Mobile IP: Introduction
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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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