A telecommunications network comprising a rydberg-atom based em signal receiver

Abstract

This invention provides a telecommunications network comprising a device and at least one network node. The device comprises a Rydberg-atom based Electromagnetic (EM) signal receiver and an uplink telecommunications interface. The Rydberg-atom based EM signal receiver may be configured in a first Rydberg state for reception at a first frequency. The device may send a request for data via the uplink telecommunications interface. Responsive thereto, the at least one network node may send a first configuration signal at the first frequency to the Rydberg-atom based EM signal receiver, the configuration signal identifying configuration parameters for the Rydberg-atom based EM signal receiver so as to configure the Rydberg-atom based EM signal receiver to a second Rydberg state for reception at a reserved frequency such that a data signal at the reserved frequency causes a detectable change in the Rydberg-atom based EM signal receiver in the second Rydberg state.

Description

[0001] A TELECOMMUNICATIONS NETWORK COMPRISING A RYDBERG-ATOM BASED EM SIGNAL RECEIVER

[0002] Field of the Invention

[0003] The present invention relates to a telecommunications network comprising: a device comprising a Rydberg-atom based Electromagnetic (EM) signal receiver, a network node, a method of operating the device, and a method of operating the network node.

[0004] Background

[0005] Conventional wireless telecommunications protocols typically implement a multiple access technique to determine when a node is permitted to transmit data to another node. These techniques include fixed multiple access schemes, such as Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA), which permanently allocate channels based on time, frequency or code slots. However, this is inefficient in telecommunication networks comprising nodes that communicate infrequently. A further category of multiple access technique includes contention based multiple access, such as Carrier Sense Multiple Access (CSMA), which provide nodes with varying degrees of freedom in transmitting data. The node may check that the channel is not being used by another node before transmiting the data. The contention based multiple access technique may also define how a node can sense if another node is transmitting using the same resource and how to respond. A further category of multiple access technique includes reservation based multiple access, such as the Resource Reservation Protocol (RSVP), in which a node reserves a resource slot for the transmission before the transmission occurs.

[0006] Summary of the Invention

[0007] According to a first aspect of the invention, there is provided a method of operating a device in a telecommunications network, the device comprising a Rydberg-atom based Electromagnetic (EM) signal receiver and an uplink telecommunications interface, the method comprising the steps of: configuring the Rydberg-atom based EM signal receiver to a first Rydberg state for reception at a first frequency; sending a request for data via the uplink telecommunications interface; responsive to the request for data, receiving a configuration signal, the configuration signal being received at the first frequency so as to cause a detectable change in the Rydberg-atom based EM signal receiver in the first Rydberg state, the configuration signal identifying configuration parameters for the Rydberg-atom based EM signal receiver; configuring the Rydberg-atom based EM signal receiver, according to the identified configuration parameters, to a second Rydberg state for reception at a reserved frequency; and receiving a data signal at the configured Rydberg-atom based EM signal receiver, the data signal being received at the reserved frequency so as to cause a detectable change in the Rydberg-atom based EM signal receiver in the second Rydberg state. The first frequency may be different to the reserved frequency.

[0008] The Rydberg-atom based EM signal receiver may be one of a plurality of Rydberg-atom based EM signal receivers and each Rydberg-atom based EM signal receiver may be configured in the first Rydberg state for reception at the first frequency.

[0009] The configuration signal may comprise an identifier for the Rydberg-atom based EM signal receiver and the step of configuring the Rydberg-atom based EM signal receiver may be responsive to the Rydberg-atom based EM signal receiver detecting the identifier for the Rydberg-atom based EM signal receiver in the configuration signal.

[0010] The uplink communications interface of the Rydberg-atom based EM signal receiver may utilise a communications medium that may be shared with another Rydberg-atom based EM signal receiver of the plurality of Rydberg-atom based EM signal receivers. The communications medium may be a physical (i.e. wired) communications medium.

[0011] According to a second aspect of the invention, there is provided a method of operating a network node in a telecommunications network, the telecommunications network comprising a first Rydberg-atom based Electromagnetic (EM) signal receiver, the method comprising the steps of: receiving a request for data from the first Rydberg-atom based EM signal receiver; responsive thereto, reserving a first reserved frequency for communications with the first Rydberg-atom based EM signal receiver; and sending a first configuration signal at a first frequency to the first Rydberg-atom based EM signal receiver, the configuration signal identifying configuration parameters for the first Rydberg-atom based EM signal receiver to receive a data signal at the first reserved frequency.

[0012] The method may further comprise the step of: determining that the request for data from the first Rydberg-atom based EM signal receiver is contention-free. The telecommunications network may comprise a second Rydberg-atom based EM signal receiver and the method may further comprise the steps of: receiving a request for data from the second Rydberg-atom based EM signal receiver; responsive thereto, reserving a second reserved frequency for communications with the second Rydbergatom based EM signal receiver; and sending a second configuration signal at the first frequency to the second Rydberg-atom based EM signal receiver, the configuration signal identifying configuration parameters for the second Rydberg-atom based EM signal receiver to receive a data signal at the second reserved frequency. The first frequency may be different to the first reserved frequency. The first frequency may be different to the second reserved frequency. The first and second reserved frequencies may be different.

[0013] The step of determining that the request for data from the first Rydberg-atom based EM signal receiver is contention-free may comprise determining that the request for data from the first Rydberg-atom based EM signal receiver does not collide with the request for data from the second Rydberg-atom based EM signal receiver.

[0014] The method may further comprise the step of: withdrawing reservation of the first reserved frequency for communications with the first Rydberg-atom based EM signal receiver and / or withdrawing reservation of the second reserved frequency for communications with the second Rydberg-atom based EM signal receiver.

[0015] The telecommunications network may further comprise one or more optical sources, the one or more optical sources may communicate a plurality of optical signals to the first Rydberg-atom based EM signal receiver, and the method may further comprise the steps of: causing configuration of the one or more optical sources according to a first configuration such that the plurality of optical signals configures the first Rydberg-atom based EM signal receiver in a first Rydberg state, wherein the first configuration signal at the first frequency causes a detectable change in the first Rydberg-atom based EM signal receiver in the first Rydberg state; and causing configuration of the one or more optical sources according to a second configuration such that the plurality of optical signals configures the first Rydberg-atom based EM signal receiver in a second Rydberg state, wherein the data signal at the first reserved frequency causes a detectable change in the first Rydberg-atom based EM signal receiver in the second Rydberg state. The one or more optica! sources may communicate the plurality of optica! signals to the second Rydberg-atom based EM signal receiver, configuration of the one or more optica! sources according to the first configuration may be such that the plurality of optica! signals configures the second Rydberg-atom based EM signa! receiver in the first Rydberg-state, the second configuration signa! at the first frequency may cause a detectable change in the second Rydberg-atom based EM signa! receiver in the first Rydberg-state, and the one or more optical sources configured according to the second configuration may be such that the plurality of optica! signals configures the second Rydberg-atom based EM signal receiver in a third Rydberg state, wherein the data signa! at the second reserved frequency may cause a detectable change in the second Rydberg-atom based EM signa! receiver in the third Rydberg state.

[0016] According to a third aspect of the invention, there is provided a method of operating a first network node in a telecommunications network, the telecommunications network comprising a first Rydberg-atom based Electromagnetic (EM) signa! receiver and a second network node, the method comprising the steps of: communicating, from one or more optical sources having a first configuration, a plurality of optical signals to the first Rydberg-atom based EM signa! receiver to configure the first Rydberg-atom based EM signal receiver in a first Rydberg state for receiving at a first frequency; receiving a configuration signal, from the second network node, identifying configuration parameters for the one or more optical sources; configuring the one or more optical sources according to the received configuration parameters to have a second configuration; and communicating, from the one or more optical sources having the second configuration, the plurality of optical signals to the first Rydberg-atom based EM signal receiver to configure the first Rydberg-atom based EM signal receiver in a second Rydberg state for receiving at a first reserved frequency.

[0017] The telecommunications network may further comprise a second Rydberg-atom based EM signal receiver and the plurality of optical signals communicated from the one or more optical sources having the second configuration may be further communicated to the second Rydberg-atom based EM signal receiver to configure the second Rydbergatom based EM signal receiver in a third Rydberg state for receiving at a second reserved frequency. The method may further comprise the steps of: receiving a request for data from the first Rydberg-atom based EM signal receiver, the request for data being received via a telecommunications interface between the first network node and the first Rydberg-atom based EM signal receiver; and sending the request for data from the first Rydberg-atom based EM signal receiver to the second network node, wherein reception of the configuration signal may be responsive to sending the request for data from the first Rydberg-atom based EM signal receiver to the second network node.

[0018] The method may further comprise the step of: determining that the request for data from the first Rydberg-atom based EM signal receiver is contention-free.

[0019] The method may further comprise the steps of: receiving a request for data from the second Rydberg-atom based EM signal receiver, the request for data being received via a telecommunications interface between the network node and the second Rydbergatom based EM signal receiver; and sending the request for data from the second Rydberg-atom based EM signal receiver to the second network node, wherein reception of the configuration signal may be responsive to sending the request for data from the second Rydberg-atom based EM signal receiver to the second network node.

[0020] Determining that the request for data from the first Rydberg-atom based EM signal receiver is contention-free may comprise determining that the request for data from the first Rydberg-atom based EM signal receiver does not collide with the request for data from the second Rydberg-atom based EM signal receiver.

[0021] According to a fourth aspect of the invention, there is provided a computer program comprising: first instructions which, when the program is executed by a device, cause the device to carry out the steps of the method of the first aspect of the invention; second instructions which, when the program is executed by a network node, cause the network node to carry out the steps of the method of the second aspect of the invention; or third instructions which, when the program is executed by a first network node, cause the first network node to carry out the steps of the method of the third aspect of the invention. The computer program may be stored on a computer readable carrier medium. According to a fifth aspect of the invention, there is provided a device comprising a processor configured to carry out the steps of the method of the first aspect of the invention.

[0022] According to a sixth aspect of the invention, there is provided a network node comprising a processor configured to carry out the steps of the method of the second aspect of the invention. The network node may comprise the one or more optical sources.

[0023] According to a seventh aspect of the invention, there is provided a first network node comprising a processor configured to carry out the steps of the method of the third aspect of the invention.

[0024] According to an eighth aspect of the invention, there is provided a telecommunications network comprising: at least one device of the fifth aspect of the invention; and a network node of the sixth aspect of the invention.

[0025] According to a ninth aspect of the invention, there is provided a telecommunications network comprising: at least one device of the fifth aspect of the invention; a first network node of the seventh aspect of the invention; and a second network node configured as the network node of the sixth aspect of the invention.

[0026] Brief Description of the Figures

[0027] In order that the present invention may be better understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings in which:

[0028] Figure 1 is a schematic diagram of a first wireless telecommunications network;

[0029] Figure 2 is a schematic diagram of a second wireless telecommunications network; and Figure 3 is a swimlane diagram illustrating a method of communicating in the network of Figure 2.

[0030] Detailed Description

[0031] A Rydberg atom is an atom with one or more electrons excited to a very high principal quantum number (e.g. >10). These Rydberg atoms have several useful properties, such as very large dipole moments and long lifetimes. The Rydberg atom may be used in a Rydberg-atom based ElectroMagnetic (EM) field detector. The Rydberg-atom based EM field detector is based on the Electromagnetically induced Transparency (EIT) effect. The EIT effect may be experienced when a probe signal and a coupling signal are used to elevate electrons of an atomic medium to a Rydberg state. In this state, the atomic medium becomes transparent to the probe signal. An EM field incident at the atomic medium may then cause a further transition of an electron from the Rydberg state to a further Rydberg state. Electrons may subsequently drop from the further Rydberg state to the ground state so that the atomic medium becomes less transparent to the probe signal. The EM field may therefore be detected from this change in transparency as a change in intensity of the probe signal, thus creating a Rydberg-atom based Amplitude Modulation (AM) EM detector. A more detailed explanation of this effect, and a further explanation of a Rydberg-atom based Frequency Modulation (FM) EM detector, can be found in the article, “A Multiple-Band Rydberg-Atom Based Receiver / Antenna: AM / FM Stereo Reception”, Holloway et al., National Institute of Standards and Technology). A Rydberg-atom based phase-modulated EM detector has been described in “A Rydberg Atom-Based Mixer: Measuring the Phase of a Radio Frequency Wave”, AppL Phys. Lett. 114, 114101 (2019), Holloway et al, which utilises an additional Local Oscillator (LO) signal. These Rydberg-atom based EM detectors can also be used to receive a data stream by demodulating data encoded in the detected signals, thus creating a Rydbergatom based EM receiver.

[0032] A first wireless telecommunications network 100 is illustrated in Figure 1. The first wireless telecommunications network 100 comprises a plurality of remote units (collectively 100, and in Figure 1 comprises a first remote unit 110a, second remote unit 110b and third remote unit 110c), a ground station 120 and a network controller 130.

[0033] The ground station 120 comprises a first optical source 121 configured to generate a first optical signal (hereinafter, the “probe” optical signal) and a second optical source array 123 configured to generate one or more second optical signals (hereinafter, the one or more “coupling” optical signals). These optical signals are communicated to each remote unit of the plurality of remote units 110 via one or more optical fibre connections.

[0034] Each remote unit of the plurality of remote units 110 comprises a Rydberg-atom based EM field receiver 111. The Rydberg-atom based EM field receiver of each remote unit comprises a containment of Rydberg-atoms (e.g. a containment vessel of Rubidium, Caesium or Strontium atoms) which are excited to a Rydberg-state by the probe and coupling optical signals communicated by the ground station 120. Each remote unit of the plurality of remote units 110 further comprises a photodiode 117 (for detecting / receiving the probe signal following its passage of the containment of Rydbergatoms of that remote unit) and a device 115 (for processing the detected / received probe signal).

[0035] The ground station 120 further comprises a wireless transceiver 127 for communicating with other nodes in the first wireless telecommunications network 100, such as the network controller 130.

[0036] The network controller 130 is illustrated in Figure 1 as being part of a satellite and comprises a wireless transceiver 131 for communicating with other nodes in the first wireless telecommunications network 100, such as the ground station 120.

[0037] A first method of communicating between the network controller 130 and one or more remote units of the plurality of remote units 110 of the first wireless telecommunications network 100 will now be described. In this first method, the network controller 130 wirelessly transmits a downlink communication to the ground station 120, the downlink communication being destined for at least one remote unit of the plurality of remote units 110. The ground station 120 receives the downlink communication at its wireless transceiver 127 and forwards the downlink communication via its optical connection to the or each destination remote unit via the probe and / or coupling optical signals (e.g. by modulating the data of the downlink communication to the probe and / or coupling optical signals).

[0038] There are problems with the first communication method, including:

[0039] 1 ) The ground station 120 is a single point of failure in the downlink communication between network controller 120 and the destination remote unit(s). Therefore, in the event the ground station 120 cannot participate at any point during the downlink communication (e.g. due to the ground station 120 being unpowered, over-utilised or out of range of the network controller 130), then the downlink communication fails; 2) The optica! fibre connection(s) between the ground station 120 and the or each remote unit of the plurality of remote units 110 are a contended resource. This may be undesirable if the downlink communication must not be contended; and

[0040] 3) Each remote unit of the plurality of remote units 110 has a capability to receive the downlink communication. This may be undesirable if not all remote units of the plurality of remote units can be trusted.

[0041] A second method of communicating between the network controller 130 and one or more remote units of the plurality of remote units 110 will now be described. In this second method, each remote unit that is a destination of a downlink communication from the network controller 130 comprises a wireless transceiver (based on a dipole antenna) providing that remote unit with an uplink capability to request data from the network controller 130. In response to the request, the network controller 130 wirelessly transmits the downlink communication to that remote unit. The remote unit may receive this downlink communication via the wireless transceiver and / or via the Rydberg-atom based EM field detector acting as a receiver.

[0042] There are problems with the above second communication method, including that the wireless transceiver of each remote unit consumes additional resources (e.g. energy) of the remote unit. This may be undesirable for certain types of remote units, such as those comprising an Internet-of-Things (loT) device or in any other situation in which low energy consumption is desirable.

[0043] A second wireless telecommunications network 200 will now be described with reference to Figure 2. This second wireless telecommunications network 200 comprises: a plurality of remote units (collectively 210, and in Figure 2 comprises a first remote unite 210a, a second remote unit 210b and a third remote unit 210c), a ground station 220 and a network controller 230.

[0044] The ground station 220 comprises a first optical source 221 configured to generate a probe optical signal and a second optical source 223 configured to generate one or more coupling optical signals. The probe optical signal is generated at a probe frequency and each coupling optical signal is generated at a respective coupling frequency (which will be described in more detail below). The ground station 200 further comprises a third optical source 225 configured to generate a third optical signa! (hereinafter, the “uplink” optical signal).

[0045] The third optical source 225 is configured for low cost and low transmission loss, such as by generating the uplink optical signal in any one of the optical telecommunications bands (e.g. the O-band, E-band, S-band, C-band, L-band or U-band). In one example, the uplink optical signal is generated at 1550nm. This further enables a low-cost modulator to be used at each remote unit of the plurality of remote units 210 (as described below). The uplink optical signal is also communicated to each remote unit of the plurality of remote units 210 via the one or more optical fibre connections. The ground station 220 of the second wireless telecommunications network 200 further comprises a photodiode 229 configured to receive the uplink optical signal following its passage of each remote unit of the plurality of remote units 210 (as described in more detail below).

[0046] As shown in Figure 2, each remote unit of the plurality of remote units 210 comprises a respective containment of Rydberg-atoms 211 , a respective modulator 213, a respective device 215 and a respective photodiode 217. The components of each remote unit do not need to be collocated, such that the term “remote” generally describes the distance between a collection of components of one unit being remote from a collection of components of another unit. Furthermore, the containment of Rydberg-atoms 211 of each remote unit 210 may be located in an above ground location (so as to receive electromagnetic signals transmitted by the network controller 230) but one or more of the remaining components of the remote unit may be located underwater or underground.

[0047] The probe optical signal, generated by the ground station 220, is communicated to each remote unit of the plurality of remote units 210. The probe optical signal is split from the one or more optical fibre connections so as to serially pass through each remote unit of the plurality of remote units 210. In Figure 2, it is shown that the probe optical signal passes through the first remote unit 210a, then in turn through the second remote unit 210b, then in turn through the third remote unit 210c. In each remote unit, the probe optical signal passes through the respective containment of Ryberg-atoms 211 of that remote unit so as to excite those Rydberg-atoms from a first state (e.g. a ground state) to a first excited state. Following passage of the respective containment of Rydberg- atoms 211 in each remote unit, the probe optica! signa! is thereafter split into a first path which passes to the respective photodiode 217 of that remote unit and a second path which passes to the next remote unit (e.g. from the first remote unit 210a to the second remote unit 210b via the one or more optical fibre connections).

[0048] The one or more coupling optica! signals, generated by the ground station 220, are communicated to each remote unit of the plurality of remote units 210. The one or more coupling optica! signals are split from the one or more optical fibre connections so as to serially pass through each remote unit of the plurality of remote units 210. In Figure 2, it is shown that the one or more coupling optica! signals pass through the third remote unit 210c, then in turn through the second remote unit 210b, then in turn through the first remote unit 210a. In each remote unit, the one or more coupling optica! signals pass through the respective modulator 213 of that remote unit. The respective modulator 213 of each remote unit comprises a coupling frequency filter. The coupling frequency filter is configurable so as to filter at a particular frequency (that is, to allow passage of any coupling optical signal at that particular frequency and to prevent passage of any coupling optical signal at any other frequency). The coupling frequency filter may be implemented as a Fabry-Perot cavity or an acousto-optical filter, as described, for example, in "Wavelength-tunable optical filters: applications and technologies,", H. Kobrinski et al., IEEE Communications Magazine, vol. 27, no. 10, pp. 53-63, Oct. 1989.

[0049] The coupling frequency filter may have a default configuration so as to filter at a first frequency. The one or more coupling optical signals includes a first coupling optical signal at the first frequency such that, in the default configuration, the respective modulator 213 of each remote unit allows passage of the first coupling optical signal and prevents passage of any other coupling optical signal of the one or more coupling optical signals that has a frequency that differs from the first frequency.

[0050] The frequency configuration of the coupling frequency filter of the respective modulator 213 of a particular remote unit may be configured independently of the frequency configuration of the coupling frequency filter of the respective modulator 213 of any other remote unit.

[0051] Following passage of a coupling optical signal of the one or more coupling optical signals through the respective modulator 213 of a remote unit, the coupling optical signal passes through the respective containment of Rydberg-atoms 211 of that remote unit (counterpropagating the probe optical signal) so as to excite those Rydberg-atoms which, in combination with the excitation due to the probe optical signal, causes the Rydbergatoms to be excited to a predetermined Rydberg state. The frequencies of the probe optical signal and the first coupling optical signal are set so as to excite the Rydbergatoms to a first predetermined Rydberg state. The energy difference between the first predetermined Rydberg-state and another Rydberg-state corresponds with the energy of an electromagnetic signal transmitted by the network controller 230 in a shared downlink channel, in this state, the photodiode 229 of the remote unit is able to detect (and therefore receive data) transmitted by the network controller 230 in the shared downlink channel.

[0052] Furthermore, when the one or more coupling optica! signals includes a second coupling optical signa! having a second frequency (different to the first frequency) and the coupling frequency filter of the respective modulator 213 is configured to allow passage of that second coupling optical signal at the second frequency, then the Rydberg-atoms are excited by the probe optical signal and the second coupling optical signal to a second predetermined Rydberg-state. The energy difference between the second predetermined Rydberg-state and another Rydberg-state corresponds with the energy of an electromagnetic signal transmited by the network controller 230 in a data channel. In this state, the photodiode 229 of the remote unit is able to detect (and therefore receive data) transmitted by the network controller 230 in the data channel.

[0053] The uplink optical signal, generated by the ground station 220, is communicated to each remote unit of the plurality of remote units 210. The uplink optical signal is split from the one or more optical fibre connections so as to serially pass through each remote unit of the plurality of remote units 210. In Figure 2, it is shown that the uplink optical signal passes through the third remote unit 210c, then in turn through the second remote unit 210b, then in turn through the first remote unit 210a. In each remote unit, the uplink coupling optica! signa! passes through the respective modulator 213 of that remote unit. Each respective modulator 213 of each remote unit comprises an uplink frequency modulator configured for modulating the uplink optica! signa! (such as by amplitude modulation) with an uplink data signal. The uplink frequency modulator may be implemented as a Lithium Niobate modulator with fibre tails (for example, an ElectroOptic Modulator as provided by Thorlabs Inc.). The frequency of the uplink optical signal is configured so as to avoid any interaction with the Rydberg-atoms as the uplink optical signal passes through the containment of Rydberg-atoms 211 of each remote unit. Alternatively, the uplink optical signal may follow an at least partially distinct path (to the probe and one or more coupling optical signals) so as to serially pass through each remote unit without passing through each respective containment of Rydberg-atoms 211.

[0054] The device 215 of each remote unit may be, for example, an loT device, such as a sensor, actuator, camera or robot, such that the respective devices 215 of the plurality of remote units 210 form a distributed loT network across a geographical region. The device 215 includes at least one wired electrical communications interface. The at least one wired electrical communications interface enables the device 215 to receive and process any data received at the photodiode 217. The at least one wired electrical communications interface further enables the device 215 to control the uplink modulator so as to modulate an uplink data signal to the uplink optical signal.

[0055] A method of communicating between the network controller 230 and the first remote unit 210a of the plurality of remote units 210 will now be described with reference to Figure 3. In an initial state of the second network 200, at least the first remote unit 210a of the plurality of remote units 210 is in a default state so as to receive data on the shared downlink channel. That is, the frequencies of the probe optical signal and the first coupling optical signal of the one or more coupling optical signals are set so as to excite the Rydberg-atoms of the first remote unit 210a to the first predetermined Rydberg state, wherein the energy difference between the first predetermined Rydberg state and another Rydberg state corresponds with the energy of an electromagnetic signal transmited by the network controller 230 in the shared downlink channel. One or more other remote units of the plurality of remote units 210 may also be in the default state so as to receive data on the shared downlink channel.

[0056] In step S101 , the device 215 of the first remote unit 210a sends a control signal to the uplink modulator of the modulator 213 so as to cause the uplink modulator to modulate a first data signal onto the uplink optical signal. In this example, the first uplink data signal comprises a unit identifier identifying the first remote unit 210a and a resource identifier identifying data to be downloaded. The control signal may be sent in response to the device 215 of the first remote unit 210a detecting a requirement to download the data, such as in response to an error event indicating that updated software is required. The first data signal may be considered as a request to download the data.

[0057] In step S103, the ground station 220 receives the uplink optical signal at the uplink photodiode 229. The ground station 220 is configured to implement a contention based medium access scheme so as to determine, in step S105, whether the first data signal modulated to the uplink optical signal collides with any other data signal, such as a data signal modulated to the uplink optical signal by any other remote unit of the plurality of remote units. If a collision is detected, then the first data signal (and the other data signal with which the first data signal collides) is ignored.

[0058] In this example, the first data signal does not collide with another data signal and the first data signal is successfully detected and decoded by the ground station 220. In step S107, the ground station 220 wirelessly transmits the first data signal to the network controller 230 via its wireless transceiver 227.

[0059] In step S109, the network controller 230 receives, at its wireless transceiver 231 , the first data signal and decodes the unit identifier and resource identifier contained therein. The unit identifier may be used by the network controller 230 to identify the first remote unit 210a and its associated permissions, priorities, encryption key and / or capabilities. The resource identifier may be used by the network controller 230 to identify the resource requested by the first remote unit 210a, such that the network controller 230 may prepare that resource for transmission (e.g. retrieve the resource from data storage).

[0060] In step S111, the network controller 230 determines whether to accept or reject the request of the first data signal. This determination may be based on, for example, utilisation of the network controller’s wireless transceiver 231 (or any associated resources) relative to a threshold. If rejected, then the process ends. If accepted, then, in step S113, the network controller 230 allocates a downlink resource to the first remote unit 210a, the downlink resource having an allocated frequency and allocated timeslot. The allocated frequency of the downlink resource represents the frequency of a data signal (comprising the requested data) to be transmitted by the network controller’s wireless transceiver 231 during a time period represented by the allocated timeslot. The allocated frequency is retrieved from a central pool of frequencies, which only allocates the frequency if it is not currently being used for any other purpose (such as communication between the network controller 230 and any other remote unit of the plurality of remote units 210).

[0061] In step S115, the network controller 230 sends a first configuration signal to the ground station 220 (which may be via a directional beam directed at the ground station 220), the first configuration signal comprising identifiers for the downlink resource (e.g. a frequency identifier and a timeslot identifier). In step S117, the network controller 230 sends a second configuration signal to the first remote unit 210a (which may be via a directional beam directed at the first remote unit 210a), the second configuration signal comprising the frequency identifier and remote unit identifier. The second configuration signal is transmited at the first frequency of the shared downlink channel.

[0062] In step S119, the ground station 220 receives the first configuration signal and configures a coupling frequency of a second coupling optical signal. In step S121 , the first remote unit 210a receives the second configuration signal in the shared downlink channel and configures the coupling frequency filter of the modulator 213, based on the second configuration signal, to allow passage of the second coupling optical signal at its respective frequency to the containment of Rydberg-atoms 211 (and therefore not allow passage of any other coupling optical signal having a different frequency). The coupling frequency of the second coupling optical signal is therefore configured by the ground station 220 so as to excite the Rydberg-atoms (in combination with the excitation by the probe optical signal) of the containment of Rydberg-atoms 211 of the first remote unit 210a to a predetermined Rydberg state, the predetermined Rydberg state having an energy difference with a further Rydberg state such that the electromagnetic signal transmited by the network controller 230 at the allocated frequency is detectable at the photodiode 217 of the first remote unit 210a.

[0063] In step S123, the network controller 230 transmits the data signal at the allocated frequency and during the allocated timeslot. Further, the ground station 220 continues to transmit the second coupling optical signal during the allocated timeslot. In step S125, the first remote unit 210a receives the data signal at the photodiode 217. Following expiry of the time period defined by the allocated timeslot, in step S127, the device 215 of the first remote unit 210a receives the data contained within the data signal and reconfigures its coupling frequency filter to its default configuration (corresponding with the shared downlink channel); in step S129, the ground station 220 ceases transmission of the second coupling optical signal; and, in step S131, the network controller 230 returns the allocated frequency to the central pool of frequencies (so as to be reallocated for a future communication).

[0064] For completeness, it is noted that the allocated frequency used for communication to the first remote unit 210a is not available for allocation to any other communication (e.g. between the network controller 230 and any other remote unit of the plurality of remote units 210) between its allocation to the first remote unit 210a in step S113 and its return to the central pool of frequencies in step S131.

[0065] The above method of communicating in the second network 200 provides advantages over the first and second methods of communicating in the first network 100 (described above). Firstly, the ground station’s 220 participation during the allocated timeslot is limited to the transmission of the coupling optical signal. In contrast, in the first method described above, the ground station 120 forwarded data between the network controller 130 and remote unit 110 which required the ground station to modulate this data to the signal communicated between the ground station 120 and remote unit. The ground station 220 of the second network 220 therefore does not require any downlink (i.e. ground station 220 to remote unit 210) modulator. Secondly, the one or more optical fibre connections between the ground station 220 and the plurality of remote units 210 are not a contended resource. Thirdly, the intended recipient remote unit 210 of a download is specifically configured for the download (by being tuned from the shared downlink frequency to the allocated frequency) whilst all other remote units remain at the shared downlink frequency, such that only the intended recipient remote unit 210 receives the data signal from the network controller 230. The skilled person will understand that some or all of these benefits may be realised in an alternative network comprising a single remote unit, such that the network comprising a plurality of remote units is non-essential.

[0066] The method of communicating between the network controller 230 and the first remote unit 210a may be extended to a method of communicating between the network controller 230 and a plurality of remote units 210, such as the first and second remote units 210a, 210b. In this enhancement, the first and second remote units 210a, 210b both send a request for data to the ground station 220. If these requests do not collide, then the requests are forwarded to the network controiier 230 which then allocates a first allocated frequency to the first remote unit 210a and a second allocated frequency to the second remote unit 210b (the first and second allocated frequencies being distinct and non-overlapping). The first and second remote units 210a, 210b may then simultaneously (that is, contemporaneously) receive data at their respective allocated frequencies. As the first and second remote units 210a, 210b may be configured to receive data over a very wide frequency range (by virtue of utilising a Rydberg-atom based EM receiver), then this method of communicating between the network controller 230 and a plurality of remote units 210 provides high network throughput relative to the first and second methods described above.

[0067] In a further enhancement, the data signal transmitted from the network controller 230 to a remote unit 210 may be encrypted. This may be enabled by the network controller 230 storing an encryption key of the remote unit 210. Furthermore, the configuration signals transmited by the network controller 230 may also be encrypted. This may be enabled by the ground station 220 storing the associated encryption key.

[0068] In the above description, the ground station 220 and network controller 230 cooperate to implement a contention-based reservation protocol, in which the ground station 220 determines whether a request for data from a remote unit collides with any other request, and the network controller 230 reserves a frequency forthat remote unit if the request is not contended. This protocol may be implemented, for example as a Demand Assigned Multiple Access (DAMA) system using the ALOHA protocol, but the skilled person will understand that any other contention-based reservation protocol may be used. The skilled person will also understand that the steps implemented by the ground station 220 and the network controller 230 may be implemented by a single entity.

[0069] In the above description, the network controller 230 is implemented on a satellite. This is non-essential and the network controller 230 may be implemented on any other nonterrestrial platform (e.g. High Altitude Platform) or terrestrial platform (e.g. a base station). A non-terrestrial platform is advantageous when the plurality of remote units 210 are positioned across a geographical area that may not be contained with the coverage area of a terrestrial platform. Furthermore, it is non-essential that the uplink communications interface between each remote unit and the ground station 220 is implemented as an optical communication interface. Alternatively, the upiink communications interface may be implemented as a wireless communication interface or an alternative wired communication interface (e.g. Ethernet or Digital Subscriber Line). However, this may increase the resource (e.g. energy) demands of the remote unit.

[0070] The skilled person will understand that it is non-essential that the plurality of remote units are arranged in an array. The plurality of remote units may have dedicated connections to the ground station 220 (e.g. forming a star topology).

[0071] The skilled person will understand that any combination of features is possible within the scope of the invention, as claimed.

Claims

CLAIMS1. A method of operating a device in a telecommunications network, the device comprising a Rydberg-atom based Electromagnetic (EM) signal receiver and an uplink telecommunications interface, the method comprising the steps of: configuring the Rydberg-atom based EM signal receiver to a first Rydberg state for reception at a first frequency; sending a request for data via the uplink telecommunications interface; responsive to the request for data, receiving a configuration signal, the configuration signal being received at the first frequency so as to cause a detectable change in the Rydberg-atom based EM signal receiver in the first Rydberg state, the configuration signal identifying configuration parameters for the Rydberg-atom based EM signal receiver; configuring the Rydberg-atom based EM signal receiver, according to the identified configuration parameters, to a second Rydberg state for reception at a reserved frequency; and receiving a data signal at the configured Rydberg-atom based EM signal receiver, the data signal being received at the reserved frequency so as to cause a detectable change in the Rydberg-atom based EM signal receiver in the second Rydberg state.

2. A method as claimed in Claim 1 , wherein the Rydberg-atom based EM signal receiver is one of a plurality of Rydberg-atom based EM signal receivers, each Rydberg-atom based EM signal receiver being configured in the first Rydberg state for reception at the first frequency.

3. A method as claimed in Claim 2, wherein the configuration signal comprises an identifier for the Rydberg-atom based EM signal receiver and the step of configuring the Rydberg-atom based EM signal receiver is responsive to the Rydberg-atom based EM signal receiver detecting the identifier for the Rydberg-atom based EM signal receiver in the configuration signal.

4. A method as claimed in any one of Claims 2 to 3, wherein the uplink communications interface of the Rydberg-atom based EM signal receiver utilises acommunications medium that is shared with another Rydberg-atom based EM signa! receiver of the plurality of Rydberg-atom based EM signal receivers.

5. A method of operating a network node in a telecommunications network, the telecommunications network comprising a first Rydberg-atom based Eiectromagnetic (EM) signal receiver, the method comprising the steps of: receiving a request for data from the first Rydberg-atom based EM signa! receiver; responsive thereto, reserving a first reserved frequency for communications with the first Rydberg-atom based EM signa! receiver; and sending a first configuration signa! at a first frequency to the first Rydberg-atom based EM signa! receiver, the configuration signa! identifying configuration parameters for the first Rydberg-atom based EM signa! receiver to receive a data signa! at the first reserved frequency.

6. A method as claimed in Ciaim 5, further comprising the step of: determining that the request for data from the first Rydberg-atom based EM signa! receiver is contention-free.

7. A method as claimed in Ciaim 5 or Ciaim 6, wherein the telecommunications network comprises a second Rydberg-atom based EM signal receiver, the method further comprising the steps of: receiving a request for data from the second Rydberg-atom based EM signa! receiver; responsive thereto, reserving a second reserved frequency for communications with the second Rydberg-atom based EM signal receiver; and sending a second configuration signa! at the first frequency to the second Rydberg-atom based EM signa! receiver, the configuration signal identifying configuration parameters for the second Rydberg-atom based EM signa! receiver to receive a data signa! at the second reserved frequency.

8. A method as claimed in Ciaim 7 when dependent on Ciaim 6, wherein the step of determining that the request for data from the first Rydberg-atom based EM signa! receiver is contention-free comprises determining that the request for data from the firstRydberg-atom based EM signa! receiver does not collide with the request for data from the second Rydberg-atom based EM signal receiver.

9. A method as claimed in any one of Claims 5 to 8, further comprising the step of: withdrawing reservation of the first reserved frequency for communications with the first Rydberg-atom based EM signal receiver and / or withdrawing reservation of the second reserved frequency for communications with the second Rydberg-atom based EM signal receiver.

10. A method as claimed in any one of Claims 5 to 9, wherein: the telecommunications network further comprises one or more optical sources, and the one or more optical sources communicates a plurality of optical signals to the first Rydberg-atom based EM signal receiver, the method further comprising the step of: causing configuration of the one or more optical sources according to a first configuration such that the plurality of optical signals configures the first Rydberg-atom based EM signal receiver in a first Rydberg state, wherein the first configuration signal at the first frequency causes a detectable change in the first Rydberg-atom based EM signal receiver in the first Rydberg state; and causing configuration of the one or more optical sources according to a second configuration such that the plurality of optical signals configures the first Rydberg-atom based EM signal receiver in a second Rydberg state, wherein the data signal at the first reserved frequency causes a detectable change in the first Rydberg-atom based EM signal receiver in the second Rydberg state.

11. A method as claimed in Claim 10 as dependent on Claim 7, wherein: the one or more optical sources communicates the plurality of optical signals to the second Rydberg-atom based EM signal receiver, configuration of the one or more optical sources according to the first configuration is such that the plurality of optical signals configures the second Rydbergatom based EM signal receiver in the first Rydberg-state, the second configuration signal at the first frequency causes a detectable change in the second Rydberg-atom based EM signal receiver in the first Rydbergstate, andthe one or more optical sources configured according to the second configuration is such that the plurality of optical signals configures the second Rydbergatom based EM signal receiver in a third Rydberg state, wherein the data signal at the second reserved frequency causes a detectable change in the second Rydberg-atom based EM signal receiver in the third Rydberg state.

12. A method of operating a first network node in a telecommunications network, the telecommunications network comprising a first Rydberg-atom based Electromagnetic (EM) signal receiver and a second network node, the method comprising the steps of: communicating, from one or more optical sources having a first configuration, a plurality of optical signals to the first Rydberg-atom based EM signal receiver to configure the first Rydberg-atom based EM signal receiver in a first Rydberg state for receiving at a first frequency; receiving a configuration signal, from the second network node, identifying configuration parameters for the one or more optical sources; configuring the one or more optical sources according to the received configuration parameters to have a second configuration; and communicating, from the one or more optical sources having the second configuration, the plurality of optical signals to the first Rydberg-atom based EM signal receiver to configure the first Rydberg-atom based EM signal receiver in a second Rydberg state for receiving at a first reserved frequency.

13. A method as claimed in Claim 12, wherein the telecommunications network further comprises a second Rydberg-atom based EM signal receiver and the plurality of optical signals communicated from the one or more optical sources having the second configuration are further communicated to the second Rydberg-atom based EM signal receiver to configure the second Rydberg-atom based EM signal receiver in a third Rydberg state for receiving at a second reserved frequency.

14. A method as claimed in Claim 12 or Claim 13, further comprising the steps of: receiving a request for data from the first Rydberg-atom based EM signal receiver, the request for data being received via a telecommunications interface between the first network node and the first Rydberg-atom based EM signal receiver; andsending the request for data from the first Rydberg-atom based EM signa! receiver to the second network node, wherein reception of the configuration signa! is responsive to sending the request for data from the first Rydberg-atom based EM signa! receiver to the second network node.

15. A method as claimed in Ciaim 14, further comprising the step of: determining that the request for data from the first Rydberg-atom based EM signa! receiver is contention-free.

16. A method as claimed in Ciaim 13 or any one of Claims 14 to 15 as dependent on Ciaim 13, further comprising the steps of: receiving a request for data from the second Rydberg-atom based EM signa! receiver, the request for data being received via a telecommunications interface between the first network node and the second Rydberg-atom based EM signa! receiver; and sending the request for data from the second Rydberg-atom based EM signal receiver to the second network node, wherein reception of the configuration signa! is responsive to sending the request for data from the second Rydberg-atom based EM signa! receiver to the second network node.

17. A method as claimed in Ciaim 16 when dependent on Ciaim 15, wherein determining that the request for data from the first Rydberg-atom based EM signa! receiver is contention-free comprises determining that the request for data from the first Rydberg-atom based EM signa! receiver does not coiiide with the request for data from the second Rydberg-atom based EM signa! receiver.

18. A computer program comprising: first instructions which, when the program is executed by a device, cause the device to carry out the steps of any one of Ciaims 1 to 4; second instructions which, when the program is executed by a network node, cause the network node to carry out the steps of any one of Claims 5 to 11 ; or third instructions which, when the program is executed by a first network node, cause the first network node to carry out the steps of any one of Claims 12 to 17.

19. A computer readable carrier medium comprising the computer program of Claim 18.

20. A device comprising a processor configured to carry out the steps of any one of Claims 1 to 4.

21. A network node comprising a processor configured to carry out the steps of any one of Claims 5 to 11.

22. A network node as claimed in Claim 21 as dependent on either Claim 10 or Claim 11 , comprising the one or more optical sources.

23. A first network node comprising a processor configured to carry out the steps of any one of Claims 12 to 17.

24. A telecommunications network comprising: at least one device as claimed in Claim 20; and a network node as claimed in Claim 22.

25. A telecommunications network comprising: at least one device as claimed in Claim 20; a first network node configured as the first network node of Claim 23; and a second network node configured as the network node of Claim 21 as dependent on any one of Claims 5 to 9, wherein the steps of causing configuration of the one or more optical sources comprises sending respective configuration signals to the one or more optical sources.

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