ANALYSIS AND APPLICATION OF COGNITIVE RADIO ON 4G COMMUNICATIONS

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JoCES (2014) 1-8 © STM Journals 2014. All Rights Reserved Page 1
Journal of Communication Engineering & Systems
ISSN: 2249-8613 (online), ISSN: 2321-5151 (print)
Volume 4, Issue 3
www.stmjournals.com
Analysis and Application of Cognitive Radio on
4G Communications
Md. Nazrul Islam1, Mohammad Mamunur Rashid2, A.O.M. Asaduzzaman3,
Md. Shamim Hossain3, Md. Alamgir Hossain3*
1Department of CSE, Islamic University, Kushtia, Bangladesh
2School of Science and Technology, Bangladesh Open University, Gazipur, Bangladesh
3Department of CSE, Islamic University, Kushtia, Bangladesh
Abstract
Nowadays network services are available anywhere and anytime through the
advancement in wireless communication technology. Several technology and generation
are introduced for wireless communication such as 2.5G, 3G etc. But for faster and
reliable communication wireless generations are improved—4G technology is one of
them. 4G communication systems are being developed to solve the various problems
faced by the current communication systems (3G, 2.5G). 4G will be an intelligent
technology that will reduce the number of different technologies to a single global
standard. Cognitive Radio (CR) is the key enabling technology for next generation
networks. CR techniques provide the capability to use or share the spectrum in an
opportunistic manner. With the use of CR, 4G wireless networks will support global
roaming across multiple wireless and mobile networks. In this paper, analysis and
application of CR in 4G communications is reviewed. IEEE 802.22 networks are
cognitive technology-based networks which will enhance the performance of 4G
communication systems. IEEE 802.16h (WiMAX) provides extensions to support
unlicensed coexistence.
Keywords: Cognitive Radio (CR), WiMAX, Fourth Generation (4G), Federal
Communications Commission (FCC), Cognitive Engine (CE)
*Author for Correspondence E-mail: alamgirlovely@yahoo.com
INTRODUCTION
The demand for spectrum resources is
increasing day by day due to continuous
growth in the Wireless Communication
System. But there is a point to be noted that
the Radio spectrum is band limited. Cognitive
Radio (CR) is not only a radio technology; it
also includes a revolutionary change in how
the spectrum is regulated. CR and Fourth
Generation (4G) network are two
complementary developments that will
reframe the world of wireless
communications. 4G networks employing CRs
are a solution that revolutionizes the
telecommunication industry, significantly
changing the way we design our wireless
systems and services. Researchers expect
intelligent reconfigurable CR prototypes to
emerge within next five years. Some devices
available already have some elements of CR
e.g., WLAN, Military follower Jammers. In
spite of the increased complexity, future
networks should be easily maintainable and
there capabilities should be continuously
improved and upgraded by relying as little as
possible on human intervention.
In order to meet this demand, the networking
research community proposed a new paradigm
of networking—the cognitive network [1, 2].
It is generally agreed that cognitive networks
have the ability to think, learn and remember.
4G technology will offer many advances to the
wireless market, including downlink data rates
over 100 megabits per second (Mbps), low
latency, very efficient spectrum use and low
cost implementations. With flexible network
connections, efficient use of spectrum and
impressive user applications, 4G will offer
what consumers want [3].

Analysis and Application of Cognitive Radio Islam et al.
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Fig. 1: Evolution of Mobile Cellular Network (Adachi F. Ref. [4]).
Evolution of wireless generations is shown in
Figure 1.
COGNITIVE RADIO TECHNOLOGY
Today, there are several existing definitions of
CR and Cognitive Radio Networks. The most
important ones are the definitions provided by
Federal Communications Commission (FCC)
in the USA (2005), National
Telecommunications and Information
Administration (NTIA, 2005), International
Telecommunications Union (2005), IEEE
1900.1 WG. Perhaps the best definition is the
one provided by Haykin [5]:
“Cognitive Radio is an intelligent wireless
communication system that is aware of its
surrounding environment (i.e., outside world),
and uses the methodology of understanding-
by-building to learn from the environment and
adapt its internal states to statistical
variations in the incoming RF stimuli by
making corresponding changes in certain
operating parameters (e.g., transmit power,
carrier frequency and modulation strategy) in
real-time, with two primary objectives in
mind: highly reliable communications
whenever and wherever needed; and efficient
utilization of the radio spectrum”.
CR technology aims at making use of the
network resources currently used in wireless
communication systems more efficiently. CR
allows opportunistic use of the licensed
spectrum band by an unlicensed user with
minimum allowable interference to the
licensed user, and without compromising on
the desired quality of service required by the
unlicensed user. Hence, CRs must carry out
spectrum sensing to identify white spaces or
spectrum holes which are bands of frequencies
assigned to primary users, but, these bands are
not being utilized by those users at a particular
time and specific geographic location, [6] as
shown in Figure 2.
The CR Technology Characteristics
Flexibility and Agility
This is the ability to change the waveform and
other radio operational parameters while on
the move.
Sensing
This is the ability to observe and measure the
state of the radio environment, including
spectral occupancy. For the device to change
its operation based on the current knowledge
of the radio environment, sensing is very
necessary.
Learning and Adaptability
This is the ability to analyze sensory input, to
recognize patterns, and modify internal
operational behavior based on the analysis of
new situation. With these characteristic
features, CR has the capability to sense the
spectrum and determine vacant band [7].

Journal of Communication Engineering & Systems
Volume 4, Issue 3
ISSN: 2249-8613 (online), ISSN: 2321-5151 (print)
JoCES (2014) 1-8 © STM Journals 2014. All Rights Reserved Page 3
Fig. 2: Frequency Spectrum Showing White Space. Source: (Rajbanshi, 2007)
Fig. 3: Basic Cognition Cycle. Source: Ref. [5].

Analysis and Application of Cognitive Radio Islam et al.
JoCES (2014) 1-8 © STM Journals 2014. All Rights Reserved Page 4
Cognitive Cycle
Operations of the CR are controlled by the
Cognitive Engine (CE). The CE works
according to the cognitive cycle [6, 8]. The
cognitive cycle consists of various steps as
shown in Figure 3. This cycle includes
analyzing the RF stimuli from outside
environment and sensing spectrum holes. It
also includes functions like transmission
power control and spectrum management after
sensing the white spaces to ensure interference
free opportunistic spectrum access.
The CE performs the tasks of sensing,
analysis, learning, decision making and
reconfiguration [9]. CR networks consist of
two types of users—primary (licensed) and
secondary (unlicensed or cognitive) users.
Licensed users have higher priority for the
usage of the licensed spectrum [10]. On the
other hand, unlicensed users can
opportunistically communicate in licensed
spectrum by changing their communication
parameters in an adaptive way when spectrum
holes are available [10, 11].
Important Functions of a CR [12]
Spectrum Sensing: Spectrum sensing means
to sense the unutilized spectrum bands.
Detection of spectrum holes is one of the basic
functions of CR. Spectrum sensing techniques
could be broadly categorized as:
a) Transmitter Detection: It is a way of
spectrum sensing in which presence of
primary transmitter signal is sensed. It
could be achieved by the techniques like
energy detection, cyclostationary feature
detection and matched filter detection.
b) Cooperative Detection: In this method
information from various cognitive users
is used to sense primary user presence.
c) Interference-Based Detection: In this
method primary user is detected on the
basis of RF interference.
Spectrum Management: It is the process of
capturing best available spectrum considering
user and QoS requirements. Spectrum
management is an important function of CR as
it decides the best available spectrum
opportunity for secondary users. Spectrum
management function could be further
classified into spectrum analysis and spectrum
detection.
Spectrum Mobility: Spectrum mobility refers
to the transition of cognitive user from one
frequency to another. This transition is
possible due to detection of some other best
spectrum opportunity or due to primary user
detection on the same spectrum. As CR works
on the basis of dynamic spectrum access thus
maintains seamless transitions.
Spectrum Sharing: Spectrum sharing refers to
spectrum scheduling. It enables CR users to
efficiently utilize and share used licensed
spectrum. Spectrum sharing is one of the
major challenges of open spectrum access.
FOURTH GENERATION WIRELESS
SYSTEMS
The existence of 4G Networks in today’s
technology-driven society is important
indicators of advancement and change. 4G, or
Fourth Generation networks, are designed to
facilitate improved wireless capabilities,
network speeds, and visual technologies.
While neither standards bodies nor carriers
have concretely defined or agreed upon what
exactly 4G will be, it is expected that end-to-
end IP and high quality streaming video will
be among 4Gs distinguishing features. 4G
promises to offer a vast range and diversity of
converged devices, services and networks to
revolutionize the way we communicate. 4G
would influence today’s networking
architecture where the inter user
communication is realized with the help of
third party communication infrastructure. 4G
would not only offer ultra high data rates but
would also enable a ubiquitous computing
paradigm [13].
4G Features
4G is the fourth generation of mobile phone
mobile communication technology standards.
It is the successor to 3G technology. It does
not have its own release versions whereas it
has release versions of technologies under it.
The technologies under it are WiMAX, Lte. It
is completely based on Internet Protocol. It has
data bandwidth of 200 Mbps, and flexible
bandwidth. The spectral efficiency could be 20
MHz, and has low cost than 3G. The data
throughput practically is 3–5 Mbps and
potentially it is 100–300 Mbps. It has a peak
upload rate of 500 Mbps. The peak download
rate is 1 Gbps.

Journal of Communication Engineering & Systems
Volume 4, Issue 3
ISSN: 2249-8613 (online), ISSN: 2321-5151 (print)
JoCES (2014) 1-8 © STM Journals 2014. All Rights Reserved Page 5
Table 1: Features of 4G [15].
Specifications
4G
Frequency band
2–8 GHz
Bandwidth
5–20 MHz
Data rate
20 Mbps or more
Access
Multi-carrier – CDMA or OFDM (TDMA)
FEC
Concatenated codes
Switching
Packet
Data throughput:
3–5 Mbps but potential estimated at a range of 10–300 Mbps.
Peak upload rate
50 Mbit/s
Peak download rate
1 Gbit/s
Switching technique
Packet switching, message switching
Network architecture
Integration of wireless LAN and Wide area
Services and applications
Wimax2 and LTE-Advance
Forward error correction (FEC)
Concatenated codes are used for error corrections in 4G
Frequency band
2–8 GHz
It supports packet as well as message
switching. Its network architecture is
integration of wireless LAN and wide area
network. It uses concatenated codes for error
correction. It has frequency band of 2–8 GHz.
It provides HD video access to the users.
Virtual presence is also possible. It provides
virtual navigation. 4G networks are likely to
use a combination of WiMAX and WiFi
technologies [14]. The features of 4G are
given in Table 1.
APPLICATION OF COGNITIVE
RADIO IN 4G
When fully implemented, 4G is expected to
enable pervasive computing, in which
simultaneous connections to multiple high
speed networks provide seamless handoffs
throughout a geographical area. The network
operators may employ technologies such as
CR and wireless mesh networks to ensure
connectivity and efficiently distribute both
traffic and spectrum [14]. Multiple standards
of 3G make it difficult to roam and
interoperate across various networks, whereas
4G provides global standard that provides
global mobility. This is possible with the help
of CR. As a support of Mobility Management,
the communication between different systems
should be established through generic
interfaces. Multimode terminals are the one
aspect considered for 4G systems. 4G systems
will prove to be far cheaper than 3G, since
they can be built atop existing networks and
won’t require carriers to purchase costly extra
spectrum. In addition to being a lot more cost
efficient, so carriers can do more with less
[16]. With 4G systems there will be a need to
design a single user terminal that can operate
in different wireless networks and overcome
the design problems such as limitations in the
size of the device, its cost and power
consumption. This problem can be solved
using Software-defined Radio/CR approach
i.e., user terminal adapts itself to the wireless
interfaces of the network. Another important
role of CR in 4G communications is that the
4G devices are expected to be more visual and
intuitive rather than today’s text and menu-
based systems. They will be able to interact
with the environment around it and act
accordingly [17].
Typical key applications scenarios of CR are:
1. Senses the radio frequency environment
for the presence of white spaces.
2. Manages the unused spectrum.
3. Increases the efficiency of the spectrum
utilization significantly.
4. Improves the spectrum utilization by
neglecting the over occupied spectrum
channels and filling the unused spectrum
channels.
5. Improves the performance of the overall
spectrum by increasing the data rate on
good channels and moving away from the
bad channels.
6. Use the unused spectrum for new business
propositions, such as providing high speed
internet in the rural areas and high data

Analysis and Application of Cognitive Radio Islam et al.
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rate network applications like video
conferencing can be made. A CR makes
use of the available spectrum efficiently,
solves the spectrum scarcity issue and thus
can save millions of dollars [18].
CR technology can become a key enabler for
true heterogeneous communication
environment where data-aided mitigation
techniques, such as physical or logical layer
cognitive pilot channel (CPC) will be
implemented for optimal sharing of the
spectrum and coexistence with least
interference among various radio access nodes.
These ideas gain in importance especially with
respect to the vision of Future Internet or
Internet of Things, where a multitude of
different devices are expected to communicate
seamlessly and rearrange their network
configuration in an autonomous fashion in
order to route/exchange the information in
most efficient way. The cognitive and
reconfigurable radio paradigms with CPC and
cognitive routing schemes are expected to
contribute greatly to the realization of this
vision, as forecasted by the Future Internet
Assembly and reflected in the 7th Framework
Program (2007–2013) of the European
Community for research, technological
development and demonstration activities.
Standards which incorporate this research:
1. Stand-alone CR systems (to be
standardized and developed)—IEEE
802.22 is currently the only candidate.
This standard foresees a Wireless Regional
Area Network (WRAN) to access white
spaces in TV bands.
2. Cognitive capabilities built into other
standards—IEEE 802.16 e/h/m presents a
good example of this approach,
focusing on the coexistence of WiMAX
systems in unlicensed bands [17].
IEEE 802.22 (Table 2)
IEEE 802.22 defines air interface for use by
license-exempt devices on a noninterfering
basis in VHF and UHF (54–862 MHz) bands
which are also referred to as the TV White
Spaces. This 802.22 standard utilizes CR
technology to ensure that no undue
interference is caused to television services
using the television bands. In this way 802.22
is the first standard to fully incorporate the
concept of CR. This new standard, which will
operate in the TV bands, makes use of
techniques such as spectrum sensing,
incumbent detection and avoidance, and
spectrum management to achieve effective
coexistence and radio resource sharing with
existing licensed services [19].
Table 2: IEEE 802.22 WRAN System Capacity and Coverage [16].
1.
RF channel bandwidth
6 MHz
2.
Average spectrum efficiency
3 bit/s/Hz
3.
Channel capacity
18 Mbit/s
4.
System capacity per
1.5 Mbit/s
5.
subscriber(forward)
384 Kbit/s
6.
System capacity per
3.9
7.
subscriber(Return)
50
8.
Forward/return ratio
600
9.
Over subscription ratio
90 subs
10.
Number of subscribers per channel
3 bit/s/Hz
11.
Minimum number of subscribers
1800 subs
12.
Assumed early take up rate
2.5 persons
13.
Potential number of subscribers
4500 persons
14.
Assumed number of persons per household
98.3 W
15.
Total number of persons per coverage area
30.7 Km
16.
WRAN base station EIRP
1.5 person/Km2
17
Radius of coverage for WRAN system
OFDM
18
Minimum population density covered
Spectrum
19
Modulation Methodology
Sensing to identify free channels

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IEEE 802.16e/h/m
IEEE 802.16-based WiMAX is also gaining
attention as a 4G solution. It uses OFDMA-
based multicarrier modulation, MIMO, and
other advanced features along with CR
technology to greatly improve the mobile
wireless services. WiMAX supports either
manual or automatic selection of networks
based on user preference and defines protocols
to support this. This is said to be done with the
help of CR technique [17].
802.16 Family
802.16
LOS 10–66 GHz
802.16a
2–11 GHz (superceded by 802.16-2004)
802.16c
2–11 GHz (superceded by 802.16-2004)
802.16d
Combined 802.16, 802.16a, 802.16c into
802.16-2004
802.16e
Approved 2005 Dec 7. Published Feb 2006.
802.16f
Network Management Information Base
(MIB) Published 2005 Dec1.
802.16g
Network Management Plane Draft 2006 Feb
802.16h
Coexistence with license-exempt 802.16
protocols (Draft)
802.16i
Mobile Management Information Base
(explicitly to handle updates from 802.16e)
802.16j
Mobile Multihop Relay
802.16k
Network Management/Bridging
802.16m
4G WiMAX
CONCLUSION
Next Generation Networks are being
developed to solve current wireless network
problems resulting from the limited available
spectrum and inefficiency in the spectrum
usage by exploiting the existing wireless
spectrum opportunistically. Next Generation
Networks, equipped with the intrinsic
capabilities of the CR, will provide an ultimate
spectrum-aware communication paradigm in
wireless communications.
In this survey, the CR capabilities, furthermore
the application of CR on 4G communication
systems has been emphasized. The various
application scenarios and the standards
incorporating them have been reviewed.
Internet is a driving force for higher data rates
and high speed access for mobile wireless
users. 4G systems will give value added
services but still they will offer a lot many
challenges till they get fully implemented. The
growth of 4G technology will be enhanced
with the development of the open standards.
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