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tions normally use wireless technology as mobility is highly sought after- everyone despises the idea of having wires tan-
gling all over the body.
Figure 2.3 transmissions medium between Guided and unguided FONG et al 2011
2.1.2 Metal Conducting Cables vs. Optical Cables
Undoubtedly, mobility is a major concern for the governance of wireless communication in telemedicine applications. However,
it is crucial to understand the principle properties of metal con- ducting cables and fibre optic cables as they remain highly uti-
lized in particular sectors for instance the network backbone or relation between
fixed devices. Now let us examine the way these cables transmit data and compare their properties to study
how they are best suited for certain applications. By examining the ‘twisted pair’ cable as shown in Figure 2.4, we can briefly
study the use of metal conducting cable. The figure illustrates two insulated wires coiled with one another in a helical fashion.
Computer and telephone networks normally use this type of copper wires. Information is conveyed in a simple manner
where a specific voltage means logic ‘1’ and another voltage
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level represent logic ‘0’. The accurate exhibition relies on the speci
fic encoding mechanism utilized but we assume a positive voltage denotes a ‘1’ while the absence of voltage 0 V is rep-
resented as ‘0’. I. Therefore, transmitting information is fairly fundamental in which the cable carries a voltage that alternates
between a positive voltage and a 0 V when relaying a sequence of ‘1’s and ‘0’s. Here, optical communications also operate in
an identical manner. Figure 2.5 shows that if ‘1’ is transmitted, a light beam travels through the centre core. In contrast, ‘0’ is
represented by the lack of light. As such, the light beam which is emitted at the
fibre optic cables end will be in a succession of on and off. Usually, process of switching from on and off is too
rapid to be noticed by a human eye. Thus, it may appear as al- ways being on. Since the cable is bendable there must be some
kind of mechanism for retaining the light within the cable’s core- a cladding that surrounds the centre core as depicted in
Figure 2.5. The cladding is made of a highly re
flective material which prevents light from escaping by reflecting the light back
into the core.
Figure 2.4 Twisted cables FONG et al 2011
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Figure 2.5 Fiber optic communication systems
FONG et al 2011 In the two scenarios, the presence or absence of a feedback de-
termines the transmission of ‘1’s and ‘0’s across a cable. Never- theless it must be noted that in reality what happens behind the
scene may be complicated but the discussion above illustrates the process in which transmission takes place. There are some
types of cables which are frequently utilized in wired telemedi- cine networks. One of the metal conducting cable is called the
‘co-axial cable’ which is no longer frequently used with tele- medicine applications but will be mentioned briefly as it is still
used in many applications especially in decoding boxes and TV antennas. Its main component is the centre core conductor, in
almost the same structure as
fibre optic cable, surrounded by another group of metal conducting strands and separated by an
insulator. A major problem revolving this cable is that it is bulky. Other types of wiring include a couple of wires running
in parallel. There are two major types of fibre optic cables namely glass and plastic
fibres. The main difference is the cost and performance. Generally, glass fibres fair in terms of trans-
mission rate and reliability but the plastic fibres are compara- tively cheaper per unit length.
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2.1.3 Transmission Speed of Data
Bandwidth’ specifies the quantity of data a particular channel transmits and it is crucial to fully understand it in any form of
communications. The bandwidth is fixed for a channeled. A general guideline highlights that a higher bandwidth will sup-
port a higher information rate. As a particular transmission me- dium’s bandwidth is
fixed, data transmission rate can be increased by adding more bits into one ‘band’. A tally of the
number of changes of electronic states per second is referred to as a baud. For an instance, a copper cable of 1k baud changes
the voltage 1000 times in one second. A crucial fact is it does not essentially mean that it just transmits 1000 data bits per se-
cond. This is explainable by examining several mathematics equations, even though we will not probe into the concepts. A
specific number of distinct signal levels L is referred to each baud or shift of signaling state in one second. For instance, the
voltage levels of 0.5 V and 1.0 V. These distinctive levels can be represented by combinations of binary bits. For example
01 and 11 represent 0.5 V and 1.0 V respectively. A direct relationship exists for the the number of bits n for every baud:
n = log
2
L
Or:
L = 2
n
Thus, in this specific example, there are two bits n = 2 and four dissimilar levels L = 4 each one indicated as 00, 01,
10, and 11. Moreover, the data transmission rate or bit rate, counted in number of bits per second or bps might be expanded
for a given
fixed baud rate by utilizing more diverse signaling levels as more bits can be transmitted by every baud. Bandwidth
2.2
2.3
