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multiple accesses can be easily understood by referring to Fig- ure 5.6 and 5.7. A network is divided into individual time slots
in Figure 5.6. In this scenario, the time slot happens to be equal but this situation does not occur most of the time. Every trans-
mitting device has its own allocated duration and the next user will be allocated another duration. For instance, A, B and C are
the devices allocated with 10ms time slot each. During the transmission process, device A will be given the first access and
spend its first 10ms. After that, B is given the same time slot and followed by C. This means that at the time slot between
0ms to 10ms, A will have the transmission followed by B in between 10ms to 20ms and C in between 20ms to 30ms. As C
completed its time slot of 10ms, it goes back to A and the entire cycle continues. In every 10ms the device is changing its se-
quence A to B to C and again with A. The theory of the multi- ple accesses is well explained in the example of three devices
above. However in real time, when switching between the de- vices, there is a lag time between them. There were no instanta-
neous transmission goes on when each device completes its time slot. Hence the lag time should be considered when switch-
ing the transmission cycle. Figure 5.8 describes the transmis- sion process discussed earlier where a logical switch enable the
devices to gain entry to the channel.
Figure 5.7 Multiplexing of frequency division
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Figure 5.8 Time slots alternation FONG et al 2011
Rather than dividing network into time slots, the network is di- vided into unique frequency bands through FDMA. The channel
is split according to frequency bands permitted illustrated in Figure 5.9. For instance, the split frequency is demonstrated by
having a channel with a band of 100 to 400 MHz. The channel is split into three equal frequencies where each of them is capa-
ble of transmitting 100MHz. This means that all the three splits have the range of 100 to 200MHz, 200 to 300MHz and 300 to
400MHz transmission. Each split shares the one third of the channel bandwidth. However in real time, the one third of the
bandwidth is hardly fulfilled by the splits. This is due to band pass filters Figure 5.8 shows that each splits were attached to a
band pass filter against the usual switch with TDMA which are not able to immediately break the frequency for the next and
also for immediate start up. The use of a guard band is required for the cut off so that it creates better accuracy of the filters.
Figure 5.10 show a perfect filter with an accurate cut off of the frequency. In real time, such perfect filter cannot be found. As
the disruption is progressive in nature, more effective filter with the accurate frequency cut off is needed so that the changes
happen in quick time.
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Figure 5.9 Filtering for different sub-bands
FONG et al 2011
Figure 5.10 ‘Ideal’ filter with sharp cut off
FONG et al 2011 Those accessible methods on splitting channels have a signifi-
cant effect on a shared wireless networks. TDMA and FDMA methods are more commonly used for splitting instead of other
methods such Code Division Multiple Access CDMA. The main differences of TDMA and FDMA are well-fed bandwidths
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over a time frame and the continuous availability for bandwidth variation. Each method provides a distinct advantage where
TDMA is more suitable for subsequent data traffic and FDMA for the severe data traffic as it have a continual access and is
constant over a period of time. Allocating dynamic bandwidth increases the efficiency of the channel by providing more de-
mand sources.
5.2.4 Orthogonal Polarization
Expandable data throughput is achievable by adjusting the con- figuration of antennas. For example, the signals of vertical and
horizontal polarization can have separate channels through put- ting different antennas with orthogonal polarization perpendicu-
lar between the two signals. Based on earth’s topography, vertical polarize antenna has a perpendicular electric field
whereas horizontal polarize antennas has parallel electric field. Figure 5.11 shows an example of old style TV antennas placed
on rooftops known as linearly polarized antennas. Those anten- nas on rooftops are always placed in parallel to earths topogra-
phy, thus is known as horizontal polarization. Polarization can be increased by having more channels through the addition of
antennas. Figure 5.12 show the existing antennas of circular po- larization. In circular polarization, the polarization completes its
rotation per wavelength as the plane rotate in a circular motion. For example, if the wavelength of polarization is 1 meter the
circular polarization should have 360 degree rotation in a 1 me- ter. The energy in circular polarization it exerts on horizontal
and vertical planes. The direction of the polarization is also flexible, where circulation can take place in either clockwise or
anti-clockwise rotation.
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Figure 5.11 Regular television antennas FONG et al 2011
Commonly circular polarization has higher adaptability in non- LOS scenario mainly because as it hits any barriers, the signal
are reflected back to the transmission source and the difference sources of signal can be propagated.
Figure 5.12 Circular polarization antennas
FONG et al 2011 To achieve scalability, sectorisation is performed whereby addi-
tional antennas are installed by request by increasing the num- ber of sectors as illustrated in Figure 5.13 which shows that in
the beginning, deployment is installed via the provision of om- ni-directional coverage. Additional three more antennas are in-
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stalled to cover areas in a 90° angle as demand gets higher. Therefore, 3 more networks are provided in the same region.
Development is possible through segmentation shown in the given example whereby there is an alternative of increasing to 8
segments from 4.
Figure 5.13 Sectorisation of an antenna FONG et al 2011 5.3 Integrating network with current IT services
Most of the e-health channels are established on existing IT ser- vices Gibson, 2002, borgmeyer et al 2005, polak et al 2009
such as in the home monitoring of an asthmatic patient using the Internet. The only difference is the addition of asthma moni-
toring device telemedicine as shown in Figure 5.14. It shows that there will not be a severe disruption to the monitoring sys-
tem even if the Internet is disrupted. However, an integrated channel is a much complicated system and a slight disruption
such as the integration process will result in the disruption of the entire network. As a rule of the thumb, any maintenance
work carried out in one part of an organization should not affect the daily operations of independent of the channel system.
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Figure 5.14 Self-monitoring system for an asthma patient
FONG et al 2011 In order to carry out the network maintenance successfully
without effecting the entire system in an organization it is im- portant to have a copy of the building layout map which illus-
trates the physical network of the building whereby wiring locations, access entries and related infrastructures. It allows the
merging of all the latest gadgets in appropriate locations. Data networking and energy supply should be attached to newly-
integrated gadgets since most monitoring devices could attain energy from cables. Effective integration includes configuring
new portions into the system. All the existing networks might have different network architectures that need varied integrating
demands. Existing communicative channels include IEEE 802.11 WLANs are IP channels that simplifies interaction
through standardizations. However, several previous channels may require extra procedures due to network protocol.
