14.IJAEST-Vol-No-7-Issue-No-2-Spectrum-Utilization-by-Using-Cognitive-Radio-Technology-258-263 by ISERP ISERP

Er. Vishakha Sood* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 2, 258 - 263

Spectrum Utilization by Using Cognitive Radio Technology ECE department Student RIEIT Railmajra Punjab, India vishakha.sood@rediffmail.com

Keywords: - cognitive radio (CR), Power spectral density (PSD), Primary user (PU), secondary user (SU).

INTRODUCTION

ECE department Faculty RIEIT Railmajra Punjab, India singh.manwinder@gmail.com

Abstract: Cognitive radio networks can be designed to manage the radio spectrum more efficiently by utilizing the spectrum holes in primary userâ&#x20AC;&#x2122;s licensed frequency bands. The currently available unlicensed spectrum is reaching its limit and various demands for applications and data rates in wireless communications requires additional spectrum which imposes limits on spectrum access. These requirements demand for efficient and intelligent use of spectrum. The system model and the problem of the optimum spectrum allocation in cognitive radios are introduced and formulated. There are very few experimental simulation techniques present regarding cognitive radios, thus we intend to come out with a simpler and efficient simulating technique. Our approach was to take the decisions on the basis of power spectral density of the channel which can be used cognitively to find out the available gaps those can be assigned to new incoming users thus improving the overall channel throughput.

Er. Manwinder Singh

Er. Vishakha Sood

As we now that spectrum is not scarce but it is not used properly or efficiently. It is shown in figure-1 that the total available spectrum is 0-6 GHZ but only up to 2 GHZ is used properly.

Most of todayâ&#x20AC;&#x2122;s radio systems are not aware of their radio spectrum environment and operate in a specific frequency band using a specific spectrum access system. Investigations of spectrum utilization indicate that not all the spectrum is used in space (geographic location) or time. A radio, therefore, that can sense and understand its local radio spectrum environment, to identify temporarily vacant spectrum and use it, has the potential to provide higher bandwidth services, increase spectrum efficiency and minimize the need for centralized spectrum management. This could be achieved by a radio that can make autonomous (and rapid) decisions about how it accesses spectrum. Cognitive radios have the potential to do this. Cognitive radios have the potential to jump in and out of unused spectrum gaps to increase spectrum efficiency and provide wideband services. In some locations and/or at some times of the day, 70 percent of the allocated spectrum may be sitting idle. The FCC has recently recommended that significantly greater spectral efficiency could be realized by deploying wireless devices that can coexist with the licensed users [1].

Figure-1.Measurement of 0~6 GHz spectrum Utilization at Berkeley Wireless Research Center [1]

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Figure-2.Spectrum measurement across 900 kHz-1 GHz band (Lawrence, USA) [2]

The figure -2 shows the use of cognitive radio for filling the spectral holes [2]. This paper is organized as follows: in section II we will give complete description of PSD. In section III we will explain the current frequency allocation plan in India .In section IV we will explain the system performance with the block diagram .In section V we will explain the simulation results with graphs. Section VI will conclude the theory.

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Er. Vishakha Sood* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 2, 258 - 263

POWER SPECTRAL DENSITY DETECTION

The power spectral density (PSD) is intended for continuous spectra [2]-[6]. The integral of the PSD over a given frequency band computes the average power in the signal over that frequency band. In contrast to the meansquared spectrum, the peaks in these spectra do not reflect the power at a given frequency. Syntax Hpsd=dspdata.psd(Data) Hpsd=dspdata.psd(Data,Frequencies Hpsd=dspdata.psd(...,'Fs',Fs) Hpsd=dspdata.psd(...,'SpectrumType',SpectrumTyp) Hpsd=dspdata.psd(...,'CenterDC',flag) Hpsd = dspdata.psd (Data, Frequencies) uses the power spectral density estimation data contained in Data and Frequencies vectors. Hpsd = dspdata.psd(...,'Fs',Fs) uses the sampling frequency Fs. Specifying Fs uses a default set of linear frequencies (in Hz) based on Fs and sets Normalized Frequency to false.

India’s National Frequency Allocation plan:The National Frequency Allocation Plan (NFAP) forms the basis for development and manufacturing of wireless equipment and spectrum utilization in the country. Frequency bands allocated to various types of radio services in India are as follows. 1) 0-87.5 MHz is used for marine and aeronautical navigation, short and medium wave radio, amateur (ham) radio and cordless phones. 2) 87.5-108 is used for FM radio broadcasts 3) 109-173 MHZ Used for Satellite communication, aeronautical navigation and outdoor broadcast vans 4) 174-230 MHz not allocated. 5) 230-450 MHZ Used for Satellite communication, aeronautical navigation and outdoor broadcast vans 6) 450- 585 is Not allocated. 7) 585-698 is used for TV broadcast 8) 698-806 not allocated. 9) 806-960 is used by GSM and CDMA mobile services. 10) 960-1710 is used for Aeronautical and space communication. 11) 1710- 1930 is used for GSM mobile services. 12) 1930-2010 is used by defense forces. 13) 2010-2025is not allocated. 14) 2025-2110is used for Satellite and space communications. 15) 2110-2170 is not allocated. 16) 2170-2300 is used for Satellite and space communications. 17) 2300-2400 is not allocated. 18) 2400- 2483.5 Used for Wi-Fi and Bluetooth short range services. 19) 2483.5-3300 Space communications. 20) 3300-3600 not allocated. 21) 3600-10000 Space research, radio navigation. 22) 10000 are used for satellite downlink for broadcast and DTH services.

Hpsd = dspdata.psd (...,'SpectrumType', Spectr mType) uses the SpectrumType string to specify the interval over which the power spectral density was calculated. For data that ranges from [0 pi) or [0 pi], set the SpectrumType to onesided; for data that ranges from [0 2pi), set the SpectrumType to two-sided.

communication, broadcasting, radio navigation, mobile satellite service, aeronautical satellite services, defense communication etc.

II.

Hpsd = dspdata.psd (...,'CenterDC', flag) uses the value of flag to indicate whether the zero-frequency (DC) component is centered. If flag is true, it indicates that the DC component is in the center of the two-sided spectrum. Set the flag to false if the DC component is on the left edge of the spectrum. The periodogram for a sequence[x1…….xN] is given by the formula

)

|∑

(

(1)

The periodogram will be

S (f) =

|∑

⁄

(2)

Where is in radians/sample. Frequency is in Hz, Fs are the sampling frequency. Periodogram is the PSD estimate of the signal defined by sequence [x1 ….xN]. III.

CURRENT INDIA

SPECTRUM

ALLOCATION

The word spectrum refers to a collection of various types of electromagnetic radiations of different wavelengths. Spectrum or airwaves are the radio frequencies on which all communication signals travel. In India the radio frequencies are being used for different types of services like space communication, mobile ISSN: 2230-7818

As is clear from the above plan that spectrum is not used fully that’s why we are making use of cognitive radio technology to make best from available[7],[12]. The current fixed frequency band allocation scheme cannot accommodate these requirements of increasing number of high data rate devices. The challenges for managing the radio spectrums in India are mentioned in [11].The spectrum utilization in the frequency bands between 30 MHz to 3GHz averaged over six locations was studied by the Shared Spectrum Company [12],[15].The report shows that the maximum utilization is approximately 25% in TV

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Er. Vishakha Sood* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 2, 258 - 263

IV.

SYSTEM PERFORMANCE

We’ve taken 5 carrier frequencies Fc1 = 1000, Fc2 = 2000, Fc3 = 3000, Fc4=4000 & Fc5 = 5000. Keeping the user message/data signal frequency as 1000. x = cos (2*pi*1000*t)//every user’s base band data signal. Once user 1’s data arrive, it is modulated at the first carrier Fc1, similarly as the 2nd user’s data arrives, it is modulated at the 2nd carrier Fc2, so on till fifth user is assigned the Fc5 band. If any user’s data is not present his frequency band remains empty which is called a Spectral Hole [16]-[20]. Figure-3 shows the block diagram representation for calculation of PSD.

arrives he is assigned the first spectral hole. If all the slots are reserved ask user to empty a particular slot. The slot that is to be fired is asked and made empty accordingly to user. Whether to add or not the Noise and in how much amount is asked to user. The output is plotted. The attenuation and %age of attenuation is asked to be added and plotted accordingly [2], [7]-[9]. V.

SIMULATION RESULTS

We’ve designed our system to have 5 different frequency channels and each User is assigned a particular frequency band. Once we run our program it’ll ask to add a User and assign it a particular band in ascending order.

channel and the average usage is only about 5.2% .This finding suggests that spectrum scarcity as perceived today is mostly due to the inefficient fixed frequency allocation rather than physical shortage of radio spectrum.

Figure-4 command window showing entry of users

Here we haven’t entered User 2, & 4, thus their respective bands are still un- allocated. We can see them below in the power spectral density graph of our carrier signal.

Figure 3: Block diagram for PSD calculation

Let us explain it by taking example:

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

Figure-5.PSD graph

This figure shows the PSD graph of the values entered above. As is clear from the figure that we have allocated only users 1, 3 and 5; their respective bands can be seen here.

End

Firstly we will initialize the 5 Carrier Frequency Bands (Fc) for all Users, Message Frequency (as taken 1000 here) and the Sampling Frequency (Fs). When any user’s data arrives it is modulated at its carrier frequency, if any user’s data is not present then his frequency band remains empty. Then all the modulated signals are added to create a carrier signal. The Power Spectral Density is estimated by using periodogram method. All the PU is assigned with spectrum according to their data requirements. When a new User (SU) ISSN: 2230-7818

Figure-6 command window

Here the secondary user’s entry is asked and secondary user is entered at the free space which is not occupied by PU.

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Er. Vishakha Sood* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 2, 258 - 263

Here is the PSD of figure-6.We can see from fig-5 that slot 2 was not assigned to PU so it is allocated here to the SU.

Figure-7 PSD graph

Figure-10 command window showing attenuation

Here we can see the attenuation operation. The %age by which the signal is to be attenuated is added here.

Figure-8 command window showing noise addition

Here the noise adds operation is performed. The SNR is asked to be added. As here 50 dB is added. Figure-11 PSD plot

Here we can see the effect of adding attenuation to the signal. As the level of the signal depends upon the %age of attenuation added.

Figure-9 PSD graph

Here the added noise figure is plotted. We can easily distinguish between the original signal and noise added signal.

Figure-12 command window

Here we can see that until all the slots are not filled the program will re -run and ask for adding the secondary users. ISSN: 2230-7818

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Er. Vishakha Sood* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 2, 258 - 263

Figure-13 PSD graph

Figure-16 command window showing slot fired operation

As we can see from fig-6 that slot 4 was un-occupied so it is allocated here to SU.

Here the slot fire operation is explained. The slot which is required to fire by user is entered and made vacant accordingly.

Figure-14 command window showing all slots filled

Here again the secondary userâ&#x20AC;&#x2122;s entry is asked. If all slots are reserved then the program will not re run.

Figure-15 PSD plot

Here is the PSD of above entered command. As all slots are occupied so no user canâ&#x20AC;&#x2122;t be entered now. It is required to first vacate any slot for further entry.

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Figure-17 PSD Plot

As we can see from above command that slot 1 is fired so it is free for next data or for next user to be used. VI. CONCLUSION In this paper we have taken the problem of in-efficient spectrum utilization i.e. shown by FCC that the spectrum is not scarce but it is not used efficiently and we have tried to maximize the utilization. We have made use of PSD and tried to vary some parameters so that the portion of the spectrum which is not used by PU at a time can be allocated to SUs. Firstly we have given priority to PUs and accordingly the left sots are allocated to SUs. Then we have fired the slots. Then we have added noise and attenuation to see their effects on the availability of the signal. As we have obtained best results but the results can vary with the previous researches due to variations in parameters.

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Er. Vishakha Sood* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 2, 258 - 263

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