Apparatus for detecting uplink ranging codes in a wireless communication system

1. An apparatus comprising:

a first transform unit configured to receive as input data from a mobile station and to perform operations for transforming data received from the mobile station to generate a plurality of first outputs;

a cross-correlation unit configured to receive the first outputs from the first transform unit and configured to compare the first outputs with possible ranging codes to generate a plurality of second outputs;

a selective output unit configured to receive the second outputs from the cross-correlation unit and to selectively output portions of the second outputs that match one or more of the ranging codes;

a second transform unit configured to receive the portions of the second outputs that are output by the selective output unit and to perform operations for transforming the portions of the second outputs to generate a plurality of third outputs; and

a detection unit configured to receive the third outputs and to detect the ranging codes for the received data based on the third outputs.

2. The apparatus of claim 1 , wherein the first transform unit utilizes a Fast Fourier Transform to perform the operations for transforming data received from the mobile station.

3. The apparatus of claim 1 , wherein the second transform unit utilizes an Inverse Fast Fourier Transform to perform the operations for transforming the received portions of the second outputs.

4. The apparatus of claim 1 , further comprising a switch coupled to the cross-correlation unit and configured to selectively supply the second outputs to the second transform unit or to the selective output unit depending on whether one or more predetermined criteria are met, such that when the one or more predetermined criteria are met the switch supplies the second outputs to the second transform unit and bypasses the selective output unit.

5. The apparatus of claim 4 , wherein the switch is configured to supply the second outputs to the second transform unit and to bypass the selective output unit when a ranging code book providing the possible ranging codes has a size smaller than a predefined value.

6. The apparatus of claim 4 , wherein the switch outputs the second outputs to the selective output unit when the number of ranging codes detected by the detection unit is smaller than a predetermined threshold.

7. The apparatus of claim 1 , wherein the detection unit is further configured to estimate a time offset of the data received from the mobile station.

8. The apparatus of claim 7 , wherein the detection unit estimates the time offset by comparing the third outputs from the second transform unit with a set of predetermined signal distribution patterns of the possible ranging codes and by determining peak locations of the distribution patterns.

9. The apparatus of claim 1 , wherein the detection unit is further configured to estimate a frequency offset of the data received from the mobile station.

10. The apparatus of claim 1 wherein the detection unit is further configured to acquire power adjustment information of uplink signals associated with the mobile station based on the detected ranging codes.

11. The apparatus of claim 1 , wherein the selective output unit is configured to selectively output portions of the second outputs that match one or more of the ranging codes such that computing demands for the second transform unit are reduced.

12. A method comprising:

at a base station, receiving data from a mobile station;

first transforming the data received from the mobile station with a Fast Fourier Transform to generate a plurality of first outputs;

comparing the first outputs with possible ranging codes to generate a plurality of second outputs;

selectively outputting portions of the second outputs that match one or more of the possible ranging codes, when a predetermined criterion is met;

second transforming the portions of the second outputs with an Inverse Fast Fourier Transform to generate a plurality of third outputs; and

detecting the ranging codes for the received data based on the third outputs.

13. The method of claim 12 , wherein selectively outputting portions of the second outputs is not performed when the predetermined criterion is not met.

14. The method of claim 13 , wherein the second transforming comprises transforming the portions of the second outputs when a ranging code book providing the possible ranging codes has a size larger than a predefined value.

15. The method of claim 13 , wherein second transforming comprises transforming the portions of the second outputs when a number of the portions of the second outputs that match the ranging codes is smaller than a predetermined threshold.

16. The method of claim 12 , further comprising estimating a time offset of the data received from the mobile station.

17. The method of claim 16 , wherein estimating comprises estimating the time offset by comparing the third outputs with a set of predetermined signal distribution patterns of the possible ranging codes and by determining peak locations of the distribution patterns.

18. The method of claim 12 , further comprising estimating a frequency offset of the data received from the mobile station.

19. The method of claim 12 , further comprising acquiring power adjustment information of uplink signals associated with the mobile station based on the detected ranging codes.

20. The method of claim 12 , wherein selectively outputting comprises outputting portions of the second outputs that match one or more of the ranging codes such that computing demands are reduced for the second transforming of the portions of the second outputs.