• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention relates to a method and system for correcting the Doppler effect of a mobile communication in a high-speed system, such as aircraft and trains. It comprises calculating an error frequency, for a receiver module, as the difference between expected frequency and received frequency; generate a Doppler frequency correction signal in a correction module; providing the Doppler frequency correction signal to a mixer module, where the mixer module also receives the signal with Doppler frequency offset; assign a sign for the Doppler frequency correction signal; mix the signal with Doppler frequency shift and the Doppler frequency correction signal with the assigned sign; and provide a corrected output signal, where the Doppler effect has been canceled. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2716628A1
    申请号:ES201930318
    申请日:2019-04-08
    公开日:2019-06-13
    发明作者:Rodriguez Cesar Briso；Ramirez Cesar Calvo
    申请人:Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

    [0001]
    [0002]
    [0003]
    [0004] OBJECT OF THE INVENTION
    [0005]
    [0006] The invention relates to the technical field of mobile communications and, more specifically, to the correction of signals affected by the Doppler effect in telecommunications systems associated with high-speed transports.
    [0007]
    [0008] BACKGROUND OF THE INVENTION
    [0009] Currently, the ubiquitous mobile communications systems reach all possible areas of use, including modern high-speed transport systems. In this scenario of high-speed mobile communications, it must be taken into account that when a vehicle moves relative to a receiver, the received signal is affected by a physical phenomenon known as a Doppler effect, which causes its central frequency to vary. proportional to the speed at which the receiver and the transmitter move relative to each other.
    [0010]
    [0011] The Doppler effect depends on the frequency transmitted and the speed of the mobile, so its effect becomes more important as the speed of the vehicle increases, being especially relevant in high-speed transport such as airplanes or trains and for communications systems high frequency. In these cases the mobile moves at speeds that can exceed 1000km / h and generates a high Doppler shift. The following table shows some values for trains and aircraft speeds and with frequencies used in mobile communications systems:
    [0012]
    [0013]
    [0014] Current mobile communications systems can operate with moderate Doppler shifts. Specifically, 3G and 4G mobile communication systems are designed to operate with mobile phones traveling at speeds of less than 120 km / h, but for frequencies and high speeds, it may be impossible to synchronize the system, resulting in a deterioration of the system's performance. as speed increases.
    [0015]
    [0016] The mobile communications systems belonging to the state of the art, are designed to operate at low speeds, less than 200Km / h, degrading their performance remarkably at higher speeds and it is not possible to modify the configuration of the receivers that are currently used. Normally the only option is to make small corrections in the receiver demodulator, but these corrections are limited by the design of the receiver, which in many cases is not enough for high speeds.
    [0017]
    [0018] On the other hand, the state of the art includes some solutions to estimate the Doppler frequency shift and the Doppler spectrum that occurs when a mobile moves at a certain speed. However, none of the known inventions corrects the Doppler frequency.
    [0019]
    [0020] Therefore, the state of the art lacks a device to correct the Doppler effect in the high frequency signals used in mobile telecommunication systems in high-speed scenarios.
    [0021]
    [0022] DESCRIPTION OF THE INVENTION
    [0023] In order to achieve the objectives and avoid the drawbacks mentioned above, the present invention describes, in a first aspect, a method for correcting the Doppler effect in a signal received in a receiving device of a mobile communication system. The method comprises the following steps:
    [0024] - receive a signal with Doppler frequency shift;
    [0025] - calculating an error frequency parameter, by a receiver module, where the error parameter corresponds to a difference between a preset expected frequency and the frequency of the received signal in the receiver module;
    [0026] - generating a Doppler frequency correction signal in a correction module, based on the calculated error frequency parameter;
    [0027] - providing the Doppler frequency correction signal generated to a mixing module, where the mixing module also receives the signal with Doppler frequency shift;
    [0028] - assign a sign for the Doppler frequency correction signal; Y
    [0029] - mixing, by the mixing module, the Doppler frequency shift signal and the Doppler frequency correction signal with the assigned sign; Y
    [0030] - providing the receiver module with a corrected output signal comprising the signal mixed by the mixer.
    [0031]
    [0032] The present invention assigns a sign for the correction signal so that the correction frequency is minimized, for which the steps of:
    [0033] -generate, by the correction module, a first control signal associated with a positive sign or a negative sign;
    [0034] - selecting, by the mixing module, one of the two lateral bands resulting from the mixing of the frequency correction signal and the received signal with Doppler frequency shift, as a function of the first generated control signal;
    [0035] - obtaining, by the receiver module, a first error frequency parameter;
    [0036] - generating, by the correction module, a second control signal associated with the opposite sign;
    [0037] - selecting, by the mixing module, the side band contrary to that previously selected, as a function of the second control signal generated;
    [0038] - obtaining, by the receiver module, a second error frequency parameter; and - providing the mixer module with the control signal corresponding to the lowest error frequency parameter obtained, between the first and second error frequency parameters.
    [0039]
    [0040] In one of the embodiments of the invention, selecting a sideband in the mixing module comprises switching a switching device between an upper sideband and a lower sideband as a function of the control signal provided from the correction module.
    [0041]
    [0042] Additionally, a particular embodiment of the invention contemplates limiting the maximum Doppler frequency shift that the received signal may suffer, taking into account the speed at which the receiving device travels. For this, the steps of:
    [0043] - determining a speed of movement of the receiving device;
    [0044] - determine a maximum Doppler frequency shift, based on the determined speed;
    [0045] - check that the error frequency parameter is less than the maximum Doppler frequency offset determined for the determined speed; and - otherwise, assign the opposite sign to the Doppler frequency correction signal. Thus, advantageously, it is interpreted that if the error frequency exceeds the maximum limit, the sign has been assigned erroneously and must be changed to the opposite sign, which will result in the correct cancellation of the Doppler effect.
    [0046]
    [0047] In one embodiment of the present invention, a continuous control, exercised by the correction module, of the sign assigned to the Doppler frequency correction signal is contemplated. The continuous control comprises: detecting a variation of the error frequency parameter above a predetermined threshold; as a result of the detection, determining that a change of sign has occurred in the Doppler frequency shift of the received signal; and assigning the opposite sign to the Doppler frequency correction signal. Thus, the objective of minimizing the correction frequency is advantageously achieved by assuming that the abrupt variation has been due to the change in the sign of the Doppler frequency shift in the received signal.
    [0048]
    [0049] A second aspect of the present invention relates to a system for correcting the Doppler effect in a signal received in a receiving device of a mobile communication system. The system comprises:
    [0050]
    [0051] - a receiver module configured to receive a signal with a Doppler frequency shift and calculate an error frequency parameter, where the error frequency parameter corresponds to a difference between a preset expected frequency and the frequency of the received signal;
    [0052]
    [0053] - a correction module configured to generate a Doppler frequency correction signal, based on the error frequency parameter calculated by the receiver module; providing the generated Doppler frequency correction signal to a mixing module; and assigning a sign for the Doppler frequency correction signal; Y
    [0054]
    [0055] - a mixing module configured for; mix the signal with Doppler frequency shift with the Doppler frequency correction signal, according to the sign assigned; and providing a corrected output signal (6) comprising the mixed signal.
    [0056]
    [0057] Additionally, in one of the embodiments of the invention, speed sensing means are contemplated, wherein the correction module is further configured to determine a speed of movement of the receiving device, based on measurements provided by the speed sensing means; determine a maximum Doppler frequency shift, based on the determined velocity; check that the error frequency parameter is less than the maximum Doppler frequency offset determined for the determined speed; and if not, assign the opposite sign to the Doppler frequency correction signal.
    [0058]
    [0059] The correction module, according to one of the embodiments of the invention, comprises a processor and a direct digital synthesizer, controlled by the processor, configured to generate sinusoidal frequencies equivalent to that of the received input signal.
    [0060]
    [0061] The mixing module, according to one of the embodiments of the invention, is an image rejection mixer configured to select one of the two sidebands resulting from the mixing of the frequency correction signal and the received signal with displacement of Doppler frequency, depending on a control signal provided by the correction module.
    [0062]
    [0063] The image rejection mixer, according to a specific embodiment of the invention, further comprises a switching device configured to switch between an upper side band and a lower side band, as a function of the control signal.
    [0064]
    [0065] In one of the embodiments of the invention, the system comprises a mobile telephone housing the receiver module, the correction module and the receiver module. Thus, advantageously, all the elements are implemented in the receiver device itself and allow the cancellation of the Doppler effect in any communication received in the mobile telephone, although this is in a high-speed system.
    [0066] In a particular embodiment of the invention, the system is implemented in a single electronic device, which is sandwiched between the antenna of the mobile receiver and the base station of the mobile communication system, so that it allows communications regardless of the speed the one that the mobile phone moves.
    [0067] A final aspect of the invention relates to a computer program comprising code means configured to perform the steps described above, when said program is executed on a computer, a digital signal processor, a programmable gate arrangement, an integrated circuit , a microprocessor, a microcontroller or any other form of programmable hardware.
    [0068]
    [0069] Advantageously, the present invention allows the operation of mobile communication systems, for example 3G and 4G, at speeds much higher than those that were designed, thus solving the problem of the current high-speed transport systems, in which higher speeds are handled at 300km / h that significantly deteriorate the performance as the speed increases, as a result of the displacement of the frequency of the link by the Doppler effect.
    [0070]
    [0071] The device of the present invention can be incorporated both to the receiver's input (usually a mobile phone) of a mobile communication system and to the base station, so that it cancels the Doppler shift generated by the speed by correcting the frequency of the received signal by mobile based on its speed.
    [0072]
    [0073] BRIEF DESCRIPTION OF THE FIGURES
    [0074] To complete the description of the invention and in order to help a better understanding of its characteristics, according to an example of embodiment thereof, a set of drawings is attached where, illustrative and not limiting, they have been represented The following figures:
    [0075]
    [0076] Figure 1 shows a block diagram, according to one of the embodiments of the invention, of the Doppler shift correction system, comprising an image rejection mixer, a Doppler correction generator and a receiver.
    [0077]
    [0078] Figure 2 shows the scheme of the image rejection mixer of Figure 1, in which one of the two sidebands generated in the process of mixing the input signal and the Doppler correction signal is eliminated.
    [0079]
    [0080] DETAILED DESCRIPTION OF THE INVENTION
    [0081] The present invention discloses a method and a system for correcting the Doppler effect of a mobile communication in a high-speed environment.
    [0082] The Doppler corrector system of the present invention comprises an electronic circuit and a processor that advantageously estimate and correct the Doppler shift of the frequency that occurs in the radio signals as a consequence of the moving speed of the mobile telephone. For this purpose, in one of the embodiments of the invention, an electronic circuit is proposed which comprises a frequency mixer 1, a Doppler correction generator 2 and a mobile communications receiver 3.
    [0083]
    [0084] As shown in Figure 1, the signal received by the system is a signal with a certain Doppler shift, resulting in the sum of a central frequency f or more a Doppler shift frequency f D. At the entrance of the system, to compensate for the losses, there is a low noise amplifier 4. The output of the amplifier is connected to the frequency mixer 1 as the main element to control the Doppler of the input signal 5. The use of this frequency mixer allows a high rejection of one of the two sidebands that are generated in the mixing process, so that the mobile communications receiver 3 of the system is not affected by it and directly receives a signal with the Doppler cancelled.
    [0085]
    [0086] The generator module of the Doppler correction 2, connected between the mobile communications receiver 3 and the frequency mixer 1, comprises an electronic circuit with a digital frequency generator, based on a direct digital synthesizer controlled by a processor. This circuit is capable of generating sinusoidal frequencies with high frequency accuracy, so that it generates a frequency equivalent to that of the input signal. The processor of this Doppler correction generating module calculates the Doppler correction using as input parameters the speed of the receiver, for example the user's mobile phone (V M ), which is used to calculate what would be the maximum value of expected Doppler frequency, and the Doppler frequency error parameter (ferr) generated by receiver 3, which consists of the frequency variation between the received and the generated Doppler. Depending on these parameters, the Doppler correction frequency f üop © and its sign are calculated, in such a way that the error frequency delivered by the receiver is minimized.
    [0087]
    [0088] Fig. 2 shows a detailed embodiment of a frequency mixing device 1, in which an image rejection mixer 20 is used. The image reject mixer 20 is useful for filtering the image frequency (symmetric frequency of the signal ) at the output of the mixer and stay only with the output signal that minimizes the error frequency. In Figure 2 it can be seen that the mixing circuit with image frequency rejection comprises two mixers 21, 22 receiving the correction frequency signal f Dop (t) generated by the correction module 2 , to which the received signal is applied R (t) through a 90 ° coupler 23. At the output there is a switch 24 connected with a second coupler 90 ° 25, which receives the control signal (+/- f Dop ) sent from the correction module 2 , so that, depending on the assigned sign, the switch selects one of the two sidebands, while the image band is rejected. In this way, this image rejection mixer 20 allows one of the two sidebands to be quickly selected depending on whether the Doppler shift is positive or negative, which allows the receiver to receive the corrected signal, without the Doppler effect that has already been detected. been canceled.
    [0089]
    [0090] According to one of the embodiments of the invention, a signal transmitted by a mobile communication system arrives at a mobile phone traveling at high speed. This received signal R (t) has, as a consequence of the speed (V m ) to which the mobile moves with respect to the communication base station, a Doppler shift that can be positive or negative / f. The signal R (t) is mixed with a frequency generated by the Doppler correction generating module so that the output signal 6 R '(t) reaches the receiver 3 without Doppler shift.
    [0091]
    [0092] The correction frequency f Dop (t) generated by the Doppler correction generating module is a low frequency signal necessary to correct the Doppler generated in the propagation. This frequency goes from 0Hz to a few tens of KHz, as can be seen in table 1, and is adjusted according to the speed (which can be obtained, for example, thanks to the odometer of the vehicle in which the receiver is traveling), which allows us to limit a maximum frequency, and the angle of arrival of the signal to the mobile, where the arrival angle marks the sign and the Doppler frequency.
    [0093]
    [0094] The Doppler correction sign estimation is also carried out in the Doppler correction generator module, since it is necessary to provide a control signal (+/- f Dop ) to the frequency mixer module 1 to select the frequency sign of correction f Dop (t).
    [0095] The sign of the Doppler is determined according to the error signal (f err ) supplied by the receiver following an iterative method, so that the sign is calculated initially by testing the two signs (+/-) and choosing the one that generates a lower error frequency (f err ). Additionally, maximum levels are established for the maximum expected error frequency, which are calculated based on the mobile speed (V M ), so that once the correction frequency is calculated with one of the signs randomly assigned, if the assigned sign causes the error frequency to be greater than the maximum expected error frequency, the processor will immediately change to the opposite sign the correction frequency f Dop (t) .
    [0096]
    [0097] Once the initial sign has been determined, the generator module of the Doppler correction or simply the correction module, continues to exercise control of the sign, always in order to minimize the signal f err . Thus, when it detects a sudden change in f err , in which its value rises sharply, the correction module determines that a Doppler sign change has occurred and changes the sign of the control signal (+/- f Dop ) provided to the mixer module in order to minimize f err .
    [0098]
    [0099] Depending on the sign provided, the frequency mixer 1 selects the corresponding side band, where for example, according to Figure 2, a positive sign corresponds to the upper sideband and a negative sign to the lower sideband.
    [0100]
    [0101] In the following example, provided in an illustrative manner, the calculation of the error frequency (f err ) and the choice of the sign of the Doppler frequency f Dop (t) in the correction generator module 2, according to an embodiment, is described in detail. of the invention. First, it is based on a received signal 5 R (t) that includes the Doppler shift:
    [0102] R (t) = f or + f D;
    [0103]
    [0104] whereby the output signal 6 R '(t) provided by the mixer is:
    [0105]
    [0106] R '(t) = f or + (f D ± f DO P (t)) = f or + f err
    [0107]
    [0108] Assuming that, at the initial instant (t 0 ), the corrector module 2 makes an estimation of the correction frequency f DO P (t) = 0, the output signal 6 of the mixer is equal to the input signal 5 y, therefore, the error frequency will initially be equal to the Doppler shift frequency:
    [0109] R '(t) = R (t) and f err (t o ) = f D
    [0110]
    [0111] At the next instant (t i ) the corrector module generates f DOp (t i ) with a random sign / - so that the processor evaluates which of the two signs results in a lower error frequency and chooses it:
    [0112]
    [0113] f err (t 1 ) <f err (^) = The initial sign is the correct one
    [0114] f err (t 1 )> f err (^) = The sign is the opposite
    [0115]
    [0116] Once the correct sign has been determined, corrector module 2 maintains this sign until it detects a sudden change in the value of f err (t), in which case it starts the process of sign adjustment again.
    [0117]
    [0118] The present invention has application in any mobile communication system, especially in those high-speed transport systems such as railways and airplanes.
    [0119]
    [0120] The present invention should not be limited to the embodiment described here. Other configurations may be made by those skilled in the art in view of the present disclosure. Accordingly, the scope of the invention is defined by the following claims.
    权利要求:
    Claims (12)
    [1]
    Method for correcting the Doppler effect in a signal received in a receiving device of a mobile communication system, where the method is characterized in that it comprises the following steps:
    - receive a signal with Doppler frequency shift (5);
    - calculating an error frequency parameter, by a receiver module (3), where the error parameter corresponds to a difference between a pre-established expected frequency and the frequency of the signal received in the receiver module (3);
    - generating a Doppler frequency correction signal in a correction module (2), based on the calculated error frequency parameter;
    - providing the Doppler frequency correction signal generated to a mixing module (1), where the mixing module also receives the signal with Doppler frequency shift;
    - assign a sign for the Doppler frequency correction signal; Y
    - mixing, by the mixing module, the Doppler frequency shift signal and the Doppler frequency correction signal with the assigned sign; Y
    - providing the receiver module (3) with a corrected output signal (6) comprising the signal mixed by the mixer.
    [2]
    2. Method according to claim 1 wherein assigning a sign for the correction signal comprises:
    - generate, by the correction module, a first control signal associated with a positive sign or a negative sign;
    - selecting, by the mixing module, one of the two lateral bands resulting from the mixing of the frequency correction signal and the received signal with Doppler frequency shift, as a function of the first generated control signal;
    - obtaining, by the receiver module, a first error frequency parameter;
    - generating, by the correction module, a second control signal associated with the opposite sign;
    - selecting, by the mixing module, the side band contrary to that previously selected, as a function of the second control signal generated;
    - obtaining, by the receiver module, a second error frequency parameter; Y - providing the mixer module with the control signal corresponding to the lowest error frequency parameter obtained, between the first and second error frequency parameters.
    [3]
    Method according to claim 2, wherein selecting a sideband in the mixing module comprises switching a switching device (24) between an upper sideband and a lower sideband as a function of the control signal provided from the correction module ( two).
    [4]
    4. Method according to any of the preceding claims which further comprises:
    - determining a speed of movement of the receiving device;
    - determine a maximum Doppler frequency shift, based on the determined speed;
    - check that the error frequency parameter is less than the maximum Doppler frequency offset determined for the determined speed; and - otherwise, assign the opposite sign to the Doppler frequency correction signal.
    [5]
    Method according to any one of the preceding claims wherein the correction module exerts a continuous control of the sign assigned to the Doppler frequency correction signal, comprising:
    - detecting a variation of the error frequency parameter above a predetermined threshold;
    as a result of the detection, determining that a change of sign has occurred in the Doppler frequency shift of the received signal; Y
    - assign the opposite sign to the Doppler frequency correction signal.
    [6]
    6. System for correcting the Doppler effect in a signal received in a receiving device of a mobile communication system, where the system is characterized in that it comprises:
    - a receiver module (3) configured to receive a signal with Doppler frequency shift and calculate an error frequency parameter, where the error frequency parameter corresponds to a difference between a preset expected frequency and the frequency of the received signal;
    - a correction module (2) configured to generate a Doppler frequency correction signal, based on the error frequency parameter calculated by the receiver module; providing the generated Doppler frequency correction signal to a mixer module (1); and assigning a sign for the Doppler frequency correction signal; Y
    - a mixing module (1) configured for; mix the signal with Doppler frequency offset with the Doppler frequency correction signal, according to the assigned sign; and providing a corrected output signal (6) comprising the mixed signal.
    [7]
    System according to claim 6 further comprising speed sensing means, wherein the correction module is further configured to determine a speed of movement of the receiving device, based on measurements provided by the speed sensing means; determine a maximum Doppler frequency shift, based on the determined velocity; check that the error frequency parameter is less than the maximum Doppler frequency offset determined for the determined speed; and if not, assign the opposite sign to the Doppler frequency correction signal.
    [8]
    System according to any of claims 6-7 wherein the correction module comprises a processor and a direct digital synthesizer, controlled by the processor, configured to generate sinusoidal frequencies equivalent to that of the received input signal.
    [9]
    System according to any of claims 6-8 wherein the mixing module is an image rejection mixer (20) configured to select one of the two sidebands resulting from the mixing of the frequency correction signal and the received signal with Doppler frequency offset, depending on a control signal provided by the correction module.
    [10]
    System according to claim 9 wherein the image rejection mixer further comprises a switching device (24) configured to switch between an upper side band and a lower side band, as a function of the control signal.
    [11]
    11. System according to any of claims 6-10 further comprising a mobile telephone housing the receiver module, the correction module and the receiver module.
    [12]
    12. A computer program comprising code means configured to perform the steps of any of claims 1-5, when said program is executed on a computer, a digital signal processor, a programmable gate arrangement, an integrated circuit, a microprocessor, a microcontroller or any other form of programmable hardware.
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    同族专利:
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    引用文献:
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    US4199809A|1976-04-05|1980-04-22|The United States Of America As Represented By The Secretary Of The Navy|Programmable data terminal set|
    US5936961A|1993-06-07|1999-08-10|Alcatel Mobile Phones|Signalling packet for communication system with reference modulated in accordance with a time-dependent law|
    CN101958734A|2010-10-19|2011-01-26|京信通信系统（中国）有限公司|Integrated wireless coverage solution|
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    ES201930318A|ES2716628B2|2019-04-08|2019-04-08|METHOD AND SYSTEM TO CORRECT THE DOPPLER EFFECT OF A MOBILE COMMUNICATION IN A HIGH-SPEED SYSTEM|ES201930318A| ES2716628B2|2019-04-08|2019-04-08|METHOD AND SYSTEM TO CORRECT THE DOPPLER EFFECT OF A MOBILE COMMUNICATION IN A HIGH-SPEED SYSTEM|
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