Electromagnetic Interference Wireless Communications

37 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. 38

2.2.2 Infrared IR

Infrared waves are located between microwaves and visible red light in the spectrum. The sun emits an appreciable amount of infrared radiation that is associated with heat. An almost equivalent amount of visible light and infrared from the sun will hit the surface of the earth. Let us examine how these rays affect communications and healthcare. Generally, the application of infrared waves extends to detection by night vision which is significant in search and rescue operations. Common uses of infrared waves in wireless communication include the control of home appliances using a remote device. When we use the re- mote control to adjust the volume of a stereo, the controller dis- charges an infrared signal that conveys the instruction to the sensor in the stereo. The International Commission on Illumina- tion CIE classifies infrared into three separate categories, of which near-infrared or IR-A is utilized in night vision applica- tions while short-wavelength infrared IR-B is used in wireless communications. Infrared waves of short wavelengths are used extensively in long range optical communications. However, this study shall not dwell into the details of this and concentrate only on wireless networking. The Infrared Data Association IrDa manages the IR wireless guidelines for gadgets that use the progressive on and off of an infrared Light Emitting Di- odes LED for communication. A silicon photo-diode at the receiver alters the received infrared pulses to an electric current reproducing the sequence of on and off. This is a developed innovation that has been used for years and quite simple to use without any interference issues. However, it cannot pass through walls. In addition, a direct LOS is prerequisite and the transmitter must be placed fairly near the center of the sensor with just + - 15 ◦ offset possible. Even though the present IrDa compatible devices are only able to support speeds up to 16 Mbps, the adoption of Giga-IR offers a hypothetical transmis- 39 sion speed of up to 1 Gbps. It is frequently used in small ECG fragment transmission.

2.2.3 Wireless Local Area Network WLAN and Wi-Fi

The IEEE 802.11 guidelines are quite broadly used in wireless home systems, providing convenient access to the internet at minimal cost to the user. WLAN is different from Bluetooth and IR, and it requires a few deliberations in configuring the initial requirements before a communication link could be initialized. Popular IEEE 802.11 guidelines include abgn; these norm values describe the specifications for the physical layer PHY that defines how raw data bits are transmitted over the air and the WLANs Medium Access Control Layer MAC that pro- vides address and channel access control methods which per- mits numerous gadgets to correspond with each other via a single Access Point. Besides the 802.11a which clocks at speeds of around 5 Ghz, the remaining three standards are running at 2.4 Ghz. Being confined to this frequency band, interference may occur due to other appliances adopting similar frequencies, for example mi- crowave ovens, cordless telephones and other Bluetooth devic- es. Depending upon its usage, the coverage area of WLAN fluctuates enormously- namely indoor or outdoor usage ranging from 50 to 300 meters respectively. The construction of a basic WLAN connection generally comprises of one access point AP at the least, which one or several mobile clients MC, tries to establish a communication to the network through the AP. MCs are fundamentally any mobile gadget that is able to establish this communication. A wireless networking infrastruc- ture is formed when the APs are set in different locations throughout the broadcasting area. In a basic configuration of WLAN there is one AP in the focal point surrounded by one or more MCs. The network coverage zone could be expanded by