Method for processing in a telecommunication system and associated telecommunication module

0001The present invention relates to a method of processing in a telecommunication system comprising a first wireless telecommunication module according to a first wireless telecommunication protocol, said first module being adapted to receive a signal comprising at least a first signal according to the first protocol on a wireless transmission channel and comprising an automatic gain calculation block which determines a current gain value as a function of the signal received in said wireless transmission channel and an amplifier adapted to amplify said received first signal according to said current value gain determined according to said received signal.

0002Document is known <patcit id="pcit0001" dnum="US20070064835A1"><text>US 2007/0064835 A1</text></patcit> a method of implementing, after receiving a notification, a countermeasure to reduce the effects of interference.

0003Document is also known <patcit id="pcit0002" dnum="US20040239559A1"><text>US 2004/0239559 A1</text></patcit> a method of reducing interference by detecting a scrambling signal and generating a signal synchronized with said scrambling signal.

0004In addition, document <patcit id="pcit0003" dnum="WO0106669A1"><text>WO 01/06669 A1</text></patcit> a method implemented at a receiver and a transceiver and of anticipating the intervals during which the transceiver is active to desensitize the receiver during said intervals.

0005For example, the ATC transponders (in English "Air Traffic Control") on board the aircraft are used to communicate the position, altitude and / or identity of the aircraft. This communication may be a response generated by the ATC following the reception of a poll transmitted by a secondary radar. This secondary radar is associated with a primary radar which only detects the position of the aircraft in distance and azimuth via the reception of an echo.

0006This response can also be generated by queries from other aircraft in the surrounding airspace. These interrogations are issued by a system called TCAS (Traffic Collision Avoidance System) intended to prevent collisions.

0007In the case of ATC responses corresponding to 1090 MHz (megahertz) frequency pulse trains carrying position, altitude and / or aircraft identity messages, the second harmonic of an ATC response is centered on a frequency Fr_h2, equal to 2180 MHz and has a power level of the order of a few watts.

0008The Applicant wishes to provide the aircraft with mobile telecommunications means, for example of LTE type, which receive the fluxes from the ground transmitter using a radio frequency band which contains this second harmonic.

0009However, the reception capacity of these LTE telecommunications means embedded in an aircraft is heavily impacted during the transmission of ATC responses by the transponder also embedded in the aircraft, because the pulse trains blind and invalid, because of the mechanism adaptive gain of these telecommunications means, the reception, and for a very long time including the time of de-sensitization and re-sensitization of the receiver which is necessary for it to regain the gain allowing it to treat again correctly received LTE signals.

0010Indeed, following each pulse train, the gain decreases sharply and throughout the re-sensitization period, the gain is insufficient to properly process the LTE signal.

0011This results in a loss of flow and an increase in the LTE communication latency that can render the LTE telecommunication means non-operational when the transmissions by the transponder are frequent, especially when the recurrences of pulse trains are greater than or equal to 500 trains. per second, as conventionally met.

0012For this purpose, according to a first aspect, the invention proposes a method of treatment in a telecommunication system of the aforementioned type, characterized in that the telecommunication system comprising a second wireless telecommunication module adapted to intermittently transmit second signals. on the wireless communication channel according to a second communication protocol, each second signal being of less duration than T_max, the method comprises a step according to which when a second signal is determined, by the automatic gain calculation block, as present in the signal received by the first module in said wireless transmission channel, a current gain value is then determined by the automatic gain calculation block independently of the power of said second signal.

0013The proposed solution makes it possible to reduce the drawbacks of the prior art, in particular to limit the impact of the emission of the second signals on the reception of the first signal on said channel.

0014In embodiments, the method of processing in a telecommunication system according to the invention further comprises one or more of the following features:<ul id="ul0001" list-style="dash" compact="compact"><li>the automatic gain calculation block detects a power increase of said received signal and, following the detection of said increase, updates the value of the gain as a function of the power signal thus increased only if the increase in the amplitude persists beyond a duration equal to T_max ;</li><li>the automatic gain calculation block freezes the present value of the gain from said detection during a time delay at least equal to T_max or equal to the minimum between T_max and the duration during which the increase in power persists;</li><li>in a nominal mode of operation of the automatic gain calculation block, said automatic gain calculation block determines the current value of gain as a function of the power of the signal received in said wireless transmission channel;</li></ul>said method comprises the following steps when a second signal is to be transmitted by the second wireless telecommunication module:<ul id="ul0002" list-style="dash" compact="compact"><li>estimating a delay according to the time required for the transmission by the second wireless telecommunications module of said second signal;</li><li>following said estimation, triggering an auxiliary operating mode of the automatic gain calculation block, for a duration equal to said estimated time delay and during which the second signal is emitted, according to which the automatic gain calculation block determines a value gain current independent of the power of the second received signal in said wireless transmission channel;<ul id="ul0003" list-style="dash" compact="compact"><li>a second signal to be transmitted is a response to a message indicating a code and received by the second module, and said duration necessary for the transmission of said second signal is estimated according to said code;</li><li>the telecommunication system is on board a mobile building, the first wireless telecommunication module is a mobile radio receiver adapted to communicate with a remote mobile radio network and the second wireless telecommunication module is a transponder adapted for communicate with a remote radar and / or a remote transponder;</li><li>the first wireless telecommunication protocol is an LTE protocol;</li><li>the second signal of the signal received in said wireless transmission channel by the first wireless telecommunication module is amplified by the amplifier according to said calculated present value of gain;</li><li>the first wireless telecommunication protocol is adapted so that the first module detects that it has not correctly received a signal intended for it and for following said detection, correctly reconstructing or re-transmitting said first signal to the second module;</li><li>the first wireless telecommunication protocol is adapted so that the first module detects that it has not correctly received a signal intended for it and for following said detection, correctly reconstructing or re-transmitting said first signal to the second module.</li></ul></li></ul>

0015According to a second aspect, the present invention proposes a wireless telecommunication module according to a first wireless telecommunication protocol, adapted to receive, on a wireless transmission channel, a signal comprising at least a first signal according to the first protocol and comprising an automatic gain calculation block adapted to determine a gain value as a function of the signal received in said wireless transmission channel and an amplifier adapted to amplify said received signal according to a gain value determined by the automatic calculation block gain; said wireless telecommunication module being intended for a telecommunication system comprising another wireless telecommunication module adapted to intermittently transmit second signals over the wireless communication channel according to a second communication protocol, each second signal being of duration less than T_max, said wireless telecommunication module according to a first wireless telecommunication protocol being characterized in that the automatic gain calculation block is adapted for, when determining that a second signal is present in the received signal, determining a current value gain independently of the power of said second signal.

0016In embodiments, the wireless telecommunication module further includes one or more of the following features:<ul id="ul0004" list-style="dash" compact="compact"><li>the automatic gain calculation block is adapted to detect an increase in power of said received signal and, following the detection of said increase, to update the value of the gain as a function of the power signal thus increased only if the increase in the amplitude persists beyond a duration equal to T_max ;</li><li>the automatic gain calculation block is adapted to fix the present value of the gain from said detection and during a time delay equal to T_max or equal to the minimum between T_max and the duration during which the increase in power persists;</li><li>in a nominal operation mode of the automatic gain calculation block, said automatic gain calculation block is adapted to determine the current value of gain as a function of the power of the signal received in said wireless transmission channel; and when a second signal is to be transmitted by the second wireless telecommunication module, estimating a delay dependent on the time required for the second wireless telecommunication module to transmit said second signal and triggering an auxiliary operating mode of the second wireless communication module. automatic gain calculation block, for a duration at least equal to said estimated delay and during which the second signal is emitted,</li><li>a second signal to be transmitted is a response to a message indicating a code and received by the second module, and said duration necessary for the transmission of said second signal is estimated according to said code;</li><li>the wireless telecommunication module is intended for an on-board telecommunication system on board a mobile building, said wireless telecommunication module being a mobile radio receiver adapted to communicate with a remote mobile radio network and said second signals being transmitted by a transponder adapted to communicate with a remote radar and / or a remote transponder, and</li><li>the first wireless telecommunication protocol is an LTE protocol.</li></ul>

0017These features and advantages of the invention will appear on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which:<ul id="ul0005" list-style="dash" compact="compact"><li>the <figref idref="f0001">figure 1</figref> represents a view of a wireless telecommunication system in one embodiment of the invention;</li><li>the <figref idref="f0001">figure 2</figref> represents a flowchart of steps of a method in one embodiment of the invention;</li><li>the <figref idref="f0002">figure 3</figref> is a partial view of the transceiver 4 in one embodiment.</li></ul>

0018The <figref idref="f0001">figure 1</figref> is a view of a wireless telecommunication system 2 in one embodiment of the invention.

0019In this case, the wireless telecommunication system 2 is embedded in an aircraft 1.

0020The wireless telecommunication system 2 comprises a transponder 3 and an LTE transceiver 4.

0021The transponder 3, ATC type, is adapted to receive interrogation messages from a remote equipment 12 (for example a secondary radar on the ground or a transponder on board another aircraft etc.).

0022These interrogation messages require the provision, by the transponder 3, of characteristics of the aircraft 1 such as the identity of the aircraft and / or its current altitude and / or position and / or a code indicating its operational situation. (Radio failure, hijacking, etc.) and include at least one respective interrogation code indicating which of these characteristics is required (or which of these characteristics are required) in accordance with one of the three ATC modes: A, C or S.

0023Such an interrogation message in the case considered takes the form of a pulse train at a frequency Fi, for example Fi = 1030 MHz.

0024The transponder 3 is adapted to prepare and transmit an ATC response message to the interrogation message.

0025The content of an ATC response message includes the characteristic (s) of the aircraft 1 required in the interrogation message.

0026In the case considered, an ATC response message takes the form of a pulse train transmitted to a radio frequency Fr, for example Fr = 1090 MHz, and the length of this train is at most T_max = 120 microseconds (μs): Depending on the characteristic (s) transmitted, the length of the train is either 25 μs or 120 μs.

0027The second harmonic of an ATC response message is centered on a frequency Fr_h2, equal to 2180 MHz and is spread over approximately 10 MHz.

0028The power level of this second harmonic is typically a few watts.

0029The transceiver LTE 4 is adapted to transmit or receive data to and from, respectively, at least one base station 11, of type eNode B, arranged on the ground and in radio range of the transmitter -receiver LTE 4.

0030These data transmissions and receptions are carried out in accordance with the LTE (Long Term Evolution) protocol defined by the 3GPP consortium.

0031The receiving band of the transceiver 4 is the band B_rec, which is the band [2170 MHz, 2185 MHz] in this case.

0032The LTE transceiver 4 comprises an antenna 6 for receiving LTE signals in said band. The transceiver LTE 4 comprises a reception circuit of the signals received via the antenna 6 and corresponding to the band B_rec, said receiving circuit comprising an amplifier stage 7 and a block 8 of automatic gain control.

0033Antenna 6 receives a current signal in band B_rec and provides, after filtering the signals in this band, this current signal received at the amplifier 7.

0034The LTE transceiver 4 further comprises an LTE signal transmission circuit (not shown).

0035The amplifier stage 7, for example of the low noise amplifier type, called LNA (of the English "Low Noise Amplifier"), is adapted to amplify the current signal supplied to it by the antenna 6 by multiplying it by a gain the value of which is provided by the block 8 of automatic gain control.

0036This amplified signal supplied by the amplifier stage 7 is then subjected to processing implemented by the receiver circuit of the transceiver 4, including baseband conversion, baseband processing, and then LTE demodulation. .

0037The amplified signal is also provided at the input of the automatic gain control block 8.

0038Block 8 of automatic gain control is adapted to determine, based on the signal recently received in band B_rec (Typically the last received signal is the entire signal received and supplied by the antenna 6 from a time window of duration T₀ ending at the current instant considered t, with T₀ fixed according to the embodiment), the current value of the gain to be applied by the amplifier 7 to the received current signal.

0039The purpose of this adaptive gain is to obtain at the output of the amplifier stage 7 a substantially constant amplitude signal equal to a target amplitude value (typically the gain is low when the power of the LTE signal received last is large, and the gain is strong when the power of the LTE signal received recently is low: the gain is a decreasing power of the power of the LTE signal lately received).

0040According to the invention, the automatic gain control block 8 is adapted to determine a current value of gain, as a function of the signal recently received and supplied by the antenna 6, independently of the power of an ATC response message. transmitted by the transponder 3 when determined by the block 8, such an ATC response message is part of the current signal received.

0041Thus according to the invention, the transceiver 4 is adapted to implement the set of steps 100 comprising the steps 101, 102, 103.

0042In a step 101, the current signal, named S (t), received by the antenna 6 in the B-band_rec is supplied at time t to the amplifier stage 7.

0043In a step 102, the amplifier stage 7 amplifies the received current signal S (t) by the current value supplied by the automatic gain control block 8 and supplies the signal thus amplified, named S_at(t), in parallel with the part of the reception circuit responsible for the LTE demodulation and with the automatic gain control block 8.

0044In a step 103, the automatic gain control block 8 determines a present value of gain according to the received signal (ie according to S_at(T)).

0045And when an ATC response message transmitted by the transponder 3 is part of the received signal, the automatic gain control block 8 determines a present value of gain independently of the power of this ATC response message.

0046The automatic gain control block 8 delivers to the amplifier stage 7 this current discounted value of determined gain.

0047In a particular implementation of a first embodiment, reference is made to the portion of transceiver 4 shown in FIG. <figref idref="f0002">figure 3</figref>.

0048The transceiver 4 comprises the antenna 6, the amplifier stage 7, an analog-digital converter 20, a digital frequency down-converter 21, also called DDC 21 (in English "Digital Down Concerter") and the block 8 automatic gain control.

0049The automatic gain control block 8 comprises an envelope detector 9, a calculation block 10, a digital-analog converter 22 and a gain calculation controller 25.

0050The gain calculation controller 25 comprises, in the case considered, a low-pass filter 11, a subtractor 12, a hysteresis comparator 13 and a delay device 14.

0051This processing makes it possible to eliminate from the signal taken into account for the adaptation of the gain components of duration equal to or less than T_max.

0052Thus, in this first embodiment of the invention, the following substeps take place during step 102.

0053The signal received by the antenna, which is then applied bandpass bandwidth filtering band B_rec is supplied to the amplifier stage 7. The amplifier stage 7 applies to the signal that it receives as input the current gain then calculated by the block 8 of automatic gain control. The signal thus amplified is digitized by the analog-digital converter 20, lowered in frequency by the DDC 21, then is sent, on the one hand to the LTE demodulation device, on the other hand to the automatic gain control block 8. .

0054In the automatic gain control block 8, the envelope of the input signal is detected by the envelope detector 9. And this signal from the envelope detector 9 is sent, on the one hand, to the calculation block 10, on the other hand to the gain calculation controller 25 (point A).

0055Subtractor 12 makes the difference between the amplitude of the signal entering at point A and the amplitude of the average value of said signal (received at point B), the average value obtained by passing said signal in the low-pass filter 11 of frequency of cut much lower than the inverse of the desired reaction time for the gain calculation controller 25 (typically in the case considered, the cutoff frequency is chosen to be equal to 800 Hz).

0056The difference (obtained at point C) between the incoming signal and its mean value is then applied to the positive input of the amplitude comparator 13 at hysteresis. On the negative input of the comparator 13 is applied a high threshold value. The effect of the hysteresis comparator 13 results in the fact that the crossing of the high threshold by the signal applied to the positive input will result in a high switching of the comparator output if this threshold crossing corresponds to an increase of the amplitude of the signal. The low switching of the comparator output will occur if the signal applied to the positive input takes a zero value and if this threshold crossing corresponds to a decrease in the amplitude of the signal.

0057Thus a sharp increase in the signal at the input of the controller 25 (point A) will thus induce a high-level switchover of the output of the comparator 13 (point D). A return to the initial amplitude of the signal will return the output of the comparator 13 to the low state.

0058The output of the comparator 13 (point D) is applied, on the one hand, to the triggering input of the delay device 14 and, on the other hand, to the reset input of this delay device 14. The passage of the low state in the high state (rising edge) on the triggering input of the delay device 14 triggers the activation of a control signal (point E) during a delay slightly greater than the duration of the longest bursts of the ATC signal (which are here 120 μs). The transition from the high state to the low state (falling edge) on the reset input of the delay device 14 interrupts the activation of a control signal that has previously been triggered (point E).

0059A sharp increase in the signal at the input of the device (point A) will therefore trigger activation of the control signal (point E) for a duration of 120 μs. The end of the timer interrupts the activation of the control signal. A return to the initial amplitude of the signal interrupts the activation of the control signal (in the case, for example, of a return to the initial amplitude after a strong increase of the signal during a duration of 25 μs).

0060The above control signal (point E) is applied to a blocking input of the gain calculation block 10.

0061The activation of the control signal requires the gain calculation block 10 to keep the gain supplied to the amplifier stage 7 (point F) constant, and of value equal to the value of this gain present at the moment of the triggering of the activation of the control signal. The interruption of the control signal enables the gain calculation block 10 to update the gain as a function of the value of the signal present on its input (the gain then determined being a decreasing function of the power of the present signal so as to obtain output of the amplifier 7 a signal of constant amplitude).

0062A sharp increase of the signal at the point A will therefore result in a corresponding variation of the gain applied by the amplifier stage 7 (point F) only if the new value of the input signal lasts more than 120 μs. A "moderate" increase or a decrease in the signal at point A will result in a variation of the gain applied by the amplifier stage 7 as if the gain calculation controller 25 were absent (the latter is transparent to the "natural" evolutions of the LTE signal ).

0063The reaction time of the automatic gain control block 8 on the appearance of a high power signal in the B-band_rec is short (de-sensitization), but the re-sensitization time is longer (several ms) so as not to erase the envelope modulation of the received signal.

0064This treatment serves to eliminate the rapid variations in the level of the received signal (of duration less than T_max, here T_max 120 μs) in order to take into account in the adaptive calculation of the gain calculation block 10 only the level variations corresponding to a change in the useful signal for the LTE receiver, of the slow fading type, antenna masking. .

0065At the sudden appearance of a strong level signal on the antenna 6, the following cases may occur:<ul id="ul0006" list-style="dash" compact="compact"><li>the variation of level is linked to a sudden evolution of the useful signal: the reaction of the block 8 of automatic gain control, and thus the adaptation of the gain, is delayed from T_max, here T_max = 120 μs: the receiver is "blinded" for a maximum duration of T_max ie the signal provided by the amplifier will be too strong with respect to the target amplitude for 120 μs;</li><li>the variation in level is due to the transmission of a 25 μs ATC pulse train by the transponder 3: the reaction of the automatic gain control block 8 following this variation is inhibited by the action of the filter 9; the receiver is "blinded" for a maximum duration of T_max 120 μs, but there is no dead time of re-sensitization of several ms at the end of the emission of the pulse train as suffered in the operation according to the prior art;</li><li>the level variation is due to the emission of an ATC pulse train from T_max = 120 μs by the transponder 3: the reaction of the automatic gain control block 8 following this variation is inhibited by the action of the filter 9; the receiver is "blinded" for a duration T_max of 120 μs, but again there is no dead time of re-sensitization of several ms at the end of the emission of the pulse train as suffered in the operation according to the prior art.</li></ul>

0066In a second particular embodiment of the invention, the automatic gain control block 8 is adapted to operate according to two alternative modes of operation: the nominal operating mode and the auxiliary operating mode.

0067In one embodiment, the switchover to the auxiliary operating mode is triggered by the reception by the automatic gain control block 8 of a notification sent by the transponder 3 to the block 8 via a communication bus indicating the imminent dispatch of an ATC response message by the transponder 3.

0068In one embodiment, the duration T_train the response message that will be sent (this duration depending on the corresponding interrogation message) is indicated in the notification.

0069In the nominal operating mode, said automatic gain control block 8 determines, in step 102, the current value of gain G as a function of the power of the signal recently received in said wireless transmission channel, ie as a function of S (t-θ) for any θ between 0 and T₀.

0070In the auxiliary operating mode of the automatic gain control block 8, the automatic gain control block determines a current gain value G (t) according to a gain calculated by the automatic gain control block 8 beforehand. to switch to the auxiliary operating mode (or a predetermined value, corresponding for example to an average gain of an LTE signal received without the presence of an ATC response).

0071And the automatic gain control block 8 is adapted to switch to the auxiliary operating mode just before an ATC pulse train is emitted by the transponder 3, to remain in this auxiliary operating mode during a TEMP time delay and to switch from the auxiliary operating mode to the nominal operating mode at the end of the TEMP time delay.

0072The value of the delay TEMP is chosen at least equal to the duration of transmission of said pulse train.

0073According to the embodiments, TEMP is taken equal to the transmission duration of said pulse train T_train (equal to 25 or 120 μs depending on the type of response) or equal to the maximum duration T_max. Or again TEMP is taken equal to the sum of T_train (or T_max) and T₀.

0074The invention makes it possible to reduce the disadvantages of the prior art, in particular to limit the impact of the transponder response message pulses on the LTE communications to a level corresponding substantially to the actual duration of transmission of the response messages.

0075Furthermore, in the various embodiments, it will be detected by the transceiver LTE 4 and / or the eNode B 11, if data transmitted by the eNode B 11 have not been received by the LTE 4 transceiver, thanks to LTE protocol reliability algorithms. The transmission errors due to the missing data are corrected by the transceiver 4 by means of redundancies in the received data (and without resorting to retransmissions) or the missing data are retransmitted.

0076Such algorithms are for example the algorithms H-ARQ (in English "Hybrid Automatic Repeat reQuest") and RLC (in English "Radio Link Control") in particular. H-ARQ in particular acts in 1 to 2 milliseconds, which makes it possible to strongly limit the consequences of a blindness and to make the latter imperceptible for LTE communications of data or speech type.

0077In the particular embodiment described above, a harmonic of the main signal transmitted by the transponder and the reception band of the LTE transceiver included the same channel; the invention can of course be used in a case where the main signal itself emitted by the transponder and the LTE module receiving band share the same channel.

0078The invention has been described above with respect to a transponder and an LTE transceiver. Of course, in another embodiment of the invention, the transponder and the LTE transceiver are, one and / or the other, replaced by any other type of radio frequency equipment using a common radio frequency channel.

0079In the particular embodiment described above, the duration of the messages could take two alternative values; in other embodiments, the duration of the messages may take any number of values.

0080Furthermore, in the embodiment described above, the automatic gain control is performed on the signal after amplification. In another embodiment, it is realized on the signal before amplification.