Original Publication Date: 2001-Dec-01
Included in the Prior Art Database: 2003-Jul-23
The SNIR (Signal to Noise and Interference Ratio) is needed for:
Information / Kommunikation
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...