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LTE Cell Search: Why we have two PSS located in a 10 msec frame?

+2 votes

While going through the docs it is understood that in initial Cell search mechanism first UE detects PSS (Primary sync signal) and then SSS (secondary sync signal). Following are my queries -
1) Why we have two PSS located in a 10 msec frame?
2) Why SSS appears before PSS . in actual it should be PSS and then followed by SSS.
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posted Oct 28, 2015 by anonymous

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1 Answer

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The UE first looks for the primary synchronization signal (PSS) which is transmitted in the last OFDM symbol of the first time slot of the first subframe (subframe 0) in a radio frame.
This enables the UE to acquire the slot boundary independently from the chosen cyclic prefix selected for this cell. Based on the downlink frame structure ( FDD).
The primary synchronization signal is transmitted twice per radio frame, so it is repeated in subframe 5 (in time slot 11). This enables the UE to get time synchronized on a 5 ms basis, which was selected to simplify the required inter-frequency and inter-RAT measurements.

answer Oct 29, 2015 by Manohar
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