Patent Publication Number: US-2023138550-A1

Title: Interference cancellation for satellite communication

Description:
TECHNICAL FIELD 
     The present disclosure relates to satellite communication, and in particular, to corresponding systems and methods for digital radio interference mitigation. 
     BACKGROUND ART 
     Starting with fifth-generation (5G) cellular services, a deployment of a C-Band frequency spectrum (3.4-4.2 GHz) has commenced which is has traditionally been used by satellite services including Fixed Satellite Service (FSS). 
     Therefore, satellite ground reception nowadays may be subject to radio interference from terrestrial radio network transceivers, such as cellular base stations. 
     SUMMARY 
     In view of the above-mentioned drawback, an objective of the present disclosure is to improve a reception of satellite ground stations of the background art. 
     The objective is achieved by the embodiments as defined by the appended independent claims. Preferred embodiments are set forth in the dependent claims and in the following description and drawings. 
     A first aspect of the present disclosure relates to a system for digital radio interference mitigation, comprising a first interface configured to receive a first digital signal associated with a satellite ground station; a second interface configured to receive a second digital signal associated with and acquired at a radio network transceiver; and a signal processing unit connected to the first and second interfaces and configured to mitigate a radio interference associated with the second digital signal in the first digital signal. 
     The first digital signal may comprise a downlink (DL) baseband signal demodulated by the satellite ground station. 
     The first digital signal may comprise a digital I/Q over IP signal. 
     The second digital signal may comprise a DL baseband signal and/or an uplink (UL) baseband signal associated with the radio network transceiver. 
     The second digital signal may comprise a digital I/Q over IP signal. 
     The second digital signal may be demodulated by the radio network transceiver. 
     The system may further comprise a radio probe connectable to the second interface and configured to demodulate the second digital signal from a radio signal acquired within a given distance to the radio network transceiver. 
     The second digital signal may further comprise an information indicative of a beam direction of the radio network transceiver relative to the satellite ground station. 
     The second digital signal may further comprise an information indicative of a channel state between the radio network transceiver and the satellite ground station. 
     The information indicative of the channel state may comprise a channel matrix estimated by the radio network transceiver. 
     The signal processing unit may be configured to mitigate the radio interference associated with the second digital signal in the first digital signal using an adaptive filter. 
     The signal processing unit may further be configured to estimate coefficients of the adaptive filter using one or more of: a least mean squares, LMS, algorithm; a normalized least mean squares, NLMS, algorithm; a recursive least squares, RLS, algorithm; a multiple signal classification, MUSIC, algorithm; and machine learning. 
     The machine learning may comprise supervised training of an artificial neural network. 
     The radio network transceiver may use radio frequencies allocated to a DL of fixed satellite services, FSS. 
     A second aspect of the present disclosure relates to a method for digital radio interference mitigation, comprising: receiving a first digital signal associated with a satellite ground station; receiving a second digital signal associated with and acquired at a radio network transceiver; and mitigating a radio interference associated with the second digital signal in the first digital signal. 
     ADVANTAGEOUS EFFECTS 
     The present disclosure provides systems and for digital radio interference mitigation which may improve a reception of satellite ground stations in coexistence scenarios with 5G cellular radio, by acquiring the interfering digital signal at the interfering radio network transceiver (i.e. cellular base station). 
     Acquisition of an interfering digital baseband signal re-uses an available digital signal and does not create additional computing effort at the interfering radio network transceiver. 
     Acquisition of an interfering digital I/Q over IP signal re-uses available signal processing algorithms and communication protocols. 
     A radio probe configured to demodulate the second digital signal from a radio signal acquired within a given distance to the radio network transceiver provides the interfering digital signal if no direct interface to the interfering radio network transceiver is available or wanted. 
     Including an information indicative of a beam direction of the radio network transceiver relative to the satellite ground station and/or an information indicative of a channel state between the radio network transceiver and the satellite ground station may respectively improve an effectivity of interference cancellation. 
     Mitigation of radio interference using adaptive filters facilitates re-use of available signal processing algorithms, such as LMS, NLMS, RLS and/or MUSIC, and further allows for estimation of coefficients by machine learning. 
     The proposed systems and methods are especially effective if the interfering radio network transceiver uses radio frequencies allocated to a DL of FSS, i.e., upon coexistence in the C-band frequency spectrum. 
     The technical effects and advantages described in relation with the system equally apply to the method having corresponding features. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above-described aspects and implementations will now be explained with reference to the accompanying drawings, in which the same or similar reference numerals designate the same or similar elements. 
       The features of these aspects and implementations may be combined with each other unless specifically stated otherwise. 
       The drawings are to be regarded as being schematic representations, and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to those skilled in the art. 
         FIG.  1    illustrates a system in accordance with the present disclosure; and 
         FIG.  2    illustrates a method in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTIONS OF DRAWINGS 
       FIG.  1    illustrates a system  1  in accordance with the present disclosure. 
     The system  1  is suitable for digital radio interference mitigation. 
     The system  1  comprises a first interface  11  configured to receive a first digital signal  12  associated with a satellite ground station  3 . The first digital signal  12  may comprise a DL baseband signal demodulated by the satellite ground station  3 . In particular, the first digital signal  12  may comprise a digital I/Q over IP signal. 
     The system  1  further comprises a second interface  13  configured to receive a second digital signal  14  associated with and acquired at a radio network transceiver  4 . The radio network transceiver  4  may especially use radio frequencies allocated to a DL of FSS. The second digital signal  14  may comprise a DL baseband signal and/or an UL baseband signal associated with the radio network transceiver  4 . Particularly, the second digital signal  14  may comprise a digital I/Q over IP signal. 
     The second digital signal  14  may be demodulated by the radio network transceiver  4 . Alternatively or additionally (especially in case of a plurality of radio network transceivers  4 ), the system  1  may further comprise a radio probe  5  which is connectable to the second interface  13  and configured to demodulate the second digital signal  14  from a radio signal acquired within a given distance to the radio network transceiver  4 . For example, the given distance may preferably amount to less than 100 meters, more preferably to less than 10 meters, and most preferably even closer (in immediate vicinity of the radio network transceiver  4 ). The second digital signal  14  provided by the radio probe  5  should ideally reproduce the second digital signal  14  provided by the radio network transceivers  4 . 
     One implementation of the radio probe  5  may include a cellular radio receiver configured to demodulate the DL baseband signal of the radio network transceiver  4  from a radio signal, and/or determine an UL channel allocation of the radio network transceiver  4  and demodulate its UL baseband signal from a radio signal. 
     The second digital signal  14  may further comprise an information indicative of a beam direction of the radio network transceiver  4  relative to the satellite ground station  3 , and/or an information indicative of a channel state between the radio network transceiver  4  and the satellite ground station  3 , in particular a channel matrix estimated by the radio network transceiver  4 . For example, a DL baseband signal associated with the radio network transceiver  4  and a channel matrix estimated by the radio network transceiver  4  may be transformed into the interfering DL signal at the satellite ground station  3 . Likewise, an UL baseband signal associated with the radio network transceiver  4  and the channel matrix estimated by the radio network transceiver  4  may be transformed into the interfering UL signal at the satellite ground station  3 . A priori knowledge of the beam direction of the radio network transceiver  4  may further improve these transformations. 
     The system  1  further comprises a signal processing unit  15  connected to the first and second interfaces  11 ,  13  and configured to mitigate a radio interference associated with the second digital signal  14  in the first digital signal  12 , in particular using an adaptive filter  151 . 
     The signal processing unit  15  may further be configured to estimate coefficients of the adaptive filter  151  using one or more of: a least mean squares, LMS, algorithm; a normalized least mean squares, NLMS, algorithm; a recursive least squares, RLS, algorithm (all of which being used for beamforming the radiation patterns of smart antennas); a multiple signal classification, MUSIC, algorithm (used for frequency estimation and radio direction finding); and machine learning. For example, the machine learning may comprise supervised training of an artificial neural network (ANN) based on inputs (at least portions of recorded first and second signals) and a desired output (filter coefficients known to achieve an improvement in digital signal quality of the recorded first signal, such as a bit error ratio (BER), for example). 
       FIG.  2    illustrates a method  2  in accordance with the present disclosure. 
     A second aspect of the present disclosure relates to a method  2  for digital radio interference mitigation, comprising: receiving  21  a first digital signal  12  associated with a satellite ground station  3 ; receiving  22  a second digital signal  14  associated with and acquired at a radio network transceiver  4 ; and mitigating  23  a radio interference associated with the second digital signal  14  in the first digital signal  12 .