44
buildings which represent different units that are interlinked to a network backbone as indicated in Figure 2.6.
Figure 2.6 Network connecting the hospital 2.2.7 Satellite Networks
These are more advanced and costly networking as launching a satellite accurately above the earth is an expensive affair. How-
ever, its operating guideline is uncomplicated. A communica- tion satellite or comsat is placed into a pre-determined orbit
above the earth. The orbit of the satellite will depend on the pre- ferred coverage area. The comsat functions as a point-to-point
microwave radio relay which facilitates a radio connection be- tween two distinct Earth stations. Satellites are often utilized in
WAN wide area networks. Although a satellite cannot with- stand natural interference for example solar storms, it is indeed
very reliable and gives appreciable speed interfaces. Despite the fact that such features may seem apt for remote robotic surgery
considering the endless amount of data which need to be trans-
45
ferred; it is not suitable since its integral long propagation delay will probably influence instantaneous operations. Therefore,
satellite networking is mostly utilized for remote recovery.
2.2.8 Frequency Bands between Licensed and Unlicensed
Some networks utilize licensed bands while the other networks are unlicensed and they shared the band with multiple users.
Hence the effect of licensed and unlicensed frequency on tele- medicine operations is to be discussed further. Any telemedi-
cine application can function in both licensed and unlicensed frequency bands and according to Dekleva et al 2007, yan et
al 2010, zhang et al 2011 which is a better option depends on the situation at hand. Firstly, an unlicensed network does not
experience any delay or incur any cost in getting a license. Moreover, an unlicensed connection is easily created and can be
done by anyone with no limitation on the kind of radio gadgets being used. However, since everyone can access the gadget is at
high risk of interference and security breaches. On the other hand, licensed networks will function within designated bands
with restricted usage so the devices can highly personalised to the exact requirements of the users. Licensed frequency bands
have protection against inference although a 100 guaranteed bandwidth availability and 100 assurance against interference
meaning an interference free environment cannot be attained. Therefore, one has to negotiate between convenience and cost
with security and operating environment. In conclusion, there are several kinds of wireless networking which can be used for
an array of telemedicine functions, each with its own benefits and drawbacks. A particular selection on the type of wireless
networking will be based on its performance and features as the type of services obtained can extensive. Normally users will opt
to make use of an existing network to reduce cost and time tak- en to set up. The advancement in communication technologies
enables more selection to be made available in future and tele-
46
medicine application will be more accessible and reliable to be utilized by people with different needs.
2.3 Operating Outdoor
The impact of electrical noise emitted by the gadgets nearby may be very prominent as the signal strength will weaken in
relation to distance travelled attenuation, Transmitted signals can be lost or corrupted if the noise is very severe resulting in
the data to be useless. At the same time, beside the noise and attenuation, distortion of the signal can be a problem as data
travels through metal conductors. Distortion happens in many ways and is subjected to the kind of obstacles that lie along the
signal path. Normally, the shape of the signal is distorted for instance when a square wave can no longer maintain its smooth
pulse. Even though, the problem of signal propagation does happen indoors, there are more factors which are beyond con-
trol in the outdoor environment which makes more signals de- grade severely.
The yardstick that measures the signal loss in a transmission link is the loss which is predicted to happen in a free space
meaning the loss which happens along a path which is free of everything that might reflect or absorb signal energy. If a radio
wave which is being transmitted hit a physical obstacle it will be subjected to the phenomena as in Figure 2.7: -
i. Diffraction: a signal will split into secondary waves.
Diffraction will happen if a propagating signals strikes a surface which sharp edges. The waves emitted by the
surface will be present in space and some fraction of the waves may penetrate behind the obstacle and create a
power loss. A phenomenon of waves bending around the obstacle will occur.
