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EP-4128553-B1 - INTELLIGENT PACKET REPETITION IN MOBILE SATELLITE SERVICE (MSS) LINKS TO OVERCOME CHANNEL BLOCKAGES

EP4128553B1EP 4128553 B1EP4128553 B1EP 4128553B1EP-4128553-B1

Inventors

  • DUTTA, SANTANU
  • ZHENG, Dunmiin

Dates

Publication Date
20260506
Application Date
20210324

Claims (20)

  1. A wireless communications system (500) comprising: a bidirectional wireless link (502) between two transceivers (506, 512) containing electronic processors (504, 510), configured to transmit and receive packetized wireless communications, wherein a receiver of one transceiver provides feedback information to a transmitter of the other transceiver, based on the feedback information: the other transceivers' electronic processors (504, 510) determines: that the bidirectional wireless link is subject to a pathloss caused by environmental obstructions, an extent of the pathloss caused by environmental obstructions, and a packet repeat value indicative of a number of packet repetitions necessary to enable the receiver to receive transmitted packets with adequate reliability by packet combining, and subsequent to the said determination, the transmitter sends the transmitted packets to the receiver based on the packet repeat value, wherein the electronic processors are configured to: determine the packet repeat value by: estimating a mean pathloss value for a transmitted signal of the bidirectional wireless link; determining whether the mean pathloss value is less than a first threshold; responsive to determining that the mean pathloss value is less than the first threshold, determining a deficit value for the transmitted signal; determining whether the deficit value is less than a second threshold; responsive to determining that the deficit value is less than the second threshold, determining the packet repeat value based on a functional relationship between the deficit value and a number of packet repetitions.
  2. The wireless communication system (500) of claim 1, wherein the determination of the packet repeat value is made at the receiver.
  3. The wireless communication system (500) of claim 1, wherein the determination of the packet repeat value is made at the transmitter.
  4. The system (500) of claim 1, wherein the electronic processors (504, 510) are configured to determine the deficit value calculating a difference between the first threshold value and the mean pathloss value.
  5. The system (500) of claim 1, wherein the functional relationship is based on an estimate of the packet error rate for the transmitted signal and a received signal to noise ratio for the transmitted signal at a receiver of the second communications device.
  6. The system (500) of claim 1, wherein the first threshold is set to a static value.
  7. The system (500) of claim 1, wherein the first threshold is determined dynamically using a machine learning model trained using historical mean pathloss values for the transmitted signal.
  8. The system (500) of claim 1, wherein the electronic processors (504, 510) are configured to: set an update timer based on a transmission repetition time; and responsive to the update timer expiring, determine an updated packet repeat value.
  9. The system (500) of claim 8, wherein the transmission repetition time is the duration over which repeated transmissions of the transmitted packets are made based on the packet repeat value and a minimum transmission block size for the repeated packet.
  10. The system (500) of claim 1, wherein the wireless communications system (500) is part of a mobile satellite system.
  11. The system (500) of claim 1, wherein the decision to repeat packets and the packet repeat value is informed by the geographic location of the receiving transceiver.
  12. A method for intelligent packet repetition, the method comprising: transmitting and receiving packetized wireless communications between a first communications device and a second communications device via a bidirectional wireless link; receiving, by the first communications device from the second communications device, feedback information including an indication of a pathloss caused by environmental obstructions in the communication channel, the indication including information indicating a presence and an extent of the pathloss caused by environmental obstructions, wherein the feedback does not include status indications for individual received packets; responsive to receiving the indication of a pathloss caused by environmental obstructions in the communication channel, determining a packet repeat value based on the feedback information, wherein the packet repeat value is greater than one; modifying a downlink signal of the bidirectional wireless link to repeat transmitted packets based on the packet repeat value; and transmitting the downlink signal, wherein determining the packet repeat value includes: estimating (402) a mean pathloss value for the downlink signal; determining (404) whether the mean pathloss value is less than a first threshold; responsive to determining that the mean pathloss value is less than the first threshold, determining (408) a deficit value for the downlink signal; determining (410) whether the deficit value is less than a second threshold; responsive to determining that the deficit value is less than the second threshold, determining (412) the packet repeat value based on a functional relationship between the deficit value and a number of packet repetitions.
  13. The method of claim 12, wherein determining (408) the deficit value includes calculating a difference between the first threshold value and the mean pathloss value.
  14. The method of claim 12, wherein the functional relationship is based on an estimate of the packet error rate for the downlink signal and a received signal to noise ratio for the downlink signal at a receiver of the second communications device.
  15. The method of claim 12, wherein the first threshold is set to a static value.
  16. The method of claim 12, further comprising: determining the first threshold dynamically using a machine learning model trained using historical mean pathloss values for the downlink signal.
  17. The method of claim 12, wherein the determination of the packet repeat value is performed by the second communications device.
  18. The method of claim 17, further comprising: setting an update timer based on a transmission repetition time; and responsive to the update timer expiring, determining an updated packet repeat value.
  19. The method of claim 18, wherein the transmission repetition time is the duration over which repeated transmissions of the transmitted packets are made based on the packet repeat value and a minimum transmission block size for the repeated packet.
  20. The method of claim 12, where the first communications device and the second communications device belong to a mobile satellite system.

Description

FIELD Embodiments described herein relate to satellite wireless communications systems and, more particularly, to providing intelligent packet repetition in mobile satellite service (MSS) links to overcome channel blockages. WO 2016/119232 A1 discloses a method to dynamically adjust repetition number of PDSCH with a report of assisted information, comprising reporting an assisted information related to the decoding result of the transport block; and configuring a second repetition number for another transport block or retransmission of the transport block. WO 2017/078784 discloses feedback of number of repetitions needed for successful decoding together with NACK. Estimation based on accumulated SINR of previous repetitions and a target SINR. MEDIATEK INC: "Discussion on PUCCH functionality for Rel-13 MTC", [Online] 19 April 2015 (2015-04-19), 3GPP DRAFT; R1-152114 DISCUSSION ON PUCCH FUNCTIONALITY FOR REL-13 MTC discloses, besides SR and DL HARQ-ACK feedback, reporting the (estimated) number of repetitions based on demodulation result of repeated PDSCH to assist adjustment of repetitions at eNB. SUMMARY In a first aspect of the invention, a wireless communications system is provided according to appended independent claim 1. In a second aspect of the invention, a method for intelligent packet repetition is provided according to appended independent claim 12. Satellite communications systems and methods are widely used for communications with user equipment (UE). Satellite communications systems and methods generally employ at least one space-based component, such as one or more satellites, which are configured to wirelessly communicate with UEs on the Earth. The overall design and operation of cellular satellite systems are well known to those having skill in the art and need not be described further herein. Moreover, as used herein, the term "UE" includes cellular or satellite radiotelephones with or without a multi-line display; Personal Communications System (PCS) terminals (e.g., user terminals) that may combine a radiotelephone with data processing, data communications capabilities; smart telephones that can include a radio frequency transceiver and/or a global positioning system (GPS) receiver; and/or conventional portable computers or other electronic devices, which devices include a radio frequency transceiver. As used herein, the term "transceiver" may refer to a combined transmitter-receiver component or may refer to devices that include separate transmitter and receiver components. A UE also includes any other radiating user device, equipment and/or source that may have time-varying or fixed geographic coordinates and/or may be portable, transportable, installed in a vehicle (aeronautical, maritime, or land-based) and/or situated and/or configured to operate locally and/or in a distributed fashion over one or more terrestrial locations. Furthermore, as used herein, the term "space-based component" or "space-based system" includes one or more satellites at any orbit (geostationary, substantially geostationary, medium earth orbit, low earth orbit, etc.) and/or one or more other objects and/or platforms (e.g., airplanes, balloons, unmanned vehicles, space crafts, missiles, etc.) that has/have a trajectory above the earth at any altitude. Mobile satellite service (MSS) operates with relatively low link margins compared to terrestrial wireless systems. This is because of the much greater propagation ranges involved in MSS relative to terrestrial wireless systems. A typical radio frequency propagation scenario for a terrestrial wireless system is illustrated in FIG. 1. In FIG. 1, a UE 102 is in wireless communication with a transmission tower 104 via one or more non-line-of-sight (NLOS) links 106. In terrestrial wireless systems, it is customary to operate with an approximately 20-30dB margin over a line-of-sight (LOS) link. However, as illustrated in FIG. 1, terrestrial links are normally of non-line-of- sight (NLOS) type. Radio propagation over NLOS links (e.g., the NLOS links 106) occurs mostly by reflections from environmental clutter, for example, buildings 108, trees (not shown), and the like. Terrestrial wireless links are designed so that, despite the direct path being blocked, enough signal power still reaches the receiver of the UE 102 to close the link from a demodulation perspective. Therefore, useful information can be sent over such links. Link closure occurs despite the presence of substantial, excess attenuation and multipath fading relative to a LOS link. In current systems, useful MSS propagation occurs mostly by LOS links, although some multipath reflection and diffraction may also be present, as illustrated in FIG. 2. FIG. 2 shows a satellite 202 sending a signal to a vehicle mounted mobile satellite terminal 204 in an urban area 206. Although it is desirable to operate MSS in LOS conditions, this is not always possible when the user equipment is mobile, for example, as shown in FI