Bluetooth by kishorkna

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									       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni




                       Bluetooth


                     Ing. A. Leonardi




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni




Bluetooth is a short range (10-100 m) and low-cost wireless
network system to replace cables and give RF connection
between consumer devices.




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             Università degli Studi di Catania
    Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                                     Scenarios




                                                                Figure 2: Peripheral interconnects

Figure 1: Personal Area Networking (PAN)




                                           Figure 3: Voice/Data Access Points




             Università degli Studi di Catania
    Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                Bluetooth Ad Hoc Networks (1)

     Piconet
        The technology allows creation of small ad-hoc networks
        (piconets) consisting of at most 8 simultaneously active
        devices.


     Scatternet
        Many different piconets may coexist and interoperate in
        the same physical area.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

         Bluetooth Ad Hoc Networks (2)

A piconet consists of one master and up to 7 slaves.


The master is the central entity that decides transmit/receive
resource allocation to different slaves and thus controls
bandwidth usage among slaves.


Two or more piconets can be linked together to form a
scatternet. In this, one device in each piconet (either a
master or a slave) acts like a bridge between them.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

         Bluetooth Ad Hoc Networks (3)




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

         Bluetooth Ad Hoc Networks (4)

A Bluetooth device can function as either a master as or a
slave.


Each piconet can only have a single master, but a master in
one piconet can be a slave in another piconet.


This allows a dynamic topology construction of complex
scatternet.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                    Radio channel (1)

Bluetooth operates in the unlicensed ISM band at 2.4 GHz.


A CDMA-FH/TDD system is used:
    79 carriers spaced 1 MHz, in the band 2400-2483,5 MHz;
    the channel is divided into time slots where each slot
   corresponds to an RF hop frequency;
    consecutive slots correspond to different RF hop frequencies;
    all Bluetooth units participating in the piconet are time- and
   hop-synchronized to the channel;
    a TDD scheme is used where master and slave alternatively
   transmit.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                    Radio channel (2)

The channel is divided into time slots, each 625 μs in lenght,
thus the nominal hop rate is 1600 hops/s.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Piconet channel (1)

The piconet channel is represented by a pseudo-random
hopping sequence hopping through the 79 RF channels.


The hopping sequence is unique for the piconet and is
determined by the Bluetooth device address of the master.


The phase in the hopping sequence is determined by the
Bluetooth clock of the master.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Piconet channel (2)




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                     Physical links (1)

Between master and slave(s), different types of links can be
established. Two link types have been defined:
    Synchronous Connection-Oriented (SCO) link
    Asynchronous Connection-Less (ACL) link


The SCO link is a point-to-point link between a master and a
single slave in the piconet. The master maintains the SCO
link by using reserved slots at regular intervals.


The SCO link reserves slots and can therefore be
considered as a circuit-switched connection between the
master and the slave.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                     Physical links (2)

The ACL link is a point-to-multipoint link between the
master and all the slaves participating on the piconet.


In the slots not reserved for the SCO link(s), the master can
establish an ACL link on a per-slot basis to any slave,
including the slave(s) already engaged in an SCO link.


The ACL link provides a packet-switched connection
between the master and all active slaves participating in the
piconet.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                     Physical links (3)

A slave is permitted to return an ACL packet in the slave-to-
master slot if and only if it has been addressed in the
preceding master-to-slave slot. If the slave fails to decode
the slave address in the packet header, it is not allowed to
transmit.


ACL packets not addressed to a specific slave are
considered as broadcast packets and are read by every
slave.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                        Example (1)

An ACL link in a piconet with three devices:




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                        Example (2)

A mixed link in a piconet with four devices:




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Multislot packet (1)

For a multi-slot packet, the RF hop frequency to be used for
the entire packet is derived from the Bluetooth clock value
in the first slot of the packet.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Multislot packet (2)

The maximum throughput in an ACL link is obtainable with a
piconet of two devices that use multislot packets of 5 slots:


    Maximum asymmetric throughput: 723.2 kb/s in one direction
   and 57.6 kb/s in the opposite direction; using 5-multislot
   packets in one direction and single slot packets in the other.


    Maximum symmetric throughput: 433.9 kb/s, using 5-multislot
   packets in both directions.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

            ARQ scheme in the ACL link

Bluetooth uses a fast, unnumbered acknowledgment
scheme:
    an ACK or a NAK is returned in response to the receipt of
   previously received packet.


The slave will respond in the slave-to-master slot directly
following the master-to-slave slot.


The master will respond at the next event it will address the
same slave (the master may have addressed other slaves
between the last received packet from the considered slave
and the master response to this packet).




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni


            ARQ scheme in the ACL link
                    Example




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

              Bluetooth protocols stack




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

       Bluetooth protocols description (1)
Bluetooth Radio: defines the requirements of the Bluetooth
transceiver device operating in the 2.4GHz ISM band


Baseband:
     manages physical channels and links apart from other services like
   error correction, data whitening, hop selection and Bluetooth security;
    manages asynchronous and synchronous links, handles packets and
   does paging and inquiry


LMP: Manager carries out link setup, authentication, link
configuration and other protocols




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

       Bluetooth protocols description (2)
HCI: provides a command interface to the baseband controller and
link manager, and access to hardware status and control registers


L2CAP: provides connection-oriented and connectionless data
services to upper layer protocols with protocol multiplexing
capability, segmentation and reassembly operation, and group
abstractions.


RFCOMM: provides emulation of serial ports over the L2CAP


SDP: provides a means for applications to discover which services
are available and to determine the characteristics of those
available services.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

              Connection establishment

By definition, the master is represented by the Bluetooth
unit that initiates the connection (to one or more slave
units).


Once a piconet has been established, master-slave roles
can be exchanged.


There are two major states: STANDBY and CONNECTION; in
addition, there are seven substates, page, page scan,
inquiry, inquiry scan, master response, slave response, and
inquiry response.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

   Connection establishment state diagram




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                Inquiry procedures (1)

A device that want to discover other devices enters the
inquiry state


A device that wants to be discovered enters the inquiry scan
state


During an inquiry substate, the discovering unit collects the
Bluetooth device addresses and clocks of all units that
respond to the inquiry message.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                Inquiry procedures (2)

The inquiry message broadcast by the source does not
contain any information about the source itself. However, it
may indicate which class of devices should respond.


The inquiry response is optional: a unit is not forced to
respond to an inquiry message.


Every devices during the inquiry procedure uses a well
known inquiry hopping sequence of 32 dedicated
frequencies.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Page procedures (1)

The page substate is used by the master (source) to activate
and connect to a slave (destination) having the address
known during inquiry phase.


The master tries to capture the slave by repeatedly
transmitting in different hop channels, according to the
hopping sequence of the slave (obtained from its address).


The slave enters periodically the page scan state.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Page procedures (2)

Although the master and the slave use the same hopping
sequence, they surely use different phases  they may
never meet each other.


To compensate for the clock drifts, the master will send its
page message twice per each TX slot on two different hop
frequencies.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Page procedures (3)

When a page message is successfully received by the slave,
there is a coarse FH synchronization between the master
and the slave. They enter a response routine to exchange
information for a better synchronization.


Then the master and the slave changes to the channel
(master’s) hopping sequence.


The channel access code and channel hopping sequence
are derived from the Bluetooth device address of the
master. The timing is determined by the master clock.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

                   Page procedures (4)




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
           Baseband Methods for Power
                Conservation (1)
Sniff Mode is used when a slave shall participate in the
piconet only in a sniff interval.


In ACL link, keeping synchronization in a piconet at the
connection establishment, it receives and transmits packets
only in the time slots of the fixed interval called "sniff cycle".
In other time slots, power consumption is saved by
performing only the processing indispensable to maintain
synchronization of a piconet.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
           Baseband Methods for Power
                Conservation (2)
Hold Mode is useful when a BT Device doesn’t want to
participate in the connection for a Hold Mode Length.


In ACL link, keeping synchronization in a piconet at the
connection establishment, a communication link is
temporarily interrupted during a fixed period (defined as
"hold time"). Power consumption is saved by performing
only the processing indispensable to maintain
synchronization of a piconet during hold time. If the hold
time passes, it will return to the original ACL link and
transmission and reception of a packet will be resumed.




       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
           Baseband Methods for Power
                Conservation (3)
Park Mode is used to render the slaves inactive but still
synchronized to the master using the beacon interval.


It is low power consumption mode peculiar to a slave (a
master does not become Park mode). Altough the
synchronization of a piconet is maintained, the slave node
can only receive packets but can not send packets. Except
the receiving slot for every fixed interval called "beacon
cycle", power consumption is saved by performing only the
processing indispensable to maintain synchronization of a
piconet.




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       Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
           Baseband Methods for Power
                Conservation (4)
Entry into sniff, hold or park mode requires an established
ACL Connection.
The following table summarizes the modes and the BT Role
that can request, force, activate or exit the modes.




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