SHORT AND LONG DISTANCE WIRELESS COMMUNICATIONS
Wireless communication may be differentiated based on the region it covers into short distance and long distance wireless communication.
• Short Distance Wireless Communication:-
Short distance wireless communication consists of very short distance of few meters (infra-red) to a distance of up to 50 Km (Wi-Max). Following are the types of short distance wireless communications.
• Long Distance Wireless Communication
Long distance wireless Communication comprises of distances above 50 Km using either cellular communication methods or Global Positioning Systems which utilizes satellites.
• SHORT DISTANCE WIRELESS COMMUNICATION
Wi-Fi (Wireless Fidelity) is a wireless communication system very Commonly used at home and office. It is also called WLAN (Wireless LAN). It is a popular wireless networking technology which uses radio waves to provide wireless high-speed internet and network connections. Wireless networks are easy to setup and are inexpensive. In Wi-Fi, information travels over the air. These networks are extremely limited in range due to low power o transmissions allowing users to Connect only within close proximity to a router or signal repeater. Wi-Fi is common in home networking applications which provides portability without any need of cables. Wi-Fi networks need to be secured with passwords for security purposes in order not to be accessed by others.
Wi-Max (Worldwide interoperability for Microwave Access) is a wireless network that provides public network service to users. It is very similar to Wi-Fi but covers a big range of 40 to 50 Km. Wi-Max Creates a Metropolitan Area Network (MAN) and provides a wireless alternative to Cable TV and DSL Internet connection. It provides service just about anywhere you go within a city. It transmits information through microwave and uses a more complex technology than Wi-Fi.
Bluetooth is a short-range and low speed wireless Communication technology. Its range is around 10 meters with the data transfer rate up to 723 Kbps and it consumes low power. It provides a way to connect and exchange information between devices such as mobile phones, laptop Computers, PCs, printers, digital cameras, and video game consoles. Bluetooth can be
used to replace cables between the PC and the linking devices such as printers, keyboards, mouse, etc.
infra-red (IR) waves are extremely high frequency waves which are used for short range communication. Some common applications of infrared technology are listed below.
Car locking systems use infrared technology for automatic locking and unlocking the doors of cars.
Modern Computers have infrared enabled mouse, keyboards, and printers. in Home security systems have infrared enabled burglar alarm system. o Remote control system in TVs, Toys, etc uses infrared technology.
• LONG DISTANCE WIRELESS COMMUNICATION
Long Distance wireless communication systems provide services that are not possible with the use of cables. It includes cellular and global positioning systems.
• CELLULAR COMMUNICATION
Cellular communication refers to wireless communication systems that divide a geographical region into sections called cells. Each cell has a Base Station (BS) at the center that contains a transceiver and controller that provides radio communication to mobile phones.
In cellular Communication, each mobile phone uses a separate temporary radio frequency (channel) to talk to the Base Station (BS). The BS talks to many mobile users at the same time as shown in Fig.6.5. Channels use a pair of frequencies for communication. One frequency, the uplink is used for the mobile phone to Communicate with the BS and another frequency for the down link for BS to Communicate with the mobile phone. The basic concept of cellular communication is that it reuses the radio frequency by the cell that as at a distance where there is no interference Of the Other.