A receiver circuit for estimating a state of an uplink channel between a wireless communication unit and a base station in a wireless communication system computes a conditioned Channel Impulse Response (CIR), the amount of conditioning being based on the noise present in the channel. A CIR and a Noise Variance are estimated from a Sounding Reference Signal received from the wireless communication unit. The estimated CIR is conditioned by comparing it with an adaptive threshold value selected from a look up table that lists threshold values against Noise Variance values. The threshold value further conditions the CIR to eliminate noise and interference. The conditioned CIR is converted into the frequency domain and used to provide a channel gain estimate which, together with noise estimates, is used to determine a Signal to Interference Noise Ratio (SINR) for the channel.