v Bluetooth
  • Bluetooth
  • PAN (personal area)
  • Short range
  • 1-3Mbs (v12)
  • Ad Hoc
  • Cable replacement
  • Complex connection
  • Secure authentication via SSP (known problems)
  • Integrates (profiles)
  • Wi-Fi
  • LAN (local area)
  • Medium range
  • 54Mbps (a/g)
  • Infrastructure
  • LAN extension
  • Simple connection
  • Secure authentication via WPA2 (considered safe)
  • Layer 12 only

43
Bluetooth versions
  • Bluetooth 1.1
  • also IEEE Standard 802.15.1-2002
  • initial stable commercial standard
  • Bluetooth 1.2
  • also IEEE Standard 802.15.1-2005
  • eSCO (extended SCO) higher, variable bitrates,
    retransmission for SCO
  • AFH (adaptive frequency hopping) to avoid
    interference
  • Bluetooth 2.0 EDR (2004, no more IEEE)
  • EDR (enhanced date rate) of 3.0 Mbit/s for ACL
    and eSCO
  • lower power consumption due to shorter duty cycle
  • Bluetooth 2.1 EDR (2007)
  • better pairing support, e.g. using NFC
  • improved security
  • Bluetooth 3.0 HS (2009)
  • Bluetooth 2.1 EDR IEEE 802.11a/g 54 Mbit/s

44
WPAN IEEE 802.15.1 Bluetooth
  • Connection set-up time
  • Depends on power-mode
  • Max. 2.56s, avg. 0.64s
  • Quality of Service
  • Guarantees, ARQ/FEC
  • Manageability
  • Public/private keys needed, key management not
    specified, simple system integration
  • Special Advantages/Disadvantages
  • Advantage already integrated into several
    products, available worldwide, free ISM-band,
    several vendors, simple system, simple ad-hoc
    networking, peer to peer, scatternets
  • Disadvantage interference on ISM-band, limited
    range, max. 8 active devices/network, high set-up
    latency
  • Data rate
  • Synchronous, connection-oriented 64 kbit/s
  • Asynchronous, connectionless
  • 433.9 kbit/s symmetric
  • 723.2 / 57.6 kbit/s asymmetric
  • Transmission range
  • POS (Personal Operating Space) up to 10 m
  • with special transceivers up to 100 m
  • Frequency
  • Free 2.4 GHz ISM-band
  • Security
  • Challenge/response (SAFER), hopping sequence
  • Availability
  • Integrated into many products, several vendors

45
WPAN IEEE 802.15 future developments 1
  • 802.15.2 Coexistence
  • Coexistence of Wireless Personal Area Networks
    (802.15) and Wireless Local Area Networks
    (802.11), quantify the mutual interference
  • 802.15.3 High-Rate
  • Standard for high-rate (20Mbit/s or greater)
    WPANs, while still low-power/low-cost
  • Data Rates 11, 22, 33, 44, 55 Mbit/s
  • Quality of Service isochronous protocol
  • Ad hoc peer-to-peer networking
  • Security
  • Low power consumption
  • Low cost
  • Designed to meet the demanding requirements of
    portable consumer imaging and multimedia
    applications

46
WPAN IEEE 802.15 future developments 2
  • Several working groups extend the 802.15.3
    standard
  • 802.15.3a - withdrawn -
  • Alternative PHY with higher data rate as
    extension to 802.15.3
  • Applications multimedia, picture transmission
  • 802.15.3b
  • Enhanced interoperability of MAC
  • Correction of errors and ambiguities in the
    standard
  • 802.15.3c
  • Alternative PHY at 57-64 GHz
  • Goal data rates above 2 Gbit/s
  • Not all these working groups really create a
    standard, not all standards will be found in
    products later

47
WPAN IEEE 802.15 future developments 3
  • 802.15.4 Low-Rate, Very Low-Power
  • Low data rate solution with multi-month to
    multi-year battery life and very low complexity
  • Potential applications are sensors, interactive
    toys, smart badges, remote controls, and home
    automation
  • Data rates of 20-250 kbit/s, latency down to 15
    ms
  • Master-Slave or Peer-to-Peer operation
  • Up to 254 devices or 64516 simpler nodes
  • Support for critical latency devices, such as
    joysticks
  • CSMA/CA channel access (data centric), slotted
    (beacon) or unslotted
  • Automatic network establishment by the PAN
    coordinator
  • Dynamic device addressing, flexible addressing
    format
  • Fully handshaked protocol for transfer
    reliability
  • Power management to ensure low power consumption
  • 16 channels in the 2.4 GHz ISM band, 10 channels
    in the 915 MHz US ISM band and one channel in the
    European 868 MHz band
  • Basis of the ZigBee technology www.zigbee.org

48
ZigBee
  • Relation to 802.15.4 similar to Bluetooth /
    802.15.1
  • Pushed by Chipcon (now TI), ember, freescale
    (Motorola), Honeywell, Mitsubishi, Motorola,
    Philips, Samsung
  • More than 260 members
  • about 15 promoters, 133 participants, 111
    adopters
  • must be member to commercially use ZigBee spec
  • ZigBee platforms comprise
  • IEEE 802.15.4 for layers 1 and 2
  • ZigBee protocol stack up to the applications

49
WPAN IEEE 802.15 future developments 4
  • 802.15.4a
  • Alternative PHY with lower data rate as extension
    to 802.15.4
  • Properties precise localization (lt 1m
    precision), extremely low power consumption,
    longer range
  • Two PHY alternatives
  • UWB (Ultra Wideband) ultra short pulses,
    communication and localization
  • CSS (Chirp Spread Spectrum) communication only
  • 802.15.4b, c, d, e, f, g
  • Extensions, corrections, and clarifications
    regarding 802.15.4
  • Usage of new bands, more flexible security
    mechanisms
  • RFID, smart utility neighborhood (high
    scalability)
  • 802.15.5 Mesh Networking
  • Partial meshes, full meshes
  • Range extension, more robustness, longer battery
    live
  • 802.15.6 Body Area Networks
  • Low power networks e.g. for medical or
    entertainment use
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