CN114223240A

CN114223240A - Paging optimization based on mobile device proximity

Info

Publication number: CN114223240A
Application number: CN202080051272.8A
Authority: CN
Inventors: A·施密特; A·卢夫特; M·别纳斯; M·汉斯
Original assignee: Ipcom GmbH and Co KG
Current assignee: Ipcom GmbH and Co KG
Priority date: 2019-07-17
Filing date: 2020-07-17
Publication date: 2022-03-22
Anticipated expiration: 2040-07-17
Also published as: CN114223240B

Abstract

The invention provides a method for executing paging action aiming at second user equipment, UE and equipment in a mobile communication system, which comprises the steps of sending a configuration message from a first base station to first UE equipment so as to configure the first UE equipment to send a paging indication at a preset time under the condition of determining that a geographical condition is met; and transmitting a paging message from one of the first base station and the second base station to the second UE device after the paging indication is sent.

Description

Paging optimization based on mobile device proximity

Technical Field

The present invention relates to paging procedures in cellular communication systems, for example, those operating in accordance with the 4G-LTE suite of specifications of the 3GPP or its successor technology (commonly referred to as 5G-NR).

Background

In 4G-LTE, the Radio Access Network (RAN) consists of base stations called enbs, which provide user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards mobile communication devices (UEs). The enbs are connected to each other via an X2 interface. The eNB is also connected to the Core Network (CN) via an S1 interface, and more particularly to a Mobility Management Entity (MME) responsible for C-plane traffic via an S1-MME interface and to a serving gateway (S-GW) responsible for U-plane traffic via an S1-U interface. The S1 interface supports a many-to-many relationship between the MME/S-GW and the eNB.

Disclosure of Invention

Each base station of a cellular communication system may control the communication of the air interface within its geographical coverage area, i.e. within its radio cell. When a mobile communication device (UE) is located within the coverage area of a radio cell and camped on it (in other words, when it is registered with the radio cell providing coverage), it can communicate with the base station controlling the radio cell. When a user of a mobile communication device initiates a call or a call is addressed to the mobile communication device, a radio channel may be established between the mobile communication device and a base station controlling a radio cell in which the mobile communication device is located.

As the mobile communication device continues to move throughout the coverage area of the cellular communication system, control of the call may be transferred between adjacent radio cells. The transfer of a call from one radio cell to another is commonly referred to as handover (or handoff). Handover is typically based on network configured measurements made by the UE (e.g., on different overlapping and/or neighboring radio cells).

In this case, the term "call" is intended to cover various scenarios in which user data is exchanged one-way or two-way over the air interface, which is part of an active connection between a serving base station and a mobile communication device. For example, it may be a voice telephone, a data telephone, internet data traffic, and other forms.

Another interface for device-to-device direct communication (D2D) is defined in 3 GPP. Such interfaces are illustrated in fig. 1 using 4G-LTE terminology. The same interface exists in the 3GPP successor technology 5G-NR.

Two mobile communication devices (UEs) within or outside the coverage of a system radio cell may communicate with each other to enable certain services (or applications), such as "public safety" or "vehicle-to-vehicle communication. For the case that the direct device-to-device communication must be performed in areas where network coverage cannot be guaranteed, 3GPP has proposed three different usage scenarios —

(1) Case within coverage: the network controls the resources used for D2D communication.

(2) Out-of-coverage cases: the UE uses resources pre-configured in the USIM of the mobile device or UICC card. However, the term "out of coverage" must be interpreted with caution. It is not meant to be completely uncovered, but rather means that there is no coverage on the frequency used for D2D communication, although the UE may be covered on another carrier used for cellular communication.

(3) Case of partial coverage: out-of-coverage UEs use preconfigured values, while in-coverage UEs obtain their resources from the base station. Careful coordination of the network and preset values is necessary to enable communication and limit interference to UEs located at cell borders near out-of-coverage UEs.

In conventional cellular communications, such as over the LTE Uu air interface, an eNB communicates with a UE in both the Uplink (UL) direction (i.e., from handset to beacon) and the Downlink (DL) direction (i.e., from beacon to handset). With the introduction of the LTE PC5 air interface into the Sidelink (SL), this concept is extended to use cases for direct communication between various devices.

Drawings

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 illustrates a connection for direct communication between devices according to 3GPP specifications;

FIG. 2 illustrates radio resource control states and state transitions between 4G-LTE and 5G-NR;

FIG. 3 illustrates an example of a paging message;

FIG. 4 illustrates one example of a subframe structure defined for 4G-LTE;

FIG. 5 illustrates a schematic diagram of messages transmitted in accordance with the present invention;

FIG. 5a illustrates transmission of a paging indication and a paging message;

FIG. 6 is an information sequence chart illustrating an implementation of the present invention when two UEs are served by the same base station;

FIG. 7 is an information sequence chart illustrating an implementation of the present invention when two UEs are served by different base stations;

FIG. 8 illustrates a first configuration option;

FIG. 9 illustrates a second configuration option;

figure 10 illustrates a paging indication transmitted in a sidelink resource;

FIG. 11 illustrates a paging indicator transmitted in a downlink resource; and

fig. 12 illustrates a case where the paging indication and the paging message are not transmitted in the same subframe.

Detailed Description

Fig. 2 illustrates a Radio Resource Control (RRC) protocol state diagram according to 3GPP TS 38.331. The figure also illustrates inter-RAT mobility support between 4G-LTE (left schematic) and 5G-NR (right schematic).

After the RRC connection is established, the mobile communication device (UE) is either in an RRC _ CONNECTED state or in an RRC _ INACTIVE state. If this is not the case, i.e. no RRC connection is established, the UE is in RRC _ IDLE state. The RRC state may be further described as follows:

RRC_IDLE：

UE-specific DRX is configurable by upper layers;

mobility is controlled by the UE (based on network configuration);

-the UE monitoring the DL control channel to detect a paging indication;

-the UE performs neighbor cell measurements and cell (re) selection;

the UE acquires system information and may send SI requests (if configured).

RRC_INACTIVE：

UE-specific DRX may be configured by upper layers or RRC layers;

mobility is controlled by the UE (based on network configuration);

-the UE storing a "UE inactive" Access Stratum (AS) context;

-a RAN-based notification area is configured by the RRC layer;

-the UE monitoring the DL control channel to detect a paging indication;

-the UE performs neighbor cell measurements and cell (re) selection;

-the UE performing a RAN-based notification area update;

acquire system information and may send SI requests (if configured).

RRC_CONNECTED:

-the UE storing a "UE activated" Access Stratum (AS) context;

-unicast data may be transmitted to/from the UE;

at lower layers, the UE may be configured with UE-specific DRX;

-for a UE supporting Carrier Aggregation (CA): one or more secondary cells (scells) may be aggregated with a particular cell (SpCell) to increase bandwidth;

-for a UE supporting Dual Connectivity (DC): one Secondary Cell Group (SCG) may be aggregated with a Master Cell Group (MCG) to increase bandwidth;

-mobility is controlled by the network;

-the UE monitoring the DL control channel to detect a paging indication;

-the UE monitoring the DL control channel to detect resource allocation conditions;

-the UE providing channel quality and feedback information;

-the UE performing neighbor cell measurements and measurement reporting;

-the UE acquiring system information.

Paging is a mechanism by which the infrastructure side tells the mobile communication device that i have something to give you. In most cases, the paging procedure is initiated when the mobile communication device is in a reduced power consumption state (e.g., in an RRC IDLE or RRC INACTIVE mode of operation). However, paging may also occur when the UE has a persistent connection with its serving base station (e.g., while in RRC _ CONNECTED mode of operation).

In early wireless communication systems, such as 3G-UMTS, a special physical channel was provided in the downlink for mobile communication devices to detect paging information. This paging indicator channel is specifically designed to enable the mobile communication device to periodically wake up its receiver (for a short period of time to minimize the impact on battery life) to detect a paging indicator (typically assigned to a group of UEs). The mobile communication device will then keep its receiver on to receive longer messages indicating the exact identity of the called UE.

In 4G-LTE and 5G-NR communication systems, no such separate physical channel is used for this purpose. While the Physical Downlink Shared Channel (PDSCH) is used for paging messages, the indication is provided through a Physical Downlink Control Channel (PDCCH). The duration of PDCCH signaling is already short and therefore monitoring the PDCCH from time to time has a low impact on battery life. Thus, normal PDCCH signaling may be used to carry (information equivalent to) paging indications, while detailed paging information is carried over PDSCH in the resource blocks indicated by PDCCH. The paging indication sent on the PDCCH uses a single fixed identity called P-RNTI (paging radio network temporary identity). Instead of providing different paging identifiers for different (groups of) UEs, different (groups of) UEs are configured to monitor paging messages of different subframes (their paging occasions). A paging message typically consists of several paging records (up to 32), each for a particular UE. One UE may be identified by the UE-identity carried in the paging message. This in turn means that all UEs that happen to get a paging indication (at the respective paging occasion) need to receive, decode and analyze the whole paging message even if there is no paging record associated with them. In a practical deployment, the number of UEs sharing one paging occasion may be quite high (i.e. much larger than 32).

The paging procedure may be initiated in the following scenario:

transmitting paging information to the UE maintained in the RRC _ IDLE or RRC _ INACTIVE state to trigger an RRC connection setup or RRC connection recovery procedure (see fig. 2);

notifying the UE in the above three RRC states of a change in SI (system information);

the UE in the above three RRC states is informed about notification of PWS (public warning system).

Paging means that the mobile communication device is to constantly monitor certain downlink resources on the PDCCH to check whether the network is sending a paging indication. The paging indication indicates that corresponding paging information is to be transmitted on the PDSCH.

In the context of the present invention, the term "paging data" includes both a "paging indication" (possibly in the form of a P-RNTI on the PDCCH) and the actual "paging message" (possibly transmitted on the PDSCH and possibly containing several "paging records" for different UEs). According to the prior art, the "paging message" always follows the "paging indication" in the PDSCH region of the same subframe. A paging record is a set of information that is specific to a particular mobile communication device. Fig. 3 illustrates the structure of a known paging message defined for 4G-LTE.

A paging message may include up to 32 paging records. Each paging record may include a UE-Identifier (e.g., IMSI or S-TMSI) and a CN-Domain indicator (e.g., CS for circuit switched or PS for packet switched). The remaining information elements relate to system information updates (SI modification) or various common warning system (PWS) indications, followed by further optional information elements (depending on the release number of the specification), such as parameters controlling access barring, inter-frequency reallocation, or BCCH modification indications for UEs using eDRX.

In some cases, the structure of the paging message may be different from that shown in fig. 3 because it includes only one paging record list. In this case, the SI modification and the indication of PWS are contained in a single 8-bit word, called "short message/sms", which may be carried on the PDCCH (in some types of DCI).

If a mobile communication device in an RRC IDLE or RRC INACTIVE mode of operation is paged, paging data received by the mobile communication device may trigger it to enter a full mode of operation. For example, if user data is already available to the mobile communication device on the infrastructure side (an event known as "downlink data arrival"), the mobile communication device may be called and change from an RRC IDLE or RRC INACTIVE operating state to an RRC CONNECTED operating state (refer to the RRC connection recovery or RRC connection establishment procedure shown in fig. 2).

Fig. 4 shows a simplified version of a subframe structure of a downlink (tower to handset) resource grid used in a wireless communication system according to 4G-LTE. One subframe may include two regions, a Control Channel Region (CCR) and a Shared Channel Region (SCR). The CCR may (primarily) contain PDCCH/PCFICH physical channels, while the SCR may (primarily) contain PDSCH physical channels. For simplicity, the broadcast channel region (i.e., the region where the PBCH physical channel is located) and the synchronization signals (e.g., P-SS and S-SS) are not shown in fig. 4. In the case of 4G-LTE, ten consecutive subframes constitute one radio frame with a total length of 10 milliseconds.

The sub-frame defined for the 5G-NR may also contain one CCR and one SCR, but the arrangement of the zones may deviate slightly from that shown in fig. 4, since the resource grid of the 5G-NR generally allows more flexibility.

For example, in 5G-NR, CCR may be represented in the form of a set of control resources (CORESET) that do not extend over the entire bandwidth of the carrier. Furthermore, the CCR of the 5G-NR may not be scheduled to occupy the first OFDM symbol in a given subframe. Nevertheless, the principles of the method described below can be readily applied to 5G-NR.

In order to efficiently utilize radio resources, the paging procedures of 4G-LTE and 5G-NR are designed to have the following characteristics:

more than one mobile communication device monitors the same paging occasion on the PDCCH;

the paging record list in the paging message enables the network to process sudden paging requests, i.e. to process instantaneous high-load paging requests;

therefore, congestion of paging (i.e., paging messages cannot be sent) can be minimized.

From the UE perspective, receiving a paging indicator at a given paging occasion requires all mobile communication devices assigned to that paging occasion to receive, decode and interpret the entire contents of a subsequent paging message, which typically consists of multiple (up to 32) paging records. Flipping through all of these records is an arduous process. All mobile communication devices receiving a paging indication on a respective paging occasion are obligated to perform this procedure even if no dedicated paging record is included in the paging message about them. In the most advanced technology, the number of UEs sharing one paging occasion may be quite high (i.e. much larger than 32).

Only mobile communication devices that find a matching UE-identity in any of the paging records will take action on the paging message. It is likely that most mobile communication devices will eventually find a paging record that does not match them after going through the process of receiving, decoding and analyzing the content of the paging message. These devices parse the content of the paging message, but are futile. In the context of the present invention, this is referred to as "false alarm in paging" (FAP).

The document WO 2017/099837 a1 describes a UE that is a relay of remote UEs. The processing circuitry of the remote UE detects a paging message from an eNodeB of the ProSe network over an air interface between the eNodeB and the remote UE, or over a PC5 interface between the relay UE and the remote UE through a relay UE of the ProSe network.

WO 2018/028279 a1(EP 3449975 a1) describes a technique for discontinuous reception over a PC5 interface, with a relay UE performing paging for remote UEs.

US 10,117,223B 1 describes a system in which a relay base station may be used to make a call to a corresponding device of a donor base station communicating with the relay base station. EP 3113548 a1 describes an arrangement in which, in order for one UE to connect to another UE over a D2D sidelink, a first UE requests a serving eNB to call a second UE, which sends a page to the first UE.

In another aspect, the present invention provides a method of performing a paging action for a user equipment, UE, device in a mobile communication system, the method comprising configuring another UE device to transmit a paging indicator when it is determined that the UE device satisfies a geographical condition; and transmitting the paging message from the base station to a UE device after the paging indicator is transmitted.

The invention also provides a UE device arranged to receive a paging indication from another UE device and in response to the indication to configure itself to receive a paging message corresponding to the paging indication from a base station.

Preferred aspects of the invention are provided according to the dependent claims.

It is an object of the present invention to minimize the number of false positives in paging. This is achieved by exploiting the proximity knowledge of mobile communication devices capable of direct inter-device communication and configuring the relevant mobile communication devices accordingly. According to the invention, the paging indicator is no longer transmitted over the Uu air interface within the entire coverage area of the radio cell. Conversely, when a page indication is detected as being close, it is propagated by the selected mobile communication device to the associated neighboring mobile communication devices over the PC5 air interface. The paged neighboring mobile communication device may then wake up to receive subsequent paging messages from the base station over the Uu air interface.

According to a first aspect of the present invention, a first mobile communications device may be configured to propagate a page indication over the PC5 air interface to a second mobile communications device that the network wishes to call. The second (paged) mobile communications device will receive a subsequent paging message from the base station over the Uu air interface. Thus, the two parts that make up the paging data (i.e., "paging indication" and "paging message") are decoupled from one another.

A second aspect of the invention relates to identifying a proximity relationship between a first mobile communication device and a second (paged) mobile communication device. The second mobile communication device may be a stationary or quasi-stationary communication device whose location is known (at least at certain boundaries) by the infrastructure side. In one embodiment, the second mobile communication device is embedded in or connected to an internet of things (IoT) device, such as a smart meter, roadside equipment, a vending machine, a sensor, or an actuator. In another embodiment, the second mobile communication device is configured to have a special sleep period, which may be much longer than the sleep periods of other mobile communication devices in the same cellular communication network.

The configuration procedure of the first mobile communication device for implementing the method of the invention is a third aspect of the invention. Preferably, the configuration is performed while the communication device resides in the RRC _ CONNECTED mode of operation. The configuration may include location information and/or time information for sending a paging indication. The former may assist a first mobile communication device in sending a paging indicator when in proximity to a second mobile communication device that the network wishes to call. The latter may assist the first mobile communication device to send a paging indication to the second mobile communication device at the correct point in time (e.g. taking into account the sleep period of the second mobile communication device).

According to a fourth aspect of the invention, transmission of paging indicators (whether on sidelink or downlink radio resources) between adjacent mobile communication devices is enabled. In order to make this work free from any interference from the PDCCH transmitted by the radio cell, some refinements of resource coordination are described in a fifth aspect of the invention.

According to a fifth aspect of the invention, some parts of the Control Channel Region (CCR) are not used (left empty) by the base station. This is arranged to avoid resource collision (interference) between subframes transmitted by the first mobile communications device over the PC5 interface and subframes transmitted by the base station over the Uu air interface.

According to a sixth aspect of the invention, a timing relationship is defined between the paging indicator (transmitted according to the fourth aspect described above) and the subsequent paging message (transmitted over the Uu air interface). Unlike most advanced deployments, this timing relationship may span different subframes (e.g., the control channel region transmitting the paging indicator and the shared channel region transmitting the subsequent paging message may no longer be located within the same subframe).

The invention can reduce the occurrence of FAP. In detail, the number of mobile communication devices that have to undergo receiving, decoding and analyzing the content of paging messages without actual paging can be greatly reduced. This is particularly advantageous for internet of things devices such as smart meters, sensors or actuators, which are often severely limited in power consumption.

By utilizing the proximity knowledge of mobile communication devices capable of inter-device direct communication and configuring the location and time parameters of the participating mobile communication devices accordingly, the paging procedure can be improved. According to the invention, the paging indicator is no longer transmitted over the Uu air interface within the entire coverage area of the radio cell. Conversely, when a page indication is detected as being close, it is propagated by the selected mobile communication device to the associated neighboring mobile communication devices over the PC5 air interface. The paged neighboring mobile communication device may then wake up to receive subsequent paging messages from the base station over the Uu air interface.

A first aspect of the invention relates to the decoupling of the paging indication from the paging message.

The first mobile communication device may be configured by the infrastructure side to propagate the page indication over the PC5 air interface (either on the sidelink radio resource or on the downlink radio resource through analog base station functionality) to the adjacent second mobile communication device that the network wishes to call. The second (paged) mobile communications device will receive subsequent paging messages for the base station over the conventional Uu air interface.

Fig. 5 depicts how the two parts constituting the paging data are decoupled from each other and sent from different entities: step 1 represents the configuration process of the mobile communication device and will be discussed in more detail in connection with the third aspect of the invention. In step 2, a paging indication is sent by the first mobile communication device (UE1), and step 3 describes the transmission of a paging message by the base station. The paging indication may be transmitted from UE1 to UE2 over the sidelink resources over the PC5 air interface, as shown in fig. 5 a. Another option for transmitting a paging indication from the UE1 to the UE2 is for the UE1 to provide downlink resources (e.g., resources used over the Uu air interface) to emulate some base station functionality (not shown in fig. 5). These two different schemes are discussed in more detail below in connection with the fourth aspect of the invention.

Fig. 6 shows a message sequence chart in accordance with one embodiment of the present invention in which both the first mobile communication device (UE1) and the second mobile communication device (UE2) are served by the same base station. UE1 may be a normal UE and UE2 may be an internet of things device that may have been configured with a sleep cycle that is much longer than the sleep cycles of other normal communication devices in the same cellular communication network. The sleep period of the UE2 may be known to the infrastructure side (e.g., may be stored in a memory of the core network entity or RAN entity).

At point a of fig. 6, the base station BS1 decides (or receives an indication to do so from the core network) to configure the (at least one) UE1 to transmit a paging indication to other mobile communication devices in the vicinity (e.g., over the PC5 air interface). For this purpose, the configuration information needs to contain some detailed information about the target mobile communication device (i.e. the device to be paged), e.g. at least one piece of information relating to the target device's sleep period, potential wake-up time, configured paging occasion, location data, deployment details, preferred paging mode (e.g. on sidelink or downlink resources), etc. The UE1 receives the configuration message at point B. From now on, the UE1 periodically or continuously checks for time and/or location requirements to send paging indicators to nearby mobile communication devices. This is indicated at point C in fig. 6. In some cases it may be beneficial to check certain parameters in a sequential order, for example, first checking time criteria and then (when a paging occasion is imminent or a sleep cycle is imminent) checking location criteria. To this end, the UE1 may compare the output of a GNSS receiver or similar location determination module to the location request received from the configuration information of the base station. If all of these (and possibly further criteria) are met (see point F), the UE1 may send a paging indication to mobile communication devices in its vicinity over the PC5 air interface (on either the sidelink resources or the downlink resources, as desired by the UE 2). In this example, the UE2 receives the paging indicator at point G. The UE2 is now expected to receive subsequent paging messages sent by the base station at the correct point in time (e.g., after a relative amount of time tp). The UE2 receives the paging message at point H. This message can now be processed to find a matching paging record. Thus, further activities (such as random access attempts to the base station BS 1) may be initiated.

Fig. 7 shows a message sequence chart in accordance with another embodiment of the invention in which a first mobile communication device (UE1) and a second mobile communication device (UE2) are served by different base stations. Likewise, the UE1 may be a normal UE and the UE2 may be an internet of things device that may be configured with a sleep period that is significantly longer than the sleep periods of other normal communication devices in the same cellular communication network. The sleep period of the UE2 may be known to the infrastructure side (and may, for example, be stored in a memory of the core network entity or RAN entity).

At point a' of fig. 7, the base station BS1 decides (or receives an indication to do so from the core network or from other RAN nodes, e.g., base station BS 2) to configure the (at least one) UE1 to transmit a paging indication to other mobile communication devices in the vicinity (e.g., over the PC5 air interface). In this example scenario, another mobile communication device (i.e., the device to be paged) is served by base station BS 2. The configuration message may need to contain some detailed information about the target mobile communication device, for example, there should be at least one piece of information about the target device's sleep cycle, potential wake-up time, configured paging occasions, location data, deployment details, preferred paging scheme (e.g., on sidelink resources or downlink resources), etc. In addition, the configuration message needs to contain base station related information (e.g., base station identification directed to BS 2) that serves other mobile communication devices. The UE1 receives the configuration message at point B'. From now on, the UE1 periodically or continuously checks for time and/or location requirements to send paging indicators to nearby mobile communication devices. This is indicated by point C' in fig. 7. In some cases it may be beneficial to check certain parameters in a sequential order, for example, first checking time criteria and then (when a paging occasion is imminent or a sleep cycle is imminent) checking location criteria. To this end, the UE1 may compare the output of the GNSS receiver or similar location determination module to the location request received from the configuration message of the base station. If certain criteria are met (see point D'), the UE1 may initiate a random access procedure with the base station BS2 to obtain a Timing Advance (TA) value for communication between the base station BS2 and the UE 2. The UE1 receives random access response information containing TA1 at point E'. We assume here that the distance between the UE1 and the UE2 is relatively small (e.g., in the range of 100 meters or less), so the timing advance value of the communication between the base station BS2 and the UE1 (TA1) and the timing advance value of the communication between the base station BS2 and the UE2 (TA2) are the same or at least very similar. When all transmission criteria (as defined in the configuration message) are met, the UE1 can calculate the exact time to transmit the paging indicator to mobile communication devices in its vicinity (see point F') while taking into account the timing advance value for communications between the base station BS2 and the UE2 (TA2) derived from TA 1. UE1 may transmit paging indications on sidelink resources or downlink resources over the PC5 air interface, as desired by UE 2. In this example, the UE2 receives the paging indicator at point G'. Now, the UE2 expects to receive a subsequent paging message transmitted by its serving base station BS2 at the correct point in time (e.g., after a relative amount of time tp). The UE2 receives the paging message at point H'. This message can now be processed to find a matching paging record. Thus, further activities (such as random access attempts to the base station BS 2) may be initiated.

Points D 'and E' in fig. 7 represent a simplified version of the random access procedure ("2-Step RACH") that contains only two messages. In some embodiments, the random access procedure consists of a total of four messages ("4-Step RACH") exchanged between the UE1 and the BS 2. We further propose to expand the range of values of the information element "establishment cause" that can be used, for example, for RRC connection setup messages (in the case of 4G-LTE this is the third message exchanged in the "4-step RACH" random access procedure, not shown in fig. 7) to enable the UE1 to signal to the base station BS2 that the purpose of the random access attempt is to find out the Timing Advance (TA) of another mobile communication device in its vicinity according to the paging method disclosed in the present invention. For example, the new value of the "establishment cause" may be set to "timing-advance for-PC 5" (or the like). The base station, upon receiving the RRC connection setup message with the "establishment cause" set to such new value, will know that the purpose of this random access procedure is not to establish a bearer between the UE1 and the core network for instant messaging. It will therefore alleviate some of the processing burden of the base station. This also helps to inhibit load balancing operations, if any.

A second aspect of the invention relates to identifying adjacency relationships.

Using the known "D2D ProSe direct discovery" procedure would be an option to detect proximity between two mobile communication devices. However, this process is accompanied by an exchange of information over the air interface of the PC 5.

In the present case, the goal is to have the second mobile communication device remain in sleep mode for as long as possible. Thus, it is not contemplated to have the second mobile communication device communicate any extensive information with potentially nearby devices over the PC5 air interface.

Thus, in order for the proposed method to work satisfactorily, the first mobile communication device needs to be provided by the network with a paging occasion suitable for the potential second mobile communication device (at a particular location). The infrastructure will need to maintain a database in either the RAN (for RAN-initiated paging if the second mobile communication device concerned resides in RRC _ INACTIVE mode of operation) or the CN (for CN-initiated paging if the second mobile communication device concerned resides in RRC _ IDLE mode of operation).

According to this aspect of the invention, the proximity between two mobile communication devices may be detected by the first mobile communication device according to a network configuration. It is proposed to include in the configuration data geographical parameters ("location data") determined or predicted in terms of the infrastructure. The configuration process itself will be discussed in more detail in the context of the third aspect of the invention described below.

With respect to geographic parameters, a location on the earth can be represented by latitude and longitude. The latitude (which may be abbreviated as Lat, phi or phi) is the angle between the equatorial plane and a line projected at the center of a reference ellipsoid that approximates the shape of the earth to illustrate the features of the earth's flat poles and equatorial crown. The lines connecting the points at the same latitude are called the latitude lines, and the trajectories of the latitude lines on the earth surface are concentric circles and parallel to the equator. North pole is 90 ° north latitude; the south pole is 90 ° latitude. The 0 ° parallel to the latitude, designated as the equator, is the fundamental plane of all geographic coordinate systems. The equator divides the globe into the northern hemisphere and the southern hemisphere. Longitude (which may be abbreviated Long, λ or lambda) refers to the east or west angle between a reference meridian between two geographic poles and another meridian passing through an arbitrary point. All the meridian lines are half of the great circle and are not parallel. They meet at the north and south poles. One line passing through the royal astronomical stage of greenwich (near london, uk) is selected as the international zero longitude reference line, i.e. the present elementary meridian. The east of the primary meridian is in the eastern hemisphere and the west is in the western hemisphere. The primitive meridian of greenwich is 180 ° for the west meridian and 180 ° for the east meridian.

Table 1 shows that the location of an example can be expressed in two different ways or formats. The second row of table 1 illustrates latitude and longitude in decimal value format. The third row illustrates the same latitude and longitude in degrees, minutes, seconds format. Each data format can be easily translated or converted to another data format. In combination with latitude and longitude values, any position of any point on the earth's surface can be specified. They may be supplemented with an additional altitude value to specify the location of a point above average sea level (not shown in table 1 for simplicity). The geographic parameters used in the present invention may consist of any combination of latitude, longitude and altitude in any format.

TABLE 1

	Decimal fraction	Degree-minutes-seconds
			Latitude (phi)	North latitude 52.264667	52 DEG 15 '52.80' north
Longitude (Lambda)	Dongding Jing 10.523776	10 DEG 31 '25.59' east

Furthermore, in terms of geographic parameters, the distance between two mobile communication devices may be defined by a reference point and a maximum allowed distance. For example, if a first mobile communication device finds that it is approaching a given location (or entering an area around a given reference point) by comparing output data from a Global Navigation Satellite System (GNSS) receiver or similar location determination module with its location information configured for the method of the present invention, then a proximity detection event occurs. In this case, the first mobile communication device may start sending paging indications to one or more second mobile communication devices according to its configuration, which the network considers to be in the vicinity of the first mobile communication device. Of course, in doing so, the first mobile communication device needs to take into account all other configuration parameters it receives in the configuration data set (e.g. related to timing requirements, resources to be used over the PC5 air interface, etc.).

A third aspect of the invention relates to configuring a first mobile communication device.

The present invention describes two configuration options for the innovative approach. In both options, a set of configuration data sets is transmitted from the network to the first mobile communication device in subframe n. The configuration data set may refer to a subframe (n + x) occurring at a later point in time (if x1) or to the same subframe (n) in which it was received by the first mobile communications device (if x ═ 0). Alternatively, the configuration data may also contain a subframe pattern, and thus may refer to more than one subframe that will occur at a later point in time.

According to one embodiment of the invention, the configuration data set contains location information, such as geographical parameters (list), or cell IDs (list), and similar information (generally referred to as "location data"). The geographic parameters may be determined or predicted on the infrastructure side or read from a database.

According to another embodiment of the invention, the set of configuration data contains timing information, which may include a relative time indication (e.g. "the configuration applies within three subframes from now on" or "the configuration applies within 3 milliseconds from now on") and/or a timing reference (e.g. in the form of a base station identifier (list)), and similar information. If UE1 and UE2 are camped on different base stations (e.g., consisting of a macro base station layer and a small base station layer) in a heterogeneous network (HetNet) deployment, the base station identifiers (lists) may help UE1 calculate the exact point in time to send the paging indication. From the base station identifier, the UE1 may find a Timing Advance (TA) suitable for a base station providing cell coverage for the UE2 (e.g., after random access to the cell). Since the frame timing of the cell serving UE1 may be different from the frame timing of the cell in which UE2 resides, the TA determined by performing random access on another cell may be used by UE1 to calculate the exact point in time to transmit a paging indication to UE 2. Details about such random access are contained in the first aspect described above (see description of fig. 7).

The first configuration option is shown in fig. 8.

The configuration data is transmitted from the network to the first mobile communication device at the physical layer (i.e. on the PDCCH) via Downlink Control Information (DCI) elements (see fig. 8). The DCI element may be an enhancement/modification to an existing DCI element or may be newly designed to support a configuration method.

The DCI may be addressed to a particular first mobile communications device (using a single RNTI) or a Group of first mobile communications devices (using a newly defined Group-RNTI). In fig. 8, subframe 1 is transmitted by the infrastructure side (base station). Subframe 2 represents the same subframe as received by the first mobile communication device. The "C" field in the CCR indicates that the configuration data is transmitted from the network to the first mobile communication device through the DCI element.

A second configuration option is shown in fig. 9.

The configuration data is transmitted from the network to the first mobile communication device at the RRC layer by RRC signaling (see fig. 9). For this RRC signaling, the existing downlink RRC message may be enhanced/modified or a completely new RRC message designed to support the configuration method. One type of RRC message is for all UEs within a given radio cell coverage (broadcast RRC signaling), while another type of RRC message is for a single UE (dedicated RRC signaling). The method of the present invention is not limited to either of these two types of RRC messages. According to the invention, the network is free to choose whether to use broadcast RRC signalling or dedicated RRC signalling to communicate the set of configuration data to the one or more first mobile communication devices over the Uu air interface.

In fig. 9, subframe 1 is transmitted by the infrastructure side (base station). Subframe 2 represents the same subframe as received by the first mobile communication device. The "C" field in the SCR indicates that the configuration data is transmitted from the network to the first mobile communication device by (broadcast or dedicated) RRC signalling.

The signaling of the physical layer (option 1, according to fig. 8) is somewhat faster, but less reliable (in terms of ciphering and error correction) than the RRC signaling. The signaling at the RRC layer (option 2, according to fig. 9) allows a wider range of configuration data and provides more flexibility to construct the payload of the present invention. Configuration option 2 is preferred for our primary scenario where the second mobile communication device is an internet of things device that needs to be woken up.

A fourth aspect of the present invention relates to the problem of paging over the air interface of PC 5.

According to this aspect of the invention, the two separate information required in the paging procedure are sent by two different entities. First, a Paging Indicator (PI) is sent from UE1 to UE2, and then a Paging Message (PM) is sent from the base station to UE 2. Although the latter (i.e., PM) is always transmitted in the SCR of the downlink subframe, PI transmission by UE1 may occur on the sidelink radio resource or downlink radio resource, as will be explained in the next section.

Fig. 10 depicts the case where the UE1 uses the sidelink resource to transmit the PI over the PC5 air interface. The secondary link resources (regarding frame timing and frequency allocation) are chosen in such a way that they are in time and frequency together with those downlink resources that UE2 normally expects the PDCCH sent from its serving base station to occur, i.e. if the PM is sent in subframe (n + x), then the PI must also arrive at UE2 in subframe (n + x). The remainder of the sidelink resource grid in subframe 1 (i.e., resources other than those used for the PI of the present invention) may or may not be left empty. Subframe 1 and subframe 2 contain PIs. Subframe 1 is transmitted by UE1 and subframe 2 represents reception of the same subframe by UE 2. The UE1 may choose to transmit this sub-link subframe on the portion of the resource grid where the UE2 would normally expect a downlink subframe (from its base station) to arrive. Subframe 3 and subframe 4 contain PM. Subframe 3 is transmitted by the base station and subframe 4 represents reception of the same subframe by the UE 2. As expected by UE2, the PM is located in the SCR.

Fig. 11 depicts a case where the UE1 transmits the PI over the PC5 air interface using downlink resources. This means that the UE1 mimics the base station functionality in this part of the operation. In one embodiment, the analog base station functionality may require the UE1 to open the second TX chain (at least) for a limited time. The downlink resources (with respect to frame timing and frequency allocation) are selected in such a way that they are in time and frequency with those downlink resources that UE2 would normally expect the PDCCH sent from its serving base station to occur, i.e. if the PM is sent in sub-frame (n + x), the PI must also arrive at UE2 in sub-frame (n + x). In subframe 1, the remainder of the downlink resource grid (except for the resources used for the PI of the present invention) may or may not be left empty.

Subframe 1 and subframe 2 contain PIs. Subframe 1 is transmitted by UE1 and subframe 2 represents reception of the same subframe by UE 2. The UE1 may choose to transmit the downlink subframe on the portion of the resource grid where the UE2 would normally expect (from its base station) the downlink subframe to arrive. Subframe 3 and subframe 4 contain PM. Subframe 3 is transmitted by the base station and subframe 4 represents reception of the same subframe by the UE 2. As expected by UE2, the PM is located in the SCR.

In fig. 10 and 11, the subframe perceived by the UE2 at time point (n + x) is a superposition of subframe 1 (transmitted by the UE1) and subframe 3 (transmitted by the base station). This composed "downlink subframe", as expected by UE2, contains both PI and PM in the CCR (e.g., PM in the SCR).

A fifth aspect of the invention relates to fine resource coordination.

Fig. 10 and 11 also show the portion of the CCR labeled "B" for subframe 3. According to one embodiment of the invention, this part of the downlink resource grid is preferably left empty (i.e. not used) by the base station serving the UE2 to avoid any resource collision between subframe 3 transmitted over the Uu air interface and subframe 1 transmitted over the PC5 air interface. Without such a gap, interference may occur on various UEs in the vicinity of the two mobile communication devices UE1 and UE2, particularly on UE 2.

For example, the "B" portion of the CCR may include one or more Resource Elements (REs) or Resource Blocks (RBs) allocated to the PDCCH of subframe 3 in which a paging indication (e.g., in the form of DCI with a Cyclic Redundancy Check (CRC) portion scrambled by one paging-RNTI) is typically sent.

A sixth aspect of the invention relates to the cross-subframe timing relationship.

A sixth aspect relates to timing relationships beyond subframe boundaries. This means that, unlike current deployments, the control channel region transmitting the PI and the shared channel region transmitting the subsequent PM no longer reside in the same subframe. Details of this are shown in figure 12. In the previous figures, it was used to represent the amount of time between the UE1 receiving the paging configuration (in subframe n) and the associated subframe (n + x) performing the paging procedure. In contrast, fig. 12 shows the length of time between receiving a subframe (n + x) and a subframe (n + y), where x < y.

In this case, the UE2 needs to know that the PI and PM are not received in the same subframe. The offset may be part of a configuration process according to the third aspect of the invention.

Preferred aspects of the present invention include:

(1) a method for a first mobile communication device to assist in a paging procedure to page a second mobile communication device;

in particular, the paging procedure comprises at least one of:

receiving a paging indication from a first mobile communication device over a device-to-device direct air interface; receiving a paging message from a base station;

also, wherein the transmission of the paging indicator is configurable by the base station, the paging indicator is sent when at least one of the following criteria is met:

location requirements (the first mobile communication device has detected proximity to the second mobile communication device);

time requirement (the first mobile communication device has detected paging opportunity/reachability to the second mobile communication device).

And other requirements, wherein the novel paging procedure further comprises at least one of:

generating a location fix message in the first mobile communication device;

comparing, by the first mobile communication device, the position fix information with configuration data received from a base station;

determining, by the first mobile communication device, a transmission time for transmitting the subframe to the second mobile communication device over the direct device-to-device air interface;

a paging indicator is included by the first mobile communication device in a subframe transmission to the second mobile communication device.

Note: the order of "location check" and "time check" is arbitrarily selected. The reverse is also possible.

Another aspect is wherein determining the transmission time further comprises at least one of:

performing, by a first mobile communication device, random access to a base station serving a second mobile communication device;

the first mobile communications device receiving the timing advance value from a base station serving the second mobile communications device;

calculating, by a first mobile communications device, a timing offset between the first and second mobile communications devices from the timing advance value received by the base station serving the second mobile communications device;

determining, by a first mobile communication device, an exact point in time of sub-frame alignment between the first and second mobile communication devices using the timing offset; and

transmitting, by the first mobile communication device, one subframe to the second mobile communication device at the exact point in time.

The invention also provides a mobile communication device with the means for realizing the paging process.

The present invention provides infrastructure equipment with means to implement the paging process.

Claims

1. A method of performing a paging action for a second User Equipment (UE), the UE and an apparatus in a mobile communication system, the method comprising:

sending a configuration message from a first base station to a first UE device to configure the first UE device to send a paging indication at a predetermined time if it is determined that a geographical condition is satisfied; and

sending a paging message from one of the first base station and a second base station to the second UE device after the paging indication is sent.

2. The method of claim 1, wherein the geographic condition is that the second UE device is located within a predetermined proximity of the first UE device.

3. The method of claim 1 or claim 2, wherein the first UE device determines whether the geographic condition is satisfied by analyzing global navigation satellite system information.

4. The method of any preceding claim, wherein the paging indication is transmitted over a sidelink (sidelink) between UE devices.

5. The method of any of claims 1-3, wherein the paging indication is transmitted by the first UE device as a base station emulator.

6. The method of any preceding claim, wherein the configuration message comprises location information and/or time information.

7. The method of claim 6, wherein the configuration information is transmitted to the first UE device via downlink control information.

8. The method of claim 6, wherein the configuration information is transmitted to the first UE device by radio resource control signaling.

9. The method of any preceding claim, wherein the first base station does not transmit in a portion of a downlink resource grid to be used by the first UE device for sending the paging indication.

10. The method of any preceding claim, wherein the second UE device is informed of the time difference between one subframe carrying the paging indication received from the first UE device and one subframe carrying the paging message received from the first or second base station.

11. The method of any preceding claim, wherein the first UE device determines its location, compares its determined location with configuration data received from the first base station, and determines a transmission time for transmitting the paging indication.

12. The method of claim 11, wherein to determine the transmission time, the first UE device performs random access for the second base station serving the second UE, receives a timing advance parameter from the second base station, calculates a timing offset between the first UE device and the second UE device, uses the timing offset to determine a point in time of subframe alignment between the first and second UE devices, and transmits a subframe containing the paging indication at the point in time.

13. The method of any preceding claim, further comprising sending, by the first UE device, the paging indication to the second UE device.

14. A user equipment, UE and apparatus are adapted to receive a paging indicator from another UE device over a first air interface and to perform a configuration action in response to the paging indicator to receive a subsequent paging message associated with the paging indicator from a base station over a second air interface.

15. A method of performing a paging action for a second User Equipment (UE), the UE and an apparatus in a mobile communication system, the method comprising:

sending a configuration message from a first base station to a first UE device to configure the first UE device to send a paging indication at a predetermined time if it is determined that a geographical condition is satisfied;

transmitting, by the first UE device, the paging indicator to the second UE device; and