Noise uncertainty effect on multi-channel cognitive radio networks

International Journal of Electrical and Computer Engineering (IJECE)
Vol. 10, No. 5, October 2020, pp. 4818~4823
ISSN: 2088-8708, DOI: 10.11591/ijece.v10i5.pp4818-4823  4818
Journal homepage: http://ijece.iaescore.com/index.php/IJECE
Noise uncertainty effect on multi-channel cognitive
radio networks
Amira Osama1
, Heba A. Tag El-Dien2
, Ahmad A. Aziz El-Banna3
, Adly S. Tag El-Dien4
1
Department of Electrical and Computer Engineering, High Institutes for Engineering and Technology Al-obour, Egypt
2,3,4
Faculty of Engineering at Shoubra, Benha University, Egypt
Article Info ABSTRACT
Article history:
Received Oct 28, 2019
Revised Mar 11, 2020
Accepted Mar 30, 2020
Achieving high throughput is the most important goal of cognitive radio
networks. The main process in cognitive radio is spectrum sensing that
targets getting vacant channels. There are many sensing methods like
matched filter, feature detection, interference temperature and energy
detection which is employed in the proposed system; however, energy
detection suffers from noise uncertainty. In this paper a study of throughput
under noise fluctuation effect is introduced. The work in this paper proposes
multi-channel system; the overall multi-channel throughput is studied under
noise fluctuation effect. In addition, the proficiency of the network has
been examined under different number of channels and sensing time with
noise uncertainty.
Keywords:
Cognitive radio
Multi-channel
Noise uncertainty
Throughput
Copyright © 2020 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Amira Osama,
Department of Electrical and Computer Engineering,
High Institutes for Engineering and Technology Al-obour,
21 Cairo - Belbeis Desert Rd, Kaliobeya, Egypt.
Email: amiraosama111@gmail.com, amira.osama@oi.edu.eg
1. INTRODUCTION
Cognitive radio (CR) using spectrum sensing technique can be used to solve the issues of spectrum
underutilization [1-3]. In cognitive radio field the secondary user (SU) detect the primary user bands and
depends on this decision it selects the spectrum for its communication [4-6].The CR system could be single
channel or Multi-channel, choosing the system according to needs, because each system has benefits and
drawbacks. In CR system, the secondary user have to detect the vacant channel [7-10]. When a vacant
channel is detected, the secondary system will access that channel. However, spectrum sensing as an urgent
issue in CR, demands the secondary user to powerfully and successfully sense the existence of primary
signal [11-13]. Spectrum management is the core function in CR; contains various processes such as
spectrum sensing (SS), spectrum decision and spectrum handoff. SS is one of the most important advantages
of CR sensors network from old wireless sensor networks (WSNs). It overtakes few opticals like low SNR
for primary users, time dispersion, channel fading, and noise uncertainty [14-16].
Maximum throughput of the network has been studied for several numbers of optimal CR users.
Ahead of the issue of threshold mismatch of energy detectors with noise power uncertainty, a cooperative
spectrum sensing method with dynamic dual threshold is expressed in [17]. In [18] the optimal sensing
technique has been offered maximizing channel throughput. The offered optimal cooperative spectrum
sensing (CSS) settings for wide-band sensing channels is investigated and determined specifically with few
simple however dependable techniques. In [19] a new spectrum sensing adaptive algorithm considering noise
uncertainty has been proposed. In [20] the researchers studied noise uncertainty effect and fading on
the detection performance. In [21] researchers offered an evidence-theory based fusion rule for cooperative
energy detection in existance of noise power uncertainty.

Int J Elec & Comp Eng ISSN: 2088-8708 
Noise uncertainty effect on multi-channel cognitive radio networks (Amira Osama)
4819
Authors in [22] introduce a modified two-stage detection technique that relay on energy detection
under noise uncertainty. Researchers in [23] examined the act of spectrum sensing, they proposed that
the throughput reaches maximum at optimal sensing time. To certify how processes of primary user is not
disturbed, it has to keep the spectrum-sensing capability to get vacant channel when SU needs it.
Therefore, the proficiency of sensing the existence of primary signals remains important. Spectrum sensing
contains several methods (e.g. Matched filter, energy detection, feature detection, interference temperature).
In [24] authors studied and analyzed the proficiency of energy detector spectrum sensing method with
parameters affecting its performance on Nakagami-m fading channels under noise uncertainty and without.
Authors in [25] proposed a different system of two stages spectrum sensing, Adaptive two-stage spectrum
sensing (ATSS) , with noise uncertainty effect ATSS is a modification of a predictable two stage spectrum
sensing when the decision threshold of each stage is adapted on the distance, expected noise variance and
concluded noise uncertainty range. Noise uncertainty affect the performance of multi-channel is studied with
different number of channel and decides which best number ti get high throughput.
2. RESEARCH METHOD
This paper will introduce multi-channel system which has several channels that studies how noise
uncertainity affects the system performance to get the best scenario. Our proposed system here consists of
muli-channel (as each SU stands for one channel in proposed system) Spectrum sensing performance has
been offered to get best number of CR users [23], sensing time, Throughput R under noise fluctuation effect.
The received signal for every CR is sampled at sampling frequency fs.
As shown in Figure 1, every cognitive frame consists of spectrum sensing time (t) and data
transmission time (T-t), where T is the total frame time. Consider that the distribution function for noise can
be summarized in an interval [(1 + 𝜌)−1
𝜎𝑣𝑖
2
, (1 + 𝜌)𝜎𝑣𝑖
2
], where 𝜎𝑣𝑖
2
noise variance for 𝑖𝑡ℎ channel and 𝜌
is a parameter that quantizies the level of the uncertainity.Assuming K is the number of samples existing
during t .Therefore the number of samples, K=t.fs [23, 25]. The probability of detection and probability of
false alarm for multi-channel system under noise uncertainty effect can be written as
𝑃𝑓 = argmax
𝜎 𝑣𝑖
2∈[(1+𝜌)−1 𝜎 𝑣𝑖
2,(1+𝜌)𝜎 𝑣𝑖
2]
1
2
𝑒𝑟𝑓𝑐 (
1
√2
(
𝜆
𝜎 𝑣𝑖
2 − 1) √ 𝑡. 𝑓𝑠) (1)
𝑃𝑑 = argmax
𝜎 𝑣𝑖
2∈[(1+𝜌)−1 𝜎 𝑣𝑖
2,(1+𝜌)𝜎 𝑣𝑖
2]
1
2
𝑒𝑟𝑓𝑐 (
1
√2
(
𝜆
𝜎 𝑣𝑖
2 − Ɣ𝑖 − 1) √
𝑡.𝑓𝑠
2Ɣ 𝑖+1
) (2)
Solving (1), (2) under noise we will get
𝑃𝑓 =
1
2
𝑒𝑟𝑓𝑐(
1
√2
(
𝜆
(1+𝜌)𝜎 𝑣𝑖
2 − 1) √𝑘) (3)
𝑃𝑑 =
1
2
𝑒𝑟𝑓𝑐(
1
√2
(
𝜆
(1+𝜌)−1 𝜎 𝑣𝑖
2 − 𝛾𝑖 − 1) √
𝑘
2𝛾 𝑖 +1
) (4)
𝑃𝑓 =
1
2
𝑒𝑟𝑓𝑐(
1
√2
(
𝜆
𝛽𝜎 𝑣𝑖
2 − 1) √𝑘) (5)
𝑃𝑑 =
1
2
𝑒𝑟𝑓𝑐(
1
√2
(
𝛽𝜆
𝜎 𝑖
2 −
Ɣ 𝑖
𝛽
− 1)√
𝑘
2Ɣ 𝑖
𝛽
+1
) (6)
where 𝛽 = 1 + 𝜌,Ɣ𝑖 represents the SNR at the CR receiver for 𝑖𝑡ℎ channel and 𝜆 represents the decision
threshold. The throughput for the total false alarm probability in the absence of PU is [20, 23].
𝑅0 =
𝑇−𝜏
𝑇
𝐶𝑜(1 − 𝑄 𝑓𝑡)𝑃(𝐻𝑜) (7)
where 𝐶 𝑂 represents the throughput in the absence of PU. The throughput for the total missed detection
probability is
𝑅1 =
𝑇−𝜏
𝑇
𝐶1(1 − 𝑄 𝑑𝑡)𝑃(𝐻1) (8)

 ISSN: 2088-8708
Int J Elec & Comp Eng, Vol. 10, No. 5, October 2020 : 4818 - 4823
4820
where 𝐶1 represents the throughput in the existence of PU. From [20, 23] we get
𝑄 𝑓𝑡 = (1 − 𝑃𝑓)
𝑛
(9)
𝑄 𝑑𝑡 = (1 − 𝑄 𝑑) 𝑛
(10)
The total throughput R of the CR network can be expressed from previous disscussion as
𝑅 =
𝑇−𝑡
𝑇
(𝐶0 (1 − 𝑄 𝑓𝑜𝑝𝑡) 𝑃(𝐻0) + 𝐶1 (1 − 𝑄 𝑑𝑜𝑝𝑡)𝑃(𝐻1)) (11)
As R is a function of 𝑃𝑓and 𝑃𝑑,it will be affected by changing noise fluctuations. So the throughput
will be decreased when probability of false alarm increased or probability of detection decreased. Studying
n that represents the number of CRs in spectrum sensing. To compare this proposed system and [17] under
noise fluctuation equation of the system will be
𝑃𝑓 =
1
2
𝑒𝑟𝑓𝑐(𝑒𝑟𝑓𝑐−1(2𝑃𝑑)√2Ɣ𝑖 𝛽 + 1 +
𝑚
2
Ɣ𝑖 𝛽) (12)
Figure 1. Cognitive frame structure
3. RESULTS AND ANALYSIS
Now we are going to investigate the noise fluctuation on the ED ROC. As assumed above the noise
variance with uncertainty changed in the interval 𝜎𝑣𝑖
2
ϵ[𝜎𝑣𝑖
2
/𝜷, 𝜷𝜎𝑣𝑖
2
] where β >1 and changed from 1.259
to 1.585 [22]. BPSK modulation has been used by primary user to transmit its data with 3 MHz bandwidth.
The maximum time for which the secondary user uninformed of the primary action is selected as
Fs.T=3000[19]. The frame time of detection cycle is 100ms and target detection probability is 0.7.
We choose 𝑃(𝐻0) =0.8,𝑃(𝐻0) =0.2,𝐶 𝑂 =6.6582 and 𝐶 𝑂 =6.6137. Figure 2 shows the relation between
throughput and SNR at different values for noise fluctuations. We observe that when noise increasing by
30% and SNR=-12dB, the throughput R tends to zero, which means system at β =1.3 still working until SNR
reaches -12dB.
Figure 3 explains the throughput relation with number of CRs operating at t=2 ms. studying at
average number of CRs =5.At β=1, the throughput R=3.5.At β=1.05, the throughput R=2.5, which means by
increasing β by 5% throughput decreasing by 29%. At β=1.1, the throughput R=1.8, which means by
increasing by 10% throughput decreasing by 50%. At β=1.3, the throughput R=0.5, which means by
increasing by 30% throughput decreasing by 86%.
Figure 4 shows the relation between throughput and sensing time with different number of CRs.
(a) at n=15, we observe that when noise increasing by 30%, the throughput tends to zero. (b) at n=10,
we observe when increasing noise by 30%, the throughput decreasing by 70%. (c) at n=5, we observe when
increasing noise by 30%,the throughput decreasing by 60%.From that we can say at n=10 ,this is the best
number for CRs in this system under noise effect.
Figure 5 shows a comparison with [17] under noise fluctuation β=1.3 we obtained that at t=3ms,
P_f in reference system reaches to 0.55 which means it affected from noise with 30% but in our proposed
system that 𝑃𝑓 reaches 0.43 which means it affected from noise with 14%. This means that our proposed
system is better than reference system.

4821
Figure 2. Throughput vs SNR Figure 3. Throughput vs number of CRs
(a) (b)
(c)
Figure 4. The relation between throughput R and sensing time t,
(a) No. of CRs=15, (b) No. of CRs=10, (c) No. of CRs=5

 ISSN: 2088-8708
Int J Elec & Comp Eng, Vol. 10, No. 5, October 2020 : 4818 - 4823
4822
Figure 5. Sensing time vs Pf
4. CONCLUSION
The noise uncertainty effect on the performance of multi-channel is studied and we observe that,
in multi-channel, for our system it is good to work with 10 channels to achieve reasonable throughput in
relation with SNR or with sensing time by increasing noise up to 30%.From that we can say ,the proposed
system can reach reasonable throughput in single or multi-channel under noise that increase of 30% effect.
ACKNOWLEDGEMENTS
I would like to express my strong thanks to my supervisors for their guidance. I would like to
express my Love and thank to my family members.
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BIOGRAPHIES OF AUTHORS
Amira Osama, Teaching Assistant in Electrical and Communication Engineering, Universitad
High Institutes for Engineering and Technology Al-obour. She received her B.Eng., from Benha
university (Egypt) in 2013. She has been a Teaching Assistant High Institutes for Engineering
and Technology Al-obour since 2014. Her research interests include the field of network
communcation, Mobile systems ,WSN and IOT .
Heba A.Tag El Dien recieved B.Sc., M.Sc. and Ph.D. degrees from Shoubra Faculty of
Engineering, Benha University, Egypt, in 2007, 2013,and 2017 respectively. She is currently
assistant Professor in the electrical engineering department in Shoubra Faculty of Engineering.
She is a legal instructor in Cisco academy in Shoubra faculty of Engineering.
Ahmad A. Aziz El-Banna received a master’s degree from Benha University, Egypt, in 2011,
and a Ph.D. degree from the Egypt-Japan University of Science and Technology, Egypt, in 2014.
He served as a Visiting Researcher with Osaka University, Japan, from September 2013 to June
2014. He also completed a nine-month scholarship in embedded systems at Information
Technology Institute, Egypt, in 2008. Since June 2018, he has been Postdoctoral Research
Fellow with the Smart Sensing and Mobile Computing Laboratory, Shenzhen University, China.
He also holds the position of an Assistant Professor with the Electrical Engineering Department,
Faculty of Engineering at Shoubra, Benha University, Egypt. His research interests include
wireless communications, embedded systems, cooperative networking, MIMO, space-time
coding, IoT, WSN, underwater communication, and machine learning.
Adly S. Tag Eldien receivrd B.Sc.,M.Sc. and Ph.D. degrees Benha University, Egypt, in
1984,1989 and 1993 respectively.He is currently an associate professor in the department of
electrical engineering- Benha University.He was the X-head of Benha University network and
information center,his research interests include robotics,network and mobile communication.

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