Apparatus and Method for Performing a Scan Procedure and Mobile Station Comprising the Same

• US 20090092041A1
• Filed: 08/08/2008
• Published: 04/09/2009
• Est. Priority Date: 10/04/2007
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Juang, Den-Kai
• Granted Patent: US 8,279,746 B2
• Time in Patent Office: Days
• US Class Current: 370/210
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

An apparatus for performing a scan procedure according to an orthogonal frequency division multiple access (OFDMA) signal and a mobile station comprising the same are provided. The characteristic of the apparatus is that it comprises two FIT input buffers. In a first period of a downlink subframe, the first FFT input buffer is used for data transmission. In a second period of the downlink subframe, the second FFT input buffer is used for storing more than one OFDMA sample in advance for further processing. In a third period of an uplink subframe, the stored OFDMA samples can be used to generate a refined frame boundary and calculates a CINR value of each of a plurality of neighboring base stations. Therefore, the apparatus and the MS can perform the scan procedure without downgrading the network efficiency.

Claims

1. An apparatus for performing a scan procedure according to an orthogonal frequency division multiple access (OFDMA) signal, comprising:

a first fast Fourier transform (FFT) input buffer for contiguously gathering a first predetermined number of OFDMA samples related to the OFDMA signal during a first period corresponding to a downlink subframe;

a second FFT input buffer for gathering a second predetermined number of OFDMA samples related to the OFDMA signal during a second period corresponding to the downlink subframe;

an FFT core module for contiguously applying FFT to the first predetermined number of OFDMA samples during the first period and for applying FFT to the second predetermined number of OFDMA samples during a third period corresponding to an uplink subframe, the uplink subframe occurring later than the downlink subframe;

a post-FFT processing module for measuring a frame boundary of a serving base station (SBS) of the apparatus during the first period and for measuring a refined frame boundary of at least one neighboring base station (NBS) of the apparatus according to the second predetermined number of OFDMA samples and the frame boundary during the third period; and

a channel interference and noise ratio (CINR) measurement module for calculating a CINR value of the at least one NBS based on the refined frame boundary.

2. The apparatus of claim 1, wherein the OFDMA signal comprises a sub-signal from the SBS and each of the at least one NBS.

3. The apparatus of claim 2, wherein the sub-signal from the SBS comprises an identity of the at least one NBSs, the post-FFT processing module measures the refined frame boundary of the at least one NBSs according to the corresponding identity, and the CINR measurement module calculates the CINR value of the at least one NBSs according to the corresponding identity.

4. The apparatus of claim 1, wherein the first predetermined number of OFDMA samples comprises a preamble of the OFDMA signal in the first input buffer, the preamble in the first input buffer is overwritten after the preamble in the first input buffer is forwarded to the FFT core module.

5. The apparatus of claim 1, wherein the second predetermined number is greater than the first predetermined number.

6. The apparatus of claim 1, further comprising:

a receiving filter for filtering the OFDMA signal; and

a pre-FFT processing module for processing the OFDMA signal before the first predetermined number of OFDMA samples are gathered and the second predetermined number of OFDMA samples are gathered.

7. The apparatus of claim 3, wherein the apparatus, the SBS, and the NBSs conform to the Worldwide Interoperability for Microwave Access (WiMAX) standard and the identities are CELL_IDs defined in the WiMAX standard.

8. A mobile station (MS), comprising:

an antenna for receiving an OFDM signal; and

a processing module for performing a scan procedure according to the OFDMA signal, comprising;

a first FFT input buffer for contiguously gathering a first predetermined number of OFDMA samples related to the OFDMA signal during a first period corresponding to a downlink subframe;

a second FFT input buffer for gathering a second predetermined number of OFDMA samples related to the OFDMA signal during a second period corresponding to the downlink subframe;

an FFT core module for contiguously applying FFT to the first predetermined number of OFDMA samples during the first period and for applying FFT to the second predetermined number of OFDMA samples during a third period corresponding to an uplink subframe, the uplink subframe occurring later than the downlink subframe;

a post-FFT processing module for measuring a frame boundary of an SBS of the MS during the first period and for measuring a refined frame boundary of at least one NBS of the MS according to the second predetermined number of OFDMA samples and the frame boundary during the third period; and

a CINR measurement module for calculating a CINR value of the at least one NBS based on the refined frame boundary.

9. The MS of claim 8, wherein the OFDMA signal comprises a sub-signal from the SBS and the at least one NBSs.

10. The MS of claim 9, wherein the sub-signal from the SBS comprises an identity of the at least one NBSs, the post-FFT processing module measures the refined frame boundary of the at least one NBSs according to the corresponding identity, and the CINR measurement module calculates the CINR value of the at least one NBSs according to the corresponding identity.

11. The MS of claim 8, wherein the first predetermined number of OFDMA samples comprise a preamble of the OFDMA signal in the first input buffer, the preamble in the first input buffer is overwritten after the preamble in the first input buffer is forwarded to the FFT core module.

12. The MS of claim 8, wherein the second predetermined number is greater than the first predetermined number.

13. The MS of claim 8, wherein the processing module further comprises:

a receiving filter for filtering the OFDMA signal; and

a pre-FFT processing module for processing the OFDMA signal before the first predetermined number of OFDMA samples are gathered and the second predetermined number of OFDMA samples are gathered.

14. The MS of claim 9, wherein the MS, the SBS, and the NBSs conform to the WiMAX standard and the identities are CELL_IDs defined in the WiMAX standard.

15. A method for performing a scan procedure according to an OFDMA signal, comprising the steps of:

gathering a first predetermined number of OFDMA samples related to the OFDMA signal contiguously during a first period corresponding to a downlink subframe;

gathering a second predetermined number of OFDMA samples related to the OFDMA signal during a second period corresponding to the downlink subframe;

applying FFT to the first predetermined number of OFDMA samples contiguously during the first period;

applying FFT to the second predetermined number of OFDMA samples during a third period corresponding to an uplink subframe occurring later than the downlink subframe;

measuring a frame boundary of an SBS during the first period;

measuring a refined frame boundary of at least one NBS according to the second predetermined number of OFDMA samples and the frame boundary during the third period; and

calculating a CINR value of the at least one NBS based on the refined frame boundary.

16. The method of claim 15, wherein the first predetermined number of OFDMA samples comprise a preamble of the OFDMA signal in the first input buffer, the preamble in the first input buffer is overwritten after the preamble in the first input buffer is forwarded to process FFT.

17. The method of claim 15, wherein the second predetermined number is greater than the first predetermined number.