Okaay.. this is our next discussion,
it is all about Wireless and Mobile Computing…
What is Wireless and what is Mobile? Basically, it is difference. But today, technology makes it become one each other. When you see a mobile device, it could do Wireless thing and do a Mobile Computing. Let me tell you about the definition.
Wireless is come from Wire and less, it means no need of wired things to do.
Wireless device : is a device who have an ability to communicated without wire.
The Example of device which have a wireless technology is : PDA, Cell Phone, Smartphone, Wireless Mouse / Keyboard, Laptop, Pager, and many other. On the wireless technology there is a protocol which is a rule that makes the communication run smoothly, it is called Wireless Application Protocol. It is the standard that enables wireless devices with tiny display screens, low bandwidth connection and minimal memory to access web-based information and services.
Another wireless technology is Opera mini browser, this is a type of Microbrowsers which have a function as an internet browser with small file size that can work within low memory of wireless device and the low bandwidth of wireless network. Opera mini, could compress the web to be become lighter and use low bandwidth. The Opera mini, use the picture to compress the bandwidth.
Wireless Transmission Media
The difference between Radio waves and microwaves
There is no clear difference between radio waves and microwaves. Electromagnetic waves ranging in frequencies between 3KHz and 1 GHz are normally called radio waves. Waves ranging in frequencies between 1 and 300 GHz are normally called microwaves.
Radio Waves Signal
Radio waves are normally omnidirectional. When an antenna transmits radio waves, they are propagated in all directions. This means that the sending are receiving atennas do not have to be aligned.
The omnidirectional characteristics of radio waves make them useful for multicasting, in which there is one sender but many receivers. Our AM and FM radio stations, cordless phones and television are examples of multicasting
The Disadvantage of Radio Waves
Radio waves transmitted by one antenna are susceptible to interference by another antenna that is sending signals of the same frequency or band.
Electronic waves with frequencies between 1GHz to 300GHz are normally called microwaves. Unlike radio waves, microwaves are uniderctional, in which the sending and receiving antennas need to be aligned.
Microwaves propagation is line-of-sight therefore towers with mounted antennas need to be in direct sight of each other. Due to the unidirectional property of microwaves, a pair of antennas can be placed aligned together without interfering with another pair of antennas using the same frequency.
The disadvantage of the microwaves
High-frequency microwaves cannot penetrate walls. This is why receiving antennas cannot be placed inside buildings.
Infrared is used in devices such as the mouse, wireless keyboard and printers. Some manufacturers provide a special port called the IrDA port that allows a wireless keyboard to communicate with a PC.
Infrared signals have frequencies between 300GHz to 400THz. They are used for short-range communciation.
Infrared signals have high frequencies and cannot penetrate walls. Due to its short-range communication system, the use of an infrared communication system in one room will not be affected by the use of another system in the next room.
This is why using an infrared TV remote home will not interfere with the use of infrared TB remote control.
The disadvantage of using infrared
Infrared signal cannot be used for long distance communication. In addition, we cannot use infrared waves outside a building because sun’s ray contain infrared waves that can interfere waves that can interfere with communication.
The use of satellite to communicate, the wider area makes satellite is suitable for large area communication. Such as GPS, Internet, Television, and other communication needs.
there are three types of the orbit :