Transcript Mobile IP: Introduction

Bluetooth: Introduction
Reference: Chapter 15, Wireless Communications and Networks,
by William Stallings, Prentice Hall
Overview
• Initially developed by Ericsson in 1994
• Using 2.4 GHz band (up to 720 kbps, 10m)
• Provide consumer with the ability to do
– Make calls from a wireless headset connected
remotely to a cell phone
– Eliminate cables linking computers to printers,
keyboards, and the mouse
– Hook up MP3 players wirelessly
– Set up home networks
– Call home from a remote location to turn
appliances on and off, set the alarm, and monitor
activity
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Overview (cont)
• Bluetooth Applications
– Data and voice access points
– Cable replacement
– Ad Hoc networking
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Protocol Architecture
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Core Protocols
• Radio
– Details of the air interface, including frequency, the
use of frequency hopping, modulation scheme,
and transmit power
• Baseband
– Concerned with connection establishment within a
piconet, addressing, packet format, timing and
power control
• Link manager protocol (LMP)
– Responsible for link setup between BT devices and
ongoing link management
 Security aspects: authentication and encryption
 Control and negotiation of baseband packet sizes
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Core Protocols (cont)
• Logical link control and adaptation
protocol (L2CAP)
– Adapts upper-layer protocols to the baseband
layer
– Provide both connectionless and connectionoriented services
• Service discovery protocol (SDP)
– Device information, services, and the
characteristics of the services can be queries
to enable the establishment of a connection
between two or more BT devices
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Bluetooth Protocols
• RFCOMM
– Cable replacement protocol
– RFCOMM presents a virtual serial port that is
designed to make replacement of cable
technologies as transparent as possible
– Provides for binary data transport and
emulates EIA-232 control signals over the BT
baseband layer
• Telephony control protocol (TCS BIN)
– Defines the call control signaling for the
establishment of speech and data calls
between BT devices
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Usage Model
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Usage Model (cont)
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Usage Model (cont)
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Piconets
• Piconet
– Basic unit of networking in BT
– Consisting of a master and from 1 to 7 active
slave devices
– The radio designated as the master makes the
determination of the channel and phase that
shall be used by all devices on this piconet
– A slave may only communicate with the master
and may only communicate when granted
permission by the master
– A device in one piconet may also exist as part
of another piconet and may function as either
a slave or master in each piconet
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Master/Slave Relationships
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Wireless Network Configurations
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Wireless Network Configurations
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Radio & Baseband Parameters
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Radio Specification
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Baseband Specification
1600 hops per second
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Baseband Specification (cont)
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Baseband Specification (cont)
• Physical links
– Synchronous connection oriented (SCO)
 Allocates a fixed bandwidth between a point-to-point
connection involving the master and a single slave
 The master maintains the SCO link by using reserved
slots at regular intervals
 The basic unit of reservation is two consecutive slots
(one in each transmission direction)
 The master can support up to 3 simultaneous SCO
linkes, while a slave can support 2 or 3 SCO links
 SCO packets are never retransmitted
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Baseband Specification (cont)
– Asynchronous connectionless (ACL)
 A point-to-multipoint link between the master and all
the slaves in the piconet
 In slots not reserved for SCO links
 The master can exchange packets with any slave on
a per-slot basis
 Only a single ACL link can exist
 For most ACL packets, packet retransmission is
applied
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Baseband Specification (cont)
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Baseband Specification (cont)
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Baseband Specification (cont)
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Baseband Specification (cont)
• Packet format
– Access code: used for timing synchronization,
offset compensation, paging and inquiry
 Three types of access codes
 Channel access code (CAC): identifies a piconet
 Device access code (DAC): used for paging and its
subsequent response
 Inquiry access code (IAC): used for inquiry purposes
– Header: used to identify packet type and to
carry protocol control information
– Payload: contains user voice or data, and in
most cases a payload header
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Baseband Specification (cont)
• Packet Header
– AM_ADDR
 3-bit AM_ADDR contains the “active mode” address
(temporary address assigned to this slave in this
piconet) of one of the slaves
 A transmission from the master to a slave contains
that slave’s address
 A transmission from a slave contains its address
 The value 0 is reserved for a broadcast from the
master to all slaves in the piconet
– Type
 Identifies the type of packet
 For SCO: HV1, HV2, HV3
 For ACL: DM1, DM3, DM5, DH1, DH3, DH5
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Baseband Specification (cont)
– Flow
 Provides a 1-bit flow control mechanism for ACL
traffic only
– ARQN
 Provides a 1-bit acknowledgement mechanism for
ACL traffic protected by a CRC
 If the reception was successful, an ACK (ARQN=1) is
returned; otherwise a NAK (ARQN=0) is returned
– SEQN
 Provides a 1-bit sequential numbering scheme
– HEC (Header Error Control)
 An 8-bit error detection code used to protect the
packet header
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Baseband Specification (cont)
• Payload format
– Payload header
 An 8-bit header is defined for single-slot packets,
and a 16-bit header is defined for multislot packets
– Payload body: user information
– CRC: 16-bit CRC code on data payload
• Payload header
– L_CH: identifies the logical channel
– Flow: used to control flow at the L2CAP level
– Length: the number of bytes of data in the
payload, excluding the payload header and
CRC
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Baseband Specification (cont)
• Error correction
– 1/3 rate FEC (forward error correction)
 Used on the 18-bit packet header
 For the voice field in an HV1 packet
 Simply sending three copies of each bit
 A majority logic is used
– 2/3 rate FEC
 Used in all DM packets, in the data field of the DV
packets, in the FHS packet, an in the HV2 packet
 Hamming code
 Can correct all single errors and detect all double
errors in each codeword
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Baseband Specification (cont)
– ARQ (automatic repeat request)
 Used with DM and DH packets, and the data field of
DV packets
 Similar to ARQ schemes used in data link control
protocols
 1. Error detection
 2. Positive acknowledgement
 3. Retransmission after timeout
 4. Negative acknowledgement and retransmissions
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Baseband Specification (cont)
• Logical Channels
– Five types of logical data channels designed to
carry different types of payload traffic
– 1. Link control (LC)
 Carries low level link control information: ARQ, flow
control, payload characterization
 The LC channel is carried in every packet except in
the ID packet, which has no packet header
– 2. Link manager (LM)
 Transports link management information between
participating stations
 Support LMP traffic and can be carried over either an
SCO or ACL link
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Baseband Specification (cont)
– 3. User asynchronous (UA)
 Carries asynchronous user data: normally carried
over the ACL link
– 4. User isochronous (UI)
 Carries isochronous user data: normally carried over
the ACL link but may be carried in a DV packet on the
SCO link
– 5. User synchronous (US)
 Carries synchronous user data
 This channel is carried over the SCO link
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Baseband Specification (cont)
State diagram
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Baseband Specification (cont)
• Inquiry procedure
– The first step in establishing a piconet is for a
potential master to identify devices in a range that
wish to participate in the piconet
– Once a device has responded to an Inquiry, it
moves to the page scan state to await a page from
the master in order to establish a connection
• Page procedure
– Once the master has found devices within its
range, it is able to establish connections to each
device, setting up a piconet
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Baseband Specification (cont)
• Channel state
– Standby
 The default state, low-power state
– Connection
 The device is connected to a piconet as a master or a
slave
– Page
 Device has issued a page
 Used by the master to activate and connect to a
slave
 Master sends page message by transmitting slave’s
device access code (DAC) in different hop channels
– Page scan
 Device is listening for a page with its own DAC
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Baseband Specification (cont)
– Master response
 A device acting as a master receives a page
response from a slave
– Slave response
 A device acting as a slave responds to a page from a
master
– Inquiry
 Device has issued an inquiry, to find the identity of
the devices within range
– Inquiry scan
 Device is listening for an inquiry
– Inquiry response
 A device that has issued an inquiry receives an
inquiry response
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Baseband Specification (cont)
• Connection state
– Active
 The slave actively participates in the piconet by
listening, transmitting and receiving packets
 The master periodically transmits to the slaves to
maintain synchronization
– Sniff
 The slave does not listen on every receive slot but
only on specified slots for its message
 The slave can operate in a reduced-power status the
rest of the time
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Baseband Specification (cont)
– Hold
 The device in this mode does not support ACL
packets and goes to reduced power status
 The slave may still participate in SCO exchanges
– Park
 When a slave does not need to participate on the
piconet but still is to be retained as part of the
piconet, it can enter the park mode, which is a lowpower mode with very little activity
 The device is given a parking member address
(PM_ADDR) and loses its active member (AM_ADDR)
address
 With the use of the park mode, a piconet may have
more than seven slaves
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Link Manager Specification
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Link Manager Specification (cont)
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L2CAP
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L2CAP Formats
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L2CAP Signaling Command Code
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L2CAP Quality of Service
• Flow specification
– Service type
– Token rate (bytes/second)
– Token bucket size (bytes)
– Peak bandwidth (bytes/second)
– Latency (microseconds)
– Delay variation (microseconds)
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L2CAP Quality of Service
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