OFDM RECEIVER HAVING MEMORY CAPABLE OF ACTING IN A SINGLE-CHIP MODE AND A DIVERSITY MODE

• US 20090316820A1
• Filed: 06/23/2008
• Published: 12/24/2009
• Est. Priority Date: 06/23/2008
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Yang, Shun-An
• Granted Patent: US 8,059,737 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/0837 using pre-detection combining H04B7/0868 takes precedence
• CPC Class Codes: H04B 7/0877 switching off a diversity branch, e.g. to save power
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

An OFDM receiver is provided. The OFDM receiver comprises a Fourier transform (FFT) module, a storage device, an equalizer, and a diversity combiner module. The Fourier transform module transforms a time-domain symbol into an OFDM symbol. The storage device stores OFDM symbols. When operated in a single chip mode, the storage device stores more OFDM symbols outputted from FFT module than operated in a diversity mode. The equalizer retrieves the OFDM symbols from the storage device or the FFT module, estimates the channel frequency response of a transmission channel, and equalizes the OFDM symbol according to the channel frequency response. When operated in the diversity mode, the diversity combiner module receives the OFDM symbols and an alignment signal from a diversity OFDM receiver.

Claims

1. An OFDM receiver for receiving signals transmitted at radio frequency and having a storage device to be shared by an equalizer and a diversity combiner module, comprising:

a (FFT) receiving a time-domain symbol and transforming the time-domain symbol into an OFDM symbol;

the storage device, capable of operating in a diversity mode or a single chip mode, storing a first set of OFDM symbols when operated in the single chip mode, and storing a second set of OFDM symbols when operated in the diversity mode;

the equalizer, coupled to the storage device, for retrieving and equalizing the OFDM symbols from at least one of the storage device and the FFT module; and

the diversity combiner module, coupled to the storage device, for receiving an alignment signal and data symbols from a diversity OFDM receiver.

wherein the first set of OFDM symbols is different from the second set of OFDM symbols and the first set of OFDM symbols comprises more the OFDM symbols outputted from the FFT module than the second set of OFDM symbols,

whereby the storage device is capable of storing more OFDM symbols outputted from the FFT module to generate a better estimation result from the equalizer in the single chip mode and the storage device is capable of storing less OFDM symbols outputted from the FFT module for having a extra space to store the OFDM symbols received from the diversity OFDM receiver in the diversity mode.

2. The OFDM receiver as claimed in claim 1, wherein the alignment signal includes information for combining the OFDM symbols outputted from the FFT module and the data symbols received from the diversity OFDM receiver.

3. The OFDM receiver as claimed in claim 1, wherein the size of the first set of the OFDM symbols and the size of the second set of the OFDM symbols are dynamically adjusted.

4. The OFDM receiver as claimed in claim 1, wherein the size of the first set of the OFDM symbols and the size of the second set of the OFDM symbols are dynamically adjusted according to an amount of OFDM symbols as equalizer required.

5. The OFDM receiver as claimed in claim 1, further comprising a synchronizing and guard-interval-removing module, wherein the synchronization and guard-interval-removing module receives a transmitted signal, synchronizes the signal and removes the guard-interval of the synchronized signal to form the time-domain symbol.

6. The OFDM receiver as claimed in claim 1, wherein the equalizer comprises an estimation module for estimating a channel frequency response of a transmission channel according to pilot sub-carriers in the OFDM symbols outputted from the FFT module.

7. The OFDM receiver as claimed in claim 6, wherein the estimation module further comprises:

a time direction interpolation block for interpolating pilot sub-carriers of OFDM symbols to form a plurality of pseudo pilot sub-carriers; and

a frequency direction interpolation block receiving the plurality of pseudo pilot sub-carriers and interpolating all the sub-carriers of an OFDM symbol according to the pseudo pilot sub-carriers and the pilot sub-carriers.

8. The OFDM receiver as claimed in claim 1 further comprises a de-mapping module and an error control code decoder.

9. The OFDM receiver as claimed in claim 8, wherein the OFDM symbols outputted from the FFT module are further de-mapped or de-interleaved in the de-mapping module and sent the de-mapped or de-interleaved output to the diversity combiner module for combining with the data symbols from the diversity OFDM receiver.

10. The OFDM receiver as claimed in claim 9, wherein the data symbols from the diversity OFDM receiver are de-mapped or de-interleaved.

11. An OFDM receiver for receiving signals transmitted at radio frequency, comprising:

a Fourier transform (FFT) module receiving a time-domain symbol and transforming the time-domain symbol into an OFDM symbol 1;

a storage device, capable of operating in a non-MPEFEC mode or a MPEFEC mode, storing a first set of OFDM symbols when operated in the non-MPEFEC mode, and storing a second set of OFDM symbols when operated in the MPEFEC mode;

an equalizer for retrieving OFDM symbols from the storage device or the FFT module, estimating the channel frequency response of a transmission channel according to pilot sub-carriers in the OFDM symbols, and equalizing the OFDM symbols according to the channel frequency response;

an error control code decoder decoding the equalized OFDM symbols to generate transport streams; and

an MPEFEC module operating in either the MPEFEC mode or the non-MPEFEC mode, when operated in the MPEFEC mode, the MPEFEC module forwards the MPEFEC information and the OFDM symbols from the storage device.

12. The OFDM receiver as claimed in claim 11, wherein the MPE-FEC module comprises a (Forward Error Correction) FEC decoder.

13. The OFDM receiver as claimed in claim 11, further comprising a synchronizing and guard-interval-removing module, wherein the synchronization and guard-interval-removing module receives a transmitted signal, synchronizes the signal and removes the guard-interval of the synchronized signal to form the time-domain symbol.

14. The OFDM receiver as claimed in claim 11 further comprises a de-mapping module and an error control code decoder.

15. A method for receiving signals transmitted at radio frequency and having a storage device to be shared by an equalizer and a diversity combiner module, comprising:

providing a Fourier transformer (FFT) module for receiving a time-domain symbol and transforming the time-domain symbol into an OFDM symbol;

storing a first set of OFDM symbols in the storage device when operated in the single chip mode, and storing a second set of OFDM symbols when operated in the diversity mode;

retrieving and equalizing the OFDM symbols, wherein the OFDM symbols are retrieved from the storage device or directly from the FFT module; and

receiving an alignment signal and data symbols from a diversity OFDM receiver;

wherein the first set of OFDM symbols is different from the second set of OFDM symbols and the first set of OFDM symbols comprises more the OFDM symbols outputted from the FFT module than the second set of OFDM symbols,

whereby more OFDM symbols outputted from the FFT module are stored to generate a better estimation result while the storage device acts under the single chip mode and less OFDM symbols outputted from the FFT module are stored so that there are extra spaces in the storage device to store the OFDM symbols received from the diversity OFDM receiver while the storage device acts under the diversity mode.

16. The method as claimed in claim 15, wherein the alignment signal includes information for combining the OFDM symbols outputted from the FFT module and the data symbols from the diversity OFDM receiver.

17. The OFDM receiver as claimed in claim 15, wherein the size of the first set of the OFDM symbols and the size of the second set of the OFDM symbols are dynamically adjusted.

18. The OFDM receiver as claimed in claim 15, wherein the size of the first set of the OFDM symbols and the size of the second set of the OFDM symbols are dynamically adjusted according to an amount of OFDM symbols for performing the equalizing step.

19. The OFDM receiver as claimed in claim 15, the OFDM symbols outputted from the FFT module are further de-mapped or de-interleaved prior and the de-mapped or de-interleaved output are combined with the data symbols from the diversity OFDM receiver.