Mapping a transmission stream in a virtual baseband to a physical baseband with equalization

• US 8,989,286 B2
• Filed: 11/10/2011
• Issued: 03/24/2015
• Est. Priority Date: 11/10/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: He, Yong, Tan, Kun, Shen, Haichen, Zhang, Jiansong, Zhang, Yongguang
• Primary Examiner(s): Malek, Leila
• Application Number:
  US13/294,093
• Publication Number:
  US 20130122949A1
• Time in Patent Office: 1,230 Days
• Field of Search: 375/260, 370/329, 455/62, 455/509
• US Class Current: 375/260
• CPC Class Codes: H04B 7/24 for communication between two or more posts wireless communication networks H04W
• 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 5/0044 allocation of payload
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: Y02D 30/70 in wireless communication networks

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 transmission components associated with 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 physical transmission symbol composed of time-domain samples derived from the mapped frequency components and a cyclic prefix. In the receive path, a time-domain symbol received on the physical baseband is reshaped and equalized by the virtual spectrum layer in order to recompose a time-domain samples of a transmission stream in the virtual baseband.

Claims

1. A method, comprising:

mapping, by a spectrum virtualization module of a wireless device, a plurality of transmission components associated with a transmission stream produced by a wireless physical layer protocol module of the wireless device for transmission in a virtual frequency band to sub-carriers associated with one or more allocated physical frequency bands, wherein;

the plurality of transmission components associated with the transmission stream includes M frequency components, wherein M is an integer that is not less than one;

the virtual frequency band has a virtual bandwidth; and

the one or more allocated physical frequency bands are part of a physical baseband;

performing an M-point fast Fourier transform on a plurality of time-domain samples of the transmission stream to derive the M frequency components;

performing an N-point inverse fast Fourier transform on the mapped plurality of the M frequency components to derive a plurality of physical time-domain transmission samples, wherein N is an integer that is not less than one and, wherein N is at least as large as M multiplied by a ratio that is a function of the virtual bandwidth and a span of the physical baseband;

appending, by the spectrum virtualization module, a cyclic prefix to a plurality of physical time-domain transmission samples derived by transformation of the plurality of the mapped transmission components associated with the transmission stream to generate a physical transmission symbol for transmission on the one or more allocated physical frequency bands; and

outputting the physical transmission symbol by the spectrum virtualization module.

2. The method of claim 1, wherein the plurality of transmission components associated with the transmission stream includes M time-domain samples of the transmission stream, and wherein the method further comprises deriving the plurality of physical time-domain transmission samples by performing an N-point inverse fast Fourier transform on mapped ones of the M time-domain samples of the transmission stream.

3. The method of claim 1, further comprising determining a length of the cyclic prefix based on a multipath delay.

4. The method of claim 1, further comprising:

scaling, by a bandwidth 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 and a the virtual bandwidth of the virtual frequency band; and

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

5. The method of claim 4, wherein the reducing comprises adding zero-pad samples to the transmission signal, low-pass filtering the zero-pad samples, and decimating the transmission signal to produce a bandwidth-adjusted transmission signal.

6. The method of claim 1, further comprising adjusting, by a sampling rate adjustment module, a sampling rate of a transmission signal that includes the transmission symbol, the adjusting including adding zero-pad samples to the transmission signal, low-pass filtering the transmission signal, and decimating the transmission signal.

7. The method of claim 1, further comprising shifting, by a frequency shift module, 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 the mapping of the plurality of transmission components associated with the transmission stream to the sub-carriers associated with the one or more allocated physical frequency bands.

8. 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 transmission bands and including a receive symbol;

performing, by the spectrum virtualization module, an N-point fast Fourier transform on time-domain samples of the receive symbol to produce N reception components, wherein N is an integer that is not less than one;

equalizing, by the spectrum virtualization module, the N reception components to compensate for channel distortion;

mapping, by the spectrum virtualization module, M of the N compensated reception components that correspond to the one or more allocated physical transmission bands to sub-carriers of a virtual frequency band, wherein M is an integer that is not less than one; and

passing, by the spectrum virtualization module, time-domain samples associated with the M mapped compensated reception components to a wireless physical layer protocol module.

9. The method of claim 8, further comprising performing, by the spectrum virtualization module, an M-point inverse fast Fourier transform on the M mapped compensated reception components to produce the time-domain samples associated with the M mapped compensated reception components.

10. The method of claim 8, further comprising identifying the receive symbol, and removing a cyclic prefix prior to performing the N-point fast Fourier transform.

11. The method of claim 8, further comprising adjusting the receive signal to match a virtual sampling rate of the virtual frequency band.

12. The method of claim 8, further comprising shifting frequencies of the one or more allocated physical frequency bands to compensate for a frequency shift caused by the mapping.

13. A wireless device, comprising:

a processor;

a memory;

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

a physical layer protocol module stored in the memory and executable by the processor to generate a transmission stream for transmission on a virtual transmission band;

a decomposition/recomposition module stored in the memory and executable by the processor to map M transmission components associated with the transmission stream to sub-carriers associated with one or more portions of the physical frequency band that are allocated for transmission, to perform an N-point inverse fast Fourier transform on the mapped M transmission components to produce time-domain samples, and to generate a transmission signal that includes a transmission symbol for transmission by the radio front-end by appending a cyclic prefix to the time-domain samples, wherein M is an integer that is not less than one and wherein N is an integer that is not less than one;

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 an aggregated physical bandwidth of the one or more portions of the physical frequency band allocated for transmission and a virtual bandwidth of the virtual transmission band, wherein the decomposition/recomposition module is further configured to map the M transmission components to the sub-carriers associated with the one or more allocated portions of the physical frequency band based on scaled ones of the one or more portions of the physical frequency band; and

a bandwidth adjustment module configured to reduce a transmission bandwidth of the transmission signal by the factor.

14. The wireless device of claim 13, wherein the bandwidth adjustment module is further configured to reduce the transmission bandwidth by addition of zero-pad samples to the transmission signal, low-pass filtering of the zero-padded samples, and decimation of the transmission signal.

15. The wireless device of claim 13, wherein the decomposition/recomposition module is further configured to generate the M transmission components by performing an M-point fast Fourier transform on M time-domain samples of the transmission stream, wherein M is selected independently of the number of sub-carriers in the virtual transmission band.

16. The wireless device of claim 13, wherein the decomposition/recomposition module is further configured to perform an N-point fast Fourier transform on a receive symbol to produce N receive components, to reverse map M of the N receive components corresponding to portions of a physical frequency band allocated for reception to a virtual reception band, to equalize the mapped M receive components to compensate for signal distortion, and to perform an M-point inverse fast Fourier transform on the compensated M receive components to produce time-domain samples of a reception stream in the virtual reception band.