o 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 This represents a paradigm shift in technology!

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

In some locations or some times of the day, 70 percent of the allocated spectrum may be sitting idle. New bandwidth-intensive wireless services are being offered.

Unlicensed users constrained to a few overloaded bands Increasing number of users.

This growth requires more spectral bandwidth to satisfy the demand.

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

– ‘Bandwidth Harvesting’ It is a

software-designed radio

with cognitive software.

CR can

sense

the environment.

CR

adapts

its way of communication to minimize the caused interference.

CR coexists with the primary user (using the same frequency band) in two ways:

Concurrent

and

Opportunistic

.

S 1 S 2 B S 1 B S 2 Figure: A four-nodes wireless sensor network scenario .

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

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

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

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

CR prototypes to emerge within the next five years.

Some devices are already in use like WLANs

o o

Dynamic Spectrum Access ( DSA ) 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 end disp('all user slots in use. try again later,');

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 Band Un-allocated Bands / Spectrum Holes

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

o o o o

Mobile multimedia downloads which require moderate data rates Emergency communications services that require a moderate data rate and localized coverage (for example, video transmission from firemen’s’ helmets); Broadband wireless networking (for example, using nomadic laptops), which needs high data rates, but where users may be satisfied with localized “hot spot” services; Multimedia wireless networking services (e.g. audio/video distribution within homes) requiring high data rates.

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