ZEROING-OUT LLRS USING DEMOD-BITMAP TO IMPROVE PERFORMANCE OF MODEM DECODER

• US 20090245431A1
• Filed: 03/16/2009
• Published: 10/01/2009
• Est. Priority Date: 03/28/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Challa, Raghu N., Lin, Jeremy H.
• Granted Patent: US 8,437,433 B2
• Time in Patent Office: Days
• US Class Current: 375/340
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A demodulation mask bitmap includes binary mask values. Each mask value corresponds to an input resource element to a demodulator. For each mask value of a first state, a demodulation engine of the demodulator is not clocked and the demodulator outputs a zero-valued resource element. For each mask value of a second state, the demodulation engine is clocked, the input resource element is demodulated, and the demodulator outputs a demodulated resource element. A demodulation mask bitmap is designed to mask pilot resource elements and corrupted resource elements. Power is conserved by not clocking the demodulation engine for corrupted and pilot resource elements. Subsequent LLR generation and decode operations are simplified. Decoder performance is improved because the decoder does not decode LLR values derived from corrupted resource elements and/or resource elements not relevant to the reconstruction of a communicated message.

Claims

1. A method comprising:

(a) receiving a demodulation mask bitmap of mask values;

(b) receiving a resource element; and

(c) demodulating the resource element and outputting a demodulated resource element if a mask value corresponding to the resource element has a first value, whereas if the mask value corresponding to the resource element is a second value then outputting a third value.

2. The method of claim 1, wherein a demodulator performs the demodulating of (c), and wherein the demodulator is not clocked if the mask value corresponding to the resource element is the second value.

3. The method of claim 1, wherein the resource element is one of a plurality of resource elements, and wherein the plurality of resource elements forms a two-dimensional frequency-time matrix.

4. The method of claim 1, wherein the resource element includes a real coefficient and an imaginary coefficient of a complex number.

5. The method of claim 1, further comprising:

(d) generating the demodulation mask bitmap of mask values, wherein a mask value of the demodulation mask bitmap corresponding to a pilot resource element is the second value.

6. The method of claim 1, further comprising:

(d) generating the demodulation mask bitmap of mask values, wherein a mask value of the demodulation mask bitmap corresponding to a corrupted resource element is the second value.

7. The method of claim 1, wherein the receiving of (a) further involves reading a task instruction across a bus, and wherein the task instruction includes the demodulation mask bitmap.

8. The method of claim 6, wherein a Tightly Coupled Memory (TCM) system performs the generating of (d).

9. The method of claim 1, wherein the third value is a zero-valued triplet.

10. A demodulator comprising:

a plurality of sequential storage elements storing a demodulation mask bitmap of mask values; and

a demodulation engine that selectively outputs a demodulated resource element if a mask value corresponding to a resource element is a first value, whereas if the mask value corresponding to the resource element is a second value then the demodulation engine outputs a third value.

11. The demodulator of claim 10, further comprising:

a task manager, wherein the task manager reads a task instruction over a bus and stores the demodulation mask bitmap into the plurality of sequential storage elements; and

an IQ fetcher that reads the resource element from a buffer.

12. The demodulator of claim 11, wherein the demodulation engine is not clocked if the mask value corresponding to the resource element is the second value.

13. An apparatus, comprising:

means for outputting a demodulated resource element if a mask value corresponding to a resource element is a first value, whereas if the mask value corresponding to the resource element is a second value then outputting a third value; and

a plurality of sequential storage elements that store a demodulation mask bitmap of mask values.

14. The apparatus of claim 13, wherein the means is also for demodulating a resource element to generate the demodulated resource element.

15. The apparatus of claim 13, wherein the means is also for generating a Log-Likelihood Ratio (LLR) if the mask value corresponding to the resource element is the first value, whereas if the mask value corresponding to the resource element is the second value then generating a zero-valued LLR.

16. The apparatus of claim 13, wherein the means and the plurality of sequential storage elements are parts of a radio receiver.

17. A computer program product, comprising:

computer-readable medium comprising;

code for causing a computer to demodulate a resource element and output a demodulated resource element if a mask value corresponding to the resource element has a first value, whereas if the mask value corresponding to the resource element is a second value then outputting a third value.

18. The computer program product of claim 17, wherein the computer includes a processor, a memory, and a demodulator operatively coupled to the processor, and wherein the memory is the computer-readable medium and stores the code.

19. The computer program product of claim 17, wherein the computer-readable medium further comprises:

code for causing the computer to output the third value when the resource element is a corrupted resource element, wherein the corrupted resource element is a resource element containing corrupted data.

20. The computer program product of claim 18, wherein the mask value is one mask value of a two-dimensional demodulation mask bitmap array of mask values.

21. The computer program product of claim 17, wherein the computer-readable medium further comprises:

code for causing the computer to update a demodulation mask bitmap of mask values.

22. A method comprising:

(a) receiving a demodulation mask of mask values;

(b) receiving a resource element; and

(c) controlling how a demodulation engine demodulates the resource element depending on a multi-bit mask value corresponding to the resource element.

23. The method of claim 22, wherein the demodulation engine comprises a first demodulator and a second demodulator, wherein the first demodulator performs the demodulating of (c), and wherein the first demodulator is not clocked if the multi-bit mask value has a predetermined value.

24. The method of claim 22, wherein the resource element is one of a plurality of resource elements, and wherein the plurality of resource elements forms a three-dimensional time-frequency-space grid.

25. The method of claim 22, wherein the demodulation mask of mask values is a three-dimensional grid of multi-bit mask values.