A Novel Approach to Fairly Grant Channel Access to Secondary Users in Cognitive Radio Networks Using Scheduling

International Journal of Scientific Research and Engineering Development-– Volume 3 Issue 4, July –Aug 2020
Available at www.ijsred.com
ISSN : 2581-7175 ©IJSRED:All Rights are Reserved Page 81
A Novel Approach to Fairly Grant Channel
Access to Secondary Users in Cognitive Radio
Networks using Scheduling
Balakrishnan K.*, Tamilarasan S.**
*Department of Information Science and Engineering, BrindavanCollege of Engineering, Bangalore
Email: geminibala88@gmail.com
** Department of Computer Science and Engineering, Brindavan College of Engineering, Bangalore
Email: stamilarasan74@rediffmail.com
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Abstract:
A Cognitive Radio Network (CRN) is one where Primary users have the need of using the range. The Secondary users are controlled
to ensure that they don't meddle in the channel, when a Primaryuser is dynamic. Be that as it may, when a Primary user is idle, the
Secondary users are permitted access to the range. In any case, there doesn't exist an approach to facilitate between the different
Secondary users that get to the range in an occasion of the nonattendance of the Primary users. In this paper, we propose a Channel
Access Scheduling plan, which is a concentrated way of arranging entrance to the channels for the different Secondary users that are
a piece of the CRN. This proposal revolves around a Scheduling Manager (SM) that arranges the channel access between the
Secondary users. The SM considers metrics like QOS and holding up time in the line to choose which Secondary gets to the channel.
The recreation results show that the proposition improves throughput of the framework and furthermore improves reasonableness in
channel assignment.
Keywords —Cognitive Radio Network, Channel Access Scheduling, Scheduling Manager,
Throughput.
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I. Introduction
Cognitive Radio Networks (CRNs) are a propelling
innovation in remote interchanges used to improve the
channel usage of constrained unearthly assets, particularly as
the interest for remote recurrence has quickly expanded as of
late. In CRNs, unlicensed auxiliary systems or the Secondary
Users (SUs) are possibly allowed to get to the channel just
when they don't meddle with the activity of authorized
essential systems or the Primary Users (PUs). This entrance
happens through a product characterized radio that looks to
utilize an inert channel. What's more, as of late, the
heterogeneity of both channel get to strategy and range
request in SUs is turning into another pressing issue on the
grounds that the impedance prompted by the channel use of
SUs may altogether hamper the throughput execution of
different SUs in subjective systems.
The Federal Communications Commission (FCC)
has approved the opening of the unused spectrum in TV bands
to unlicensed devices. The possibility of spectrum availability
subsequently has triggered new standardization activities
within the IEEE working groups for the networks capable for
operating in TV white space bands. For example, IEEE 802.22
WRAN has appeared in an attempt to develop physical and
MAC layer specifications for WRAN operation in less
populated rural areas. IEEE 802.11af standard was developed
by modifying the conventional IEEE 802.11 standard to
operate in this range. And IEEE 802.19.1 standard is at early
stage of development for potential coexistence between
heterogeneous CRNs.
As the assortment of these intellectual systems
expands, it is normal that different SUs with heterogeneous
qualities may coincide in same region. Most past examination
has concentrated on relieving the obstruction among PUs and
SUs [1] [2]. In [3], [4], they proposed a priority based
scheduler to tackle the conjunction issue. In [3] there is a
proposal for a scheduler with just two distinct levels, where
the higher and lower priority levels related to PUs and SUs,
separately. At that point, in [4], PUs had pre-emptive need
over SUs, and the needs for SUs were additionally partitioned
into various need esteems.
In this paper, we consider the coexistence among
heterogeneous SUs with different maximum tolerable delay
requirement, depending on their service type (e.g., best-effort,
multi-media, interactive services, and so on). We then propose
RESEARCH ARTICLE OPEN ACCESS

a centralized approach to explicitly and dynamically
coordinate the channel accesses among SNs under the
assumption that SNs can exchange channel information and
the traffic delay requirement through a scheduling manager
(SM).
II.LiteratureSurvey
YahiaTachwali et al [10] proposes a methodology to
maximize spectrum utilization by maximizing the number of
channels used or number of SUs served, when each SU selects
only one channel. However, the drawback of this approach is
that it does not consider different requirements of SUs.
OzgurErgul et al [8] suggest a methodology to
minimize interference between SUs and interference caused to
PUs. This can be investigated jointly with power control. This
also minimizes interference in the network, which increases
performance and ensures minimum impact on PUs. But, the
approach does not necessarily ensure satisfaction of different
user QoS demands.
Minal S. Moon et al [5] have proposed an approach
for channel selection for data communication using energy
detection sensing technology. A new data called Preferable
Channel List has been introduced in the proposal. PCL has
been used for selection of channel in systems where the
receiver is dominant. The proposed system gives reasonable
throughput while keeping the delay at a minimum.
Indika A. M. Balapuwaduge, Lei Jiao, VicentPla [4] have
proposed a queue-based channel assembling strategy for
heterogeneous channel CRNs and analytical structure for
performance evaluation of such networks. They achieved
signiﬁcant reduction in forced terminations of ESU services.
This proposal is recommended if PUs are more active in a
CRN.
III. Problemdefinition
From the Literature survey it is very clear that the dynamic
channel allocation routine that uses priority as its basis does
not exist for a CRN. This becomes more difficult when there
is a network with nodes requiring heterogeneous services. In
such situations, it is possible that critical parameters like delay
may be ignored. Hence, a proposal is made in this paper for
providing a dynamic approach for allocating resources while
keeping priority scheduling as one of the core concepts for a
CRN.
As already mentioned, a CRN consists of two
categories of nodes or users namely Primary and Secondary.
These users have heterogeneous network and service
requirements. While it is the PU that have access to the
channels in the spectrum by default, it is the responsibility of
the SU Base Station (SU-BS) to allocate the unused channels
to the SUs. For this, the SU-BS uses a metric called Channel
Quality Indicator (CQI) that helps the SU-BS make a decision
on which of the secondary should get the unused channel.
This metric CQI is compared with another metric called
Signal-to-Interference-Noise-Ratio (SINR) to make this
decision.
The capability of the cognitive radio to have
knowledge of the spectrum and thereby detect opportunities of
unused channels is mainly because of the property of
spectrum sensing. This sensing is carried out by the base
stations of the secondary network. Spectrum sensing can
either be In-Band or Out-Band. Through Out-Band sensing,
the BS tries to find out if there are any spectrum opportunities.
The In-Band sensing is used to determine if there is any
primary user present that needs a channel in the spectrum.
IV. SystemModel
In this system, we consider a PU, multiple heterogeneous SUs,
and a SM over a single wireless channel. In cognitive
networks, SUs are regulated in order to prevent them from
accessing the channel if PUs are currently utilizing the
channel. The SM is responsible for coordinating the channel
access operations among heterogeneous SUs as well as
between a PU and SUs.
Fig.1 A coexistence scenario of PU and SUs.
In Fig. 1, a PU and multiple heterogeneous SUs exist, where
tn is the n-th sensing time by SUs, and Ts is sensing time
interval between successive sensing times. If the PU occupies
the channel at a specific time tn, then SUs sense the channel at
every Ts and report the channel condition information to the
SM. Upon the notice from SUs, the SM decides which frame
is to be transmitted based on the channel access scheduling
policy, as long as the PU is not currently occupying the
channel.
A detailed description of the possible coexistence cases
between a PN and multiple SNs is as follows:
• [Busy] As shown in Fig. 1(a), the first frame of the PU is
transmitted at the specific point t1. In this case, no SU
attempts to utilize the channel were made during transmission
of the PU between t1 and t3 in order to avoid the interference
with the PU.

International Journal of Scientific Research and Engineering Development
ISSN : 2581-7175 ©
• [Success] SUs are able to have opportunity to use the
channel between t3 and t4 since the channel is perceived as
idle at t3. In Fig. 1(b), the SUs successfully transmit their
frames because the transmission of SUs finishes before the PU
requires using the channel.
• [Collision] After the SUs sense the idle channel at t5, the
SUs attempt to gain access to the wireless channel and
transmit their frames. Unlike Fig. 1(b), the transmissions of
SUs last until the start of PU frame as shown in Fig. 1(c). As a
result, these two frames collide and fail to be transmitted,
leading to throughput degradation. Therefore, if the
transmission of a frame does not finish until the next interval,
the channel access scheduler in the SM should not allow such
a transmission to begin.
Fig. 2.The channel access scheduling operation in the SM.
Figure 2 illustrates the SM operation, which consists of N
queues and a scheduler, where N is the number of priority
values, and Qn is the queue with the n-th highest priority.
When an SU has a data frame to transmit, it sends a
transmission request message that includes the network
identity and the data transmission duration to the SM in order
to acquire the channel use permission. After the SM receives
the transmission request message from the SU, it pla
message in the corresponding queue according to the priority
value of the frame. When the channel becomes idle, the
scheduler in the SM chooses a frame from its queues, and then
sends the transmission permission message to the SU that sent
the request message for the selected frame. As such, the SM
must have appropriate channel scheduling policy to efficiently
utilize the channel and satisfy the quality of service (QoS)
requirements for the PU and SUs in the CRN.
A. Dynamic Channel Access Scheduling Scheme
The proposed scheduling scheme aims to select a set of data
frames from N queues such that the total sum of priorities is
maximized while ensuring that the transmission duration does
International Journal of Scientific Research and Engineering Development-– Volume 3 Issue
©IJSRED:All Rights are Reserved
ble to have opportunity to use the
channel between t3 and t4 since the channel is perceived as
idle at t3. In Fig. 1(b), the SUs successfully transmit their
frames because the transmission of SUs finishes before the PU
After the SUs sense the idle channel at t5, the
SUs attempt to gain access to the wireless channel and
transmit their frames. Unlike Fig. 1(b), the transmissions of
SUs last until the start of PU frame as shown in Fig. 1(c). As a
mes collide and fail to be transmitted,
leading to throughput degradation. Therefore, if the
transmission of a frame does not finish until the next interval,
the channel access scheduler in the SM should not allow such
The channel access scheduling operation in the SM.
Figure 2 illustrates the SM operation, which consists of N
queues and a scheduler, where N is the number of priority
th highest priority.
to transmit, it sends a
transmission request message that includes the network
identity and the data transmission duration to the SM in order
to acquire the channel use permission. After the SM receives
the transmission request message from the SU, it places the
message in the corresponding queue according to the priority
value of the frame. When the channel becomes idle, the
scheduler in the SM chooses a frame from its queues, and then
sends the transmission permission message to the SU that sent
est message for the selected frame. As such, the SM
must have appropriate channel scheduling policy to efficiently
utilize the channel and satisfy the quality of service (QoS)
cheme
The proposed scheduling scheme aims to select a set of data
frames from N queues such that the total sum of priorities is
maximized while ensuring that the transmission duration does
not exceed the remaining idle time. We formulate this
scheduling problem as a knapsack problem, i.e.,
𝑚𝑎𝑥 𝑃𝑛 . 𝑋𝑛
Subject to
𝑆𝑛 . 𝑋𝑛 ≤ 𝑇𝑠
Xn ϵ {0, 1}
where Pn is the priority value of the data frame at the head of
the n-th queue, Sn is the corresponding data transmission time,
Ts is the interval between two sensing times, and X
binary decision variable for the data frame in each queue.
Note that if Xn = 1, the frame in the n-th queue is selected.
In (1), we give a higher priority to a data frame that
has shorter maximum tolerable delay because such a frame is
more sensitive to transmission delays. For example, if a multi
media data frame fails to be transmitted within its maximum
tolerable delay, it cannot be used in practical terms and can be
regarded as lost. Therefore, the priority value of a data frame
in the n-th queue can be calculated as
𝑃 = 𝑑
wheredn is the maximum tolerable delay of the data frame at
the head in the n-th queue.
We also dynamically update the priorities of data
frames in order to mitigate the starvation problem. In (1), the
SM tends to select only the data frames with the highest
priories with the data frames having low priorities being rarely
selected. To solve this problem, we gradually increase the
priorities of data frames that are not selected at the head of the
queues as follows:
𝑃𝑛 ← 𝑃𝑛 + 𝑀𝑛 . 𝑎
whichMn is the number of waiting time slots in the head of the
n-th queue, and a is the increase of the priority value. As a
becomes larger, the data frames having a initially low priority
can acquire an opportunity to access the channel.
V. SimulationR
To evaluate performance of our proposed channel access
scheduling scheme, we conducted various simulations using
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Page 83
not exceed the remaining idle time. We formulate this
oblem as a knapsack problem, i.e.,
(1)
is the priority value of the data frame at the head of
is the corresponding data transmission time,
is the interval between two sensing times, and Xn is a
binary decision variable for the data frame in each queue.
th queue is selected.
In (1), we give a higher priority to a data frame that
has shorter maximum tolerable delay because such a frame is
more sensitive to transmission delays. For example, if a multi-
mitted within its maximum
tolerable delay, it cannot be used in practical terms and can be
regarded as lost. Therefore, the priority value of a data frame
(2)
is the maximum tolerable delay of the data frame at
We also dynamically update the priorities of data
frames in order to mitigate the starvation problem. In (1), the
SM tends to select only the data frames with the highest
ries with the data frames having low priorities being rarely
selected. To solve this problem, we gradually increase the
priorities of data frames that are not selected at the head of the
(3)
is the number of waiting time slots in the head of the
th queue, and a is the increase of the priority value. As a
becomes larger, the data frames having a initially low priority
can acquire an opportunity to access the channel.
Results
performance of our proposed channel access
scheduling scheme, we conducted various simulations using

International Journal of Scientific Research and Engineering Development
ISSN : 2581-7175 ©
MATLAB. During the simulations, the data transmission
times were randomly selected to be between 5 ms and 15 ms;
we also assume that the maximum tolerable delays of SUs are
100, 80, 60, 40, 30, and 20 ms. Again, data frames that are not
successfully transmitted within its maxim tolerable delay are
regarded to be lost.
Figure 3 shows the simulation results of the average
delay with respect to the priority values when the idle time
period is 50 ms. Note that p1 is lowest priority value, and p5
is highest priority value with the smallest maximum tolerable
delay time.
The average delays for First in First out (FIFO) are almost the
same regardless of the priority value. In terms of the priority
queue (PQ) and the proposed scheme with a=0, the data
frames with low priorities have extremely long average delay
time because the transmissions of data frames with higher
priority take precedence over those with lower priority. It is
seen that when a = 6, the maximum tolerable delay is lower
than the requirement of the tolerable delay.
Figure 4 depicts the network throughput results with
respect the idle time period. The throughput performance is
seen to increase as the idle time period is increased from 30
ms to 50ms. The reason is that when the available channel
access time is increased, more frames belonging to SUs are
successfully delivered. Since the FIFO and PQ transmit data
frames without consideration of the idle time constraint in (1),
they show a low throughput performance. Note that the
throughput for the proposed scheme with a=0 is also low since
the frames with lower priority have extremely long delay time.
However, our proposed scheduling scheme
outperforms the conventional schemes, with an overall
improvement in throughput performance of about 15%.
Fig. 3 The average delay time for multiple SNs with different maximum
tolerable delay.
International Journal of Scientific Research and Engineering Development-– Volume 3 Issue
©IJSRED:All Rights are Reserved
MATLAB. During the simulations, the data transmission
times were randomly selected to be between 5 ms and 15 ms;
m tolerable delays of SUs are
100, 80, 60, 40, 30, and 20 ms. Again, data frames that are not
successfully transmitted within its maxim tolerable delay are
Figure 3 shows the simulation results of the average
priority values when the idle time
period is 50 ms. Note that p1 is lowest priority value, and p5
is highest priority value with the smallest maximum tolerable
The average delays for First in First out (FIFO) are almost the
he priority value. In terms of the priority
queue (PQ) and the proposed scheme with a=0, the data
frames with low priorities have extremely long average delay
time because the transmissions of data frames with higher
h lower priority. It is
seen that when a = 6, the maximum tolerable delay is lower
Figure 4 depicts the network throughput results with
respect the idle time period. The throughput performance is
e as the idle time period is increased from 30
ms to 50ms. The reason is that when the available channel
access time is increased, more frames belonging to SUs are
successfully delivered. Since the FIFO and PQ transmit data
the idle time constraint in (1),
they show a low throughput performance. Note that the
throughput for the proposed scheme with a=0 is also low since
the frames with lower priority have extremely long delay time.
However, our proposed scheduling scheme
erforms the conventional schemes, with an overall
improvement in throughput performance of about 15%.
Fig. 3 The average delay time for multiple SNs with different maximum
Fig. 4. The network throughput with respect to the idle time period
VI. Conclusion
We have studies the channel access scheduling issues when
multiple heterogeneous SNs coexist and share a single
channel. The proposed channel access scheme was formulated
as a knapsack problem to maximize the sum of priorities of
data frames under the constraint of limited transmission time.
Specifically, the priorities of data frames in the queue were
dynamically adjusted according to the wait time in the head of
the queues in order to mitigate the starvation problem in
priority scheduling. As a result, through various simulations,
we showed that our proposed scheduling scheme can meet the
requirements for maximum tolerable delay while achieving a
high throughput performance.
References
[1] Y. Li, and A. Nosratinia, “Hybrid Opportunistic Scheduling in Cognitive
Radio Networks,” in Proc. of the Wireless Communications, IEEE
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[4] P. Zhu, J. Li, and X. Wang, “Scheduling Model for Cognitive Radio,” in
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Volume 3 Issue 4, July –Aug 2020
www.ijsred.com
Page 84
The network throughput with respect to the idle time period
Conclusion
channel access scheduling issues when
multiple heterogeneous SNs coexist and share a single
channel. The proposed channel access scheme was formulated
k problem to maximize the sum of priorities of
data frames under the constraint of limited transmission time.
Specifically, the priorities of data frames in the queue were
dynamically adjusted according to the wait time in the head of
o mitigate the starvation problem in
priority scheduling. As a result, through various simulations,
we showed that our proposed scheduling scheme can meet the
requirements for maximum tolerable delay while achieving a
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