SMART ANTENNA
B.GANGADHAR
08QF1A1209
ABSTRACT
One of the most rapidly developing areas ofcommunications is “Smart Antenna” systems. Thispaper deals with the principle and working of smartantennas.
The main use of smart antennas in mobilecommunications that enhances the capabilities ofthe mobile and cellular system such a faster bit rate,multi use interference, space division multiplexing(SDMA),increase in range, Multi path Mitigation.
one great advantage that is a very high security. Thesignal that is been transmitted by a smart antennacannot tracked or received any other antenna thusensuring a very high security of the datatransmitted.
INTRODUCTION:
What is a smart antenna?
A smart antenna is an array of antenna elements connected to adigital signal processor. Such a configuration dramaticallyenhances the capacity of a wireless link through a combination ofdiversity gain, array gain, and interference suppression.Increased capacity translates to higher data rates for a givennumber of users or more users for a given data rate per user.
PRINCPLE OF WORKING:
The smart antenna works as follows. Each antennaelement "sees" each propagation path differently,enabling the collection of elements to distinguishindividual paths to within a certain resolution.
A smart antenna receiver can decode the data from asmart antenna transmitter this is the highest-performing configuration or it can simply providearray gain or diversity gain to thedesired signalstransmitted from conventional transmitters andsuppress the interference.
The smart antenna can also separate the signals frommultiple users who are separated in space but whouse the same radio channel this application is calledSpace-division multiple access (SDMA).
APPLICATIONS IN MOBILECOMMUNICATIONS:
Smart antenna is capable of forming transmit/receivebeams towards the mobile of interest. At the sametime it is possible to place spatial nulls in thedirection of unwanted interferences. This capabilitycan be used to improve the performance of a mobilecommunication system.
Increased antenna gain:
The ’smart’ antenna forms transmit andreceive beams. Therefore, the’smart’ antenna has ahigher gain than a conventional omni-directionalantenna. The higher gain can be used to eitherincrease the effective coverage, or to increase thereceiver sensitivity, which in turn can be exploited toreduce transmit power and electromagnetic
radiation in the network.
Decreased inter-symbol-interference (ISI)
Multipath propagation in mobile radio environments leads to ISI.Using transmit and receive beams that are directed towards themobile of interest reduces the amount of Multipath and ISI.
Decreased co-channel-interference (CCI)
’Smart’ antenna transmitters emit less interference by onlysending RF power in the desired directions. Furthermore, ’smart’antenna receivers can reject interference by looking only in thedirection of the desired source. Consequently ’smart’ antennas arecapable of decreasing CCI. A significantly reduced CCI can be takenadvantage of by Spatial Division Multiple Access (SDMA) o The samefrequency band can be re-used in more cells, i.e. the so calledfrequency re-use distance can be decreased. This technique is calledChannel Re-use via Spatial Separation.
CONCLUSION:
In conclusion to this paper “Smart Antenna”systems are the antennas with intelligence andthe radiation pattern can be varied without beingmechanically changed. As the system uses a DSPprocessor the signals can be processed digitallyand the performance is with a high data ratetransmission and good reduction of mutual signalinterference.