Abstract
A method for dedicated short-range communication, DSRC, of an on-board unit, OBU, with at least two beacons, each beacon using a different channel for transmitting a respective carrier signal, comprises: receiving a receive signal comprising the carrier signals of the beacons; downconverting the receive signal to obtain a downconverted signal; filtering all of said different channels out of the downconverted signal to obtain a filtered signal; modulating an OBU response onto the filtered signal to obtain a response signal; upconverting the response signal to obtain an upconverted signal; and transmitting the upconverted signal to the beacons. An OBU is configured to carry out a DSRC with at least two beacons.
Claims
1. A method for dedicated short-range communication, DSRC, of an on-board unit, OBU, with at least two beacons, the OBU being mounted on a vehicle passing the beacons on a road and each beacon using a different channel for transmitting a respective carrier signal, the method comprising the following steps carried out in the OBU: receiving, by an input antenna, a receive signal comprising the carrier signals of the at least two beacons; downconverting, by an input converter, the receive signal to obtain a downconverted signal; filtering, by an input filter, all of said different channels out of the downconverted signal to obtain a filtered signal; modulating, by a modulator, an OBU response onto the filtered signal to obtain a response signal; upconverting, by an output converter, the response signal to obtain an upconverted signal; and transmitting, by an output antenna, the upconverted signal to the at least two beacons.
2. The method according to claim 1, wherein, in said step of downconverting, the receive signal is downconverted to baseband to obtain the downconverted signal, and wherein, in said step of filtering, the downconverted signal is low-pass filtered by blocking frequencies above a cut-off frequency lying substantially at the highest frequency of said different channels in the downconverted signal.
3. The method according to claim 1, wherein, in said step of downconverting, the receive signal is downconverted to intermediate band to obtain the downconverted signal, and wherein, in said step of filtering, the downconverted signal is band-pass filtered by blocking frequencies below a lower cut-off frequency lying substantially at the lowest frequency of said different channels in the downconverted signal as well as frequencies above an upper cut-off frequency lying substantially at the highest frequency of said different channels in the downconverted signal.
4. The method according to claim 2, wherein at least two of said different channels are separated by a guard band that is blocked in said step of filtering.
5. The method according to claim 3, wherein at least two of said different channels are separated by a guard band that is blocked in said step of filtering.
6. The method according to claim 1, further comprising, after said step of modulating, a further step of filtering, by an output filter, all of said different channels out of the response or upconverted signal.
7. The method according to claim 1, wherein at least one of the steps of downconverting, filtering, modulating, further filtering and upconverting is processed digitally, and wherein the method comprises the step of analogue-to-digital-converting the respective one of the receive, downconverted, filtered and response signals, and the step of digital-to-analogue-converting the respective one of the downconverted, filtered, response, and upconverted signals.
8. The method according to claim 1, wherein either said steps of downconverting and filtering or said steps of modulating and upconverting or both said steps of downconverting and filtering and said steps of modulating and upconverting are carried out in respective in-phase, I, and quadrature, Q paths on I and Q components of the respective signal.
9. The method according to claim 1, wherein said DSRC-communication is performed according to a time division duplex, TDD, scheme, and the method further comprises, prior to said step of transmitting, determining, whether the OBU is allowed to transmit, and only if so, carrying out said step of transmitting.
10. The method according to claim 1, wherein the different channels each have a channel bandwidth in a range from 0.1 MHz to 50 MHz.
11. The method according to claim 1, wherein the different channels each have a channel bandwidth in a range from 1 MHz to 12 MHz.
12. The method according to claim 1, wherein the different channels each have a channel bandwidth in a range from 4 MHz to 9 MHz.
13. An on-board unit, OBU, for dedicated short-range communication, DSRC, with at least two beacons each of which uses a different channel for transmitting a respective carrier signal, the OBU comprising: an input antenna configured to receive a receive signal comprising the carrier signals of the at least two beacons; an input converter configured to downconvert the receive signal to obtain a downconverted signal; an input filter configured to filter all of said different channels out of the downconverted signal to obtain a filtered signal; a modulator configured to modulate an OBU response onto the filtered signal to obtain a response signal; an output converter configured to upconvert the response signal to obtain an upconverted signal; and an output antenna configured to transmit the upconverted signal to the at least two beacons.
14. The OBU according to claim 13, wherein the input converter is configured to downconvert the receive signal to baseband to obtain the downconverted signal, and wherein the input filter, for said filtering, comprises a low-pass filter having a cut-off frequency lying substantially at the highest frequency of said different channels in the downconverted signal.
15. The OBU according to claim 13, wherein the input converter is configured to downconvert the receive signal to intermediate band to obtain the downconverted signal, wherein the input filter, for said filtering, comprises a band-pass filter having a lower cut-off frequency lying substantially at the lowest frequency of said different channels in the downconverted signal and an upper cut-off frequency lying substantially at the highest frequency of said different channels in the downconverted signal.
16. The OBU according to claim 13, further comprising an output filter interposed between the modulator and the output antenna and configured to filter all of said different channels out of the response or upconverted signal.
17. The OBU according to claim 13, comprising a software defined radio, SDR, containing at least one of the input converter, the input filter, the modulator, the output filter, and the output converter, for digitally processing the respective signal/s, and an analogue-to-digital converter and a digital-to-analogue converter configured to convert the respective signals prior to and after digital processing, respectively.
18. The OBU according to claim 13, wherein either the input converter and the input filter, on the one hand, or the modulator and the output converter, on the other hand, or both the input converter, the input filter, the modulator and the output converter each comprise an in-phase, I, path and a quadrature, Q, path.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The disclosed subject matter will now be described by means of exemplary embodiments thereof with reference to the enclosed drawings, in which show:
[0034] FIG. 1 an on-board unit (OBU) according to the disclosed subject matter, which is mounted on a vehicle passing three beacons on a road and performing a dedicated short-range communication (DSRC) with the three beacons, in a schematic top view;
[0035] FIG. 2 a first embodiment of the OBU of FIG. 1, in a schematic circuit diagram;
[0036] FIG. 3 an exemplary receive signal received by an input antenna of the OBU of FIGS. 1 and 2, in an amplitude-frequency diagram;
[0037] FIG. 4 a downconverted signal obtained by an input converter of the OBU of FIGS. 1 and 2 from the receive signal of FIG. 3, in an amplitude-frequency diagram;
[0038] FIG. 5 a filtered signal obtained by an input filter of the OBU of FIGS. 1 and 2 from the downconverted signal of FIG. 4, in an amplitude-frequency diagram;
[0039] FIG. 6 a response signal obtained by a modulator of the OBU of FIGS. 1 and 2 from the filtered signal of FIG. 5, in an amplitude-frequency diagram;
[0040] FIG. 7 an upconverted signal obtained by an output converter of the OBU of FIGS. 1 and 2 from the response signal of FIG. 6 and as transmitted by an output antenna of the OBU of FIGS. 1 and 2, in an amplitude-frequency diagram;
[0041] FIG. 8 a second embodiment of the OBU of FIG. 1, in a schematic circuit diagram;
[0042] FIG. 9 a filtered signal obtained by an input filter of the OBU of FIG. 8 from the receive signal of FIG. 3, in an amplitude-frequency diagram;
[0043] FIG. 10 a third embodiment of the OBU of FIG. 1, in a schematic circuit diagram; and
[0044] FIG. 11 a method according to the disclosed subject matter as carried out by the OBU of FIGS. 1, 7 and 9, respectively, in a flow diagram.
DETAILED DESCRIPTION
[0045] FIG. 1 shows an on-board unit (OBU) 1 that is mounted on a vehicle 2 driving on a road 3 which has three lanes 4-6. The OBU 1 communicates, by means of a dedicated short-range communication (DSRC) according to a DSRC standard such as CEN DSR, ETSI EN 300 674-2-1, IEEE 802.11p, ARIB STD-T75, etc., with two or more (here: three) beacons 7.sub.1-7.sub.3 that are located at the road 3 (here: above the lanes 4-6) and passed by the vehicle 2, e.g., to identify, survey, toll, or guide the vehicle 2. To this end, each beacon 7.sub.1-7.sub.3 transmits a respective carrier signal 8.sub.1-8.sub.3 in a different channel 9.sub.1-9.sub.3 (FIG. 3) and in a respective coverage area C.sub.1, C.sub.2, C.sub.3, wherein the coverage areas C.sub.1-C.sub.3 of the beacons 7.sub.1-7.sub.3 optionally overlap. It is understood that the signals transmitted by the beacons 7.sub.1-7.sub.3 may also carry information modulated onto the carrier signals 8.sub.1-8.sub.3. Upon receiving the carrier signals 8.sub.1-8.sub.3 the OBU 1 answers thereto, either once or repeatedly, and either instantly or in a time-delayed manner, e.g., according to a time-division duplex (TDD) scheme.
[0046] During the passage of the vehicle 1, the communication connection to the beacons 7.sub.1-7.sub.3 may change and even be interrupted for one or more of the beacons 7.sub.1-7.sub.3, e.g., due to an interference with other DSRC or non-DSRC signals of other devices such as another OBU 10 mounted on another vehicle 11, a smartphone, etc., due to signal reflections, etc. Hence, the OBU 1 answers in all the channels 9.sub.1-9.sub.3 in order to communicate with as many of the beacons 7.sub.1-7.sub.3 as possible for including at least that one the beacons 7.sub.1-7.sub.3 that has the strongest communication connection at the moment of answering.
[0047] An exemplary answering shall be described with reference to FIGS. 2-7, FIG. 2 depicting a first exemplary embodiment of the OBU 1 and FIGS. 3-7 respective signals processed by the OBU 1.
[0048] The OBU 1 in the example of FIG. 2 comprises an input antenna 12 which receives a receive signal 13 shown in FIG. 3. The receive signal 13 comprises the carrier signals 8.sub.1-8.sub.3 of at least two (here: of all three) of the beacons 7.sub.1-7.sub.3 in the respective channels 9.sub.1-9.sub.3 at radio-frequency f.sub.RF. The bandwidth BW of each channel 9.sub.1-9.sub.3 may be in any range according to a DSRC standard, e.g., in a range from 0.1 MHz to 50 MHz, in particular from 1 MHz to 12 MHz, e.g. from 4 MHz to 9 MHz, e.g., about 5 MHz. In addition to the desired channels 9.sub.1-9.sub.3, the receive signal 13 comprises unwanted signal components 14 caused by non-desirable DSRC or non-DSRC communications.
[0049] The receive signal 13 is downconverted by an input converter 15 of the OBU 1 to obtain a downconverted signal 16 shown in FIG. 4. The exemplary input converter 15 of FIG. 2 converts the receive signal 13 down to baseband by mixing the receive signal 13 with a cosine mixing signal cos(2.Math.f.sub.L,RF.Math.t), wherein f.sub.L,RF denotes the lowest frequency of the channels 9.sub.1-9.sub.3 at radio-frequency. In alternative embodiments, other mixing signals may be used.
[0050] An input filter 17 of the OBU 1 filters all of the different channels 9.sub.1-9.sub.3 out of the downconverted signal 16 for further use to obtain the filtered signal 18 shown in FIG. 5. Hence, the input filter 17 lets pass (filters out) only the desired channels 9.sub.1-9.sub.3 used for DSRC and blocks the non-desirable channels and frequencies, e.g., of the non-desirable signal components 14. To this end, the exemplary input filter 17 of FIG. 2 is a low-pass filter and has a cut-off frequency f.sub.C which lies substantially at the highest frequency f.sub.H,BB of the different channels 9.sub.1-9.sub.3 in the downconverted signal 16, in FIG. 5: in baseband. In this context substantially at the highest frequency f.sub.H,BB includes minor deviations from the highest frequency f.sub.H,BB, e.g., in the range of five or ten percent, keeping the input filter 17 narrowbanded while blocking the non-desirable signal components 14 to a large extent. In alternative embodiments, other filter transfer functions may be used, e.g., as described below with reference to FIGS. 8 and 9.
[0051] Downstream of the input filter 17, the OBU 1 comprises a modulator 19 which modulates an OBU response 20 onto the filtered signal 18 to obtain a response signal 21 shown in FIG. 6. The OBU response 20 may include any information used for vehicle identification, surveillance, tolling, routing, etc. and may be modulated onto the filtered signal 18 using any modulation, e.g., an amplitude modulation, a frequency modulation, a phase modulation, in particular a phase shift keying like a binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK).
[0052] The OBU 1 further comprises an output converter 22 which converts the response signal 21 up to radio-frequency f.sub.RF to obtain an upconverted signal 23 shown in FIG. 7. The exemplary output converter 23 of FIG. 2 converts the response signal 21 up by mixing the response signal 21 with a cosine mixing signal cos(2.Math.f.sub.L,RF.Math.t), wherein f.sub.L,RF again denotes the lowest frequency of the channels 9.sub.1-9.sub.3 at radio frequency f.sub.RF (FIG. 3). In alternative embodiments, other mixing signals may be used, e.g., as described below with reference to FIGS. 8 and 9.
[0053] The upconverted signal 23 may optionally be amplified as indicated by the signal amplitudes of FIGS. 6 and 7 by an amplifier (not shown), optionally be filtered by a high-pass filter to eliminate mirror frequencies (not shown), and is finally transmitted by an output antenna 24 of the OBU 1 towards the beacons 7.sub.1-7.sub.3. As the upconverted signal 23 includes the OBU response 20 in all of the channels 7.sub.1-7.sub.3, a subsequent reception of the transmitted upconverted signal 23 at one of the beacons 7.sub.1-7.sub.3, e.g. at the one with the strongest communication channel at the transmission time, suffices to successfully communicate the OBU response 20 to the beacons 7.sub.1-7.sub.3.
[0054] As indicated by the dashed lines in in FIG. 2, the OBU 1 optionally comprises a detector 25 for detecting the filtered signal 18, and/or a switch 26 for initiating signal transmission. For instance, when a TDD scheme is applied, the beacons 7.sub.1-7.sub.3 may synchronise the OBU 1 by means of predetermined signals. In one example, the beacons 7.sub.1-7.sub.3 transmit signals carrying information modulated onto the carriers 8.sub.1-8.sub.3 at even TDD frames and only the carriers 8.sub.1-8.sub.3 at odd TDD frames. Hence, when the detector 19 detects the carriers 8.sub.1-8.sub.3 only, it may close the switch 26 as indicated by actuation arrow 27 to initiate the modulating, upconverting and transmitting. In another example, the beacons 7.sub.1-7.sub.3 transmit the carriers 8.sub.1-8.sub.3 at even TDD frames and are silent at odd TDD frames. Hence, the detector 25 may close the switch 26 when it detects no carriers 8.sub.1-8.sub.3 in the filtered signal 18. In still other embodiments, the detector 25 is not present, e.g., when the switch 26 is actuated by a system clock (not shown) synchronising the TDD frames, when no TDD scheme is used and when no switching for transmitting is used, etc.
[0055] With reference to FIGS. 8 and 9, an exemplary second embodiment of the OBU 1 utilising an alternative antenna setup, an intermediate band processing, and an output filtering shall now be described.
[0056] The OBU 1 in the example of FIG. 8 utilises one and the same antenna 28 as input and output antenna 12, 24. The switching between receiving (input antenna 12) and transmitting (output antenna 24) is carried out by a further switch 29 which is actuated as indicated by actuation arrow 30, e.g., similar to the switch 26 of FIG. 2 by the optional detector 25 or a system clock (not shown). The switch 26 and the further switch 29 may each be embodied as any switch or direction control known in the art, e.g., as a (switching) circulator, a PIN diode switch, a field effect transistor switch etc.
[0057] The OBU 1 shown in FIG. 8 processes the respective signals in intermediate band. Hence, the input converter 15 of the OBU 1 of FIG. 8 converts the receive signal 13 down to intermediate band to obtain the downconverted signal 16 shown in FIG. 9, e.g., by mixing the receive signal 13 with a suitable cosine mixing signal cos(2.Math.f.Math.t). The input filter 17 of the OBU 1 of FIG. 8 is a bandpass filter the lower cut-off frequency f.sub.C,L of which lies substantially at the lowest frequency f.sub.L,IB of the different channels 9.sub.1-9.sub.3 in the downconverted signal 16, i.e. in intermediate band f.sub.IB, and whose upper cut-off frequency f.sub.C,U lies substantially at that highest frequency f.sub.H,IB of the different channels 9.sub.1-9.sub.3 in the downconverted signal 16, i.e. in intermediate band f.sub.IB (FIG. 9). As in the example of FIG. 2, the term substantially includes a deviation of about five or ten percent. Thus, the input filter 17 of FIG. 8 blocks the unwanted signal components 14 below as well as above the channels 9.sub.1-9.sub.3 shown in FIG. 9 to obtain the filtered signal 18, and, in case the channels 9.sub.1-9.sub.3 are separated by guard bands (not shown), optionally also the guard bands.
[0058] Thereafter, the modulator 19 of the OBU 1 in the example of FIG. 8 modulates the OBU response 20 onto the filtered signal 16 in intermediate band f.sub.IB to obtain the response signal 21 in intermediate band f.sub.IB, and the output converter 22 of the OBU 1 converts the response signal 21 from intermediate band f.sub.IB up to radio frequency f.sub.RF to obtain the upconverted signal 23.
[0059] In the example of FIG. 8, the OBU 1 further comprises an optional output filter 31 which is interposed between the modulator 19 and the output antenna 24, 28, i.e. between the modulator 19 and the output converter 22 (FIG. 8) or between the output converter 22 and the output antenna 24, 28 (not shown). The output filter 31, similar to the input filter 17, filters all of the channels 9.sub.1-9.sub.3 out of the response signal 21 or the upconverted signal 23 (not shown).
[0060] With reference to FIG. 10 an exemplary third embodiment of the OBU 1 utilising digital signal processing and an I-/Q-modulation scheme shall be described below.
[0061] The OBU 1 in the example of FIG. 10 provides an in phase path (I path) and a quadrature path (Q path) for I and Q components of the respective signals. The input converter 15 has I- and Q-input converters 15.sub.I, 15.sub.Q mixing the receive signal 13 with phase-offset mixing signals cos(2.Math.f.sub.L,RF.Math.t) and sin(2.Math.f.sub.L,RF.Math.t) to obtain respective I- and Q-components of the downconverted signal 16 (here: at baseband, alternatively: at intermediate band as described above). The input filter 17 has I- and Q-input filters 17.sub.I, 17.sub.Q filtering the respective I- and Q-component of the downconverted signal 16 to obtain respective I- and Q-components of the filtered signal 18. The modulator 19 has I- and Q-modulators 19.sub.I, 19.sub.Q modulating the OBU response 20 onto the respective I- and Q-component of the filtered signal 18 to obtain respective I- and Q-components of the response signal 21. The optional output filter 31 has I- and Q-output filters 31.sub.I, 31.sub.Q filtering all of the channels 9.sub.1-9.sub.3 out of the respective I- and Q-component of the response signal 21. And the output converter 22 has I- and Q-output converters 22.sub.I, 22.sub.Q mixing the respective component of the response signal 21 with phase-offset mixing signals cos(2.Math.f.sub.L,RF.Math.t) and sin(2.Math.f.sub.L,RF.Math.t) to obtain respective I and Q-components of the upconverted signal 23 which are added and transmitted by the output antenna 24, 28 towards the beacons 7.sub.1-7.sub.3. The I- and Q-components may be used to convey both amplitude and phase information, or to cancel mirror frequencies (not shown in FIGS. 3 to 7 and 9) in a single sideband (SSB) scheme.
[0062] In the example of FIG. 10, the OBU 1 carries out the modulation and the detection digitally, which is optional. To this end, the OBU 1 has an analogue-to-digital converter (ADC) 32 converting the filtered signal 18 (here: the I- and Q-components thereof) from analogue to digital, a software defined radio (SDR) 33 which embodies the modulator 19 and the detector 25 digitally, e.g., by means of a processor, and a digital-to-analogue (DAC) converter converting the response signal 23 (here: the I- and Q-components thereof) from digital back to analogue. Alternatively, any other combination of the input converter 15, the input filter 17, the detector 25 (if present), the modulator 19, the output filter 31 (if present) and the output converter 22 may be embodied digitally by the SDR 33, as long as the ADC 32 is arranged upstream the SDR 33 and the DAC 34 is arranged downstream the SDR 33 to convert the respective signals, prior to and after digital processing.
[0063] FIG. 11 illustrates a method 35 for DSCR between the OBU 1 and the at least two beacons 7.sub.1-7.sub.3. The method 35 may be carried out by the OBU 1 and may utilise any of the above-mentioned embodiments and variants of the OBU 1 and/or the above-mentioned functions in corresponding method steps.
[0064] In an antecedent step 36, which may or may not be part of the method 35, each of the at least two beacons 7.sub.1-7.sub.3 transmits a respective carrier signal 8.sub.1-8.sub.3 in a different channel 9.sub.1-9.sub.3. Each of the channels 9.sub.1-9.sub.3 may optionally have a bandwidth BW (FIG. 3) in a range from 0.1 MHz to 50 MHz, particularly from 1 MHz to 12 MHz, e.g., from 4 MHz to 9 MHz, optionally about 5 MHz.
[0065] In a first step 37 of the method 35, the receive signal 13 comprising the carrier signals 8.sub.1-8.sub.3 of at the least two beacons 7.sub.1-7.sub.3 is received by the input antenna 12, e.g., as described above with reference to FIGS. 2, 3 and 8.
[0066] In a second step 38 of the method 35, the receive signal 13 is downconverted by the input converter 15 to obtain the downconverted signal 16, e.g., as described above with reference to FIGS. 2, 4, 8 and 9.
[0067] In a third step 39 of the method 35, all of the channels 9.sub.1-9.sub.3 are filtered out of the downconverted signal 16 by the input filter 17 for further use to obtain the filtered signal 18, e.g., as described above with reference to FIGS. 2, 5, 8, 9 and 10. When the receive signal 13 has been downconverted to baseband in step 38 of downconverting, the downconverted signal 16 may be low-pass filtered by blocking frequencies above the cut-off frequency f.sub.C which lies substantially at the highest frequency f.sub.H,BB of the channels 9.sub.1-9.sub.3 (FIGS. 4 and 5). When the receive signal 13 has been downconverted to intermediate band in step 38 of downconverting, the downconverted signal 16 may be band-pass filtered by blocking frequencies below the lower cut-off frequency f.sub.C,L which lies substantially at the lowest frequency f.sub.L,IB of the channels 9.sub.1-9.sub.3 as well as frequencies above the upper cut-off frequency f.sub.C,U which lies substantially at the highest frequency f.sub.H,IB of the channels 9.sub.1-9.sub.3 (FIG. 9). When the channels 9.sub.1-9.sub.3 are separated by one or more guard bands, these guard band/s may optionally be blocked as well.
[0068] In a fourth step 40 of the method 35, the OBU response 20 is modulated onto the filtered signal 18 by the modulator 19 to obtain the response signal 21, e.g., as described above with reference to FIGS. 2, 6, 8 and 10.
[0069] In a sixth step 41 of the method 35, the response signal 21 is upconverted by the output converter 22 to obtain the upconverted signal 23, e.g., as described above with reference to FIGS. 2, 7, 8 and 10.
[0070] In a seventh step 42 of the method 35, the upconverted signal 23 is transmitted by the output antenna 24 to the beacons 7.sub.1-7.sub.3, e.g., as described above with reference to FIGS. 2, 7, 8 and 10, such that it shall be received by at least one of the beacons 7.sub.1-7.sub.3.
[0071] After said step 40 of modulating, the channels 9.sub.1-9.sub.3 may be filtered out from the response signal 21 or the upconverted signal 23 by the output filter 31 in an optional further filtering step 43, e.g., as described above with reference to FIG. 8 or 9.
[0072] As indicated by the optional steps 44 of analogue-to-digital converting (here: of the downconverted signal 16) and digital-to-analogue converting 45 (here: of the response signal 40), any combination of the steps 38-42 (and 43, if performed) may optionally be carried out digitally, e.g., in the SDR 33. Thereby, step 44 precedes and step 45 follows the step/s carried out digitally, e.g., as described above with reference to FIG. 10.
[0073] When the DSRC is optionally performed according to a TDD scheme, the method 35 may further comprise an optional step 46 of determining, whether the OBU 1 is allowed to transmit according to the TDD scheme, e.g., as explained above with reference to the switches 26 and 29 in FIGS. 2 and 8. Then, step 42 of transmitting is only carried out, when it has been determined that the OBU 1 is allowed to transmit. Step 46 of determining is carried out prior to the step 42 of transmitting, e.g., directly before step 42 of transmitting, directly before step 40 of modulating.
[0074] In an optional embodiment of the method 35, steps 38, 39 of downconverting and filtering and/or the steps 40, 41 of modulating and upconverting are carried out in respective in-phase (I) and quadrature (Q) paths on I and Q components of the respective signal, e.g., as described above with reference to FIG. 10.
[0075] The disclosed subject matter is not restricted to the specific embodiments disclosed herein, but encompasses all variants, modifications and combinations thereof that fall within the scope of the appended claims, in particular combinations of the exemplary embodiments of the OBU 1 of FIGS. 2, 8 and 10.
