Patent ID: 8488439
Filing Date: 2013-07-16
Classification: H04L

Abstract:
1. A method for estimating carrier frequency offset of a subscriber station by a base station for an uplink in an OFDMA communication system comprising: selecting a set of null sub-channels from among all null sub-channels of the OFDMA communication system; computing, in a signal processing device, signal energy leakage into said set of null sub-channels; calculating a cost function value using the computed value of the signal energy leakage; and adjusting said carrier frequency offset to minimize signal energy leakage into said set of null sub-channels; wherein calculating the cost function value and said adjusting said carrier frequency offset comprise: initializing a carrier frequency offset value to provide a carrier frequency offset reference value; initializing the cost function value to provide a cost function reference value; calculating a correction matrix; calculating the cost function value using at least said correction matrix; comparing said calculated cost function value with said cost function reference value and proceeding either, in the case that said calculated cost function value is greater than said cost function reference value, by returning said carrier frequency offset reference value as the estimated carrier frequency offset and terminating the method; or, in the case that said calculated cost function value is equal to or less than said cost function reference value, by setting said cost function reference value equal to said calculated cost function value and modifying said carrier frequency offset reference value; and repeating said calculating a correction matrix, said calculating a cost function value, and said comparing until either said calculated cost function value is greater than said cost function reference value, or a range of frequency adjustment is exceeded; and wherein said modifying said carrier frequency offset reference value comprises using a least mean squares method.