Movement of Data, Information, and Knowledge: The Transmission Subsystem
It (telecommunications) is powerful and it empowers, with far reaching consequences.
It has demonstrated the potential to transform society and business,
and the revolution has just begun. With the invention of the telephone, human
communications and commerce were forever changed, Time and distance
began to melt away as a barrier to doing business, keeping in touch with loved
ones, and being able to immediately respond to major world events. Through
the uses of computers and telecommunication networks, humans have been
able to extend their powers of thinking, influence and productivity, just as
those in the Industrial Age were able to extend the power of their muscles, or
physical self, through the use of heavy machinery. ( Goleniewslti 2002, xv)
LEARNING OBJECTIVES
Compare and contrast transmission and communications.
Categorize the various ways of sending ( transmitting) signals from one
place to another.
Recognize the features of effective transmission.
Identify and describe the role of the components of network architecture.
OVERVIEW
Movement (transmission) of a signal from one to another, in time and place,
is a subsystem of an augmented data, information, and knowledge (ADIK)
system. If we could move our bodies through space at the speed of light, we
could do things that are shown to us in movies. Of course, we can't. Yet,
wheels help us move faster. Wings enable us to fly. Before the telephone, we
were limited to pebbles, smoke, flags, horseback, and written messages as a
means to transmit our intentions and action to others. Now we can talk
across oceans and through space, bringing together cell phones, TVs, radio,
and other electronic devices to help us deal with many things before, while,
and after they happen. The information scientist works with the electrical
engineer, the computer scientist, and the psychologist to determine what
kind of AD!K system meets human needs and requirements. This chapter
will examine the transmission of data, information, and knowledge as a subsystem
of an ADIK system. It will discuss the importance of transmission in
the day-to-day experiences of both individuals and organizations. This
chapter will also introduce networking and the technologies that make it
possible. Throughout the study of transmission its relationship to communications,
what is transmitted for human meaning and understanding, is of
central importance.
Terms
Transmission
"Transmission" is defined as the movement of signals from one point in space
and time to another. Teletransmission refers to the electrical movement of signals.
Signals represent states of events captured by sensors coded and moved
(transmitted) to human/machine processors (satellites, telephone system, computers,
e-mail).
It should be clear at the outset that the transmission of data may obey different
principles than the transmission o f information, and the transmission
of information may differ from the principles involved in the transmission of
knowledge, although the three are interrelated in important ways. Communication,
as applied to transmission, refers to the electronic and other devices
that move signals from one place (medium) to another. Exchange between
senders and receivers can be at different points of time and place. This aspect
of transmission of these resources is discussed. as part of a communication or
transfer subsystem (chapters 9 and 10 of this book).
Wireless transmission, simply stated, is without wires; the cell phone is
the most common example. Wireless transmission has been a human activity
for a long time, from the time when smoke signals were the means for asserting
battle intentions to the present-day radio at home or in the car. Currently and collective activity and commerce occur. Study of wireless transmission
it is most predominant in the cell phone, where much of individual is a subject of some technical complexity. Only a brief view can be provided
at this point in our study of information science. The key issues rest on the
effective use of bandwidth, the capacity that a connection has for carrying
data. The technical problems rest on the retention of signal strength, the influence
of signal echo, fading interference, and noise. The design and position
orientation of antennae enter into the assessment as well. Problems
center around standards for use and design, political regulation, and spectrum
allocation.
More often than not, communication and transmission of messages and
signals are considered as synonymous experiences. Communication, in this
text, refers to the human ideas, meanings, understanding, and intentions
(transmitted by a carrier between a human sender and receiver: e.g., language,
mail, etc.). In the literature the terms "teletransmission" and "telecommunications"
are cojoined both in theory and practice (Thompson et al. 2006).
Telecommunication refers to the process of electronic communication ( e.g.,
radio, TV, media, etc.). Communication is not possible without transmission.
The absence of transmission, however, can also be a source of communication
(i.e., the fact that you did not receive the Jetter from the college you applied to
can be a signal suggesting the possibility of an event or a number of events regarding
your admission). See figure 6.1 for some of the differences between
transmission and communication.
Why is the difference between transmission and communication important?
An increasing number of countries and regions have become reachable>
and in turn, the world is a more accessible place. It has become a necessity for
doctors in large cities to reach doctors located in remote parts of the country.
Surgeons in California have concluded successful operations on patients living
in Alaska. It is important for businesspeople to be able to get together and
move their ideas from one place to another.
As ADIK systems, we write and place letters in the mailbox, dial a phone
number in our home, chat with our friends. In all of these experiences, we
are engaged in the process of transmission that facilitates communication.
When our sensors ( organic/mechanical) pick up energy from the external
world, this energy is expressed in the form of a signal (chemical, electrical),
which moves either to our brains, our hands, or to the computer. When we
pick up a newspaper, book, or letter, these documents (products) serve as
transmitters of states that are occurring or not occurring, represented in
physical form. The important point for our understanding of information
science rests on the fact that without transmission, ADIK systems would not
exist, let alone operate. When transmission fails, ADIK systems fail. When
they do, the information scientist attempts to understand the cause of such
failures and integrates this understanding in the analysis, design, and evaluation
of ADIK systems.
The Transmission Process
Signals from events captured by ADIK systems are coded, and when so represented,
they constitute data. These data in turn provide the means to generate
messages over distance and time from one source to another. Transmitters and
receivers are two hardware devices with a physical connection between them.
For simplicity's sake, let's say that one of the devices is a computer and the
other is a printer directly wired to a network. Inside the computer, there are
two essential parts needed to establish data transmission: software and a network
interface card. The software includes a director and a network driver.
The role of the director is to tell the information where to go. In other words,
the director determines whether the request made by the user can be handled
by the computer itself (a local service) or if the request has a need for a network
service (remote service). For example, you finished an English paper
that is due tomorrow and want to print it. The printer is not directly connected
to the computer, yet it is connected through the network, and the
printer sits across the room. Remember, the characters that were typed into
the computer through the keyboard have been translated into binary code
(ones and zeroes) and transmitted. Since the printer is a network service, the
director guides this binary information to the network driver with notification of
destination. At this point, the network driver engages and acts as a conveyer
between the director and the network interface card. It takes the information
to be delivered and packs it up according to the rules established by
the network, called network protocol (more on this later in the chapter). In
our example, the binary word-processing document has descriptive information
attached to the beginning of it, which includes where the message originated
and its destination.
The Role of Words and Symbols as Transmitters
Language is a system of words and symbols used to transmit our intentions,
feelings, and other states of our lives. Language plays an essential role in communications.
For example, you received a letter from a friend whom you met
on a recent visit to China. The letter was written in Chinese. Although you received
the message, you would not be able to read and understand the message
because it was in a different language. You were not able to translate the
symbols, thus no message was received. It provided no meaning to you. Information
scientists working with computer scientists, linguists, and others are
now making advances in computer language transmission and translation
that would bridge this language gap. But in addition to lack of transmission,
we need to consider that there are errors in transmission that need to be accounted
for.
Electronic Component Failures
Whenever any electronic or mechanical device is used for whatever purpose,
the possibility of equipment malfunction or failure in transmission can occur.
There are also other errors that can occur. Whenever we send a message from
one source to another, human or technological, there can be an error in understanding
(knowledge) of that which is intended. The error can occur as
part of noise (random energy) that impairs the reception of the message. Humans
have the capacity to return the message to the sender for clarification,
thus reducing the impact of the error in the application of what is intended.
Yet noise (random energy), the result of technical interference, can directly influence
the transmission of the message in many ways.
Errors in the transmission subsystem can occur at many parts of an ADIK
system. For example, failure to replace the batteries in the fire detection device
in your home renders that sensor unable to transmit to-and thus informthe
inhabitants about the fire, leading to serious consequences. The delay in
transmitting the message from the human lookout to the ship's captain on the
ocean liner Titanic cost the lives of many passengers.
Transmission of Knowledge
One view (among many) that could distinguish between information and
knowledge centers on the question that individuals ask about themselves and
the world around them. Knowledge centers on the questions of "how" and
"why:' Answers leading to an understanding of these questions may rest with
philosophers, psychologists, educators, and many other professionals. Meanwhile,
the transmission of knowledge is well within the bounds of many institutions,
from the press to education. The work and focus of information
scientists will center on how technology, primarily computers, can aid human
access and application of knowledge. It should be mentioned that in the post-
9/11 era, the access and management of knowledge (intelligence) would offer
increased challenges to the information scientist.
The Network
The Broad View of Networks
The sharing of data, information, and knowledge across distances is a necessary
tool in everyday life in today's society. The demand has fueled research
and development of better ways to connect nodes of computers through networking.
In the construction of a network, several specifications must be considered
before putting it all together. What types of data will be shared? How
many bytes is a typical quantity of data? How fast does it need to be shared?
Who will be the users of the database? What are the limits to their capabilities?
How many users will want to share this information? How much reliability is
needed in the network? All these questions-and more-should be considered
when analyzing, designing, and evaluating ADIK systems (in this case,
networks). The answer to these questions will help determine what network
devices are needed, what medium should be used, what network architecture
software should run the system, and if any other hardware devices are needed
to advance the sharing of data, information, and knowledge among users.
There are advantages, disadvantages, data size, and rate limits to be considered.
Most of all, the cost of building such networks usually determines the
materials involved. All these matters are of direct interest to the information
scientist in the analysis, design, and evaluation of these systems.
What Is Meant by Network and Networking?
A network is a series of computers that work together to serve users at the
same or different locations. Networking is data, information, and knowledge
transfer (from one point in space to another) made possible by teletransmission
technologies. These technologies function in a medium-the physical
surroundings (air, water, etc.) in which the signals are carried. Networks augment
the human capacity to communicate. It's the same as having a conversation.
It takes at least two communicators (transmitter and receiver device),
a medium between them, and some service to be provided. For example, in a
face-to-face conversation, two parties communicate. Air is used as a medium
(voice) to carry sound (acoustic signals) between the two, and the service that
is provided is the language that is used by each person involved, each having
an understanding of the rules of its use. By definition in a technological sense,
networking is the connection between two or more computers ( or other devices)
through some type of medium, with the ability to transmit according to
set rules and protocols that form a local area network (LAN), metropolitan
area network (MAN) , or even a wide area network (WAN). So now let's examine
the three basic parts of any network: the transmitters and receivers, the
media, and the services.
Transmitters and Receivers
There are other hardware devices used in constructing a network that become
useful depending on the needs of the network configuration. These hardware
devices are hubs, switches, bridges, and routers. Each sends data along a network,
but varies in capabilities. For example, the hub (figure 6.2), which is located
at the center of the network, takes the data from one node of a star
topology and broadcasts the data to all other nodes (computers) on its network.
It does not concern itself with the address of the receiver when forwarding
the data. It only repeats data to all the nodes connected to this single
network.
When two or more networks connect together, a slightly more complex
device must be used. For example, a bridge is used to connect two networks
that use the same protocols or rules in sending data (protocol is discussed
later). The software capability must contain addressing and switching intelligence.
This means that the bridge is aware of the location of all the nodes
connected and the unique identifying addresses. However, if I wanted to
connect two or more networks or different protocols, a router must be used.
Since this hardware device connects two or more networks of different protocols
or rules, the data might have to be adjusted to be sent across another
network. Let us consider that data are prepared by sending from a node in
network 1, where the protocol requires the same size of ten megabytes (Mb).
The data are being sent to a receiving node in network 2 that requires a data
size of only 1Mb. It is the router's job to make adjustments between the two
networks. Therefore, the original signal of I 0Mb data packets have to be
broken down into !Mb data packets before they are sent across network 2 to
the receiving node. These concepts will be discussed in greater detail later in
the chapter.
The Server
Most computers that are part of a network are connected through cabling to
a bigger, faster computer with more storage capacity, known as the server. The
server is just that-it serves the other computers connected to the network.
There are several services provided by this technology such as printing, file
storage, messenger services, and others. A request is made from one computer
to print the word-processing file to the print server computer. That server
controls the print queue, the order of the files to be printed. It is there that the
file is formatted and printed back ipto the characters that were visible on the
user's monitor. There are other services such as messenger services that send
and receive electronic messages (like e-mail or bulletin boards) or file services
where the served files are stored and retrieved from the file server instead of
one's own computer.
The Medium
The medium is the surrounding material in which signals exist and move
around (air, water, etc.). In the present sense, the medium refers to the device
that enables signals to be transported from one point to another. We can understand
the kind of medium technology and the function that such technology
serves. There are several types of mediums. They are twisted pair wiring,
coaxial cable, and fiber-optic cabling and wireless.
Twisted Pair Wiring
Otherwise known as "phone wire," unshielded twisted pair (UTP) cabling
is a pair of copper wires twisted around each other to prevent interference of
signals. The fundamental physics concept of electricity and magnetism behind
this technology is that when electricity runs through a wire, a magnetic
field is created and surrounds the wire. Wires that are close together will have
their magnetic field interfere with one another, thereby corrupting the electrical
signal in the wire. By twisting the wires together, the fields are cancelled
out, and the wire is then insulated, or the signal is protected from corruption.
There are several types of unshielded twisted pair cabling.
Coaxial Cable
Coaxial cable, or "coax;' is the wiring used for cable television. It consists of
a solid copper wire surrounded by insulation and a shield made of copper
braiding. It is then further coated with a protective covering to prevent further
external interference. There are two types of coax: thicknet and thinnet. Just
as the name implies, thicknet is the thicker of the two, able to cover longer distances
when networking: 500 meters as opposed to 185 meters by thinnet. A
British naval connector (BNC) is used to connect cable to its hardware.
Fiber-Optic Cabling
Fiber is the premium choice of cabling. It uses light signals traveling along
glass or plastic, instead of electrical signals along copper wire. The glass is then
surrounded by more glass to act as an insulating layer to prevent leakage or allowing
the trapping of light inside. It is then coated with permanent virtual circuit
(PVC) or Teflon as a protective covering. The advantages and disadvantages
in the use of fiber optics in communications are listed in table 6.1.
Table 6.2 compares how long it would take to transmit a book, using several
different methods including telephone (twisted pair), LAN (coaxial
cable), and fiber-optic cable.
Advantages and Disadvantages of Fiber Optic Usage.
Advantages That Fiber Offers:
1. More bandwidth;
2. Allows one to add additional equipment that provides for increased transmission
capacity;
3. Not subject to interference (electromagnetic);
4. low in weight and mass.
Disadvantages:
1. Special test equipment is needed;
2. Shortage of components and manufacturing sites;
3. Subject to physical damage;
4. High installation costs;
5. Vulnerability to damage by wildlife.
Topology
Now that we are aware of all the hardware possibilities and wiring types, we
must put all these together so that data, information, and knowledge can be
shared. How these devices are connected is called the physical view of local
area network (LAN). By definition, the physical view is the physical location
of all the hardware and the physical connection between them. The topology
used, also known as the "wiring orientations," is a very important consideration
when designing a network. Which topology to use depends upon which
network architecture is implemented. These are critical aspects for an ADIK
systems analyst and designer.
How Fast?
• One page of single-spaced, word-processed text is equal to about 2,000 bytes of information,
or 1 6,000 bits (8 bits per byte). The text of Cohen's book is approximately
200,000 bytes long.
• Old-fashioned (1 970s) teletype was transmitted at 1 1 0 bits per second (bps). At that
rate, it would take four hours to transmit this book via teletype.
• If we transmitted this book over a typical telephone (dial-up, twisted pair cable) computer
link (2400 bps), it would take approximately eleven minutes.
• If we transmitted this book over a typical LAN (2.6 million bits per second [Mbps] on
coaxial cable), i t would take less than one-half of a second.
• If we transmitted this book over a special fiber-optic cable-based network ( 1 00 Mbps),
it would take less than one-fiftieth of one second. Looking at it another way, we could
send fifty copies of this book in a single second.
Four LAN network topologies are presented: star, bus, ring, and tree. These
are displayed in figure 6.3.
The star topology is probably the most popular. All hardware devices of
this segment of the network ( otherwise known as "nodes") are connected to
a hub or some other multiaccess hardware unit. Any data sent by the computer
must pass through the central device before continuing on to another
node of the network. If a node were to have problems, it would not interfere
with the operation of the rest of the network. Also, the failed node could be
easily detected. On the other hand, the physical wiring of this orientation
could get ugly and expensive! The bus topology is a "linear" orientation that
has two distinct endpoints or terminators; each node branches off a common
line having its own address. The advantage of the bus topology is the minimal
wiring needed; it is more cost-effective. The main disadvantage of the
bus topology is that if a node were to fail on this topology, the rest of the network
beyond this point would be unable to transmit across the network. The
nodes of a ring topology are connected in a circle. While it is similar to a bus
topology, it has no terminators. All the data sent by a node travels around a
ring until it reaches the address of its destination. The physical connection
can get expensive, and if one node fails, the whole network goes down until
the problem is fixed. In the tree topology, the root is the head end where all
the transmissions must pass. The root of the tree contains the trunk cable
where user devices are connected. The head end translates the frequencies of
one device to the frequency of another (remodulation). Many network administrators
have designed LANs using combinations of all these topologies.
Transmission Processing Protocols
As stated previously, the method used in the transmission of data is of direct
interest to the information scientist in the analysis, design, and evaluation of
these ADIK systems (networks). Sending data across the wiring of a network
is very similar to sending a letter via U.S. mail using a standard addressing
method. This standard addressing method, called Internet protocol {IP) addressing,
is a system that applies a unique identifier to a node or a host connection
to a network. IP addressing assigns a logical address to every device
and gives an address for internetworking.
By definition, a protocol is a set of rules that describe a method of transmission
between systems. There are several protocols working today, but for
our purposes, we will focus on the most widely used, which is transmission
control protocol I Internet protocol (TCP/IP). They all have similar functions
but differ in the handling of translation, encryption ( code to restore original
data), security, and comprehension techniques. Each basically achieves the
same goal, namely, sending data to its destination across a network. So how
does it work? Let's look at the open systems interconnection (OSI) model to
understand protocols (see figure 6.4).
But what guarantees are there to ensure delivery of the data? In 1984, the
International Organization for Standardization (!OS) presented the OSI
model for sending data over a network (figure 6.4). The goal of this model was
to help eliminate network incompatibility and transmission problems between
different types of networks. It was not designed to be an absolute standard,
but it is used in developing network protocols or rules for sending data
over a network. It is a great reference model to use in understanding how networks
function and computers communicate.
A protocol takes data to be delivered and breaks it down into understandable
parts, in terms of machine language. The OSI model can be compared to an
onion; it has several layers. So, like an onion, the data sent can be "peeled" apart
and translated by another machine somewhere else along the network. The OSI
has seven "layers," if you will. Working from the top down, figure 6.4 shows these
layers. Starting with the application layer and continuing down to the physical
layer, the data is broken into chunks, also called packets, with control data being
added at each layer on the way down (transmitting device) and then stripped
away on the way back up (receiving device). This process is referred to as encapsulation.
For example, you have an English paper due tomorrow and you have
been typing into the computer. Along with the typed document, the application software adds at the "head" of the document called "header information:' Header
data could include such specifics as the version and software package data used
to create the document, how large the document is in terms of byte size, where
the document begins and ends, and other data pertinent to the receiver.
Altogether, the software header and the document itself make up the application
layer. This is the innermost layer of the set of data to be sent. Other examples
of application layer data could be created in e-mail, Hypertext Transfer
Protocol (HTTP) requests, or file transfer protocol (ftp).
The presentation layer refers to data that is translated, formatted, restructured,
encrypted, and compressed. It is then encapsulated by identifiers
of the types of software used to manipulate it in such a way. The presentation
represents the combination of the adjustments made with the added
software data. Now that the data is packaged and its destination determined,it is now prepared for deliver y. All protocols have a limit to the number of
bytes of data that can be sent across a line at one time. The transport layer
takes care of this issue by dividing data into packets. Then, it ensures that
the packets will get to the destination. If for any reason not all the data
reaches the destination address, it is the transport layer that is responsible
for retransmission of the packets. Before the data packets are transmitted,
three layers of network protocol must process them. First, the network
layer determines the best path to send the data across the network and adds
this data to each packet. The data link layer adds error-checking information
to the back of each packet. The receiver of the data packets then uses
this data to determine if the data packet has been corrupted somewhere
along its transmission path. Also, the media access control (MAC) address
is added. This is the unique identifier given the network interface card
(NIC) when it is manufactured. This number is a way to distinguish between
computers on the same network and, thus, packets can be traced
back to the source.
Lastly, the entire data packet is converted into binary digits. The physical
layer then takes the ones and zeroes and converts them into voltage, light,
or radio signal, depending on the network medium used. Isn't it amazing
that all this occurs in a matter of fractions of a second? So much detail is
monitored when designing the protocol software needed to handle the
packaging of data that is sent across a network. Remember, the OSI model
is only a reference for programmers that design protocol software. Not all
protocols have these seven distinct layers but have taken care of the functions
in the combination of layers. For example, the TCP/IP protocol application
layer combines the duties of OSI's application, presentation, and
session layers all at once. Regardless of the protocol used, the names of the
layers may be different, but the concepts are virtually the same. All of this
is of critical importance to the information scientist. The main concern is
to ensure that the data as a total packet reaches its destination, has not been
corrupted all along the way, and that the interpretation of the data is not
corrupted.
Network Architecture: Combining It All Together
The medium, the physical layout of the transmitters, the access method, and
the protocol (services) all combine to make what is known as the network architecture.
Table 6.3 provides a chronology of network architectures.
Some current common network architectures are Ethernet, AppleTalk,
ARCNet, Token Ring, and FDDI (fiber distributed data interface). The Ethernet is the most common network architecture. The access method is known as
carrier sense multiple access /collision detection (CSMNCD). This refers to a
computer that is ready to send data across a medium that will "listen" to the
wire to detect if it is carrying a signal, that is, another device sending data. If
no signal is detected, the computer will send its data; otherwise, it will wait for
a random time period before trying again.
Advances in Teletransmission
For the information scientist, teletransmission and telecommunications
offer significant challenges. These challenges are defined in the vast, fast, and
significant advances in technology represented to some extent by networking
and wireless transmission of signals. These advances that aid in the processing
of data, information, and knowledge provide significant opportunities
for the planning, operating, and controlling (managing) of many
individual organizational resources. The fu nctions of teletransmission and
telecommunication can be seen in the many advances in technology, which
support and advance national and international commerce as well as geopolitical
initiatives. Networking and wireless communications are examples of
two such advances. Of particular interest and importance in the role of remote
sensing is serving in extending the science of data, information, and
knowledge transmission. "Remote sensing is the science of deriving information
about the earth's land and water areas from images acquired at a distance"
(http://fwie.fw.vt.edu/tws-gis/glossary.htm). See figure 6.5 for an application
of remote sensing.
SUMMARY
Our lives depend on our capacity to receive, note, and respond to the activities
and ideas around us. The movement (transmission) of signals that
transmit our ideas and intention is a normal human activity, yet also a complex
affair_ Transmission (movement) of signals from one component of an
ADIK system to another is an essential function and requirement of such
systems. Failure of transmission corresponds to the failure of the system.
The content of the transmission is represented as the signal. The signal contains
the data that is transported through the medium. The expression of
data in a transmission is considered the language of the transmission. The
matter of the language used to convey the message can vary based on cultural
applications that require translation. This difficulty in transmission is
increased when the equipment used or the human action involved in the
transmission fails, or, when there is lack of precision in the use of the language m conveying the intended idea adequately. These considerations
apply to the transmission of information and knowledge alike although the
impacts and consequences may differ. Advances in transmission and communication
media ( twisted pair, coaxial cable, fiber optics) that continue to
be made are important to our understanding of their role in information
science, particularly in the analysis, design, and evaluation of ADIK systems.
Networking of these technological advances, with the combined use of computers,
serves to increase the human ability to use transmission and communication
hardware and software more efficiently and effectively in the
engagement of problems and making decisions. Wireless transmission is a
case in point. As we can note, wireless (cellular) transmissions have influenced
and continue to influence the way that individuals and organizations
relate to each other and form a broad perspective of national and international
commerce and geopolitics.