System and method for paging

Abstract

A method for paging performed by a network node in a communications network, wherein paging comprises the network node broadcasting a transmission associated with a device identifier of a first wireless device of the communications network. The device identifier of the first wireless device and a set of mappings from the device identifier of the first wireless device to a set of indices are known to the network node and the first wireless device. The method comprises creating a Bloom filter of length by adding the device identifier of the first wireless device to the Bloom filter by applying each mapping in the set of mappings to the device identifier of the first wireless device and changing the entries of the Bloom filter corresponding to the indices in the output of the mappings to 1 and broadcasting the Bloom filter.

Description

[0001] SYSTEM AND METHOD FOR PAGING

[0002] TECHNICAL FIELD

[0003] The disclosure relates generally to systems and methods for paging in a communications network and more specifically relates to using Bloom filters to page devices in a network. Further disclosed are related network nodes, wireless devices, computer programs, and computer program products.

[0004] BACKGROUND

[0005] A key component of future Internet of Things, loT, networks is loT devices with extremely low energy consumption, which are further low cost, low complexity, and with a generally small footprint. These devices are sometimes referred to as zero energy devices, to focus on the importance of developing extremely energy efficient devices. Several different technological tracks related to zero energy devices are under discussion, including passive devices based on backscattering technology. Regardless of the technology choice, it is essential to develop efficient power saving modes (i.e. sleep modes, idle modes) to achieve the desired low energy consumption. During a power saving mode, the device transmitter and receiver can be turned off to decrease energy consumption.

[0006] For loT devices, there are a number of important applications where only very infrequent transmissions are needed, such as a temperature sensor which reports temperature data on a daily basis, or a sensor which receives reconfiguration instructions on a weekly basis. Transmitting and receiving data stands for a large proportion of the total energy consumption of an loT device, so the total energy consumption can be estimated by the amount of time the device transmitter and / or receiver must be turned on for transmitting and / or receiving data or checking if there are transmissions to receive.

[0007] Some loT devices can be restricted to only use device initiated, uplink, transmissions and as such be very energy efficient, since they only need to turn on a transmitter on a pre-defined schedule to transmit data and may return to an idle mode immediately after transmission. However, such devices are limited in that they can never be reached in case network initiated, downlink, data transmissions need to be sent to the device, such as updated instructions on what task to perform or other software updates. In order to be reachable for network initiated transmissions, an loT device needs to wake up and turn on its receiver for potential messages directed to the loT device. A network defined acceptable delay for reaching the device determines how often a device needs to wake up to check for possible messages. In such a system, the total energy consumption can be estimated by how frequently a device needs to be reachable for downlink transmissions.

[0008] Cellular systems use paging to reach devices in idle modes for downlink transmissions. Taking long-term evolution, LTE / 4G, networks as an example, the time instances where a device may receive paging messages is determined by a formula specified in 3rdGeneration Partnership Program, 3GPP, Technical Specification, TS, 36.304 v17.4.0. This standard defines a paging frame, PF, and a paging occasion, PO, where the paging frame is a radio frame which may contain a paging message and the paging occasion is the sub-frame within the paging frame. The PO and PF together specify the time instances where the device may expect a paging message.

[0009] At the instances specified by the PO and the PF, the device wakes up and monitors a paging channel, in this example the physical downlink control channel, PDCCH, to check if any messages are available. If the PDCCH indicates that a paging message is available the device will demodulate the physical downlink shared channel, PDSCH, to check for which devices the paging messages are available and if it is one of the devices that has a message. In LTE, the presence of paging messages is indicated by using a specific paging ID on PDCCH. In order to determine if the device is a device that has a message waiting, the device has to decode all device IDs listed on PDSCH. In LTE, there can be up 16 IDs to decode and the ID used can be either 48 bits or 15 digits long.

[0010] Since loT devices aim to be extremely lightweight, this decoding process can be demanding and time consuming for the device. It is therefore of interest to develop a less resource-demanding method for paging.

[0011] SUMMARY

[0012] It is an object of the present disclosure to provide a system and method for resourceefficient paging in a communications system. According to a first aspect of the disclosure, there is a method performed by a network node in a communications network for paging in the communications network. Paging comprises the network node broadcasting a transmission associated with a device identifier of a first wireless device of the communications network, wherein the device identifier of the first wireless device and a set of k mappings from the device identifier of the first wireless device to a set of indices £ {0, 1}, are known to the network node and the first wireless device. The method comprises creating a Bloom filter of length n by adding the device identifier of the first wireless device to the Bloom filter by applying each mapping in the set of mappings to the device identifier of the first wireless device and changing the entries of the Bloom filter corresponding to the indices in the output of the mappings to 1 . The method further comprises broadcasting the Bloom filter. Hereby is achieved resource-efficient paging in a communications network.

[0013] According to an embodiment of the first aspect, the method further comprises adding a device identifier of a second wireless device to the Bloom filter by applying the set of mappings to the second device identifier and changing the entries of the Bloom filter corresponding to the indices in the output of the mapping to 1 .

[0014] According to an embodiment of the first aspect, the method further comprises selecting a subset of wireless devices of the communications network to page and adding the device identifier for each of the wireless devices in the subset of wireless device to the Bloom filter.

[0015] According to an embodiment of the first aspect, the method further comprises determining that the subset of wireless devices is larger than a number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter. The method further comprises dividing the subset of wireless devices into subsets, each of the subsets comprising at most m devices, and creating a Bloom filter corresponding to each subset. Hereby is achieved resource efficient paging while maintaining a low error rate.

[0016] According to an embodiment of the first aspect, the set of mappings comprises hash functions. Hereby is achieved that the Bloom filter may be calculated efficiently. According to an embodiment of the first aspect the set of mappings comprises mappings which are pairwise independent. Hereby is achieved a minimized error rate.

[0017] According to an second aspect of the disclosure, there is a method performed by a wireless device in a communications network for handling paging in the communications network. Handling the paging comprises the wireless device listening for a transmission associated with a device identifier of the wireless device, wherein the identifier of the wireless device and a set of k mappings from the device identifier of the wireless device to a set of indices is known to the network node and the wireless device. The method comprises receiving a transmission and evaluating the transmission as a Bloom filter to determine if the transmission matches the device identifier of the wireless device. If there is a match, the method comprises responding to the paging transmission, and if there is not a match, the method comprises not responding to the paging transmission. Hereby is achieved resourceefficient handling of paging transmissions.

[0018] According to an embodiment of the second aspect, the method comprises the wireless device entering a power saving mode if there is no match between the Bloom filter and the device identifier. Hereby active time for the device is minimized, achieving further energy savings.

[0019] According to an embodiment of the second aspect, not responding to the transmission comprises entering a power saving mode at the first entry in the Bloom filter corresponding to an output of the set of mappings which is not 1 . Hereby is achieved that a sleep mode may be entered even faster, further reducing energy use.

[0020] According to a third aspect of the disclosure, there is a method for paging in a communications network. The method is performed by a system comprising a network node and at least one wireless device, wherein each wireless device Wthas an identifier known to the wireless device and the network node and a set of mappings from the device identifiers of the wireless devices to a set of indices ItQ {0, ... , n - 1} is known to the network node and the wireless devices. The method comprises the network node creating a Bloom filter of length n by applying each mapping to each device identifier and changing the entries of the Bloom filter corresponding to the indices in the output of the mapping to 1. The method further comprises the network node broadcasting the Bloom filter. The method further comprises the at least one wireless devices receiving a broadcast. The method further comprises the at least one wireless devices evaluating the transmission as a Bloom filter to determine if the transmission matches the device identifier. The method further comprises the at least one wireless devices, if there is a match between the Bloom filter and the device identifier, responding to the paging transmission. The method further comprises the at least one wireless devices, if there is not a match between the Bloom filter and the device identifier, not responding to the transmission.

[0021] According to an embodiment of the third aspect, the method further comprises the network node selecting a subset of wireless devices of wireless devices of the system to page and the network node adding the device identifier for each of the wireless devices in the subset of wireless device to the Bloom filter.

[0022] According to an embodiment of the third aspect, the method further comprises the network node determining that the subset of wireless devices is larger than some number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter. The method further comprises the network node dividing the subset of wireless devices into subsets, each of the subsets comprising at most m devices and the network node creating one Bloom filter corresponding to each subset.

[0023] According to an embodiment of the third aspect, the set of mappings comprises k hash functions.

[0024] According to an embodiment of the third aspect, the mappings are pairwise independent.

[0025] According to an embodiment of the third aspect the method further comprises the at least one wireless devices entering a power saving mode if there is no match between the Bloom filter and the device identifier.

[0026] According to an embodiment of the third aspect, not responding to the transmission comprises the at least one wireless device entering a power saving mode at the first entry in the Bloom filter corresponding to an output of the set of mappings which is not 1 .

[0027] According to a fourth aspect of the disclosure, there is a network node, where the network node has access to a device identifier for at least one wireless device and a set of k mappings from the device identifier of the first wireless device to a set of indices c {o, ... , n - 1}. The network node is configured to create a Bloom filter of length n by adding a device identifier of a first wireless device to the Bloom filter, wherein adding a device identifier to the Bloom filter comprises applying each mapping in a set of k mappings to the device identifier and changing the entries of the Bloom filter corresponding to the output of the mappings to 1 . The network node is further configured to broadcast the Bloom filter.

[0028] According to an embodiment of the fourth aspect, the network node is further configured to add a device identifier of a second wireless device to the Bloom filter by applying the each mapping in the set of k mappings to the second device identifier and changing the entries of the Bloom filter corresponding to the output of the mappings to 1 .

[0029] According to an embodiment of the fourth aspect, the network node is further configured to select a subset of wireless device of the communications network to page and add the device identifier for each of the wireless devices in the selected subset to the Bloom filter.

[0030] According to an embodiment of the fourth aspect, the network node is further configured to determine that the subset of wireless devices is larger than a number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter. The network node is further configured to divide the subset of wireless devices into subsets, each of the subsets comprising at most m devices and create a Bloom filter corresponding to each subset.

[0031] According to an embodiment of the fourth aspect, the set of mappings comprises hash functions.

[0032] According to an embodiment of the fourth aspect, the set of mappings comprises mappings which are pairwise independent. According to an embodiment of the fourth aspect, the network node comprises a radio access node.

[0033] According to a fifth aspect of the disclosure, there is a wireless device, WD, in a communications network, where the WD has a device identifier and a set of k mappings from the device identifier of the first wireless device to a set of indices £ {0, ...,n - 1}. The WD is configured to receive a paging transmission and evaluate the transmission as a Bloom filter to determine if the transmission contains a device identifier of the WD. If there is a match, the WD is configured to respond to the paging transmission and if there is not a match, not respond to the paging transmission.

[0034] According to an embodiment of the fifth aspect, the WD is further configured to enter a power saving mode if there is no match between the Bloom filter and the device identifier.

[0035] According to an embodiment of the fifth aspect, not responding to the transmission comprises entering a power saving mode at the first entry in the Bloom filter not matching the device identifier.

[0036] According to an embodiment of the fifth aspect, the WD is an Internet of Things, loT, device.

[0037] According to a sixth aspect of the disclosure, there is a system comprising a network node and at least one wireless device, WD, where a device identifier of the at least one WD and a set of k mappings from the device identifier of the first wireless device to a set of indices / xc {0, ..., n - 1} are known to the WD and the network node. The system is configured to the network node creating a Bloom filter of length n by adding a device identifier of a first wireless device to the Bloom filter, wherein adding a device identifier comprises applying each mapping in a set of k mappings to the device identifier and changing the entries of the Bloom filter corresponding to the output of the mappings to 1 . The system is further configured to the network node broadcasting the Bloom filter and the at least one WDs receiving a broadcast. The system is further configured to the at least one WD evaluating the transmission as a Bloom filter to determine if the transmission matches the device identifier. The system is further configured to the at least one WD, if there is a match between the Bloom filter and the device identifier, responding to the paging transmission; and the at least one WD, if there is not a match between the Bloom filter and the device identifier, not responding to the paging transmission.

[0038] According to an embodiment of the sixth aspect, the system is further configured to the network node selecting a subset of WDs of the WDs of the system to page, and the network node adding the device identifier for each of the WDs in the subset of wireless devices to the Bloom filter.

[0039] According to an embodiment of the sixth aspect the system is further configured to the network node determining that the subset of WDs is larger than some number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter. The system is further configured to the network node dividing the subset of WDs into subsets, each of the subsets comprising at most m devices and the network node creating one Bloom filter corresponding to each subset.

[0040] According to an embodiment of the sixth aspect, the set of mappings comprises k hash functions.

[0041] According to an embodiment of the sixth aspect, the mappings are pairwise independent.

[0042] According to an embodiment of the sixth aspect, the system is further configured so that the at least one WDs enter a power saving mode if there is no match between the Bloom filter and the device identifier.

[0043] According to an embodiment of the sixth aspect, the system is further configured so that the at least one WDs enter a power saving mode at the first entry in the Bloom filter corresponding to an output of the set of mappings which is not 1 .

[0044] According to an embodiment of the sixth aspect, the network node comprises a radio access node and the WDs comprise at least one Internet of Things, loT, device.

[0045] According to a seventh aspect of the disclosure, there is a computer program comprising instructions which, when executed by the processor of a network node or a wireless device, causes the network node or the wireless device to perform a method according to any embodiment of the first through third aspect. According to an eighth aspect of the disclosure, there is a computer program product comprising a computer readable storage medium on which a computer program according to the seventh aspect is stored.

[0046] The technical advantages of the first aspect and the second aspect also apply to the third through eighth espects, mutatis mutandis.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Fig. 1 depicts a flowchart of a method according to the disclosure.

[0049] Fig. 2 depicts a flowchart of a method according to the disclosure.

[0050] Fig. 3 depicts a flowchart of a method according to the disclosure.

[0051] Fig. 4 is a diagram of message exchanges according to an embodiment of the disclosure.

[0052] Fig. 5 is a diagram of message exchanges according to an embodiment of the disclosure.

[0053] Fig. 6 is a communication system according to and embodiment of the disclosure.

[0054] Fig. 7 is a network node according to an embodiment of the disclosure.

[0055] Fig. 8 is a wireless device according to an embodiment of the disclosure.

[0056] Fig. 9a depicts calculations of an error rate of a method of the disclosure.

[0057] Fig. 9b depicts calculations of an error rate of a method of the disclosure.

[0058] Fig. 9c depicts calculations of an error rate of a method of the disclosure.

[0059] Fig. 9d depicts calculations of an error rate of a method of the disclosure.

[0060] DETAILED DESCRIPTION

[0061] Fig. 1 depicts an embodiment of a first method 100 according to the disclosure. The first method is a method performed by a network node in a communication network for paging in the communication network. A communication network is a group of network nodes interconnected by telecommunications links that are used to exchange messages between the network nodes. In embodiments of the disclosure, the communication network is a wireless radio network. The wireless radio network may be a network according to any suitable standard as defined by the 3rdgeneration partnership program, 3GPP, such as Global System for Mobile Communications, GSM, Universal Mobile Telecommunications System, UMTS, Long-Term Evolution, LTE, 5G New Radio, 5G NR, or any future standard. Alternatively, the communication network may be a local area network, LAN, Wi-Fi network according to a suitable Institute of Electrical and Electronics Engineers, IEEE, standard. Alternatively or in addition, the communications network may be a hybrid telecommunications / Wi-Fi network. Alternatively, the communications network may be defined according to any other standard. The communications network may be a public network, accessible to any wireless device in the vicinity of a network node, or it may be a private network such as a private 5G network set up for a specific facility and only available to devices belonging to that facility.

[0062] The network node may for example be a radio access node in a mobile communications network such as a NodeB in a UMTS network, an eNodeB in an LTE network, a gNodeB in a 5G NR network, a radio access node according to any future standard, or it may be a Wi-Fi access point in a Wi-Fi network.

[0063] Paging in a communications network is a method by which a network node may initiate a downlink transmission to a wireless device such as an Internet of Things, loT, device or a user equipment, UE. A communication device in the form of an loT device may be a device for use in one or more application domains, these domains comprising, but not limited to, home, city, wearable technology, extended reality, industrial application, and healthcare.

[0064] By way of example, the loT device for a home, an office, a building or an infrastructure may be a baking scale, a coffee machine, a grill, a fridge, a refrigerator, a freezer, a microwave oven, an oven, a toaster, a water tap, a water heater, a water geyser, a sauna, a vacuum cleaner, a washer, a dryer, a dishwasher, a door, a window, a curtain, a blind, a furniture, a light bulb, a fan, an air-conditioner, a cooler, an air purifier, a humidifier, a speaker, a television, a laptop, a personal computer, a gaming console, a remote control, a vent, an iron, a steamer, a pressure cooker, a stove, an electric stove, a hair dryer, a hair styler, a mirror, a printer, a scanner, a photocopier, a projector, a hologram projector, a 3D printer, a drill, a hand-dryer, an alarm clock, a clock, a security camera, a smoke alarm, a fire alarm, a connected doorbell, an electronic door lock, a lawnmower, a thermostat, a plug, an irrigation control device, a flood sensor, a moisture sensor, a motion detector, a weather station, an electricity meter, a water meter, and a gas meter.

[0065] By further ways of example, the loT device for use in a city, urban, or rural areas may be connected street lighting, a connected traffic light, a traffic camera, a connected road sign, an air control / monitor, a noise level detector, a transport congestion monitoring device, a transport controlling device, an automated toll payment device, a parking payment device, a sensor for monitoring parking usage, a traffic management device, a digital kiosk, a bin, an air quality monitoring sensor, a bridge condition monitoring sensor, a fire hydrant, a manhole sensor, a tarmac sensor, a water fountain sensor, a connected closed circuit television, a scooter, a hoverboard, a ticketing machine, a ticket barrier, a metro rail, a metro station device, a passenger information panel, an onboard camera, and other connected device on a public transport vehicle.

[0066] As further way of example, the communication loT device may be a wearable device, or a device related to extended reality, wherein the device related to extended reality may be a device related to augmented reality, virtual reality, merged reality, or mixed reality. Examples of such loT devices may be a smart-band, a tracker, a haptic glove, a haptic suit, a smartwatch, clothes, eyeglasses, a head mounted display, an ear pod, an activity monitor, a fitness monitor, a heart rate monitor, a ring, a key tracker, a blood glucose meter, and a pressure meter.

[0067] As further ways of example, the loT device may be an industrial application device wherein an industrial application device may be an industrial unmanned aerial vehicle, an intelligent industrial robot, a vehicle assembly robot, and an automated guided vehicle.

[0068] As further ways of example, the loT device may be a transportation vehicle, wherein a transportation vehicle may be a bicycle, a motor bike, a scooter, a moped, an auto rickshaw, a rail transport, a train, a tram, a bus, a car, a truck, an airplane, a boat, a ship, a ski board, a snowboard, a snow mobile, a hoverboard, a skateboard, rollerskates, a vehicle for freight transportation, a drone, a robot, a stratospheric aircraft, an aircraft, a helicopter and a hovercraft. As further ways of example, the loT device may be a health or fitness device, wherein a health or fitness device may be a surgical robot, an implantable medical device, a non-invasive medical device, and a stationary medical device which may be: an in-vitro diagnostic device, a radiology device, a diagnostic imaging device, and an x-ray device.

[0069] The communication network may comprise a plurality of loT devices and other wireless devices of varied types and usage areas. For example, a communication network in a hospital setting may comprise UEs in the form of personal mobile phones belonging to staff and / or patients, medical devices for diagnostic purposes, sensing devices for the purpose of collecting patient health data, security devices such as surveillance cameras, fire alarms, and smoke alarms, environmental sensors such as temperature and humidity sensors for the purpose of maintaining a pleasant internal climate, and connected office equipment comprising everything from connected printers to smart coffee makers.

[0070] Paging comprises the network node broadcasting a paging message in a communications channel.

[0071] In an embodiment, the paging message may be a paging message in an LTE system, as defined in TS 36.331 v10.22.0 section 6.2.2. In this embodiment, the paging message is sent on the PCCH logical channel mapped to the PDSCH physical channel. Such a paging message is depicted below.

[0072] Paging messsage

[0073] — ASN1START

[0074] Paging : : = SEQUENCE { pagingRecordList PagingRecordList OPTIONAL, — Need ON systemlnfoModifi cation ENUMERATED { true } OPTIONAL, — Need ON etws- Indi cation ENUMERATED { true } OPTIONAL, — Need ON nonCriticalExtension Paging-v890-IEs OPTIONAL

[0075] }

[0076] Paging-v890-IEs SEQUENCE { lateNonCriticalExtension OCTET STRING OPTIONAL,

[0077] Need OP nonCriticalExtension Paging- v920- I Es OPTIONAL

[0078] }

[0079] Paging-v920-IEs : : = SEQUENCE { cmas-Indication-r9 ENUMERATED { true } OPTIONAL, — Need ON nonCriticalExtension SEQUENCE { } OPTIONAL — Need OP

[0080] PagingRecordList : : = SEQUENCE ( SIZE ( 1 . . maxPageRec ) ) OF PagingRecord

[0081] PagingRecord : : = SEQUENCE { ue-Identity PagingUE-Identity, cn-Domain ENUMERATED { ps , cs } , PagingUE-Identity : : = CHOICE { s-TMSI S-TMSI , imsi IMSI ,

[0082] }

[0083] IMSI : : = SEQUENCE ( SIZE ( 6 . . 21 ) ) OF IMSI-Digit

[0084] IMSI-Digit : : = INTEGER ( 0 . . 9 )

[0085] — ASN1ST0P

[0086] Different communications channels may be used for sending paging information and paging indications in different embodiments of the invention. The person skilled in the art will note that the method of the invention is not dependent on paging methods according to any specific standard, and references to GSM, LTE, and 5G NR paging are used solely as illustrative examples in the detailed description. In embodiments such as LTE systems, control channels such as PDSCH and the physical downlink control channel, PDCCH, may be used to transmit paging information. In GSM, paging messages are sent in the paging channel, PCH. Alternatively, the message may be sent in a general purpose communication channel, possibly with a preamble indicating that it is a paging message. The paging message is in some way associated with a device identifier of the at least one device the network node wants to initiate a downlink transmission with. A device identifier of a wireless device may be a string of characters associated to a unique device or to a set of devices (for example a set of identical sensors which act “as one” and may thus be treated as a single entity by the network). The properties of the device identifier may be defined in a suitable standard. In 5G NR networks, the ID used for paging is typically a 48 bit 5G shortened temporary mobile subscription identity, 5G-S-TMSI, defined in European Telecommunications Standards Institute, ETSI, TS 123 003 V16.5.0 or an international mobile subscriber identity, IMSI, defined in International Telecommunications Union, ITU, Recommendation E.212 (9 / 16). The IMSI is typically a string of at most 15 digits that uniquely identifies every user of a mobile network. For the purposes of the present disclosure, the ID used for paging may be a general purpose identifier according to any current or future standard, or an identifier developed specifically to be used to implement the methods of the present disclosure. The device ID is known to both the device and the network node.

[0087] Information about the device ID may be directly managed by the network node, or it may be managed by a separate function which the network node can query about the identity of a specific device or set of devices as needed.

[0088] In addition to a device ID, the methods of the present disclosure require that a set of k independent mappings from the device ID to a set of indices is known to both the device and the network node. The mappings are mathematical functions on the discrete space of device IDs, mapping a device ID to a number. The range of the mappings may be the set {0, ...,n - 1}. The mappings may be defined in any suitable manner. The mappings may, for example, comprise a table listing the mappings. In other embodiments, the mappings may comprise hash functions satisfying the requirements on domain and range of the mapping.

[0089] It may be advantageous to choose mappings and a means of defining the mappings which requires as little computing power and memory space as possible, to minimize the demands placed on an loT device which needs to store and execute the mappings.

[0090] The first method 100 comprises creating 101 a Bloom filter of length n by adding the device identifier of the first device to the Bloom filter. Adding the device identifier of the first device to the Bloom filter comprises applying the k mappings to the device identifier of the first wireless device and changing the entries of the Bloom filter corresponding to the indices in the output of the mappings to 1 .

[0091] A Bloom filter is a space-efficient probabilistic data structure used for testing whether an element is a member of a specific set. For the purpose of this disclosure, the Bloom filter is used to determine whether a specific device ID is present in the paging message. Bloom filters are space-efficient in the sense that they can encode membership in a set in considerably shorter message than listing all of the device IDs, and the device IDs are all encoded in the same n bits instead of listing them in some order. The probabilistic property of Bloom filters refers to a chance of false positive matches (i.e. a device falsely believing that there is a message waiting for it where there is not one). Bloom filters have no probability of false negatives, so there is no risk of a device missing a message. In general, a Bloom filter of length 10m can encode membership information for elements with a 1% false probability rate, independent of the size of individual elements or the number of elements in the set (Bonomi et. al., (2006) “An Improved Construction for Counting Bloom Filters”, Algorithms - ESA 2006, 14thAnnual European Symposium).

[0092] The Bloom filter of this method is of length n, that is, comprising n bits for some natural number n. In embodiments of the present disclosure, n may be 256. To create a Bloom filter, the network node first initiates a bit array, list, vector, or other suitable data structure which can hold an ordered list of binary decision variables such as Boolean variables. The data structure may be initiated with all entries set to 0, False, or other indications of the Boolean 0. The initiated list may be referred to as an empty Bloom filter. To add the first device ID to the Bloom filter, the network node applies the mappings to the device ID of the first wireless device. This may comprise looking up the corresponding outputs in a table, or performing mathematical calculations using the device ID as input in a function. The functions may be hash functions.

[0093] In some embodiments, the k mappings are pairwise independent. Independent, in the context of the present disclosure, refers to the outputs of the mappings being uncorrelated in order to avoid collisions between the outputs of the mappings and thus to minimize the rate of false positives. There is extensive literature on the task of choosing suitable mappings for Bloom filters. For example, a good general purpose hash function with low correlation between the input bits may be chosen, and the independent hash functions obtained by slicing the output of the single hash function into the required number of bit fields. If n is larger relative to the number of device IDs to be encoded in the hash filter, the independence requirement may be relaxed somewhat without obtaining a prohibitively large number of false positives (see e.g. Dillinger and Manolios, (2004) “Bloom Filters in Probabilistic Verification”, Proceedings of the 5thInternational conference on Formal Methods in Computer- Aided Design, Springer-Verlag, Lecture Notes in Computer Science 3312).

[0094] The output of the mappings applied to the first device ID is a set / x£ {0, 1} which may be referred to as a set of indices. The output set is of some fixed size k equal to the number of mappings. Considering Bonomi et. al., the fixed size k may be selected to be less than 10 in some embodiments. To add the device ID to the Bloom filter, the network node sets the Bloom filter entry indexed by each of the indices in the output of the mappings to 1, True, or any other indication of the Boolean 1. The person skilled in the art will note that using the indexing set {0, ...,n - 1} to index the entries in the Bloom filter is completely arbitrary and only adhered to in the present disclosure to avoid inconsistent notation - some implementations of the methods of the disclosure may use other indexing sets such as {1, depending on the specifics of the computing environment without affecting the inventive concept. In general, the elements of an n-element Bloom filter may be indexed by any indexing set J of size n. The person skilled in the art will note that initiating the Bloom filter with all elements equal to 0 and changing them to 1 is also arbitrary. Any choice of variable capable of indicating presence / no presence may be used. The Bloom filter may for instance equivalently be initiated to all Is and changed to a 0 to indicate presence. Alternatively, any other variable values could be used.

[0095] By way of a simplified example, suppose the Bloom filter is of length 5 and the set of mappings comprises two mappings such that the output of the mappings when applied to the first device ID is the set {1,3}. That is, applying a first mapping to the device ID yields the output 1 and applying a second mapping to the device ID yields the output 3. The Bloom filter would be initialized to [0,0, 0,0,0] and adding the first device ID to the Bloom filter comprises changing the entries of the filter indexed by 1 and 3 to 1, obtaining the Bloom filter encoding the membership of the first device ID as [0,1, 0,1,0],

[0096] The method 100 further comprises broadcasting 102 the Bloom filter. The Bloom filter may be broadcast in a channel specifically for paging, such as the PCH channel. Alternatively, the Bloom filter may be broadcast in a general purpose channel. In some embodiments, the Bloom filter may be preceded by a preamble indicating that it is a Bloom filter based paging message. In some embodiments, the Bloom filter may be broadcast in a specific time frame associated with paging messages. The frame associated with paging messages may be determined by a suitable standard document from a standardization organization such as 3GPP, or it may be defined when setting up a specific private network according to delay tolerances for specific types of devices. By way of example, some sensors may be classed as low importance and only listen for paging messages once every 48 hours, while other devices may perform more critical tasks and listen for paging messages every 4 hours.

[0097] The first method may further comprise adding a device identifier of a second wireless device to the Bloom filter. In some embodiments of the method, the network node will need to page more than one device at the same time. In such embodiments, the network node will select 103 a subset of wireless devices in the network. For each device in the selected subset, the network node will add the device identifier to the Bloom filter. Adding a second device comprises applying the mappings to the device ID of the second device, obtaining a second subset of indices. For each index in the second subset, the corresponding entry in the Bloom filter is set to 1.

[0098] Returning to the very simplified example, after adding the first device ID to the Bloom filter, the Bloom filter is set to [0,1, 0,1,0], Applying the mappings to the second device ID may yield the index set {0,1}. Adding the second device ID to the Bloom filter thus comprises changing the first entry and the second entry to 1. Note that the second entry is already set to 1, so it does not have to be modified to add the second device ID. The Bloom filter encoding the device ID of the first device and the device ID of the second device is thus [1,1, 0,1,0],

[0099] The first method may further comprise determining 104 that the subset of wireless device is larger than some number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device IDs are added to the Bloom filter. As noted above, Bloom filters are probabilistic structures and as such may provide false matches. By way of example, suppose there is a third device in the network associated to the simple Bloom filter in the example above. This third device is not added to the Bloom filter. However, applying the mapping to the device ID of the third device yields the index set {0,3}. Hence, if the Bloom filter [l,l,0,l,0] is broadcast and the third device checks whether it is included in the Bloom filter, the third device finds that the 0thand 3rdindex are both set to 1 and erroneously assumes there is a message waiting for the third device. Such an event is called a false positive. The risks of false positives can be minimized by carefully choosing appropriate mappings as discussed above, and by not adding too many device IDs to each Bloom filter.

[0100] A number of methods exist by which one can estimate the probability of a false positive in a Bloom filter. A simple approximation may be obtained by assuming complete independence between each bit in the mappings and that each bit is equally likely to be selected as the output of a mapping. If the Bloom filter is of length n and there are k mappings, then the probability that a specific bit of the Bloom filter is not set to 1 by any of the mappings can be estimated as (1 - Using the well- known limit expression for exp(-l), this can be estimated as exp (-fc / n). If i items have been inserted into the Bloom filter, the probability that a certain bit of the Bloom filter is still 0 is thus approximately exp -ki / ri) and the probability that the specific bit is 1 is thus approximated as 1 - exp (-fci / n) . Hence, given a device ID which is not in the filter, the probability that each of the indices in the output from the mappings is set to 1, i.e. there is a false positive, can be approximated as:

[0101] / / ki\\ke 1 - exp l -— . (Eq. 1) \ \ n ) )

[0102] More precise estimates for the probability of false positives without the independence assumption are known, such as the estimate: where (”) denotes Stirling numbers of the second kind, are known from e.g. Gopinathan and Sergey, (2020) “Certifying Certainty and Uncertainty in Approximate Membership Query Structures”, Computer Aided Verification, Lecture Notes in Computer Science, Springer Verlag. For a given maximum error rate, the person skilled in the art may thus solve for i to obtain a maximum number m of device ID which may be added to the Bloom filter without exceeding the maximum error rate.

[0103] Alternatively, the person skilled in the art may run simulations to determine an estimate for the rate of false positives and iteratively increase / decrease the number of device IDs per Bloom filter until an error rate suitable for the application is reached.

[0104] In embodiments, the first method may further comprise dividing 105 the subset of devices to be paged into subsets, each of the subsets comprising at most m devices. In embodiments, the subsets may be disjoint subsets. In embodiments, the first method may further comprise creating 106 one Bloom filter for each subset. In embodiments, the first method may further comprise broadcasting 102 each of the Bloom filters.

[0105] Fig. 2 depicts a second method 200 for handling paging in a communications network. The second method is performed by a wireless device in a communications network. In embodiments, the wireless device is an loT device. The second method comprises the wireless device listening for a transmission associated with a device ID of the wireless device. In embodiments, the listening for a transmission may be performed at specific points in time. In embodiments, the device may be in a low- energy mode, a sleep mode, or an idle mode when not listening for a transmission. The specific points in time may be set by a telecommunications standard, or they may be specific to the local network the device is a part of. The device ID is known to the device and to a network node in the network that broadcasts paging messages, such as a radio access node or a Wi-Fi access point.

[0106] Additionally, a set of k mappings from the device ID to a set of indices are known to the device and the network node. The mappings may in embodiments be selected to be simple to calculate or look up for the device, since the device may be a low- energy or zero-energy loT device.

[0107] The second method comprises receiving 201 a transmission. In embodiments, the transmission may have a preamble telling the device that it is a paging message according to the methods of the disclosure. In other embodiments, the message may be received at a time when the device only expects paging messages according to the methods of the disclosure. In other embodiments the device is notified on a control channel that there is a potential paging message to be received. The paging notification can be done by including a paging identifier on the control channel or scrambling the control channel with a paging specific code.

[0108] The second method further comprises evaluating 202 the transmission as a Bloom filter to determine if the transmission matches the device identifier of the wireless device. Evaluating the transmission as a Bloom filter comprises checking if the indices resulting from applying the mappings to the device ID are set to 1 . In some embodiments, evaluating the transmission as a Bloom filter comprises only evaluating the transmission if it has a preamble indicating that it is a Bloom filter based paging message. In other embodiments, evaluating the transmission as a Bloom filter comprises only evaluating the transmission if it is transmitted at a time associated with Bloom filter based paging messages. In other embodiments, the device will evaluate every received transmission as a Bloom filter.

[0109] Evaluating the transmission comprises applying the mappings to the device ID to obtain a set of k indices indicating positions in the Bloom filter. Evaluating the transmission further comprises checking each of the k positions corresponding to the indices to see if the position contains a 1, the value True, or some other suitable indication of a true Boolean variable. Checking each of the k positions may be performed by any suitable algorithm.

[0110] If each of the k positions contains the number 1, there is a positive match for the Bloom filter and the second method comprises the device responding 203 to the paging transmission. Responding to the paging transmission may comprise demodulating a channel to receive a transmission. The channel to be demodulated may be specified by a suitable telecommunications standard. For example, in 4G LTE communications, a device will demodulate the physical downlink shared channel, PDSCH, in response to receiving a paging transmission. In some embodiments, the message may be transmitted in the same channel as the paging message and the device may simply continue demodulating the same channel as the paging message was received in to receive the message.

[0111] In some embodiments, the positive match may be a false positive match. In such embodiments, the device will still perform the task of responding to the paging transmission. In some embodiments, such as those based on LTE / NR, the device will, on finding the false positive, continue trying to set up a connection with a network node to receive the message. This may comprise, for example, transmitting an RRC connection request message to the network node based on the paging message. However, since there was no paging message from the network, the network node will reject the RRC connection request. Alternatively, in some embodiments, there may be a lightweight protocol for transmitting paging messages whereby the data message is transmitted directly after the paging message for the relevant devices to decode. However, since there is no message intended for the device, the device may, in embodiments, be unable to demodulate the channel to receive the message. In other embodiments, the device may receive a message with information or instructions intended for a different device.

[0112] Alternatively, the device may find that at least one of the entries in the Bloom filter corresponding to an index output from the mappings is not set to 1. In such embodiments, the device may stop 204 evaluating the transmission. The second method may comprise stopping the evaluation of the Bloom filter at the first index which is not set to 1, or it may comprise evaluating the complete filter and simply taking no action if at least one index is not set to 1. When the device stops evaluating the Bloom filter may be selected by the implementer when choosing a suitable algorithm to evaluate the Bloom filter. In some embodiments, the device may enter 205 a low energy mode such as a sleep mode or an idle mode immediately on stopping the evaluation of the Bloom filter.

[0113] Fig. 3 depicts a third method 300 according to the disclosure. The third method is a method for paging in a telecommunications system performed by a system comprising a network node and at least one wireless device. Associated to each wireless device is a device identifier known to the wireless device and the network node. Moreover, a set of k mappings from the device ID to a set of indices is known to both the wireless devices and the network node. The third method comprises the network node creating 301 a Bloom filter of length n by applying each mapping to each device ID and changing the entries of the Bloom filter corresponding to the indices in the output of the mappings to 1. The third method further comprises the network node broadcasting 302 the Bloom filter. The third method further comprises the at least one wireless devices receiving 303 a broadcast. Typically, the broadcast comprises the Bloom filter. The third method further comprises the at least one wireless devices evaluating 304 the transmission as a Bloom filter to determine if the transmission matches the device identifier. The third method further comprises the at least one wireless devices, if there is a match between the Bloom filter and the device identifier, responding 305 to the paging transmission. The third method further comprises the at least one devices, if there is not a match between the Bloom filter and the device identifier, not responding 306 to the transmission. In some embodiments of the disclosure, not responding may comprise not sending an RRC connection request or similar message to the network node. In other embodiments of the disclosure, not responding may comprise not attempting to demodulate a data message following the paging message.

[0114] In some embodiments of the disclosure the RRC connection request message is followed by further signalling to establish a connection, for example an RRC connection setup message sent from the network which could also contain data intended for the device. In other embodiments the paging message may include a request to perform a pre-defined action for example to read the system information channel or to display an earthquake and sunami warning as specified in 3GPP for LTE.

[0115] In embodiments of the third method, the method may further comprise the network node selecting 307 a subset of wireless devices of the system to page. The selected subset may be selected based on a need to communicate information to devices in the subset. Alternatively or in addition, the choice of subset may be based on a standard of the system which specifies which devices will be listening for a paging transmission at the time when the transmission will be sent.

[0116] In some embodiments of the third method, the method may further comprise the network node determining 308 that the selected subset of wireless devices is larger than some number m where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter. In such embodiments, the method may further comprise the network node dividing 309 the selected subset of wireless devices into subsets, where each subset comprises at most m devices. In such embodiments, the method may further comprise the network node creating 310 one Bloom filter corresponding to each subset. In some embodiments, the network may monitor the number of false positives and adjust the number k during operation if the number of false positives rise above some threshold.

[0117] In some embodiments, the one or more wireless devices may enter 311 a low energy mode such as a sleep mode or an idle mode immediately on stopping the evaluation of the Bloom filter.

[0118] Fig. 4 depicts an exemplary flow of communication between a wireless device and a network node in the case where there is a message for the wireless device according to an embodiment of a method according to the disclosure. The flow of messages may be initiated by the network node transmitting 401 a paging notification to all nodes listening in a specific timeslot. The paging notification may, for example, be performed by encoding the PDCCH channel with a paging ID. In some embodiments, the paging ID may be a paging radio network temporary identifier, PRNTI. On receipt of the paging notification, the wireless device will wait 402 for an incoming paging message, such as an RRC paging message, comprising a Bloom filter to check if there is a paging for the wireless device. The network node will create 403 the Bloom filter based on device IDs corresponding to wireless devices which are being paged in the current timeslot. The network node transmits 404 the paging message comprising the Bloom filter. The Bloom filter is received by the wireless device, which evaluates 405 the Bloom filter and finds a positive match. The wireless device transmits a request 406, such as an RRC connection request message, for a message for the device ID associated to the wireless device to the network node. The network node then finds 407 the queued message for the requested device ID and sends 408 the queued message to the wireless device.

[0119] Fig. 5 depicts an exemplary flow of communication between a wireless device and a network node in the case where there is no message for the wireless device in a scenario where there is a false positive match between the transmitted Bloom filter and the device ID. In this scenario, steps 501-506 are identical to respective corresponding step of steps 401 -406 where there is a message for the device. However, on receiving a message request for a message associated to the device ID of the wireless device, the network node find 507 no queued message for the requested device ID. In this scenario, the device may respond with some indication 508 that there is no message waiting for the device.

[0120] Fig. 6 depicts an exemplary communication system 600 according to an embodiment of the disclosure. The communication system may comprise a host 601 in communication with a core network 606 comprised in a telecommunication network 602. The core network may further comprise one or more core network nodes 608. The core network may be in communication with network nodes 610A, 610B in an access network 604. The network nodes, in turn, may communicate directly with UEs 612A, 612B or with a hub 614 which communicates with UEs 612C, 612D.

[0121] Fig. 7 depicts an exemplary network node 700 according to an embodiment of the disclosure. The network node may perform any embodiment of the first method of the disclosure, be a part of a system according to embodiments of the third method of the disclosure, or partake in an exchange of messages as described in Fig. 4 and Fig. 5. The network node may comprise a communication interface 706 which in turn may comprise an antenna 710, radio front-end circuitry 718 comprising a radio filter 720 and an amplifier 722, and a port or terminal 716. The communication interface may communicate with processing circuitry 705 comprising radio frequency transceiver circuitry 712 and baseband circuitry 714. The processing circuitry may further have access to a memory 704. The processing circuitry, memory, and communication interface may have access to a power source 708. In some embodiments, the network node may be a virtual network node or open radio access network node. The memory may further comprise a computer program product 726 comprising a computer program 724 in the form of computer readable instructions, which, when executed by the processor, cause the network node to perform methods according to any embodiment of the first method according to the disclosure.

[0122] Fig. 8 depicts an exemplary wireless device 800 according to an embodiment of the disclosure. The wireless device may be a UE or an loT device. The wireless device may perform any embodiment of the second method of the disclosure, be a part of a system according to the third method of the disclosure, or partake in an exchange of messages according to Fig. 4 or Fig. 5. The wireless device may comprise processing circuitry 802, a bus 804, an input / output interface 806, a power source 808, a memory 810 comprising application programs 814 and data 816, a communication interface 812 comprising a transmitter 818 and a receiver 820, and an antenna 822. The memory may further comprise a computer program product 826 comprising a computer program 824 in the form of computer readable instructions which, when executed by a processor, cause the wireless device to perform methods according to any embodiment of the second method according to the disclosure.

[0123] Fig. 9a depicts the outputs of a calculation of false positives of a method according to the disclosure. The table depicts the estimated number of false positive values using Eq. 1 out of 10 000 devices when the length of the Bloom filter is set to 768 bits. The rows correspond to inserting 16, 32, and 48 device IDs in the filter respectively. The first, second, and third column respectively correspond to the false positive rate with 3, 4, and 5 mappings. The fourth column lists the mathematically optimal value of the number of mappings k = ln(2) n / m obtained by minimizing Eq. 1 , followed by the probability of a false positive using the optimal number of mappings and the expected number of false positives.

[0124] Fig. 9b depicts the same calculations using a Bloom filter of length 512.

[0125] Fig. 9c depicts the same calculations using a Bloom filter of length 256, with additional rows corresponding to smaller number of inserted device IDs.

[0126] Fig. 9d depicts the calculations for breaking the 768 bit Bloom filter into three subfilters, each sub-filter of length 256, and adding 16 device IDs to each sub-filter compared to using a single 768 bit Bloom filter with 48 device IDs. As can be seen from this take, the number of false positives is equal for the case where a single longer filter is used compared to using several shorter filters, which may indicate to the person skilled in the art that some implementations may use a single longer filter over multiple shorter filters to page a large number of devices. The person skilled in the art may therefore choose to use a variable filter length depending on the number of devices the network node may need to page in a specific time slot without losing accuracy.

Claims

CLAIMS1 . A method (100) performed by a network node in a communications network for paging in the communications network, wherein paging comprises the network node broadcasting a transmission associated with a device identifier of a first wireless device of the communications network, wherein the device identifier of the first wireless device and a set of k mappings from the device identifier of the first wireless device to a set of indices£ {0, ... , n - 1], are known to the network node and the first wireless device, the method comprising: creating (101 ) a Bloom filter of length n by adding the device identifier of the first wireless device to the Bloom filter by applying each mapping in the set of mappings to the device identifier of the first wireless device and changing the entries of the Bloom filter corresponding to the indices in the output of the mappings to 1 ; and broadcasting (102) the Bloom filter.

2. The method (100) according to claim 1 , further comprising adding a device identifier of a second wireless device to the Bloom filter by applying the set of mappings to the second device identifier and changing the entries of the Bloom filter corresponding to the indices in the output of the mapping to 1 .

3. The method (100) according to claim 1 or 2, further comprising: selecting (103) a subset of wireless devices of the communications network to page; and adding the device identifier for each of the wireless devices in the subset of wireless device to the Bloom filter.

4. The method (100) according to claim 3, further comprising: determining (104) that the subset of wireless devices is larger than a number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter; dividing (105) the subset of wireless devices into subsets, each of the subsets comprising at most m devices; andcreating (106) a Bloom filter corresponding to each subset.

5. The method (100) according to any one of claims 1 -4, wherein the set of mappings comprises hash functions.

6. The method (100) according to any one of claims 1 -5 wherein the set of mappings comprises mappings which are pairwise independent.

7. A method (200) performed by a wireless device in a communications network for handling paging in the communications network, wherein handling the paging comprises the wireless device listening for a transmission associated with a device identifier of the wireless device, wherein the identifier of the wireless device and a set of k mappings from the device identifier of the wireless device to a set of indices is known to the network node and the wireless device, the method comprising: receiving (201 ) a transmission; evaluating (202) the transmission as a Bloom filter to determine if the transmission matches the device identifier of the wireless device; if there is a match, responding (203) to the paging transmission; and if there is not a match, not responding (204) to the paging transmission.

8. The method (200) according to claim 7, further comprising the wireless device entering (205) a power saving mode if there is no match between the Bloom filter and the device identifier.

9. The method (200) according to claim 7 or 8, wherein not responding to the transmission comprises entering a power saving mode at the first entry in the Bloom filter corresponding to an output of the set of mappings which is not 1 .

10. A method (300) for paging in a communications network, the method performed by a system comprising a network node and at least one wireless device, wherein each wireless device Wthas an identifier known to the wireless device and the network node and a set of mappings from the device identifiers of the wireless devices to a set of indices It£ {0, ...,n - 1} is known to the network node and the wireless devices, the method comprising:the network node creating (301 ) a Bloom filter of length n by applying each mapping to each device identifier and changing the entries of the Bloom filter corresponding to the indices in the output of the mapping to 1 ; the network node broadcasting (302) the Bloom filter; the at least one wireless devices receiving (303) a broadcast; the at least one wireless devices evaluating (304) the transmission as a Bloom filter to determine if the transmission matches the device identifier; the at least one wireless devices, if there is a match between the Bloom filter and the device identifier, responding (305) to the paging transmission; and the at least one wireless devices, if there is not a match between the Bloom filter and the device identifier, not responding (306) to the transmission.11 . The method (300) according to claim 10, further comprising: the network node selecting (307) a subset of wireless devices of wireless devices of the system to page; and the network node adding (301 ) the device identifier for each of the wireless devices in the subset of wireless device to the Bloom filter.

12. The method (300) according to claim 11 , further comprising: the network node determining (308) that the subset of wireless devices is larger than some number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter; the network node dividing (309) the subset of wireless devices into subsets, each of the subsets comprising at most m devices; the network node creating (310) one Bloom filter corresponding to each subset.

13. The method (300) according to any one of claims 10-12, wherein the set of mappings comprises k hash functions.

14. The method (300) according to any one of claims 10-13 wherein the mappings are pairwise independent.

15. The method (300) according to any one of claims 10-1 , further comprising the at least one wireless devices entering (311 ) a power saving mode if there is no match between the Bloom filter and the device identifier.

16. The method (300) according to any one of claims 10-15, wherein not responding to the transmission comprises the at least one wireless device entering (311 ) a power saving mode at the first entry in the Bloom filter corresponding to an output of the set of mappings which is not 1 .

17. A network node (700), where the network node has access to a device identifier for at least one wireless device and a set of k mappings from the device identifier of the first wireless device to a set of indices / x£ {0, ...,n - 1}, the network node configured to: create a Bloom filter of length n by adding a device identifier of a first wireless device to the Bloom filter; wherein adding a device identifier to the Bloom filter comprises applying each mapping in a set of k mappings to the device identifier and changing the entries of the Bloom filter corresponding to the output of the mappings to 1 ; and; broadcast the Bloom filter.

18. The network node (700) according to claim 17, further configured to add a device identifier of a second wireless device to the Bloom filter by applying the each mapping in the set of k mappings to the second device identifier and changing the entries of the Bloom filter corresponding to the output of the mappings to 1 .

19. The network node (700) according to claim 17 or 18, further configured to: select a subset of wireless device of the communications network to page; and add the device identifier for each of the wireless devices in the selected subset to the Bloom filter.

20. The network node (700) according to claim 19, further configured to: determine that the subset of wireless devices is larger than a number m, where m is related to an error rate e such that the expected false positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter; divide the subset of wireless devices into subsets, each of the subsets comprising at most m devices; and create a Bloom filter corresponding to each subset.

21. The network node (700) according to any one of claims 17-20, wherein the set of mappings comprises hash functions.

22. The network node (700) according to any one of claims 17-21 , wherein the set of mappings comprises mappings which are pairwise independent.

23. The network node (700) according to any one of claims 17-22, wherein the apparatus comprises a radio access node.

24. A wireless device (800), WD, where the WD has a device identifier and a set of k mappings from the device identifier of the first wireless device to a set of indices £ {o, ... , n - 1], the WD configured to: receive a paging transmission; evaluate the transmission as a Bloom filter to determine if the transmission contains a device identifier of the WD; if there is a match, responding to the paging transmission; and if there is not a match, not responding to the paging transmission.

25. The WD (800) according to claim 24, wherein the WD is further configured to enter a power saving mode if there is no match between the Bloom filter and the device identifier.

26. The WD (800) according to claim 24 or 25, wherein not responding to the transmission comprises entering a power saving mode at the first entry in the Bloom filter not matching the device identifier.

27. The WD (800) according to any one of claims 23-26, wherein the WD is an Internet of Things, loT, device.

28. A system (600) comprising a network node (700) and at least one wireless device (800), WD, where a device identifier of the at least one WD and a set of k mappings from the device identifier of the first wireless device to a set of indices A £ {0, ... , n - 1} are known to the WD and the network node, the system configured to: the network node creating a Bloom filter of length n by adding a device identifier of a first wireless device to the Bloom filter; wherein adding a device identifier comprises applying each mapping in a set of k mappings to the device identifier and changing the entries of the Bloom filter corresponding to the output of the mappings to 1 ; the network node broadcasting the Bloom filter; the at least one WDs receiving a broadcast; the at least one WD evaluating the transmission as a Bloom filter to determine if the transmission matches the device identifier; the at least one WD, if there is a match between the Bloom filter and the device identifier, responding to the paging transmission; and the at least one WD, if there is not a match between the Bloom filter and the device identifier, not responding to the paging transmission.

29. The system (600) according to claim 28, further configured to: the network node (700) selecting a subset of WDs of the WDs of the system to page; and the network node (700) adding the device identifier for each of the WDs in the subset of wireless devices to the Bloom filter.

30. The system (600) according to claim 29, further configured to: the network node (700) determining that the subset of WDs is larger than some number m, where m is related to an error rate e such that the expectedfalse positive rate for the Bloom filter exceeds e if more than m device identifiers are added to the Bloom filter; the network node (700) dividing the subset of WDs into subsets, each of the subsets comprising at most m devices; the network node (700) creating one Bloom filter corresponding to each subset.31 . The system (600) according to any one of claims 28-30, wherein the set of mappings comprises k hash functions.

32. The system (600) according to any one of claims 28-31 , wherein the mappings are pairwise independent.

33. The system (600) according to any one of claims 28-32, wherein the system is further configured so that the at least one WDs (800) enter a power saving mode if there is no match between the Bloom filter and the device identifier.

34. The system (600) according to any one of claims 28-33, wherein the system is further configured so that the at least one WDs (800) enter a power saving mode at the first entry in the Bloom filter corresponding to an output of the set of mappings which is not 1 .

35. The system (600) according to any one of claims 28-34, wherein the network node (700) comprises a radio access node and the WDs (800) comprise at least one Internet of Things, loT, device.

36. A computer program (724) comprising instructions which, when executed by a processor of a network node, causes the network node device to perform a method according to any one of claims 1-6.

37. A computer program product (726) comprising a computer readable storage medium on which a computer program (724) according to claim 36 is stored.

38. A computer program (824) comprising instructions which, when executed by a processor of a wireless device, causes the wireless device to perform a method according to any one of claims 7-9.

39. A computer program product (826) comprising a computer readable storage medium on which a computer program (824) according to claim 38 is stored.

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