Mobile technology-Unit 1

Mobile Technologies- Unit 1 ~SRP
Introduction to Mobile Computing
Mobile Computing is a technology that allows transmission of data, voice and video
via a computer or any other wireless enabled device without having to be connected
to a fixed physical link. The main concept involves −
 Mobile communication
 Mobile hardware
 Mobile software
Mobile communication
The mobile communication in this case, refers to the infrastructure put in place to
ensure that seamless and reliable communication goes on. These would include
devices such as protocols, services, bandwidth, and portals necessary to facilitate
and support the stated services. The data format is also defined at this stage. This
ensures that there is no collision with other existing systems which offer the same
service.
Since the media is unguided/unbounded, the overlaying infrastructure is basically
radio wave-oriented. That is, the signals are carried over the air to intended devices
that are capable of receiving and sending similar kinds of signals.
Mobile Hardware
Mobile hardware includes mobile devices or device components that receive or
access the service of mobility. They would range from portable laptops,
smartphones, tablet Pc's, Personal Digital Assistants.

These devices will have a receptor medium that is capable of sensing and receiving
signals. These devices are configured to operate in full- duplex, whereby they are
capable of sending and receiving signals at the same time. They don't have to wait
until one device has finished communicating for the other device to initiate
communications.
Above mentioned devices use an existing and established network to operate on. In
most cases, it would be a wireless network.
Mobile software
Mobile software is the actual program that runs on the mobile hardware. It deals
with the characteristics and requirements of mobile applications. This is the engine
of the mobile device. In other terms, it is the operating system of the appliance. It's
the essential component that operates the mobile device.
Since portability is the main factor, this type of computing ensures that users are not
tied or pinned to a single physical location, but are able to operate from anywhere. It
incorporates all aspects of wireless communications.
Mobile Computing - Brief Evolution
In today's computing world, different technologies have emerged. These have
grown to support the existing computer networks all over the world. With mobile
computing, we find that the need to be confined within one physical location has
been eradicated. We hear of terms such as telecommuting, which is being able to
work from home or the field but at the same time accessing resources as if one is in
the office.

The advent of portable computers and laptops, Personal Digital Assistants (PDA),
PC tablets and smartphones, has in turn made mobile computing very convenient.
The portability of these devices ensure and enable the users to access all services
as if they were in the internal network of their company. For example, the use of
Tablet PC and iPads. This new technology enables the users to update documents,
surf the internet, send and receive e-mail, stream live video files, take photographs
and also support video and voice conferencing.
The constant and ever increasing demand for superior and robust smart devices
has been a catalyst for market share. Each manufacturer is trying to carve a niche
for himself in the market. These devices are invented and innovated to provide
state-of-the-art applications and services. For instance, different manufacturers of
cellular phones have come up with unique smartphones that are capable of
performing the same task as computers and at the same processing speed. The
market share for different competitors is constantly being fought for. For example,
the manufacturers of Apple's iPhone OS, Google's Android' Microsoft Windows
Mobile, Research In Motion's Blackberry OS, are constantly competing to offer
better products with each release.

The need for better, portable, affordable, and robust technology has made these
vendors to constantly be innovative. Market figure and statistics show an ever
growing need to purchase and use such devices for either professional or personal
use. It is in this light that services to suit long-term implementation are developed or
innovated. It has also pushed other industry vendors to adopt services that will
provide better services. For example, cellular service providers are forced to
improve and be innovative to capture more subscribers. This can be in terms of
superior services such as high speed internet and data access, voice and video
service etc. Hence the adoption of different generations of networks like of 2G,
2.5G, 3G, 4G network services.
The essence of mobile computing is to be able to work from any location. The use
of iPads, tablets, smartphones, and notebooks, have pushed the demand for these
devices. Modern day workers have such devices that enable them to carry out their
work from the confines of their own location. These devices are configured to
access and store large amounts of vital data. Executive and top management can
take decisions based on ready information without going to the office. For example,
sales reports and market forecasts can be accessed through these devices or a
meeting can take place via video or audio conferencing through these devices. With
such features being high in demand, manufacturers are constantly coming up with
applications geared to support different services in terms of mobile computing.

Mobile Computing - Classification
Mobile computing is not only limited to mobile phones, but there are various
gadgets available in the market that are built on a platform to support mobile
computing. They are usually classified in the following categories −
Personal Digital Assistant (PDA)
The main purpose of this device is to act as an electronic organizer or day planner
that is portable, easy to use and capable of sharing information with your computer
systems.
PDA is an extension of the PC, not a replacement. These systems are capable of
sharing information with a computer system through a process or service known as
synchronization. Both devices will access each other to check for changes or
updates in the individual devices. The use of infrared and Bluetooth connections
enables these devices to always be synchronized.
With PDA devices, a user can browse the internet, listen to audio clips, watch video
clips, edit and modify office documents, and many more services. The device has a
stylus and a touch sensitive screen for input and output purposes.
Smartphones
This kind of phone combines the features of a PDA with that of a mobile phone or
camera phone. It has a superior edge over other kinds of mobile phones.
Smartphones have the capability to run multiple programs concurrently. These
phones include high-resolution touch screens, web browsers that can access and
properly display standard web pages rather than just mobile-optimized sites, and
high-speed data access via Wi-Fi and high speed cellular broadband.
The most common mobile Operating Systems (OS) used by modern smartphones
include Google's Android, Apple's iOS, Nokia's Symbian, RIM's BlackBerry OS,
Samsung's Bada, Microsoft's Windows Phone, and embedded Linux distributions
such as Maemo and MeeGo. Such operating systems can be installed on different

phone models, and typically each device can receive multiple OS software updates
over its lifetime.
Tablet PC and iPads
This mobile device is larger than a mobile phone or a PDA and integrates into a
touch screen and is operated using touch sensitive motions on the screen. They are
often controlled by a pen or by the touch of a finger. They are usually in slate form
and are light in weight. Examples would include ipads, Galaxy Tabs, Blackberry
Playbooks etc.
They offer the same functionality as portable computers. They support mobile
computing in a far superior way and have enormous processing horsepower. Users
can edit and modify document files, access high speed internet, stream video and

audio data, receive and send e-mails, attend/give lectures and presentations among
its very many other functions. They have excellent screen resolution and clarity.
Mobile Computing - Major Advantages
Mobile computing has changed the complete landscape of our day-to-day life.
Following are the major advantages of Mobile Computing −
Location Flexibility
This has enabled users to work from anywhere as long as there is a connection
established. A user can work without being in a fixed position. Their mobility
ensures that they are able to carry out numerous tasks at the same time and
perform their stated jobs.
Saves Time
The time consumed or wasted while travelling from different locations or to the
office and back, has been slashed. One can now access all the important
documents and files over a secure channel or portal and work as if they were on
their computer. It has enhanced telecommuting in many companies. It has also
reduced unnecessary incurred expenses.
Enhanced Productivity
Users can work efficiently and effectively from whichever location they find
comfortable. This in turn enhances their productivity level.
Ease of Research
Research has been made easier, since users earlier were required to go to the field
and search for facts and feed them back into the system. It has also made it easier
for field officers and researchers to collect and feed data from wherever they are
without making unnecessary trips to and from the office to the field.
Entertainment
Video and audio recordings can now be streamed on-the-go using mobile
computing. It's easy to access a wide variety of movies, educational and informative
material. With the improvement and availability of high speed data connections at
considerable cost, one is able to get all the entertainment they want as they browse
the internet for streamed data. One is able to watch news, movies, and
documentaries among other entertainment offers over the internet. This was not
possible before mobile computing dawned on the computing world.
Streamlining of Business Processes
Business processes are now easily available through secured connections. Looking
into security issues, adequate measures have been put in place to ensure
authentication and authorization of the user accessing the services.

Some business functions can be run over secure links and sharing of information
between business partners can also take place.
Meetings, seminars and other informative services can be conducted using video
and voice conferencing. Travel time and expenditure is also considerably reduced.
Mobile Computing - Security Issues
Mobile computing has its fair share of security concerns as any other technology.
Due to its nomadic nature, it's not easy to monitor the proper usage. Users might
have different intentions on how to utilize this privilege. Improper and unethical
practices such as hacking, industrial espionage, pirating, online fraud and malicious
destruction are some but few of the problems experienced by mobile computing.
Another big problem plaguing mobile computing is credential verification. As other
users share username and passwords, it poses as a major threat to security. This
being a very sensitive issue, most companies are very reluctant to implement
mobile computing to the dangers of misrepresentation.
The problem of identity theft is very difficult to contain or eradicate. Issues with
unauthorized access to data and information by hackers, is also an enormous
problem. Outsiders gain access to steal vital data from companies, which is a major
hindrance in rolling out mobile computing services.
No company wants to lay open their secrets to hackers and other intruders, who will
in turn sell the valuable information to their competitors. It's also important to take
the necessary precautions to minimize these threats from taking place. Some of
those measures include −
 Hiring qualified personnel.
 Installing security hardware and software
 Educating the users on proper mobile computing
ethics
 Auditing and developing sound, effective policies to
govern mobile computing
 Enforcing proper access rights and permissions

These are just but a few ways to help deter possible threats to any company
planning to offer mobile computing. Since information is vital, all possible measures
should be evaluated and implemented for safeguard purposes.
In the absence of such measures, it's possible for exploits and other unknown
threats to infiltrate and cause irrefutable harm. These may be in terms of reputation
or financial penalties. In such cases, it's very easy to be misused in different
unethical practices.
If these factors aren’t properly worked on, it might be an avenue for constant threat.
Various threats still exist in implementing this kind of technology.
Mobile Computing - Current Trends
This chapter lists down the current mobile technologies starting from 3G
technologies which is the hottest mobile technology available in the market.
3G
3G or third generation mobile telecommunications is a generation of standards for
mobile phones and mobile telecommunication services fulfilling the International
Mobile Telecommunications-2000 (IMT-2000) specifications by the International
Telecommunication Union. Application services include wide-area wireless voice
telephone, mobile Internet access, video calls and mobile TV, all in a mobile
environment.
Global Positioning System (GPS)
The Global Positioning System (GPS) is a space-based satellite navigation system
that provides location and time information in all weather, anywhere on or near the
Earth, where there is an unobstructed line of sight to four or more GPS satellites.
The GPS program provides critical capabilities to military, civil and commercial
users around the world. In addition, GPS is the backbone for modernizing the global
air traffic system, weather, and location services.
Long Term Evolution (LTE)
LTE is a standard for wireless communication of high-speed data for mobile phones
and data terminals. It is based on the GSM/EDGE and UMTS/HSPA network
technologies, increasing the capacity and speed using new modulation techniques.
It is related with the implementation of fourth Generation (4G) technology.

WiMAX
WiMAX (Worldwide Interoperability for Microwave Access) is a wireless
communications standard designed to provide 30 to 40 megabit-per-
second data rates, with the latest update providing up to 1 Gbit/s for
fixed stations. It is a part of a fourth generation or 4G wireless-
communication technology. WiMAX far surpasses the 30-metre wireless
range of a conventional Wi-Fi Local Area Network (LAN), offering a
metropolitan area network with a signal radius of about 50 km. WiMAX
offers data transfer rates that can be superior to conventional cable-
modem and DSL connections, however, the bandwidth must be shared
among multiple users and thus yields lower speed in practice.
Near Field Communication
Near Field Communication (NFC) is a set of standards for smartphones
and similar devices to establish radio communication with each other by
touching them together or bringing them into close proximity, usually no
more than a few centimeters. Present and anticipated applications
include contactless transactions, data exchange, and simplified setup of
more complex communications such as Wi-Fi. Communication is also
possible between an NFC device and an unpowered NFC chip, called a
"tag".
Conclusion
Today's computing has rapidly grown from being confined to a single
location. With mobile computing, people can work from the comfort of
any location they wish to as long as the connection and the security
concerns are properly factored. In the same light, the presence of high
speed connections has also promoted the use of mobile computing.
Being an ever growing and emerging technology, mobile computing will
continue to be a core service in computing, and Information and
Communications Technology.

Mobile Communication
MOBILE COMPUTING TECHNOLOGIES
Mobile data processing is made available due to the advances in wireless technologies, and
location detection and positioning systems.
The current wireless technologies used for indoor and outdoor networks includes-
(i) In-room Networks-infrared Bluetooth and radio
frequency
(ii) Wireless LAN (WLAN),
(iii) Broadband Wireless Networks,
(iv) Wide Area Wireless/Radio Networks,
(v) Satellite-based Networks, and
(vi) Cellular Networks

Different generations of Wireless Technology

Cell
A cell is a certain, geographic location that is served by a particular
tower. If you are moving, your cellphone signal is transferred from
cell to cell, depending on your location. In order to prevent you from
losing the call. All of these cells are connected to a mobile switching
center. Signals are passed from the phone, through the antenna, and
sent through the switching center where they will either be passed to
another cell or converted to a signal that can be sent along traditional
telephone lines. The entire, complicated process only takes a second
to complete. Maintaining the system is very important to keeping the
lines of communication open.
Every city is divided into small areas each area is called as a cell thus
a cell is defined as a basic geographical unit of a cellular
communication system seriously pay attention this is important as the
city is geographically divided into small cells. It is mandatory that all
cells must be symmetrical in shape based on this.

We have four geometrical shapes such as Circle Square equilateral
triangle and hexagon. If we select the shape of a cell as a circle then
the area between the two circles will not get covered by the base
station and any attempt of communication from that area will fail.
Thus we eliminate the circular shape.
Hexagon has the highest area as compared to the other two shapes.
Thus we divide the geographical area into hexagonal cells.
Cluster group:
The next concept is a cluster a group of cells is called as a cluster. The
cluster size is not fixed. It depends on the requirements of the area.

Basic structure of mobile phone:
Let’s study the mobile phone system now the basic structure of the
mobile phone system is as shown.
Where MS means mobile station BTS is base transceiver station. BSC
is base station controller and MSC is mobile switching center. In this
diagram MS is nothing but the mobile phone of a user.
Call from one mobile to another mobile:
Every cell has its own base transceiver station at its center. Whenever
a call is set up the first signal is sent to the base transceiver station of
the cell from this base transceiver station it goes to the central base
station controller which controls the working of all the base stations
from BSC it then goes to MSC or mobile switching center which is
the master controller of the entire system. These MSC s are different
for different areas from MSC of area one the signal is transmitted to
MSC of area 2 where it follows the reverse sequence as MSC to BSC,
BSC to BTS and from BTS – MS. Whenever a user makes an attempt
to call someone a separate channel is assigned to the user by the MSC
if all the channels are already occupied by other users then this user
has to wait for a channel to become free in such a case the user gets
the notification such as call cannot be completed or network error etc

Features of cellular concept:
Frequency reuse:
Now let’s see the features of the cellular concept its first feature is
frequency reuse in frequency reuse same set of frequencies are used
for radio channels located in different areas as shown in the diagram
below.
Every cell named as a uses the same set of frequencies the advantages
of frequency reuse are many transmitters of small output power
operating at the same frequency can be used. It reduces the minimum
height of the transmitting antenna as each antenna has to cover a
small distance but the disadvantage is that if the system is not
properly designed then it may lead to co-channel interference. Co-
channel interference is a phenomenon in which two frequency signals
of adjacent channels interfere with each other.
Cell splitting:
The second feature of the cellular concept is cell splitting. In cell
splitting technique each cell is divided into smaller cells known as

micro cells. The radius of these small cells is half of the original
radius. Cell splitting technique proves advantages when the traffic of
cell phone users increases beyond the limit of a regular cell.
Handoff:
Let’s see what do we mean by a handoff procedure consider a
situation where we are traveling from place A to place B via a car.
Sometimes it happens that for a short period of 2 or 3 seconds the
signal strength on mobiles becomes very low and again it increases
and reaches its normal level. Have you ever thought why this
happens? The answer to this question is the handoff procedure when
someone user X travels in area A he receives the signal from base
station that is antenna a has a stronghold on out devices signal but as
he moves away from antenna a the signal strength gradually decreases
at a boundary of cell a the whole of antenna a on the device is
minimum at the same time when the device is about to enter into cell
B base station B starts to take hold on the device thus at the border of
cell a and cell B. Both the antennas have equal amount of hold on the
device of user X as user X crosses the border and enters into cell be
area B strength of base station. A very rapidly decreases and strength
of base station B rapidly increases in short the device receives the
signal network from base station B. But during this procedure the call
is still on. Hence base station a handovers this call to base station B
without any effect on a call this procedure is known as the handoff
procedure. This process happens so rapidly that the user never notices
it.
We all know that there are two types of systems available as GSM
and CDMA. We will only study the basics of GSM system GSM
stands for global system for mobile GSM is nothing but a big system
made up of few small systems. Such as mobile stations MS base
station subsystem, BSS network and switching subsystem NSS
operating subsystems OSS. The architecture of this GSM network is
as shown mobile station MS nothing but the device used for

communication. Such as cell phone fax machine etc base station
subsystem BSS. BSS gets connected to ms wire radio interface. it has
two different blocks as BTS base transceiver system and BSC base
station controller practically. Every MS gets connected to BTS of that
area this beauty s sends the signal to BSC many BTS are connected to
one BSC and at the end of this BSC is connected to MSC. Hence BSS
system consists of BTS and BSC network and switching subsystem
NSS. This system mainly contains MSC. MSC is the backbone of the
entire network it controls all the operations from setting up a call till
the handoff procedure other blocks of NSS are h l our home location
register which keeps the database of all the users who reside in the
same geographical area VL our visitor location register keeps the
track of all the users who are visitors for that particular geographical
area mainly roaming customers authentication center mainly controls.
The authentication of the users by checking their sim numbers etc and
sends the required information to the MSC
SIM:
what does a SIM card actually do we all know a mobile would not
work without one but why let’s start by looking at what SIM actually
stands for it stands for subscriber identity module. So fundamentally it
identifies your phone so when you send a message. Your phone
knows which network to use and your operator knows who to bail for
it though SIM contains more information. It contains of course your
number the information needed to bill you for a lot SIM. The SIM
obviously knows the unlock pin though you can’t get it out even if
you use scissors and it typically has contacts and messages saves on
its memory because of this you can easily move the SIM between
phones and keep your number. A simple way to think about it is that
once you insert a SIM card the phone becomes your phone. The
carrier extracts the information from a number this number is written
on the SIM card.

It is called the integrated circuit card identifier the shiny bit is an
integrated circuit basically just a bunch of transistors and this is
mounted on a card. It is a pointless name really but Telkom people
seem to love the raku names anyway the number is made up of an
issuer identification number and IIN more acronyms starting with an
industry identifier which is almost always 89 have a look at your SIM
card it probably starts with 89 then the country code, 44 for United
Kingdom then we have the individual account identification number
that is unique to you and finally we have a check digit that ensures
that the previous numbers are correct. So it checks for any miss prints
or errors and this is done using a clever algorithm developed IBM
which is Lunz checksum. Finally let’s look at something the very few
people know about there are two main ways of managing a network
GSM and CDMA. GSM is a global system for mobile that requires a
SIM and is used by almost everyone but you also have the entirely
valid code division multiple access system which does not require a
SIM how is this possible it’s quite complicated but basically what is
going on is the phone has a serial number and the carriers have a list
of the phone’s if your phone is on the list you can use the network.

Cells
A cell can be defined as an area of radio coverage from one BTS antenna
system. It is the smallest building block in a mobile network and a cell can be
represented by a hexagon.
There are two types of cells;
1. Omni directional cell:
An omni-directional cell (or omnicell) is served by a BTS with an
antenna which transmits equally in all directions (360 degrees).
2. Sector cell:
A sector cell is the area of coverage from an antenna, which transmits, in
a given direction only. For example, this may be equal to 120 degrees or
180 degrees of an equivalent omni- directional cell. One BTS can serve
one of these sector cells with a collection of BTS’s at a site serving more
than one, leading to terms such as two-sectored sites and more
commonly, three-sectored sites.

Clusters
Groups of frequencies can be placed together into patterns of cells
called clusters. A cluster is a group of cells in which all available
frequencies have been used once and only once.
Since the same frequencies can be used in neighboring clusters,
interference may become a problem. Therefore, the frequency re-use
distance must be kept as large as possible. However, to maximize
capacity the frequency re-use distance should be kept as low as
possible.
The re-use patterns recommended for GSM are the 4/12 and the
3/9 pattern. 4/12 means that there are four three-sector sites
supporting twelve cells using twelve frequency groups.
In the 3/9 cell pattern there are always 9 channels separating each
frequency in a cell. However, when compared with the 4/12 pattern,
cells A1 and C3 are neighbors and use adjacent frequencies.
Therefore, the C/A interference will increase. In this case, an operator
may use frequency hopping which, if planned correctly, could reduce
the possibility of such adjacent channel interference

Frequency Reuse
Frequency Reuse is the scheme in which allocation and reuse of channels
throughout a coverage region is done. Each cellular base station is allocated a
group of radio channels or Frequency sub-bands to be used within a small
geographic area known as a cell. The shape of the cell is Hexagonal. The
process of selecting and allocating the frequency sub-bands for all of the
cellular base station within a system is called Frequency reuse or Frequency
Planning.
Silent Features of using Frequency Reuse:
 Frequency reuse improve the spectral efficiency and signal Quality (QoS).
 Frequency reuse classical scheme proposed for GSM systems offers a
protection against interference.
 The number of times a frequency can be reused is depend on the tolerance
capacity of the radio channel from the nearby transmitter that is using the
same frequencies.
 In Frequency Reuse scheme, total bandwidth is divided into different sub-
bands that are used by cells.
 Frequency reuse scheme allow WiMax system operators to reuse the same
frequencies at different cell sites.

Cell with the same letter uses the same set of channels group or frequencies sub-
band.

TOTAL NUMBER OF CHANNELS (S)
To find the total number of channel allocated to a cell:
S = Total number of duplex channels available to use
k = Channels allocated to each cell (k<S)
N = Total number of cells or Cluster Size
Then Total number of channels (S) will be,
S = kN
FREQUENCY REUSE FACTOR
Frequency Reuse Factor = 1/N
In the above diagram cluster size is 7 (A,B,C,D,E,F,G) thus frequency reuse factor is
1/7.
THE NUMBER OF CELLS
N is the number of cells which collectively use the complete set of available
frequencies is called a Cluster. The value of N is calculated by the following
formula:
N = I2
+ I*J + J2
Where I,J = 0,1,2,3…

CAPACITY(C)-
Hence, possible values of N are 1,3,4,7,9,12,13,16,19 and so on.
If a Cluster is replicated or repeated M times within the cellular
system, then Capacity, C, will be,
C = MkN = MS
In Frequency reuse there are several cells that use the same set of
frequencies.
These cells are called Co-Channel Cells. These Co-Channel cells
results in interference.
So to avoid the Interference cells that use the same set of channels
or frequencies are separated from one another by a larger distance.
The distance between any two Co-Channels can be calculated by the
following formula:
D = R * (3 * N)1/2
Where,
R = Radius of a cell
N = Number of cells in a given cluster

BELOW IS THE PYTHON CODE FOR VISUALIZING THE
FREQUENCY REUSE CONCEPT
#!/usr/bin/python
from math import *
# import everything from Tkinter module
from tkinter import *
# Base class for Hexagon shape
class Hexagon(object):
def __init__(self, parent, x, y, length, color, tags):
self.parent = parent
self.x = x
self.y = y
self.length = length
self.color = color
self.size = None
self.tags = tags
self.draw_hex()
# draw one hexagon
def draw_hex(self):
start_x = self.x
start_y = self.y
angle = 60
coords = []
for i in range(6):
end_x = start_x + self.length * cos(radians(angle * i))

end_y = start_y + self.length * sin(radians(angle * i))
coords.append([start_x, start_y])
start_x = end_x
start_y = end_y
self.parent.create_polygon(coords[0][0],
coords[0][1],
coords[1][0],
coords[1][1],
coords[2][0],
coords[2][1],
coords[3][0],
coords[3][1],
coords[4][0],
coords[4][1],
coords[5][0],
coords[5][1],
fill=self.color,
outline="black",
tags=self.tags)
# class holds frequency reuse logic and related methods
class FrequencyReuse(Tk):
CANVAS_WIDTH = 800
CANVAS_HEIGHT = 650
TOP_LEFT = (20, 20)
BOTTOM_LEFT = (790, 560)
TOP_RIGHT = (780, 20)
BOTTOM_RIGHT = (780, 560)

def __init__(self, cluster_size, columns=16, rows=10, edge_len=30):
Tk.__init__(self)
self.textbox = None
self.curr_angle = 330
self.first_click = True
self.reset = False
self.edge_len = edge_len
self.cluster_size = cluster_size
self.reuse_list = []
self.all_selected = False
self.curr_count = 0
self.hexagons = []
self.co_cell_endp = []
self.reuse_xy = []
self.canvas = Canvas(self,
width=self.CANVAS_WIDTH,
height=self.CANVAS_HEIGHT,
bg="#4dd0e1")
self.canvas.bind("<Button-1>", self.call_back)
self.canvas.focus_set()
self.canvas.bind('<Shift-R>', self.resets)
self.canvas.pack()
self.title("Frequency reuse and co-channel selection")
self.create_grid(16, 10)
self.create_textbox()
self.cluster_reuse_calc()

# show lines joining all co-channel cells
def show_lines(self):
# center(x,y) of first hexagon
approx_center = self.co_cell_endp[0]
self.line_ids = []
for k in range(1, len(self.co_cell_endp)):
end_xx = (self.co_cell_endp[k])[0]
end_yy = (self.co_cell_endp[k])[1]
# move i^th steps
l_id = self.canvas.create_line(approx_center[0], approx_center[1],
end_xx, end_yy)
if j == 0:
self.line_ids.append(l_id)
dist = 0
elif i >= j and j != 0:
dist = j
# rotate counter-clockwise and move j^th step
l_id = self.canvas.create_line(
end_xx, end_yy, end_xx + self.center_dist * dist *
cos(radians(self.curr_angle - 60)),
end_yy + self.center_dist * dist *
sin(radians(self.curr_angle - 60)))
self.curr_angle -= 60

def create_textbox(self):
txt = Text(self.canvas,
width=80,
height=1,
font=("Helvatica", 12),
padx=10,
pady=10)
txt.tag_configure("center", justify="center")
txt.insert("1.0", "Select a Hexagon")
txt.tag_add("center", "1.0", "end")
self.canvas.create_window((0, 600), anchor='w', window=txt)
txt.config(state=DISABLED)
self.textbox = txt
def resets(self, event):
if event.char == 'R':
self.reset_grid()
# clear hexagonal grid for new i/p
def reset_grid(self, button_reset=False):
self.first_click = True
self.curr_angle = 330
self.curr_count = 0
self.co_cell_endp = []
self.reuse_list = []
for i in self.hexagons:
self.canvas.itemconfigure(i.tags, fill=i.color)

try:
self.line_ids
except AttributeError:
pass
else:
for i in self.line_ids:
self.canvas.after(0, self.canvas.delete, i)
self.line_ids = []
if button_reset:
self.write_text("Select a Hexagon")
# create a grid of Hexagons
def create_grid(self, cols, rows):
size = self.edge_len
for c in range(cols):
if c % 2 == 0:
offset = 0
else:
offset = size * sqrt(3) / 2
for r in range(rows):
x = c * (self.edge_len * 1.5) + 50
y = (r * (self.edge_len * sqrt(3))) + offset + 15
hx = Hexagon(self.canvas, x, y, self.edge_len, "#fafafa",
"{},{}".format(r, c))
self.hexagons.append(hx)
# calculate reuse distance, center distance and radius of the hexagon

def cluster_reuse_calc(self):
self.hex_radius = sqrt(3) / 2 * self.edge_len
self.center_dist = sqrt(3) * self.hex_radius
self.reuse_dist = self.hex_radius * sqrt(3 * self.cluster_size)
def write_text(self, text):
self.textbox.config(state=NORMAL)
self.textbox.delete('1.0', END)
self.textbox.insert('1.0', text, "center")
self.textbox.config(state=DISABLED)
#check if the co-channels are within visible canvas
def is_within_bound(self, coords):
if self.TOP_LEFT[0] < coords[0] < self.BOTTOM_RIGHT[0]
and self.TOP_RIGHT[1] < coords[1] < self.BOTTOM_RIGHT[1]:
return True
return False
#gets called when user selects a hexagon
#This function applies frequency reuse logic in order to
#figure out the positions of the co-channels
def call_back(self, evt):
selected_hex_id = self.canvas.find_closest(evt.x, evt.y)[0]
hexagon = self.hexagons[int(selected_hex_id - 1)]
s_x, s_y = hexagon.x, hexagon.y
approx_center = (s_x + 15, s_y + 25)

if self.first_click:
self.first_click = False
self.write_text(
"""Now, select another hexagon such
that it should be a co-cell of
the original hexagon."""
)
self.co_cell_endp.append(approx_center)
self.canvas.itemconfigure(hexagon.tags, fill="green")
for _ in range(6):
end_xx = approx_center[0] + self.center_dist * i * cos(
radians(self.curr_angle))
end_yy = approx_center[1] + self.center_dist * i * sin(
radians(self.curr_angle))
reuse_x = end_xx + (self.center_dist * j) * cos(
radians(self.curr_angle - 60))
reuse_y = end_yy + (self.center_dist * j) * sin(
radians(self.curr_angle - 60))
if not self.is_within_bound((reuse_x, reuse_y)):
self.write_text(
"""co-cells are exceeding canvas boundary.
Select cell in the center"""
)
self.reset_grid()

break
if j == 0:
self.reuse_list.append(
self.canvas.find_closest(end_xx, end_yy)[0])
elif i >= j and j != 0:
self.reuse_list.append(
self.canvas.find_closest(reuse_x, reuse_y)[0])
self.co_cell_endp.append((end_xx, end_yy))
self.curr_angle -= 60
else:
curr = self.canvas.find_closest(s_x, s_y)[0]
if curr in self.reuse_list:
self.canvas.itemconfigure(hexagon.tags, fill="green")
self.write_text("Correct! Cell {} is a co-cell.".format(
hexagon.tags))
if self.curr_count == len(self.reuse_list) - 1:
self.write_text("Great! Press Shift-R to restart")
self.show_lines()
self.curr_count += 1
else:
self.write_text("Incorrect! Cell {} is not a co-cell.".format(
hexagon.tags))
self.canvas.itemconfigure(hexagon.tags, fill="red")

if __name__ == '__main__':
print(
"""Enter i & j values. common (i,j) values are:
(1,0), (1,1), (2,0), (2,1), (3,0), (2,2)"""
)
i = int(input("Enter i: "))
j = int(input("Enter j: "))
if i == 0 and j == 0:
raise ValueError("i & j both cannot be zero")
elif j > i:
raise ValueError("value of j cannot be greater than i")
else:
N = (i**2 + i * j + j**2)
print("N is {}".format(N))
freqreuse = FrequencyReuse(cluster_size=N)
freqreuse.mainloop()

OUTPUT:
Useful Study links-
1. Mobile Communication –
https://www.youtube.com/watch?v=tt1-
Ohe9QQU&list=RDCMUCpuCKBmQA70bNy39-
VJU_4g&index=2
2. Frequency Reuse - Cell Splitting - Handoff Procedure
https://www.youtube.com/watch?v=ioj6F1v59yw
3. How Mobile Phone Works
https://www.youtube.com/watch?v=1JZG9x_VOwA
4. Cellular Concepts
https://www.tutorialspoint.com/umts/umts_cellular_c
oncepts_introduction.htm

Noise & its Effects On Mobile
In any communication system, during the transmission of the signal, or while
receiving the signal, some unwanted signal gets introduced into the
communication, making it unpleasant for the receiver, questioning the quality
of the communication. Such a disturbance is called as Noise.
What is Noise?
Noise is an unwanted signal which interferes with the original message signal
and corrupts the parameters of the message signal. This alteration in the
communication process, leads to the message getting altered. It is most likely
to be entered at the channel or the receiver.
The noise signal can be understood by taking a look at the following example.
Hence, it is understood that noise is some signal which has no pattern and no constant
frequency or amplitude. It is quite random and unpredictable. Measures are usually taken to
reduce it, though it can’t be completely eliminated.
Most common examples of noise are –
 Hiss sound in radio receivers
 Buzz sound amidst of telephone conversations
 Flicker in television receivers, etc.

Effects of Noise
Noise is an inconvenient feature which affects the system performance. Following are the
effects of noise.
Noise limits the operating range of the systems
Noise indirectly places a limit on the weakest signal that can be amplified by an amplifier.
The oscillator in the mixer circuit may limit its frequency because of noise. A system’s
operation depends on the operation of its circuits. Noise limits the smallest signal that a
receiver is capable of processing.
Noise affects the sensitivity of receivers
Sensitivity is the minimum amount of input signal necessary to obtain the specified quality
output. Noise affects the sensitivity of a receiver system, which eventually affects the
output.
Types of Noise
The classification of noise is done depending on the type of the source, the effect it shows or
the relation it has with the receiver, etc.
There are two main ways in which noise is produced. One is through some external
source while the other is created by an internal source, within the receiver section.
External Source
This noise is produced by the external sources which may occur in the medium or channel of
communication, usually. This noise cannot be completely eliminated. The best way is to
avoid the noise from affecting the signal.
Examples
Most common examples of this type of noise are −
 Atmospheric noise (due to irregularities in the atmosphere).
 Extra-terrestrial noise, such as solar noise and cosmic noise.
 Industrial noise.
Internal Source
This noise is produced by the receiver components while functioning. The components in
the circuits, due to continuous functioning, may produce few types of noise. This noise is
quantifiable. A proper receiver design may lower the effect of this internal noise.
Examples

Most common examples of this type of noise are −
 Thermal agitation noise (Johnson noise or Electrical noise).
 Shot noise (due to the random movement of electrons and holes).
 Transit-time noise (during transition).
 Miscellaneous noise is another type of noise which includes flicker, resistance effect
and mixer generated noise, etc.
Signal to Noise Ratio
Signal-to-Noise Ratio (SNR) is the ratio of the signal power to the noise power. The
higher the value of SNR, the greater will be the quality of the received output.
Figure of Merit
The ratio of output SNR to the input SNR can be termed as the Figure of merit (F). It is
denoted by F. It describes the performance of a device.
CDMA vs. GSM
Difference between CDMA and GSM
Cellular mobile services have been used all over the world for a long time and still evolving
day by day. With these services, various communication services also evolved, and CDMA
and GSM are two of them. CDMA and GSM are the two most important technology
standards that are known for mobile communication. Both the GSM and CDMA converts the
data from the mobile phone into radio waves. But these technologies are differentiated in the
way in which the calls & data transfer takes place over a network. One of the key differences
between CDMA and GSM is that GSM uses SIM cards to connect a mobile phone with its
network, whereas CDMA does not need any SIM card and operates on ESNs (Electronic
Serial Number). In this topic, we will understand what GSM and CDMA technologies are
and how they differentiate from each other in detail.
What is GSM?
o GSM or Global System for Mobile Communication is a digital mobile
communication standard, which is used for transmitting and receiving data and voice
signals over a network.
o It is also known as the second-generation standard for mobile networks or
telecommunication, and it operates on a wedge spectrum.
o GSM uses the TDMA (Time Division Multiple Access) and FDMA (Frequency
Division Multiple Access) for separating the users & cells and transmitting the
signals.

o Due to the GSM standard, various other wireless services such as GPRS(General
Packet Radio Service), UMTS(Universal Mobile Radio System), and
EDGE(Enhanced Data Rates for GSM Evolution) have also evolved.
o It operates on three different radio frequencies, which are 900MHz, 1800MHz, and
1900MHz.
o Among these three frequencies, the 900MHz band frequency is used by the Original
GSM system, and the 1800 MHz band frequency is used to provide the added support
for increasing customers. The 1900MHz band is specifically used in the US (United
States).
o The GSM users have first taken advantage of the service Short Message System
(SMS), by which the users can communicate with each other using text messages over
the given network.
Advantages of GSM
o With GSM technology, we can have a low-cost mobile set and base stations.
o It improves spectrum efficiency.
o The data or voice signals are of high quality in GSM.
o The GSM is compatible with ISDN (Integrated Services Digital Network)
What is CDMA?
o CDMA is an acronym for Code Division Multiple Access, which is also a radio
telecommunication standard similar to GSM.

o The CDMA came into existence in 2G and 3G generation as the protocol of wireless
communication.
o It is based on the spread spectrum technology and makes optimal use of the
available bandwidth. Since it uses the spread spectrum technology, hence allows each
user to transmit the data over the entire frequency spectrum at any time.
o The CDMA provides one of the most secure modes of communication due to its
spread spectrum property.
o It is used in UHF or Ultra high-frequency cellular systems, with frequency bands
ranging from 800MHz to 1900MHz.
Advantages of CDMA:
o It uses a fixed frequency spectrum in an efficient way.
o There is no limit on the number of Users.
o It provides a flexible allocation of resources.
o It is compatible with other cellular technologies; hence it allows nation-wide roaming.
Differences Between GSM and CDMA
1. Technology Used
The GSM is based on the wedge spectrum technology, also known as a carrier. This carrier is
split into various time slots on the basis of TDMA technology, and each time slots are
assigned to each user. Due to this, until one outgoing call is finished, no other user can access
that slot. It uses FDMA to provide multiuser access by dividing the user frequencies.
On the other hand, CDMA uses the spread spectrum technology and hence it makes optimal
use of the available bandwidth. It enables each user to transfer the data over the entire
frequency spectrum at any time.
2. SIM Cards
SIM (Subscriber Identity Module) is a smart card that contains the user identification
information to identify the subscriber on a telephony device. In a GSM-based phone, a SIM
card is required to make the data or call transmission. These cards can be easily replaced
from one mobile phone to another with saved information.
On the other hand, CDMA based devices do not require a SIM card; instead, it uses ESN
(Electronic Serial Number). Since it does not use a SIM card, hence changing a device from
another is difficult and required a proper procedure.

3. Flexibility
The GSM standard is more flexible as compared to CDMA. It is because, in GSM, the SIM
card can be inserted into any device and can be used. Whereas, CDMA mobile phone can
only be used if ESN is registered in its database.
If a CDMA stops working on a phone, we need to buy the new phone, whereas if a SIM stops
working, we can use another SIM rather than changing the phone.
4. Spectrum frequencies
The GSM works on the frequency spectrum ranging from 850 MHz to 1900 MHz, whereas
CDMA also operates in the frequency range of 850MHz and 1900MHz.
5. Radiation Exposure
In GSM phones, there is 28 times more radiation exposure takes place as compared to
CDMA phones.
GSM phone continuously transmits wave pulses, whereas CDMA phones do not continuously
produce such pulses.
6. Global Reach
GSM is more used globally as compared to CDMA technology. Approx. 80% of the mobile
networks across 210 countries use GSM compared to CDMA. The CDMA-based mobile
phones are mostly used in the US, Canada, and Japan.
7. Security
The CDMA provides more security as compared to GSM technology because it has inbuilt
encryption and uses the spread spectrum for data transmission.
In CDMA, the signal detection is much difficult than in GSM. Hence it is more secure.
8. Data Transfer Rate
The data transfer rate is high in CDMA compared to GSM technology. In CDMA, EVDO
data transfer technology is used, which provides a maximum download speed of 2 Mbps.
On the other hand, GSM uses EDGE data transfer technology that provides a maximum
download speed of 384 Kbps, which is much slower than CDMA.

How to check if the phone is based on GSM or CDMA
technology?
To check if your mobile phone is GSM-based or CDMA based, check the below points:
1. Check from your Phone Settings:
o For iPhone users: Go to Settings→General→About→ check for the MEID, ESN, or
IMEI number near the bottom of the menu.
o For Android users: Go to Settings→ System→About Phone→Click to Status, and
check for the MEID, ESN, or IMEI number.
In both cases, if you see the MEID or ESN number, then your phone is CDMA based. If you
see the IMEI number, then your phone is a GSM-based phone. If you see both options, it
means your device supports both technologies.
2. Check for SIM card Slot on the Phone:
As discussed above, the GSM phone makes use of SIM cards, whereas CDMA not. So, you
can check on your mobile phone whether it contains a SIM slot or not. But due to widely
spread of 4G LTE technology, most CDMA devices also use SIM cards, so this way of
checking is less helpful now.
Comparison Chart between CDMA and GSM
CDMA GSM
It stands for Code Division
Multiple Access.
It stands for Global System for
Mobile Communication.
It uses a CDMA mechanism for
data & call transmission.
It uses TDMA and FDMA
mechanism for data & voice
transmission.
The transmission rate is fast
compared to GSM.
The transmission rate is slow
compared to CDMA.
It uses EVDO data transfer It uses EDGE data transfer

technology. technology.
It is handset specific and does not
require any SIM for
communication.
It is SIM specific, hence requires a
SIM card for communication.
During transmission, it is much
prone to radiation emission.
During transmission, it is
comparatively less prone to
radiation emission.
It offers more secure
communication compared to GSM.
It offers less secure
communication compared to
CDAM.
The signal detection is difficult in
CDMA.
The signal detection is easy in
GSM.
It provides built-in encryption. It requires additional encryption as
no built-in encryption is available.
It enables limited roaming. It enables worldwide roaming.
Conclusion:
Both GSM and CDMA have their own importance and depends on how both
technologies are being used. Approximately 80% of the world uses GSM, and
CDMA is used mostly in the US and somewhere in Canada and Japan.

Difference between GSM and CDMA
GSM stands for Global System for Mobile communication, while CDMA stands
for Code Division Multiple Access GSM uses FDMA (Frequency division multiple
access) and TDMA (Time division multiple access). GSM supports transmitting data
and voice both at once, but CDMA have not this feature.
The main distinction between GSM and CDMA is that in GSM, the customer
information is put on a SIM card which can be moved to a new mobile phone.
Whereas only mobile phones from a set of whitelisted companies can be used with a
CDMA network.
The differences between GSM and CDMA are as follows:
Serial No. GSM CDMA
1. Full form Global System for Mobile
communication.
Code Division Multiple
Access.
2. Technology
used
FDMA(Frequency division multiple
access) and TDMA (Time division
multiple access).
CDMA(Code division
multiple access).
3. Availability GSM is globally widely used and
available.
CDMA is available in
fewer countries and
carriers.
4. Data speed
rate
42Mbps in HSPA (3G). 3.6Mbps in CDMA.
5.Features GSM supports transmitting data and
voice both at once.
CDMA does not support
this feature.
6. Customer
Information
Stored in a SIM card. Stored in a headset or
phone.

The GSM architecture
The GSM architecture consists of three major interconnected subsystems that interact with
themselves and with users through certain network interface. The subsystems are Base
Station Subsystem (BSS), Network Switching Subsystem (NSS) and Operational Support
Subsystem (OSS). Mobile Station (MS) is also a subsystem but it is considered as a part of
BSS.
1. Mobile Station (MS): Mobile Station is made up of two entities.
A. Mobile equipment (ME):
 It is a portable, vehicle mounted, hand held device.
 It is uniquely identified by an IMEI number.
 It is used for voice and data transmission. It also monitors power and signal quality of
surrounding cells foe optimum handover. 160 characters long SMS can also be sent
using Mobile Equipment.
B. Subscriber Identity module (SIM):
 It is a smart card that contains the International Mobile Subscriber Identity (IMSI)
number.
 It allows users to send and receive calls and receive other subscriber services. - It is
protected by password or PIN.
 It contains encoded network identification details. it has key information to activate
the phone.
 It can be moved from one mobile to another.
2. Base Station Subsystem (BSS): It is also known as radio subsystem, provides
and manages radio transmission paths between the mobile station and the Mobile Switching
Centre (MSC). BSS also manages interface between the mobile station and all other
subsystems of GSM. It consists of two parts.

A. Base Transceiver Station (BTS):
 It encodes, encrypts, multiplexes, modulates and feeds the RF signal to the antenna.
 It consists of transceiver units.
 It communicates with mobile stations via radio air interface and also communicates
with BSC via Abis interface.
B. Base Station Controller (BSC):
 It manages radio resources for BTS. It assigns frequency and time slots for all mobile
stations in its area.
 It handles call set up, transcoding and adaptation functionality handover for each MS
radio power control.
 It communicates with MSC via A interface and also with BTS.
3. Network Switching Subsystem (NSS): it manages the switching functions
of the system and allows MSCs to communicate with other networks such as PSTN and
ISDN. It consist of
A. Mobile switching Centre:
 It is a heart of the network. It manages communication between GSM and other
networks.
 It manages call set up function, routing and basic switching.
 It performs mobility management including registration, location updating and inter
BSS and inter MSC call handoff.
 It provides billing information.
 MSC does gateway function while its customers roam to other network by using
HLR/VLR.
B. Home Location Registers (HLR): - It is a permanent database about mobile
subscriber in a large service area. - Its database contains IMSI, IMSISDN, prepaid/post-paid,
roaming restrictions, supplementary services.
C. Visitor Location Registers (VLR): - It is a temporary database which updates
whenever new MS enters its area by HLR database. - It controls mobiles roaming in its area.
It reduces number of queries to HLR. - Its database contains IMSI, TMSI, IMSISDN, MSRN,
location, area authentication key.
D. Authentication Centre: - It provides protection against intruders in air interface. - It
maintains authentication keys and algorithms and provides security triplets (RAND, SRES,
Ki).
E. Equipment Identity Registry (EIR):
 It is a database that is used to track handset using the IMEI number.
 It is made up of three sub classes- the white list, the black list and the gray list.


4. Operational Support Subsystem (OSS): It supports the operation and
maintenance of GSM and allows system engineers to monitor, diagnose and troubleshoot all
aspects of GSM system. It supports one or more Operation Maintenance Centres (OMC)
which are used to monitor the performance of each MS, Bs, BSC and MSC within a GSM
system. It has three main functions:
 To maintain all telecommunication hardware and network operations with a particular
market.
 To manage all charging and billing procedures
 To manage all mobile equipment in the system.
Interfaces used for GSM network :
1)UM Interface –Used to communicate between BTS with MS
2)Abis Interface— Used to communicate BSC TO BTS
3)A Interface-- Used to communicate BSC and MSC
4) Singling protocol (SS 7)- Used to communicate MSC with other network .
GSM Services-
GSM offers much more than just voice telephony. Contact your local GSM network
operator to the specific services that you can avail.
GSM offers three basic types of services −
 Telephony services or teleservices
 Data services or bearer services
 Supplementary services
Teleservices
The abilities of a Bearer Service are used by a Teleservice to transport data. These services
are further transited in the following ways −

Voice Calls
The most basic Teleservice supported by GSM is telephony. This includes full-rate speech at
13 kbps and emergency calls, where the nearest emergency-service provider is notified by
dialing three digits.
Videotext and Facsmile
Another group of teleservices includes Videotext access, Teletex transmission, Facsmile
alternate speech and Facsmile Group 3, Automatic Facsmile Group, 3 etc.
Short Text Messages
Short Messaging Service (SMS) service is a text messaging service that allows sending and
receiving text messages on your GSM mobile phone. In addition to simple text messages,
other text data including news, sports, financial, language, and location-based data can also
be transmitted.
Bearer Services
Data services or Bearer Services are used through a GSM phone. to receive and send data is
the essential building block leading to widespread mobile Internet access and mobile data
transfer. GSM currently has a data transfer rate of 9.6k. New developments that will push up
data transfer rates for GSM users are HSCSD (high speed circuit switched data) and GPRS
(general packet radio service) are now available.
Supplementary Services
Supplementary services are additional services that are provided in addition to teleservices
and bearer services. These services include caller identification, call forwarding, call
waiting, multi-party conversations, and barring of outgoing (international) calls, among
others. A brief description of supplementary services is given here −

 Conferencing − It allows a mobile subscriber to establish a multiparty conversation,
i.e., a simultaneous conversation between three or more subscribers to setup a
conference call. This service is only applicable to normal telephony.
 Call Waiting − This service notifies a mobile subscriber of an incoming call during a
conversation. The subscriber can answer, reject, or ignore the incoming call.
 Call Hold − This service allows a subscriber to put an incoming call on hold and
resume after a while. The call hold service is applicable to normal telephony.
 Call Forwarding − Call Forwarding is used to divert calls from the original recipient
to another number. It is normally set up by the subscriber himself. It can be used by
the subscriber to divert calls from the Mobile Station when the subscriber is not
available, and so to ensure that calls are not lost.
 Call Barring − Call Barring is useful to restrict certain types of outgoing calls such
as ISD or stop incoming calls from undesired numbers. Call barring is a flexible
service that enables the subscriber to conditionally bar calls.
 Number Identification − There are following supplementary services related to
number identification −
o Calling Line Identification Presentation − This service displays the
telephone number of the calling party on your screen.
o Calling Line Identification Restriction − A person not wishing their number
to be presented to others subscribes to this service.
o Connected Line Identification Presentation − This service is provided to
give the calling party the telephone number of the person to whom they are
connected. This service is useful in situations such as forwarding's where the
number connected is not the number dialed.
o Connected Line Identification Restriction − There are times when the
person called does not wish to have their number presented and so they
would subscribe to this person. Normally, this overrides the presentation
service.
o Malicious Call Identification − The malicious call identification service was
provided to combat the spread of obscene or annoying calls. The victim
should subscribe to this service, and then they could cause known malicious
calls to be identified in the GSM network, using a simple command.
 Advice of Charge (AoC) − This service was designed to give the subscriber an
indication of the cost of the services as they are used. Furthermore, those service
providers who wish to offer rental services to subscribers without their own SIM can
also utilize this service in a slightly different form. AoC for data calls is provided on
the basis of time measurements.
 Closed User Groups (CUGs) − This service is meant for groups of subscribers who
wish to call only each other and no one else.
 Unstructured supplementary services data (USSD) − This allows operator-defined
individual services.

Different Modes used for Mobile
Communication
Learn the answer by reading our in-depth guide to wireless technologies.
1. Satellite Communication
Satellite communication is a crucial form of wireless communication.
By means of satellites, people all over the earth can communicate
with each other.
It may not be possible to send a signal to another country because,
well, the curvature of the earth is in the way. This is one reason why
satellites are orbiting the earth because they can send a signal amongst
themselves and eventually to the distant country. All of this at an
incredibly fast speed. NASA and other space agencies make regular
use of this type of technology. Of course, sending a satellite into the
atmosphere is not cheap. Therefore the technology involved must be
subjected to significant testing before launch.

2. Infrared Communication
Infrared communication is present in most homes in the form of a
television remote control. However, how does it work?IR transmits
information by means of invisible light. This means that on the
electromagnetic spectrum it lies between microwaves and visible
light. Infrared communication requires a transmitter and a
photoreceiver to receive the light beam. Since any disruption to the
light will result in the photoreceiver not receiving it, IR will only
function when there is a line of sight visibility. That means that if you
stand between the transmitter and receiver it will probably not work.

4. Broadcast Radio
The most famous form of wireless transmission on our list, broadcast
radio, was probably the first kind of wireless communication.
Radio transmitters send out data in the form of radio waves to
receiving antennae. Radio waves are forms of electromagnetic
signals. Signals are relatively narrow, and waves can be sent across
various frequencies. This is why your car radio is able to receive
signals from many different radio stations.
There are many types of users of radio communication. Radio stations
that send out informative and entertaining programs. Maritime radio
channels allow ships to communicate with each other and the shore.
Ham radio enthusiasts are able to communicate and use radio
communication for personal use.

4. Microwave Communication
Microwave technology is an effective type of communication that is used globally.
This technology can be broken down into 2 types
Satellite Microwave Communication
This is the most effective method of transmitting microwaves globally. Like Infrared
technologies, Microwave technologies require a clear line of sight. This means that if
you want to send a signal over a long distance, sending it up to a satellite first is a
good idea.
The only problem is that in very dense cloudy weather the signal to the satellite can be
blocked by atmospherics.
Terrestrial Microwave Communication
Microwave technologies can be a very secure form of communication. If a signal
needs to be transmitted over a short distance, it can be enough to erect two antennae
with a clear line of sight. The signal can then be transmitted between the two
receivers. This negates the need to connect to an outside network.

5. Wi-Fi
Wi-Fi internet is a low powered wireless electronic network. These
are available in almost every shopping mall and cafe in the world.
Essentially a physical wired network is connected to a router. This
creates a highly localized and low power wireless network.
From this, it is possible to connect a range of devices to the local
network. However, public wireless internet access is known to be a
target for thieves and hackers. Therefore, it is essential that both users
who connect to these networks and the providers use password
protection defense methods.

6.Mobile Communication Systems
The burgeoning mobile phone industry uses similar technology to Wi-
Fi but on a much grander and safer scale. Mobile phone companies
provide coverage to customers nationwide or even international
scale.
They do this by means of a complex blend of local networks and
transmitters together with satellite support.

7.Bluetooth Technology
Bluetooth is a relatively new technology but is becoming more and
more prevalent. It is essentially a simple method to send information
across a short distance. However, this information can include either
messages or even files.
Bluetooth technology was originally designed to be a replacement for
physical cables. However, it does have its downsides. It has a
maximum reach of 30 feet. This can be reduced further, but not
entirely blocked by walls and other solid items.

Architecture of Mobile Computing(3 tier)
A 3-tier architecture is an application program that is organized into three major
parts, comprising of:
 The data access layer tier at the bottom,
 The application tier (business logic) in the middle and
 The client tier (presentation) at the top.

Each tier is distributed to a different place or places in a
network. These tiers do not necessarily correspond to physical
locations on various computers on a network, but rather to logical
layers of the application.
1. Presentation Layer (UI):
 This layer presents data to the user and optionally permits data
manipulation and data entry, also this layer requests the data
form Business layer.
 This layer accomplished through use of Dynamic HTML and
client-side data sources and data cursors.
2. Business Logic Layer:
 The business logic acts as the server for client requests from
workstations. It acts according Business rules fetch or insert data
through the Data Layer.
 In turn, it determines what data is needed (and where it is
located) and acts as a client in relation to a third tier of

programming that might be located on a local or mainframe
computer.
 Because these middle-tier components are not tied to a specific
client, they can be used by all applications and can be moved to
different locations, as response time and other rules require.
3. Data Access Layer:
 The third tier of the 3-tier system is made up of the DBMS that
provides all the data for the above two layers.
 This is the actual DBMS access layer.
 Avoiding dependencies on the storage mechanisms allows for
updates or changes without the application tier clients being
affected by or even aware of the change.

Mobile technology-Unit 1

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