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SNIR-Evaluation Disclosure Number: IPCOM000018034D
Original Publication Date: 2001-Dec-01
Included in the Prior Art Database: 2003-Jul-23
Document File: 2 page(s) / 163K

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Yingije Gao: AUTHOR


The SNIR (Signal to Noise and Interference Ratio) is needed for:

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Idee: Yingije Gao, Bocholt

•   noise from components in analogue base bandparts

•   noise  in  digital  part  –  auto  correlation  noise(finite length of scrambling code)

The SNIR (Signal to Noise and Interference Ratio) isneeded for:

•   Evaluation of receiver performance together withBER, especially in non-lab environments, whereSNIR preconfiguration is not feasible.

•   Power control

A simple block diagram of a CDMA communicationsystem is shown in figure 1. There are not only exter-nal noise (N 0 ) and external interference (I) but alsointernal influences in a communication system. Theinternal influences mainly consist of:

•   noise in RF part – N tx  and N rx  (EVM)

•   error in receiver algorithms – AFC, searcher andcombiner.

•   Quantisation error of A/D and D/A converter.

In order to compare the BER with QPSK theory allinternal and external influence in the real system haveto be considered. So the SNIR should be evaluated inthe physical layer – rake part.

Normally the SNIR is calculated in the rake combi-ner, because the symbols are corrected with channelcoefficients. The main problem of the SNIR calcula-tion in rake combiner is to determine the noise andinterference power.

In figure 2 a impulse response of pilot symbols isshown,  which  is  achieved  after  correlation  of  re-ceived signal in the match filter. The same operation

for the pilot symbols are also done for different fingerpositions in rake combiner. In the MRC (MaximalRatio Combining) the receiver symbols are weightedwith the channel coefficients.

The SNIR is then calculated:

SNIR = S r  / N m ,

where S r  is the signal energy calculated in rake com-biner  and  N m  is the  noise  and  interference  energycalculated in match filter.

This is  the  invention  of  SNIR  evaluation  methodusing the noise and interference energy in match filterand the symbol energy in rake combiner.

Evaluation of receiver performance: BER (Bit ErrorRate)  –  measurements  with  two  SNIR  evaluationmethods are shown i...