Kingston University CI7110 Data Communications Report Analysis

This report, prepared for Kingston University's CI7110 Data Communications course, delves into the critical aspects of data communication, emphasizing digital communication, TCP/IP networks, and network security protocols. The report begins with an overview of the evolution of communication methods, highlighting the shift from traditional methods to modern digital techniques. It explores the advantages of digital communication, including its immunity to distortion and interference, and the flexibility in hardware implementation. The report then examines the modulation and demodulation of digital signals, detailing various modulation schemes such as amplitude shift keying, phase shift keying, and frequency shift keying. Furthermore, it discusses network protocol suites, including the TCP/IP protocol layering, and the functionalities of Local Area Networks (LANs). The report provides a comprehensive analysis of the underlying principles and technologies that facilitate efficient and secure data transmission.

KINGSTON UNIVERSITY
FACULTY OF SCIENCE, ENGINEERING AND COMPUTING
CI7110 DATA COMMUNICATIONS
TITLE
COURSEWORK
STUDENT NAME
STUDENT REGISTRATION NUMBER
PROFESSOR (TUTOR)
DATE OF SUBMISSION

ABSTRACT
Researchers are constantly seeking better techniques to ensure that there is improved data
communication especially in the areas of transmission and reception of data sent over digital
communication equipment. Data communication has a long history and is constantly being
improved using the different innovations and technologies being developed. The data
communication field is quite broad and the users are spoilt for choice as more and more
technologies have been developed to ease communication especially over long distances. This
paper seeks to address the aspects of data communication such as the digital communication,
TCP/IP networks and the network security protocols. Communities in the traditional age used
different methods to communicate to each other. Some of the common modes were smoke
signals, messengers, drums, and bottles over the sea. There are a number of caveats that can be
isolated with such methods but the key drawback was on the unreliability of the communication
mode. Information needs to be received as it was transmitted. There should be no distortion or
lack of communication thereof. This paper discusses the modern techniques that have been
employed in seeking the reliability, availability, and efficiency.
Keywords: Data communication, digital communication, mobile networks, satellite
communication, information efficiency, network security, internet networks, encryption, trends
and advances.

INTRODUCTION
Communication aims at ensuring the transfer of
information from the sender to the recipient. The
legacy communication scheme includes the
sender, transmitter point, channel of
communication, receiver point, and the
recipient. Usually, in a real-life application the
source can either be analog or digital. For
instance, a temperature and humidity sensor,
DHT22 would like to collect the environmental
status in terms of temperature and humidity, the
values are analog in nature. Analog inputs are
usually converted to digital values for analysis
and transmission. The transmitter can be used to
transmit voice, data, video, or any multi-media
information from the source.
Some of the major communication systems used
globally are:
(i) The public switched telephone
network
(ii) Satellite systems
(iii) Radio and TV broadcasting
(iv) Cellular phones
(v) Computer networks such as
LANs, WANs, and WLANs.
For transmission of information, these systems
convert information into either electrical,
electromagnetic and optical signals that are
appropriate for the transmission medium or
channel of communication.
History of digital systems
Communities in the traditional age used
different methods to communicate to each
other. Some of the common modes were
smoke signals, messengers, drums, and
bottles over the sea. There are a number of
caveats that can be isolated with such
methods but the key drawback was on the
unreliability of the communication mode.
Information needs to be received as it was
transmitted.
Digital signals and spectra
Digital systems convert their bit symbols into
signals for transmission while the analog
systems convert analog messages to signals for
propagation of information over the channels.

Many of the modern communication systems are
using the digital techniques to distinguish
between discrete symbols which allows for the
regeneration of signals as opposed to
amplification. When the signals fail to amplify,
the system is useful for data compression or
source coding, error correction or channel
coding, equalization and security. One can easily
mix and retrieve signals and data carried over
the signals using digital techniques. Once the
signals are received on the receiver’s end, the
receiver recreates the signals or bits from
received signals so as to mitigate the channel
effects. The performance metric for analog
systems is fidelity, for digital it is the bit rate
and error probability.
Over the years, innovators and researchers have
ascertained that digital communications are east
to regenerate the distorted signal and regenerate
repeaters along the transmission path that can
detect a digital signal and retransmit the signal
without errors. Unfortunately, that is not
possible with the analog communication
systems. The digital signals are immune to
distortion and interference. The digital
communication is rugged in the sense that it is
more immune to channel noise and distortion.
The digital hardware implementation tends to be
flexible and it permits the use of
microprocessors or the mini-processors such as
Arduino boards and PLC, they have a shorter
design and production cycle hence they tend to
meet the economies of scale. The component
designs use the LSI and VLSI such that the cost
of production lowers even further. Digital
communication systems allow for multiplexing
using techniques such as the time and code
division multiple access unlike the frequency
division multiple access which is used by the
analog systems of communication. More
advantages are obtained from the utilization of
digital techniques, such that one can combine
the formats for transmission through a common
medium. The most common baud rate is 9600
for communication system. It is the rate at which
the signaling elements are transmitted and the
probability that one of the bits is in error is the
bit error rate. These two terms are used in the
performance study of the digital signals.

Modulation and demodulation of digital
signals
When the digital signals are obtained at the
transmission point, the technical team must
figure out how the modulation of digital data
will be performed. The modulation converts
the digital data or a low-pass analog to band-
pass analog signal. The carrier frequency
acts as a basis for the information signal
hence it is the modulating signal. The digital
signal strength is represented in binary form
in either 1 or 0. The signal can be modulated
by varying its primary parameters such as
amplitude, frequency, or the phase angle.
The demodulation tends to be simple when
the modulated signal reaches the receiver’s
point. Bandpass modulation is the process
by which some characteristics of a
sinusoidal waveform is varied according to
the message signal. Modulation shifts the
spectrum of a baseband signal to some high
frequency. For the bandpass modulation
techniques, the magnitude and phase of the
signal are altered. The bandpass signal can
be represented as,
s ( t )=A ( t ) cos [ θ ( t ) ]= A ( t ) cos ( ω0 t +ϕ ( t ) )
The real valued signal is represented as the
magnitude as the A(t) and the generalized
angle as the phase is involved. The
modulated signal can represent information
through changing three parameters of the
signal in Amplitude shift keying, phase shift
keying, and frequency shift keying. The
amplitude phase shift keying is obtained as,
s ( t ) =A ( t ) cos [ θ ( t ) ] = A ( t ) cos ( ω0 t+ φ )
Its instantaneous frequency can be expressed
as,
ωi ( t ) = dθ ( t )
dt =ω0
Or
θ ( t ) =∫
−∞
t
ωi ( α ) dα
The phase shift keying technique modulates
the phase of a signal such that,
θ ( t ) =ωC t +K p m ( t )
sPM ( t )= Acos [ ωc t+ K p m ( t ) ]

ωi ( t ) = dθ ( t )
dt =ωc + K p m' ( t )
Where,
α ( t ) =∫
−∞
t
m( α)dα
Frequency is adjusted usually in the analog
systems,
SFM =A { cos ( ω0 t ) −Kf a ( t ) sin ( ω0 t ) }
For the complex envelope messages,
St =ℜ [ g ( t ) exp ( j ω0 t ) ]
It is crucial to consider the complex
envelope and M&P forms to transform from
the complex envelope to magnitude or
phase. The digital signals with a modulation
greater than two are referred to as binary
signals. There are several modulation
schemes such as the binary amplitude shift
keying, binary phase shift keying, and the
binary frequency shift keying.
For the binary frequency shift keying, there
are two different frequencies that are used to
transmit binary information. The data is
encoded in the frequencies and the
modulation or message signal is used to
select from the given frequencies. One is
used as the mark frequency while the other
is the space frequency.
S0 ( t ) =Ac cos ( ω1 t+ ϕ1 )
S1 ( t ) =Ac cos ( ω2 t+ ϕ2 )
During the phase shift keying, the phase of
the carrier signal is switched between two or
more in response to the baseband signal
modulator.
Network protocol suites
Communication and data sharing are key
components in the digital communication
systems. The computer network is a
collection of the various computing devices
which are connected in various ways in
order to communicate and share resources.
These resources can either be hardware or
software. The connections between
computers in a network are made using the
physical wires or cables. Some connections
are wireless and as such they use the
wireless forms of media to transmit the
information. Some of the media are radio

waves or infrared signals. The data transfer
rate is the speed with which the data moves
from one point to the other on the network.
The data transfer rate is the key issue in
computer networks as there are a lot of
overhead involved which consumes time
and throughput. These networks tend to
have opened up an entire frontier in the
world of computing which is known as the
client server model. This is the most recent
advancement in the computer networks
which allows the client machine to request
for services from the server and the server
responds. In such cases, a file server is used
as the computer that stores and manages the
files for multiple users on a network. The
web server is a computer dedicated to
responding to requests for webpages. A
Local Area Network is a network that
connects a relatively small number of
machines in a relatively close or small
geographical area. There are various
topologies used to administer the local area
network. Some of the common topologies
are:
(i) Ring topology which
connects all the nodes in a closed
loop on which messages travel in one
direction as a token.
(ii) The star topology centers
around one node to which all other
nodes are connected through and via
which all messages are sent. It forms
the backbone of the client-server
model.
(iii) The Bus topology has all the
nodes connected to a single
communication line that carries
messages in both directions. The
most prevalent bus technology is
known as the ethernet and is used as
the industry standard for the local
area networks.
TCP/IP protocol layering
The protocol stack used on the
Internet is the Internet Protocol Suite. It is

usually called TCP/IP after two of its most
prominent protocols, but there are other
protocols as well. The TCP/IP model is
based on a five-layer model for networking.
The TCP/IP protocol stack models a series
of protocol layers for networks and systems
that allows communications between any
types of devices. The model consists of five
separate but related layers, as shown below,
In TCP/IP, as with most layered
protocols, the most fundamental elements of
the process of sending and receiving data are
collected into the groups that become the
layers. Each layer’s major functions are
distinct from all the others, but layers can be
combined for performance reasons. Each
implemented layer has an interface with the
layers above and below it, except for the
application and physical layers, and provides
its defined service to the layer above and
obtains services from the layer below. In
other words, there is a service interface
between each layer, but these are not
standardized and vary widely by operating
system. TCP/IP is designed to be
comprehensive and flexible. It can be
extended to meet new requirements, and has
been. Individual layers can be combined for
implementation purposes, as long as the
service interfaces to the layers remain intact.
Layers can even be split when necessary,
and new service interfaces defined. Services
are provided to the layer above after the
higher layer provides the lower layer with
the command, data, and necessary
parameters for the lower layer to carry out
the task. Layers on the same system provide
and obtain services to and from adjacent
layers. However, a peer-to-peer protocol
process allows the same layers on different

systems to communicate. The term peer
means every implementation of some layer
is essentially equal to all others. There is no
“master” system at the protocol level.
Communications between peer
layers on different systems use the defined
protocols appropriate to the given layer. In
other words, services refer to
communications between layers within the
same process, and protocols refer to
communications between processes. Each
layer on the sending system adds
information to the data it receives from the
layer above and passes it all to the layer
below except for the physical layer. There is
a natural grouping of the five-layer protocol
stack at the network layer and the transport
layer. The lower three layers of TCP/IP,
sometimes called the network support
layers, must be present and functional on all
systems, regardless of the end system or
intermediate node role. The transport layer
links the upper and lower layers together.
This layer can be used to make sure that
what was sent was received, and what was
sent is useful to the receiver. Each layer uses
encapsulation to add the information its peer
needs on the receiving system. The network
layer adds a header to the information it
receives from the transport at the sender and
passes the whole unit down to the data link
layer.
At the receiver, the network layer looks at
the control information, usually in a header,
in the data it receives from the data link
layer and passes the remainder up to the
transport layer for further processing. This is
called encapsulation because one layer has
no idea what the structure or meaning of the
Protocol Data Unit is at other layers. The
PDU has several more or less official names
for the structure at each layer. Although the
intermediate nodes are not shown, these
network devices will only process the data
through the first three layers. The physical
layer transmits information in electronic

form as encoded using the various encoding
techniques such as Manchester technique.
The sender and receiver must be
synchronized at the symbol level so that the
number of bits expected per unit time is the
same. In other words, the sender and
receiver clocks must be synchronized. On
modern links, the timing information is
often retrieved from the received data
stream, in bit synchronization. This
transmission rate is the number of bits per
second that can be sent. It also defines the
duration of a symbol on the wire. Symbols
usually represent one or more bits, although
there are schemes in which one bit is
represented by multiple symbols, is the data
rate.
The data link layer performs framing,
physical addressing, and error detection.
When it comes to frame error detection and
correction in the real world, error detection
bits are sometimes ignored and frames that
defy processing due to errors are simply
discarded. This does not mean that error
detection and correction are not part of the
data link layer standards: It means that in
these cases, ignoring and discarding are the
chosen methods of implementation. In
discard cases, the chore of handling the error
condition is pushed up the stack to a higher
layer protocol. the data link layer can
perform some type of flow control. Flow
control makes sure senders do not
overwhelm receivers: a receiver must have
adequate time to process the data arriving in
its buffers. At this layer, the flow control, if
provided, is link-by-link. LANs do not
usually provide flow control at the data link
layer, although they can. Not all destination
systems are directly reachable by the sender.
This means that when bits at the data link
layer are sent from an originating system,
the bits do not arrive at the destination
system as the next hop along the way.
Directly reachable systems are called
adjacent systems, and adjacent systems are

always “one hop away” from the sender.
When the destination system is not directly
reachable by the sender, one or more
intermediate nodes are needed.
The layering of TCP/IP is important if IP
packets are to run on almost any type of
network. The IP packet layer is only one
layer, and from the TCP/IP perspective, the
layer or layers below the IP layer are not as
important as the overall flow of packets
from one host to another across the network.
Layering means that you only have to adapt
one type of packet to an underlying network
type to get the entire TCP/IP suite. Once the
packet has been framed you need not worry
about TCP/UDP, or any other protocol: they
come along for the ride with the layering.
Only the IP layer has to deal with the
underlying hardware. All that really matters
is that the device at the receiving end
understands the type of IP packet
encapsulation used at the sending end. If
only one form of packet encapsulation was
used, the IP packets could remain inside the
frame with a globally unique MAC address
from source to destination. Network nodes
could forward the frame without having to
deal with the packet inside. The transport
layer of TCP/IP consists of two major
protocols: The Transmission Control
Protocol (TCP) and the User Datagram
Protocol (UDP).
TCP is a reliable layer added on top of the
best-effort IP layer to make sure that even if
packets are lost in transit, the hosts will be
able to detect and resend missing
information. TCP data units are called
segments. UDP is as best-effort as IP itself,
and UDP data units are called datagrams.
The messages that applications exchanges
are made up of strings of segments or
datagrams. Segments and datagrams are
used to chop up application content, such as
huge, multi-megabyte fi les, into more easily
handled pieces. TCP is reliable in the sense
that TCP always resends corrupt or lost

segments. This strategy has many
implications for delay-sensitive applications
such as voice or video. TCP is a connection-
oriented layer on top of the connectionless
IP layer. This means that before any TCP
segment can be sent to another host, a TCP
connection must be established to that host.
Connectionless IP has no concept of a
connection, and simply forwards packets
without any understanding if the packets
ever really got where they were going. In
contrast to TCP, UDP is a connectionless
transport layer on top of connectionless IP.
UDP segments are simply forwarded to a
destination under the assumption that sooner
or later a response will come back from the
remote host. The response forms an implied
or formal acknowledgment that the UDP
segment arrived. At the top of the TCP/IP
stack is the application, or application
services, layer. This is where the client–
server concept comes into play. The
applications themselves typically come in
client or server versions, which is not true at
other layers of TCP/IP. While a host
computer might be able to run client
processes and server processes at the same
time, in the simplest case, these processes
are two different applications. Client–server
application implementation can be
extremely simple. A server process can start
and basically sit and listen for clients to talk
to the server. For example, a Web server is
brought up on a host successfully whether
there is a browser client pointed at it or not.
The Web server process issues a passive
open to TCP/IP and essentially remains idle
on the network side until some client
requests content. As a result of these
structured protocol suite, different devices
can be used at each level.
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