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Tuesday, 10 August 2010

Adaptive Multipath Detection

For achieveing a better Eb/N0 (little energy to the noise ratio) than the todays Rake receiver, there will be a better estimation of the radio channel is needed. This Seminar Topic is proposes to reaching this Goal by an artificial N/w, which is used for detecting all the multipaths in direct sequence spread spectrum signal. The 0/P of this adaptive neural is the extimation of channel response. To increasing the Eb/N0 of the direct Sequence Spread Spectrum Signals. Rake receivers consists of upto six demodulators. Which demodulates strongest few echoes of Signal. Their O/P signals will be collected. The result will be higher stability against the noice.

Presented work also based using not only 1 path for the reconstructing transmitted bit stream, but nearly all the paths. The received PN(pseudo noise) radio signal is simpled with rate of about 4 times chip rate of PN Signal & passed through a despreader that correlate it with original PN Sequence.

In contrasting to conventional receiver, correlation is made for every delay, which is realised in correlator bank whose O/P is given to neural N/W. As the neural net, a perseption with the backpropagation is used, with the task to detect all multipaths in correlated signal. With the conventional filters, the problem of detecting only multipath peaks & not peaks due to the crosscorrelation of PN Sequence with the inverted PN Sequence which is occuring whenever the bit change from one to -minus one or inverse, which is nearly impossible for handling. The O/P of the net is estimated response of actual channel. With this information containing delay & the attenuation of each of the propagation path, the transmitted bit stream can be easily rebuilt...


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