WO2019141433A1

WO2019141433A1 - Methods of determining the mode of estimation of data received and of toggling of reception, corresponding computer program product, estimation device and terminal

Info

Publication number: WO2019141433A1
Application number: PCT/EP2018/083877
Authority: WO
Inventors: Jean-Roger Roy
Original assignee: Tdf
Priority date: 2018-01-19
Filing date: 2018-12-06
Publication date: 2019-07-25
Also published as: FR3077173B1; FR3077173A1

Abstract

The invention relates to a method of determining the mode of estimation of data received by a system comprising at least two radiofrequency receivers the method comprising the following steps: obtaining (E300) of a planning information item representative of a use over time of first and second carrier frequencies for a radio broadcasting of the data, the first and second carrier frequencies being distinct; determination (E310) of the mode of estimation of the data received as a function of the planning information item, the determination step taking into account a decision to recombine or not recombine first and second signals transposed to baseband delivered by the two radiofrequency receivers tuned respectively to the first and second carrier frequencies, the decision to recombine or not recombine being made on the basis of the planning information item.

Description

Methods of determining received data reception and reception failover mode, computer program product, estimating device and corresponding terminal.

1 TECHNICAL FIELD

The field of the invention is that of reception systems comprising at least two radio frequency receivers that can be tuned to two different carrier frequencies.

More specifically, the invention relates to a method for determining the estimation mode of the data received by such a system when the data in question are broadcast on different distinct carrier frequencies, as well as a flexible reception switching method, for example during the switching the broadcast of the data in question from a first carrier frequency to a second carrier frequency, the data in question being simultaneously broadcast on the first and second carrier frequencies during at least one time recovery period.

The invention finds particular applications in the field of long-range radio broadcasting based on the use of carrier frequencies in the shortwave range (for example DRM broadcasting, for "Digital Radio Mondiale" in English), different frequencies carriers of this range that can be used at different times of the day depending on atmospheric conditions of propagation.

2 TECHNOLOGICAL BACKGROUND

The diffusion based on the use of short waves, ie electromagnetic waves having carrier frequencies in the range of 3 to 30 MHz, makes it possible to reach more or less distant areas on the surface of the globe according to the mode of propagation considered for such waves.

More particularly, there are classically three types of litters that can be reached for such waves: Local range: The propagation is carried out by ground wave and the radius of coverage obtained is of the order of a few tens of kilometers to a hundred kilometers;

Average range: The propagation is then ionospheric and the radius of coverage obtained is of the order of a few hundred to a thousand kilometers;

Extended range: The propagation is also ionospheric and the coverage radius extends beyond a thousand kilometers in multiple jumps.

It thus appears that long coverage ranges are obtained via ionospheric propagation of short waves, and in particular via reflection of such short waves on the ionosphere.

However, the characteristics of the ionosphere remain correlated with the solar activity index. The latter has a major impact on the degree of ionization of the ionosphere layers that participate in the absorption or reflection of signals at varying altitudes.

It thus appears that certain frequencies are more adapted than others to reach a given coverage area via such ionospheric reflection from a shortwave broadcasting site depending on the time of day, the season, the geographical location, etc.

It is thus known in the short wave broadcasting networks to plan the use over time of different frequencies for broadcasting data to a particular coverage area.

More particularly, networks of the SMFN type (for "Synchronized Multi-Frequency Networks" in English) provide time-lapse zones during which two carrier frequencies f 1 and f 2 must succeed each other at the same time for the dissemination of the same data as illustrated in FIG. Figure la. A broadcast site of such a network is for example equipped with two radio transmitters as shown in Figure lb. A first radio transmitter 120fl transmits the data broadcast on the carrier frequency f1 and a second Radio transmitter 120f2 transmits the same data on the carrier frequency f2, to the same coverage area in which a reception system 150 is located.

The reception system 150 implements a known architecture for reception in such a broadcast configuration. Such an architecture is for example based on the use of two reception voices as shown in FIG. In the case where the reception system 150 is located in a diffusion zone covered by the first f1 and second f2 carrier frequencies, for example shortwave, such an architecture allows simultaneous reception of the two radiofrequency signals broadcast on the frequencies. fl and f2. More precisely, the splitter 102 makes it possible to switch one of these two received signals, for example the one centered on fl, on a first radio frequency receiver RX1, and the second of these two received signals, for example the one centered on f2, on a second radio frequency receiver RX2. Each of these two radio frequency receivers then delivers a signal transposed into a baseband (ie directly around the zero frequency, for example when the radio frequency receivers are of the direct conversion type, or ZIF (for "Zero Intermediate Frequency"), is centered around a low intermediate frequency, for example when the radio frequency receivers are of the conversion type to such a low intermediate frequency, or low-IF (for "low intermediate frequency") to first and second modules of estimation of the data 111, 112 implementing all the demodulation functions conventionally encountered in a reception channel dedicated to digital communications (channel estimation, equalization, symbol decision, etc.).

In this example, the first module 111 estimates the data broadcast on the frequency f1, and the second module 112 estimates the data broadcast on the frequency f2. This data is then transmitted to a switching module 101 whose purpose is to direct either the flow of data from the first data estimation module 111, or the data flow from the second data estimation module 112, to the output of the receiving system and therefore to the user. This switching is managed by a management module 100 which bases the switching decision on Quality of Service (QoS) criteria, associated with the reception quality of the data on the two frequencies. and f2. This may be, for example, an indication of the level of the received radio frequency signal, or RSSI (for "Received Signal Strength Indicator" in English), by each of the two radio frequency receivers, or the error rate of PET or binary BER packets. associated with the data estimated by the first and second data estimation modules 111, 112.

However, it appears that this switching of the data received on each of the reception channels related to the use of this known architecture leads to a degraded user experience. For example, flow interruptions may appear due to the difficulty of managing the synchronization of the two data streams delivered by the first and second data estimation modules 111, 112. Similarly, the information contained in the two received signals at frequencies f1 and f2 is not optimally used to determine the data broadcast in the network. Moreover, the management of the switching between the two data streams according to this known principle leads to a great complexity of implementation.

Thus, there is a need for an improved method of estimating data broadcast in a broadcast network using two distinct carrier frequencies, the two carrier frequencies being used simultaneously for broadcasting the same data during at least one time-lapse area.

There is also a need to improve the user experience, and more particularly during the reception switchover during a received carrier frequency change.

Finally, there is a need for such a method of data estimation and reception switching to be economical for addressing a consumer market.

3 SUMMARY

In one embodiment of the invention, there is provided a method for determining the data estimation mode received by a system comprising at least two radio frequency receivers. Such a method comprises the following steps: obtaining planning information representative of a first and second carrier frequency time usage for data broadcasting, the first and second carrier frequencies being distinct;

determining the estimation mode of the received data according to the planning information.

The determination step takes into account a decision to recombine or not the first and second baseband transposed signals delivered by the at least two radio frequency receivers tuned respectively to the first and second carrier frequencies. The decision to recombine or not is made on the basis of at least the planning information.

Thus, the invention proposes a novel and inventive solution to allow the estimation of data received by a system comprising at least two radio frequency receivers, the data being broadcast at least a portion of the time simultaneously on first and second carrier frequencies.

To do this, the proposed method takes into account scheduling information representative of a first and second carrier frequency time usage for a broadcast of the data in question to determine whether the estimate of the received data is on the basis of recombination, or not, of the corresponding baseband transposed signals in order to take into account all available information at the system level.

According to one embodiment, the obtaining step comprises receiving planning information by at least one of the radio frequency receivers.

Thus the planning information is easily updated by the network broadcasting the data, for example via a broadcast on a dedicated information channel.

According to one embodiment, the obtaining step comprises a reading of the planning information in a system memory.

Thus planning information is easily accessible to the system. In addition, the management of the traffic on the network is simplified, avoiding the dissemination of this planning information. According to one embodiment, the estimation mode corresponds to an estimation of the data received on the basis of a recombination of the first and second base-band transposed signals at least over a predetermined period during which the planning information is representative. simultaneously broadcasting data on the first and second carrier frequencies.

Thus, the joint use of the first and second baseband transposed signals makes it possible to improve the estimation of the received data with respect to the use of only one of the signals in question.

According to one embodiment, the estimation mode corresponds to an estimate of the data received on the basis of:

the first baseband transposed signal when the scheduling information is representative of a broadcast of data only on the first carrier frequency;

the second baseband transposed signal when the scheduling information is representative of a broadcast of data only on the second carrier frequency; and

recombining the first and second baseband transposed signals when the scheduling information is representative of simultaneously broadcasting the data on the first and second carrier frequencies.

Thus the joint use of the first and second signals transposed in baseband during the entire period of broadcasting data simultaneously on the first and second carrier frequencies makes it possible to optimize the estimation of the data received by using, at any time, all the information available at the system level.

According to one embodiment, the step of determining the estimation mode of the received data comprises, when the planning information is representative of a broadcasting of data simultaneously on the first and second carrier frequencies, obtaining a first and a second quality information associated with a signal received respectively on the first and second carrier frequencies. The decision to recombine or not is made on the basis additionally of the first and second quality information.

Thus, even if the data are simultaneously broadcast on the first and second carrier frequencies, the quality of a signal is taken into account in deciding whether to recombine or not. This makes it possible to limit such recombination to situations where it actually provides a gain in processing, ie to cases where the quality of the recombined signals is sufficiently good, thereby limiting the computing load and the energy consumption of the system. .

recombination of the first and second baseband transposed signals when the first quality information, respectively the second quality information, is greater than a first low threshold, respectively a second low threshold;

the second baseband transposed signal if the first quality information is less than or equal to the first low threshold and the second quality information is greater than the second low threshold;

of the first signal transposed into baseband if the first quality information is greater than the first low threshold and if the second quality information is less than or equal to the second low threshold.

Thus, the consideration of quality information is simple and robust.

According to one embodiment, the step of determining the estimation mode of the received data comprises, when the planning information is representative of a broadcasting of data simultaneously on the first and second carrier frequencies, obtaining a first and a second time reception quality variation information associated with a received signal respectively on the first and second carrier frequencies. The decision to recombine or not is made on the basis additionally of the first and second quality temporal variation information. Thus, the temporal evolution of the quality of a signal is taken into account in deciding to recombine or not. This makes it possible to anticipate such recombination in situations where it actually provides a gain in processing, ie in cases where the quality of the recombined signals is not deteriorating too abruptly.

recombination of the first and second baseband transposed signals when:

the first quality information, or the second quality information, is greater than a first low threshold or a second low threshold; and

the first quality variation information, or the second quality variation information, is greater than a first variation threshold or a second variation threshold;

the second signal transposed into baseband when:

the first quality information is less than or equal to the first low threshold or the first quality variation information is less than or equal to the first threshold of variation; and

the second quality information is greater than the second low threshold and the second quality variation information is greater than a second quality variation threshold;

the first signal transposed to baseband when:

the first quality information is greater than the first low threshold and the first quality variation information is greater than a first quality variation threshold; and

the second quality information is less than or equal to the second low threshold or the second quality variation information is less than or equal to the second variation threshold; the first and second quality variation information being positively defined.

Thus, taking into account the reception quality variation information over time is simple and robust.

According to one embodiment, the estimation mode of the received data is updated and corresponds to an estimate of the data received on the basis of:

the first signal transposed into baseband if the first quality information is greater than a first high threshold and the second quality information is less than or equal to a second high threshold;

the second signal transposed into baseband if the second quality information is greater than the second high threshold and if the first quality information is less than or equal to the first high threshold;

of a baseband transposed signal on which the estimation of the data received following a previous execution of the step of determining the estimation mode of the data received was based if the first and second quality information are respectively greater than the first and second high thresholds.

Thus, even if the data are simultaneously broadcast on the first and second carrier frequencies, the estimation of the data is based on a single signal when the quality information corresponding to this signal is greater than a high threshold, ie when the reception on this frequency is good enough that the data estimated on the basis of this signal alone are considered sufficiently reliable. Thus, the other receivers can be placed in a waiting position and the estimation of the received data can be done in a simplified way. All this contributes to the minimization of the energy consumption of the reception system.

According to one embodiment, the step of determining the estimation mode of the received data comprises, when the estimation of the received data is based on the first signal transposed into baseband, respectively on the second signal transposed into baseband. , a transmission to the second radio frequency receiver, respectively to the first radio frequency receiver, of a scanning information at least one frequency different from the second carrier frequency, respectively the first carrier frequency.

Thus, when a receiver is not used for estimating the data, it is advantageously used to scan other carrier frequencies, for example a dedicated information channel in order to obtain updated planning information.

In another embodiment of the invention, there is provided a method of switching reception without interruption of service of a system comprising at least two radio frequency receivers. The method is implemented when receiving data broadcast successively over time on at least:

a first carrier frequency during a first predetermined time period;

a second carrier frequency distinct from the first carrier frequency during a second predetermined period of time; and

the first and second carrier frequencies during a predetermined period of time overlap of the first and second predetermined time periods.

Such a method comprises:

at least one step of obtaining planning information as previously described (according to any one of the aforementioned embodiments);

at least three steps for determining the estimation mode of the received data as previously described (according to any one of the aforementioned embodiments), the three steps of determining the estimation mode being implemented successively in time when the system receives the data respectively during the first predetermined time period, during the predetermined time lapse period, and during the second predetermined time period;

at least three estimation steps of the received data taking into account the estimation modes determined respectively during the three steps of determining the estimation mode. Thus, a soft reception switchover (ie without reception interruption) is obtained in the case of a reception switchover from the first carrier frequency to the second carrier frequency.

Moreover, the joint use of the information contained in the first and second baseband signals makes it possible to optimize the estimation of the data received during the period of simultaneous reception on the two carrier frequencies.

According to one embodiment, the carrier frequencies are in the shortwave frequency range.

According to one embodiment, the data broadcast on the first and second carrier frequencies are synchronized in time.

Thus, the hardware implementation of the claimed method is simplified. Indeed, since the radio propagation time between the radio transmitters and the reception system is negligible compared to the symbol time in the existing broadcast networks, a temporal alignment of the data broadcast on the different carrier frequencies makes it possible to dispense with resynchronization means. flows delivered by the different receivers of the reception system before recombination.

According to one embodiment, the recombination implements a maximum ratio recombination technique of the first and second signals transposed into baseband.

Thus, this technique (which is for example used in some circuits dedicated to reception in space diversity) makes it possible to envisage a simple, efficient and economical implementation of an embodiment of the claimed method.

According to one embodiment, the data is broadcast by a digital broadcasting network of the SMFN type (for "Synchronized Multi-Frequency Networks").

The invention also relates to a computer program, comprising program code instructions for the implementation of at least one method as described above, according to any one of its various embodiments, when it is run on a computer. In another embodiment of the invention, there is provided a device for determining the mode of estimation of the data received by a system comprising at least two radio frequency receivers.

Such a device is particularly suitable for implementing the method for determining the estimation mode of the data received according to the invention (according to any one of the various embodiments mentioned above).

Thus, the features and advantages of this device are the same as those of the generation method described above. Therefore, they are not detailed further.

In another embodiment of the invention, there is provided a receiving terminal comprising a system comprising at least two radio frequency receivers tuned respectively to a first carrier frequency and to a second carrier frequency different from the first carrier frequency. Such a terminal comprises a device for determining the estimation mode of the received data as described above (according to any one of its embodiments).

Thus, the characteristics and advantages of this terminal are the same as those of the generation device described above. Therefore, they are not detailed further.

4 LIST OF FIGURES

Other features and advantages of the invention will appear on reading the following description, given by way of indicative and nonlimiting example, and the appended drawings, in which:

FIGS. 1a and 1b illustrate an exemplary broadcast configuration in an SMFN type broadcasting network using two distinct carrier frequencies simultaneously over at least one time overlap period for broadcasting the same data from a broadcast site, according to the art. previous;

FIG. 1a illustrates an optimized receiving system for receiving in the configuration of FIG. 1a according to a technique of the prior art; FIG. 2 illustrates a reception terminal comprising a data estimation device according to one embodiment of the invention;

FIG. 3 illustrates the steps of a method of determining the mode of estimation of the received data according to various embodiments of the invention;

FIG. 4 illustrates a hysteresis system used in one embodiment of the method for determining the data estimation mode according to different embodiments of the invention;

FIG. 5 illustrates the steps of a reception switching method without service interruption according to various embodiments of the invention; FIG. 6 illustrates an exemplary structure of a device for determining the mode of estimation of the received data allowing the implementation of the method of FIG. 3;

FIG. 7 illustrates an example of reception configurations associated with a plan for using shortwave broadcast frequencies in an SMFN type broadcasting network.

DETAILED DESCRIPTION OF THE INVENTION

In all the figures of this document, the elements and identical steps are designated by the same reference.

The general principle of the technique described consists in determining the mode of estimation of the data received by a system comprising at least two radio frequency receivers on the basis of a planning information representative of a time use of first and second carrier frequencies. for a broadcasting of the data in question.

More particularly, the determination of the data estimation mode takes into account a decision to recombine or not the first and second baseband transposed signals delivered by two tuned radiofrequency receivers so as to receive the first and second carrier frequencies, respectively. such decision to recombine or not being made on the basis of at least the planning information. Thus, the information present in the two signals transposed in baseband is better used than in known techniques (in which no recombination is provided) to improve the estimation of the received data.

Furthermore, a soft reception switching (i.e. without reception interruption) is obtained in the case of a reception switchover from the first carrier frequency to the second carrier frequency via a period of simultaneous reception of the first and second carrier frequencies.

FIG. 2 shows a receiving terminal 210 comprising a device for determining the data estimation mode according to one embodiment of the invention.

Such a reception terminal 210 is for example considered to receive the data broadcast by the broadcast site of the network of FIG.

More particularly, the receiving terminal 210 comprises a reception system comprising two radio frequency receivers identical to the aforementioned receivers RX1 and RX2. The reception system further comprises a data estimation module 201. Unlike the first and second data estimation modules 111, 112 of the known architecture described in relation to FIG. 1c, the data estimation module 201 operates in three distinct modes of operation.

In a first mode of operation, the estimation module 201 estimates the data broadcast by the network on the sole basis of the signal broadcast on the first carrier frequency f1. More precisely, the estimation of the data is carried out on the basis of the signal transposed into baseband by one of the two radiofrequency receivers (RX1, RX2), here RX1, tuned to receive the first carrier frequency in question.

In a second mode of operation, the estimation module 201 estimates the data broadcast by the network on the sole basis of the signal broadcast on the second carrier frequency f2. More specifically, the estimation of the data is performed on the basis of the signal transposed into baseband by one of the two receivers. radio frequencies (RX1, RX2), here RX2, tuned to receive the second broadcast frequency in question.

Finally, in a third mode of operation, the estimation module 201 estimates the data diffused by the network on the basis of a recombination of the signals transposed into baseband by the two radio frequency receivers RX1 and RX2 so as to receive the first signals. and second broadcast frequencies.

Thus, unlike known solutions, the estimation of the data is based on an optimized use of the information contained in the two signals broadcast on the first and second carrier frequencies and received by the two receivers RX1 and RX2. Indeed, these signals are emitted on distinct carrier frequencies f1, f2. Frequency diversity is then expected during the propagation on these two frequencies (for example during the ionospheric propagation in the case of a diffusion in short waves). An estimate of the data received on the basis of a joint processing of the two baseband transposed signals delivered by the two radiofrequency receivers RX1 and RX2 then makes it possible to optimize the quality of the data delivered by the estimation module 201.

More precisely, a processing gain can be expected with respect to the processing of only one of the two received signals. Thus, under the assumption that the two received signals are perfectly decorrelated because of the frequency diversity, a 3dB gain can be expected in terms of improvement of the useful signal level equivalent to the input of the reception system.

In the embodiment considered, the estimation of the data taking into account the two baseband transposed signals delivered by the two radio frequency receivers is based on a maximum ratio combination (MRC) technique. in English), well known to those skilled in the art, thus allowing a simple and controlled implementation of the described technique. Such a technique is for example described in the article by AKM Arifuzzman, Md. Anwar Hossain, Nadia Nowshin and Mohammed Tarique, "A comparative performance analysis of CRM diversity receivers in OFDM System", International Journal of Distributed and Parallel Systems (IJDPS) Vol.2, No.4, July 2011. In a variant, the data broadcast by the network on the first and second carrier frequencies are synchronized in time. The implementation of the estimation module 201 is thus simplified. Indeed, since the radio propagation time between the radio transmitters 120fl, 120fl and the reception system is negligible compared to the symbol time in the existing broadcast networks, a temporal alignment of the data broadcast on the different carrier frequencies makes it possible to overcome resynchronization means of the baseband transposed signals delivered by the different radio frequency receivers of the reception system before recombination. In particular, it becomes possible to use existing circuits for receiving spatial diversity reception provided that the two radio frequency receivers embedded in these circuits are able to be tuned to two distinct reception frequencies. This could be the case of the circuits proposed by the manufacturers Siano (SMS4470) or Parrot (Octopus 3), with a slight modification of the functionalities related to the intermediate software layers, or "middleware". Such an embodiment of the described technique is particularly advantageous in terms of complexity and cost of the solution.

The receiving terminal 210 shown in FIG. 2 also comprises a device 200 for determining the estimation mode of the received data, in order to determine which of the three aforementioned operating modes is implemented at a given moment. To do this, the device 200 takes into account a planning information representative of a time use of the first f1 and second f2 carrier frequencies used for broadcasting the data in question.

The taking into account of this planning information by the determining device 200 of the receiving terminal 210 is detailed below, in relation with the method for determining the estimation mode of the received data according to different embodiments of the invention. .

With reference to FIGS. 3 and 4, the steps of a method for determining the estimation mode of the received data according to various embodiments of the invention and an associated hysteresis system are described next. In a step E300, the determination device 200 obtains the planning information representative of a time use, by the broadcast site of the considered network, of the first f1 and second f2 carrier frequencies for the broadcasting of the data.

In embodiments in which the network is broadcasting in shortwave, the planning in question takes into account, for example, ionospheric propagation conditions for each of the frequencies f1 or f2. The planning information then indicates on which time slot the data will be broadcast by the broadcast site on each of the carrier frequencies fl or f2.

For example, the DRM standard provides for conveying in the SDC component (for "Service Description Channel") of the MDI (for "Multiplex Distribution Interface") flow data relating to the alternative broadcast frequencies. For a given broadcasting service, a DRM receiver thus stores all the last alternative frequencies that have been transmitted to it, even when the receiver is switched off / on. The complete list of alternative broadcast frequencies, as well as their effective validity, are broadcast continuously. On average, it is estimated that a 24-hour Short Wave service can represent up to more than ten alternative frequencies.

In some embodiments, step E300 comprises receiving E300a planning information by at least one of the radio frequency receivers RX1 or RX2, the information being broadcast by the network in question. Thus the planning information is easily updated by the network broadcasting the data, for example via a broadcast on a dedicated information channel.

In other embodiments, step E300 includes reading E300b of scheduling information in a memory 603 of the receiving system. Thus planning information is easily accessible to the system. In addition, the management of the traffic on the network is simplified by avoiding the dissemination of this planning information. In a step E310, the determining device 200 determines the estimation mode of the received data according to the planning information obtained during the implementation of the obtaining step E300.

More particularly, the determination of the estimation mode of the received data takes into account a decision to recombine or not the first and second baseband transposed signals delivered by the two radio frequency receivers RX1 and RX2 respectively tuned to receive the first signals. and second f2 carrier frequencies. Such a decision to recombine or not takes into account the planning information obtained during the implementation of step E300 described above.

Thus, in some embodiments the estimation of the received data is effected on the basis of a recombination of the first and second baseband transposed signals at least over a predetermined period during which the planning information is representative of broadcasting data simultaneously on the first and second f2 carrier frequencies. The estimation of the received data is thus improved compared to the known techniques where only one of the signals in question is used for such an estimate.

In some embodiments, the estimate of the received data is based on:

the first baseband transposed signal when the scheduling information is representative of a broadcast of the data only on the first carrier frequency fl (first aforesaid mode of operation);

the second signal transposed into baseband when the planning information is representative of a broadcast of data only on the second carrier frequency f2 (second mode of operation mentioned above); and recombining the first and second baseband transposed signals when the scheduling information is representative of simultaneously broadcasting data on the first and second carrier frequencies (third mode of operation mentioned above). Thus, the joint use of the first and second baseband-transposed signals during the entire data broadcasting period simultaneously on the first f1 and second f2 carrier frequencies makes it possible to optimize the estimation of the received data by using any moment, all information available at the system level.

In some embodiments, when the scheduling information is representative of a data broadcast simultaneously on the first f1 and second f2 carrier frequencies, the decision to recombine or not is made on the basis of additionally first IQ1 and second IQ2. information representative of the quality of reception respectively on each of the reception channels of the system / terminal to determine the estimation mode of the received data.

Thus, the recombination of the first and second baseband transposed signals is limited to situations where it actually provides a processing gain, ie to cases where the quality of the recombined signals is good enough, thereby limiting the load of the signal. calculation as well as the energy consumption of the system. This may be the case for example at the beginning of a time recovery period, when the second frequency f2 for example is not yet received with an optimal quality, or at the end of this same period of time recovery, when the frequency fl for example is received with a quality of less no less good.

To do this, step E310 comprises obtaining E310a of the first IQ1 and second IQ2 information representative of the quality of reception.

According to implementation variants, the first IQ1 and second IQ2 information belong to the group comprising:

an RSSI sent back by each of the radio frequency receivers RX1 and RX2 of the reception system;

a packet error rate or a bit error rate related to each of the reception channels; and

QoS information provided by a higher application layer and associated with each of the reception channels. The determination device 200 compares the first information IQ1 with a first low threshold, threshold_lB, and a first high threshold, threshold_lH, with threshold_lB lower than or equal to threshold_lH.

Similarly, the determining device 200 compares the second information IQ2 with a second low threshold, threshold_2B, and a second high threshold, threshold_2H, with threshold_2B lower than or equal to threshold_2H. In this way :

when IQ1 is greater than threshold_lB and IQ2 is greater than threshold_2B, the estimation of the received data is based on a recombination of the baseband transposed signals delivered by the two radio frequency receivers RX1, RX2 tuned so as to receive respectively the two carrier frequencies fl and f2 (third mode of operation mentioned above);

when IQ1 is less than or equal to threshold_lB and IQ2 is greater than threshold_2B, the estimate of the received data is based on the baseband transposed signal delivered by the tuned radio frequency receiver to receive the second broadcast frequency f2 (second mode aforementioned operation);

when IQ1 is greater than threshold_lB and IQ2 is less than or equal to threshold_2B, the estimation of the received data is based on the baseband transposed signal delivered by the tuned radiofrequency receiver to receive the first broadcast frequency f1 (first mode aforementioned operating principle).

Thus, the consideration of quality information is simple and robust.

In some embodiments, the decision to recombine or not is made on the basis of first IVQ1 and second IVQ2 time reception quality variation information on each of the receiving channels of the system / terminal.

To do this, step E310 comprises obtaining E310b of the first IVQ1 and second IVQ2 receive quality variation information.

For example, the first IVQ1 and second quality variation information IVQ2 are expressed as a differential, over a given period, of a quantity belonging to the group comprising:

an RSSI sent back by each of the radio frequency receivers RX1 and RX2 of the reception system; a packet error rate or a bit error rate related to each of the reception channels; and

a QoS information provided by a higher application layer and associated with each of the reception channels (for example the SNR (for "Signal to Noise Ratio" in English) associated with each of the signals received by the radio frequency receivers RX1 and RX2).

For example, when the differential is defined as the difference between the quality information IQ1 or IQ2 taken at a later date and the quality information IQ1 or IQ2 in question taken at an earlier date, a positive IVQ1 or IVQ2 information indicates a increase in quality on the corresponding reception channel. Conversely, negative IVQ1 or IVQ2 information indicates a decrease in quality. In this case, we speak of quality variation information IVQ1 and IVQ2 defined positively.

Similarly, when the differential is defined as the difference between the quality information IQ1 or IQ2 taken at an earlier date and the quality information IQ1 or IQ2 in question taken at a later date, a positive IVQ1 or IVQ2 information indicates a decrease in quality on the corresponding reception channel. Conversely, negative IVQ1 or IVQ2 information indicates an increase in quality. In this case, we speak of quality variation information IVQ1 and IVQ2 defined negatively.

In variants, the differential in question is estimated by averaging the corresponding quality information over a predetermined time, for example ten seconds.

Thus, the temporal evolution of the quality of a signal is taken into account in deciding to recombine or not. This makes it possible to anticipate such recombination in situations where it actually provides a gain in processing, i.e., in cases where the quality of the recombined signals is not being degraded too abruptly.

To do this, the determination device 200 compares the first quality variation information IVQ1 with a first threshold of variation. Similarly, determination device 200 compares the second quality variation information IVQ2 to a second threshold of variation.

For example, when the quality variation information IVQ1 and IVQ2 are positively defined, it is decided to base the estimate of the received data on a given baseband transposed signal when the corresponding time variation information is greater than the threshold of variation in question (for example if the quality of reception on the corresponding channel is not being degraded too brutally in practice).

On the other hand, in some embodiments, the use of the first IVQ1 and second quality variation information IVQ2 is combined with the use of the first quality IQ1 and second IQ2 information in order to decide whether to recombine or not. Thus, the determination step E310 can implement the step E310a or the step E310b or the two steps E310a and E310b.

For example, when the quality variation information IVQ1 and IVQ2 are positively defined, it is decided to estimate the received data on the basis of:

the recombination of the first and second baseband transposed signals delivered by the two radiofrequency receivers RX1, RX2 tuned to receive respectively the two carrier frequencies f1 and f2 (third mode of operation mentioned above) when:

the first quality information IQ1, respectively the second quality information IQ2, is greater than threshold_lB, respectively threshold_2B; and the first quality variation information IVQ1, respectively the second quality variation information IVQ2, is greater than the first variation threshold, respectively the second variation threshold;

the second baseband transposed signal delivered by the tuned radio frequency receiver to receive the second broadcast frequency f2 (second aforementioned mode of operation) when:

the first quality information IQ1 is less than or equal to threshold_lB or when the first quality variation information is less than or equal to the first quality variation threshold; and the second quality information IQ2 is greater than threshold_2B and the second quality variation information IVQ2 is greater than the second threshold of quality variation;

of the first baseband transposed signal delivered by the tuned radio frequency receiver to receive the first broadcast frequency fl (first mode of operation mentioned above) when:

the first quality information IQ1 is greater than threshold_lB and the first quality variation information IVQ1 is greater than the first threshold of quality variation; and

the second quality information IQ2 is less than or equal to threshold_2B or when the second quality variation information is less than or equal to the second quality variation threshold.

Conversely, when the quality variation information IVQ1 and IVQ2 are negatively defined, their comparison to the corresponding quality variation thresholds is reversed (i.e. "greater than" vs. "less than").

On the other hand, when both the first quality variation information is less than or equal to the first quality variation threshold and the second quality variation information is less than or equal to the second quality variation threshold, only the criteria based on the first IQ1 and the second IQ2 quality information are used to decide how to estimate the received data.

In other embodiments, the estimation mode of the received data is updated. More particularly:

when IQ1, respectively IQ2, is greater than threshold_lH, respectively threshold_2H, the estimate of the received information is based only on the baseband transposed signal corresponding to IQ1, respectively IQ2;

when both IQ1 and IQ2 are greater than threshold_lH and threshold_2H respectively, the estimate of the information received is based solely on the baseband transposed signal on which the estimate of data received following a previous execution was based. of the step of determining the estimation mode of the received data. Thus, even if the data are simultaneously broadcast on the first and second carrier frequencies f1 and f2, if the reception on one of the carrier frequencies f1 or f2 is good enough for the data estimated on the basis of this signal to be considered sufficiently reliable, the estimation of data is performed solely on the basis of this signal. Thus, the second radio frequency receiver can be placed in a waiting position and the estimation of the received data can be done in a simplified manner while minimizing the energy consumption of the reception system.

In variants, threshold_lB is equal to threshold_2B and / or threshold_lH is equal to threshold_2H, which simplifies the implementation and management of the described method.

In another variant, the thresholds threshold_lB, threshold_2B, threshold_lH and threshold_2H are defined relative to a third threshold, threshold_0, thus allowing simpler management of these thresholds with reference to a physical quantity characteristic of radio frequency receivers RX1, RX2 as their threshold of sensitivity for example.

In another variant, a hysteresis is used on the low and high thresholds defined above. This technique makes it possible to dispense with the oscillation phenomena in the decision of the estimation mode delivered by the determination device 200, this type of oscillation leading to a degradation of the estimation of the data in the end.

To do this, as illustrated in FIG. 4, low thresholds called negative thresholds, threshold_lB- and threshold_2B-, and positive thresholds, threshold_lB + and threshold_2B + are defined so as to be lower and higher than thresholds low threshold_lB and threshold_2B respectively. Likewise, so-called negative high thresholds, threshold_lH- and threshold_2H-, and positive thresholds, threshold_lH + and threshold_2H +, are defined so as to be lower and higher than thresholds high threshold_lH and threshold_2H respectively.

Thus, when IQ1, respectively IQ2, believes, the low and high thresholds (threshold_lB and threshold_lH, as well as threshold_2B and threshold_2H respectively) are deemed to be crossed only if IQ1, respectively IQ2, are greater than the corresponding low and high positive thresholds. Conversely, when IQ1, respectively IQ2, decreases, the low and high thresholds (threshold_lB and threshold_lH, as well as threshold_2B and threshold_2H respectively) are not known. only if IQ1, respectively IQ2, are lower than the corresponding low and high negative thresholds.

In some embodiments, step E310 includes E310c transmission of scanning information.

More particularly, when the estimation of the received data is based on the first signal transposed into baseband, respectively on the second signal transposed into baseband, the determination device 200 delivers to the second radio frequency receiver RX2, respectively to the first radio frequency receiver. RX1, a scanning information of a different frequency of the second carrier frequency f2, respectively of the first carrier frequency f1, allowing for example to obtain updated planning information by listening to a dedicated information channel.

We will now describe, in relation to FIG. 5, the steps of a method of switching reception without interruption of service according to different embodiments of the invention.

By way of illustration, the situation of FIG. 1a in which the SMFN distributing the data received by the reception terminal 210 has been planned, has planned a shortwave broadcast of the data successively in time over at least:

the first carrier frequency f1 during a first predetermined time period;

the second carrier frequency f2 distinct from the first carrier frequency f1 during a second predetermined time period; and

the first f1 and f2 carrier frequencies for a predetermined period of time overlap of the first and second time periods.

The determining device 200 of the terminal 210 then implements the step E300 of the method of determining the estimation mode described above in relation to FIG. 3 (according to any one of its embodiments) in order to obtain planning information indicating the use in time of the first fl and second f2 carrier frequencies for the broadcasting of the data in question by the network.

On the basis of the obtained planning information, the determining device 200 determines the estimation mode of the data received by the terminal 210 by implementing the step E310 for determining the estimation mode of the data received from the method of determining the estimation mode described above in relation to FIG. 3 (according to any one of its embodiments).

The received data are then estimated by the data estimation module 201 when an estimation step E500 is implemented on the basis of the baseband transposed signal (s) by one or the other. the two radiofrequency receivers RX1 (or RX2, or RX1 and RX2) according to the decision issued by the determination device 200 during the implementation of the aforementioned step E310.

The implementation of steps E310 and E500 is then done iteratively over time as a function of the carrier frequency or frequencies indicated as being used by the planning information for the dissemination of the data.

For example, three implementations of steps E310 and E500 will follow one another in time so that:

the judging device 200 indicates that the data estimation mode is based on the first baseband transposed signal delivered by the first tuned receiver RX1 to receive the first carrier frequency f1 during the first predetermined time period. The data estimation module 201 then estimates the data on the basis of the first transposed signal only;

the judging device 200 indicates that the data estimation mode is based on a combination of the first transposed signal and the second baseband transposed signal delivered by the second tuned receiver RX2 to receive the second carrier frequency f2 during the predetermined period of time recovery. The data estimation module 201 then estimates the data on the basis of the combination of the two signals transposed into baseband; and the judging device 200 indicates that the data estimation mode is based on the second baseband transposed signal delivered by the second tuned receiver RX2 to receive the second carrier frequency f2 during the second predetermined time period. The data estimation module 201 then estimates the data on the basis of the second transposed signal only.

Thus, the reception switchover is done in a "flexible" manner, ie without service interruption for the end user, while optimizing his experience by improving the estimation of the data received via the joint processing of the two transposed signals. in baseband by the two radiofrequency receivers RX1 and RX2 in the time overlap regions of the diffusion via the two carrier frequencies f1 and f2. Moreover, during the first, respectively second, predetermined time period, the determination device 200 delivers to the second radio frequency receiver RX2, respectively to the first radio frequency receiver RX1, a scanning information of a frequency different from the second carrier frequency f2, respectively of the first carrier frequency fl, in order to obtain, for example, updated planning information by listening to a dedicated information channel.

FIG. 6 shows an exemplary structure of the device 200 for determining the estimation mode of the data received, enabling the method of FIG. 3 to be implemented.

The device 200 comprises a random access memory 603 (for example a RAM memory), a processing unit 602 equipped for example with a processor, and controlled by a computer program stored in a read-only memory 601 (for example a ROM or a hard disc). At initialization, the code instructions of the computer program are for example loaded into the RAM 603 before being executed by the processor of the processing unit 602.

This FIG. 6 only illustrates one of several possible ways of making the device 200 so that it performs certain steps of the method detailed above, in relation to FIG. embodiments). Indeed, these steps can be performed indifferently on a reprogrammable calculation machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of logical gates such as an FPGA or an ASIC, or any other hardware module).

In the case where the device 200 is made with a reprogrammable calculation machine, the corresponding program (that is to say the sequence of instructions) can be stored in a removable storage medium (such as for example a diskette, a CD-ROM or a DVD-ROM) or not, this storage medium being readable partially or totally by a computer or a processor.

An example of reception configurations associated with a plan for using shortwave broadcast frequencies in a DRM type SMFN broadcast network, as well as the associated steps of a method, will now be described in connection with FIG. receiving failover without service interruption according to one embodiment of the invention.

More particularly, each gray square refers to a short-wave (HF) spectrum (Bk) of the high frequency spectrum used for broadcasting in the network in question. Depending on the planning constraints, the frequencies used beyond 14:00 (f5, f6 and f7) are not necessarily identical to the frequencies used in the morning (f1, f2 and f3), but they belong respectively to the same subbands.

In general, with respect to a current frequency fn belonging to a sub-band Bk used at a given instant, the frequencies used at the previous instants fn-1 and following fn + 1 belong here to the adjacent frequency bands Bk-1 and bk + 1. In the case of the frequency band comprising the highest frequencies (here B4), the interval to be considered for the alternative frequencies is that of rank immediately lower (here B3). The frequency plan of the network is for example broadcast via the component SDC (for "Service Description Channel" in English) of the flow MDI (for "Multiplex Distribution Interface" in English) of the DRM network in question. Time lapse intervals (here A, B, C, D, E, F) can be up to a few tens of minutes. As soon as a pair of frequencies is active, the receivers should remain tuned until one of the two frequencies completely disappears. At the end of the broadcast on this frequency, the previously tuned receiver will then be used to scan the new alternative frequencies according to the principle explained above. During the time recovery period, one benefits from the possible exploitation of one or the other of the baseband transposed signals delivered by the receivers RX1 and RX2, and according to a recombination, for example of the MRC type as described above.

Table 1

Table 1 above gives the values of the information IQ1 and IQ2 and the values of the information IVQ1 and IVQ2 positively defined here obtained by the determination device 200 during the implementation of the determination step E310 described above in FIG. relationship with FIGS. 3 and 5 during the reception of the data broadcast in the DRM broadcast network considered. More particularly, the reception detailed in Table 1 is carried out over a time range comprising times tn and tn + 1 belonging for example to the time recovery range E.

The tuning information for the two radiofrequency receivers RX1 and RX2 corresponding to the various estimation modes thus determined during the reception in question are also indicated in this table.

The received data are estimated by the data estimation module 201 when implementing an estimation step E500 on the basis of the baseband transposed signal (s) by one or the other two radio frequency receivers RX1 and RX2 according to the decision issued by the determination device 200.

The sequence of steps E310 and E500 is thus done iteratively when receiving data over a time slot during which the broadcast is done on more than one broadcast frequency so that the described technique allows the terminal composed of both radiofrequency receivers RX1 and RX2 to switch its reception successively from reception on a frequency fn only, until the reception on a frequency fn + 1 alone, passing through an intermediate step of determination of the scattered data on the basis of the recombination of baseband transposed signals delivered by the two tuned radio frequency receivers on the frequencies fn and fn + 1.

Thus, the reception switchover is done in a "flexible" manner, ie without service interruption for the end user, while optimizing his experience by optimizing the estimation of the data received via the joint processing of the two transposed signals. in baseband by the two radio frequency receivers RX1 and RX2 in the time overlap areas.

Claims

A method for determining the estimation mode of data received by a system comprising at least two radio frequency receivers (RX1, RX2),

characterized in that it comprises the following steps:

obtaining (E300) scheduling information representative of a time use of first (f1) and second (f2) carrier frequencies for broadcasting said data, said first and second carrier frequencies being distinct;

determination (E310) of the estimation mode of said received data as a function of said planning information,

said determining step taking into account a decision to recombine or not the first and second baseband transposed signals delivered by said at least two radio frequency receivers tuned respectively to said first and second carrier frequencies, said decision to recombine or not being taken on the basis of at least said planning information.

A method of determining the estimation mode according to claim 1, wherein said obtaining step comprises receiving (E300a) said planning information by at least one of said radio frequency receivers.

A method of determining the estimation mode according to claim 1 or 2, wherein said obtaining step comprises reading (E300b) said scheduling information in a memory (603) of said system.

4. Method for determining the estimation method according to any one of claims 1 to 3,

wherein said estimation mode corresponds to an estimate of said received data on the basis of a recombination of said first and second transposed signals in baseband for at least a predetermined period during which said planning information is representative of broadcasting said data simultaneously on said first and second carrier frequencies.

5. Method for determining the estimation mode according to any one of claims 1 to 4,

wherein said estimation mode corresponds to an estimation of said received data on the basis of:

said first baseband transposed signal when said scheduling information is representative of a broadcast of said data only on said first carrier frequency;

said second baseband transposed signal when said scheduling information is representative of a broadcast of said data only on said second carrier frequency; and

a recombination of said first and second baseband transposed signals when said scheduling information is representative of a broadcasting of said data simultaneously on said first and second carrier frequencies.

6. Method for determining the estimation method according to any one of claims 1 to 5,

wherein said step of determining the estimation mode of said received data comprises, when said scheduling information is representative of a broadcast of said data simultaneously on said first and second carrier frequencies, obtaining (E310a) a first (IQ1) and a second (IQ2) quality information associated with a received signal respectively on said first and second carrier frequencies,

said decision to recombine or not being made on the basis additionally of said first and second quality information.

7. A method of determining the estimation mode according to claim 6, wherein said estimation mode corresponds to an estimation of said received data on the basis of:

said recombination of said first and second baseband transposed signals when said first quality information, respectively said second quality information, is greater than a first low threshold, respectively a second low threshold;

said second baseband transposed signal if said first quality information is less than or equal to said first low threshold and said second quality information is greater than said second low threshold;

said first baseband transposed signal if said first quality information is greater than said first low threshold and said second quality information is less than or equal to said second low threshold.

8. Method for determining the estimation method according to any one of claims 1 to 6,

wherein said step of determining the estimation mode of said received data comprises, when said scheduling information is representative of a broadcast of said data simultaneously on said first and second carrier frequencies, obtaining (E310b) a first (IVQ1) and a second (IVQ2) time reception quality variation information associated with a received signal respectively on said first and second carrier frequencies, said decision to recombine or not being made on the basis further of said first and second information temporal variation of quality.

9. A method of determining the estimation mode according to claim 8 in that it depends on claim 6,

of said recombination of said first and second band-transposed signals basic when:

said first quality information, respectively said second quality information, is greater than a first low threshold, respectively a second low threshold; and

said first quality variation information, respectively said second quality variation information, is greater than a first variation threshold, respectively a second variation threshold;

said second signal transposed into baseband when:

said first quality information is less than or equal to said first low threshold or said first quality variation information is less than or equal to said first threshold of variation; and

said second quality information is greater than said second low threshold and said second quality variation information is greater than a second quality change threshold;

said first signal transposed into baseband when:

said first quality information is greater than said first low threshold and said first quality variation information is greater than a first quality change threshold; and

said second quality information is less than or equal to said second low threshold or said second quality variation information is less than or equal to said second threshold of variation;

said first (IVQ1) and second (IVQ2) quality variation information being positively defined.

10. A method of determining the estimation mode according to claim 7 or 9, wherein said estimation mode of said received data is updated and corresponds to an estimate of said received data on the basis of:

said first baseband transposed signal if said first quality information is greater than a first high threshold and said second quality information is less than or equal to a second high threshold; said second baseband transposed signal if said second quality information is greater than said second high threshold and said first quality information is less than or equal to said first high threshold;

a baseband transposed signal on which the estimation of the data received following a previous execution of said step of determining the estimation mode of said received data is based if said first and second quality information are respectively greater than said first data; and second high thresholds.

11. Method for determining the estimation mode according to any one of claims 4 to 10,

wherein said step of determining the estimation mode of said received data comprises, when said estimate of the received data is based on said first baseband transposed signal, respectively on said second baseband transposed signal, a transmission (E310c) said second radiofrequency receiver, respectively to said first radio frequency receiver, scanning information of at least one frequency different from said second carrier frequency, respectively said first carrier frequency.

12. A method of switching reception without interruption of service of a system comprising at least two radio frequency receivers (RX1, RX2),

said method being implemented when receiving data broadcast successively over time on at least:

a first carrier frequency (F1) during a first predetermined time period;

a second carrier frequency (f2) distinct from said first carrier frequency during a second predetermined time period; and said first and second carrier frequencies for a predetermined period of time overlap of said first and second predetermined time periods, characterized in that it comprises:

at least one step of obtaining (E300) planning information according to any one of claims 1 to 11;

at least three steps for determining (E310) the estimation mode of the received data according to any one of claims 1 to 11,

said three estimation mode determining steps being implemented sequentially in time when said system receives said data respectively during said first predetermined time period, during said predetermined time lapse period, and during said second predetermined time period;

at least three estimation steps (E500) of said received data taking into account the estimation modes determined respectively during said three steps of determining the estimation mode.

The method of any one of claims 1 to 12 wherein said carrier frequencies are in the shortwave frequency range.

The method of any one of claims 1 to 13 wherein the data broadcast on said first and second carrier frequencies is time synchronized.

The method of any of claims 1 to 14 wherein said recombination implements a maximum ratio recombination technique of said first and second baseband transposed signals.

16. The method according to claim 1, in which said data is broadcast by a digital broadcasting network of the SMFN type (for "Synchronized Multi-Frequency Networks").

17. Computer program product, including code instructions of program for the implementation of a method according to at least one of claims 1 to 16, when said program is executed on a computer.

18. A device (200) for determining the mode of estimation of the data received by a system comprising at least two radio frequency receivers (RX1, RX2), characterized in that it comprises a reprogrammable calculation machine (602) or a computer dedicated calculation configured for:

obtaining planning information representative of a use in the first (f1) and second (f2) carrier time for broadcasting said data, said first and second carrier frequencies being distinct;

determining a mode of estimation of said received data according to said planning information,

said determination of said estimation mode taking into account a decision to recombine or not the first and second baseband transposed signals delivered by said at least two radio frequency receivers tuned respectively to said first and second carrier frequencies,

said decision to recombine or not being made on the basis of at least said planning information.

19. Reception terminal (210) comprising a system comprising at least two radiofrequency receivers (RX1, RX2) tuned respectively to a first carrier frequency and to a second carrier frequency different from said first carrier frequency,

characterized in that it comprises a device (200) according to claim 18 for determining the mode of estimation of the data received by said system.