Wireless device and method for low power and low data rate operation

• US 9,537,699 B2
• Filed: 05/22/2015
• Issued: 01/03/2017
• Est. Priority Date: 11/21/2011
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Kenney, Thomas J., Perahia, Eldad
• Primary Examiner(s): Ho, Duc C
• Application Number:
  US14/719,733
• Publication Number:
  US 20150365265A1
• Time in Patent Office: 592 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H04L 27/2628 Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators H04L27/2634 takes precedence
• CPC Class Codes: H04L 27/2643 using symbol repetition, e.g. time domain realization of distributed FDMA
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 69/22 Parsing or analysis of headers
• CPC Class Codes: H04W 52/267 taking into account the information rate
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

Embodiments of a wireless device and method for transmitting a packet comprising one or more orthogonal frequency division multiplexed (OFDM) transmission symbols are generally described herein. In some embodiments, the wireless device may be configured to map data to active tones and map zeroes to nulled tones of a set of OFDM tones to generate an OFDM symbol comprising both the active and the nulled tones. The number of active and nulled tones may be based on a nulling factor. The OFDM symbol may be down-clocked to generate an OFDM transmission symbol for transmission over a reduced transmission bandwidth. Accordingly, low power may be used for very low data rate transmissions, which may be suitable for sensor devices.

Claims

1. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of a wireless device to configure the wireless device for transmission of a packet comprising one or more orthogonal frequency division multiplexed (OFDM) transmission symbols, the instructions to configure the wireless device to:

map data to active tones and map zeroes to nulled tones of a set of OFDM tones to generate an OFDM symbol comprising both the active and the nulled tones, the number of active and nulled tones being based on a nulling factor; and

generate a packet comprising one or more OFDM transmission symbol from the generated OFDM symbol for transmission over a transmission bandwidth.

2. The non-transitory computer-readable storage medium of claim 1, wherein the set of OFDM tones of the OFDM symbol comprises a predetermined number of tones;

and

wherein the number of active tones of the set and the number of nulled tones of the set is determined based on the nulling factor; and

wherein the OFDM symbol is generated by performing an inverse Fourier transform on both active and the nulled tones.

3. The non-transitory computer-readable storage medium of claim 2, wherein the nulling factor indicates a portion of tones of the set of tones that are active;

and

wherein the OFDM transmission symbol further includes pilot tones, guard tones and a cyclic prefix.

4. The non-transitory computer-readable storage medium of claim 3, wherein the packet comprises a physical layer service data unit (PSDU), the PSDU comprising a plurality of OFDM transmission symbols,

wherein the data that is mapped to the active tones is received as part of a media-access control (MAC) layer protocol data unit (MPDU);

and

wherein the instructions further configure the one or more processors to calculate a PSDU length based at least on the nulling factor, a size of the MPDU, and a number of OFDM symbols to be transmitted as part of the PSDU.

5. The non-transitory computer-readable storage medium of claim 4, wherein the instructions further configure the one or more processors to:

calculate a number of padding bits based on a length of the PSDU; and

add the calculated number of padding bits to generate the PSDU,

wherein the data bits and the padding bits of the PSDU are mapped to the active tones and are not mapped to the nulled tones.

6. The non-transitory computer-readable storage medium of claim 5, wherein the instructions further configure the one or more processors to include the nulling factor in a signaling field of a header portion of the PSDU for use by a receiver in decoding the PSDU.

7. The non-transitory computer-readable storage medium of claim 5, wherein the instructions further configure the one or more processors to:

receive a configuration signal from an access point indicating the nulling factor; and

determine the number of active tones and the number of nulled tones based on the nulling factor.

8. The non-transitory computer-readable storage medium of claim 5, wherein the instructions further configure the one or more processors to:

multiplex the data that is to be mapped to the active tones with the zeroes that are to be mapped to the nulled tones; and

perform an inverse-discrete Fourier transform (IDFT) on the multiplexed data to generate a time-domain signal corresponding to the OFDM symbol having the data on the active tones and zeroes on the nulled tones.

9. The non-transitory computer-readable storage medium of claim 8, wherein to generate the OFDM transmission symbol, the wireless device is configured to down-clock the OFDM symbol to generate the OFDM transmission symbol for transmission over a reduced transmission bandwidth.

10. The non-transitory computer-readable storage medium of claim 9, wherein the time-domain signal has a transmission bandwidth based on a sample clock rate,

wherein the instructions further configure the one or more processors to:

perform the IDFT based on the sample clock rate; and

perform a digital-to-analog conversion on the time-domain signal based on the sample clock rate to generate the OFDM transmission symbol having the transmission bandwidth,

wherein the sample clock rate is a down-clocked sample clock rate configured to reduce the transmission signal bandwidth by a factor of ten or more.

11. The non-transitory computer-readable storage medium of claim 10, wherein the instructions further configure the one or more processors to configured the wireless device to:

upconvert the time domain signals to a transmission frequency of between 800 MHz and 1.0 GHz; and

amplify the signals at the transmission frequency with a power amplifier,

wherein the time-domain signals for transmission generated by the IDFT comprise a plurality of tones that are evenly spaced across the transmission bandwidth, the plurality of tones comprising the active and the nulled tones.

12. The non-transitory computer-readable storage medium of claim 11, wherein the active tones are substantially evenly spaced across the transmission bandwidth allowing for a reduction in a peak-to-average power ratio (PAPR) of the signals for transmission.

13. The non-transitory computer-readable storage medium of claim 11, wherein when the sample clock rate is down-clocked by one-tenth, the transmission bandwidth comprises bandwidths of 2 MHz, 4 MHz, 8 MHz or 16 MHz using sets of 52, 108, 234 and 468 tones, respectively.

14. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of a wireless device to configure the wireless device for transmission of one or more orthogonal frequency division multiplexed (OFDM) transmission symbols, the operations to configure the wireless device to:

map data to active tones and map zeroes to nulled tones of a set of OFDM tones to generate an OFDM symbol comprising both the active and the nulled tones, the number of active and nulled tones being based on a nulling factor; and

down-clock the OFDM symbol to generate an OFDM transmission symbol for transmission over a reduced transmission bandwidth.

15. The non-transitory computer-readable storage medium of claim 14, wherein the instructions further configure the wireless device to:

multiplex data that is to be mapped to the active tones with the zeroes that are to be mapped to the nulled tones; and

perform an inverse-discrete Fourier transform (IDFT) on the multiplexed data to generate a time-domain signal corresponding to the OFDM symbol having the data on the active tones and zeroes on the nulled tones.

16. The non-transitory computer-readable storage medium of claim 15, wherein the set of OFDM tones of the OFDM symbol comprises a predetermined number of tones,

wherein the number of active tones of the set and the number of nulled tones of the set is determined based on the nulling factor;

and

wherein the OFDM symbol is generated by performing an inverse Fourier transform on both the active and the nulled tones.

17. The non-transitory computer-readable storage medium of claim 16, wherein the OFDM symbol is part of a physical layer service data unit (PSDU), the PSDU comprising a plurality of OFDM transmission symbols,

wherein the data that is mapped to the active tones is received as part of a MAC layer protocol data unit (MPDU);

and

wherein the instructions further configure the one or more processors to calculate a PSDU length based at least on the nulling factor, a size of the MPDU, and a number of OFDM symbols to be transmitted as part of the PSDU.

18. The non-transitory computer-readable storage medium of claim 17, wherein the instructions further configure the one or more processors to:

calculate a number of padding bits based on a length of the PSDU; and

add the calculated number of padding bits to generate the PSDU,

wherein data bits and the padding bits are mapped to the active tones and are not mapped to the nulled tones.

19. The non-transitory computer-readable storage medium of claim 18, wherein the instructions further configure the one or more processors to include the nulling factor in a signaling field of a header portion of the PSDU for use by a receiver in decoding the PSDU.

20. The non-transitory computer-readable storage medium of claim 14, wherein the wireless device is a sensor device configured to operate on battery power and configured to transmit sensor data comprising one or more OFDM transmission symbols, the sensor device configured to:

map data to active tones and map zeroes to nulled tones of a set of OFDM tones to generate an OFDM symbol comprising both the active and the nulled tones, the number of active and nulled tones being based on a nulling factor; and

down-clock the OFDM symbol to generate a multicarrier OFDM transmission symbol for transmission over a reduced transmission bandwidth.

21. The non-transitory computer-readable storage medium of claim 20, wherein the sensor device comprises an OFDM transmitter that is configured in accordance with an IEEE 802.11 standard to operate at the down-clocked sample clock rate.

22. The non-transitory computer-readable storage medium of claim 21, wherein the sensor device is coupled to a metering apparatus and is further configured to:

read sensor data from the metering apparatus; and

transmit the sensor data at predetermined time intervals,

wherein the transmission of the sensor data comprises transmission of a physical layer service data unit (PSDU) comprising a plurality of OFDM transmission symbols,

wherein the sensor data including padding bits are mapped to active tones of the OFDM transmission symbols and

zeros are mapped to nulled tones of the OFDM transmission symbols.

23. The non-transitory computer-readable storage medium of claim 22 wherein the sensor device is further configured to transmit at a transmission frequency of between 800 MHz and 1.0 GHz, and

wherein the reduced transmission bandwidth is no greater 2 MHz.

24. A wireless device for transmitting a packet comprising one or more orthogonal frequency division multiplexed (OFDM) transmission symbols, the wireless device comprising processing circuitry and transceiver circuitry configured to:

map data to active tones and map zeroes to nulled tones of a set of OFDM tones to generate an OFDM symbol comprising both the active and the nulled tones; and

down-clock the OFDM symbol to generate an OFDM transmission symbol for transmission over a reduced transmission bandwidth.

25. The wireless device of claim 24, wherein the wireless device is configured to perform an inverse-discrete Fourier transform (IDFT) based on a sample clock rate for transmission of the OFDM transmission symbol over the reduced transmission bandwidth.

26. The wireless device of claim 25 wherein the wireless device is configured to:

multiplex the data that is to be mapped to the active tones with the zeroes that are to be mapped to the nulled tones; and

perform the IDFT on the multiplexed data to generate a time-domain signal corresponding to the OFDM symbol having the data on the active tones and zeroes on the nulled tones.

27. The wireless device of claim 24 wherein the number of active and nulled tones being based on a nulling factor.

28. The wireless device of claim 25 wherein the sample clock rate is a down-clocked sample clock rate configured to reduce the transmission bandwidth by a factor of ten or more.

29. The wireless device of claim 25 wherein when the sample clock rate is down-clocked by up to one-tenth or more.

30. The wireless device of claim 24 wherein the reduced transmission bandwidth comprises bandwidths of 2 MHz, 4 MHz, 8 MHz or 16 MHz using sets of 52, 108, 234 and 468 tones, respectively.