METHOD AND COMMUNICATION DEVICE FOR COMPENSATING DOPPLER EFFECTS IN RECEIVED WIRELESS COMMUNICATION SIGNALS

Abstract

Doppler effects are compensated for in received wireless communication signals. In a receiver a first signal is received, that was transmitted by a transmitter at a first frequency f.sub.1 and that was received at a doppler-shifted first frequency f.sub.1′ and a second signal, that was transmitted by said transmitter at a second frequency f.sub.2 and that was received at a doppler-shifted second frequency f.sub.2′ is also received. A frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value. Based on the doppler-shifted first frequency f.sub.1′, the doppler-shifted second frequency f.sub.2′ and the frequency difference f.sub.S, the first frequency f.sub.1 is determined for pre-compensating Doppler effects in the received first signal.

Claims

1. A method for compensating Doppler effects in received wireless communication signals, comprising the steps of: receiving in a receiver of a first signal, that was transmitted by a transmitter at a first frequency f.sub.1 and that was received at a doppler-shifted first frequency f.sub.1′; receiving in said receiver of a second signal, that was transmitted by said transmitter at a second frequency f.sub.2 and that was received at a doppler-shifted second frequency f.sub.2′; wherein a frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value; determining the first frequency f.sub.1 based on said doppler-shifted first frequency f.sub.1′, said doppler-shifted second frequency f.sub.2′ and said frequency difference f.sub.S; using said determined first frequency f.sub.1 for pre-compensating Doppler effects in said received first signal.

2. The method according to claim 1, wherein said first frequency f.sub.1 and said second frequency f.sub.2 are carrier frequencies of two respective communication channels.

3. The method according to claim 1, wherein said first frequency f.sub.1 and said second frequency f.sub.2 are in different frequency domains, for example one of said first and second frequency lies in the 2 GHz domain and the other of said first and second frequency lies in the 4 GHz domain.

4. The method according to claim 1, wherein said first signal and said second signal are both used for transmitting relevant data to said receiver.

5. The method according to claim 1, wherein said first signal is used for transmitting relevant data to said receiver and said second signal is used for transmitting relevant data to another receiver.

6. The method according to claim 1, wherein said first signal and said second signal are transmitted time-sliced.

7. The method according to claim 1, wherein information about said predetermined frequency difference f.sub.S is exchanged between said receiver and said transmitter, preferably during an initial handshake of a wireless communication setup procedure.

8. A receiver for a vehicle, arranged for compensating Doppler effects in received wireless communication signals by performing operations comprising: receiving in a receiver of a first signal, that was transmitted by a transmitter at a first frequency f.sub.1 and that was received at a doppler-shifted first frequency f.sub.1′; receiving in said receiver of a second signal, that was transmitted y said transmitter at a second frequency f.sub.2 and that was received at a doppler-shifted second frequency f.sub.2′; wherein a frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value; determining the first frequency f.sub.1 based on said doppler-shifted first frequency f.sub.1′, said doppler-shifted second frequency f.sub.2′ and said frequency difference f.sub.S; using said determined first frequency f.sub.1 for pre-compensating doppler effects in said received first signal

9. (canceled)

10. A vehicle comprising a receiver arranged for compensating Doppler effects in received wireless communication signals by performing operations comprising: receiving In a receiver of a first signal, that was transmitted by a transmitter at a first frequency f.sub.1 and that was received at a doppler-shifted first frequency f.sub.1′; receiving in said receiver of a second signal, that was transmitted by said transmitter at a second frequency f.sub.2 and that was received at a doppler-shifted second frequency f.sub.2′; wherein a frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value; determining the first frequency f.sub.1 based on said doppler-shifted first frequency f.sub.1′, said doppler-shifted second frequency f.sub.2′ and said frequency difference f.sub.S; using said determined first frequency f.sub.1 for pre-compensating doppler effects in said received first signal.

11. (canceled)

12. (canceled)

13. The receiver according to claim 8, wherein said first frequency f.sub.1 and said second frequency f.sub.2 are carrier frequencies of two respective communication channels.

14. The receiver according to claim 8, wherein said first frequency f.sub.1 and said second frequency f.sub.2 are in different frequency domains, for example one of said first and second frequency lies in the 2 GHz domain and the other of said first and second frequency lies in the 4 GHz domain.

15. The receiver according to claim 8, wherein said first signal and said second signal are both used for transmitting relevant data to said receiver.

16. The receiver according to claim 8, wherein said first signal is used for transmitting relevant data to said receiver and said second signal is used for transmitting relevant data to another receiver.

17. The receiver according to claim 8, wherein said first signal and said second signal are transmitted time-sliced.

18. The receiver according to claim 8, wherein information about said predetermined frequency difference f.sub.S is exchanged between said receiver and said transmitter, preferably during an initial handshake of a wireless communication setup procedure.

19. The vehicle according to claim 10, wherein said first frequency f.sub.1 and said second frequency f.sub.2 are carrier frequencies of two respective communication channels.

20. The vehicle according to claim 10, wherein said first frequency f.sub.1 and said second frequency f.sub.2 are in different frequency domains, for example one of said first and second frequency lies in the 2 GHz domain and the other of said first and second frequency lies in the 4 GHz domain.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For a more complete understanding of the present invention, reference in the following description is made in to the accompanying drawings in which:

[0037] FIG. 1 shows a schematic overview of a receiver, a vehicle and a system according to one or more embodiments of the invention; and,

[0038] FIG. 2 shows a schematic overview of a method according to one or more embodiments of the invention.

DETAILED DESCRIPTION

[0039] FIG. 1 shows a schematic overview of a receiver 100, a vehicle 110 and a system 120 according to one or more embodiments of the invention as described in this document. Furthermore, in FIG. 1 a transmitter 130 has been indicated.

[0040] In one or more embodiments, the receiver 100 may be a communication unit or an Electronic Control Unit (ECU) of a vehicle. In one or more embodiments, the vehicle 110 may be a car, a motorbike, a van, a truck, a bicycle or a scooter. In one or more embodiments, the system 120 comprises (i) the transmitter 130 and (ii) the receiver 100 or the vehicle 110 with the receiver 100. In one or more embodiments, the transmitter may be a base station of cellular network (5G, UMTS, etc.) or a WLAN access point.

[0041] The receiver and the transmitter are arranged for exchanging data using a wireless communication protocol, such as 5G, UMTS or WLAN. According to one or more embodiments, the transmitter transmits a first signal 140 at first frequency f.sub.1 and a second signal 150 at a second frequency f.sub.2. The receiver 100 receives both signals, but because vehicle 110 is moving, the signals are received at a doppler-shifted first frequency f.sub.1′ and a doppler-shifted second frequency f.sub.2′ respectively.

[0042] A frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value. In one or more embodiments, information about the frequency difference f.sub.S is stored in receiver 100. In other embodiments, information about the frequency difference fs is transmitted from transmitter 130 to receiver 100.

[0043] As explained above, the first frequency f.sub.1 may be determined or calculated on the basis of the doppler-shifted first frequency f.sub.1′, the doppler-shifted second frequency f.sub.2′ and the frequency difference f.sub.S, preferably in the receiver 100.

[0044] The determined first frequency f.sub.1 is used for a pre-compensation of the Doppler effect on the first signal, when receiving the first signal at the doppler-shifted first frequency f.sub.1′.

[0045] In one or more embodiments, a Doppler frequency shift f.sub.D=f.sub.1′−f.sub.1 is used or calculated for the pre-compensation. Pre-compensation on the receiver side with a known doppler frequency shift is considered technically trivial and well known in the art.

[0046] In one or more embodiments, the second frequency f.sub.2 is determined or calculated on the basis of the doppler-shifted first frequency f.sub.2′, the doppler-shifted second frequency f.sub.2′ and the frequency difference f.sub.S, preferably in the receiver 100. The determined second frequency f.sub.2 may be used for a pre-compensation of the Doppler effect on the second signal.

[0047] In wireless communication two different frequencies are observable:

[0048] the data signal is transmitted with a signal frequency (when LTE is used, the signal frequency has a magnitude of several MHz), and the carrier signal has a carrier frequency (when LTE is used, the carrier frequency has a magnitude of few GHz). While signal frequencies are dictated by the communication standard such as LTE, carrier frequencies can be selected arbitrarily among the available frequency bands. The available frequency bands are determined by political and regulatory authorities as well as economical competition among the communication providers. However, apart from authorities' constraints there is no technical reason not to select suitable carrier signals and corresponding frequencies for communication.

[0049] Therefore, in one or more embodiments, the frequencies f.sub.1 and f.sub.2 are carrier frequencies of two communication channels, which are selected by the communication provider in such a way that equation f.sub.2=f.sub.1+f.sub.S Error! Reference source not found. and the frequency difference f.sub.S is known to both communication partners, that is the transmitter and the receiver.

[0050] It can be assumed, that all disturbance on the channel, measurement imprecision and other factors impeding the communication is given by the Noise frequency f.sub.N, such that

[00007] $\begin{matrix} f_{1, 2}^{'} = (\frac{c + v_{R x}}{c - v_{T x}}) f_{1, 2} + f_{N_{1, 2}} & (8) \end{matrix}$

and hence

[00008] $\begin{matrix} f_{1} = (\frac{f_{1}^{'} .Math. f_{S}}{f_{2}^{'} - f_{1}^{'} + f_{N_{1}} - f_{N_{2}}}) & (9) \end{matrix}$

[0051] The noise f.sub.N has a direct exponential impact on the quality of the Doppler calculation. The larger the noise, the poorer the quality of the Doppler estimation. However, the degrading effect of noise on the communication channel can be counter-balanced by the choice of the frequency difference f.sub.S. The quality of the estimation may be improved by choosing the frequency difference f.sub.S as large as possible.

[0052] If OFDM subcarrier signals are used, the frequency difference f.sub.S is determined by the OFDM channel width, the number of subcarriers and the width of those individual carriers. Second, the quality of the observed carrier frequencies f.sub.1 and f.sub.2 (or, respectively, the avoidance of noises f.sub.N.sub.1 and f.sub.N.sub.2) has a direct impact on the quality of the estimated Doppler. Measurements of the carrier frequencies of OFDM subchannels are more vulnerable to noise than e.g. measuring carrier frequencies of all subcarriers and calculating a “central OFDM carrier frequency”, thus reducing non-systematic disturbances.

[0053] Therefore, in one or more embodiments, two distinct, and far apart, channels are used for best results. Those two channels can be taken from separate frequency domains. Exemplarily, the upcoming 5G New Radio standard permits transmission of data in the existing LTE frequency range (600 MHz to 6 GHz) and extends available frequencies by millimeter wave bands (24 GHz to 86 GHz). Due to coverage short term, focus will be on the bands between 600 MHz and 5 GHz, but already coupling channels in the range of 2 GHz with channels in the range of 4 GHz offers the frequency difference fs of 2 GHz, which is significantly better than the 20 MHz spacing of outer LTE (4 G) OFDM subcarriers.

[0054] Using an additional channel to counter Doppler presents a significant overhead. If two channels would be used for communication of the same information this would indeed be true. However, since only the frequency of the carrier band is relevant, the data communicated over this coupled channel can be used arbitrarily.

[0055] In one or more embodiments, the first signal and the second signal are both used for transmitting relevant data to said receiver. Together the two bands can transmit twice as much information, thus doubling the bandwidth between the transmitter and receiver, at the cost of overall available channels.

[0056] In one or more embodiments, the first signal is used for transmitting relevant data to said receiver and said second signal is used for transmitting relevant data to another receiver. The second channel can provide its carrier frequency as a reference only and can be used to transmit information for a different receiver—which in turn could use the carrier frequency of the first prior channel as a reference.

[0057] In one or more embodiments, the first signal and the second signal are transmitted time-sliced. In that way the channels can be shared flexibly between different communication pairs.

[0058] In one or more embodiments, information about said predetermined frequency difference fs is exchanged between said receiver and said transmitter, preferably during an initial handshake of a wireless communication setup procedure. Alternatively, the information about said predetermined frequency difference f.sub.S is exchanged using characteristics of the carrier frequencies. E.g. Phase Keying could be used to ensure the correct baseband channels are used, even when the communicated factor is incorrect due to Doppler.

[0059] FIG. 2 shows a schematic overview of a method 200 according to one or more embodiments of the invention. The receiver 100, the vehicle 110 and/or the system 120 of FIG. 1 may be arranged for executing the steps of this method.

[0060] The method 200 may comprise the following steps:

[0061] Step 210: receiving in a receiver of a first signal, that was transmitted by a transmitter at a first frequency f.sub.1 and that was received at a doppler-shifted first frequency f.sub.1′;

[0062] Step 220: receiving in said receiver of a second signal, that was transmitted by said transmitter at a second frequency f.sub.2 and that was received at a doppler-shifted second frequency f.sub.2′, wherein a frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value

[0063] Step 230: determining the first frequency f.sub.1 based on said doppler-shifted first frequency f.sub.1′, said doppler-shifted second frequency f.sub.2′ and said frequency difference f.sub.S;

[0064] Step 240: using said determined first frequency f.sub.1 for pre-compensating Doppler effects in said received first signal.

[0065] A computer program may be provided comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of one or more embodiments of the method as described in this document. A computer-readable medium may be provided, having stored thereon this computer program.

[0066] Furthermore, one or more embodiments may be described by the following: A method, a transmitter, a vehicle and a system for compensating Doppler effects in received wireless communication signals are provided. The method comprises the following steps. In a receiver a first signal is received, that was transmitted by a transmitter at a first frequency f.sub.1 and that was received at a doppler-shifted first frequency f.sub.1′ and a second signal, that was transmitted by said transmitter at a second frequency f.sub.2 and that was received at a doppler-shifted second frequency f.sub.2′ is also received. A frequency difference f.sub.S between the first frequency f.sub.1 and the second frequency f.sub.2 has a predetermined value. Based on said doppler-shifted first frequency f.sub.1′, said doppler-shifted second frequency f.sub.2′ and said frequency difference f.sub.S, the first frequency f.sub.1 is determined for pre-compensating Doppler effects in the received first signal.

[0067] As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, device, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “unit”, “module”, “system”, “device” or “element”.

[0068] Functions or steps described in this document may be implemented as an algorithm executed by a microprocessor of a computer. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied, e.g., stored, thereon.

[0069] It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention.

METHOD AND COMMUNICATION DEVICE FOR COMPENSATING DOPPLER EFFECTS IN RECEIVED WIRELESS COMMUNICATION SIGNALS

Assignee

Inventors

Cpc classification

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H04L25/0222

ELECTRICITY

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H04L2027/0026

ELECTRICITY

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H04L27/2676

ELECTRICITY

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H04B7/01

ELECTRICITY

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H04L25/0238

ELECTRICITY

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H04L27/2657

ELECTRICITY

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H04L27/0014

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H04L25/022

ELECTRICITY

International classification

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H04B7/01

ELECTRICITY

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H04L27/00

ELECTRICITY

Abstract

Claims

Description