Method, apparatus and computer program

Abstract

Method of determining an order of an array of passive wireless internet of things (IOT) tags, comprising: activating pairs of tags of the group in a phase sweep sequence 412; receiving responses from

Description

FIELD The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to determining the order of tags in a tag array. BACKGROUND Passive or Ambient Internet of Things (A-loT) devices are devices that operate without a dedicated power source. A passive device may harness energy from wireless signals sent on specific carriers and / or bandwidths and charge a simple circuitry that, once activated, may emit / reflect a signal which encodes at least the ID of the passive radio. An example system architecture around a passive device comprises an activator (a device that sends an activation signal targeted at waking up the passive radio device), a passive device (which harnesses energy over a range of frequencies and listens for activation signals; when an activation signal is detected, the passive radio emits / reflects a signal which is specific to that device) and a reader device (that listens and detects the passive radio signals). The reader may or may not be collocated with the activator. The number of loT connections has been growing rapidly in recent years and is predicted to be hundreds of billions by 2030. With more and more ‘things’ expected to be interconnected, there remains a need for further developments in this field. SUMMARY According to an aspect, there is provided a controller comprising means for: configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence; configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence; receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; and based on the information indicating the power level, determining an order of the tags in the group of tags. Configuring the activator device may comprise configuring the activator device to activate a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases, wherein the different phases are selected based on information indicating a phase shift capability of the second tag. The controller may further comprise means for: receiving, from the reader device, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal received by the reader device for each of the pairs of tags may comprise, for each tag pair, the power level of the combined signal received by the reader device for each of the different phases in the phase sweep sequence. Configuring the activator device and the reader device may comprise sending, to the activator device and the reader device, information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Configuring the activator device may comprise sending a resource allocation to the activator device for activating each pair of tags. Configuring the reader device may comprise sending a resource allocation to the reader device for receiving the signals from each pair of tags. Determining the order of the tags in the group of tags may comprise: determining, for each tag pair, a phase difference setting between the tags corresponding to the highest power level of the combined signal; and determining the order of the tags based on the determined phase difference settings. Determining the order of the tags based on the determined phase difference settings may comprise: determining a first tag pair having the highest power level of the combined signal associated with the smallest set of similar phase difference settings between the tags as being the tag pair with the greatest separation. Determining the order of the tags based on the determined phase difference settings may further comprise: determining one or more further pairs of tags having the highest power level of the combined signal associated with the next smallest set of phase difference settings between the tags as being the tag pair with the next largest separation; and repeating the determining for the remaining tag pairs for each next largest phase difference until all tag pairs have been determined. Determining the order of tags based on the determined phase difference settings may comprise: determining, for each tag pair, a second order approximation based on the information indicating the power level of the combined signal received by the receiver for each phase setting in the phase sweep sequence; determining phase difference values for each tag pair based on the second order approximation; and determining the placement order based on the determined second order approximations. Determining the placement order based on the determined second order approximations may comprise: determining a first tag pair having the highest power level of the combined signal associated with a smallest set of similar phase difference values as being the tag pair with the largest separation; and determining a second and third tag pair having the highest power level of the combined signal associated with the next smallest set of similar phase difference values as being tag pairs with the next largest separation. The controller may further comprise means for: storing the determined order of the tags with information associated with the group of tags. The controller may further comprise means for: determining a tag group phase setting selection based on the determined order of the tags; and sending, to the activator device and the reader device, information indicating the determined tag group phase setting selection. According to an aspect there is provided an activator device comprising means for: receiving, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; and activating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. Activating the tag pairs may comprise activating a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases. Receiving the configuration may further comprise receiving information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Receiving the configuration may further comprise receiving a resource allocation to the activator device for activating each pair of tags. The activator device may further comprise means for: receiving, from the controller, information indicating a tag group phase setting selection. According to an aspect there is provided a reader device comprising means for: receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence; receiving, from each of pairs of tags according to the received configuration, a combined signal; and sending, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. The reader device may further comprise means for: receiving, from each of the tags in the group of tags, information indicating a phase shift capability of the tag; and sending, to the controller, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal for each of the pairs of tags may comprise, for each tag pair, information indicating the power level of the combined signal for a plurality of different phases in a phase sweep sequence. The configuration may further comprise information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Receiving the configuration may further comprise receiving a resource allocation for receiving the signals from each pair of tags. According to an aspect, there is provided a controller comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the controller at least to: configure an activator device for activating each pair of tags in a group of tags in a phase sweep sequence; configure a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence; receive, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; and based on the information indicating the power level, determine an order of the tags in the group of tags. The at least one processor may be further configured to cause the controller to configure the activator device to activate a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases, wherein the different phases are selected based on information indicating a phase shift capability of the second tag. The at least one processor may be further configured to cause the controller to: receive, from the reader device, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal received by the reader device for each of the pairs of tags may comprise, for each tag pair, the power level of the combined signal received by the reader device for each of the different phases in the phase sweep sequence. The at least one processor may be further configured to cause the controller to send, to the activator device and the reader device, information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. The at least one processor may be further configured to cause the controller to send a resource allocation to the activator device for activating each pair of tags. The at least one processor may be further configured to cause the controller to send a resource allocation to the reader device for receiving the signals from each pair of tags. The at least one processor may be further configured to cause the controller to: determine, for each tag pair, a phase difference setting between the tags corresponding to the highest power level of the combined signal; and determine the order of the tags based on the determined phase difference settings. The at least one processor may be further configured to cause the controller to: determine a first tag pair having the highest power level of the combined signal associated with the smallest set of similar phase difference settings between the tags as being the tag pair with the greatest separation. The at least one processor may be further configured to cause the controller to: determine one or more further pairs of tags having the highest power level of the combined signal associated with the next smallest set of phase difference settings between the tags as being the tag pair with the next largest separation; and repeat the determining for the remaining tag pairs for each next largest phase difference until all tag pairs have been determined. The at least one processor may be further configured to cause the controller to: determine, for each tag pair, a second order approximation based on the information indicating the power level of the combined signal received by the receiver for each phase setting in the phase sweep sequence; determine phase difference values for each tag pair based on the second order approximation; and determine the placement order based on the determined second order approximations. The at least one processor may be further configured to cause the controller to: determine a first tag pair having the highest power level of the combined signal associated with a smallest set of similar phase difference values as being the tag pair with the largest separation; and determine a second and third tag pair having the highest power level of the combined signal associated with the next smallest set of similar phase difference values as being tag pairs with the next largest separation. The at least one processor may be further configured to cause the controller to: store the determined order of the tags with information associated with the group of tags. The at least one processor may be further configured to cause the controller to: determine a tag group phase setting selection based on the determined order of the tags; and send, to the activator device and the reader device, information indicating the determined tag group phase setting selection. According to an aspect, there is provided an activator device comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the activator device at least to: receive, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; and activate the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. The at least one processor may be further configured to cause the activator device to activate a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases. The at least one processor may be further configured to cause the activator device to receive information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. The at least one processor may be further configured to cause the activator device to receive a resource allocation to the activator device for activating each pair of tags. The at least one processor may be further configured to cause the activator device to: receive, from the controller, information indicating a tag group phase setting selection. According to an aspect, there is provided a reader device comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the reader device at least to: receive, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence; receive, from each of pairs of tags according to the received configuration, a combined signal; and send, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. The at least one processor may be further configured to cause the reader device to: receive, from each of the tags in the group of tags, information indicating a phase shift capability of the tag; and send, to the controller, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal for each of the pairs of tags may comprise, for each tag pair, information indicating the power level of the combined signal for a plurality of different phases in a phase sweep sequence. The configuration may further comprise information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. The at least one processor may be further configured to cause the reader device to receive a resource allocation for receiving the signals from each pair of tags. According to an aspect, there is provided a method performed by a controller, the method comprising: configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence; configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence; receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; and based on the information indicating the power level, determining an order of the tags in the group of tags. Configuring the activator device may comprise configuring the activator device to activate a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases, wherein the different phases are selected based on information indicating a phase shift capability of the second tag. The method may further comprise: receiving, from the reader device, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal received by the reader device for each of the pairs of tags may comprise, for each tag pair, the power level of the combined signal received by the reader device for each of the different phases in the phase sweep sequence. Configuring the activator device and the reader device may comprise sending, to the activator device and the reader device, information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Configuring the activator device may comprise sending a resource allocation to the activator device for activating each pair of tags. Configuring the reader device may comprise sending a resource allocation to the reader device for receiving the signals from each pair of tags. Determining the order of the tags in the group of tags may comprise: determining, for each tag pair, a phase difference setting between the tags corresponding to the highest power level of the combined signal; and determining the order of the tags based on the determined phase difference settings. Determining the order of the tags based on the determined phase difference settings may comprise: determining a first tag pair having the highest power level of the combined signal associated with the smallest set of similar phase difference settings between the tags as being the tag pair with the greatest separation. Determining the order of the tags based on the determined phase difference settings may further comprise: determining one or more further pairs of tags having the highest power level of the combined signal associated with the next smallest set of phase difference settings between the tags as being the tag pair with the next largest separation; and repeating the determining for the remaining tag pairs for each next largest phase difference until all tag pairs have been determined. Determining the order of tags based on the determined phase difference settings may comprise: determining, for each tag pair, a second order approximation based on the information indicating the power level of the combined signal received by the receiver for each phase setting in the phase sweep sequence; determining phase difference values for each tag pair based on the second order approximation; and determining the placement order based on the determined second order approximations. Determining the placement order based on the determined second order approximations may comprise: determining a first tag pair having the highest power level of the combined signal associated with a smallest set of similar phase difference values as being the tag pair with the largest separation; and determining a second and third tag pair having the highest power level of the combined signal associated with the next smallest set of similar phase difference values as being tag pairs with the next largest separation. The method may further comprise: storing the determined order of the tags with information associated with the group of tags. The method may further comprise: determining a tag group phase setting selection based on the determined order of the tags; and sending, to the activator device and the reader device, information indicating the determined tag group phase setting selection. According to an aspect there is provided a method performed by an activator device, the method comprising: receiving, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; and activating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. Activating the tag pairs may comprise activating a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases. Receiving the configuration may further comprise receiving information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Receiving the configuration may further comprise receiving a resource allocation to the activator device for activating each pair of tags. The method may further comprise: receiving, from the controller, information indicating a tag group phase setting selection. According to an aspect there is provided a method performed by a reader device, the method comprising: receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence; receiving, from each of pairs of tags according to the received configuration, a combined signal; and sending, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. The method may further comprise: receiving, from each of the tags in the group of tags, information indicating a phase shift capability of the tag; and sending, to the controller, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal for each of the pairs of tags may comprise, for each tag pair, information indicating the power level of the combined signal for a plurality of different phases in a phase sweep sequence. The configuration may further comprise information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Receiving the configuration may further comprise receiving a resource allocation for receiving the signals from each pair of tags. According to an aspect, there is provided a computer readable medium comprising instructions which, when executed by a controller, cause the controller to perform at least the following: configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence; configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence; receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; and based on the information indicating the power level, determining an order of the tags in the group of tags. Configuring the activator device may comprise configuring the activator device to activate a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases, wherein the different phases are selected based on information indicating a phase shift capability of the second tag. The instructions, when executed, may cause the controller to further perform: receiving, from the reader device, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal received by the reader device for each of the pairs of tags may comprise, for each tag pair, the power level of the combined signal received by the reader device for each of the different phases in the phase sweep sequence. Configuring the activator device and the reader device may comprise sending, to the activator device and the reader device, information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Configuring the activator device may comprise sending a resource allocation to the activator device for activating each pair of tags. Configuring the reader device may comprise sending a resource allocation to the reader device for receiving the signals from each pair of tags. Determining the order of the tags in the group of tags may comprise: determining, for each tag pair, a phase difference setting between the tags corresponding to the highest power level of the combined signal; and determining the order of the tags based on the determined phase difference settings. Determining the order of the tags based on the determined phase difference settings may comprise: determining a first tag pair having the highest power level of the combined signal associated with the smallest set of similar phase difference settings between the tags as being the tag pair with the greatest separation. Determining the order of the tags based on the determined phase difference settings may further comprise: determining one or more further pairs of tags having the highest power level of the combined signal associated with the next smallest set of phase difference settings between the tags as being the tag pair with the next largest separation; and repeating the determining for the remaining tag pairs for each next largest phase difference until all tag pairs have been determined. Determining the order of tags based on the determined phase difference settings may comprise: determining, for each tag pair, a second order approximation based on the information indicating the power level of the combined signal received by the receiver for each phase setting in the phase sweep sequence; determining phase difference values for each tag pair based on the second order approximation; and determining the placement order based on the determined second order approximations. Determining the placement order based on the determined second order approximations may comprise: determining a first tag pair having the highest power level of the combined signal associated with a smallest set of similar phase difference values as being the tag pair with the largest separation; and determining a second and third tag pair having the highest power level of the combined signal associated with the next smallest set of similar phase difference values as being tag pairs with the next largest separation. The instructions, when executed, may cause the controller to further perform: storing the determined order of the tags with information associated with the group of tags. The instructions, when executed, may cause the controller to further perform: determining a tag group phase setting selection based on the determined order of the tags; and sending, to the activator device and the reader device, information indicating the determined tag group phase setting selection. According to an aspect, there is provided a computer readable medium comprising instructions which, when executed by an activator device, cause the activator device to perform at least the following: receiving, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; and activating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. Activating the tag pairs may comprise activating a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases. Receiving the configuration may further comprise receiving information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Receiving the configuration may further comprise receiving a resource allocation to the activator device for activating each pair of tags. The instructions, when executed, may cause the activator device to further perform: receiving, from the controller, information indicating a tag group phase setting selection. According to an aspect, there is provided a computer readable medium comprising instructions which, when executed by a reader device, cause the reader device to perform at least the following: receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence; receiving, from each of pairs of tags according to the received configuration, a combined signal; and sending, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. The method may further comprise: receiving, from each of the tags in the group of tags, information indicating a phase shift capability of the tag; and sending, to the controller, the information indicating the phase shift capability of each of the tags in the group of tags. The information indicating the power level of the combined signal for each of the pairs of tags may comprise, for each tag pair, information indicating the power level of the combined signal for a plurality of different phases in a phase sweep sequence. The configuration may further comprise information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags. Receiving the configuration may further comprise receiving a resource allocation for receiving the signals from each pair of tags. According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to perform at least the method according to any of the preceding aspects. In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above. DESCRIPTION OF FIGURES Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which: Figure 1 shows an example system architecture; Figure 2 shows methods according to some examples; Figures 3 and 4 show signalling exchanges according to some examples; Figure 5 shows some example simulation results; Figure 6 shows an example 2nd order approximation for some values shown in Figure 5; and Figure 7 shows example estimated delta phase values. DETAILED DESCRIPTION The scope of protection sought for various embodiments of the disclosure is set out by the independent claims. The embodiments and features, if any, described in the specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the disclosure. Figure 1 shows an example system architecture around a passive device comprising an activator 100, a passive device 102 and a reader device 104. In operation, the activator 100 emits an activation signal 106 which is received by the passive device 102. The passive device 102 harnesses the energy from the activation signal and emit / reflects a further signal 108 that is specific to the passive device 102 (e.g. is modulated based on an identifier of the passive device 102). The further signal 108 is received by the reader 104. As used herein, the further signal 108 may be referred to as a backscatter signal. Passive devices may be categorised into one of three categories based on the passive device’s capabilities: Type A: No energy storage, no independent signal generation / amplification, e.g., backscattering transmission. Type B: Has energy storage, no independent signal generation, e.g., backscattering transmission, with use of stored energy for amplification for reflected signals. Type C: Has energy storage, has independent signal generation, e.g., active RF components for transmission. For A-loT device type A and B (which may be referred to herein as tags or A-loT tags) the activation range may be limited to a few meters (e.g. up to 10 meters) depending on the efficiency and gain of the activator and the A-loT tag. As such the activator may need to be in proximity to the A-loT Tag, while the reader / readers may be located further away. As such, the activator can be a handheld or mobile UE (e.g. a robot mounted UE), while readers may be positioned at fixed positions. For example, in a stock warehouse scenario where stock items are provided with a tag, the activator may be a robot traversing the warehouse and sending activation signals to activate the tags on the stock items and the readers may be located in the ceiling. Multiple readers can be used to estimate the location of individual stock items based on triangularization techniques. However it may be prohibitive to have large numbers of readers scattered around the warehouse (e.g. for cost reasons), and consequently while the Activator to A-loT Tag distance may be relatively short, the A-loT Tag to reader distance may be significantly longer. However, as the A-loT devices do not have a power source and rely on backscattering, the effective range of the signal emitted / reflected by the A-loT device may be somewhat limited. Thus the number of readers required in the warehouse may depend on the realizable A-loT Tag to reader backscatter link budget. As such, improvement of the A-loT Tag to reader link budget may have a direct impact on the cost of the asset tracking system implementation. One solution to this problem is to mount a plurality of small size and low-cost A-loT Tags (in a Tag group) on the asset to be tracked and by this enable backscatter reflection power gain in the direction of the reader to improve the link budget compared to a single Tag through beamforming techniques. Procedures for optimizing the backscatter reflection gain of a Tag group in the direction of the reader include adjusting the reflection phase setting for each Tag in the group such that the signals emitted / reflected by each tag in the group interfere constructively in the direction of the reader. In some implementations of the placement order of the Tags in the group may be unknown. As such, all possible combinations of Tag reflection phase settings may need to be swept to identify the optimum gain constellation towards each active A-loT reader. The placement order of the A-loT Tags in the Tag-Array may be important for configuring the optimum codebook, with a limited number of beam configurations. Sweeping all possible combinations may work well for small Tag arrays with limited number of phase settings but for larger Tag arrays with high phase shifter resolution it may be beneficial from a resource overhead and latency point of view to obtain information about the order of the Tags in the array constellation. Some examples of the present disclosure provide solutions for determining the relative placement order of A-loT Tags configured for Tag-array operation in order to reduce the number of used sweep combinations. Reference is made to Figure 2, which shows methods according to some examples. At 200, a method comprises configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence. At 202 the method comprises configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence. At 204 the method comprises receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence. At 206, the method comprises, based on the information indicating the power level, determining an order of the tags in the group of tags. In some examples, steps 200-206 may be performed at or by a controller. At 208, a method comprises receiving, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence. At 210, the method comprises activating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. In some examples steps 208-210 may be performed at or by an activator device. At 212, a method comprises receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence. At 214, the method comprises receiving, from each of pairs of tags according to the received configuration, a combined signal. At 216, the method comprises sending, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. In some examples steps 212-216 may be performed at or by a reader device. Reference is made to Figure 3, which shows a signalling exchange according to some examples. The signalling exchange shown in Figure 3 may be for optimizing the reflection gain of a group of tags (herein also referred to as a tag array) comprising tags A-D, where initially the placement order of the A-loT Tags in the Tag-Array is unknown. As such the Tag phase patterns must be configured to traverse all relevant phase setting combinations during the beam sweeping steps 308-312 in Figure 3. At 300, a controller, such as a session control unit (SCU), obtains information on the group of A-loT tags. The information may comprise for example a group identifier and capability information for each tag in the group. The capability information may for example comprise information indicating a number of phase shifts that the tag is able to apply and / or what those phase shift values are (e.g., a tag may be able to perform 8 possible phase shifts of 0°, 45°, 90°, 135°, 180°, 225°, 270° &315°). At 302, the controller may configure the activator with information relating to the group of A-loT tags. For example, the controller may configure the activator with identifiers of each of the tags and / or the group identifier. The controller may configure the activator with information indicating the activation signal needed for each tag. At 304, the activator configures each tag in the group with phase pattern information for performing group phase sweeping. For example, the activator may configure the tags such that the tags cycles through all possible phase shifts for all possible phase combinations of the group of tags. For example, in a 1:4 tag array with two phase shift settings per tag, there are 8 different phase combinations (e.g., {A1 B1 C1 D1}, {A1 B1 C1 D2}, {A1 B1 C2 D1} etc., where A1 denotes a first phase shift setting for tag A and A2 denotes a second phase shift setting for tag A, and so on). As shown in Figure 3, optionally each tag in the group may confirm the receipt of the configuration by emitting / reflecting a tag specific signal to the reader. The reader may then send an indication of the confirmation to the controller. At 306 the controller configures the activator and one or more readers with information for performing tag group beam sweeping. For example, the activator may configure the reader(s) with resource allocation information relating to the activation signal and backscatter signal(s) associated with the tag group. At 308 the activator sends, to the tags, an activation signal. At 310, the readers receive, from each of the tags, a backscatter signal with phase shifts applied according to the configuration at 304. At 312, based on the received backscatter signals, the readers measure a combined group signal for each tag group activation. Steps 308-312 are then repeated for each phase combination in the tag group. At 314, the readers send a reporting message to the controller indicating the measured group signal information for each tag group activation. At 316, the controller selects the best tag group phase settings for reaching the different readers (which may or may not be different for each reader). In the example signalling exchange of Figure 3, steps 308-312 are repeated for each phase combination in the tag group. For example, in a 1:4 tag array with two phase shift settings per tag, there are 8 different phase combinations in the tag group; and in a 1:4 tag array with three phase shift settings per tag there are 27 different phase combinations in the tag group. For larger number of Tags in the Tag group and / or higher resolution A-loT Tag phase shifters (that is, tags capable of more phase shift settings), the number of tag group phase sweeps required may increase further and may become unmanageably large. As an example, for a 1:4 Tag-Array with 3-bit phase shifters the number of constellation sweeps grows to 512. The signalling overhead required for the activator to send the activation signals and the receivers to receive and process the tag specific signals and the latency caused by repeating the process so many times may be prohibitively large. In some examples of the present disclosure, a Tag-Array Tag order identification procedure is provided which may be executed once (for example before initiating the procedure described in Figure 3) and may significantly reduce the number of tag group phase sweeps required. In some examples the order of the tags in a tag array may be derived by sequentially evaluating randomly selected pairs of A-loT Tags in the Tag-Array. In some examples the activator may configure a first tag to perform a phase sweep and configure a second tag of with a static phase while the first tag performs a phase sweep. During the phase sweep the reader may measure the received combined power from the first and second tags (a “tag pair”). These combined power values for each pair of tags in the array may then be used to derive the placement order of the A-loT Tags in the Tag-Array, which will be discussed in further detail below. For example, in an array of four tags, {A,B,C,D}, the tag pairs may be: AB, AC, AD, BC, BD, CD. The activator may configure tag A with a static phase while tag B performs a phase sweep, and the reader may measure the received combined power from the pair of AB. This process may be repeated for the remaining tag pairs, and the reader may send the measured received combined power for all tag pairs to the controller. In some examples (for example when the reader is in a boresight angular direction of the Tag-Array) the procedure may not result in a conclusive placement order. In such examples the controller may either: Assign a different Reader within coverage of the Tag-Array to determine the order of the A-loT Tags in the Tag-Array; or Have the Activator configure the Tag-Array for boresight operation until the location of the Tag-Array and / or Reader has changed sufficiently for the Reader to determine the order of the A-loT Tags in the Tag-Array. In some examples the assigned Reader may experience poor signal conditions (e.g., due to bad Signal to Interference and Noise Ratio (SINR)) it might not receive the combined signals from the A-loT Tag-Array. In such cases the Reader may signal to the controller that the reader has been unable to receive the signals. The signalling may for example comprise a negative acknowledgment (NACK) message. When the controller only receives a few valid received power values from the Reader, the controller may conclude that the session might have been interrupted by interference during the A-loT Tag pair sweeping procedure. For example, when 5 to 7 valid received power values from the Reader for an eight-stat sweeping procedure are expected but only 2 received power values are received, the controller may conclude that interference has occurred. Reference is made to Figure 4, which shows a signalling exchange according to some examples. In some examples it may be assumed that the controller knows the ID of the individual A-loT Tags intended to be used in the Tag-Array and their common group ID and that the A-loT Tag (element) spacing of the tags in the Tag Array is approximately the same (for example 0.5 to 0.7 of the activation signal wavelength). Reference is made to Figure 4, which shows a signalling exchange according to some examples. At 400, the controller (e.g. SCU) may initialize and configure an Activator and Reader for determining the relative placement order of a group of A-loT tags. For example, the controller may configure the Activator and Reader with a resource allocation for triggering activation of the tags in the group of tags and / or information indicating the phase sweep sequence to be performed. In some examples the controller may send, to the Activator and Reader, identifiers of the tags in the group of tags and a group identifier of the group of tags. At 402 the activator may send, to the tags in the group of tags, a capability report request. In response, at 404, each tag may emit a backscatter signal comprising tag capability information, such as information indicating the tag (for example a tag identifier) and information indicating a number of configurable phase shifts that the tag may perform, which may be received at the receiver. At 406, the receiver may forward the information received from the tags to the controller. At 408, based on the received tag capability information, the controller may determine and send a phase sweep configuration for the activator and a configuration for the reader for a first pair of tags in the group. The phase sweep configuration for the activator may indicate a phase sweep sequence to be performed by the tags (e.g. information indicating that one of the tags is to emit backscatter signals with a static phase and the other one of the tags is to emit backscatter signals with different phase shifts according to the configurable phase shifts that the tag can apply). In some examples the configuration may further comprise a resource allocation for the phase sweep sequence. The configuration for the reader may indicate the resource allocation for the reader to listen for the combined backscatter signal(s) from the group of tags. At 410, based on the configuration received from the controller at 408, the activator sends configuration information to the first pair of tags. The activator may configure a first tag to emit backscatter signals with a static phase and configure a second tag to emit backscatter signals with different phase shifts in a sequence - for example 0°, 45°, 90°... etc. At 412 the activator sends activation signals to the first pair of tags based on the configuration performed at 410. For example, the activator may send a first activation signal to activate the first tag (with static phase) and second tag (with phase shift = 0°) and send a second activation signal to activate the first tag (with static phase) and second tag (with phase shift = 45°). It should be understood that the number of activation signals sent may vary depending on the phase shift capabilities of the tags in the pair. At 414, the first pair of tags emit a combined backscatter signal based on the activation signal sent by the activator at 412. The combined backscatter signal is then received at the reader. The reader will receive a combined backscatter signal for each activation signal sent by the activator - for example when the activator sends two activation signals (to activate the first tag with static phase and the second tag with two different phase shifts), the reader will receive two different combined backscatter signals. At 416 the reader sends, to the controller, information indicating the combined power level of the backscatter signal received at 414 for each phase sweep of the tag pair. Following the earlier example where two activation signals are used to activate the first tag (with static phase) and the second tag (with phase shift = 0° and phase shift = 45°), the reader may indicate two combined power levels for the tag pair (one at tag B=0°, one at tag B=45°). At 418, based on the information received at 414, the controller determines the phase difference setting between the tags in the pair that provides the highest power level of the combined backscatter signal received by the receiver at 414. Steps 408-418 may then be repeated for each tag pair in the group of tags. For example, when the group of tags comprises tags {A, B,C,D}, steps 408-418 may be implemented once for each tag pair - e.g. once for tag pair AB, once for tag pair AC, and so on. Thus, after repeating steps 408-418, the controller has determined the phase difference setting between each pair of tags that provides the highest power level of the combined backscatter signal. At 420, the controller determines the placement order of the tags in the group based on the determined phase difference settings between each pair of tags that provides the highest power level of the combined backscatter signal. This will be discussed in further detail below. When the controller has determined the placement order of the tags in the group, the controller may store determined the placement order of the tags in the group. The controller may then determine the optimum tag group phase settings based on the determined placement order. For example, the controller may determine the tag group phase settings to maximise constructive interference of backscatter signals in the direction of the reader. In some examples the controller may determine that it is unable to determine the placement order at 420. For example, the controller may not have sufficient information (e.g. due to interference on the activation and / or backscatter signals), or there may be two or more phase differences with the same highest combined backscatter signal. In such examples the controller may assign a different reader within coverage of the group of tags or may configure the group of tags for temporary boresight operation - for example the controller may configure the group of tags for boresight operation until a tag array order can be determined and an optimum beam sweep pattern can be derived. By applying the method described above in relation to Figure 4, the number of combinations needed to determine the optimum tag group phase settings may be significantly reduced when compared to the method described in relation to Figure 3. For example, for an A-loT Tag-Array consisting of 4 individual A-loT Tags, each implemented with an eight-state phase shifter, there are 512 possible combinations, each of which would be assessed individually in the method of Figure 3. By applying the method described in Figure 4, an optimum tag group phase selection may be determined in as little as 5 to 7 beam sweep configurations for a 1x4 tag array. This is equal to a reduction of required sweep combinations / configurations of a factor of 70 up to 100. In some examples the angular direction of the Reader seen at the Tag-Array can be used to determine the placement order of the A-loT Tags in the Tag-Array, thereby allowing an optimum codebook can be derived for the Tag-Array. Table 1 below illustrates an example for a group of 4 A-loT Tags with 8 possible phase shifts per tag (0°, 45°, 90°, 135°, 180°, 225°, 270° &315°), which can be configured with an optimum codebook of seven entries (-45°, -30° -15°, 0°, 15°, 30°, 45°). In this example the A-loT Tags are assumed to be placed with an inter element distance of approximately half a wavelength (A / 2). Other numbers of A-loT Tags in the Tag-Array, number of possible phase shifts (even different per A-loT Tag) or number of configured beams in the codebook is also possible. In the example shown in Table 1 it is further assumed that the Reader is located at an angular direction suitable for deriving the order of the A-loT Tags in the Tag-Array, for example at 15°. The phase values shown in Table 1 are the phase difference settings (“delta phase”) on the A-loT Tag pairs in the A-loT Tag-Array that maximize the combined power of the backscatter signal received at the Reader at step 414. 1st Tag A A A B B C 2nd Tag B C D C D D Delta Phase 45° 90° 135° 45° 90° 45° Table 1: Example phase difference settings for maximized combined power received at the Reader. In some examples, the controller may determine the placement order of the tags in the group based on the following procedure: • The controller may determine the A-loT Tag pair(s) having a maximum combined power associated with the smallest set of similar delta phase values (e.g. the least common delta phase value(s)). For example, the smallest set of similar delta phase values in the example of Table 1 is the set comprising only one value, namely 135°. The controller may determine that the tag pair(s) in the smallest set of similar delta phase values will be the A-loT Tag pair(s) spaced with the largest possible physical distance in the Tag-Array. Thus in the example of Table 1 the controller may determine that A-loT Tag A &D are either the first and last A-loT Tags in the Tag-Array or the last and first A-loT Tags in the Tag-Array. Possible Tag-Array orders; [A, -, -, D] or [D, -, -, A], A B It should be understood that in the case of a two dimensional array (e.g. c p ), the smallest set of similar delta phase values may comprise two delta phase values - one associated with the separation between tags AD and one associated with the separation between tabs BC. • The controller may then determine one or more tag pairs having a highest combined power associated with the next smallest set of similar delta phase values (e.g. the next least common delta phase value(s)). For example, the next smallest set of similar delta phase values in the examiner of Table 1 is the set comprising two values, namely 90°, which corresponds to tag pairs AC and BD. The controller may determine that these tags are spaced with the next largest possible physical distance in the tag array. In the example of Table 1, the controller may determine that A-loT Tag pairs (A&C and B&D) have the maximum combined power at the next least common delta phase value (90°), and thus tags A&C and B&D will be spaced with the second largest possible physical distance in the Tag-Array. Thus the controller may determine that the possible Tag-Array order is one of: [A, B , C , D] or [D, C , B , A] • The controller may then determine one or more tag pairs having the a highest combined power associated with the next smallest set of similar delta phase values (e.g. the next least common delta phase value(s)). The controller may determine that these tags are spaced with the next largest possible physical distance in the tag array. This may be repeated until all tag pairs have been determined. In the case of the final tag pair(s) (e.g. the tag pairs associated having a highest combined power associated with the largest set of similar delta phase values, or in other words the most common delta phase values), the controller may determine that the spacing between those pairs is the smallest possible spacing, i.e. that those tags are adjacent. In the example of table 1, the controller may determine the next smallest set of similar delta phase values comprises the three values of 90° associated with tag pairs AB, BC and CD, and may determine that these tag pairs are adjacent. Thus the controller may determine the following possible Tag-Array orders: [A, B , C , D] or [D, C , B , A], In some examples “similar” phase values may be understood as being phase values that differ from each other by less than a certain amount. For example, for a certain value of 5, phase values of 87° and 92° may be considered similar, but phase values of 87° and 110° may not be considered similar. The certain amount may be selected or configured (e.g., by the network operator) according to the implementation. For example, a smaller certain amount may result in more frequent occurrences of values being considered not similar but may result in a higher degree of confidence that the results obtained from the values are accurate when similar values are found. In some examples the last evaluation may not be needed to derive the order of the A-loT Tags in the Tag-Array, as that is already determined in the former step. However, in some examples all the delta phase settings that maximizes the combined power may have to be determined for all the six A-loT Tag pairs to ensure that the correct maximum delta phase values are found. In addition, determining the delta phase for all six A-loT Tag pairs may in some examples be used to estimate the confidence level of the obtained results. In the example of Table 1, 48 iterations may be required for a full characterization of the possible 8 phase settings of the 6 A-loT Tag pairs. However, this procedure may be performed only a few times for each tag group (one time for many cases, but more for some cases if a unique solution is not found for the first iteration), whereafter the optimum codebook for the Tag-Array can be configured. In live operation, a maximum of 7 iterations (beam sweeps) may then be required. It should be understood that fewer A-loT Tags in the Tag-Array will reduce the number of needed iterations, while an increased number of A-loT Tags in Tag-Array will increase the number of needed iterations. It should be understood that, while examples have been provided with respect to a 1:4 tag array, in other examples other tag array sizes may be accounted for, including two dimensional tag arrays. Reference is made to Figure 5, which shows simulation results illustrating some of the concepts discussed above. The simulated results shown in Figure 5 are obtained based on a 1x4 linear A-loT Tag-Array configuration as an example, where the combined antenna gain values for the pair of activated A-loT Tags (i.e. the combined power of the backscatter signals for a given tag pair) during the phase sweeping procedure are shown for different angular directions (0°, 3°, 6°, 9°, 12°, 15°, 30° &45°) of the Reader compared to the orientation of the A-loT Tag-Array. The values in bold indicates the delta phase setting for maximum combined antenna gain for the activated A-loT Tag pair, which may for example be the phase difference setting determined by the controller at step 418. As can be seen from Figure 5, the angle of the reader device may impact on the phase shift associated with the maximum combined power level for a given tag pair. In some examples the measurements for the different angular directions towards the Reader can be used to derive the placement order of the A-loT Tags in the A-loT Tag-Array. For example a 2nd order curve approximation may be made for each column (A-loT Tag pair) and the maximum combined antenna gain value for each approximated curve determined. In some examples, when performing a second order approximation, the values in each column may be sorted such that the two lowest combined antenna gain values are located at the start and end of the evaluation vector. For example, in Figure 5a, for tag pair BD the lowest values (-0.3 and -18.0) are located at the start (-135 degrees) and end (180 degrees) of the evaluation vector. However in some examples this may not be the case - for example tag pair AD in Figure 5d, the lowest value (-14.6) is located in the middle of the evaluation vector (at -90 degrees. Thus the vector for the tag pair AD may be sorted such that the sequence of antenna gain (reading from -135 degrees to 180 degrees) reads as follows:. -14.6, 0.8, 5.9, 8.3, 9.1, 8.6, 6.2, 0.8. In some cases the receiver dynamic range at the Reader may be limited. As such, some of the A-loT Tag pair phase sweeps may result in low combined antenna gain values that cannot be detected and may be omitted from the curve approximation process. Figure 6 shows example 2nd order curve approximations for the values shown in Figure 5h. As can be seen, there is a single distinct delta phase value at 600 with a maximum around 30° (corresponding to tag pair AD), two similar delta phase values at 602 with maxima around 260° (corresponding to tag pairs AC and BD), and three similar delta phase values at 604 with maxima around 130° (corresponding to tag pairs AB, BC, and CD). Figure 7 shows the resulting estimated delta phase value (in degrees) for maximum combined antenna gain for the different activated A-loT Tag pairs with the Reader located at different angular directions compared to the orientation of the Tag-Array. In the examples shown in Figure 7, the second order approximation has been performed by using the measured delta phase values in three different ways: Approximation 1 (App#1): All of the simulated delta phase values have been used. Approximation 2 (App#2): Delta phase values lower than 10 dB from the maximum delta phase values have been removed (this may illustrate a Reader with limited dynamic range). Approximation 3 (App#3): Delta phase values lower than -5 dB have been truncated to -5 dB. In some examples the controller may know how many tags are in the tag array, and thus may know how many tag pairs to expect with a certain separation. For example in a tag array of four tags, the controller may expect: For a linear array (e.g. {A,B,C,D} - one tag pair with the largest separation (e.g. AD), two tag pairs with a next largest separation (e.g. BD and AC), and three tag pairs with a smallest separation (e.g. AB, BC, CD); or A B For a two-dimensional array (e.g. )- two tag pairs with the largest separation (e.g. AD and BC) and four tag pairs with a smallest separation (e.g. AB, AC, CD, BD). While the controller may not know whether the tags are arranged in a linear or two dimensional array, the controller may determine one (in the case of a linear tag array) or two (in the case of a two-dimensional array) of the tag pairs associated with a distinct delta phase value compared to the other tag pairs as being the tag pair(s) with the largest separation. That is to say, in some examples the controller may determine the tag pair(s) with a maximum combined power associated with the smallest set of similar delta phase values (e.g. the least common delta phase value(s)) as being the tag pair(s) with the largest separation. For example with reference to Figure 7c, in approximation 1 the delta phase value for tag pair AD is distinct from the delta phase values of all the other tag pairs (e.g. 65° for tag pair AD in compared to values of 15°, 39°, 15°, 49° and 28° for the other tag pairs), and is thus the tag pair with the maximum combined power associated with the smallest set of similar delta value values (in this case, the set comprises one value). In this context, distinct may refer to a value that is different from the nearest other values by more than a certain amount (and as described previously, similar may mean that the values are within a certain amount of each other). From this, the controller may determine that tags AD have the largest separation. In some examples, for instance as shown in Figure 7a, in some cases there may not be a single distinct delta phase value, or the selection of a distinct phase value may be highly uncertain (in that the value is not significantly different from the other values). As such the selection of the tag pair based on this value may produce an incorrect determination as to the tag pair with the largest separation. In such cases, a different reader may be selected and the procedure repeated at a different angular direction of the reader with respect to the group of tags. Having determined the tag pair with the furthest separation, the controller may then determine the one or more remaining tag pairs having a highest combined power associated with the next smallest set of similar delta phase values as being the tag pairs with the next largest separation. For example, with reference to Figure 7c, the controller may determine that the delta phase values for tag pairs AC and BD are the next smallest set of similar delta phase values (e.g. under approximation 1, tags AC and BD have a delta phase of 39° and 49° which may be considered similar, and is a smaller set compared to the set of similar delta phase values of 15°, 15° and 28° for the other remaining tag pairs). The controller may then determine the remaining tag pairs as being the tag pairs with the smallest separation, i.e. the pairs of tags that are adjacent. In Figure 7, tag pairs that are considered adjacent are indicated by bold text in the delta phase values; tag pairs that are separated by one tag are indicated by italic text in the delta phase values, and the tag pair that is separated with the largest separation is indicated by normal text in the delta phase values. As can be seen from Figure 7, the order of the A-loT Tags in the A-loT Tag-Array can be identified for use cases where the Reader is at an angular direction compared to the Tag-Array of more than 3° for this example. However, the confidence level of the estimation increases as the angular direction increases, as the delta phase shifts of the A-loT pair groups also increases. In addition, Figure 7 shows that approximations 2 and 3 (where some of the low antenna gain values have been removed or truncated) may improve the confidence level in line with the expected dynamic range of realistic in-field measurements. While the maximum and minimum delta phase groups change for angular directions higher than 30° (as the delta phase shifts wrap around 360°) each pair group may still be identifiable as shown in Figure 7h for an angular direction of 45°. The principles described above may be adapted from a linear array to a two-dimensional array - however it should be understood that in the case of a two-dimensional array, the delta phase values determined by the controller may be different to those described above. For example, the controller may not determine a single distinct delta phase value, but rather determine two or more delta phase values that are similar to each other and distinct from the other delta phase values (corresponding to the tags that are separated from each other by the longest distance on the diagonal of the array). When determining the remaining tag pairs having the next most similar delta phase values as being the tag pairs with the next largest separation, in the case of a 2x2 array the controller may determine that all the remaining tags have the same / similar delta phase values and thus conclude that those tags have the same / similar separation. Thus in some examples the controller may determine the placement order of tags in a group of tags (or tag array) based on backscatter signals produced by pairs of tags in the group during a phase sweep sequence. In particular, the controller may determine, for all tag pairs in the group, the phase difference between the tags in a pair that is associated with the highest backscatter signal power. Based on the determined phase differences, the controller may deduce the tags that are further separated from each other, and then determine the next furthest separated tags (and so on) until the placement order of all the tags has been determined. The controller may use the determined placement order to determine a codebook for the activator to activate the tags in the group to achieve maximum gain in the direction of the reader. In some examples there is provided a controller comprising means for: configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence; configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence; receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; and based on the information indicating the power level, determining an order of the tags in the group of tags. In some examples there is provided a controller comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the controller at least to: configure an activator device for activating each pair of tags in a group of tags in a phase sweep sequence; configure a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence; receive, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; and based on the information indicating the power level, determine an order of the tags in the group of tags. In some examples there is provided an activator device comprising means for: receiving, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; and activating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. In some examples there is provided an activator device comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the activator device at least to: receive, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; and activate the tag pairs in the group of tags in the phase sweep sequence based on the received configuration. In some examples there is provided a reader device comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the reader device at least to: receive, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence; receive, from each of pairs of tags according to the received configuration, a combined signal; and send, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. In some examples there is provided a reader device comprising means for: receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence; receiving, from each of pairs of tags according to the received configuration, a combined signal; and sending, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence. It is understood that references in the above to various network functions (e.g., to an AMF, an SMF, etc.) may comprise apparatus that perform at least some of the functionality associated with those network functions. Further, an apparatus comprising a network function may comprise a virtual network function instance of that network function. It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and / or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities. It is noted that whilst some embodiments have been described in relation to 5G networks, similar principles can be applied in relation to other networks and communication systems. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements. In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.” This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device. The embodiments of this disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computerexecutable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it. Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM). The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples. Embodiments of the disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. The scope of protection sought for various embodiments of the disclosure is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the disclosure. The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this disclosure will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1 A controller comprising means for:configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence;configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence;receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; andbased on the information indicating the power level, determining an order of the tags in the group of tags.

2. The controller of claim 1, wherein configuring the activator device comprises configuring the activator device to activate a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases, wherein the different phases are selected based on information indicating a phase shift capability of the second tag.

3. The controller of claim 2, further comprising means for:receiving, from the reader device, the information indicating the phase shift capability of each of the tags in the group of tags.

4. The controller of claim 2 or 3, wherein the information indicating the power level of the combined signal received by the reader device for each of the pairs of tags comprises, for each tag pair, the power level of the combined signal received by the reader device for each of the different phases in the phase sweep sequence.

5. The controller of any preceding claim, wherein configuring the activator device and the reader device comprises sending, to the activator device and the reader device, information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags.

6. The controller of any preceding claim, wherein:configuring the activator device comprises sending a resource allocation to the activator device for activating each pair of tags; andconfiguring the reader device comprises sending a resource allocation to the reader device for receiving the signals from each pair of tags.

7. The controller of any preceding claim, wherein determining the order of the tags in the group of tags comprises:determining, for each tag pair, a phase difference setting between the tags corresponding to the highest power level of the combined signal; anddetermining the order of the tags based on the determined phase difference settings.

8. The controller of claim 7, wherein determining the order of the tags based on the determined phase difference settings comprises:determining a first tag pair having the highest power level of the combined signal associated with the smallest set of similar phase difference settings between the tags as being the tag pair with the greatest separation.

9. The controller of claim 8, wherein determining the order of the tags based on the determined phase difference settings further comprises:determining one or more further pairs of tags having the highest power level of the combined signal associated with the next smallest set of phase difference settings between the tags as being the tag pair with the next largest separation; andrepeating the determining for the remaining tag pairs for each next largest phase difference until all tag pairs have been determined.

10. The controller of any of claims 7 to 9, wherein determining the order of tags based onthe determined phase difference settings comprises:determining, for each tag pair, a second order approximation based on the information indicating the power level of the combined signal received by the receiver for each phase setting in the phase sweep sequence;determining phase difference values for each tag pair based on the second order approximation; anddetermining the placement order based on the determined second order approximations.

11. The controller of claim 10, wherein determining the placement order based on the determined second order approximations comprises:determining a first tag pair having the highest power level of the combined signal associated with a smallest set of similar phase difference values as being the tag pair with the largest separation; anddetermining a second and third tag pair having the highest power level of the combined signal associated with the next smallest set of similar phase difference values as being tag pairs with the next largest separation.

12. The controller of any preceding claim, wherein the means is further for:storing the determined order of the tags with information associated with the group of tags.

13. The controller of any preceding claim, further comprising means for:determining a tag group phase setting selection based on the determined order of the tags; andsending, to the activator device and the reader device, information indicating the determined tag group phase setting selection.

14. An activator device comprising means for:receiving, from a controller, a configuration for activating each pair of tags in a group of tags in a phase sweep sequence; andactivating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration.

15. The activator device of claim 14, wherein activating the tag pairs comprises activating a first tag in a tag pair for the phase sweep sequence with a static phase and a second tag in the tag pair for the phase sweep sequence with different phases.

16. The activator device of claim 14 or 15, wherein receiving the configuration further comprises receiving information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags.

17. The activator device of any of claims 14 to 16, wherein receiving the configuration further comprises receiving a resource allocation to the activator device for activating each pair of tags.

18. The activator device of any of claims 14 to 17, further comprising means for:receiving, from the controller, information indicating a tag group phase setting selection.

19. A reader device comprising means for:receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence;receiving, from each of pairs of tags according to the received configuration, a combined signal; andsending, to the controller, information indicating a power level of the combined signal for each of the pairs of tags in the phase sweep sequence.

20. The reader device of claim 19, further comprising means for:receiving, from each of the tags in the group of tags, information indicating a phase shift capability of the tag; andsending, to the controller, the information indicating the phase shift capability of each of the tags in the group of tags.

21. The reader device of claim 19 or 20, wherein the information indicating the power level of the combined signal for each of the pairs of tags comprises, for each tag pair, information indicating the power level of the combined signal for a plurality of different phases in a phase sweep sequence.

22. The reader device of any of claims 19 to 21, wherein the configuration further comprises information indicating an identifier of the tags in the group of tags and / or a group identifier of the group of tags.

23. The reader device of any of claims 19 to 22, wherein receiving the configuration further comprises receiving a resource allocation for receiving the signals from each pair of tags.

24. A method performed by a controller, the method comprising:configuring an activator device for activating each pair of tags in a group of tags in a phase sweep sequence;configuring a reader device for receiving signals from each pair of tags in the group of tags in the phase sweep sequence;receiving, from the reader device, information indicating a power level of a combined signal received by the reader device for each of the pairs of tags in the phase sweep sequence; andbased on the information indicating the power level, determining an order of the tags in the group of tags.

25. A method performed by an activator device, the method comprising:5 receiving, from a controller, a configuration for activating each pair of tags in a groupof tags in a phase sweep sequence; andactivating the tag pairs in the group of tags in the phase sweep sequence based on the received configuration.10 26. A method performed by a reader device, the method comprising:receiving, from a controller, a configuration for receiving signals from pairs of tags in a group of tags in a phase sweep sequence;receiving, from each of pairs of tags according to the received configuration, a combined signal; and15 sending, to the controller, information indicating a power level of the combined signalfor each of the pairs of tags in the phase sweep sequence.

Images