Patent ID: 8040790

Claim:
A low complexity bandwidth efficient method for estimating carrier frequency offset in orthogonal frequency division multiple access (OFDMA) and/or single carrier frequency division multiple access (SC-FDMA) up link transmissions in a communication network system comprising a group of subscriber stations, a base station including carrier frequency offset unit, said method comprising: (a) transmitting plurality of null subcarrier signals and data subcarrier signals, said subcarrier signals comprising N-dimensional vector having cyclic prefix, from plurality of said subscriber stations (SS) to the base station; (b) processing said transmitted subcarrier signals at the base station by estimating carrier frequency offset (CFO) by means of carrier frequency offset unit; (c) selecting the subcarrier signals based on carrier assignment scheme (CAS); wherein the estimating carrier frequency offset comprises: (i) generating a trial carrier frequency offset (CFO) vector thereafter point to point multiplying the N-dimensional received signal vector after removal of the cyclic prefix with the trial carrier frequency offset (CFO) vector; (ii) adding total energies of substantially all signals of designated null subcarrier locations; (iii) comparing added value of energies as resulted in step (ii) with previously stored null subcarrier energy if any corresponding to previous iteration to obtain a minimum energy; (iv) storing said minimum energy value and the corresponding trial carrier frequency offset value; (v) repeating the process until all the trial values are over; (vi) identifying the trial carrier frequency offset value corresponding to the minimum energy as the estimated carrier frequency offset; and (vii) performing the steps mentioned in (i)-(vi) simultaneously for all the users in the system.