Patent ID: 8005127

Claim:
An apparatus for operating a retransmission scheme in a cellular communication system, the apparatus comprising: means for receiving a retransmission feedback message on a first channel, the retransmission feedback message comprising at least one retransmission feedback symbol spread by a first spreading code having a first spreading factor; means for generating a noise estimate for the retransmission feedback symbol; threshold means for determining a detection threshold in response to the noise estimate; and determining means for determining if the received retransmission feedback message is a retransmission request in response to the detection threshold; and wherein the means for generating the noise estimate comprises sub-symbol generation means for dividing the retransmission feedback symbol into a plurality of sub-symbols, each sub-symbol being despread by a second spreading code having a second spreading factor smaller than the first spreading factor, difference means for generating difference symbol values between the plurality of sub-symbols, and estimate means for generating the noise estimate in response to the difference symbol values.