Mast sway compensated sensing signaling

Abstract

There is provided techniques for mast sway compensated sensing signaling. A method is performed by a transmitter unit comprises an antenna unit. The method comprises obtaining an indication of mast sway of the antenna unit. The method comprises transmitting, from the antenna unit, a sensing signal in conjunction with initiating compensation for the mast sway at time of transmission of the sensing signal. The sensing signal is destined for a receiver unit.

Description

[0001] MAST SWAY COMPENSATED SENSING SIGNALING

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to methods, a transmitter unit, a receiver unit, computer programs, and a computer program product for mast sway compensated sensing signaling.

[0004] BACKGROUND

[0005] Operational principles of bi-static sensing are illustrated in the communication system 100a of Fig. 1. As shown in this figure, the communication system 100a comprises a transmitter (TX) unit 200 and receiver (RX) unit 300. The TX unit 200 comprises an antenna unit 225 configured to emit sensing signals which, after their propagation in the existing environment, are received at an antenna unit 325 at the RX unit 300. Assuming that there is only one object 110 to be sensed, and provided that the TX unit 200 and the RX unit 300 are synchronized in time, the RX unit 300 is able to measure the Time of Flight (ToF). From the ToF (Tobject), the bi-static range (Dtot-object), which is the distance (DTX -object) between the TX unit 200 and the object 110 plus the distance (DObject-Rx) between the object 110 and the RX unit 300, is obtained. In the absence of knowledge of the Angle of Departure (AoD) in the TX unit 200 and the Angle of Arrival (AoA) in the RX unit 300, from the bi-static range it can be concluded that the object 110 is placed somewhere on the surface of an ellipsoid 150 with focal points in the TX unit 200 and RX unit 300. In contrast, if the AoD and / or the AoA are available, more accurate knowledge of the position of the object 110 on the ellipsoid 150 can be extracted. In both cases, it is assumed that the positions of the TX unit 200 and RX units 300 are known (and the distance between them).

[0006] As indicated before, the efficient operation of bi-static sensing relies on the time synchronization between the TX unit 200 and RX unit 300. Achieving accurate synchronization between physically separated TX units 200 and RX units 300 is a challenge compared to mono-static sensing where the TX unit 200 and the RX unit 300 share a common clock source and common time.

[0007] Time synchronization would be needed to accurately determine Tobject and thereby for determining Dtot- object, i.e. the RX unit 300 would need to accurately relate a reflection reception time (Trxobject ) with the transmission time at the TX unit 200 (Ttx). A time error between the TX unit 200 and the RX unit 300 of only 3 nanoseconds would approximately correspond to a 1 meter range inaccuracy.

[0008] Radio-frequency (RF) carrier phase synchronization will be needed to detect mobility of the object 110 and to estimate the velocity of the object 110. In more detail, this can be achieved by detecting RF carrier phase changes in the reflected path. A relative RF frequency error of e.g., 3 parts per billion between the TX unit 200 and the RX unit 300 at a carrier frequency of 3.5GHz would correspond to a frequency difference of approximately 10 Hz, which then would be similar as a Doppler shift by a pedestrian and hence would limit the lowest possible speed of the object 110 that could be accurately detected. Different means to synchronize physically separated TX units 200 and RX units 300 exist, e.g. having individual local global navigation satellite system (GNSS) synchronized receivers, having a common timing source such as a GNSS synchronized receiver with Precision Time Protocol (PTP) and / or Synchronous Ethernet (SyncE) to distribute time and frequency towards the TX units 200 and RX units 300. The distribution path generally involves multiple nodes and components, each contributing to total errors all the way up to the antenna reference point. Therefore, achieving very strict inter-node synchronization is challenging and complex also considering the required wired infrastructure that needs to be installed. Improved frequency accuracy and stability of local oscillators beyond what is needed for communication comes with additional cost. GNSS synchronized receivers will require installations allowing free view of sky, which is not always possible or requires expensive installations. In addition, jamming of GNSS receivers is a well-acknowledged problem.

[0009] Using over-the-air synchronization in various forms, and especially using a direct synchronization between the TX unit 200 and RX unit 300, is a promising technique to achieve accurate and cost-efficient synchronization for bi- and multi-static sensing. For the direct synchronization, the transmitted sensing signal from the TX unit 200 is used both for the sensing of objects and synchronization at the RX unit 300. The synchronization path could be either Line-Of-Sight (LOS) or a controlled (well characterized) Non-Line-Of-Sight (NLOS) path. Such approach would also benefit from canceling out errors or changes in the TX unit 200 and / or the RX unit 300 which are common for the reflected path and the synchronization path, e.g. errors / changes within the radio chains of the TX unit 200 and / or RX unit 300 such as delay or phase changes.

[0010] Mast sway and twist is investigated for different types of installations, thin pole, thick pole and telecom masts in “Impact of mounting structures twists and sways on point-to-point millimeter-wave backhaul links” by Rashid Kalimulin et al, published in the proceedings of the 2015 IEEE International Conference on Communication Workshop (ICCW). For mobility detection, fast mast sway caused mainly by wind is noted to have a periodic deviation with a typical frequency range of 0.4-5 Hz. The deflections for telecommunication masts are noted to be up to 1.2°. The height of the telecommunication masts is not mentioned. If assuming a telecommunication mast height of 20 meters and an inclination angle of 1.2°, this would correspond to a mast sway amplitude of about 0.4 meters. Combining this with a frequency of 5Hz would give a speed of about 13 meters / second. This is likely not fully representative and instead using an amplitude of 0.2 meters with a frequency of 1 Hz would give about 1.3 meters / second. There also exists slow mast sway with variation over daytime (i.e., with a duration of about 5-12 hours) caused by variations in heating related to the sun, with deflections for slow mast sway noted to be typically between 0.3-1°. The mast sway movement of some present and future communication systems will have a significant impact of the system ability of introducing sensing application, whether it be a mono-bi- or a bi / multi-static sensing system. Mast sways as described above will change the position of the TX unit 200 and RX unit 300 overtime. This is in the communication system 100b of Fig. 2 illustrated by mast sway 130, 140 of the antenna units 225, 325. As illustrated in Fig. 2, the mast sway 130, 140 will change the measured ToF (Tobject) and the bi-static range (Dtot-object) dependent the relative movement of the TX unit 200 and RX unit 300, and thereby create a range uncertainty if not compensated for. In Fig. 2, a NLOS path is created by the signal transmitted from the TX unit 200 being reflected by a surface 120 before reaching the RX unit 300. If using an over-the-air synchronization method, as also illustrated in Fig. 2, either by using an LOS path or an NLOS synchronization reference path, the different channels for the synchronization reference path and the sensing path would even if using the same transmitted signal for both sensing and synchronization, change differently due to the mast sway 130, 140. That is, a change in the LOS or NLOS reference path does not correctly compensate for a change in the sensing path. If over-the-air synchronization and sensing are performed at different points in time, the relative difference can be even larger, dependent the change of relative location of the antenna units 225, 325 between the two occasions.

[0011] For mobility detection by measuring RF carrier phase changes for an object reflected path towards a synchronization reference path, the relative motion of the TX unit 200 and the RX unit 300 will, if the mast sway 130, 140 is not properly compensated for, result in that fixed and static objects could falsely appear as moving objects and vice versa. That is, the mast sway 130, 140 sets a limit for the lowest mobility level the sensing system can detect. If the TX unit 200 and the RX units 300 in a bi-static sensing scenario move in opposite directions with respect to each other, an even larger speed could falsely be detected for a stationary object.

[0012] Hence, there is a need for improved sensing in the presence of mast sway.

[0013] SUMMARY

[0014] An object of embodiments herein is to address the above issues, to thereby provide accurate sensing even in the presence of mast sway.

[0015] A particular object is to enable mono-static sensing or bi-static sensing (or even multi-static sensing).

[0016] According to a first aspect there is presented a transmitter unit for mast sway compensated sensing signaling. The transmitter unit comprises processing circuitry and an antenna unit. The transmitter unit is configured to obtain an indication of mast sway of the antenna unit. The transmitter unit is configured to transmit, from the antenna unit, a sensing signal in conjunction with initiating compensation for the mast sway at time of transmission of the sensing signal. The sensing signal is destined for a receiver unit.

[0017] According to a second aspect there is presented a method for mast sway compensated sensing signaling.

[0018] The method is performed by a transmitter unit comprises an antenna unit. The method comprises obtaining an indication of mast sway of the antenna unit. The method comprises transmitting, from the antenna unit, a sensing signal in conjunction with initiating compensation for the mast sway at time of transmission of the sensing signal. The sensing signal is destined for a receiver unit.

[0019] According to a third aspect there is presented a computer program for mast sway compensated sensing signaling. The computer program comprises computer code which, when run on processing circuitry of a transmitter unit comprises an antenna unit, causes the transmitter unit to perform actions. One action comprises the transmitter unit to obtain an indication of mast sway of the antenna unit. One action comprises the transmitter unit to transmit, from the antenna unit, a sensing signal in conjunction with initiating compensation for the mast sway at time of transmission of the sensing signal. The sensing signal is destined for a receiver unit.

[0020] According to a fourth aspect there is presented a receiver unit for mast sway compensated sensing signaling. The receiver unit comprises processing circuitry and an antenna unit. The receiver unit is configured to receive, by the antenna unit, a sensing signal. The sensing signal originates from a transmitter unit. The receiver unit is configured to obtain an indication of mast sway of the antenna unit. The receiver unit is configured to compensate the sensing signal in accordance with the mast sway at time of reception of the sensing signal.

[0021] According to a fifth aspect there is presented a method for mast sway compensated sensing signaling. The method is performed by a receiver unit comprises an antenna unit. The method comprises receiving, by the antenna unit, a sensing signal. The sensing signal originates from a transmitter unit. The method comprises obtaining an indication of mast sway of the antenna unit. The method comprises compensating the sensing signal in accordance with the mast sway at time of reception of the sensing signal.

[0022] According to a sixth aspect there is presented a computer program for mast sway compensated sensing signaling. The computer program comprises computer code which, when run on processing circuitry of a receiver unit comprising an antenna unit, causes the receiver unit to perform actions. One action comprises the receiver unit to receive, by the antenna unit, a sensing signal. The sensing signal originates from a transmitter unit. One action comprises the receiver unit to obtain an indication of mast sway of the antenna unit. One action comprises the receiver unit to compensate the sensing signal in accordance with the mast sway at time of reception of the sensing signal.

[0023] According to a seventh aspect there is presented a computer program product comprising a computer program according to at least one of the third aspect and the sixth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0024] Advantageously, these aspects can be used to mitigate object sensing range uncertainties and object mobility detection limitations otherwise caused by mast sway effects. In turn, these aspects therefore provide accurate sensing even in the presence of mast sway. Advantageously, these aspects enable mono-static sensing or bi-static sensing (or even multi-static sensing). In turn, these aspects therefore require less overhead, thus reducing delays, compared to methods relying on synchronization between the TX unit and the RX unit.

[0025] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0026] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0029] Figs. 1 and 2 are schematic diagrams illustrating communication systems according to examples;

[0030] Figs. 3 and 4 are flowcharts of methods according to embodiments;

[0031] Fig. 5 is a schematic illustration of deviation and acceleration of a mast in a coordinate system according to embodiments;

[0032] Fig. 6 is a schematic illustration of waveforms for periodic mast sway according to embodiments;

[0033] Fig. 7 is a schematic illustration of projection of mast deviation to beams in different directions according to embodiments;

[0034] Fig. 8 is a schematic diagram showing functional units of a transmitter unit according to an embodiment;

[0035] Fig. 9 is a schematic diagram showing functional modules of a transmitter unit according to an embodiment;

[0036] Fig. 10 is a schematic diagram showing functional units of a receiver unit according to an embodiment;

[0037] Fig. 11 is a schematic diagram showing functional modules of a receiver unit according to an embodiment; and

[0038] Fig. 12 shows one example of a computer program product comprising computer readable means according to an embodiment. DETAILED DESCRIPTION

[0039] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0040] As noted above, there is a need for improved sensing in the presence of mast sway.

[0041] The embodiments disclosed herein therefore relate to techniques for mast sway compensated sensing signaling. In order to obtain such techniques there is provided a TX unit, a method performed by the TX unit, a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the TX unit, causes the TX unit to perform the method. In order to obtain such techniques, there is further provided an RX unit, a method performed by the RX unit, and a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the RX unit, causes the RX unit to perform the method.

[0042] With continued reference to Fig. 2, at least some of the herein disclosed embodiments are based on detecting that mast sway 130, 140 occurs. This detection can be performed independently at the TX unit 200 and the RX unit 300. Based on this detection, a determination can be made whether mast sway compensation is to be performed. Again, this determination can be performed independently at the TX unit 200 and the RX unit 300. The determination might, for example, depend on an active sensing service, measured data for current mast sway (such as its amplitude and frequency), required sensing performance accuracy (such as range uncertainty and mobility detection thresholds for low object speeds).

[0043] A system for mast sway compensated sensing signaling comprises a TX unit 200 as hereinafter will be disclosed and an RX unit 300 as hereinafter will be disclosed. Depending on the relative locations of the antenna units 225, 325, the herein disclosed embodiments are applicable to either bi-static sensing or even multi-static sensing or mono-static sensing. That is, in some embodiments, the TX unit 200 and the RX unit 300 are configured for bi-static or multi-static sensing, and in other embodiments, the TX unit 200 and the RX unit 300 are configured for mono-static sensing. The former might be the case where the antenna units 225, 325 are provided in physically separated devices whereas the latter might be the case where the antenna units 225, 325 are provided in one and the same device.

[0044] Examples where bi-static sensing is used and where beamforming is used at the antenna unit 325 of the RX unit 300 will be disclosed next. According to a first example, for beamformed transmission of sensing signals from the TX unit 200, for each beam direction in which the sensing signals are sent, the TX unit 200 pre-compensates the transmission of the sensing signal to compensate for the movement of the antenna unit 225 at the time of the transmission of the sensing signal. Similarly, the RX unit 300 can perform compensation in each of its beam directions to individually compensate each of the beam direction dependent the relative movement of its antenna unit 325. The compensation could either be performed based on real time measured inertial measurement unit (IMU) data, based on existing measured data and prediction for e.g., an upcoming transmission of sensing signals from the TX unit 200 (to allow delay loops in processing for precompensation of data at the TX unit 200) or based on a model from historically measured, sensed, or estimated, IMU data.

[0045] According to a second example, for omni-directional transmission of sensing signals from the TX unit 200, the TX unit 200 uses sensor data, such as data obtained from an IMU in the TX unit 200, to measure and characterize the movement of the antenna unit 225 over time. The TX unit 200 can then send information based on the sensor data to the RX unit 300. The RX unit 300 could then perform postcompensation for its own antenna movement (i.e., movement of the antenna unit 325) as well as for the antenna unit 225 at the TX unit 200 based on the information received from the TX unit 200. The information can be sent in time proximity to the transmission of the sensing signal from the TX unit 200 to reflect the position and speed of change of the antenna unit 225 at the TX unit 200 as valid for when the sensing signal was transmitted. Alternatively, the information could be sent before the sensing signal is sent, potentially either including a prediction of the position and speed of change of the antenna unit 225 or information from which such prediction can be derived. Yet alternatively, the information could be sent after the sensing signal has been transmitted and then include actual antenna data as measured at the TX unit 200 when the sensing signal was transmitted.

[0046] An example where mono-static sensing is used will be disclosed next.

[0047] For mono-static the TX unit 200 and / or the RX unit 300 could perform compensation based on sensing directions and antenna data similar as performed in a bi-static scenario with the difference that transmission of the sensing signal and its related reception occurs in the same antenna directions.

[0048] In case the antenna unit 225 in the TX unit 200 does not support beamforming with individual phase control of different beams, as an alternative to transmitting compensated sensing signals, the information about the deviation can be transmitted to the RX unit 300, either in a direct link to each affected RX unit 300, as a broadcast message, or indirectly by informing some network node in the communication system 100a, 100b that then informs the RX units 300 about mast deviation of any TX units 200 in their area.

[0049] In hybrid schemes, the carrier phase can be compensated at the TX unit 200 in the different beams to mitigate Doppler errors. However, the TX unit 200 does not perform any compensation of the modulation timing, but instead sends mast deviation information to the RX unit 300 for the RX unit 300 to correct for position errors.

[0050] Reference is now made to Fig. 3 illustrating a method for mast sway compensated sensing signaling as performed by the TX unit 200 according to an embodiment. The TX unit 200 comprises an antenna unit 225.

[0051] SI 02: The TX unit 200 obtains an indication of mast sway 130 of the antenna unit 225. Different ways for the TX unit 200 to obtains the indication of mast sway 130 of the antenna unit 225 will be disclosed below.

[0052] S104: The TX unit 200 transmits, from the antenna unit 225, a sensing signal in conjunction with initiating compensation for the mast sway 130 at time of transmission of the sensing signal. The sensing signal is destined for the RX unit 300.

[0053] Advantageously, this method and this TX unit 200 can be used to mitigate object sensing range uncertainties and object mobility detection limitations otherwise caused by mast sway effects. In turn, this method and this TX unit 200 therefore provide accurate sensing even in the presence of mast sway.

[0054] Advantageously, this method and this TX unit 200 enable mono-static sensing or bi-static sensing (or even multi-static sensing). In turn, this method and this TX unit 200 therefore require less overhead, thus reducing delays, compared to methods relying on synchronization between the TX unit 200 and the RX unit 300.

[0055] Embodiments relating to further details of mast sway compensated sensing signaling as performed by the TX unit 200 will now be disclosed.

[0056] There may be different ways for the TX unit 200 to initiate the compensation in step SI 04.

[0057] In some aspects, to initiate the compensation involves the TX unit 200 to perform pre-compensation at the TX unit side. Hence, in some embodiments, initiating the compensation comprises pre-compensating the sensing signal in accordance with the mast sway 130, whereby it is the sensing signal as pre-compensated that is transmitted.

[0058] In this respect, the pre-compensating might comprise compensating a carrier phase of the sensing signal in accordance with the mast sway 130. Further aspects of the pre-compensating as performed by the TX unit 200 will be disclosed below.

[0059] In some aspects, to initiate the compensation involves the TX unit 200 to send information of the mast sway 130 to the RX unit 300 for post-compensation to be performed at the RX unit side. Hence, in some embodiments, initiating the compensation comprises transmitting information of the mast sway 130 to the RX unit 300. In this respect, the information might pertain to any, or any combination, of: acceleration of the mast sway 130 per dimension, velocity of the mast sway 130 per dimension, displacement of the mast sway 130 per dimension.

[0060] Further in this respect, there can be different points in time in which the information of the mast sway 130 is sent to the RX unit 300. In general terms, the information might be sent in a time proximity to the TX unit 200 transmitting the sensing signal. Further in this respect, the information can be sent before the transmission of the sensing signal, potentially either including a prediction at the upcoming transmission of the sensing signal or information from which such prediction can be derived. That is, in some embodiments, the information is transmitted before the sensing signal and pertains to a prediction of the mast sway 130 at the time of transmission of the sensing signal. Still further in this respect, the information can be sent after the transmission of the sensing signal, potentially including actual measured antenna data at the TX unit 200. That is, in some embodiments, the information is transmitted after the sensing signal and pertains to the mast sway 130 as measured at the time of transmission of the sensing signal.

[0061] Reference is now made to Fig. 4 illustrating a method for mast sway compensated sensing signaling as performed by the RX unit 300 according to an embodiment. The RX unit 300 comprises an antenna unit 325.

[0062] S202: The RX unit 300 receives, by the antenna unit 325, a sensing signal. The sensing signal originates from the TX unit 200.

[0063] S204: The RX unit 300 obtains an indication of mast sway 140 of the antenna unit 325.

[0064] S206: The RX unit 300 compensates the sensing signal in accordance with the mast sway 140 at time of reception of the sensing signal.

[0065] Advantageously, this method and this RX unit 300 can be used to mitigate object sensing range uncertainties and object mobility detection limitations otherwise caused by mast sway effects. In turn, this method and this RX unit 300 therefore provide accurate sensing even in the presence of mast sway.

[0066] Advantageously, this method and this RX unit 300 enable mono-static sensing or bi-static sensing (or even multi-static sensing). In turn, this method and this RX unit 300 therefore require less overhead, thus reducing delays, compared to methods relying on synchronization between the TX unit 200 and the RX unit 300.

[0067] Embodiments relating to further details of mast sway compensated sensing signaling as performed by the RX unit 300 will now be disclosed. In general terms, the way in which the RX unit 300 compensates the sensing signal might correspond to the way the in which the TX unit 200 pre-compensates the sensing signal. In this respect, to compensate the sensing signal at the RX unit 300 might thus comprise compensating a carrier phase of the sensing signal in accordance with the mast sway 140. Further aspects of the compensating as performed by the RX unit 300 will be disclosed below.

[0068] As disclosed above, the TX unit 200 might send information of the mast sway 130 to the RX unit 300 for post-compensation to be performed at the RX unit side. Therefore, in some embodiments, the RX unit 300 is configured to perform (optional) steps S208 and S210.

[0069] S208: The RX unit 300 receives information of mast sway 130 of an antenna unit 225 used for transmitting the sensing signal from the TX unit 200.

[0070] As disclosed above, the information might pertain to any, or any combination, of: acceleration of the mast sway 130 per dimension, velocity of the mast sway 130 per dimension, displacement of the mast sway 130 per dimension.

[0071] S210: The RX unit 300 post-compensates the sensing signal in accordance with the received information.

[0072] It is here noted that in some aspects where pre-compensation is performed at the TX unit 200 and there is no antenna sway at the RX unit 300, there is neither a need for the TX unit 200 to send any information of the mast sway 130, nor is there a need for the RX unit 300 to perform any compensation on its own. In such scenarios the RX unit 300 (such as in a bi-static sensing or a multi-static sensing scenario) could be a UE. This approach will prevent signaling overhead (especially if e.g., multiple UEs are involved in multistatic sensing) and reduce system delays and latencies that otherwise could result in errors in applied mast sway compensation.

[0073] Further aspects relating to mast sway compensated sensing signaling will be disclosed next. Unless otherwise stated, the mast sway compensation as disclosed below is applicable for both mast sway 130 at the TX unit 200 and mast sway 140 at the RX unit 300, and thus the mast sway compensation can be performed by any of the TX unit 200 and the RX unit 300, as suitable.

[0074] In general terms, the compensation can be based on accelerometer- and / or gyro-data, as obtained by the TX unit 200 and / or the RX unit 300 from the IMU. Further in this respect, the compensation can be performed by one or more integrators. That is, in some embodiments, the pre-compensating as performed by the TX unit 200 is based on: the mast sway 130 as measured at the time of transmission of the sensing signal, the mast sway 130 as measured previous to the time of transmission of the sensing signal, or a prediction of the mast sway 130 at the time of transmission of the sensing signal. Likewise, in some embodiments, the compensating as performed by the RX unit 300 is based on: the mast sway 140 as measured at the time of reception of the sensing signal, the mast sway 140 as measured previous to the time of reception of the sensing signal, or a prediction of the mast sway 140 at the time of reception of the sensing signal. As an example, the acceleration is measured in two dimensions, corresponding to mast acceleration in the horizontal plane. The thus measured 2D acceleration can be converted to velocity by two leaky integrators. The leakage can here be used to ensure that DC offsets, or biases, are not integrated to correspond to large velocities. Since the antenna units 225, 325 are at fixed locations, the average velocity of the mast sway 130, 140 should be equal to zero. Therefore, leakage can be introduced with low loss of information. The velocity can then be converted to deviation, again using leaky integrators. As the leakage in the integrators should be low enough to avoid affecting the result when the mast sway is as slow as 0.4Hz, the transient response when starting the integrators will be slow. To speed up the settling, the steady state result could be sought at start up. Assuming sinusoidal acceleration, zero-crossing of the acceleration waveform are identified. The waveform can then be integrated from the zero-crossing to the next zero-crossing, thus obtaining an integrated value. At that next zero-crossing, the velocity can then be set to half of the integrated value, and the deviation can be set to zero. The operation can then continue from that point. This can be done for the integrators in both directions of the horizontal plane. The leaky integrators will then have states close to the steady state solution and the transient will be short with small errors.

[0075] To find compensation for a given beam direction, the deviation vector is projected on the direction vector (normalized to unit length), using the scalar product (i.e., the dot product). The result is then divided by the carrier signal wavelength and the fractional part is used to rotate the baseband signal to adjust its phase, and in some cases also the dot product result divided by the speed of light is used to delay the baseband signal, depending on whether both velocity through Doppler and position of objects need to be corrected.

[0076] In case no compensation of the sensing signal is made at the TX unit 200, information regarding, for example, the velocity and deviation vectors, can be transmitted by the TX unit 200 to the RX unit 300. It is also possible for the TX unit 200 to correct for one of carrier phase and baseband signal delay, and then transmit correction information to allow the RX unit 300 to correct for the other.

[0077] Reference is next made to Fig. 5 which schematically illustrates deviation and acceleration of a mast in an x-y coordinate system according to embodiments. The location of the mast is indicated at 510. The mast deviation is in a coordinate system with an x-axis and a y-axis, and where the deviation thus is xdev along the x-axis and ydev along the y-axis. Information about the deviation is used to perform the compensation, but what is measured instead is the acceleration, denoted xacc along the x-axis and yacc along the y-axis. That is, in some embodiments, the indication of mast sway 130 as sent from the TX unit 200 to the RX unit 300 pertains to acceleration of the mast sway 130 per dimension. The acceleration can be measured, estimated, or predicted, using an IMU, or the like. Integration can be used to convert the acceleration into deviation. The integration of acceleration overtime yields the velocity. That is, in some embodiments, to pre-compensate the sensing signal at the TX unit 200 involves using the one or more leaky integrators to convert the acceleration of the mast sway 130 per dimension to velocity of the mast sway 130 per dimension. Likewise, in some embodiments, to compensate the received sensing signal at the RX unit 300 involves using the one or more leaky integrators to convert the acceleration of the mast sway 140 per dimension to velocity of the mast sway 140 per dimension. Integration of the velocity over time yields the deviation. That is, in some embodiments, to pre-compensate the sensing signal involves using the one or more leaky integrators to convert the velocity of the mast sway 130 per dimension to displacement of the mast sway 130 per dimension. Likewise, in some embodiments, to compensate the received sensing signal at the RX unit 300 involves using the one or more leaky integrators to convert the velocity of the mast sway 140 per dimension to displacement of the mast sway 140 per dimension. Hence, two integrations over time can be performed to convert the acceleration into deviation. The integrations can be performed separately in each dimension. That is, the value of xdev can be derived from xacc by two integrations, and the value of ydev can be derived from yacc by another two integrations.

[0078] Reference is next made to Fig. 6 which schematically illustrates waveforms 600 for periodic mast sway (for the x-coordinate or the y-coordinate in Fig. 5) according to embodiments. In particular, in Fig. 6 is illustrated a first waveform 610 representing acceleration, a second waveform 620 representing velocity, and a third waveform 630 representing deviation. The waveforms illustrate a steady state situation with a periodic sway. As can be seen in the figure, the first waveform 610 (i.e., the acceleration) is in anti-phase with the third waveform 630 (i.e., the deviation), and the second waveform 620 (i.e., the velocity) is lagging behind by a quarter of a period of the first waveform 610. From this can be concluded that the zero-crossings of the acceleration and the deviation co-inside, and that the velocity is at its amplitude maxima at the acceleration zero-crossings.

[0079] As noted above, there will be a DC offset, or bias, in the accelerometer data, due to imperfections in the sensor and analog electronics, such as amplifiers etc. In general terms, if data that has a DC offset is integrated, this will yield an error that grows linearly with time. Given long enough time, the error will grow without bounds, which may ruin the performance. Rather than correcting for errors due to mast sway, even larger errors could potentially be introduced. Integrators with limited gain below a certain frequency can therefore be used. This means that the pole is moved from its ideal location at zero frequency to a finite frequency far below the frequency of the mast sway, such as at least an order of magnitude below the frequency of the sway. Integrators which have limited DC gain are often referred to as a leaky integrator. Leaky integrators could be used in both signal conversion steps, i.e., when converting from acceleration to velocity, and when converting from velocity to deviation. Therefore, in some embodiments, to pre-compensate the sensing signal at the TX unit 200, and / or to compensate the sensing signal at the RX unit 300, involves using one or more leaky integrators. Using ideal integrators, i.e., with a zero-frequency pole, the memory length is infinite. That is, the integrator will at its output provide an integral of all inputs since the operation started, and old values are not weighted down. In a leaky integrator, old values are weighted down and are thereby eventually “forgotten”, but it can take a comparatively long time if the pole is at low frequency. Errors can therefore result in very long transients. Therefore, to minimize initial errors, a search is made for zero-crossings of the acceleration; if there is substantial DC offset, an estimation of the DC offset is first subtracted. At the acceleration zero-crossings, the deviation is estimated to zero, motivated by Fig. 6. The velocity at the acceleration zero-crossing can be estimated by observing that from one acceleration zero-crossing to the next, the velocity is increased by the time integral of the acceleration between those time instants. The velocity then changes between its maximum and minimum. Assuming these extreme values to be equal in magnitude but opposite in sign, the velocity maximum and minimum magnitude can be evaluated as the half the integral. The velocity (including its sign) at an acceleration zero-crossing can then be estimated as half the time integral of the acceleration from previous zero-crossing to the current zero-crossing. That is, in some embodiments, to pre-compensate the sensing signal at the TX unit 200 comprises identifying a first zero-crossing of a waveform 610 representing the acceleration, integrating the waveform from the first zero-crossing to the next following zero-crossing, at that next following zero-crossing setting the velocity 620 to correspond to half of the integrated value , and setting the displacement 630 to zero. Likewise, in some embodiments, to compensate the received sensing signal at the RX unit 300 comprises identifying a first zero-crossings of a waveform 610 representing the acceleration, integrating the waveform from the first zero-crossing to the next following zero-crossing, at that next following zero-crossing setting the velocity 620 to correspond to half of the integrated value, and setting the displacement 630 to zero. The states of the leaky integrators can then be updated at the acceleration zero-crossing instant, to zero for the deviation integrator, and half the integral value just calculated for the velocity integrator.

[0080] To further minimize transients, if a substantial estimated DC offset at the beginning of the calculation was subtracted, this DC offset multiplied by the DC gain of the integrators can be added to their output state. For the second integrator it will be the cascaded DC gain of the two integrators that is added.

[0081] With the above methods, the integrators can be started with a small and short transient, although the integrators may have a very long memory, and the mast sway compensation can even be quickly started when the mast sway 130, 140 is large.

[0082] Reference is next made to Fig. 7 which schematically illustrates a projection of mast deviation to beams in different directions according to embodiments. In Fig. 7 the mast deviation is indicated by a vector 710. In this example, there are three beams 720a, 720b, 720c. For each beam 720a, 720b, 720c there is a center direction. The mast deviation vector 710 is projected to these center directions, yielding the vectors 730a, 730b, 730c. The length of each vector 730a, 730b, 730c corresponds to the amount of time correction needed for the corresponding beam 720a, 720b, 720c. In particular, in some embodiments, the sensing signal is transmitted in directional beams 720a, 720b, 720c, and the pre-compensating at the TX unit 200 involves individual pre-compensation of the sensing signal per directional beam 720a, 720b, 720c in accordance with the mast sway 130 per beam direction 720a, 720b, 720c. Likewise, in some embodiments, the sensing signal is received in a directional beam 720a: 720c, and to compensate the sensing signal at the RX unit 300 comprises compensation of the sensing signal for the directional beam 720a, 720b, 720c in accordance with the mast sway 140 per beam direction 720a, 720b, 720c. If the vector 730a, 730b, 730c points in the same direction as the beam 720a, 720b, 720c, time should be retarded when performing the compensation for the sensing signal. This is the case when performing compensation for beams 720a and 720c. If the vector 730a, 730b, 730c points in opposite direction, time should instead be advanced when performing the compensation for the sensing signal. This is the case when performing compensation for beam 720b. One way to calculate the projected vector length and sign is to define unit length vectors aligned with the beam center directions, and then calculate the dot product between those vectors and the mast deviation vector 710, yielding the projected distance. By dividing the distance by the speed of light, or into signal periods (phase) by dividing it by the electromagnetic wavelength, this distance can be converted to the time the sensing signal should be retarded, or advanced, when performing the compensation. Hence, in some embodiments, the displacement 630 is represented by a displacement vector 710, and the displacement vector 710 as projected to each directional vector 730a, 730b, 730c and divided by the carrier wavelength yields a carrier phase compensation per directional beam 720a, 720b, 720c.

[0083] After the deviation has been estimated from the acceleration data, the compensation can be performed, either in both the TX unit 200 and the RX unit 300 or in only the RX unit 300. As noted above, the antenna unit 225, 325 may be provided in a TX unit 200 or an RX unit 300.

[0084] In case the antenna unit 325 is provided in an RX unit 300, the RX unit 300 can use the deviation of the mast as a correction to its position in the sensing equations when evaluating positions of objects 110 or correction for its velocity as part of object mobility detection.

[0085] In case the antenna unit 225 is provided in a TX unit 200, the TX unit 200 can inform any RX units 300 about its deviation in position, so the RX units 300 can use this information in their evaluation of positions of objects 110. The TX unit 200 can also inform the RX units 300 about the velocity of the mast sway 130 at the TX unit 200, so the RX units 300 can correctly evaluate object velocities through Doppler measurements. The informing can take place through a direct communication between the TX unit 200 and the RX units 300, or through broadcasting, or indirectly through the TX unit 200 informing the network, which then transmits sensing assisting information to the RX units 300. Alternatively, when transmitting the sensing signal, the TX unit 200 can directly correct its transmission for mast sway 130, so that the RX unit 300 will not have to apply any correction for the TX unit 200. When the transmission occurs in multiple beams 720a, 720b, 720c in different directions, the transmission of the sensing signal in each beam 720a, 720b, 720c should be corrected individually, as disclosed above with reference to Fig. 7. In directions orthogonal to the mast sway 130, 140 no compensation is needed, etc.

[0086] The compensation can be performed in phase and / or time. The correction in phase is to suppress Doppler effects due to shifts in carrier phase as caused by the mast sway 130, 140. The calculations above are then performed, resulting in number of wavelengths each beam should be advanced or retarded. Depending on antenna and / or transceiver architecture, the phase of the baseband signal, a local oscillator signal, or the RF signal can be shifted using corresponding circuitry. The information regarding phase adjustment is in the fractional part in the number of wavelengths of the mast deviation. For instance, if the deviation corresponds to 2.5 signal wavelengths, the phase of the sensing signal should be shifted corresponding to 0.5 periods, equal to 180 degrees. The integer part with 2 full wavelengths does not carry any information regarding the phase shift.

[0087] Compensation could be made for different frequency parts of a transmission bandwidth to adapt to wavelength differences over this bandwidth. As an example, if the deviation is xl meters, and the wavelength varies from lambdal to lambda2 over the bandwidth, a phase compensation of xl / lambdal periods for one part of the bandwidth and xl / lambda2 periods for the other and similar for frequencies (lambda) in-between, the number of compensated frequency bins could scale to adapt to the required performance and dependent on bandwidth and carrier frequency used.

[0088] As an example, for a relative bandwidth of 5% there will be an error of 2.5% at bandwidth edges compared to at the center frequency. That is, at edges it would need to be compensated 2.5% more or less than at the center frequency. If the mast sway 130, 140 is 0.3m this would correspond to an error of + / - 7.5mm at bandwidth edges if not compensated for. If frequency of mast sway is 3Hz there would be a speed amplitude of 2-7I-3-7.5 = 0. 14 m / s = 0.5km / h. That is, a rather small speed error is smeared out around + / - 0.5 km / h and around + / - 7.5mm for positioning in this particular example.

[0089] If the accuracy requirements in position are very high, so that the mast sway amplitude is problematic, to avoid errors in position due to mast sway 130, 140, also time can be compensated for. The baseband modulation signal should then be advanced / delayed individually in each beam 720a, 720b, 720c. The time delay can be calculated as indicated above by dividing the projected deviation distance by the speed of light.

[0090] As disclosed above, it can also be an option to correct only the phase at the TX unit 200, and where the TX unit 200 shares information of the mast deviation with the RX unit 300.

[0091] The herein disclosed embodiments are applicable to general sensing signals and communication signals, and not only radar sensing. For example, the herein disclosed embodiments are applicable to be used for joint communication and sensing (JCAS) applications, distributed multiple-input multiple-output (D- MIMO) communication and sensing, and coherent joint transmission (C-JT) communication and sensing and for positioning.

[0092] Fig. 8 schematically illustrates, in terms of a number of functional units, the components of a TX unit 200 according to an embodiment. Processing circuitry 210 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1210a (as in Fig. 12), e.g. in the form of a storage medium 230. The processing circuitry 210 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA). Particularly, the processing circuitry 210 is configured to cause the TX unit 200 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the TX unit 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 210 is thereby arranged to execute methods as herein disclosed.

[0093] The storage medium 230 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0094] The TX unit 200 may further comprise a communications (comm.) interface 220 for communications with other entities, functions, nodes, units, and devices to perform mast sway compensated sensing signaling in accordance with the herein disclosed embodiments. As such the communications interface 220 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0095] The processing circuitry 210 controls the general operation of the TX unit 200 e.g. by sending data and control signals to the communications interface 220 and the storage medium 230, by receiving data and reports from the communications interface 220, and by retrieving data and instructions from the storage medium 230. Other components, as well as the related functionality, of the TX unit 200 are omitted in order not to obscure the concepts presented herein.

[0096] Fig. 9 schematically illustrates, in terms of a number of functional modules, the components of a TX unit 200 according to an embodiment. The TX unit 200 of Fig. 9 comprises a number of functional modules; an obtain module 210a configured to perform step S 102, and a transmit module 210b configured to perform step S104. The TX unit 200 of Fig. 9 may further comprise a number of optional functional modules, as represented by functional module 210c. In general terms, each functional module 210a:210c may be implemented in hardware or in software. Preferably, one or more or all functional modules 210a: 210c may be implemented by the processing circuitry 210, possibly in cooperation with the communications interface 220 and / or the storage medium 230. The processing circuitry 210 may thus be arranged to from the storage medium 230 fetch instructions as provided by a functional module 210a: 210c and to execute these instructions, thereby performing any steps of the TX unit 200 as disclosed herein.

[0097] Fig. 10 schematically illustrates, in terms of a number of functional units, the components of an RX unit 300 according to an embodiment. Processing circuitry 310 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1210b (as in Fig. 12), e.g. in the form of a storage medium 330. The processing circuitry 310 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA). Particularly, the processing circuitry 310 is configured to cause the RX unit 300 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 330 may store the set of operations, and the processing circuitry 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the RX unit 300 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 310 is thereby arranged to execute methods as herein disclosed.

[0098] The storage medium 330 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0099] The RX unit 300 may further comprise a communications interface 320 for communications with other entities, functions, nodes, units, and devices to perform mast sway compensated sensing signaling in accordance with the herein disclosed embodiments. As such the communications interface 320 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0100] The processing circuitry 310 controls the general operation of the RX unit 300 e.g. by sending data and control signals to the communications interface 320 and the storage medium 330, by receiving data and reports from the communications interface 320, and by retrieving data and instructions from the storage medium 330. Other components, as well as the related functionality, of the RX unit 300 are omitted in order not to obscure the concepts presented herein.

[0101] Fig. 11 schematically illustrates, in terms of a number of functional modules, the components of an RX unit 300 according to an embodiment. The RX unit 300 of Fig. 11 comprises a number of functional modules; a receive module 310a configured to perform step S202, an obtain module 310b configured to perform step S204, and a compensate (Comp.) module 310c configured to perform step S206. The RX unit 300 of Fig. 11 may further comprise a number of optional functional modules, such as any of a receive module 3 lOd configured to perform step S208, and a post-compensate (Post-comp.) module 3 lOe configured to perform step S210. In general terms, each functional module 310a:3 lOe may be implemented in hardware or in software. Preferably, one or more or all functional modules 310a:3 lOe may be implemented by the processing circuitry 310, possibly in cooperation with the communications interface 320 and / or the storage medium 330. The processing circuitry 310 may thus be arranged to from the storage medium 330 fetch instructions as provided by a functional module 310a: 3 lOe and to execute these instructions, thereby performing any steps of the RX unit 300 as disclosed herein.

[0102] The TX unit 200 and / or the RX unit 300 may be provided as a standalone device or as a part of at least one further device. For example, the TX unit 200 and / or RX unit 300 may be provided in a node of a radio access network or in a node of a core network. Alternatively, functionality of the TX unit 200 / RX unit 300 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the radio access network or the core network) or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. A first portion of the instructions performed by the TX unit 200 and / or RX unit 300 may be executed in a respective first device, and a second portion of the instructions performed by the TX unit 200 and / or RX unit 300 may be executed in a respective second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the TX unit 200 and / or RX unit 300 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a TX unit 200 and / or RX unit 300 residing in a cloud computational environment. Therefore, although a single processing circuitry 210, 310 is illustrated in Figs. 8 and 10 the processing circuitry 210, 310 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 210a:210c, 310a:310e of Figs. 9 and 11 and the computer programs 1220a, 1220b ofFig. 12.

[0103] Some (radio) access network architectures define network nodes (or gNBs) comprising multiple component parts or nodes: a central unit (CU), one or more distributed units (DUs), and one or more radio units (RUs). The protocol layer stack of the network node is divided between the CU, the DUs and the RUs, with one or more lower layers of the stack implemented in the RUs, and one or more higher layers of the stack implemented in the CU and / or DUs. The CU is coupled to the DUs via a fronthaul higher layer split (HUS) network; the CU / DUs are connected to the RUs via a fronthaul lower-layer split (UUS) network. The DU may be combined with the CU in some embodiments, where a combined DU / CU may be referred to as a CU or simply a baseband unit. A communication link for communication of user data messages or packets between the RU and the baseband unit, CU, or DU is referred to as a fronthaul network or interface. Messages or packets may be transmitted from the network node in the downlink (i.e., from the CU to the RU) or received by the network node in the uplink (i.e., from the RU to the CU).

[0104] Fig. 12 shows one example of a computer program product 1210a, 1210b comprising computer readable means 1230. On this computer readable means 1230, a computer program 1220a can be stored, which computer program 1220a can cause the processing circuitry 210 and thereto operatively coupled entities and devices, such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. The computer program 1220a and / or computer program product 1210a may thus provide means for performing any steps of the TX unit 200 as herein disclosed. On this computer readable means 1230, a computer program 1220b can be stored, which computer program 1220b can cause the processing circuitry 310 and thereto operatively coupled entities and devices, such as the communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. The computer program 1220b and / or computer program product 1210b may thus provide means for performing any steps of the RX unit 300 as herein disclosed.

[0105] In the example ofFig. 12, the computer program product 1210a, 1210b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1210a, 1210b could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1220a, 1220b is here schematically shown as a track on the depicted optical disk, the computer program 1220a, 1220b can be stored in any way which is suitable for the computer program product 1210a, 1210b.

[0106] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A transmiter unit (200) for mast sway compensated sensing signaling, the transmiter unit (200) comprising processing circuitry (310) and an antenna unit (225), the transmiter unit (200) being configured to: obtain an indication of mast sway (130) of the antenna unit (225); and transmit, from the antenna unit (225), a sensing signal in conjunction with initiating compensation for the mast sway (130) at time of transmission of the sensing signal, the sensing signal being destined for a receiver unit (300).

2. The transmiter unit (200) according to claim 1, wherein initiating the compensation comprises precompensating the sensing signal in accordance with the mast sway (130), whereby it is the sensing signal as pre-compensated that is transmited.

3. The transmiter unit (200) according to claim 2, wherein the pre-compensating comprises compensating a carrier phase of the sensing signal in accordance with the mast sway (130).

4. The transmiter unit (200) according to claim 2 or 3, wherein the pre-compensating is based on: the mast sway (130) as measured at the time of transmission of the sensing signal, the mast sway (130) as measured previous to the time of transmission of the sensing signal, or a prediction of the mast sway (130) at the time of transmission of the sensing signal.

5. The transmiter unit (200) according to any of claims 2 to 4, wherein the sensing signal is transmited in directional beams (720a:720c), and wherein the pre-compensating involves individual precompensation of the sensing signal per directional beam (720a: 720c) in accordance with the mast sway (130) per beam direction (720a:720c).

6. The transmiter unit (200) according to any preceding claim, wherein the indication of mast sway (130) pertains to acceleration (610) of the mast sway (130) per dimension.

7. The transmiter unit (200) according to any of claims 2 to 6, wherein to pre-compensate the sensing signal involves using one or more leaky integrators.

8. The transmiter unit (200) according to a combination of claim 6 and claim 7, wherein to precompensate the sensing signal involves using the one or more leaky integrators to convert the acceleration (610) of the mast sway (130) per dimension to velocity (620) of the mast sway (130) per dimension.

9. The transmiter unit (200) according to claim 8, wherein to pre-compensate the sensing signal involves using the one or more leaky integrators to convert the velocity (620) of the mast sway (130) per dimension to displacement (630) of the mast sway (130) per dimension.

10. The transmiter unit (200) according to claim 9, wherein to pre-compensate the sensing signal comprises identifying a first zero-crossing of a waveform representing the acceleration (610), integrating the waveform from the first zero-crossing to a next following zero-crossing, at said next following zerocrossing seting the velocity (620) to correspond to half of the integrated value, and seting the displacement (630) to zero.

11. The transmiter unit (200) according to claim 10, wherein the sensing signal is transmited using a carrier wavelength, wherein each directional beam (720a:720c) is represented by a directional vector (730a:730c), wherein the displacement (630) is represented by a displacement vector (710), and wherein the displacement vector (710) as projected to each directional vector (730a:730c) and divided by the carrier wavelength yields a carrier phase compensation per directional beam (720a:720c).

12. The transmiter unit (200) according to claim 1, wherein initiating the compensation comprises transmiting information of the mast sway (130) to the receiver unit (300).

13. The transmiter unit (200) according to claim 12, wherein the information pertains to any of: acceleration (610) of the mast sway (130) per dimension, velocity (620) of the mast sway (130) per dimension, displacement (630) of the mast sway (130) per dimension.

14. The transmiter unit (200) according to claim 12 or 13, wherein the information of the mast sway (130) is transmited in a time proximity to transmiting the sensing signal.

15. The transmiter unit (200) according to claim 14, wherein the information is transmited before the sensing signal and pertains to a prediction of the mast sway (130) at the time of transmission of the sensing signal.

16. The transmiter unit (200) according to claim 14, wherein the information is transmited after the sensing signal and pertains to the mast sway (130) as measured at the time of transmission of the sensing signal.

17. A receiver unit (300) for mast sway compensated sensing signaling, the receiver unit (300) comprising processing circuitry (210) and an antenna unit (325), the receiver unit (300) being configured to: receive, by the antenna unit (325), a sensing signal, the sensing signal originating from a transmiter unit (200); obtain an indication of mast sway (140) of the antenna unit (325); and compensate the sensing signal in accordance with the mast sway (140) at time of reception of the sensing signal.

18. The receiver unit (300) according to claim 17, wherein to compensate the sensing signal comprises compensating a carrier phase of the sensing signal in accordance with the mast sway (140).

19. The receiver unit (300) according to claim 17 or 18, wherein the sensing signal is received in a directional beam (720a: 720c), and wherein to compensate the sensing signal comprises compensation of the sensing signal for the directional beam (720a:720c) in accordance with the mast sway (140) per beam direction.

20. The receiver unit (300) according to any of claims 17 to 19, the receiver unit (300) further being configured to: receive information of mast sway (130) of an antenna unit (225) used for transmitting the sensing signal from the transmitter unit (200); and post-compensate the sensing signal in accordance with the received information.

21. The receiver unit (300) according to claim 20, wherein the information pertains to any of: acceleration (610) of the mast sway (130) per dimension, velocity (620) of the mast sway (130) per dimension, displacement (630) of the mast sway (130) per dimension.

22. A system for mast sway compensated sensing signaling, the system comprising a transmitter unit (200) according to any of claims 1 to 16 and a receiver unit (300) according to any of claims 17 to 21.

23. The system according to claim 22, wherein the transmitter unit (200) and the receiver unit (300) are configured for bi-static or multi-static sensing.

24. The system according to claim 22, wherein the transmitter unit (200) and the receiver unit (300) are configured for mono-static sensing.

25. A method for mast sway compensated sensing signaling, the method being performed by a transmitter unit (200) comprising an antenna unit (225), the method comprising: obtaining (S102) an indication of mast sway (130) of the antenna unit (225); and transmitting (SI 04), from the antenna unit (225), a sensing signal in conjunction with initiating compensation for the mast sway (130) at time of transmission of the sensing signal, the sensing signal being destined for a receiver unit (300).

26. A method for mast sway compensated sensing signaling, the method being performed by a receiver unit (300) comprising an antenna unit (325), the method comprising: receiving (S202), by the antenna unit (325), a sensing signal, the sensing signal originating from a transmitter unit (200);obtaining (S204) an indication of mast sway (140) of the antenna unit (325); and compensating (S206) the sensing signal in accordance with the mast sway (140) at time of reception of the sensing signal.

27. A computer program (1220a) for mast sway compensated sensing signaling, the computer program comprising computer code which, when run on processing circuitry (210) of a transmitter unit (200) comprising an antenna unit (225), causes the transmitter unit (200) to: obtain (S102) an indication of mast sway (130) of the antenna unit (225); and transmit (S104), from the antenna unit (225), a sensing signal in conjunction with initiating compensation for the mast sway (130) at time of transmission of the sensing signal, the sensing signal being destined for a receiver unit (300).

28. A computer program (1220b) for mast sway compensated sensing signaling, the computer program comprising computer code which, when run on processing circuitry (310) of a receiver unit (300) comprising an antenna unit (325), causes the receiver unit (300) to: receive (S202), by the antenna unit (325), a sensing signal, the sensing signal originating from a transmitter unit (200); obtain (S204) an indication of mast sway (140) of the antenna unit (325); and compensate (S206) the sensing signal in accordance with the mast sway (140) at time of reception of the sensing signal.

29. A computer program product (1210a, 1210b) comprising a computer program (1220a, 1220b) according to at least one of claims 27 and 28, and a computer readable storage medium (1230) on which the computer program is stored.

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