ever wanted to know the in's and out's of bluetooth? well if you did you are in the right place; in this article we will discuss what bluetooth is, how does it work? and where is it used? hope you enjoy!
1. How Bluetooth Works
Bluetoothdeviceswill normallyoperate at2.4 GHZ in the license free,globallyavailable ISMradio
band.The advantage tothisband includesworldwide availabilityandcompatibility.A disadvantage
to thishowever,isthatthe devicesmustshare this bandwithotherRFemitters.Thisincludes
automobile securitysystems,otherwirelessdevices, andothernoise sources,suchasmicrowaves.
To overcome thischallenge,Bluetoothemploysa fastfrequencyhoppingschemeandthereforeuses
shorterpacketsthan otherstandardswithinthe ISMband.This scheme helpstomake Bluetooth
communicationmore robustandmore secure. Frequencyhopping Frequencyhoppingisbasically
jumpingfromfrequency tofrequencywithinthe ISMradioband.
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Aftera bluetoothdevice sendsorreceivesapacket,it and the device (ordevices) it’s
communicatingwith hoptoanotherfrequencybefore the nextpacketis sent.Thisscheme offers
three advantages:
1. AllowsBluetoothdevicestouse the entiretyof the availableISMband,while never transmitting
froma fixedfrequencyformore thana shortperiodof time.Thishelpsinsure that Bluetooth
conformsto the ISMrestrictionsonthe transmissionquantityperfrequency.
2. Ensuresthat any interference won’t lastlong.Anypacketthatdoesn’tarrive safely toits
destinationcanbe resenttothe next frequency.
3. Providesabase level of securityas it’sveryhardfor an eavesdroppingdevice topredictwhich
frequencythe Bluetoothdeviceswill use next. The connecteddeviceshowever,mustagree uponthe
frequencytheywilluse next.
The specification inBluetoothensuresthisintwoways.First,it definesamasterandslave type
relationshipbetween bluetoothdevices.Next,itspecifiesanalgorithm calculatingthe frequencyhop
sequences. A Bluetoothdevice thatoperatesinmastermode can communicate withuptoseven
devicesthatare setin slave mode.Toeach of the slaves,the master Bluetoothdevice will sendits
ownunique address andthe value of itsowninternal clock.The informationsentisthenusedto
calculate the frequencyhopsequences. Because the masterdevice andeachof the slave devicesuse
the same algorithmwiththe same initial input,the connecteddeviceswillalwaysarrive togetherat
the nextfrequencythattheyhave agreed upon. Asa replacementforcable technology,it’sno
wonderthatBluetoothdevicesare usuallybattery powered,suchaswirelessmice andbattery
powered cell phones.Toconserve the power,mostdevices operateinlow power.Thishelpstogive
Bluetooth devicesarange of around5 – 10 meters. Thisrange is far enoughforwireless
communication butclose enoughtoavoiddrawingtoomuchpower fromthe powersource of the
device.
