Frequency Wireless Networking (Basic)

Wireless networks can be divided into two broad segments: short-term and long term. Associated with short-range wireless network which is limited to restricted areas. This applies to local area networks (LAN), such as corporate buildings, school campus, factory or home, and also for personal area network (PAN) in which a portable computer in close proximity to each other need to communicate. These networks typically operate in unlicensed spectrum is reserved for industrial, scientific, medical ISM () usage. Frequencies available vary from country to country. The most common frequency band is at 2.4 GHz, which is available in most of the world. Another band at 5 GHz and 40 GHz are also often used. The availability of this frequency allows the user to operate the wireless network without obtaining a license, and without cost.

Long-term hold where the end of the LAN network. Connectivity is typically provided by a company that sells wireless connectivity as a service. Span a wide area network such as the metropolitan area, state or province, or across the country. Long-term objectives of the network is to provide global wireless coverage. Long range the most common wireless network is wide area network (WWAN). When a true global coverage is needed, the satellite network is also available.

Many wireless technology in the WPAN, WLAN, and WWAN categories transmit information using radio waves. For this to happen, data is superimposed on a radio wave, which is also known as a carrier wave, for carrying data. This process is called modulation. There are several modulation techniques are available, all with particular advantages and disadvantages in terms of efficiency and power requirements. Modulation technique is as follows:

1. Narrow technology - Narrow radio systems transmit and receive data at a specific radio frequency. Frequency band is stored as narrow as possible to allow information to be passed. Interference is avoided by coordinating different users on different frequencies. Radio receiver filters out all signals except on a designated frequency. For a company to use narrowband technology, requires a license issued by the government. Examples include many of the company's wide area network providers.

2. Spread spectrum - By design, the trade bandwidth efficiency of spread spectrum for reliability, integrity, and security. Consumes more bandwidth than narrow-band technology, but produces a signal louder and easier to detect by a receiver who knows the parameters of broadcast signals. For others, spread-spectrum signal looks like background noise. Two variations of existing spread-spectrum radio: frequency-hopping and direct-sequence.

a). Frequency-hopping spread spectrum (FHSS) - FHSS uses a narrow band carrier frequency rapidly through cycles. Both sender and receiver know the frequency pattern used. The idea is that even if a frequency is blocked, the others should be available. If this does not happen, then the data that is sent back. When properly synchronized, the result is a single logical channel where information is sent. For others, it appears as short bursts of noise. Maximum data rate using FHSS usually around 1 Mbps.

b). Direct-sequence spread spectrum (DSSS) - DSSS spread across the wide band radio frequency signals simultaneously. Each transmitted bit has a bit redundant pattern called a chip. The longer the chip, the more likely the original data can be restored. Longer bits also require more bandwidth. For the recipient does not expect the signal, DSSS appears as low-power broadband noise and rejected. DSSS requires more power than FHSS, but the data rate can be increased up to a maximum of 2 Mbps.

3. Orthogonal Frequency Division Multiplexing (OFDM) - OFDM transmits data by using parallel, rather than jumping technique used by the FHSS and deployment techniques that are used by DSSS. It protects from interference due to signals being transmitted through the parallel frequency. OFDM has Ultrahigh spectrum efficiency, which means that more data can travel over a smaller amount of bandwidth. It is effective for the transmission of high data-rate. The drawback of OFDM is that it is more difficult to implement than either FHSS or DSSS, and electricity consumed in large quantities.