Method of cell search

1. A method of cell search for a mobile device in a wireless communication system, the method comprising:

performing a reception timing detection procedure, to obtain at least a possible reception time for a primary synchronization signal (PSS);

performing a PSS hypothesis procedure, to generate three frequency-domain PSS sequences according to three root indexes each corresponding to a physical layer identity;

performing a secondary synchronization signal (SSS) coherent detection procedure, to calculate a SSS sequence according to each of the at least a possible reception time with the three frequency-domain PSS sequences, to obtain a physical layer cell identity group corresponding to the SSS sequence, wherein the SSS coherent detection procedure includes a fast-hardmard transform operation; and

performing a check procedure to determine whether the SSS sequence is detected, wherein the check procedure comprises:

determining that the SSS sequence is detected, and obtaining a corresponding physical layer cell identity group when the fast-hardmard transform operation result is greater than a predetermined value; and

determining that the SSS sequence is not detected when the fast-hardmard transform operation result is smaller than the predetermined value.

2. The method of claim 1 , wherein the reception timing detection procedure comprises:

receiving a wireless signal from the wireless communication system;

performing a decimation procedure on the received wireless signal to reduce a data rate of the received wireless signal to a sample rate of the PSS;

performing correlation on the decimated wireless signal and three time-domain PSS sequences, wherein the time-domain PSS sequences include a first, a second and a third time-domain PSS sequences generated by the mobile device according to a first, second and third root indexes respectively;

generating a calculation result based on a non-coherent combining operation with the maximum value outputted from a first, a second, and a third correlation results in each sample time of a PSS transmission period; and

comparing the calculation result with a predetermined value, for determining whether the PSS is detected.

3. The method of claim 2 , wherein the step of comparing the calculation result with the predetermined value, for determining whether the PSS is detected, comprises:

determining that the PSS is detected when the calculation result is larger than the predetermined value, and determining the sample time corresponding to the calculation result as a reception time of the PSS; and

determining that the PSS is not detected when the calculation result is smaller than the predetermined value.

4. The method of claim 1 , wherein the SSS coherent detection procedure includes a PS S channel estimation operation, and a coherent combining operation.

5. The method of claim 1 , further comprising:

calculating a physical layer cell identity corresponding to a cell based on the obtained physical layer cell identity group and a first, a second or a third physical layer identity, in which the first, second and third physical layer identities respectively correspond to the three frequency-domain PSS sequences for the SSS coherent detection procedure; and

performing a successive interference cancellation procedure, wherein the successive interference cancellation procedure includes steps:

generating a first PSS sequence and a first SSS sequence in the frequency domain based on the physical layer cell identity group and the first, second or third physical layer identity;

performing a channel estimation corresponding to the first SSS sequence;

re-generating a second PSS and a second SSS based on the channel estimation result, the first PSS sequence and the first SSS sequence, in which each of the second PSS and the second SSS is a part of the synchronization signal; and

obtaining a third PSS by removing the re-generated second PSS from the PSS, and obtaining a third SSS by removing the re-generated second SSS from the SSS.

6. The method of claim 1 , further comprising:

determining whether the SSS coherent detection procedure are performed on the three frequency-domain PSS sequences with a first reception time of the at least a reception time when the SSS is determined to be not detected;

performing the SSS coherent detection procedure on the three frequency-domain PSS sequences with a second reception time when the SSS coherent detection procedure are performed to all of the three frequency-domain PSS sequences with the first reception time; and

performing the SSS coherent detection procedure on the three frequency-domain PSS sequences with the first reception time when the SSS coherent detection procedure is not performed to all of the three frequency-domain PSS sequences with the first reception time.

7. A method of detecting primary synchronization signal (PSS) reception time for a mobile device in a wireless communication system, the method comprising:

receiving a wireless signal from the wireless communication system;

performing a decimation procedure on the received wireless signal to reduce a data rate of the received wireless signal to a sample rate for the PSS;

performing correlation on the decimated wireless signal and each of three time-domain PSS sequences, wherein the three time-domain PSS sequence includes a first, a second and a third PSS sequences generated by the mobile device according to a first, second and third root indexes respectively;

generating a calculation result based on a non-coherent combining operation with the maximum value outputted from a first, a second, and a third correlation results in each sample time of a PSS transmission period;

comparing the calculation result with a predetermined value, for determining whether the PSS is detected;

performing a secondary synchronization signal (SSS) coherent detection procedure, to calculate a SSS sequence according to each of the at least a possible reception time with the three frequency-domain PSS sequences, to obtain a physical layer cell identity group corresponding to the SSS sequence, wherein the SSS coherent detection procedure includes a fast-hardmard transform operation; and

performing a check procedure to determine whether the SSS sequence is detected, wherein the check procedure comprises:

determining that the SSS sequence is detected, and obtaining a corresponding physical layer cell identity group when the fast-hardmard transform operation result is greater than a predetermined value; and

determining that the SSS sequence is not detected when the fast-hardmard transform operation result is smaller than the predetermined value.

8. The method of claim 7 , wherein the step of comparing the calculation result with the predetermined value, for determining whether the PSS is detected, comprises:

determining that the PSS is detected when the calculation result is larger than the predetermined value, and determining the sample time corresponding to the calculation result as a reception time of the PSS; and

determining that the PSS is not detected when the calculation result is smaller than the predetermined value.

9. The method of claim 7 , further comprising:

performing a PSS hypothesis procedure, to generate three frequency-domain PSS sequences according to three root indexes each corresponding to a physical layer identity.

10. The method of claim 9 , wherein the SSS coherent detection procedure includes a PSS channel estimation operation, and a coherent combining operation.

11. The method of claim 7 , further comprising:

calculating a physical-layer cell identity corresponding to a cell based on the obtained physical layer cell identity group and a first, second or a third physical layer identity, in which the first, second and third physical-layer identities respectively correspond to the three frequency-domain PSS sequences for the SSS coherent detection procedure; and

performing a successive interference cancellation (SIC) procedure, for removing interference from a synchronization signal received from the cell, wherein the SIC procedure comprises:

generating a first PSS sequence and a first SSS sequence in the frequency domain based on the physical layer cell identity group and the first, second or third physical layer identity;

performing a channel estimation corresponding to the first SSS sequence; re-generating a second PSS and a second SSS based on the channel estimation result, the first PSS sequence and the first SSS sequence, in which each of the second PSS and the second SSS is a part of the synchronization signal; and

obtaining a third PSS by removing the re-generated second PSS from the PSS, and obtaining a third SSS by removing the re-generated second SSS from the SSS.

12. The method of claim 7 , further comprising:

determining whether the SSS coherent detection procedure are performed on the three frequency-domain PSS sequences with a first reception time of the at least a reception time when the SSS is determined to be not detected;

performing the SSS coherent detection procedure on the three frequency-domain PSS sequences with a second reception time when the SSS coherent detection procedure are performed to all of the three frequency-domain PSS sequences with the first reception time; and

performing the SSS coherent detection procedure on the three frequency-domain PSS sequences with the first reception time when the SSS coherent detection procedure is not performed to all of the three frequency-domain PSS sequences with the first reception time.

13. A method of cell search for a mobile device in a wireless communication system, the method comprising:

performing a reception timing detection procedure, to obtain at least a possible reception time for a primary synchronization signal (PSS);

performing a PSS hypothesis procedure, to generate three frequency-domain PSS sequences according to three root indexes each corresponding to a physical layer identity; and

performing a secondary synchronization signal (SSS) coherent detection procedure, to calculate a SSS sequence according to each of the at least a possible reception time with the three frequency-domain PSS sequences, to obtain a physical layer cell identity group corresponding to the SSS sequence;

wherein the reception timing detection procedure comprises:

receiving a wireless signal from the wireless communication system;

performing a decimation procedure on the received wireless signal to reduce a data rate of the received wireless signal to a sample rate of the PSS;

performing correlation on the decimated wireless signal and three time-domain PSS sequences, wherein the time-domain PSS sequences include a first, a second and a third time-domain PSS sequences generated by the mobile device according to a first, second and third root indexes respectively;

generating a calculation result based on a non-coherent combining operation with the maximum value outputted from a first, a second, and a third correlation results in each sample time of a PSS transmission period; and

comparing the calculation result with a predetermined value, for determining whether the PSS is detected, wherein the step of comparing the calculation result with the predetermined value, for determining whether the PSS is detected, comprises:

determining that the PSS is detected when the calculation result is larger than the predetermined value, and determining the sample time corresponding to the calculation result as a reception time of the PSS; and

determining that the PSS is not detected when the calculation result is smaller than the predetermined value.