Multi-carrier transmitter for ultra-wideband (UWB) systems

• US 20040008617A1
• Filed: 01/02/2003
• Published: 01/15/2004
• Est. Priority Date: 07/12/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Batra, Anuj, Dabak, Anand G.
• Granted Patent: US 7,609,612 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0062 Avoidance of ingress interference, e.g. ham radio channels

Abstract

System and method for a multi-carrier ultra-wideband (UWB) transmitter. A preferred embodiment comprises an UWB transmitter (for example, transmitter 300) taking advantage of both code division multiple access (CDMA) (for example, block 305) and orthogonal frequency division multiplexing (OFDM) (for example, block 315) techniques to create a multi-carrier UWB transmitter. The multi-carrier UWB is capable of avoiding interferers by eliminating signal transmissions in the frequency bands occupied by the interferers. An alternate embodiment using intermediate frequencies and mixers is also presented.

Claims

1. A method for providing ultra-wideband wireless communications comprising:

arranging a data stream into a plurality of sub-frequency ranges, wherein the sub-frequency ranges are portions of a total available transmission bandwidth;

transforming the arranged data into a time domain signal;

converting the time domain signal into an analog signal; and

transmitting the analog signal.

2. The method of claim 1 further comprising multiplying a data stream with an orthogonal spreading code prior to arranging.

3. The method of claim 2 further comprising interleaving the multiplied data stream, wherein an interleaving factor is equal to a spreading gain of the orthogonal spreading code.

4. The method of claim 2, wherein the multiplying comprises:

selecting I data bits from the data stream, where I is a number that is specified and is dependent upon an inverse Discrete Fourier transform;

multiplying the I data bits with J orthogonal spreading codes, where J is the spreading gain; and

producing a total of I*J chips.

5. The method of claim 1 further comprising adjusting a signal magnitude for each of the plurality of sub-frequency ranges to compensate for a transmit antenna'"'"'s frequency selectivity with a gain that may be different for each sub-frequency range.

6. The method of claim 1 further comprising inserting special values into certain sub-frequency ranges of the plurality of sub-frequency ranges to ensure that the wireless communications adhere to spectral constraints.

7. The method of claim 6, wherein the special values are equal to zero.

8. The method of claim 1, wherein the arranging comprises:

partitioning the data stream into I portions, where I is a number of data bits taken from the data stream and multiplied with the orthogonal spreading code;

placing the I partitions into I sub-frequency ranges out of a total of I+N sub-frequency ranges, where N is a number of zero pad sub-frequency ranges; and

putting a special value into the N remaining sub-frequency ranges.

9. The method of claim 1, wherein the transforming is an inverse Discrete Fourier transform implemented as an inverse Fast Fourier transform (iFFT), and wherein the iFFT has a length that is a power of two.

10. The method of claim 1 further comprising appending a cyclic preamble to the computed data prior to converting.

11. The method of claim 10, wherein the appending comprises:

duplicating a result of the transforming;

concatenating the result of the transforming with the duplicated result; and

replicating the concatenated result a number of times.

12. The method of claim 1 further comprising filtering the analog signal to ensure that the analog signal complies with spectral restrictions.

13. The method of claim 1 further comprising mixing the analog signal up to a desired transmission frequency prior to transmitting.

14. The method of claim 1 further comprising appending a cyclic preamble to the transformed data.

15. The method of claim 1, wherein the data stream is partitioned into a plurality of independent partitions, and wherein each partition undergoes converting and transmitting independently of each other.

16. The method of claim 1, wherein the data stream is partitioned into a plurality of independent partitions, and wherein each partition undergoes arranging, transforming, converting, and transmitting independently of each other.

17. An ultra-wideband transmitter comprising:

a data input;

a data partitioner coupled to the data input, the data partitioner containing circuitry to partition a data stream provided by the data input into a plurality of units and to place the units into individual sub-frequency ranges;

a digital-to-analog converter (DAC) coupled to the data partitioner, the DAC containing circuitry to convert a digital data stream into an analog signal stream; and

an antenna coupled to the DAC, the antenna used to transmit the analog signal stream.

18. The ultra-wideband transmitter of claim 17 further comprising a data spreader having an input coupled to the data input and an output coupled to the data partitioner, the data spreader containing circuitry to multiply the data stream with an orthogonal spreading code.

19. The ultra-wideband transmitter of claim 18, wherein there is a plurality of ultra-wideband transmitters operating within a local area, and wherein the data spreader in each of the ultra-wideband transmitters uses a different orthogonal spreading code.

20. The ultra-wideband transmitter of claim 18 further comprising an interleaver having an input coupled to the data spreader and an output coupled to the data partitioner, the interleaver containing circuitry to collect every data unit from the output of the data spreader and place it into one of J storage locations, wherein J is an order of the interleaver.

21. The ultra-wideband transmitter of claim 20, wherein a data unit, n, is placed into storage location n modulo J.

22. The ultra-wideband transmitter of claim 17, wherein the data partitioner further comprises:

a compensator having an input coupled to the data spreader, the compensator containing circuitry to adjust a signal gain in each of the individual sub-frequency ranges;

a zero pad unit having an input coupled to an output of the compensator, the zero pad unit containing circuitry to append zero valued sub-frequency ranges to the output of the compensator; and

an inverse Discrete Fourier transform unit having an input coupled to an output of the zero pad unit, the inverse Fourier transform unit containing circuitry to convert the output of the zero pad unit into a time domain representation.

23. The ultra-wideband transmitter of claim 22, wherein the inverse Discrete Fourier transform unit implements an inverse Fast Fourier Transform (iFFT) algorithm with a length equal to a power of two.

24. The ultra-wideband transmitter of claim 23, wherein the zero pad unit appends a sufficient number of zero valued sub-frequency ranges to make the sum of the individual sub-frequency ranges and the zero valued sub-frequency ranges equal to the length of the iFFT.

25. The ultra-wideband transmitter of claim 22, wherein the data partitioner further comprises a cyclic prefix unit having an input coupled to an output of the inverse Fourier transform unit, the cyclic prefix unit containing circuitry to duplicate the output of the inverse Fourier transform unit, append the output of the inverse Fourier transform unit with the duplicate, and replicate copies of the appended output.

26. The ultra-wideband transmitter of claim 17 further comprising a mixer unit having an input coupled to an output of the DAC, the mixer unit containing circuitry to modulate the analog signal stream to a desired carrier frequency.

27. The ultra-wideband transmitter of claim 17 further comprising a filter having an input coupled to the DAC and an output coupled to the antenna, the filter to ensure that the analog signal stream meets spectral restrictions.

28. The ultra-wideband transmitter of claim 17, wherein there are a plurality of DACs coupled to the data partitioner, wherein each DAC is further coupled to a mixer unit, wherein each DAC contains circuitry to convert a portion of the digital data stream into a portion of the analog signal stream, and wherein each mixer unit contains circuitry to modulate the portion of the analog signal stream to a different desired carrier frequency.

29. The ultra-wideband transmitter of claim 28, wherein the plurality of individual analog signal streams can be combined to recreate the analog signal stream.

30. The ultra-wideband transmitter of claim 28, wherein each mixer unit has an output coupled to a filter, the filter to ensure that the portion of the analog signal stream meets spectral restrictions.

31. The ultra-wideband transmitter of claim 30, wherein each filter has an output coupled to an individual antenna.

32. The ultra-wideband transmitter of claim 17, wherein there are a plurality of data partitioners coupled to the data input, wherein there is a DAC coupled to each data partitioner, wherein the data stream is partitioned into a plurality of independent partitions, and wherein each independent partition is provided to a different partitioner and DAC.

33. The ultra-wideband transmitter of claim 32, wherein each DAC is coupled to the antenna.

34. A method for avoiding interferers comprising:

scanning a transmit band for interferers;

determining the presence of interferers;

zeroing out data in a signal in a frequency band containing the interferers; and

transmitting the signal.

35. The method of claim 34, wherein the scanning comprises detecting received signal strength at every frequency within a transmit frequency band.

36. The method of claim 35, wherein the scanning further comprises stopping a current transmission.

37. The method of claim 34, wherein the determining comprises a detection of a received signal with a signal strength greater than a predetermined threshold.

38. The method of claim 34, wherein the zeroing comprises replacing an existing signal value with a zero value when the existing signal is to be transmitted at a frequency containing an interferer.

39. The method of claim 34, wherein the method is performed at periodic times during system operation.

40. The method of claim 34, wherein the method is performed when system performance degrades below a prespecified threshold, and wherein system performance is measured using a cyclic redundancy code.

41. The method of claim 34, wherein the method is performed when system performance degrades below a prespecified threshold, and wherein system performance is measured using a bit error rate (BER).

42. The method of claim 34, wherein the method is performed when system performance degrades below a prespecified threshold, and wherein system performance is measured using a packet error rate (PER).