cognitive radio principal

8/16/2019 cognitive radio principal

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Underlay and Interweave

CRs

Announcements! 1 "osted #ty"os corrected$% due &e'( 2)

at *"m+ro,ress re"orts due &e'( 2- at midni,.t

Introduction to co,nitive radiosUnderlay co,nitive radios

/"read s"ectrumIO

Interweave co,nitive radiosasic "remise

/"ectrum sensin,


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/carce !ireless/"ectrum

and E"ensive

$$$


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Co,nition RadioIntroduction

Co,nitive radios can su""ort new wireless usersin eistin, crowded s"ectrum !it.out de,radin, "erormance o eistin, users

Utili4e advanced communication and si,nal"rocessin, tec.ni5uesCou"led wit. novel s"ectrum allocation "olicies

ec.nolo,y couldRevolutioni4e t.e way s"ectrum is allocated worldwide+rovide su7icient 'andwidt. to su""ort .i,.er 5uality

and .i,.er data rate "roducts and services

. i i i


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!.at is a Co,nitiveRadio8

Co,nitive radios #CRs$ intelli,ently e"loitavaila'le side inormation a'out t.e

#a$C.annel conditions#'$Activity

#c$Code'oo9s

#d$ essa,es

t.er nodes wit. w.ic. t.ey s.are t.e s"ectru

i i di


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Co,nitive Radio+aradi,ms

Underlay Co,nitive radios constrained to cause minimal

intererence to nonco,nitive radios

InterweaveCo,nitive radios nd and e"loit s"ectral .oles

to avoid intererin, wit. nonco,nitive radios

Overlay Co,nitive radios over.ear and en.ance

nonco,nitive radio transmissions

Knowledgeand


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Underlay /ystems

Co,nitive radios determine t.e intererencet.eir transmission causes to nonco,nitivenodesransmit i intererence 'elow a ,iven t.res.old

.e intererence constraint may 'e met ;ia wide'and si,nallin, to maintain intererence

'elow t.e noise


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Underlay C.allen,es

easurement c.allen,eseasurin, intererence at "rimary receiver easurin, direction o "rimary node or

'eamsteerin,

+olicy c.allen,esUnderlays ty"ically coeist wit. licensed usersLicensed users "aid or t.eir s"ectrum

Licensed users don=t want underlays Insist on very strin,ent intererence constraints /everely limits underlay ca"a'ilities and a""lications


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Ultrawide'and Radio#U!$

Uses >(* ?.4 o @ree s"ectrum #underlay$

U! is an im"ulse radio: sends "ulses otens o "icoseconds#10B12$ to nanoseconds

#10B-$uty cycle o only a raction o a "ercent

A carrier is not necessarily needed

Uses a lot o 'andwidt. #?4$

i,. data rates% u" to *00 '"s% very low"ower

ulti"at. .i,.ly resolva'le: ,ood and 'ad


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DullB/"ace Learnin, in IO CRDetwor9s

+erormance o CRs su7ers rom intererence constraint

In IO systems% secondary users can utili4e t.e null s"ace o t.e "rimary user=s c.annel wit.out intererin, C.allen,e is or CR to learn and t.en transmit wit.in t.e null s"ace o t.e 12 matri !e develo" 'lind nullBs"ace learnin, al,orit.ms 'ased on sim"le ener,y measurements wit. ast

conver,ence


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+ro'lem /tatement

Consider a sin,le "rimary user% User 1

O'ective: Learn null s"ace null#1$%

1 wit. minimal 'urden on t.e "rimary user

+ro"ose two sc.emes:

+assive "rimary user sc.eme: +rimay usero'livious to secondary system Active "rimary user sc.eme: inimal

coo"eration #no .ands.a9e orsync.roni4ation$( &aster learnin, time(


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/ystem /etu"

Dote: q(t) can 'e any monotonic unction o y 2(t)

Ener,y is easily measura'le at secondary transmitter


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Learnin, +rocess

.e /U=s learns t.e null s"ace o 12 'y insertin, a

series o in"ut sym'ols and measurin,

q(n)=f k#

$(

.e only inormation t.at can 'e etracted is

w.et.er q(n) increases or decreases

Is t.is su7icient to learn t.e null s"ace o 128

)}(~W{ 21 n xk −


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FesGThe problem is equivalent to a blind Jacobi EVD decomposition

The theorem ensures that Jacobi can be carried out by a blind 2D

optimization in which every local minimum is a global minimum.


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an oun earc Accuracy

ore relaed constraints on +U intererence leads to 'etter"erormance o t.e secondary user

.is tec.ni5ue re5uires no coo"eration wit. +U

I +U transmits its intererence "lus noise "ower% can s"eed u"conver,ence si,nicantly

.e "ro"osed learnin, tec.ni5ue also "rovides a novel s"atialdivision multi"le access mec.anism


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+erormance


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/ummary o Underlay IO/ystems

DullBs"ace learnin, in IO systems

can 'e e"loited or co,nitive radios

lind Haco'i tec.ni5ues "rovide ast

conver,ence wit. very limited

inormation

.ese ideas may also 'e a""lied to w.ite

s"ace radios


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Interweave /ystems: Avoid interference

easurements indicate t.at even crowded s"ectrumis not used across all time% s"ace% and re5uenciesOri,inal motivation or @co,nitive radios #itola=00$

.ese .oles can 'e used or communication Interweave CRs "eriodically monitor s"ectrum or .olesole location must 'e a,reed u"on 'etween and Role is t.en used or o""ortunistic communication wit.

minimal intererence to nonco,nitive users

I t


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InterweaveC.allen,es

/"ectral .ole locations c.an,e dynamically Deed wide'and a,ile receivers wit. ast sensin,

Com"resses sensin, can "lay a role .ere/"ectrum must 'e sensed "eriodically and R must coordinate to nd common .oles

ard to ,uarantee 'andwidt.

etectin, and avoidin, active users is c.allen,in,&adin, and s.adowin, cause alse .ole detectionRandom intererence can lead to alse active user

detection

+olicy c.allen,esLicensed users .ate interweave even more t.an underlay Interweave advocates must outmaneuver incum'ents

!.it /


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!.ite /"aceetection

!.ite s"ace detection can 'e done 'y a sin,lesensor or multi"le sensors

!it. multi"le sensors% detection can 'e distri'utedor done 'y a central usion center

Jnown tec.ni5ues or centrali4ed or distri'uteddetection can 'e a""lied


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etection Errors

issed detection o "rimaryuser activity causesintererence to "rimary users(

&alse detection o "rimaryuser activity #alse alarm$misses s"ectrumo""ortunities

.ere is ty"ically a tradeo7'etween t.ese two#conservative vs( a,,ressive$


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/ummary !ireless s"ectrum is scarce

Intererence constraints .ave .indered t.e"erormance o underlay systemsE"loitin, t.e s"atial dimension o"ens new

o""ortunities

Interweave CRs nd and e"loit ree s"ectrum:+rimary users concerned a'out intererence

uc. room or innovation

+.iloso".ical c.an,es in system desi,n ands"ectral allocation "olicy also re5uired


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+resentation

@A /urvey o /"ectrum /ensin, Al,orit.ms or Co,nitive Radio

A""lications

Aut.ors: % Fuce9 and ( Arslan

+resented 'y Cey.un A9cay

Documents

cognitive radio principal