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¾ source radiating noise, ¾ receiver grabbing noise, and
¾ Coupling channel between source and receiver. All wireless transmitting gadgets such as cellular phones and
laptop computers are susceptible to EMI from proximate radiat- ing sources. Such interference initiates capacitive coupling
where energy is stored up inside the circuit and hence, affecting the electronic circuitry. This generates a wavering electric
field that may be capacitive coupled to adjacent gadgets. There are
two major forms of EMI; continuous and transient interference, which may be a result of thunderstorms provoking Lightning
Electromagnetic Pulse LEMP or swapping of high current cir- cuits. The continuous interference is initiated by emission of
radiation in a consistent manner from nearby sources, for exam- ple, other medical devices or transmitting gadgets. Transient
interference is intermittent, where sources radiates for a short time. These might be set off by thunderstorms initiating Light-
ning Electromagnetic Pulse LEMP or turning on high current circuits. The International Electro Technical Commission IEC
manages standard regulations regarding EMI while the Comite International Special des Perturbations Radio Electriques
CISPR or the International Special Committee on Radio Inter- ference, manages concerns related to radio. The CE mark,
which is often found on electronic items that include healthcare and medical equipment, denotes Conformite Europeenne or
European Conformity. Items bearing the CE stamp proves the item conforms to the European Directives that oblige Elec-
tromagnetic Compatibility EMC tests to be carried out to as- sure that a particular item fulfill the European Union EU
directive 2004108ce prior to its legitimate release into the market in any component countries of the EU.
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2.1.5 Modulation
Modulation is a process in which a carrier signal which gives the energy needed for the data to be transferred to the receiver is
modified somehow with conformity to the information to be transferred. This is basically a method of cramming information
into a signal for dissemination. Certain parameters of the car- rier signal is changed to reproduce the information to be trans-
mitted for instance, in FM frequency modulation radio broadcasting the frequency of the carrier signal is altered ac-
cording to the voice information. The receiver radio interprets this alteration of frequency as the voice carried over. In its orig-
inal form, criterions that could be altered are inclusive of the frequency number of oscillations per second, amplitude the
signal level or the phase the signals relative position to time. More than one parameter can be changed at a time in complex
modulation procedure so that more data can be represented in every baud. Hence, this method will increase the efficiency of
the transmission. Generally, a more complex receivers electron- ic circuit structure is required for higher spectral utilization effi-
ciency SUE, as the difficulty differentiating between different possible categories of the signal increases. SUE measures the
efficiency of a modulation scheme in transmitting a certain load of data for a
fixed bandwidth.
2.2 Types of Wireless Networks
The development in the wireless communications has paved the way for many options to be opened. Different types of networks
are developed for diverse purposes, with a coverage stretching from a few metres to thousands of kilometers. This segment
will discuss the common networks that are used in telemedicine applications as well as explain the reason each network is best
suited for particular circumstances. Table 2.1 outlines the key properties.
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Table 2.1 Properties of some common wireless systems
FONG et al 2011
2.2.1 Bluetooth
Bluetooth technology provides confined coverage in room mo- bile equipment connected in an ad hoc system known as
piconet”. The main advantage of Bluetooth is low power utili- zation and minimal cost requiring simple hardware. However,
the disadvantage is the risk of spreading computer virus due to its flexibility in connecting gadgets which are close together.
Bluetooth utilizes adoptive frequency hopping AFH which recognizes other gadgets in the range and hops between 79 fre-
quencies at 1 MHz intervals to reduce EMI. By doing so, it keeps away from the frequencies used by close-by devices.
Bluetooth innovation is directed by the Bluetooth Special Inter- est Group SIG. Currently, there are three divisions which cov-
er distances around 3 meters, 30 meters, or 300 meters. Despite the fact that it is generally used in hands-free units of mobile
phones, it is convenient for tiny wearable bio sensors because of the use of cheap simple transceiver or low power usage which is
1 milliwatt for 3 meters or 10 feet, Class 3.
