Introduction Of Smart Antennas

The chief goal of wireless communications research has long been to enhance user capacity, data rates, and channel reliability. User capacity refers to the number of subscribers that can be simultaneously serviced by a wireless system. Increasing data rates allows subscribers to enjoy new services such as multimedia and broadband internet access. Improving channel reliability reduces symbol error rates or reduce the chance of dropprd calls.                                                                

Major obstacles to these goals include channel fading, noise, interference, and frequency selective distortion. While these detrimental effects can be most easily combated by increasing spectrum usage or increasing the number of basestations in a system, these solutions are expensive options. Spectrum licenses and basestation site location are among the most costly components of a cellular communication system. An antenna array consists of distributed antenna elements whose outputs are combined or selected and is a practical tool for enhancing wireless system performance. A smart antenna is an antenna array system aided by some smart algorithm designed to adapt to different signal environments. Software radios and smart antennas complement each other well. Software radios provide the flexibility needed for effective smart antennas, and smart antennas provide the benefits that motivate the adoption of software radios.

In short, smart antennas mitigate fading through diversity reception and beamforming while minimizing interference through spatial filtering. It is impossible for a single smart antenna system to be ideal for all these tasks. Certain array designs are more suited for interference rejection than diversity reception and vice versa, and these functions are often at odds. In the next section these functions are discussed more.

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