Eigenvector-based initial ranging process for OFDMA uplink systems

At the contention-based synchronization, e.g., initial ranging process, it is crucial to identify multiple users through ranging codes and estimate the corresponding parameters such as timing offset and frequency offset. This paper presents an improved parameter estimation and pairing algorithm for initial ranging process in orthogonal frequency-division multiple access (OFDMA) uplink systems by exploiting multidimensional harmonic retrieval (HR) technique. Unlike most existing techniques that estimate each parameters independently and associate the ranging codes with the estimated parameters manually, the proposed method estimates multiple user’s ranging code, timing and frequency offsets simultaneously, and pair up all the multiple parameters automatically. The simulation results confirm that the proposed technique not only improves the ranging code detection capability and adjusts the acquisition range of the estimators but also increases the maximum number of resolvable users for given samples.