WO2022128358A1

WO2022128358A1 - Method for efficient paging of mobile ues using extended drx and a randomized ptws procedure

Info

Publication number: WO2022128358A1
Application number: PCT/EP2021/082616
Authority: WO
Inventors: Mathias KURTH
Original assignee: Shenzhen GOODIX Technology Co., Ltd.
Priority date: 2020-12-16
Filing date: 2021-11-23
Publication date: 2022-06-23
Also published as: CN115836555B; CN115836555A

Abstract

The invention discloses a method for efficient paging of mobile user equipment (UEs), using extended discontinuous reception (eDRX) and a randomized paging time windows (PTWs) procedure. The objective of the present invention to specify a method that allows an efficient paging for UEs which does not go of the power consumption of the UE will be solve by a method comprising the following steps: - step 1: a mobile management entity (MME) determines at least one eNodeB of several eNodeBs located within a tracking area (TA) of a target UE, where a paging time window (PTW) for said UE is starting next, whereas the PTW is indicated by PTW start; - step 2: the MME pages the UE during the PTW of a eDRX cycle of the at least one eNodeB determined in step 1; - step 3: the MME stops the paging of the target UE if it was successful, - otherwise the MME continues with step 1 until all eNodeBs in the associated TA of the target UE have been proceeded, wherein the paging time windows within an eDRX cycle are pseudo-randomly allocated and non-synchronized between eNodeBs, whereas a randomization of the PTW start of the eDRX cycle of each of the several eNodeBs (1-5) is achieved by including an identification of the eNodeB into a calculation on the PTW procedure for the target UE.

Description

Method for efficient paging of mobile UEs using extended DRX and a randomized PTWs procedure

Field of invention

The invention relates to a method for ef ficient paging of mobile user equipment (UEs ) , using extended discontinuous reception ( eDRX ) and a randomi zed paging time windows ( PTWs ) procedure .

Background Art

According to recent market forecasts , the Internet-of-Things ( ToT ) segment is expected to grow considerably within the next few years . Many use cases like supply chain tracking require network coverage with seamless mobility support as provided by today' s cellular networks . To cope with the massive number of ToT devices expected, the 3GPP standardi zation body has introduced Machine type communication (MTC ) capabilities into the cellular network technology .

In the following, the invention is illustrated using the NarrowBand Internet-of-Things (NB- IoT ) access technology as well as the Evolved Packet Core (EPC ) . The invention is not limited to the selected technology; it can be applied to 4G E-UTRAN, eMTC and other technologies using the mechanism of extended discontinuous reception ( eDRX ) as well . The discontinuous reception ( DRX ) is a mechanism in which a device goes into sleep mode for a certain period and then wakes up after a fixed interval to receive signals . The basic principle for eDRX is to extend DRX cycles to allow a device to remain in a power-saving state for a longer period of time .

Figure 1 shows the network architecture reference model of the 4th generation ( 4G) 3GPP cellular network . The Access Stratum (AS ) consists of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and the User Equipment (UE ) . The Evolved Node B ( eNodeB ) is the network element of the E- UTRAN . Within the description of the invention the terms eNodeB, base station and radio access node are used synonymously . Narrowband- IoT is a subset of E-UTRAN .

The Evolved Packet Core (EPC ) comprises following subcomponents : a Mobility Management Entity (MME ) , a Serving Gateway ( SGW) , a Packet Data Network Gateway ( PGW) , and a Home Subscriber Server (HSS ) .

The MME is the key control-node for the LTE access-network . The MME entity veri fies subscriber authori zation, manages the location of the User Equipment (UE ) with the Tracking Area ( TA) , and stores the connection states and security parameters of the subscriber UE devices . When the tracking area is changed, the MME instance receives a tracking area update . So , it is involved in the bearer activation/deactivation process and is also responsible for choosing the Serving Gateway ( SGW) for a UE at the initial attach and at time of intra-LTE handover involving Core Network ( CN) node relocation . It is responsible for authenticating the user (by interacting with the Home Subscriber Server ) . The Non Access Stratum (NAS ) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs . It checks the authori zation of the UE to camp on the service provider ' s Public Land Mobile Network ( PLMN) and enforces UE roaming restrictions . The MME is the termination point in the network for ciphering/ integrity protection for NAS signaling and handles the security key management . The MME provides the control plane function for mobility between LTE and 2G/ 3G access networks with the S3 interface terminating at the MME from the SGSN ( Serving GPRS ( general packet radio service ) support node ) . The MME also terminates the S 6a interface towards the HSS for roaming UEs .

The SGW routes and forwards user data packets , while also acting as the mobility anchor for the user plane during inter-eNodeB handovers and as the anchor for mobility between LTE and other 3GPP technologies ( terminating S4 interface and relaying the traf fic between 2G/ 3G systems and Packet Data Network Gateway) . For idle state User Equipment , the SGW terminates the downlink data path and triggers paging when downlink data arrives for the UE . It manages and stores UE contexts , e . g . parameters of the IP bearer service , network internal routing information .

The Packet Data Network Gateway ( PDN Gateway, also PGW) provides connectivity from the UE to external packet data networks ( PDNs ) by being its point of exit and entry of traf fic . A piece of UE may have simultaneous connectivity with more than one Packet Data Network Gateway for accessing multiple packet data networks . The PGW performs policy enforcement , packet filtering for each user, charging support , lawful interception and packet screening . Another key role of the PGW is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2.

The HSS is a central database that contains user-related and subscription-related information. The functions of the HSS include functionalities such as mobility management, call and session establishment support, user authentication and access authorization. The HSS is based on pre-Rel-4 Home Location Register (HLR) and Authentication Center (AuC) .

In figure 1, the transitions between the single architecture components indicate interfaces that acting upon specific protocols .

For synchronization purposes between an eNodeB and a UE, the time on the AS is partitioned into frames. The frame structure of NB-IoT is shown in figure 2. A sub-frame consists of two slots of 500ps each. A system frame of 10ms contains 10 sub-frames. A hyper system frame has 1024 system frames (10.24s) . A hyper system frame cycle consists of 1024 hyper system frames covering about 3 hours.

The cellular network supports mobile UEs in both active and idle state. When the UE is in idle state, the network tracks the location of the UE on a level of tracking area (TA) . A tracking area 6 consists of a set of eNodeBs 1-5 connected to the same MME as shown in figure 3. The TA 6 in figure 3 includes a first radio access node 1, and four neighboring radio access nodes 2, 3, 4, 5 and wherein each radio access node is an eNodeB, eNB, in the LTE network. Each eNodeB, eNBl-eNB5, is responsible for radio-related functions in adjacent cells, wherein cells served by the same eNodeB are illustrated by identical filling patterns in the schematic view. In the schematic view, each eNodeB is visualized as a physical entity with a single antenna. However, an eNodeB is a logical node that may be implemented through one or more physical radio base stations.

During initial attach or on entering a new TA 6, the UE registers within the TA 6 (or within multiple TAs) . The EPC knows the location of the UE at TA level. The UE can freely roam between eNodeBs 1-5 within the registered TA(s) 6 without the need to inform the EPC.

The procedure of locating the position of the UE at eNodeB- level is called paging. When data arrives at the EPC for the UE, paging is used to locate the UE and establish a signaling connection for downlink data delivery. The procedure for mobile terminated (MT) data transport in NB- ToT is shown in figure 4. The PGW delivers the data to SGW, where it remains until the UE has established a signaling connection. The SGW informs the MME about the downlink data, and the MME initiates the paging procedure, which is described in the following. The MME sends a paging request to eNodeB (s) according to a proprietary paging strategy. On the radio access network (RAN) level, the UE periodically listens for broadcast paging messages using a network- defined paging cycle. The eNodeB sends out a broadcast paging message within a predefined time slot determined by the paging occasion (PO) sub-frame, paging frame (PF) , and paging hyper-frame (PH) . A UE wakes up in a specific subframe either subframe 0, 4, 5 or 9 within a radio frame. These specific subframes within a Paging Frame when UE wakes up are called as Paging Occasions (POs) . The RAN paging message is a broadcast: it is received by multiple UEs. The paging message contains the identities of the UEs that are paged. If the paging message was successfully received by the paged UE, it initiates a signaling connection to the MME. The SGW is informed and the downlink data is delivered to the UE via the MME encapsulated within Non Access Stratum (NAS) Data Protocol Data Units (PDUs) . The paging has failed when no signaling connection was established. Depending on paging strategy and network configuration, the MME might start a further paging attempt, or it might declare the UE unreachable .

The paging strategy determines in which order the MME involves the eNodeBs of the TA(s) into the paging procedure. Well-known paging strategies are:

1. Blanket paging: The MME pages the UE at all eNodeBs of the registered TA(s) . Blanket paging is a simple strategy with low paging latency but high paging resource consumption and high signaling load.

2. Sequential paging: The TA is partitioned into paging zones. The MME pages all eNodeBs within a paging zone in parallel. If the paging attempt fails, the MME escalates the paging to other paging zones. The paging zones are generally constructed according to the expected probability of presence of the paged UE .

3. Shortest-distance-first: Paging zones can be constructed according to the distance to the eNodeB where the last location update of the UE has happened.

The paging strategy determines the tradeoff between paging load and paging delay. Furthermore, the size of the TA is a critical network planning parameter determining the tradeoff between location update costs versus paging costs.

The setup of a voice call should not take more than some seconds to meet customer experiences. Thus, the voice- enabled UE must be reachable on a second basis. For loT devices, on the other hand, energy consumption might be more important than reachability. 3GPP has introduced a high latency communication in combination with Power Saving Mode (PSM) and Extended Idle mode Discontinuous Reception (eDRX) . An extended DRX cycle is shown in figure 5. As illustrated in figure 5, the UE is in a connected state during a period from time tO to time tl. The MME may configure the eDRX to the UE within this period. During the period from time tl to time t2, the UE is in the sleep state of the eDRX cycle. So, the period from time tl to time t5 corresponds to the eDRX cycle, which consists of the eDRX inactivity (sleep state) , and the PTW. At time t2, the UE exits (wakes up) the sleep state of the eDRX cycle. The period from time t2 to time t5 corresponds to the paging time window (PTW) . Based on the paging message from the MME, the eNodeB repeatedly transmits the paging at the paging reception opportunity (PF and PO) within the paging time window. At time t3 and time t4, the paging reception opportunity (PF and PO) of the UE occurs. The paging reception opportunity is also called paging occasion, which is a sub-frame where the UE monitors its paging indicator. The eNodeB repeatedly transmits the paging to the UE at time t3 and time t4. At time t5, the UE transitions from the wake-up state of the eDRX cycle to the sleep state.

Extended Idle mode DRX (eDRX) allows interrupting the idle mode DRX operation to save power. The interruption time is called eDRX inactivity. The remaining time within the eDRX cycle is called Paging Time Window (PTW) . So, the eDRX inactivity period and the paging time window forms the eDRX cycle. Both network and UE negotiate the eDRX cycle and the PTW within the attach and tracking area update (TAU) procedure. The location of the PTW within the eDRX cycle in terms of paging hyper-frame (PH) and paging frame (PF) is pseudo-random and depends on the identity of the UE . For load balancing purposes, the PTWs of different UEs are uniformly distributed across the eDRX cycle.

The Paging Time Window procedure will be described next. The Paging Time Window is determined as follows (see also 3GPP TS 36.304 Release 13 (and newer) ) , :

The paging Hyper- (H) System frame number (SFN) is determined as: H-SFN mod T_eDRx,H = (UE_ID_H mod T_eDRx,n) , whereas T_eDRx,H is the eDRX cycle in number of hyperframes and UE_ID_H are the 12 most significant bits of a hashed ID (defined below) ;

The paging frame system-frame-number (SFN) is determined as: SFN = 256*i_eDRx, with i_eDRx = floor (UE_ID_H /T_eDRx,H) mod 4;

The hashed ID is determined by hashed ID = ~ ( crc32 ( OxFFFF FFFF) ^A crc32 (M-TMS I ) ) , with is the ones complement, '^A' is exclusive OR, 'crc32' is the 32-bit cyclic redundancy check using the ITU generator polynomial and 'M-TMSI' is the MME Temporary Mobile Subscriber Identity (32-bit) .

The floor expression means to round down. The 32-bit cyclic redundancy check uses the generator polynomial 0xl04CllDB7 as defined by the ITU-T V.42.

The UE is reachable for mobile terminated (MT) data and signaling during the PTW only. The implications on the MT Data transport use case (see figure 4) are as follows. The

MME needs to be aware whether and when the target UE is reachable next. This is achieved by loose hyper-SFN synchronization between MME and eNodeB, described in the following. For MT data, the MME informs the SGW about the expected time it needs to buffer the data before the UE becomes reachable again. Furthermore, the MME needs to time- align the paging requests towards the eNodeB (s) according to the PTW of the UE .

3GPP supports the monitoring of the UE reachability. When the UE is not reachable due to eDRX inactivity, EPC internal as well as connected user applications can request to be informed when the UE becomes reachable again. The UE reachability can be used to migrate the buffering of MT data from the SGW to the application.

When using eDRX within a TA, the MME needs to know the PTW start and end of the UE to be paged. The PTW is determined by the frame timing of the AS, the eDRX configuration as well as NAS-level identities of the UE . For that purpose, 3GPP mandates a so-called loose Hyper-SFN Synchronization (3GPP TS 23.682 Release 13 (and newer) ) between MME and eNodeB within a TA.

Loose Hyper-SFN Synchronization requires that the time difference between MME and each eNodeB within the TA is not more than l-2s as shown in figure 6 (with reference to US 20180263012 Al) . In other words, the eNodeBs in the tracking area have a coarse time-synchronization. The synchronization mechanism shown in figure 6 requires a performance improvement of the MME and the eNodeB which also increases system complexity. The reason why synchronization having accuracy within 1-2 seconds within an MME and an eNodeB is performed is to minimize or obviate the time taken for the eNodeB to store a paging message.

The impact of loose hyper-SFN synchronization on the paging strategy of the MME is as follows. As shown in figure 7, the PTWs for the target UE are overlapping for all eNodeBs within the TA. The allowed variation is l-2s whereas the minimum paging cycle in NB-IoT is 1.28s. During the negotiation of the eDRX parameters with the UE, the MME needs to dimension the PTW length according to paging strategy. If the PTW is short, the first paging attempts fail because of UE mobility, and the MME has paged the wrong eNodeBs, the UE might enter eDRX inactivity again and might not be reachable for a long time. The MME has then the following options:

1. The MME might prolong the PTW to accommodate additional paging attempts at the expense of the UE power consumption .

2. The MME might escalate paging earlier: By involving eNodeBs earlier, the paging load on the AS increases.

3. The MME continues the paging in the next eDRX cycle leading to higher paging latency as well as longer data buffering at the SGW.

The 3GPP specification favors option 1 [see also R2-161311, TS 23.682 Release 13 (and newer) ] to address the issue.

Figure 8 illustrates the resulting time line of the paging procedure. In the shown example, the MME is using sequential paging with two paging zones and two paging occasions per paging zone. The MME pages the UE at eNodeB 1 first, where the UE was registered last. The MME allows for two paging occasions or attempts per paging zone . After two unsuccess ful paging attempts at eNodeB 1 , the MME escalates the paging to the second paging zone involving eNodeB 2 and 3 . As the MME has selected two paging zones with two attempts each, the whole PTW for the UE needs to include four paging occasions .

So , the problem which should be addressed by the present invention is that with the state-of-the-art overlapping paging time windows for a target UE at all eNodeBs in a tracking area of the target UE limits the flexibility of the Mobile Management Entity paging strategy and goes at the expense of UE power consumption as the UE has to be in active mode for example for additional paging attempts .

It is an obj ective of the present invention to speci fy a method that allows an ef ficient paging for mobile user equipment (UEs ) which does not go of the power consumption of the UE .

Summary of the invention

The obj ective of the present invention is solved by a method for ef ficient paging of mobile UEs , using extended discontinuous reception ( eDRX ) and a randomi zed paging time windows ( PTWs ) procedure , the method comprising the following steps :

- step 1 : a mobile management entity (MME ) determines at least one eNodeB of several eNodeBs located within a tracking area ( TA) of a target UE , where a paging time window ( PTW) for said UE is starting next , whereas the PTW is indicated by PTW start ; - step 2 : the MME pages the UE during the paging time window of a eDRX cycle of the at least one eNodeB determined in step 1 ;

- step 3 : the MME stops the paging of the target UE i f it was success ful ,

- otherwise the MME continues with step 1 until all eNodeBs in the associated TA of the target UE have been proceeded, wherein the paging time windows within the eDRX cycle are pseudo-randomly allocated and non-synchroni zed between eNodeBs , whereas a randomi zation of the PTW start of the eDRX cycle of each of the several eNodeBs ( 1-5 ) is achieved by including an identi fication of the eNodeB into a calculation on the PTW procedure for the target UE . For the identi fication of the eNodeB a cell ID of said eNodeB is used .

The PTW are pseudo-randomly allocated with respect to UE as well as eNodeB and fully non-overlapping across all eNodeBs . The rationale of the randomi zed PTW feature in the PTW procedure is that the time location of the PTW within the eDRX cycle changes when the UE changes from one eNodeB to another, i . e . PTWs are not synchroni zed anymore . With PTWs not synchroni zed anymore , also the dependency of the PTW length on the paging strategy is reduced . The MME does not need to provision for UE mobility when determining the PTW length . The shorter PTW length reduces the power consumption on the UE side . The paging load on the AS is not increased, i . e . the expected number of paging messages on the radio access network level does not increase . The paging latency becomes random and uni formly distributed across the eDRX cycle . On both UE and network side , no additional state needs to be maintained since the pseudo-random allocation of PTWs is stateless. Stateless means that there is no memory required on neither network nor UE side to store any configuration or state to realize the above-mentioned PTW allocation .

The randomization of the PTW start of the eDRX cycle is achieved by including an identification of the eNodeB into the calculation on the PTW procedure for the considered/ target UE .

In a variant of the inventive method, for the identification of the eNodeB in the calculation on the PTW for the target UE an E-UTRAN Cell Identifier (ECI) , is used, whereas a hashed ID of a Hyper-System- Frame-Number (H-SFN) , where the PTW starts, is calculated by hashed ID = ~ ( crc32 ( OxFFFF FFFF) ^A crc32 (M-TMSI ^A ECI) ) ) .

Using the E-UTRAN Cell Identifier (ECI) , the hashed ID can be calculated as follows; hashed ID = ~ ( crc32 ( OxFFFF FFFF) ^A crc32 (M-TMSI ^A ECI) ) , with is the ones complement, '^A' is exclusive OR, 'crc32' is the 32 bit cyclic redundancy check using the ITU generator polynomial and 'M-TMSI' is the MME Temporary Mobile Subscriber Identity (32 bit) . With the shown formula, the hashed ID becomes pseudo-random with respect to both M-TMSI and ECI. It remains uniformly distributed within the value range of 32 bit. Using the described randomization method/procedure is only one possibility and is used as an illustration. Other possibilities or modifications that presents a randomization of the PTW start are also conceivable. The hashed ID is determined by the UE and / or by the MME . It is mandatory that the hashed ID is calculated by UE and MME , otherwise the eDRX paging procedure will fail .

Both UE and MME can determine the hashed ID, and thus , the PTW without storing any additional state .

In general , for the identi fication of an eNodeB in the calculation on the PTW procedure , the cell ID of the associated eNodeB is used . The presented idea of the invention can be adapted to recent cellular technologies . A person skilled in the art will know that he can use this idea for recent cellular technologies by adapting the terminology and calculation rules to the new standards . As an example , for the 5G technology, one would use the NR cell ID .

According to another variant of the inventive method, during a reselection of the UE from one eNodeB to another, the UE is reading a System- Information-Blockl that contains the ECI , for determining the PTW start within a new eNodeB . The hashed ID changes when the UE reselects to another eNodeB . The information that is required to calculate the new hashed ID is already available on the UE side .

Using this information, the UE can determine the start of the PTW within the new eNodeB without any additional overhead . The information about connected eNodeBs is generally available on the MME side , so that also for the MME the proposed procedure has low overhead .

In a variant of the inventive method, for low mobile and nomadic UEs , the MME at first determines the PTW of the UE at an eNodeB of the TA of the UE where the UE was registered last , the MME pages the UE at said eNodeB at a time the PTW starts and the MME stops the paging of the UE i f it was success ful , otherwise the MME continues with step 1 .

So , for low mobile and nomadic UEs , the MME might make use of information at which eNodeB the UE was registered last : Firstly, the MME determines the PTW of the UE at eNodeB where the UE was registered last , then it pages the UE at the eNodeB determined in step 1 at the time of the PTW start , and then stop paging on success . On paging failure , default to blanket paging is performed as described above .

According to a further variant of the inventive method, the randomi zed paging time windows ( PTWs ) procedure is requested by the UE in an attach request message or in a tracking area update request message exchanged between the UE and a network, wherein the network signals an activation of the randomi zed PTWs procedure within a respective attach accept message or a tracking area update accept message .

This variant enables to remain backward compatible or manages applications where the randomi zed paging latency imposes issues . The PTW randomi zation shall be an optional feature that the UE needs to request in the respective ATTACH REQUEST or TRACKING AREA UPDATE REQUEST messages . I f the UE requests the feature PTW randomi zation and the network supports it , the network shall signal the activation within the respective ATTACH ACCEPT or TRACKING AREA UPDATE ACCEPT messages .

Pursuant to another further variant of the inventive method, the method is applicable to all cellular technologies with extended idle mode DRX support , like E-UTRAN LTE , EMTC CAT- M, 5G technologies NR and 5G core .

The invention has been presented using NB- IoT and EPC technology as one example application . It can be applied to all cellular technologies with extended idle mode DRX support like E-UTRAN LTE and eMTC CAT-M as well as 5G technologies NR and 5G core .

According to another aspect of the present application, a device for ef ficient paging of mobile user equipment using extended discontinuous reception ( eDRX ) and a randomi zed paging time windows ( PTWs ) procedure is provided, comprising : a determining module configured to determine at least one eNodeB of several eNodeBs located within a tracking area ( TA) of a target UE , where a paging time window ( PTW) for said UE is starting next ; a paging module configured to page the UE during the paging time window of a eDRX cycle of the at least one eNodeB determined by the determining module , stop the paging i f it was success ful , and otherwise continue to page the UE during a paging time window of a eDRX cycle of another at least one eNodeB determined by the determining module until all eNodeBs in the associated TA of the target UE have been proceeded, wherein the paging time windows within a eDRX cycle are pseudo-randomly allocated and non-synchroni zed between eNodeBs .

The device could be a MME or other entity . It should be noted that , other details of the device may refer to the related description of the above method. For brevity, details are not described herein again.

Brief description of drawings

The invention will be explained in more detail using exemplary embodiments.

The appended drawings show

Fig. 1 Non-roaming architecture for 3 GPP accesses (see 3GPP TS 23.401, V16.8.0, Fig. 4.2.1-1) ;

Fig. 2 NB-IoT frame structure (15kHz) ;

Fig. 3 Example for a tracking area architecture (out of

US 9560628 B2) ;

Fig. 4 Mobile terminated data transport in non-access stratum Protocol Data Units (see 3GPP TS 23.401, V16.8.0, Fig. 5.3.4B.3-1) ;

Fig. 5 Extended DRX cycle (out of US 20180176883 Al) ;

Fig. 6 Loose Hyper-System-frame number Synchronization (out of US 20180263012 Al) ;

Fig. 7 Example of overlapping paging time windows in a tracking area (prior art) ;

Fig. 8 Example of paging a UE with overlapping paging time windows (prior art) ;

Fig. 9 Inventive Paging of a UE with fully nonoverlapping and non-synchronized paging time windows ; Fig. 10 Non-overlapping paging time windows in a tracking area according to the invention.

Description of Embodiments

When applying the inventive efficient paging method for UEs using extended discontinuous reception (eDRX) and a randomized paging time windows procedure, the above- mentioned use case presented in figure 8 changes as follows. The MME 7 in figure 9 again selects two attempts, also called paging occasions 8, per paging time window 11. In contrast to figure 8, the PTW 11 is shorter. The MME 7 does not need to provision for the escalation of the paging to additional paging occasions 8 within the PTW 11. The PTW length is reduced from 4 to 2 POs .

Based on the identity of the eNodeB, the start of the PTW 11 assigned to the UE is pseudo-random within the eDRX cycle 12 as shown in figure 10. For example, the UE associated with eNodeB 1 in figure 10 is assigned a PTW 11 at the start of the eDRX cycle 12. When reselecting UE to eNodeB 2, the PTW 11 changes from the start to the middle of the eDRX cycle 12. Similarly, the PTW 11 changes again when reselecting UE to the shown eNodeB 3.

For high mobile UEs, the MME 7 might use the blanket paging strategy the following way:

Firstly, the MME 7 determines eNodeB (s) where the PTW 11 is starting next for the target UE . Then the MME 7 pages the UE at this eNodeB determined first. The MME 7 stops the paging on success. On paging failure, the MME 7 continues with the first step until all eNodeB (s) in the associated TA(s) have been processed. For low mobile and nomadic UEs , the MME 7 might make use of information at which a UE was registered last :

Firstly, the MME 7 determines the PTW 11 of the UE at eNodeB where the UE was registered last . The MME 7 pages the UE at the eNodeB determined first at the time of the PTW start .

The MME 7 stops paging on success . On paging failure , the MME 7 returns per default to blanket paging described for high mobile UEs mentioned above .

List of Reference Signs

1 First eNodeB, first radio access node

2 A second eNodeB

3 A third eNodeB

4 A fourth eNodeB 5 A fi fth eNodeB

6 Tracking area

7 Mobility Management Entity

8 Paging occasion

9 UE is paged 10 UE is not paged

11 Paging time window

12 Extended discontinuous reception cycle

Claims

Method for efficient paging of mobile UEs using extended DRX and a randomized PTWs procedure Claims

1. A method for efficient paging of mobile user equipment, UEs, using extended discontinuous reception, eDRX, and a randomized paging time windows, PTWs, procedure, the method comprising the following steps:

- step 1: a mobile management entity (7) , MME, determines at least one eNodeB (1) of several eNodeBs (1-5) located within a tracking area (6) , TA, of a target UE, where a paging time window (11) , PTW, for said UE is starting next;

- step 2: the MME (7) pages the UE during the paging time window (11) of a eDRX cycle of the at least one eNodeB determined in step 1;

- step 3: the MME (7) stops the paging if it was successful,

- otherwise the MME (7) continues with step 1 until all eNodeBs (1-5) in the associated TA (6) of the target UE have been proceeded, wherein the paging time windows (11) within a eDRX cycle are pseudo-randomly allocated and nonsynchronized between eNodeBs (1-5) .

2. The method according to claim 1, whereas a randomization of the PTW start of the eDRX cycle of each of the several eNodeBs (1-5) is achieved by including an identification of the eNodeB into a calculation on the PTW procedure for the target UE . The method according to claim 2, wherein for the identification of the eNodeB in the calculation on the PTW procedure for the target UE an E-UTRAN Cell Identifier, ECI, is used, wherein a hashed ID of a Hyper-Frame, H-SFN, where the PTW starts, is calculated by hashed ID = ~ ( crc32 ( OxFFFF FFFF) ^A crc32 (M-TMSI ^A ECI) ) . The method according to claim 3, wherein the hashed ID is determined by the UE and / or by the MME (7) . The method according to claim 3, wherein during a reselection of the UE from one eNodeB to another, the UE is reading a System-Information-Blockl that contains the ECI, for determining the PTW start within a new eNodeB . The method according to claim 1, wherein for low mobile and nomadic UEs, the MME (7) at first determines the PTW (11) of the UE at an eNodeB of the TA (6) of the UE where the UE was registered last, pages the UE at said eNodeB the PTW starts, and stops the paging if it was successful, otherwise the MME (7) continues with step

1. The method according to one of the claims 1 to 6, wherein the randomized paging time windows, PTWs, procedure is requested by the UE in an attach request message or in a tracking area update request message exchanged between the UE and a network, wherein the network signals an activation of the randomized PTWs procedure within a respective attach accept message or a tracking area update accept message. The method according to one of the claims 1 to 7, wherein the method is applicable to all cellular technologies with extended idle mode DRX support, such as E-UTRAN LTE, EMTC CAT-M, 5G technologies NR and 5G core . A device for efficient paging of mobile user equipment, UEs, using extended discontinuous reception, eDRX, and a randomized paging time windows, PTWs, procedure, wherein the device comprising: a determining module configured to determine at least one eNodeB (1) of several eNodeBs (1-5) located within a tracking area (6) , TA, of a target UE, where a paging time window (11) , PTW, for said UE is starting next; a paging module configured to page the UE during the paging time window (11) of a eDRX cycle of the at least one eNodeB determined by the determining module, stop the paging if it was successful, and otherwise continue to page the UE during a paging time window (11) of a eDRX cycle of another at least one eNodeB determined by the determining module until all eNodeBs (1-5) in the associated TA (6) of the target UE have been proceeded, wherein the paging time windows (11) within a eDRX cycle are pseudo-randomly allocated and nonsynchronized between eNodeBs (1-5) .