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Bluetooth: The Universal Radio Interface for Ad hoc, Short-Range Connectivity
CIS 642
Maria Adamou

2. Overview Introduction Bluetooth Air Interface Architecture
Connection Establishment
Piconets and Scatternets
Power Management
Security
Competing technologies
Issues facing Bluetooth
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3. Introduction
In February 1998 five major telecom and PC companies – Ericsson, Nokia, IBM, Toshiba, and Intel- formed a Special Interest Group (SIG) to create a standard radio interface for short-range connectivity between electronic devices
The radio interface was named Bluetooth after a Danish Viking king Harald Bluetooth who united Denmark and Norway during 10th century
This group was further expanded in December 1999 with 3Com, Lucent, Microsoft and Motorola
Today more than 2000 companies have joined as adopters of the Bluetooth technology
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4. What is Bluetooth
Bluetooth is a universal standard radio interface for short-distance, point-to-multipoint voice and data transfer between portable devices
Its nominal link range is from 10 cm to 10 meters but can be extended to 100 meters by increasing the transmission power
Printers, desktops, fax machines, cellular phones and virtually any other digital device can be part of the Bluetooth system and form ad hoc groupings that replace cables
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5. Goals The system must operate globally
The system must support peer connectivity, connections are made on an ad hoc basis
The connection must support voice and data
Ability to withstand interference from other sources
The radio transceiver must be small and operate at low power, to fit into small, portable devices, such as mobile phones, headsets, PDAs etc
Low cost, short-range
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6. User Scenarios
3-in-1 phone: At home, portable phone (fixed line charge), when on the move, mobile phone (cellular charge), and when your phone comes within range of another mobile phone a walkie-talkie (no telephony charge)
Ultimate Headset: Connect your wireless headset to your mobile phone, mobile computer or any wired connection
Interactive Conference in meetings and conferences
Automatic Synchronizer: Automatic synchronization of your desktop, PDA, notebook and your mobile phone.
Internet Bridge: use of a mobile telephone or cordless modem device that provides modem services to a PC, to enable cordless access for dial-up networking services.
LAN access: use of a device that acts as a LAN access point (LAP) providing Bluetooth access services to one or more data terminals.
many others...
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7. Definitions
Piconet: a collection of (up to eight) devices connected via Bluetooth technology in an ad hoc fashion. Each piconet is identified by a different frequency hopping sequence and all hosts on the same piconet are synchronized
Scatternet: two or more independent and non-synchronized piconets that communicate with each other
Master unit: the device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconet
Slave units: all devices in a piconet that are not the master (up to 7 active units for each master)
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8. Bluetooth Air Interface
License-free, globally available frequency band: Industrial-Scientific-Medical (ISM) band, at 2.45 GHz in most countries in the world
Frequency-hopping (FH) spread spectrum to better support low-cost, low-power radio implementations with maximum immunity to interference
Channels use a Frequency-Hopping/ Time Division Duplex (TDD) scheme: the channel is divided into slots of 625ms giving 1600hops/sec and subsequent slots are alternately used for transmitting and receiving (TDD)
One packet can be transmitted per slot
The channel makes use of 79 equally spaced 1-MHz channels (from 2,402 MHz to 2,480 MHz), frequency shift keying (FSK) modulation
1 Mb/s transmission/reception rate
2 power levels: 0dBm for 10 meters or 20dBm (100 meters)
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9. Packet Definition
72 bits
54 bits
bits
Access code
Packet
Header
Payload 3 4 1 1 1 8
M_ADDR
TYPE
FLOW
ARQN
SEQN
HEC
72-bit access code unique for the channel, used for packet identification and synchronization, derived from the master
Header: 3-bit slave address, packet type, flow control bits, ARQ bit, sequence number, Header-Error-Check fields
Payload: bits
Multislot packets have been defined: a packet may cover one, three or five slots, sent on a single hop channel
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10. Links supported Two types of links to support multimedia applications:
Synchronous Connection-Oriented (SCO) link
Asynchronous Connectionless Link (ACL)
SCO links support symmetrical, circuit-switched point-to-point connections typically used for voice
Reservation is carried out by the master and the slave
ACL links support packet-switched point-to-multipoint connection typically used for bursty data transmission
Master units use a polling scheme to control ACL connections: a master-to-slave packet or a POLL packet poll the slave. Collisions are avoided.
All SCO and ACL traffic is scheduled by the master
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11. Architecture
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12. RF and Baseband
Controls the unit’s synchronization and transmission frequency hopping sequence, compresses and puts data into packets, assigning identifiers etc
The two link types SCO and ACL are also managed by this layer
Takes care of retransmissions and transmission error detection and recovery
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13. HCI
Provides a uniform interface method for accessing the Bluetooth hardware capabilities
It contains a command interface to the Baseband controller and link manager and access to the hardware status
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14. Link Manager Protocol (LMP)
Responsible for:
Connection set-up
Generation, exchange and control of link and encryption keys for Authentication and Encryption
Link mode negotiation and set-up, e.g. data or data/voice
Sending and receiving of data
Management of power modes, power consumption and state of a unit
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15. Logical Link Control and Adaptation Protocol (L2CAP)
L2CAP is an interface between upper layer protocols and baseband and operates in parallel to LMP
Multiplexing: L2CAP must support protocol multiplexing, since a number of protocols (e.g. SDP, RFCOMM and TCS Binary) can operate over L2CAP.
Segmentation and Reassembly: Data packets exceeding the Maximum Transmission Unit, MTU, must be segmented before being transmitted. This and the reverse functionality, reassemble, is performed by L2CAP.
Quality of Service: The establishment of an L2CAP connection allows the exchange of information regarding current Quality of Service for the connection between the two Bluetooth units
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16. Service Discovery Protocol (SDP)
Defines how a Bluetooth client's application shall act to discover available Bluetooth servers' services (like printing, file transfer, synchronization) and their Bluetooth characteristics.
Defines how a client can search for a service based on specific attributes without the client knowing anything of the available services.
Provides means for the discovery of new services becoming available when the client enters an area where a Bluetooth server is operating.
Provides functionality for detecting when a service is no longer available
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17. Other protocols
RFCOMM - Cable replacement protocol: emulates serial port to cover applications that use serial ports of the kind used in PCs and provides transport capabilities for upper level services
Telephony Control Protocols
TCS BIN: defines the call control signaling for the establishment and release of calls between units
TCS AT Commands: transmitting control signals for telephony control
Adopted protocols
PPP
TCP/UDP/IPThe TCP/UDP/IP standards are defined to operate in Bluetooth units allowing them to communicate with other units connected, for instance, to the Internet.
WAP
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18. Connection Establishment
When units are not connected they are in STANDBY mode, where they listen to 32 unique (for each unit) wake-up channels, for page or inquiry messages, for about 10ms each
Wake-up interval ranges between 0 to 3.84s (usually 1.28s)
A unit enters the PAGE or INQUIRY state in which it broadcasts page or inquiry messages
If the paging unit knows the identity of the unit to which it wants to connect, it knows the wake-up sequence and transmits the unit’s access code every 1.25ms to 16 different hop frequencies defined for the slave unit (total 10ms period)
If the pager does not know the identity of the unit, it broadcasts an inquiry message according to a common inquiry sequence, every 0 to 2.56s
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19. Connection Establishment
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20. Piconets and Scatternets
Two or more Bluetooth units that share a FH channel form a piconet. At most 1 master and 7 slaves can be in one piconet
Any unit can become a master, but by definition the paging unit that establishes the piconet is the master
The master identity and clock specify the channel parameters
All devices in a piconet are synchronized to the same FH sequence
Up to 10 piconets can co-exist with overlapping coverage areas and form a scatternet
A unit can be a master in one piconet and a slave in another, or slave in several piconets
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21. Power Management
Frequency-hopping mechanism provides synchronization between master-slaves therefore no dummy packets have to be exchaged
A receiver can quickly decide whether a packet is present or not, by the access code and the header and sleep for the rest of the slot
Power-save modes:
HOLD mode, where no communication is possible for a specified hold time
SNIFF mode, where the slave listens only to some slots (depends on the application)
PARK mode, where the slave listens to the master’s beacon at large intervals to re-synchronize, does not have a MAC address and does not participate in the traffic
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22. Modes of operation
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23. Security
As radio signals can be easily intercepted, Bluetooth devices have built-in security to prevent eavesdropping or falsifying the origin of messages (spoofing)
The main security features are:
a challenge-response routine – for authentication
stream cipher – for encryption
session key generation – session keys can be exchanged during a connection
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24. Competing Technologies
Infrared Data Association (IrDA) vs Bluetooth
IEEE b vs Bluetooth
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25. IrDA vs Bluetooth Wireless Standard
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IrDA vs Bluetooth
Wireless Standard
IrDA already proven standard (50 million units)
Bluetooth still in development
Data Transfers
IrDA up to 4Mbps; 16Mbps( under development)
Bluetooth 1Mbps(max) 721Kbps(average)
Range
IrDA – 3 feet
Bluetooth - 30 feet (or more)
Line of Sight
Required for IrDA, can be advantage in crowded situations
Not required for Bluetooth (penetrates walls)
Cost of Implementation
IrDA - Currently $2
Bluetooth- Initially $20
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26. IEEE 802.11b vs Bluetooth IEEE 802.11b high rate Bluetooth Market
IEEE b high rate
Bluetooth
Market
Home, school, and enterprise WLAN
Wireless cable
Technology
2.4 GHz, ISM, DSSS
FHSS, 1,000 hops/sec
Data rate
11 Mbps
1 Mbps
Power
20 dBm
0 dBm, 20 dBm
Range
50 m
1 to 10 m, 50 m
Topology
128 devices, CSMA/CA
8 devices, Piconet
Security
Optional WEP*
Encryption, authentication
Separate voice channel
Optional
Yes
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27. IEEE 802.1b vs Bluetooth
The task group deals with Co-existence and interoperability between Bluetooth and b
Bluetooth offers ubiquity and low price
Both technologies can co-exist reasonably well: Bluetooth will function as an aid to a larger-scale network
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28. Issues facing Bluetooth
Implementation Issues
Cost
Interoperability
Performance
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29. Future of Bluetooth
Conservative estimates foresee several hundred million Bluetooth-enabled devices in the next five years
By 2004, 75% of all mobile devices will support Bluetooth
Communications companies will no longer have to build external cables and PC cards to enable their wireless phones and network cards to interface with computers
Bluetooth will provide the "glue" for the merger of wireless and computers.
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30. References
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