ShortRange Radio Frequency Networking

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Short-Range Radio Frequency Networking

• B. Ramamuthy

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Purpose

• Study personal area network PAN and related
  standard in bluetooth
• Based on java.sun.com Bluetooth API overview,
  design and development.
• Other sources Colouris text and palo wireless
  bluetooth resource center.

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Introduction

• Bluetooth is protocol for short range, frequency
  hopping radio link between devices.
• Devices such as phones, PDAs, medical devices
  that are bluetooth-enabled.
• Based on Industrial, Scientific and Medical (ISM)
  frequency band.
• Unlicensed and globally available.
• Originally from Ericsson bluetooth named after a
  Nordic king instrumental in integration of
  Scandinavian countries.

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Figure 3.18 A typical NAT-based home network
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Figure 3.22IEEE 802 network standards
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Details

• Radio technology
• Protocol stack
• Interoperable profiles
• How does the technology work?
• How is the technology used?
• Sample APIs to work with bluetooth
• javax.bluetooth javax.obex (for object exchange)

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Radio technology

• 2.5Ghz ISM band
• The bluetooth devices in a proximity form a
  piconet comprising a master and upto 7 devices.
• Piconets can connect, the master in a piconet can
  provide a bridge.
• Global and unlicensed.

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Protocol Stack

• Protocol stack provides
• a number of higher level APIs for service
  discovery and serial IO simulation,
• lower-level protocols for packet segmentation and
  reassembly,
• protocol multiplexing and QoS

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Bluetooth Protocol Stack
Application
Java API for Bluetooth wireless technology
(JSR-082)
WAP UDP/TCP IP PPP
Bluetooth Host Controller Stack (software)
OBEX
RFCOMM (serial port emulation)
Service discovery protocol (SDP)
Logical link control Adaptation Protocol (L2CAP)
Host controller interface (HCI)
Host Controller Interface Firmware
Link Manager protocol (LMP)
Bluetooth Host Controller Firmware Hardware
Baseband Link Controller (LC)
Bluetooth Radio
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Typical application Scenarios

• Bluetooth application can be either server or
  client
• Peer-peer exposing both client and server
  functionality
• Application need not be in Java
• However J2ME-based devices can avail of the
  bluetooth API.
• Though we discuss Java-based API here, MS Vista
  has a WS based API for devices.

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Application activities
java.sun.com Bluetooth intro
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Discovery
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Bluetooth clients

• DiscoveryAgent support discovery of services and
  devices.
• Clients wanting to be notified should implement
  and register Discovery Listener interface.

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Service/device discovery
A similar sequence can be assumed for device
Discovery. Services have a UUID There is
LocalDevice And RemoteDevice APIs to control the
devices.
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Service discovery (contd.)

• Once the local device has discovered at least one
  remote device, it can begin to search for
  available services
• Bluetooth applications it can use to accomplish
  useful tasks.
• Because service discovery is much like device
  discovery, DiscoveryAgent also provides methods
  to discover services on a Bluetooth server
  device, and to initiate service-discovery
  transactions

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Serial Port

• The RFCOMM protocol, which is layered over the
  L2CAP protocol, emulates an RS-232 serial
  connection.
• The Serial Port Profile (SPP) eases communication
  between Bluetooth devices by providing a
  stream-based interface to the RFCOMM protocol.
  Some capabilities and limitations to note
• Two devices can share only one RFCOMM session at
  a time.
• Up to 60 logical serial connections can be
  multiplexed over this session.
• A single Bluetooth device can have at most 30
  active RFCOMM services.
• A device can support only one client connection
  to any given service at a time.

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Interoperable Profiles

• Profiles have been developed to manage
  cross-platform interoperability among different
  manufacturers products.
• They describe how implementations of user models
  have to be accomplished.
• Lets examine the bluetooth profile as provided by
  palowireless.

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Profiles
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How does it work?Bluetooth frame structure
Header
SCO packets (e.g. for voice data) have a 240-bit
payload containing 80 bits of data triplicated,
filling exactly one timeslot.
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Server operation

• Construct a URL that indicates how to connect to
  the service, and store it in the service record
• Make the service record available to the client
• Accept a connection from the client
• Send and receive data to and from the client
• The URL placed in the service record may look
  something like
• btspp//102030405060740A1B1C1D1E1005

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Client operation

• To set up an RFCOMM connection to a server the
  client must
• Initiate a service discovery to retrieve the
  service record
• Construct a connection URL using the service
  record
• Open a connection to the server
• Send and receive data to and from the server

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Uses of Bluetooth

• Some are from Accenture
• Wiring the wired
• Locating lost items
• Activity sensing auditing
• Environmental control
• Simple transactions
• Medical applications are unlimited