Assessment of Link Budget

166 often involves setting up new hardware to the existing network and extending coverage area. During the expansion, the network should not be interrupted as the availability of network is very important especially if that network supports life saving opera- tions. In the case of telemedicine, availability is far more im- portant compared to the other purpose as accidents could be happen and it will not wait until the network service resume. Therefore, a network should not be shut down temporarily. In terms of wired network, expansion usually involves adding of new cables. On the other hand, in terms of wireless network, it requires some adjustment of the infrastructure. Therefore, modi- fications are more feasible for wireless compared to wired net- work. According to Fong 2004, the transmission path is hard to be altered. However, the transmitter can be enhanced to en- sure receivers to process the incoming stream of data if there is an increase in data input. The main aim will be to maximise the use of available resources in the system and minimize errors so that it is not necessary for re transmission.

5.2.1 Modulation

The conversion of digital signal to analog signal is termed mod- ulation. For example, a modem has the capability to transmit computer digital signal into analog signal so that the signal could be transferred through the traditional phone line. 167 Figure 5.4 Constellation diagram FONG et al 2011 Based on the constellation diagram above, the cross section rep- resents the amplitudes and phases of signal. More dots in dia- gram means that there is a higher modulation of above 64 and carries more data bits. Nearer dots mean that it is harder to iden- tify individual dot. As resolving packed dots requires more complex recipients, there is a need to trade-off between the ef- fectiveness if spectral usage and the framework of receiver. For example, with something as high as 1024; the amplitudes and phases difference between neighboring signals points may make them cannot be differentiated.