Selecting a non-terrestrial network based public land mobile network

A wireless device, UE, in a communication network receives satellite positioning information and a list of a plurality of different types of measurements to perform to find a public land mobile network, PLMN, to select. The UE performs the plurality of different types of measurements on a frequency associated with a found PLMN to generate a plurality of measurement results. The UE determines, based on the plurality of measurements results, whether a high-quality indication should be provided to a non-access stratum, NAS. Responsive to determining that the high-quality indication should be provided, the UE provides the high quality indication and an identification of the found PLMN to the NAS.

TECHNICAL FIELD

The present disclosure relates generally to communications, and more particularly to communication methods and related devices and nodes supporting wireless communications.

BACKGROUND

There is an ongoing resurgence of satellite communications. Several plans for satellite networks have been announced in the past few years. The target services for these satellite networks vary, from backhaul and fixed wireless, to transportation, to outdoor mobile, to IoT. Satellite networks could complement mobile networks on the ground by providing connectivity to underserved areas and multicast/broadcast services.

To benefit from the strong mobile ecosystem and economy of scale, adapting the terrestrial wireless access technologies including LTE and new radio access technology (NR) for satellite networks is drawing significant interest. For example, the third-generation partnership project (3GPP) completed an initial study in Release 15 on adapting NR to support non-terrestrial networks (mainly satellite networks). This initial study focused on the channel model for the non-terrestrial networks, defining deployment scenarios, and identifying the key potential impacts. 3GPP is conducting a follow-up study item in Release 16 on solutions evaluation for NR to support non-terrestrial networks.

A satellite radio access network can include: a gateway that connects satellite network to core network; a satellite (e.g., a space-borne platform); a terminal (e.g., a wireless device and/or user equipment (UE); a feeder link (e.g., a link between a gateway and a satellite); and a service link (e.g., a link between a satellite and a terminal).

The link from gateway to terminal is often called forward link, and the link from terminal to gateway is often called return link. Depending on the functionality of the satellite in the system, two transponder options may be considered: a bent pipe transponder and/or a regenerative transponder. When using a Bent pipe transponder, a satellite forwards the received signal back to the earth with only amplification and a shift from uplink frequency to downlink frequency. When using a regenerative transponder, a satellite includes on-board processing to demodulate and decode the received signal and regenerate the signal before sending it back to the earth.

Depending on the orbit altitude, a satellite may be categorized as a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, or a geosynchronous earth orbit (GEO) satellite. A LEO satellite is located at a height ranging from 500-1,500 km, with orbital periods ranging from 10-40 minutes. A MEO satellite is located at a height ranging from 5,000-12,000 km, with orbital periods ranging from 2-8 hours. A GEO satellite is located at a height of 35,786 km, with an orbital period of 24 hours.

A satellite may generate several beams over a given area. The footprint of a beam is usually in an elliptic shape, which has been called a cell. The footprint of a beam is also often referred to as a spotbeam. The footprint of a spotbeam may move over the earth surface with the satellite movement or may be earth fixed with some beam pointing mechanism used by the satellite to compensate for its motion. The size of a spotbeam depends on the system design, which may range from tens of kilometers to a few thousands of kilometers.

FIG.1shows an example architecture of a satellite network with bent pipe transponders.

Two of the main physical phenomena that affect satellite communications system design are the long propagation delay and Doppler effects. The Doppler effects are especially pronounced for LEO satellites.

Propagation delay can be a main physical phenomenon in a satellite communication system that makes the design different from that of a terrestrial mobile system. For a bent pipe satellite network such as the satellite network illustrated inFIG.1, the one-way delays, round-trip delays, and differential delays are relevant. A one-way delay can be a delay from the base station (BS) to the UE via the satellite, or the other way around. A round-trip delay can be a delay from the BS to the UE via the satellite and from the UE back to the BS via the satellite. A differential delay can be the delay difference of two selected points in the same spotbeam.

There may be additional delay between the ground BS antenna and BS, which may or may not be collocated. This delay depends on deployment. If the delay cannot be ignored, it should be taken into account in the communications system design.

The propagation delay depends on the length of the signal path, which further depends on the elevation angles of the satellite seen by the BS and UE on the ground. The minimum elevation angle is typically more than 10° for UE and more than 5° for BS on the ground.

The round-trip time (RTT) delay is much larger in satellite systems as illustrated in the tables ofFIGS.15-16. For example, the RTT is about 545 ms for a GEO satellite system such as the satellite network illustrated inFIG.1. In contrast, the round-trip time may be no more than 1 ms for terrestrial cellular network.FIG.15is a table illustrating an example of propagation delays for GEO satellites.FIG.16is a table illustrating an example of propagation delays for non-GSO (NGSO) satellites. Within a spot beam covering one cell, the delay may be divided into a common delay component and a differential delay component. The common delay is the same for all UEs in the cell and may be determined with respect to a reference point in the spot beam. In contrast, the differential delay may be different for different UEs as the differential delay depends on the propagation delay between the reference point and the point at which a given UE is positioned within the spot beam.

The differential delay is mainly due to the different path lengths of the access links, since the feeder link is normally the same for terminals in the same spotbeam. Further, the differential delay is mainly determined by the size of the spotbeam. It may range from sub-millisecond (for spotbeam on the order of tens of kilometres) to tens of millisecond (for spotbeam on the order of thousands of kilometres).

In RAN #80, a new study item (SI) “Solutions for NR to support Non-Terrestrial Network” was agreed upon. The SI is a continuation of a preceding SI “NR to support Non-Terrestrial Networks” (RP-171450), where the objective was to study the channel model for the non-terrestrial networks, to define deployment scenarios, parameters and identify the key potential impacts on NR.

Public land mobile network (PLMN) selection in NR is defined by TS 38.304 and TS 23.122. TS 38.304 defines the below access stratum (AS) functionality:“The UE shall scan all RF channels in the NR bands according to its capabilities to find available PLMNs. On each carrier, the UE shall search for the strongest cell and read its system information, in order to find out which PLMN(s) the cell belongs to. If the UE can read one or several PLMN identities in the strongest cell, each found PLMN (see the PLMN reading in TS 38.331 [3]) shall be reported to the NAS as a high quality PLMN (but without the RSRP value), provided that the following high-quality criterion is fulfilled:1. For an NR cell, the measured RSRP value shall be greater than or equal to −110 dBm.Found PLMNs that do not satisfy the high-quality criterion but for which the UE has been able to read the PLMN identities are reported to the NAS together with their corresponding RSRP values. The quality measure reported by the UE to NAS shall be the same for each PLMN found in one cell.The search for PLMNs may be stopped on request from the NAS. The UE may optimise PLMN search by using stored information e.g. frequencies and optionally also information on cell parameters from previously received measurement control information elements.Once the UE has selected a PLMN, the cell selection procedure shall be performed in order to select a suitable cell of that PLMN to camp on.”

TS 23.122 define how the non-access stratum (NAS) selects PLMN based on the information obtained from the AS. This selection may be based on the type of PLMN, e.g., Home PLMNs (HPLMNs), based on the access technology supported by the PLMN, e.g. LTE, based on the signal quality and strength measured on a PLMN. and based on the UEs and PLMNs capabilities.

The below text is a sample from TS 23.122 illustrating one of the current PLMN selection procedures:″4.4.3.1.1 Automatic Network Selection Mode ProcedureThe MS selects and attempts registration on other PLMN/access technology combinations, if available and allowable, in the following order:i) either the (if the EHPLMN list is not present or is empty) or the highest priority EHPLMN that is available (if the EHPLMN list is present);ii) each PLMN/access technology combination in the “User Controlled PLMN Selector with Access Technology” data file in the SIM (in priority order);iii) each PLMN/access technology combination in the “Operator Controlled PLMN Selector with Access Technology” data file in the SIM (in priority order);iv) other PLMN/access technology combinations with received high quality signal in random order;v) other PLMN/access technology combinations in order of decreasing signal quality.When following the above procedure the following requirements apply:a) An MS with voice capability shall ignore PLMNs for which the MS has identified at least one GSM COMPACT.b) . . . ”

SUMMARY

According to some embodiments of inventive concepts according to the present disclosure, methods are provided to provide mechanisms for a wireless device to select NTN PLMNs and terrestrial PLMNs. The wireless device receives satellite positioning information. The wireless device further receives a list of a plurality of different types of measurements to perform to find a public land mobile network (PLMN) to select. The wireless device may perform the plurality of different types of measurements on a frequency associated with a found PLMN to generate a plurality of measurement results. The wireless device may determine based on the plurality of measurement results whether a high-quality indication should be provided to a non-access stratum (NAS). Responsive to determining that the high-quality indication should be provided, the wireless device provides the high quality indication and an identification of the found PLMN to the NAS.

A potential advantage of this method is that a wireless device may select a suitable PLMN based on relevant NTN aspects. By performing the additional measurements (i.e., the plurality of different types of measurements), a wireless device that operates according to this method may avoid selecting a PLMN that has aspects that may impair the link quality of service (QoS) that the wireless device may have otherwise selected without performing the additional measurements.

According to some other embodiments, a method is provided to operate a wireless device. The wireless device receives satellite positioning information and a list of a plurality of different types of measurements to perform to find a public land mobile network (PLMN) to select, the plurality of different types of measurements including a reference signal received power (RSRP) measurement. The wireless device may perform the plurality of measurements on a frequency associated with a found PLMN to generate a plurality of measurement results including a RSRP. The wireless device may determine whether the RSRP is greater than a RSRP threshold. Responsive to determining the RSRP is greater than the threshold, the wireless device may determine based on the plurality of measurement results whether every additional measurement result in the plurality of measurement results is above or below the corresponding threshold as specified. Responsive to every of the additional specified measurement results being above or below the thresholds as specified, the wireless device forwards the identification of the found PLMN and a high-quality indication to the NAS. Responsive to any of the additional specified measurement results not being above or below the thresholds as specified, the wireless device may forward the identification of the found PLMN with a high quality RSRP indication and the additional measurement results to the NAS.

According to some other embodiments, a method is provided to operate a wireless device. The wireless device may receive for each of a plurality of public land mobile networks (PLMNs), an identification of the PLMN and one of a plurality of measurement results for the PLMN or a high-quality indication for the PLMN, the PLMN being one of a terrestrial PLMN or a non-terrestrial network (NTN) PLMN. The wireless device may prioritize the plurality of PLMNs based on the high-quality indication and the plurality of measurement results. The wireless device may select a PLMN to camp on from the plurality of PLMNs based on the prioritization. The wireless device may perform an action to camp on the selected PLMN.

DETAILED DESCRIPTION

FIG.2is a block diagram illustrating elements of a wireless device200(also referred to as a mobile terminal, a mobile communication terminal, a wireless communication device, a wireless terminal, a wireless communication terminal, user equipment, UE, a user equipment node/terminal/device, etc.) configured to provide wireless communication according to embodiments of inventive concepts. (Wireless device200may be provided, for example, as discussed below with respect to wireless device4110ofFIG.17.) As shown, wireless device UE may include an antenna207(e.g., corresponding to antenna4111ofFIG.17), and transceiver circuitry201(also referred to as a transceiver, e.g., corresponding to interface4114ofFIG.17) including a transmitter and a receiver configured to provide uplink and downlink radio communications with a base station(s) (e.g., corresponding to network node4160ofFIG.17) of a radio access network. Wireless device UE may also include processing circuitry203(also referred to as a processor, e.g., corresponding to processing circuitry4120ofFIG.17) coupled to the transceiver circuitry, and memory circuitry205(also referred to as memory, e.g., corresponding to device readable medium4130ofFIG.17) coupled to the processing circuitry. The memory circuitry205may include computer readable program code that when executed by the processing circuitry203causes the processing circuitry to perform operations according to embodiments disclosed herein. According to other embodiments, processing circuitry203may be defined to include memory so that separate memory circuitry is not required. Wireless device UE may also include an interface (such as a user interface) coupled with processing circuitry203, and/or wireless device UE may be incorporated in a vehicle.

As discussed herein, operations of wireless device UE may be performed by processing circuitry203and/or transceiver circuitry201. For example, processing circuitry203may control transceiver circuitry201to transmit communications through transceiver circuitry201over a radio interface to a radio access network node (also referred to as a base station) and/or to receive communications through transceiver circuitry201from a RAN node over a radio interface. Moreover, modules may be stored in memory circuitry205, and these modules may provide instructions so that when instructions of a module are executed by processing circuitry203, processing circuitry203performs respective operations (e.g., operations discussed below with respect to Example Embodiments relating to wireless devices).

FIG.3is a block diagram illustrating elements of a radio access network RAN node300(also referred to as a network node, base station, eNodeB/eNB, gNodeB/gNB, etc.) of a Radio Access Network (RAN) configured to provide cellular communication according to embodiments of inventive concepts. (RAN node300may be provided, for example, as discussed below with respect to network node4160ofFIG.17.) As shown, the RAN node may include transceiver circuitry301(also referred to as a transceiver, e.g., corresponding to portions of interface4190ofFIG.17) including a transmitter and a receiver configured to provide uplink and downlink radio communications with mobile terminals. The RAN node may include network interface circuitry307(also referred to as a network interface, e.g., corresponding to portions of interface4190ofFIG.17) configured to provide communications with other nodes (e.g., with other base stations) of the RAN and/or core network CN. The network node may also include a processing circuitry303(also referred to as a processor, e.g., corresponding to processing circuitry4170) coupled to the transceiver circuitry, and a memory circuitry305(also referred to as memory, e.g., corresponding to device readable medium4180ofFIG.17) coupled to the processing circuitry. The memory circuitry305may include computer readable program code that when executed by the processing circuitry303causes the processing circuitry to perform operations according to embodiments disclosed herein. According to other embodiments, processing circuitry303may be defined to include memory so that a separate memory circuitry is not required.

As discussed herein, operations of the RAN node may be performed by processing circuitry303, network interface307, and/or transceiver301. For example, processing circuitry303may control transceiver301to transmit downlink communications through transceiver301over a radio interface to one or more mobile terminals UEs and/or to receive uplink communications through transceiver301from one or more mobile terminals UEs over a radio interface. Similarly, processing circuitry303may control network interface307to transmit communications through network interface307to one or more other network nodes and/or to receive communications through network interface from one or more other network nodes. Moreover, modules may be stored in memory305, and these modules may provide instructions so that when instructions of a module are executed by processing circuitry303, processing circuitry303performs respective operations such as providing to the wireless device200(also referred to as UE in the description below) the thresholds to use for measurements as described below.

According to some other embodiments, a network node may be implemented as a core network CN node without a transceiver. In such embodiments, transmission to a wireless device UE may be initiated by the network node so that transmission to the wireless device is provided through a network node including a transceiver (e.g., through a base station or RAN node). According to embodiments where the network node is a RAN node including a transceiver, initiating transmission may include transmitting through the transceiver.

FIG.4is a block diagram illustrating elements of a core network CN node (e.g., an SMF node, an AMF node, etc.) of a communication network configured to provide cellular communication according to embodiments of inventive concepts. As shown, the CN node may include network interface circuitry407(also referred to as a network interface) configured to provide communications with other nodes of the core network and/or the radio access network RAN. The CN node may also include a processing circuitry403(also referred to as a processor) coupled to the network interface circuitry, and memory circuitry405(also referred to as memory) coupled to the processing circuitry. The memory circuitry405may include computer readable program code that when executed by the processing circuitry403causes the processing circuitry to perform operations according to embodiments disclosed herein. According to other embodiments, processing circuitry403may be defined to include memory so that a separate memory circuitry is not required.

As discussed herein, operations of the CN node may be performed by processing circuitry403and/or network interface circuitry407. For example, processing circuitry403may control network interface circuitry407to transmit communications through network interface circuitry407to one or more other network nodes and/or to receive communications through network interface circuitry from one or more other network nodes. Moreover, modules may be stored in memory405, and these modules may provide instructions so that when instructions of a module are executed by processing circuitry403, processing circuitry403performs respective operations such as communicating with the UE over the NAS layer.

PLMN Selection

In current specifications, the access stratum (AS) layer in the UE may scan all radio frequency (RF) bands to find available public land mobile networks (PLMNs). The scanning may include finding the strongest cell on each carrier and reading the system information. The AS layer in the UE shall report the found PLMNs and their associated measured RSRP (reference signal received power) value to the NAS layer, which selects a PLMN to camp on according to 3GPP TS 23.122.

If the UE finds that the measured RSRP value is larger than a specific value, then the UE shall report these PLMNs as “high quality signal” to the NAS layer that makes the selection among the available PLMNs.

One problem identified is that the current PLMN selection criterion for determining the PLMNs may not be suitable for non-terrestrial network (NTN) cells due the different propagation in an NTN compared to a terrestrial network. One example of why this may not be suitable is that a satellite may not be suitable to select if the satellite is too close to the horizon, i.e. if the angle of elevation between the UE and the satellite (seeFIG.5) is too low. A small elevation in associated with large doppler frequency offsets and large round-trip times (RTTs) which both are aspects that impairs the link quality of service (QoS).

A second problem that may occur is that the current NAS PLMN selection according to 3GPP TS 23.122 does not take any NTN specifics into consideration. Due to the significant delays, path loss and Doppler frequency offsets associated with an NTN, the NTN may not be able to offer the same QoS as a terrestrial NW. These delays, path loss, and offsets are currently not accounted for in the PLMN selection.

This second problem may cause the UE to connect to a PLMN where the propagation delay is much larger than what the radio technology operating the PLMN supports, making establishing connection to a cell in the PLMN difficult or even impossible, which further on might cause large amount of interference.

A set of basic mechanisms for preparing PLMN selection for NTN is described below. The mechanisms may ensure that a UE selects a suitable PLMN based on relevant NTN aspects.

In one embodiment the existing PLMN selection, i.e. to determine the “high quality signal” is enhanced, in addition to RSRP, based on one or more of the following measurements performed by a UE: RSRQ (reference signal received quality), or another signal quality metric such as SINR (signal-to-interference-plus-noise ratio); RTT (round trip time); differential delay, i.e. the delay between the measured RTT and a broadcasted cell or PLMN specific RTT; UE geographical position; satellite elevation angle; satellite orbital height; and/or satellite ephemeris data

In some embodiments a UE may be capable of only performing one of the above measurements. In additional or alternative embodiments, A UE may be capable of performing a few of the above listed measurements. In additional or alternative embodiments, a UE may be capable of performing all of the above measurements.

The above measured metrics may be compared to corresponding thresholds that may be signalled by the network via a network node or be fixed in the 3GPP specifications. The signalling may be done by radio resource control (RRC) or NAS. The UE may signal the measured values to the NAS together with a high signal quality indicator when applicable, as exemplified in the embodiments illustrated inFIGS.6-8.

Operations of the wireless device200(implemented using the structure of the block diagram ofFIG.2) will now be discussed with reference to the flow chart ofFIG.6according to some embodiments of inventive concepts. For example, modules may be stored in memory205ofFIG.2, and these modules may provide instructions so that when the instructions of a module are executed by respective wireless device processing circuitry203, processing circuitry203performs respective operations of the flow chart.

Turning toFIG.6, the additional measured value specified shall be RTT to describe this embodiment. Other measurements may be used, such as one of the measurements described above. In operation600, the processing circuitry203may measure the RSRP and RTT on the frequency associated to a PLMN. In operation602, the processing circuitry203may determine whether the RSRP is greater than an RSRP threshold and whether the RTT is less than an RTT threshold. Responsive to the RSRP being greater than the RSRP threshold and the RTT being less than the RTT threshold, the processing circuitry203may forward the identification of the PLMN and a high-quality indication to the NAS in operation604. Responsive to either the RSRP being less than the RSRP threshold or the RTT being greater than the RTT threshold, the processing circuitry203may forward the identification of the PLMN and the measured RSRP and RTT values to the NAS in operation606.

FIG.7illustrates an embodiment where multiple additional measurements may be taken. In operation700, the processing circuitry203may receive satellite positioning information and/or a list of a plurality of measurements to perform to find a PLMN to select. The plurality of measurements may include a plurality of different types of measurements. In some embodiments, one of the plurality of different types of measurements includes an RSRP measurement. In additional or alternative embodiments, the list of the plurality of different types of measurements may include at least one of a reference signal received quality, RSRQ, measurement a signal-to-interference-plus-noise ratio, SINR, measurement a round trip time, RTT, measurement and a differential delay measurement. In some examples, a differential delay is a difference in propagation delay of UEs in the cell. In additional or alternative examples, a differential delay is the difference in distance between the UE and a satellite. The satellite positioning information may include at least one of a UE geographical position, a satellite elevation angle, a satellite orbital height, and satellite ephemeris data. The list may also provide the threshold to use in which to compare the measurement results for each of the plurality of different types of measurements. For example, the threshold for a measurement result may indicate whether the measurement result should be above or below the specified threshold value. The one or more measurements may depend on the capability of the UE as described above. When a specified measurement is satellite specific, a default comparison result may be specified for terrestrial based PLMNs. For example, if satellite elevation angle is specified and the threshold specified is being greater than or equal to a specified angle, the default comparison result for terrestrial based PLMNs is an indication of a “yes.” Alternatively, the comparison result may indicate that it is not applicable.

In operation702, the processing circuitry203may perform the plurality of measurements on a frequency associated with a found PLMN to generate a plurality of measurement results. For example, a RSRP may be measured and the additional specified measurement results in the plurality of measurement results may be generated (i.e., measured) from the frequency associated to the found PLMN. In operation704, the processing circuitry203may determine based on the plurality of measurement results whether a high-quality indication should be provided to the NAS. For example, if the RSRP is greater than an RSRP threshold and if the additional measurement results are above or below the thresholds as specified, the indication should be provided. An example of the additional plurality of measurement results may be RTT and RSRQ, and the thresholds may be RTT<RTTTHand RSRQ≥RSRQTH.

Turning toFIG.8, in one embodiment, determining (704) based on the plurality of measurement results whether the high-quality indication should be provided to the NAS includes receiving, in operation800, a plurality of thresholds, each of the plurality of thresholds corresponding to one of the plurality of measurement results and indicating whether the measurement result should be above or below a threshold value. For each of the plurality of measurement results, the measurement result is compared to a corresponding threshold of the plurality of thresholds in operation802and a determination is made as to whether the measurement result is above or below the corresponding threshold in accordance with the indication of the corresponding threshold in operation804. In operation806, responsive to the measurement result being above or below the threshold in accordance with the indication for all of the plurality of measurement results, a determination is made that the high-quality indication should be provided.

Returning toFIG.7, in operation706, responsive to determining that the high-quality indication should be provided, the high quality indication and an identification of the found PLMN is provided to the NAS. For example, responsive to the RSRP being greater than the RSRP threshold and the additional specified measurement results are above or below the thresholds as specified, the processing circuitry203may forward the identification of the PLMN and the high-quality indication to the NAS.

Responsive to either the RSRP being less than the RSRP threshold or any of the additional specified measurement results are not above or below the thresholds as specified, the processing circuitry203may forward the identification of the PLMN and the measured RSRP and additional measurement value(s) to the NAS in operation708.

In one embodiment the existing RSRP based “high quality signal” decision is complemented by a second NTN specific “high quality signal” decision that is based on the measured values for one or more of the above metrics.

A combined determination of a “high quality signal” is based on both metrics, and the signaling of the measured metrics is based on the metrics and the measured values as exemplified in the below figure. If the NTN specific criteria is not met a high quality indication based on RSRP may still apply.

FIG.9illustrates aspects of this embodiment. Turning toFIG.9, the additional measurement result specified is RTT. In operation900, the processing circuitry203may measure the RSRP and RTT on the frequency associated to a PLMN. In operation902, the processing circuitry203may determine whether the RSRP is greater than the specified RSRP threshold. Responsive to the RSRP not being greater than the RSRP threshold, the processing circuitry203may forward the identification of the PLMN and the measured RSRP to the NAS in operation904.

Responsive to the RSRP being greater than the RSRP threshold, the processing circuitry203may determine whether the RTT is less than the RTT threshold in operation906.

Responsive to the RTT being less than the RTT threshold, the processing circuitry203may forward the identification of the PLMN and a high-quality indication to the NAS in operation908. Responsive to the RTT not being less than the RTT threshold, the processing circuitry203may forward the identification of the PLMN and a high-quality RSRP indication to the NAS and the measured RTT value to the NAS in operation910.

FIG.10illustrates an embodiment where multiple additional measurements may be taken. In operation1000, the processing circuitry203may receive satellite positioning information and/or a list of a plurality of measurements to perform to find a PLMN to select. The plurality of measurements may include a plurality of different types of measurements. In some embodiments, one of the plurality of different types of measurements includes an RSRP measurement. IN additional or alternative embodiments, the list of the plurality of different types of measurements may include at least one of a reference signal received quality, RSRQ, measurement a signal-to-interference-plus-noise ratio, SINR, measurement a round trip time, RTT, measurement and a differential delay measurement. In some examples, a differential delay is a difference in propagation delay of UEs in the cell. In additional or alternative examples, a differential delay is the difference in distance between the UE and a satellite. The satellite positioning information may include at least one of a UE geographical position, a satellite elevation angle, a satellite orbital height, and satellite ephemeris data. The list may also provide the threshold to use in which to compare the measurement results for each of the plurality of different types of measurements. For example, the threshold for a measurement result may indicate whether the measurement result should be above or below the specified threshold value. The one or more measurements may depend on the capability of the UE as described above. When a specified measurement is satellite specific, a default comparison result may be specified for terrestrial based PLMNs. For example, if satellite elevation angle is specified and the threshold specified is being greater than or equal to a specified angle, the default comparison result for terrestrial based PLMNs is an indication of a “yes.” Alternatively, the comparison result may indicate that it is not applicable.

In operation1002, the processing circuitry203may perform the plurality of measurements on a frequency associated with a found PLMN. For example, a measurement of the RSRP and the additional specified measurements on the frequency associated with a found PLMN may be performed. In operation1004, the processing circuitry203may determine whether the RSRP is greater than the specified RSRP threshold. Responsive to the RSRP not being greater than the RSRP threshold, the processing circuitry203may forward the identification of the PLMN and the measured RSRP to the NAS in operation1006.

Responsive to the RSRP being greater than the RSRP threshold, the processing circuitry203may determine whether every additional measurement result in the plurality of measurement results is above or below the corresponding threshold as specified in operation1008. For example, if the additional specified measurement results are RTT and RSRQ, the thresholds may be RTT<RTTTHand RSRQ≥RSRQTH. Determining whether every additional measurement result in the plurality of measurement results is above or below the corresponding threshold as specified is determined when RTT<RTTTHand RSRQ≥RSRQTH.

Turning toFIG.11, in one embodiment, determine whether every additional measurement result in the plurality of measurement results is above or below the corresponding threshold as specified includes receiving, in operation1100, a plurality of thresholds, each of the plurality of thresholds corresponding to one of the plurality of measurement results and indicating whether the measurement result should be above or below a threshold value. For each of the plurality of measurement results, the measurement result is compared to a corresponding threshold of the plurality of thresholds in operation1102and a determination is made as to whether the measurement result is above or below the corresponding threshold in accordance with the indication of the corresponding threshold in operation1104. In operation1106, responsive to the measurement result being above or below the threshold in accordance with the indication for all of the plurality of measurement results, a determination is made that every additional measurement in the plurality of measurement results is above or below the corresponding threshold as specified. In operation1108, responsive to any measurement result not being above or below the threshold in accordance with the indication for the measurement, a determination is made that not every additional measurement result is above/below the threshold as specified.

Returning toFIG.10, responsive to every of the additional specified measurement results being above or below the thresholds as specified, the processing circuitry203may forward the identification of the found PLMN and a high-quality indication to the NAS in operation1010.

Responsive to any of the additional specified measurement results not being above or below the thresholds as specified, the processing circuitry203may forward the identification of the found PLMN with the high quality RSRP indication and the additional measurement results to the NAS in operation1012. For example, if RTT>RTTTHor RSRQ<RSRQTH, then the RTT and the RSRQ are not above or below the thresholds as specified.

In one embodiment a UE may be required to receive the NTN PLMN system information to acquire NTN specific information specified in the NTN PLMN system information such as satellite ephemeris data, satellite orbit altitude, NTN type (e.g., LEO, MEO, GEO), constellation size (e.g., number of satellites in the constellation), maximum supported RTT, and/or number of tracking areas supported by the PLMN. The UE AS may pass this information to the NAS together with the PLMN ID.

In one embodiment the UE NAS logic may rank and prioritize selection of a PLMN that qualifies as a high quality PLMN based on the AS measurements and information conveyed to NAS as described above. The NAS may also use the signalled AS information for ranking the PLMNs in case no high quality PLMN is identified.

FIG.12illustrates an embodiment where the UE NAS logic may prioritize PLMNs and select a PLMN based on the prioritization. In operation1200, the processing circuitry203may receive, from an access stratum layer, for each of a plurality of public land mobile networks, PLMNs, an identification of the PLMN and one of a plurality of measurements for the PLMN or a high-quality indication for the PLMN, the PLMN being one of a terrestrial PLMN or a non-terrestrial network, NTN, PLMN. The NTN PLMN may be a type of radio access technology (RAT) that is different from terrestrial PLMNs.

In operation1202, the processing circuitry203may prioritize the plurality of PLMNs based on the high-quality indication and the plurality of measurements. For example, if there are high-quality indications, the PLMNs associated with the high-quality indications may be prioritized over the PLMNs that are not associated with a high-quality indication. The PLMNs that are not associated with a high-quality indication are prioritized based on the measurements.

In another embodiment the PLMN selection may support a distinction between terrestrial and non-terrestrial networks. In one embodiment, the prioritizing may include prioritizing PLMNs based on PLMN type. Turning toFIG.13, in one embodiment, the processing circuitry203may, in operation1300, prioritize terrestrial PLMNs in the plurality of PLMNs to provide a terrestrial prioritization. In operation1302, the processing circuitry203may prioritize the NTN PLMNs in the plurality of PLMNs in a NTN prioritization separate from the terrestrial prioritization.

Returning toFIG.12, in operation1204, the processing circuitry203may select a PLMN to camp on from the plurality of PLMNs based on the prioritization. For example, if there are PLMNs having a high-quality indication, one of these PLMNs may be selected before a PLMN not having a high-quality indication may be selected. If there are no high-quality indications, then the selection may be based on the prioritization of the measurements. In one embodiment, the prioritization of the measurements may prioritize one type of measurement over another type of measurement. For example, an RTT measurement may take priority over a differential delay measurement such that a PLMN is selected based on the PLMN having a lower RTT measurement than other PLMNs.

In one embodiment the PLMN selection may support a distinction between terrestrial and non-terrestrial networks. PLMN selection can then be based on this distinction and whether the UE supports one or the other. This is illustrated inFIG.14.

Turning toFIG.14, in operation1400, the processing circuitry203may obtain an indication of whether to prioritize the terrestrial PLMNs over the NTN PLMNs. In operation1402, responsive to the indication indicating to prioritize the terrestrial PLMNs over the NTN PLMNs, the processing circuitry203selects a PLMN having a high-quality indication from the terrestrial prioritization. In operation1404, responsive to the indication indicating to prioritize the NTN PLMNs over the terrestrial PLMNs, the processing circuitry203selects a PLMN having a high-quality indication from the NTN prioritization.

Returning toFIG.12, in operation1206, the processing circuitry203may perform an action to camp on the selected PLMN.

In a further embodiment, the PLMN selection may support a distinction between different types of non-terrestrial networks, such as LEO, MEO and GEO. The PLMN selection from the plurality of PLMNs can then be based on this distinction. For example, the NTN PLMNs in the plurality of PLMNs may be prioritized based on a type of the NTN PLMN, wherein the type of the NTN PLMN comprises one of a low earth orbit, LEO, NTN, a medium earth orbit, MEO, NTN, or a geostationary orbit, GEO, NTN. An indication of a priority of which of the LEO PLMN, the MEO PLMN, and the GEO PLMN to select before selecting other PLMNs of the LEO PLMN, the MEO PLMN, and the GEO PLMN may be obtained and the selection of the PLMN to camp on may be in accordance with the priority. For example, responsive to receiving an indication of a PLMN for each of the LEO PLMN type, the MEO PLMN type, and the GEO PLMN type having a high-quality indication, the PLMN may be selected to camp on in accordance with the priority. The different type can also be based on satellite constellation size, orbit altitude, and/or RTT.

In another embodiment an NTN PLMN may be identified as a separate type of PLMN, known as, for example, a “N-PLMN”. The NTN PLMN applies to any existing type of PLMNs such as HPLMN (“N-HPLMN”). This new PLMN type may be used to refine the PLMN selection based on PLMN type.

In a further embodiment, the NTN may be identified as a separate access technology in 3GPP TS 23.122. Existing PLMN selection functionality based on access technology may then include NTN. Different types of NTNs, i.e. LEO, MEO, GEO, may be identified as separate access technologies to refine the PLMN selection based on access technology.

In another embodiment the PLMN selection may be based on the RTT.

In another embodiment the PLMN selection may be complemented with a set of requirements based on NTN characteristics such as orbit height, RTT or satellite ephemeris data. This information can be signalled from the AS as outlined above. One requirement may be that a UE with guaranteed bit rate, low latency requirements or high reliability requirements should ignore NTN PLMNs. In other words, the NTN PLMN is not prioritized. Another example is that UE with high requirements on battery life may deprioritize a PLMN with many tracking areas since this may be associated with heavy tracking area update signalling.

Explanations are provided below for various abbreviations/acronyms used in the present disclosure.

References are Identified Below.[1] TR 38.811, Study on New Radio (NR) to support non-terrestrial networks[2] RP-181370, Study on solutions evaluation for NR to support non-terrestrial Network

Additional explanation is provided below.

ABBREVIATIONS

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).1×RTT CDMA2000 1× Radio Transmission Technology3GPP 3rd Generation Partnership Project5G 5th GenerationABS Almost Blank SubframeARQ Automatic Repeat RequestAWGN Additive White Gaussian NoiseBCCH Broadcast Control ChannelBCH Broadcast ChannelCA Carrier AggregationCC Carrier ComponentCCCH SDU Common Control Channel SDUCDMA Code Division Multiplexing AccessCGI Cell Global IdentifierCIR Channel Impulse ResponseCP Cyclic PrefixCPICH Common Pilot ChannelCPICH Ec/No CPICH Received energy per chipdivided by the power density in the bandCQI Channel Quality informationC-RNTI Cell RNTICSI Channel State InformationDCCH Dedicated Control ChannelDL DownlinkDM DemodulationDMRS Demodulation Reference SignalDRX Discontinuous ReceptionDTX Discontinuous TransmissionDTCH Dedicated Traffic ChannelDUT Device Under TestE-CID Enhanced Cell-ID (positioning method)E-SMLC Evolved-Serving Mobile Location CentreECGI Evolved CGIeNB E-UTRAN NodeBePDCCH enhanced Physical Downlink Control ChannelE-SMLC evolved Serving Mobile Location CenterE-UTRA Evolved UTRAE-UTRAN Evolved UTRANFDD Frequency Division DuplexFFS For Further StudyGERAN GSM EDGE Radio Access NetworkgNB Base station in NRGNSS Global Navigation Satellite SystemGSM Global System for Mobile communicationHARQ Hybrid Automatic Repeat RequestHO HandoverHSPA High Speed Packet AccessHRPD High Rate Packet DataLOS Line of SightLPP LTE Positioning ProtocolLTE Long-Term EvolutionMAC Medium Access ControlMBMS Multimedia Broadcast Multicast ServicesMBSFN Multimedia Broadcast multicast service Single Frequency NetworkMBSFN ABS MBSFN Almost Blank SubframeMDT Minimization of Drive TestsMIB Master Information BlockMME Mobility Management EntityMSC Mobile Switching CenterNPDCCH Narrowband Physical Downlink Control ChannelNR New RadioOCNG OFDMA Channel Noise GeneratorOFDM Orthogonal Frequency Division MultiplexingOFDMA Orthogonal Frequency Division Multiple AccessOSS Operations Support SystemOTDOA Observed Time Difference of ArrivalO&M Operation and MaintenancePBCH Physical Broadcast ChannelP-CCPCH Primary Common Control Physical ChannelPCell Primary CellPCFICH Physical Control Format Indicator ChannelPDCCH Physical Downlink Control ChannelPDP Profile Delay ProfilePDSCH Physical Downlink Shared ChannelPGW Packet GatewayPHICH Physical Hybrid-ARQ Indicator ChannelPLMN Public Land Mobile NetworkPMI Precoder Matrix IndicatorPRACH Physical Random Access ChannelPRS Positioning Reference SignalPSS Primary Synchronization SignalPUCCH Physical Uplink Control ChannelPUSCH Physical Uplink Shared ChannelRACH Random Access ChannelQAM Quadrature Amplitude ModulationRAN Radio Access NetworkRAT Radio Access TechnologyRLM Radio Link ManagementRNC Radio Network ControllerRNTI Radio Network Temporary IdentifierRRC Radio Resource ControlRRM Radio Resource ManagementRS Reference SignalRSCP Received Signal Code PowerRSRP Reference Symbol Received Power ORReference Signal Received PowerRSRQ Reference Signal Received Quality ORReference Symbol Received QualityRSSI Received Signal Strength IndicatorRSTD Reference Signal Time DifferenceSCH Synchronization ChannelSCell Secondary CellSDU Service Data UnitSFN System Frame NumberSGW Serving GatewaySI System InformationSIB System Information BlockSNR Signal to Noise RatioSON Self Optimized NetworkSS Synchronization SignalSSS Secondary Synchronization SignalTDD Time Division DuplexTDOA Time Difference of ArrivalTOA Time of ArrivalTSS Tertiary Synchronization SignalTTI Transmission Time IntervalUE User EquipmentUL UplinkUMTS Universal Mobile Telecommunication SystemUSIM Universal Subscriber Identity ModuleUTDOA Uplink Time Difference of ArrivalUTRA Universal Terrestrial Radio AccessUTRAN Universal Terrestrial Radio Access NetworkWCDMA Wide CDMAWLAN Wide Local Area Network

Further definitions and embodiments are discussed below.