o To Simulate Cognitive Radio System which is so effective that it can harvest more band-width in highly desired bands than is currently in use!

– More than in use by cellular systems– More than in use by unlicensed bands– More than in use by private mobile systems

o This represents a paradigm shift in technology!

o Today’s radio systems are not aware of their radio spectrum environment and operate in a specific frequency band.

o In some locations or some times of the day, 70 percent of the allocated spectrum may be sitting idle.

o New bandwidth-intensive wireless services are being offered.o Unlicensed users constrained to a few overloaded bandso Increasing number of users.o This growth requires more

spectral bandwidth to satisfy

the demand.

o Intelligent radio that uses spectrum licensed to other users when they aren't using it.

– ‘Bandwidth Harvesting’

o It is a software-designed radio with cognitive software.

o CR can sense the environment.

o CR adapts its way of communication to minimize the caused interference.

o CR coexists with the primary user (using the same frequency band) in two ways: Concurrent and Opportunistic.

S1

S2

BS1

BS2

Figure: A four-nodes wireless sensor network scenario.

o Full Cognitive Radios do not exist at the moment and are not likely to emerge until 2030.

o Requires practical implementation of fully flexible SDR technologies and the intelligence required to exploit them cognitively.

o But, true cognition and fully flexible radios may not be needed.

o Simple intelligence and basic reconfigurability at the physical layer could provide significant benefits over traditional types of radio.

o CR prototypes to emerge within the next five years.

o Some devices are already in use like WLANs

o Dynamic Spectrum Access ( DSA )

o To fill the spectral holes with secondary users’ data.

Fc1 = 1000; Fc2 = 2000; Fc3 = 3000; Fc4 = 4000; Fc5 = 5000; Fs = 12000;x1 = cos(2*pi*1000*t);

in_p = input('\nDo you want to enter first primary user Y/N: ','s'); if(in_p == 'Y' | in_p == 'y') y1 = ammod(x1,Fc1,Fs); end

:::

in_p = input('Do you want to enter fifth primary user Y/N: ','s'); if(in_p == 'Y' | in_p == 'y') y5 = ammod(x1,Fc5,Fs); end

y = y1 + y2 + y3 + y4 + y5;

Pxx = periodogram(y); Hpsd = dspdata.psd(Pxx,'Fs',Fs);

plot(Hpsd);

in_p = input('\nDo you want to enter a secondary user Y/N: ','s'); if(in_p == 'Y' | in_p == 'y') chek1 = Pxx(25)*10000; chek2 = Pxx(46)*10000; chek3 = Pxx(62)*10000;

Code Portion Skipped

:::

else disp('all user slots in use. try again

later,'); end

inp_t=input('do u want to empty a slot: ','s'); if(inp_t=='Y'|inp_t=='y') inp_t=input('which slot do u want to empty for ur entry: ','s'); switch(inp_t) case ('1') y1=0; disp('slot1 is fired'); y = y1 + y2 + y3 + y4 + y5;case('2') y2=0; disp('slot2 is fired'); y = y1 + y2 + y3 + y4 + y5; : : :

otherwise disp('invalid slot entered'); end

inp_t=input('do u want to add noise: ','s'); if(inp_t=='y'|inp_t=='Y') d = input('Enter the SNR in dB: '); figure Y = awgn(y,d); Pxx1 = periodogram(Y);

Code Portion Skipped

tm = 1-tem; Z = y.*tm; disp('attenuating'); grid on plot(Z);

Data assigned

Allocated / Used Spectrum BandUn-allocated Bands / Spectrum Holes

Left over Spectral GapsSpectral Gap Filled by modulating the new incoming user’s data over it

o Mobile multimedia downloads which require moderate data rates

o Emergency communications services that require a moderate data rate and localized coverage (for example, video transmission from firemen’s’ helmets);

o Broadband wireless networking (for example, using nomadic laptops), which needs high data rates, but where users may be satisfied with localized “hot spot” services;

o Multimedia wireless networking services (e.g. audio/video distribution within homes) requiring high data rates.

www.intcube.com/forum for requesting the complete project