Zeroing-out LLRs using demod-bitmap to improve performance of modem decoder

• US 8,437,433 B2
• Filed: 03/16/2009
• Issued: 05/07/2013
• Est. Priority Date: 03/28/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Challa, Raghu N., Lin, Jeremy H.
• Primary Examiner(s): Ometz, David
• Assistant Examiner(s): Garcia, Santiago
• Application Number:
  US12/404,636
• Publication Number:
  US 20090245431A1
• Time in Patent Office: 1,513 Days
• Field of Search: 375/340
• 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) selectivey demodulating the resource element and outputting a demodulated resource element,

wherein the resource element is demodulated and output as a demodulated resource element if a mask value in the demodulation mask bitmap corresponding to the resource element having a first state, and

wherein the resource element is not demodulated, and not clocked, and is output from a demodulator as a predetermined value if the mask value corresponding to the resource element comprises a second state, wherein if the resource element is a pilot resource element, a mask value of the demodulation mask bitmap comprises the second state.

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 state.

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 if the resource element is a corrupted resource element, a mask value of the demodulation mask bitmap corresponding to the corrupted resource element has the second state.

6. 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.

7. The method of claim 5, wherein a Tightly Coupled Memory (TCM) system performs the generating of (d).

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

24. The method of claim 1, wherein the mask values of the demodulation mask bitmap comprise binary values.

25. The method of claim 1, further comprising:

receiving a signal;

generating the resource grid based on the signal; and

generating the demodulation mask bitmap of mask values based on the signal.

26. The method of claim 1, wherein the demodulation mask bitmap forms a two-dimensional array, and wherein each mask value of the demodulation mask bitmap corresponds to a respective resource element of in a resource grid.

9. A demodulator comprising:

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

a demodulation engine that selectively demodulates a resource element and outputs a demodulate resource element,

wherein the demodulation engine demodulates the resource element and outputs the demodulated resource element if a mask value corresponding to the resource element is a first state, and

wherein the demodulation engine does not demodulate the resource element and does not clock and outputs the resource element as a predetermined value if the mask value corresponding to the resource element is a second state and wherein if the resource element is a pilot resource element, a mask value of the demodulation mask bitmap comprises the second state.

10. The demodulator of claim 9, 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.

11. The demodulator of claim 10, wherein the demodulation engine is not clocked if the mask value corresponding to the resource element is the second state.

12. An apparatus, comprising:

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

means for selectively demodulating a resource element and outputting a demodulated resource element wherein the resource element is demodulated and

output as the demodulated resource element if a mask value in the demodulation mask bitmap corresponding to the resource element is a first state, and

wherein the resource element is not demodulated and not clocked, and is output as a predetermined value if the mask value corresponding to the resource element is a second state and wherein if the resource element is a pilot resource element, a mask value of the demodulation mask bitmap comprises the second state.

13. The apparatus of claim 12, further comprising:

means for generating a Log-Likelihood Ratio (LLR) if the mask value corresponding to the resource element is the first state, whereas if the mask value corresponding to the resource element is the second state then generating a zero-valued LLR.

14. The apparatus of claim 12, wherein the means for selectively demodulating and the plurality of sequential storage elements are parts of a radio receiver.

15. A non-transitory computer program product, comprising:

a non-transitory computer-readable storage medium comprising;

code for causing a computer to selectively demodulate a resource element and output a demodulated resource element, wherein the resource element is demodulated and output as a demodulated resource element if a mask value in a demodulation mask bitmap corresponding to the resource element has a first state, and wherein the resource element is not demodulated and not clocked and is output from a demodulator as a predetermined value if the mask value corresponding to the resource element is a second state and wherein if the resource element is a pilot resource element, a mask value of the demodulation mask bitmap comprises the second state.

16. The computer program product of claim 15, wherein the computer includes a processor, a memory, and a demodulator operatively coupled to the processor, and wherein the memory is the computer-readable storage medium and stores the code.

17. The computer program product of claim 15, wherein the computer-readable storage medium further comprises:

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

18. The computer program product of claim 16, wherein the mask value is one mask value in the demodulation mask bitmap, wherein the demodulation mask bitmap is a two-dimensional array of mask values.

19. The computer program product of claim 15, wherein the computer-readable medium further comprises:

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

20. A method comprising:

(a) receiving a demodulation mask of mask values;

(b) receiving a resource element; and

(c) controlling a demodulation engine to selectively demodulate and output the resource element depending on a multi-bit mask value of the demodulation mask corresponding to the resource element and wherein the resource element is demodulated and output as a demodulated resource element if a mask value in the demodulation mask bitmap corresponding to the resource element having a first state, and

wherein the resource element is not demodulated, and not clocked, and is output from a demodulator as a predetermined value if the mask value corresponding to the resource element comprises a second state, wherein if the resource element is a pilot resource element, a mask value of the demodulation mask bitmap comprises the second state.

21. The method of claim 20, 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.

22. The method of claim 20, wherein the resource element is one of a plurality of resource elements in a resource grid, and wherein the resource grid is a three-dimensional time-frequency-space grid.

23. The method of claim 20, wherein the demodulation mask of mask values is a three-dimensional grid of multi-bit mask values.