Saturday, 10 January 2015

Beamforming


Beamforming
Beamforming – Signal Processing Technique

Beamformingor spatial filtering is one of those concepts, a kind of signal processing technique which is used in sensor arrays for directional signal transmission or reception which is achieved on combining elements in a phased array. It is done in a way that signals at certain angles experience constructive interference while others experience destructive interferences. Beamforming could also be used at transmitting as well as receiving ends to achieve spatial selectivity.

It could also be used for sound waves or radio and has various application in wireless communication, radar, sonar, seismology, radio astronomy, acoustic and bio medicine.To identify and estimate the signal of interest at the output of a sensor array, adaptive beamforming is used by means of optimal spatial filtering and interference rejection. The most effective form of beamforming is dynamic digital beamforming which uses an advanced on-chip digital signal processing – DSP algorithm, in order to gain total control on Wi-Fi signals. Performance has improved on creating several independent signal paths to optimum focus radio energy to and from client devices on a per packet basis. For a two stream configuration, there is a possibility to steer the energy of the antenna array in the independent spatial direction which are associated on both data streams and at the same time avoids interference.

Improves Wireless Bandwidth Usage

Beamforming could also help in improving wireless bandwidth usage and can also increase wireless network’s range which in turn could improve voice streaming, video streaming together with several other bandwidth and latency sensitive transmissions. It is made possible by receivers and transmitters using MIMO – multiple-input, multiple-output, technology wherein the data is sent as well as received with the use of multiple antennas in order to increase throughput and range.

The MIMO technology was introduced first with the 802.11n standard and continues to be an important feature of the 802.11ac standard. Devices which support beamforming, aim their signals on each client, focusing on the data transmission in order that more data could reach the targeted device instead of radiating out in the atmosphere. Beamforming technique can be divided into two sections namely conventional or fixed/switched beam, beamformers and adaptive beamformers or phased array – desired signal maximization mode/interference signal minimization or cancellation mode.

Conventional/Adaptive Beamforming Techniques

Fixed set of weightings and time delays or phasing are used for conventional beamformers for the purpose of combining the signals from the sensors in the array, using only the information with regards to the location of the sensors in space as well as the wave directions. In the case of adaptive beamforming techniques, the information is combined with properties of the signals received by the array to improve rejection of unwanted signals from other directions, the process of which could be carried out in time or frequency domain. Beamforming being computationally intensive, Sonar phased array has a low data rate which can be processed in real time in software which is flexible to transmit and or to receive in various directions at the same time.

 Radar phased array on the other hand has a high data rate which usually needs dedicated hardware processing which is hard-wired to transmit and or to receive in one direction only at a time, though new field programmable gate arrays are quick to handle radar data in real time and could also be quick in reprogramming, like software, blurring the hardware/software distinction.

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