Mapping signals from a virtual frequency band to physical frequency bands

• US 9,130,711 B2
• Filed: 11/10/2011
• Issued: 09/08/2015
• Est. Priority Date: 11/10/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: He, Yong, Tan, Kun, Shen, Haichen, Zhang, Jiansong, Zhang, Yongguang
• Primary Examiner(s): Pezzlo, John
• Application Number:
  US13/294,039
• Publication Number:
  US 20130121257A1
• Time in Patent Office: 1,398 Days
• Field of Search: 370/210, 370/252, 370/430, 370/478
• US Class Current: 1/1
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 5/0041 Frequency-non-contiguous
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

Embodiments include processes, systems, and devices for reshaping virtual baseband signals for transmission on non-contiguous and variable portions of a physical baseband, such as a white space frequency band. In the transmission path, a spectrum virtualization layer maps a plurality of frequency components derived from a transmission symbol produced by a physical layer protocol to sub-carriers of the allocated physical frequency band. The spectrum virtualization layer then outputs a time-domain signal derived from the mapped frequency components. In the receive path, a time-domain signal received on the physical baseband is reshaped by the virtual spectrum layer in order to recompose a time-domain symbol in the virtual baseband.

Claims

1. A method, comprising:

mapping, by a spectrum virtualization module of a wireless device, a plurality of frequency components that are derived from a transmission symbol produced by a wireless protocol module of the wireless device for transmission on a virtual frequency band, to sub-carriers associated with one or more allocated physical frequency bands;

outputting, by the spectrum virtualization layer, a transmission signal that includes time-domain samples derived from the mapped plurality of frequency components; and

adjusting, by a sampling rate adjustment module, a sampling rate of the transmission signal including adding zero-pad samples to the transmission signal.

2. The method of claim 1, further comprising:

performing, by the spectrum virtualization module, an M-point fast Fourier transform on the transmission symbol to derive the plurality of frequency components; and

performing, by the spectrum virtualization module, an N-point inverse fast Fourier transform on the mapped plurality of frequency components to derive the time-domain samples of the transmission signal.

3. The method of claim 2, wherein the virtual frequency band has a virtual bandwidth, wherein the one or more allocated physical frequency bands are part of a physical baseband, and wherein the method further comprises selecting N to be at least as large as M multiplied by a ratio and of a width of a span of the physical baseband to the virtual bandwidth.

4. The method of claim 2, further comprising selecting M to be at least as large as a number of virtual sub-carriers of the virtual frequency band.

5. The method of claim 1, further comprising:

scaling, by a frequency scaling module of the wireless device, the one or more allocated physical frequency bands by a factor determined at least in part by a ratio of an aggregate bandwidth of the one or more allocated physical frequency bands to a virtual bandwidth of the virtual frequency band; and

reducing, by a bandwidth adjustment module, one or more transmission bandwidths of the transmission signal by the factor, wherein the mapping includes mapping the plurality of frequency components to sub-carriers of scaled ones of the one or more allocated physical frequency bands.

6. The method of claim 5, wherein the reducing comprises adding zero-pad samples to the time domain samples, low-pass filtering the zero-pad samples, and decimating the transmission signal to produce a bandwidth-adjusted transmission signal.

7. The method of claim 6, further comprising:

adjusting, by a sampling rate adjustment module, a sampling rate of the bandwidth-adjusted transmission signal including adding further zero-pad samples to the bandwidth-adjusted transmission signal;

further low-pass filtering the bandwidth-adjusted transmission signal; and

further decimating the bandwidth-adjusted transmission signal.

8. The method of claim 1, further comprising:

low-pass filtering the transmission signal; and

decimating the transmission signal.

9. The method of claim 1, further comprising shifting frequencies of the one or more allocated physical frequency bands by an amount equal to a central frequency of a span of the one or more allocated physical frequency bands upon in response to the mapping of the frequency components to the sub-carriers associated with the one or more allocated physical frequency bands.

10. A method, comprising:

receiving, by a spectrum virtualization module of a wireless device, a receive signal from a radio front-end of the wireless device, the receive signal received by the wireless device on one or more allocated physical reception bands;

adjusting, by the spectrum virtualization module, the receive signal to match a virtual sampling rate of a virtual frequency band;

transforming, by the spectrum virtualization module, time domain samples of the receive signal to produce a plurality of receive frequency components;

mapping, by the spectrum virtualization module, the receive frequency components that correspond to a plurality of non-contiguous allocated physical reception bands to sub-carriers of the virtual frequency band; and

inverse transforming, by the spectrum virtualization module, the mapped receive frequency components to produce a virtual receive symbol in the virtual frequency band.

11. The method of claim 10, wherein:

the transforming includes performing an N-point fast Fourier transform of the receive signal to produce N frequency components; and

the inversely transforming includes collecting M frequency components of the N frequency components that correspond to the plurality of non-contiguous allocated physical reception bands, and performing an M-point inverse fast Fourier transform of the M frequency components.

12. The method of claim 11, wherein the mapping includes mapping the M frequency components to sub-carriers of the virtual frequency band.

13. The method of claim 10, further comprising shifting frequencies of the one or more allocated physical frequency bands by an amount equal to a negative of a central frequency of a span of the one or more allocated physical frequency bands.

14. A wireless device, comprising:

a processor;

a radio front-end configured to wirelessly transmit and receive on a physical baseband;

a protocol module executable by the processor and configured to generate a transmission symbol for transmission on a virtual transmission band; and

a decomposition/recomposition module executable by the processor and configured to perform an M-point fast Fourier transform on the transmission symbol to produce M transmission frequency domain components, to map the M transmission frequency domain components to transmission sub-carriers associated with one or more portions of the physical baseband that are allocated for transmission, and to perform an N-point inverse fast Fourier transform on the mapped M transmission frequency domain components to produce time domain samples of a transmission signal in the physical baseband; and

a bandwidth adjustment module configured to reduce a transmission bandwidth of the transmission signal by addition of zero-pad samples to the time domain samples of the transmission signal.

15. The wireless device of claim 14, wherein the one or more portions of the physical baseband that are allocated for transmission include an aggregate transmission bandwidth, and wherein the decomposition/recomposition module is configured to select N to be at least as large as M multiplied by a ratio that is of a width of a span of the physical baseband to a virtual bandwidth of the virtual transmission.

16. The wireless device of claim 14, further comprising:

a bandwidth scaling module configured to scale the one or more portions of the physical frequency band allocated for transmission by a factor that is determined at least in part by a ratio of the aggregated physical bandwidth of the one or more portions of the physical baseband allocated for transmission to a virtual bandwidth of the virtual transmission band, wherein the decomposition/recomposition module is further configured to map the M transmission frequency domain components to the transmission sub-carriers based on scaled ones of the one or more portions of the physical frequency band, and wherein the reducing the transmission bandwidth of the transmission signal comprises reducing the; and

transmission bandwidth of the transmission signal by the factor.

17. The wireless device of claim 16, wherein the bandwidth adjustment module is further configured to:

low-pass filter of the zero-padded samples; and

decimate the transmission signal.

18. The wireless device of claim 14, further comprising a sampling rate adjustment module configured to add zero-pad samples to the transmission signal, to low-pass filter the transmission signal, and to decimate the transmission signal by a factor that is based on a ratio of a least common multiple of a transmission bandwidth of the transmission signal to a sampling rate of the radio front-end.

19. The wireless device of claim 14, wherein the decomposition/recomposition module is further configured to perform N-point fast Fourier transform on a receive signal to produce N receive frequency components, to reverse map M of the N receive frequency components corresponding to allocated portions of one or more portions of the physical frequency band allocated for reception, and to perform M-point inverse fast Fourier transform on the M receive frequency components to produce time domain samples of a received signal in a virtual reception band.