Apparatus and method for cell acquisition and downlink synchronization acquisition in a wireless communication system

A receiving method for a subscriber station (SS) in a broadband wireless communication system, comprising the steps of:

• acquiring subcarrier values having a preamble code from a fast Fourier transform (FFT) signal;
• code-demodulating the subcarrier values by multiplying the subcarrier values by a preamble code;
• calculating a plurality of differential correlations in the code-demodulated signal;
• inverse fast Fourier transform (IFFT)-processing the differential correlations by mapping the differential correlations to subcarriers and outputting an IFFT signal;
• and
• detecting a maximum value from the IFFT signal and calculating a timing offset using an IFFT output index having the maximum value.

An initial cell search method in a broadband wireless communication system, comprising the steps of:

• performing a first-order differential correlation on each of signals demodulated with all possible preamble codes and acquiring a cell having the highest first-order correlation, at an initial cell search;
• calculating a plurality of differential correlations by performing an nth-order differential correlation on the code-modulated signal of the acquired cell (1≦n≦nmax);
• inverse fast Fourier transform (IFFT)-processing the differential correlations by mapping the differential correlations to subcarriers and outputting an IFFT signal;
• and
• detecting a maximum value from the IFFT signal and calculating a timing offset using an IFFT output index having the maximum value.

A handoff target cell search method in a broadband wireless communication system, comprising the steps of:

• performing a first-order differential correlation on each of signals demodulated with the preamble codes of known neighbor cells and ordering the neighbor cells according to the first-order differential correlations, at a handoff target cell search;
• calculating a plurality of differential correlations by performing an nth-order differential correlation on each of the code-modulated signals of the neighbor cells (1≦n≦nmax);
• inverse fast Fourier transform (IFFT)-processing the differential correlations for each neighbor cell by mapping the differential correlations to subcarriers and outputting an IFFT signal for the each neighbor cell;
• and
• detecting a maximum value from the IFFT signal of the each neighbor cell and calculating a timing offset for the each neighbor cell using an IFFT output index having the maximum value.