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EP-4581773-B1 - CHANNEL HOPPING METHODS AND APPARATUS

EP4581773B1EP 4581773 B1EP4581773 B1EP 4581773B1EP-4581773-B1

Inventors

  • AROUA, Sabrine
  • SAFFAR, Illyyne
  • KHEIR, Nizar

Dates

Publication Date
20260506
Application Date
20220902

Claims (17)

  1. A method (100) performed by a Radio Access Network, RAN, node in a communication network, the method comprising: on detecting that a first channel, over which the RAN node is exchanging communication signals with a first user node, is subject to a jamming attack (110): identifying, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with the jamming attack (120); initiating communication with the first user node over the identified channel (130); and causing communication signals on the first channel to emulate the communication signals that were exchanged between the RAN node and the first user node over the first channel (140).
  2. A method (300) performed by a first user node in a communication network, the method comprising: on detecting that a first channel, over which the first user node is exchanging communication signals with a Radio Access Network, RAN, node, is subject to a jamming attack (310): communicating with the RAN node over an identified channel, wherein the identified channel has been identified, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, as being predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack (320); and causing communication signals on the first channel to emulate the communication signals that were exchanged between the RAN node and the first user node over the first channel (320i).
  3. The method as claimed in claim 2, further comprising: identifying, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack (420).
  4. The method as claimed in claim 3, wherein identifying, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest TTR with an entity targeting the first user node with a jamming attack comprises using a Reinforcement Learning process to identify the channel (420a).
  5. The method as claimed in claim 3 or 4, wherein identifying, from among channels in the communication network that are not currently occupied by any user node having a priority over a threshold level, the channel that has the lowest probability of being subject to a jamming attack by an entity targeting the first user node comprises: using the Upper Confidence Bound, UCB, algorithm to identify the channel (420b), wherein channel value comprises a function of similarity between at least one of: data exchanged between the RAN node and the first user node, and data exchanged between the RAN node and a user node occupying the channel; and signal distributions of the data exchanged between the RAN node and the first user node, and the data exchanged between the RAN node and a user node occupying the channel.
  6. The method as claimed in any one of claims 3 to 5, wherein identifying, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack comprises: for channels in the communication network, estimating a probability of being subject to a jamming attack by an entity targeting the first user node (420c).
  7. The method as claimed in claim 6, wherein estimating a probability of a channel being subject to a jamming attack by an entity targeting the first user node comprises calculating the estimated probability as a function of (221a): a similarity measure between data exchanged between the RAN node and the first user node, and data exchanged between the RAN node and a user node occupying the channel; and a similarity measure between the signal distributions of the data exchanged between the RAN node and the first user node, and the data exchanged between the RAN node and a user node occupying the channel.
  8. The method as claimed in claim 7, wherein the similarity measure comprises Mutual information (221c).
  9. The method as claimed in claim 7 or 8 wherein estimating a probability of a channel being subject to a jamming attack by an entity targeting the first user node comprises calculating the estimated probability as a function also of a jamming gain parameter for the channel (221b), wherein the jamming gain parameter for the channel is a function of: the channel gain between the user node occupying the channel and the jamming entity in the channel; and the power transmission on the channel by the user node occupying the channel.
  10. The method as claimed in any one of claims 6 to 9, wherein estimating a probability of a channel being subject to a jamming attack by an entity targeting the first user node comprises calculating the estimated probability as the product of (221c): the Mutual Information, MI, between data exchanged between the RAN node and the first user node, and data exchanged between the RAN node and a user node occupying the channel; the MI between the signal distributions of the data exchanged between the RAN node and the first user node, and the data exchanged between the RAN node and a user node occupying the channel; and a jamming gain parameter for the channel, wherein the jamming gain parameter for the channel is a function of: the channel gain between the user node occupying the channel and the jamming entity in the channel; and the power transmission on the channel by the user node occupying the channel.
  11. The method as claimed in any one of claims 3 to 10, wherein identifying, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack comprises: using a Reinforcement Learning process to explore an action space of channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level while prioritizing identification of a channel having a lowest estimated probability of being subject to a jamming attack by an entity targeting the first user node (420d).
  12. The method as claimed in any one of claims 3 to 11, wherein identifying, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack comprises: identifying a candidate set of channels that are not currently occupied by any user having an assigned priority above the threshold level (222); for channels in the candidate set (221): calculating a value of each channel during a respective time slot as a function of an estimated probability that the channel will not be subject to a jamming attack by an entity targeting the first user node (223); calculating a measure of uncertainty in the calculated channel value (224); and calculating a channel score as a sum of the channel value and channel value uncertainty (225); and selecting as the identified channel, the channel having the highest channel score (226).
  13. The method as claimed in claim 12, wherein the value of a channel increases as the estimated probability that it will not be subject to a jamming attack by an entity targeting the first user node increases (223a).
  14. The method as claimed in claim 12 or 13, wherein the probability that the channel will not be subject to a jamming attack by an entity targeting the first user node comprises the complement of the probability that the channel will be subject to a jamming attack by an entity targeting the first user node (223a).
  15. A computer program product comprising a computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform a method as claimed in any one of claims 1 to 14.
  16. A RAN node (500) in a communication network, the RAN node comprising processing circuitry configured to cause the RAN node to: on detecting that a first channel, over which the RAN node is exchanging communication signals with a first user node, is subject to a jamming attack: identify, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, the channel that is predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack; initiate communication with the first user node over the identified channel; and cause communication signals on the first channel to emulate the communication signals that were exchanged between the RAN node and the first user node over the first channel.
  17. A first user node (700) in a communication network, the first user node comprising processing circuitry configured to cause the first user node to: on detecting that a first channel, over which the first user node is exchanging communication signals with a Radio Access Network, RAN, node, is subject to a jamming attack: communicate with the RAN node over an identified channel, wherein the identified channel has been identified, from among channels in the communication network that are not currently occupied by any user node having an assigned priority over a threshold level, as being predicted to have the greatest Time To Rendezvous, TTR, with an entity targeting the first user node with a jamming attack; and cause communication signals on the first channel to emulate the communication signals that were exchanged between the RAN node and the first user node over the first channel.

Description

Technical Field The present disclosure relates to a method performed by a Radio Access Network (RAN) node in a communication network, and to a method performed by a first user node in a communication network. The present disclosure also relates to a RAN node, a first user node, and to a computer program product configured, when run on a computer, to carry out such methods. Background Radio jamming is the act of an illegitimate radio device attempting to disrupt radio communication between a legitimate sender and a legitimate receiver. When they go undetected or unprevented, radio jamming attacks may lead to denial of service on either or both of the impacted user equipment (UE) and the network. Radio jamming attacks are carried out by illicitly occupying the physical medium (i.e., radio channel) that is being used by a legitimate sender. This occupation is achieved by emitting Radio Frequency noise signal, making it impossible for the legitimate receiver to recover the original message emitted by the sender. The shared nature of wireless channels enables a jammer to disable all data transmission within the radio range. The openness and mobility of wireless communication render them vulnerable to various types of jamming attacks, which seriously threaten the users' communication security. Different strategies exist to ensure the safety and security of the wireless medium. Most existing strategies focus on designing anti-jamming techniques, enabling legitimate users to continue their communication securely. Existing anti-jamming techniques may be classified into two main classes, Rate Adaptation/power control, and channel hopping. The basic idea of power control and rate adaptation schemes consists of estimating the channel conditions and adjusting the data rate or the power transmission in order to improve communication quality. The jammer's signal is effectively considered as interference, and despite the present threat, legitimate users continue to use the same channel as jammers. When varying, i.e., increasing or decreasing, the data rate or the power control, legitimate users focus on how to override the jamming signal in a way to ensure successful data transmission from emitters to receivers. However, jammers might adopt the same strategy as the legitimate users and adapt their signals to produce higher interference to legal users. Another side effect of these approaches is that rate adaptation and power control are not well adapted to users with energy constraints, as increasing the power transmission will damage and drain their batteries. The concept of frequency hopping involves switching the carrier frequency between different bands, thereby selecting the best band that improves the quality of service (QoS) and enables better link conditions. Frequency hopping is already used in Bluetooth to enhance its reliability against undesired interfering signals and jamming attacks. In addition, frequency hopping presents the basic concept of cognitive radio networks that guarantee the opportunistic access of secondary users to the licensed bands while not being used by primary, i.e., licensed, users. The channel hopping technique is widely recommended, and in the presence of jammers, when compared with the radio adaptation and power control strategy, frequency hopping has a lower complexity. Legitimate users can escape from jammers and find new channels to improve the reliability of wireless communications. Therefore, channel hopping enables legitimate users to continue the transmission on a new secure channel without interruption. Different studies introducing new channel hopping schemes for anti-jamming communication exist. In Pei, X., Wang, X., Yao, J., Yao, C., Ge, J., Huang, L., & Liu, D. (2019, October) Joint time-frequency anti-jamming communications: a reinforcement learning approach, 2019 11th International Conference on Wireless Communications and Signal Processing (WCSP) (pp. 1-6) IEEE, the authors design a new solution based on the Markov model and reinforcement learning to find the optimal transmission channel that provides the best duration to continue communication, and the maximum long-term cumulative throughput. The study in Lee, E. K., Oh, S. Y., & Gerla, M. (2010, October), Randomized channel hopping scheme for anti-jamming communication, 2010 IFIP Wireless Days (pp. 1-5) IEEE, introduces a Quorum Rendezvous channel hopping scheme. A sender and a receiver do not explicitly establish an initial essential pairing. Instead, they hop over multiple random channels to transmit data without relying on opportunistic encounters. The hopping sequences are constructed from a quorum system to ensure that the nodes can find their next rendezvous channel within a bounded time limit. In Lee et al., new channel sequences are designed to minimize the Time to Rendezvous (TTR) each time a jamming attack is detected. The TTR is the time, measured in time slots, needed for a successful rendezvous, i.e., Reques