WNDR3700v3 Noise Level

Hi,

Using only the (partially supported) 2.4 GHz band, but all the time the noise level is reported as 0 dBm. I checked with iwinfo, and the data doesn't seem to be there. Is this a known issue (and is there a fix)?

iwinfo wlan0 info
Signal: -41 dBm Noise: unknown

Thanks!