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Average SNR Definition CID 3241. Date: 2007-09-17. Authors:. CID 3241 Text. CID 3241. Discussion. Together with CSI and compressed/uncompressed matrix feedback, average SNR values are provided.
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Average SNR Definition CID 3241 Date: 2007-09-17 Authors: Vinko Erceg, Broadcom Corporation
CID 3241 Text CID 3241 Vinko Erceg, Broadcom Corporation
Discussion • Together with CSI and compressed/uncompressed matrix feedback, average SNR values are provided. • In the current 802.11n Draft (2.07), the average SNR is defined as “dB value of the linear average” for CSI and compressed/uncompressed feedback cases. • For the CSI case, the average SNR represents: • SNR in Rx channel 1:Nr • 8 bits • Signal to Noise Ratio in 1:Nr Rx chains of the STA sending the report. Vinko Erceg, Broadcom Corporation
Discussion: Cont’ • For the compressed/uncompressed case, the average SNR has quite different meaning: • SNR for stream 1:Nc • 8 bits • Average Signal to Noise Ratio in the STA sending the report for stream 1:Nc. Vinko Erceg, Broadcom Corporation
Discussion: Cont’ • For the CSI feedback average SNR represents Rx chain SNR but for compressed/uncompressed feedback it represents SNR per spatial stream. • These are 2 different SNRs that are often regarded as “pre-processing SNR” in the case of the CSI feedback and “post-processing SNR” in the case of the compressed/uncompressed feedback. • They require different SNR definition. Vinko Erceg, Broadcom Corporation
Discussion: Cont’ • In the CSI feedback case average SNR is well represented by dB value of the linear average since it represent average SNR in the Rx chain (same as the current definition in the draft). However, • In the compressed/uncompressed feedback case it is more accurate to use average of the SNR values in dB since SNR per stream (post-processing) better relates to the capacity equation and therefore better representation of MCS. In MIMO case capacity equation includes log( f(SNR) ). Therefore, average of dB values is a natural choice. Vinko Erceg, Broadcom Corporation
Conclusion We propose the following: • In the CSI case average SNR is determined as a dB value of linear average. • In the compressed/uncompressed case average SNR is determined as an average of dB values. Proposed text is included in 07/2400r2 Vinko Erceg, Broadcom Corporation