Licensed Spectrum sharing, Unlicensed Spectrum sharing and Secondary Spectrum Access

1. Licensed Spectrum sharing, Unlicensed Spectrum
sharing and Secondary Spectrum Access
Rafi Ullah Khan, Naeem Aslam, Motsaim Sohail
The department of Telecommunication Engineering
The Islamia University of Bahawalpur (BWP)
Bahawalpur , Pakistan
Engr.rafi18@gmail.com
Naeemaslam14@gmail.com
Somig7@gmail.com
Abstract—now a day there is lots of work is happening on
the sharing of spectrum. First of all we have to know about
that what is spectrum sharing and how we can share
spectrum. Sharing of spectrum is the most critical part of
the telecommunication society and if we or someone else
want to use licensed spectrum sharing then we have to pay
for it. In licensed spectrum sharing there is some bands that
are defined by the international telecommunication union
(ITU). The next type of spectrum sharing is the unlicensed
spectrum sharing in which is unlicensed spectrum of
frequency is used and whoever want can use that portion of
frequency. The use of unlicensed spectrum is free of cost
and there is no rules and regulation for the unlicensed
spectrum. The ratio of VHF/UHF wideband is used for the
secondary spectrum access candidate, which is also named
as TV white spaces.
Keywords—Licensed spectrum sharing, Unlicensed
spectrum sharing, FCC (federal communication
commission), Sectoring, HAN (home area network),
Neighbour area network (NAN), Distribution area network
(DAN), Very high frequencies (VHF), Ultra High
Frequency (UHF)
1 LICENSED SPECTRUM
For more than 20 years broadband mobile networks are
developed using licensed or dedicated spectrum.
Commercially all cellular networks are assigned spectrum
bands to operators in dedicated blocks. These dedicated
frequency bandwidths are often assigned by competitive
auctions. Devices operation in the licensed spectrum operates
in the portion of that radio spectrum which is designed by
FCC. That spectrum is for those organizations which have
bought or which are granted by the licenses ot radio spectrum.
Having the rights of license, a radio spectrum user operates
without interference of radio channels or frequencies and also
without crowding in the radio spectrum. Law enforcement and
legal protection is provided by FCC when other operators
transmit over the similar frequency and within the similar
geographical area. FCC prevents them from using someone
else’s spectrum. An organization has legal rights to use the
frequencies allotted to that organization with in the same area
after purchasing the license.
Communications in these bands have power limitations and
also use carrier of single frequency so in fact the tendency of
these communications is purely narrow band by nature wise.
Due to excellent ratio of signal and noise (S/N), licensed
spectrum have clear advantages over undedicated frequency
or unlicensed frequency spectrum.
Potentially, strong level of signals is almost 10 to 100 times
more powerful than undedicated spectrum of frequencies
when central collector is use in the system. Instead, having
multiple of miles between end users, wireless network can
transmit up to 20 miles between them easily. Licensed
spectrum although have multiple advantages over unlicensed
spectrum, it is scarce resource which is difficult to manage
and expensive to adopt. Limited availability of frequency
bandwidth can be an issue to deal with.
The only FCC licensed communication network is Senses
Flex Net system which is designed particularly for utilities of
water, electric and gas. This system acquired protected
spectrum to solve the issues of water, gas and electric and aids
their customers to overcome the issues which their customers
faces. These issues are overcome by using 325 kHz
bandwidth along with the highest RF powers.
A worldwide example of licensed spectrum is shown in the
following figure1.

2. Licensed spectrum examples are use of the harmonized ECS
bands (790-862 MHz, 880-915 MHz, 925-960 MHz, 1710-
1785 MHz, 1805-1880 MHz, 1920-1980 MHz, 2110-2170
MHz, 2500-2690 MHz, and 3400-3800 MHz) which are used
for the provision of electronic communication services. In
such cases, responsibility to protecting the licensed user
against interference is taken by the regulator and it also
provides a legal basis for ensuring a certain quality of service
(QoS).
Another example of spectrum allocation or licensed
spectrum for Ip based networks such as Home Area Network
(HAN), Neighborhood Area Network (NAN) and Distribution
Area Network (DAN) is given in the following table.
2 UNLICENSED SPECTRUM
Unlicensed spectrum bands are those frequency bands
that have technical specified rules for both hardware and
software, but the number of users are not specifies, it has
limitless users. Any user which have certified equipment from
federal communication commission (FCC), he can use
unlicensed spectrum bands at any time either it is publically
purpose or private purposes. There is one expectable usage for
the user is that he needs no protection against the interference
like in the licensed spectrum bands. The rule that is specified
from the federal communication commission for the Wi-Fi
purposes are called 802.11 protocols so they can minimize the
error of interference.
The history of unlicensed spectrum the law which is
obeyed by the users is PART 15. After that the national
telecommunication and information administration (NTIA)
participate for the limitations of unlicensed spectrum
frequency bands. The recent technologies are spread
spectrum, Wi-Fi, software-defined-radio (SDR), ultra-wideband
etc. The bands that are unlicensed significantly are
given below and they are specified by the federal
communication commission:
 3.6 GHz (3650-3700 MHz)
 61 GHz (57-64 GHz)
 1920-1930 MHz
 902-928 MHz
 2.4 GHz
The question which is raised in all the readers minds that
why we need unlicensed spectrum bands?? The answer for
that question is to save the licensed bands and other services
that may cause to do damage to the licensed spectrum bands
and also to protect higher frequency bands.
The quality of service in between the licensed and the
unlicensed spectrum bands are that, how much facilitate the
users and easy access of the spectrum is. In comparison with
the licensed, unlicensed spectrum provides better services,
technology and devices. For better services we need to build a
strong infrastructure and high beam antennas that really
increase both of the received and the transmitted power and in
this way we can minimize the interference. In the case of
licensed share spectrum it will be much more complex to
handle and to solve the problems, and the cost of licensed
spectrum is very much high [2][3].
2.1 CHARACTERISTCS
 The time required will be less
 The bandwidth needs
 The required frequency limit for the service
2.2 WHY WE NEED SPECTRUM SHARING
The wireless communication is becoming the key part of
any type of communication, because it is cheaper, easy to
maintain. In every department of our life the communication
is backbone for it. The wireless communication providing us
capacity and mobile broadband. We used the concept of
“SECTORING” in wireless communication. In the sectoring
we divide the whole cell with an angle of 360 degree around

3. and into smaller slices, these slices are basically called
sectors, if we add these sectors the it will complete a cell.
In fixed sector, the wireless facilities can be provide
remotely, but in the case of mobile sectoring the cells are
become small due to increasing the cell capacity. The used
wireless cellular networks are increasing day by dy, so the
scientists should have to develop a method that to increase
data rates and number of users in a fives sectors with respect
to the recommendation of international telecommunication
union, this can be achieved by two ways.
 Shrinking of cell
 Using more spectrum
Fig 2 A Cell Sectoring.
2.3 SHARING OF UNLICENSED SPECTRUM
The major problem of unlicensed spectrum is that
there are multiple interfaces and the systems on a same place,
due to these problems the situation will be arise which will be
inefficient for the whole enterprise. To remove the problems
of inefficient sharing in the unlicensed spectrum we have to
build the enforcing protocols that really suit the situation. The
first step is that first of all we will do the all possible
responses. We have to make scenario where there are multiple
systems are exist at the same place, in the urban dense areas
the protocols which e used for the wi-fi purposes is 802.11
networks, and the sharing of spectrum is exist like ISM
unlicensed spectrum sharing. In the unlicensed spectrum
sharing us build a law that has only one goal is to increase the
spectrum efficiency.
To increase system efficiency, data rates, and the
bandwidth which is compatible for the single system? a
resource-allocation is the self-enforcing method without
minimizing the system performance. We can used the power
transmit limit, this will minimized the amount of interference.
For efficient resource allocation we make some situations
according to the scenario. The use unlicensed spectrum is
depends upon some technical condition, like we discuss
earlier that by transmitting low power that will help to
minimize the amount of interference.
Unlicensed spectrum sharing will be much more
efficient, reliable for only low traffic situations if the traffic is
high then the contention can arise, for that reason we use
carrier sense multiple access. No access codes are
implemented in the unlicensed spectrum sharing, this cause
large interference because if there are no passwords then the
user will be maximum and if user will be maximum then the
traffic will be higher and contention can arise that will cause
the interference. If we ignore the difficulties arising the in the
unlicensed spectrum sharing it is very useful in the increase of
users and the coverage area [1].
3 SECONDARY SPECTRUM ACCESS
The ratio of VHF/UHF wideband is used for the
secondary spectrum access candidate, it is also called TV
white spaces [4][5][6], it has been invented in recent times.
But the effect of the interference which has been added from
the nearby channels, that interference has not been under
consideration, the interference from the entire channels
combine and added to the path. The secondary spectrum
opportunities for mobile and portable devices which combine
with database of geo-locations. The evaluated opportunities in
maximal secondary users that can reach the “TV white space”
at the same time. There is a special band is given to the
emphasis to protect the TV receiver from the interference
caused from the adjacent channel and the channel path itself
so that the transmission of the television is not effected from
the interference. Suffering from the less number of users at the
different locations, by using the process of optimization we
can increase the number of secondary spectrum access users at
two different locations very easily .If we look out to the
characteristic of the interference in depth we can easily
identified that the adjacent channel causes the really big threat
in the process of TV channels and specially for those channels
that has low transmitted power .If we really succeeded in the
protection from the interference then the TV channels
secondary spectrum access can be implemented to the very
wider geographical area at the different locations.
Today we are really known very well about that the
use of wireless network is rapidly increasing and the wireless
network providers are in the searching to increase the mobile
and the broadband traffic. In the secondary spectrum we don’t
really need very large spectrum and it is also under-licensed
and can be efficiently used and it attracts the usage in the
industry and for the education purposes. The UHF/VHF TV
band are mostly considered as the secondary spectrum access
candidates. The secondary users are in under considerations to
the scientists, designing both optimized solutions and heuristic
[8][9] algorithm and optimized solutions[10][11] for the
transmitting of power from the different locations. Those
researches are really stand us to calculate the interference and
how to minimized that interference by optimizing, however
the main aim of the scientists to minimize the co-channels
interference for the TV secondary subscriber at the different

4. locations and at the very long distances from the source
channel.
The TV receiver which can be very effected to
adjacent channel interferences (ACI) , this effect of co-channel
interference can really do damage if the secondary
subscriber transmitting to the power of the victim. The effect
of the co-channels interference can be scenario based if the
portable device and the secondary subscriber are in the dense
populated areas where that the co-channels are located very
close to each other and the effect of the co-channel
interference will be maximum. The scientists are doing for the
work of how we can combine the effect of these two types of
interference is still in under processes. The phenomena of
co-channel interference and adj-cha interference is shown in
the following figure 3.1, figure 3.2, figure 3.3 and figure 3.4
below.
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4
A) PRIMARY SYSTEM
Terrestrial TV network broadcasting that station can go
about to the area of radius 30-50 km.The range of terrestrial
system will be same either the TV receiver has an indoor
antenna or the rooftop antenna. To avoid the interference
between the two co-channels the nearby TV receiver has to be
connected to the different subset of the channels to avoid the
mutual interference [6][10][14]. However they are provided
for secondary reuse.
B) SECONDARY SYSTEM
In the commercial point for reuse of ’TVWS’ are in
under lies in the scenario to the heavily populated
implemented short-range or other indoor system. So, the
secondary system is in under study in the portable and mobile
devices, to the low transmit power. The Wi-Fi system is the
best example of this system. Secondary user can be
implemented to either indoor or outdoor secondary system,
transmitting with limited fixed power.
c) COEXISTENCE DEPLOYMENT SCENARIOS
The system which are described earlier (primary and
secondary system) in the fig we can seen the portion A,B can
be easily identified, receiver of TV is linked the indoor
antenna. We can see in the figure clearly that the effect of co-channel
interference will be greater on the portion A, however
the receiver of both TV stations are located indoor. If we look
out to the receiver part of which is connected to the roof-top
antenna. The links are free from penetration loss of indoor

5. walls. The common channel interference is located at the roof-top
so it will exhibit low interference as compared to the part
b, because in the previous case both the antenna and the
receiver located inside the height of the clutters.
CONCLUSION
Unlicensed spectrum bands have specified rules for
sharing but there is no limit of the users in unlicensed
spectrum sharing. There are two possible techniques to
increase the system capacity for the unlicensed spectrum
sharing which is in turn are Resource Allocation and the Self-
Enforcing methods. Both methods increase the system
efficiency, bandwidth, data rates which suits the system
compatibility and the system enhancement. Licensed spectrum
includes the sharing of dedicated frequency bands. Lenience
of limited frequency band is allocated to the organizations
which purchase them in bidding. The dedicated band of
frequency is only permitted to be used by the concerned
organization or user. Licensed spectrum is more secure and
beneficent to use than unlicensed having less interference and
secure communication. In secondary spectrum access we used
two frequencies ultra-high frequencies and the very high
frequencies to get the system spectrum access. We used co-channel
interference technique in the secondary spectrum
access which is adjacent channel interference to increase the
use of same frequencies in the adjacent channels and we do
not require the larger bandwidth in the secondary spectrum
access. Using this, the major effect of interference will be
minimize.
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