14Oct Wireless Lan

The wireless networking community is working with two spread spectrum technologies as the basis of their transmission method. In spread spectrum transmissions, the frequency of the radio signal hops in a random, defined sequence that is known to the receiving device. These technologies are referred to as Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS). The FHSS method spreads the signal across the time spectrum using Time Division Multiplexing (TDM) techniques. The DSSS method combines the data with a faster carrier signal according to a predetermined frequency spreading ratio for transmission.

 Time Division Multiple Access (TDMA) technology employs TDM to divide a radio carrier signal into time slices, called cells, and then funneling data from different sources into the cells. This technique enables a single frequency signal to serve a number of different sources into the cells. This technique enables a single frequency signal to serve a number of different customers simultaneously. A similar technology known as CDMA (Code Division Multiple Access) does not assign users a specific frequency. Instead, it spreads the user’s data across a range of frequencies in a random digital sequence.

 A typical wireless LAN consists of wireless LAN adapter cards with an RF antenna. The WLAN adapter cards in the various systems of the LAN communicate with each other and a host system through an access point device. Current wireless LAN operates in the range of 1 Mbps transfer rates. Wireless LAN adapters are typically available in the form of PCI and PCMCIA cards.

 Another interesting wireless networking specification is known as Bluetooth. Wireless radio technologies designed to coordinate communications between network devices and the internet. The meshing together of pc, cell phones, web devices, LAN devices and other intelligent devices in a common forum is referred as convergence. Wireless networks connect computer nods together using high frequency radio waves.