Method and arrangement for noise variance and sir estimation

摘要

A method and arrangement (300) for noise variance and SIR estimation in a UTRAN Node B (122) or User Equipment (118) estimates the SIR (SIR<(1)>...SIR<(K)>) at the output of a detector (310) by using an estimate of the detector input noise variance to provide an estimate of the detector output noise variance. The detector input noise variance is derived from a midamble portion (220) in the received signal. By deriving the transfer function of the detector an estimate of the detector output noise variance is estimated. The estimated output noise variance then allows an improved estimate of the SIR (SIR<(1)>...SIR<(K)>) at the detected output. The accuracy of this technique is not poor at low SIR, since it does not suffer from a bias term, nor does it require correction therefor using a look-up table. Also, any increase in estimation variance resulting from bias correction may be avoided.