Method and apparatus for asynchronous OFDMA/SC-FDMA

• US 10,701,685 B2
• Filed: 08/26/2015
• Issued: 06/30/2020
• Est. Priority Date: 03/31/2014
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Abdoli, Javad, Jia, Ming, Ma, Jianglei
• Primary Examiner(s): Patel, Parth
• Assistant Examiner(s): Belete, Berhanu D
• Application Number:
  US14/836,538
• Publication Number:
  US 20160192353A1
• Time in Patent Office: 1,770 Days
• Field of Search: 370336
• CPC Class Codes: H04L 27/26265 Arrangements for sidelobes suppression specially adapted to multicarrier systems, e.g. spectral precoding
• 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 27/26412 Filtering over the entire frequency band, e.g. filtered orthogonal frequency-division multiplexing [OFDM]
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/265 Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators H04L27/26524 takes precedence
• CPC Class Codes: H04L 27/26536 Filtering over the entire frequency band, e.g. filtered orthogonal frequency division multiplexing [OFDM]
• CPC Class Codes: H04L 27/26538 Filtering per subband or per resource block, e.g. universal filtered multicarrier [UFMC] or generalized frequency division multiplexing [GFDM]
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0066 Requirements on out-of-channel emissions
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames

Abstract

Cyclic prefix based OFDM (CP-OFDM) signals can be filtered using a digital filter whose filter length exceeds the length of a cyclic prefix in CP-OFDM symbols of the signal. In one example, the duration of the filtered CP-OFDM symbol may be expressed by the following equation: M=N+L−1, where M is the duration of the filtered CP-OFDM signal, N is a duration of the CP-OFDM signal, and L is the filter length of the digital filter. Digitally filtering the CP-OFDM signal may include convolving a filtering signal with the CP-OFDM signal. The digital filter may include a finite impulse response (FIR) filter or an infinite impulse response (IIR) filter. In some embodiments, a different digital filter may be applied to each sub-band of the CP-OFDM signal.

Claims

1. A method for communicating orthogonal frequency-division multiplexing (OFDM) signals in a wireless communication system, the method comprising:

obtaining, by a first user equipment (UE), a cyclic prefix based orthogonal frequency-division multiplexed (CP-OFDM) signal comprising a plurality of CP-OFDM symbols having a cyclic prefix comprising a repetition of an end of a corresponding CP-OFDM symbol;

applying a digital filter to the CP-OFDM signal to obtain a filtered CP-OFDM signal, wherein main lobes of the filtered CP-OFDM signal have bandwidths in the frequency domain that are equal to bandwidths associated with a plurality of resource blocks (RBs); and

transmitting, to a base station, the filtered CP-OFDM signal over the plurality of RBs, wherein the filtered CP-OFDM signal is decoded by the base station based on a first per-UE based time synchronization corresponding to the first UE, wherein a second filtered CP-OFDM signal from a second UE is decoded by the base station based on a second per-UE based time synchronization corresponding to the second UE, the second per-UE based time synchronization being different from the first per-UE based time synchronization, and wherein the filtered CP-OFDM signal and the second filtered CP-OFDM signal are received as a combined signal by the base station.

2. The method of claim 1, wherein a duration of the filtered CP-OFDM signal is expressed by the following equation:

M=N+L−

1, where M is the duration of the filtered CP-OFDM signal, N is a duration of the CP-OFDM signal, and L is a filter length of the digital filter.

3. The method of claim 1, wherein applying the digital filter to the CP-OFDM signal comprises:

generating a filtering signal; and

convolving the filtering signal with the CP-OFDM signal to obtain the filtered CP-OFDM signal.

4. The method of claim 1, wherein applying the digital filter to the CP-OFDM signal comprises:

applying, by the base station, a different digital filter to each sub-band of the CP-OFDM signal, wherein each sub-band is assigned to a group of one or more UEs.

5. The method of claim 1, wherein applying the digital filter to the CP-OFDM signal comprises:

applying, by the first UE, the digital filter to a specific sub-band carrying the CP-OFDM signal, the specific sub-band being assigned to the first UE.

6. The method of claim 1, wherein a bandwidth of the digital filter is variable.

7. The method of claim 6, further comprising adjusting the bandwidth of the digital filter in accordance with a bandwidth of the CP-OFDM signal.

8. The method of claim 6, wherein a radio interface extends between the base station and the first UE, and wherein the CP-OFDM signal is transmitted by the base station.

9. The method of claim 7, wherein the CP-OFDM signal is transmitted over a specific frequency sub-band.

10. The method of claim 1, wherein the transmitting comprises:

transmitting the filtered CP-OFDM signal without time synchronization with respect to the second UE served by the base station.

11. A first UE, comprising:

a processor; and

a computer readable storage medium storing programming comprising instructions for execution by the processor, that when executed cause the first UE to;

obtain a cyclic prefix based orthogonal frequency-division multiplexed (CP-OFDM) signal comprising a plurality of CP-OFDM symbols having a cyclic prefix comprising a repetition of an end of a corresponding CP-OFDM symbol;

apply a digital filter to the CP-OFDM signal to obtain a filtered CP-OFDM signal, wherein main lobes of the filtered CP-OFDM signal have bandwidths in the frequency domain that are equal to bandwidths associated with a plurality of resource blocks (RBs); and

transmit, to a base station, the filtered CP-OFDM signal over the plurality of RBs, wherein the filtered CP-OFDM signal is decoded by the base station based on a first per-UE based time synchronization corresponding to the first UE, wherein a second filtered CP-OFDM signal from a second UE is decoded by the base station based on a second per-UE based time synchronization corresponding to the second UE, the second per-UE based time synchronization being different from the first per-UE based time synchronization, and wherein the filtered CP-OFDM signal and the second filtered CP-OFDM signal are received as a combined signal by the base station.

12. The first UE of claim 11, wherein a duration of the filtered CP-OFDM signal is expressed by the following equation:

M=N+L−

1, where M is the duration of the filtered CP-OFDM signal, N is a duration of the CP-OFDM signal, and L is a filter length of the digital filter.

13. The first UE of claim 11, wherein the instructions to apply the digital filter to the CP-OFDM signal include instructions to:

generate a filtering signal; and

convolve the filtering signal with the CP-OFDM signal to obtain the filtered CP-OFDM signal.

14. The first UE of claim 11, wherein the programming further includes instructions to adjust a bandwidth of the digital filter in accordance with a bandwidth of the CP-OFDM signal.

15. The first UE of claim 11, wherein a radio interface extends between the base station and the first UE, and wherein the CP-OFDM signal is transmitted by the base station.

16. A method for receiving orthogonal frequency-division multiplexing (OFDM) signals in a wireless communication system, the method comprising:

receiving, by a base station from a first user equipment (UE), a cyclic prefix based orthogonal frequency-division multiplexed (CP-OFDM) signal over a plurality of resource blocks (RBs), the CP-OFDM signal comprising a plurality of CP-OFDM symbols having a cyclic prefix comprising a repetition of an end of a corresponding CP-OFDM symbol;

receiving, by the base station from a second UE, a second CP-OFDM signal, wherein the CP-OFDM signal and the second CP-OFDM signal are received as a combined signal;

applying a digital filter to the CP-OFDM signal to obtain a filtered CP-OFDM signal, wherein main lobes of the filtered CP-OFDM signal have bandwidths in the frequency domain that are equal to bandwidths associated with the plurality of RBs;

applying a second digital filter to the second CP-OFDM signal to obtain a second filtered CP-OFDM signal;

performing a first per-UE based time synchronization of the filtered CP-OFDM signal, the first per-UE based time synchronization corresponding to the first UE;

performing a second per-UE based time synchronization of the second filtered CP-OFDM signal, the second per-UE based time synchronization corresponding to the second UE, the second per-UE based time synchronization being different from the first per-UE based time synchronization; and

processing the filtered CP-OFDM signal and the second filtered CP-OFDM signal.

17. The method of claim 16, wherein a duration of the filtered CP-OFDM signal is expressed by the following equation:

M=N+L−

1, where M is the duration of the filtered CP-OFDM signal, N is a duration of the CP-OFDM signal, and L is a filter length of the digital filter.

18. The method of claim 16, wherein applying the digital filter to the CP-OFDM signal comprises:

applying, by the base station, the digital filter to a specific sub-band of the CP-OFDM signal, the specific sub-band being assigned to the first UE.

19. The method of claim 16, wherein applying the digital filter to the CP-OFDM signal comprises:

applying, by the base station, a different digital filter to each sub-band of the CP-OFDM signal, wherein each sub-band is assigned to a group of one or more UEs.

20. The method of claim 16,

wherein the filtered CP-OFDM signal and the second CP-OFDM signal are received as the combined signal of an asynchronous superposition of the filtered CP-OFDM signal and the second CP-OFDM signal.

21. The method of claim 16, further comprising:

down-sampling the filtered CP-OFDM signal to obtain a down-sampled CP-OFDM signal; and

scaling the down-sampled CP-OFDM signal to obtain a scaled CP-OFDM signal to account for an effect of the down-sampling.

22. An apparatus, comprising:

a processor; and

a computer readable storage medium storing programming for execution by the processor, that when executed cause the apparatus to perform operations, the operations comprising;

receiving, from a first user equipment (UE), a cyclic prefix based orthogonal frequency-division multiplexed (CP-OFDM) signal over a plurality of resource blocks (RBs), the CP-OFDM signal comprising a plurality of CP-OFDM symbols having a cyclic prefix comprising a repetition of an end of a corresponding CP-OFDM symbol;

receiving, from a second UE, a second CP-OFDM signal, wherein the CP-OFDM signal and the second CP-OFDM signal are received as a combined signal;

applying a digital filter to the CP-OFDM signal to obtain a filtered CP-OFDM signal, wherein main lobes of the filtered CP-OFDM signal have bandwidths in the frequency domain that are equal to bandwidths associated with the plurality of RBs;

applying a second digital filter to the second CP-OFDM signal to obtain a second filtered CP-OFDM signal;

performing a first per-UE based time synchronization of the filtered CP-OFDM signal, the first per-UE based time synchronization corresponding to the first UE;

performing a second per-UE based time synchronization of the second filtered CP-OFDM signal, the second per-UE based time synchronization corresponding to the second UE, the second per-UE based time synchronization being different from the first per-UE based time synchronization; and

processing the filtered CP-OFDM signal.

23. The apparatus of claim 22, the operations further comprising:

down-sampling the filtered CP-OFDM signal to obtain a down-sampled CP-OFDM signal; and

scaling the down-sampled CP-OFDM signal to obtain a scaled CP-OFDM signal to account for an effect of the down-sampling.