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Wireless networks can be divided into two major segments: short-range and long-term. At short range wireless refers to networks that are restricted to a limited area. This applies to local area networks (LANs), such as corporate buildings, campuses, schools, factories or homes, as well as personal networks (PAN) where laptops close to each other have need to communicate. These networks operate over unlicensed spectrum typically set aside for industrial, scientific, medical (ISM) use. The frequencies available vary from country to country. The frequency band most commonly is 2.4 GHz, which is available in most of the planet. Other bands of 5 GHz and 40 GHz are also often used. The availability of these frequencies allows users to operate wireless networks without having obtained a license, and without charge.

WAN continue where the late local networks. Connectivity is typically provided by companies that sell wireless connectivity as a service. These networks cover important areas such as metropolitan area, state or province or entire country. The objective of long-haul networks is to provide wireless coverage in the world. The wide area network is the most common wireless WAN (WWAN). When a true global coverage is needed, satellite networks are also available.

Many of the wireless technology in the WPAN, WLAN, WWAN and categories of transmitting information by radio waves. For that to happen, the data are superimposed on the radio wave, which is also known as the carrier wave, because it carries data. This process is called modulation. There are numerous modulation techniques are available, all with advantages and disadvantages in terms of efficiency and power. The modulation techniques are:

1. narrowband technology - the narrow band radio systems transmit and receive data over a specific radio frequency. The band is kept as close as possible to allow information to be transmitted. Interference is prevented by coordinating different users on different frequencies. The radio receiver filters out all signals except those on the designated frequency. For a company to use the narrowband technology, it requires a license issued by the government. Examples of such companies include many vendors WAN.

2. Spread spectrum - By design, the craft spread spectrum off bandwidth efficiency for reliability, integrity and security. It consumes more bandwidth than the narrowband technology, but produces a signal that is stronger and easier to detect by receivers who know the parameters of the broadcast signal. For everyone, the spread spectrum signal looks like background noise. Two variants exist of spread spectrum radio skipping, frequency and direct sequence.

a). Frequency hopping spread spectrum (FHSS) - FHSS uses a narrowband carrier that has quickly made through the frequencies. The sender and receiver know the reason of frequency used. The idea is that even if a frequency is blocked, another should be available. While this is not the case, then the data is redirected. When properly synchronized, the result is a single logical channel on which information is transmitted. For everyone, it seems that short bursts of noise. The maximum rate of data using FHSS is typically around 1 Mbps.

b). Direct-Sequence Spread Spectrum (DSSS) - DSSS spreads the signal over a wide band of radio frequencies simultaneously. Each transmitted bit is a redundant bit pattern called a chip. Most of the chip, plus the original data can be recovered. Longer bits also require more bandwidth. For receivers do not expect the signal, DSSS appears as wideband noise low-power and is rejected. DSSS requires more power than FHSS, but data.