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3.3.1 At Sea
Maritime rescue is very demanding because cellular communi- cation networks do not function at sea. Satellite signal is the on-
ly communication option that can be used at the oceans. Even though most modern ship has high technologically advanced
GPS, communication might fail at times as unexpected thing can happen. The ship can sink or lost power, the individual who
need to be rescued may be thrown overboard and GPS commu- nication will fail. The development in technologies enables the
rescue and recovery task to be done hassle free compared to be- fore. Locating an individual in the big ocean is the crucial for
the rescue operation but by the use of video extraction technol- ogy with high resolution makes the task easier to handle. Strate-
gic coordination between the rescue boats, control centre and rescue helicopter are important and receive necessary support in
real time as the waves may shift a person who need to be saved to new location. Satellite communication becomes the only op-
tion as need to cover the vast area of the ocean. Satellite signals use millimeter wave in GHz magnitude which are incapable for
detecting sunken objects and ship. This was due to the absorp- tion of satellite frequencies in the ocean water. Underwater
communication is much more challenging than air communica- tion. Underwater communication is accomplished by acoustic
waves which travel 5 times faster in water than air. The study of acoustic waves was conducted back in 15
th
century; acoustic wave frequency has a range lower and average between 10 KHz
to 20 KHz. This lead to the reasons why the acoustic waves are slower in the air and data transmission will be slower. Other
factors that cause the underwater communication to be prob- lematic are narrow bandwidth and high variation of multipath.
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3.3.2 Mountains and Forests
Search and rescue mission is usually visually challenging in a forest area. Even with the aid of infrared camera, there are pos-
sibilities of failure of locating a person. The limitation of infra- red camera can be influence by many factors. Another
communication method that can be used is cell phone commu- nication. However, areas at high terrain and covered by thick
forest has less chances of having cell phone networks. Radio communication is not viable in these areas because of the eco-
nomic factors as these areas are less inhabited by people. Hence these areas have less subscribers and utilization. Typical line-of-
sight LOS link will not work due to the thick vegetation. Therefore, diffraction and reflection of a common radio signals
are the degradation factors that lead to a better communication. Radio communication must be able to transmit signal to the re-
ceiver so that meaningful data or information can be transmitted for example the location of the receiver or images of the encir-
cling areas. The clearing Fresnel Zone concept as shown in sec- tion 2.4 describes the effect of physical barrier such as trees
while the signal is being transfer. This concept relates to the space encircled by an ellipsoid of two antennas between the
ends of a radio link. Here, radio communication can always be established provided there was no disruption to the transmission
of the signals as explained in Fresnel Zone, unless there is ma- jor diffraction or other factor. However, it cannot be concluded
that failing to maintain Fresnel zone always result in communi- cation error. Sometimes, communication relies more on the sur-
rounding environment where it operates. Reflection of signal cause by objects that obstructs such trees, plants and lakes can
be the main factor for any signal loss. Even though LOS path between the transmitter and receive is less likely to exist, there
might be some gaps between the receiver and transmitter which enables one ground reflected path and one direct path through
LOS to co-exist. Therefore, the loss of signal is much dependent
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