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EP-4432578-B1 - HANDLING EMERGENCY SIGNALS IN A CELLULAR NETWORK

EP4432578B1EP 4432578 B1EP4432578 B1EP 4432578B1EP-4432578-B1

Inventors

  • García Viñas, Aitor
  • GUEVARA VERA, Jose Francisco
  • DOMÍNGUEZ ROMERO, FRANCISCO JAVIER

Dates

Publication Date
20260506
Application Date
20230313

Claims (15)

  1. A method for handling an emergency signal to a first network operated as a non-terrestrial cellular network, the first network operating on a same frequency as a second network, operated as a terrestrial cellular network, the method comprising: operating the first network in a lower activity configuration (200, 300), in which interference from the first network to the second network permits normal operation of the second network; and in response to receiving the emergency signal from a user equipment at the first network, setting the first network to a higher activity configuration (250, 350), causing increased interference from the first network to the second network than in the lower activity configuration.
  2. The method of claim 1, wherein downlink transmissions from the first network are made from a non-terrestrial transmission system having an antenna system that defines a plurality of beams, such that the beams provide separate geographical coverage areas.
  3. The method of claim 1 or claim 2, wherein operating the first network in the lower activity configuration comprises listening at the first network for any emergency signals in a predetermined bandwidth, the predetermined bandwidth being less than a bandwidth used by the second network.
  4. The method of any preceding claim, wherein operating the first network in the lower activity configuration comprises transmitting minimum downlink control signalling from the first network.
  5. The method of claim 4, wherein the minimum downlink control signalling comprises one or more of: cell-specific or common reference signals; a master information block and/or system information block; and 6 physical resource blocks.
  6. The method of claim 4 or claim 5 when dependent on claim 2, wherein the same downlink control signalling is transmitted by more than one of the plurality of beams.
  7. The method of any one of claims 4 to 6, wherein one or more of: the minimum downlink control signalling indicates that the first network is barred except for emergency access; operating the first network in the lower activity configuration comprises listening at the first network for any emergency signals in the same bandwidth in which the minimum downlink control signalling is transmitted; and the emergency signal comprises a random access preamble message.
  8. The method of any one of claims 1 to 3, wherein operating the first network in the lower activity configuration comprises making insufficient downlink transmissions from the first network to allow the user equipment to synchronise with the first network.
  9. The method of claim 8, wherein the emergency signal comprises a predefined random access message indicating an emergency.
  10. The method of claim 9, wherein one or more of: a transmission frequency and/or bandwidth for the emergency signal differs between geographical regions; and the emergency signal is coded with a Zadoff-Chu sequence.
  11. The method of claim 9 or claim 10, wherein the higher activity configuration comprises activating transmission of downlink control signalling from the first network.
  12. The method of claim 11, wherein one of more of: the downlink control signalling from the first network is minimum downlink control signalling; the downlink control signalling permits the user equipment to synchronise with the first network; and downlink transmissions from the first network are made from a non-terrestrial transmission system having an antenna system that defines a plurality of beams, such that the beams provide separate geographical coverage areas, the downlink control signalling only being transmitted on a beam providing a geographical coverage area corresponding with the emergency signal.
  13. The method of any preceding claim, wherein the higher activity configuration comprises sending a Random Access Response message from the first network in response to the emergency signal.
  14. A computer program comprising instructions that, when executed by a processor controlling operation of a first network operated as a non-terrestrial cellular network, cause the processor to perform the method of any preceding claim.
  15. A controller for a first network operated as a non-terrestrial cellular network, the controller being configured to perform the method of any one of claims 1 to 13.

Description

Technical Field of the Disclosure The disclosure concerns handling an emergency signal to a first network operated as a non-terrestrial cellular network. The first network is operating on a same frequency as a second network, operated as a terrestrial cellular network. The disclosure can be implemented as a method, a computer program and/or a controller, for example. Background to the Disclosure Cellular wireless communication networks provide wide geographical coverage by allowing user (mobile) terminals to access the network through a Radio Access Network (RAN) formed of cells, each cell having a specific geographical coverage area. In this context, a cell refers to a base station (RAN access node) having a cell identifier (Cell ID), for example as used in Third Generation Partnership Project (3GPP) standards. Coverage areas of cells may overlap and this may assist to avoid areas without coverage. Nevertheless, there are still certain areas without cellular wireless network coverage, for example where the deployment of cells is hazardous, difficult, costly or a combination of these. This may particularly occur in rural areas and developing countries. Conventional cellular networks have been terrestrial (that is, with access nodes located on the Earth's surface). Non-terrestrial cellular networks have been proposed more recently, for example using a High Altitude Platform (HAP) to provide cells. This allows coverage on the ground as it would be by a typical (terrestrial) Mobile Network Operator (MNO) site, allowing access by the same user or mobile terminals supporting this RAN in the terrestrial networks, in particular using 4G or 5G. In this context, a satellite may be considered a type of HAP and this term includes any type of radio platform, typically operating above 20km in altitude and preferably at a specified, nominal, fixed point relative to the Earth. The term HAP as used herein should not be confused with the term "High Altitude Platform Station" used in the International Telecommunication Union (ITU) Radio Regulations, which has a narrower definition. A RAN provided by a HAP infrastructure involves complexities. Referring first to Figure 1, there is shown a schematic architecture for an exemplary non-terrestrial cellular RAN, in this case provided through a satellite 10. The satellite 10 acts as a repeater between a baseband system 30 and the end users (for example, any SIM-based devices including mobile terminals, not shown). The baseband system 30 generates radio signals for transmission by the satellite 10 and also processes baseband signals received by the satellite 10. Thus, the baseband system 30 provides lower level base station functions (and may be virtualized or non-virtualized) and transmits one or more intermediate signals to the satellite 10. Each intermediate signal represents a baseband carrier signal for a respective cell, each carrier signal having a respective bandwidth. These are provided to a satellite gateway antenna unit 50, which acts as a mixer, multiplexer and ground station radio. The transmission frequency between the gateway antenna unit 50 and the satellite 10 is typically in the Ku-band or Q-band. The communication between the baseband system 30 and the HAP 10 is thereby made through the antenna 50. The intermediate signals (which for Long Term Evolution, LTE signals, also termed 4G, would be Orthogonal Frequency Division Multiplexed, OFDM, signals) are advantageously transmitted to the satellite 10 multiplexed in frequency. Each intermediate signal may thus define a respective carrier signal. The satellite 10 transmits the radio signals using individual, respective beams. A first carrier may be transmitted using a first beam to provide a first coverage area 91 (the upper left area shown), a second carrier may be transmitted using a second beam to provide a second coverage area 92 (the central area shown), a third carrier may be transmitted using a third beam to provide a third coverage area 93 (the top area shown), a fourth carrier may be transmitted using a fourth beam to provide a fourth coverage area 94 (the upper right area shown), a fifth carrier may be transmitted using a fifth beam to provide a fifth coverage area 95 (the lower right area shown), a sixth carrier may be transmitted using a sixth beam to provide a sixth coverage area 96 (the lower central area shown) and a seventh carrier may be transmitted using a seventh beam to provide a seventh coverage area 97 (the lower left area). Communication between the satellite 10 and the end users is in the standardized 3GPP radio access bands. Each carrier signal is transmitted within a respective allocated frequency channel. The satellite 10 is thereby capable of managing a large number of wireless network cells and they can be communicated (that is, transmitted and/or received) over specific areas through directive beams. However, the satellite 10 is limited in both power and bandwidth. The bandwidth limitatio