# Patent

## Title
Signaling of core network restart to wireless devices

## Abstract

A radio access network node and methods are described herein for signaling an indication of a network restart to wireless devices within a cellular network. In one embodiment, the radio access network node is operable to: (1) signal, to the wireless devices, an indication that a network restart has occurred in a core network node in a pool of core network nodes in the cellular network; and (2) receive, from at least one of the wireless devices, a re-registration message in response to the signaling of the indication that the network restart has occurred. The wireless device and methods implemented by the same are also described herein.

## Background
CLAIM OF PRIORITY
This application claims the benefit of priority to U.S. Provisional Application Ser. No. 62/128,867, filed on Mar. 5, 2015, the entire contents of which are hereby incorporated herein by reference for all purposes.


TECHNICAL FIELD
The present disclosure relates generally to the wireless communications field and, more particularly, to a radio access network node and method for signaling to wireless devices that a network restart has occurred in a core network node which is associated with a pool of core network nodes. In addition, the present disclosure relates to a wireless device and method for receiving the signaling of a network restart from the radio access network node.
BACKGROUND
The following abbreviations and terms are herewith defined, at least some of which are referred to within the following description of the present disclosure.

    3GPP 3rd-Generation Partnership Project
    AGCH Access Grant Channel
    ASIC Application Specific Integrated Circuit
    BCCH Broadcast Control Channel
    BLER Block Error Rate
    BSS Base Station Subsystem
    BTS Base Transceiver Station
    CC Coverage Class
    CCCH Common Control Channel
    CN Core Network
    CRC Cyclic Redundancy Check
    DRX Discontinuous Receive Cycle
    EC-GSM Extended Coverage Global System for Mobile Communications
    EC-PCH Extended Coverage Paging Channel
    EC-SCH Extended Coverage Synchronization Channel
    eDRX Extended Discontinuous Receive Cycle
    eNB Evolved Node B
    DSP Digital Signal Processor
    EDGE Enhanced Data rates for GSM Evolution
    EGPRS Enhanced General Packet Radio Service
    FCCH Frequency Correction Channel
    GSM Global System for Mobile Communications
    GERAN GSM/EDGE Radio Access Network
    GMSK Gaussian Minimum Phase Shift Keying
    GP GERAN Plenary
    GPC GERAN Plenary Cellular
    GPRS General Packet Radio Service
    HARQ Hybrid Automatic Repeat Request
    HLR Home Location Register
    IE Information Element
    IMSI International Mobile Subscriber Identity
    IoT Internet of Things
    LTE Long-Term Evolution
    M2M Machine-to-Machine
    MBMS Multimedia Broadcast/Multicast Service
    MME Mobility Management Entity
    MS Mobile Station
    MTC Machine Type Communications
    NAS Non-Access Stratum
    NB Node B
    NRI Network Resource Identifier
    PCH Paging Channel
    PDP Packet Data Protocol
    PDN Packet Data Network
    PDTCH Packet Data Traffic Channel
    PSM Power Saving Mode
    P-TMSI Packet Temporary Mobile Subscriber Identity
    RA Routing Area
    RACH Random Access Channel
    RAN Radio Access Network
    RAU Routing Area Update
    RNC Radio Network Controller
    SCH Synchronization Channel
    SGSN Serving GPRS Support Node
    SI System Information
    TAU Tracking Area Update
    TDMA Time Division Multiple Access
    TS Timeslot
    TSC Timing Sequence Code
    TSG Technical Specifications Group
    UE User Equipment
    VLR Visitor Location Register
    WCDMA Wideband Code Division Multiple Access
    WiMAX Worldwide Interoperability for Microwave Access
    Coverage Class (CC): At any point in time a wireless device belongs to a specific uplink/downlink coverage class that corresponds to either the legacy radio interface performance attributes that serve as the reference coverage for legacy cell planning (e.g., a Block Error Rate of 10% after a single radio block transmission on the PDTCH) or a range of radio interface performance attributes degraded compared to the reference coverage (e.g., up to 20 dB lower performance than that of the reference coverage). Coverage class determines the total number of blind transmissions to be used when transmitting/receiving radio blocks. An uplink/downlink coverage class applicable at any point in time can differ between different logical channels. Upon initiating a system access a wireless device determines the uplink/downlink coverage class applicable to the RACH/AGCH based on estimating the number of blind transmissions of a radio block needed by the BSS (radio access network node) receiver/wireless device receiver to experience a BLER (block error rate) of approximately 10%. The BSS determines the uplink/downlink coverage class to be used by a wireless device on the assigned packet channel resources based on estimating the number of blind transmissions of a radio block needed to satisfy a target BLER and considering the number of HARQ retransmissions (of a radio block) that will, on average, be needed for successful reception of a radio block using that target BLER. Note: a wireless device operating with radio interface performance attributes corresponding to the reference coverage (normal coverage) is considered to be in the best coverage class (i.e., coverage class 1) and therefore does not make blind transmissions. In this case, the wireless device may be referred to as a normal coverage wireless device. In contrast, a wireless device operating with radio interface performance attributes corresponding to an extended coverage (i.e., coverage class greater than 1) makes blind transmissions. In this case, the wireless device may be referred to as an extended coverage wireless device.
    eDRX cycle: eDiscontinuous reception (eDRX) is a process of a wireless device disabling its ability to receive when it does not expect to receive incoming messages and enabling its ability to receive during a period of reachability when it anticipates the possibility of message reception. For eDRX to operate, the network coordinates with the wireless device regarding when instances of reachability are to occur. The wireless device will therefore wake up and enable message reception only during pre-scheduled periods of reachability. This process reduces the power consumption which extends the battery life of the wireless device and is sometimes called (deep) sleep mode.
    Nominal Paging Group: The specific set of EC-PCH blocks a device monitors once per eDRX cycle. The device determines this specific set of EC-PCH blocks using an algorithm that takes into account its IMSI, its eDRX cycle length and its downlink coverage class.


Today it is common to use Serving General Packet Radio Service (GPRS) Support Nodes (SGSNs) in a pool. The benefit of pooling multiple SGSNs is that the service area is larger than the service area of one SGSN. The larger service area results in reduced inter-SGSN RA updates, and it reduces the Home Location Register (HLR) update traffic. Currently, when one of the SGSNs in a pool recovers from an error (e.g., a power failure where an SGSN restarts and therefore loses with respect to the registered wireless devices all knowledge of Packet Temporary Mobile Subscriber Identity (P-TMSI) to International Mobile Subscriber Identity (IMSI) associations), the SGSN may initiate individual paging for each of the currently registered wireless devices using the wireless device's IMSI. For example, the SGSN can request the IMSIs from the HLR and the Visitor Location Register (VLR) to understand which wireless devices are currently registered in the network. Then, with the knowledge of the IMSIs and the cell level Discontinuous Receive (DRX) cycle that is common to all of the wireless devices in the same cell, the SGSN can transmit paging indications to request the wireless devices (e.g., mobile stations (MSs)) to re-register to the network.
Upon reception of paging indications for GPRS services which use the wireless device's IMSI (instead of the wireless device's assigned P-TMSI), the wireless devices will locally deactivate any active packed data protocol (PDP) context(s) and Multimedia Broadcast/Multicast Service (MBMS) context(s), and locally detach from the GPRS. After performing the local detach, the wireless devices perform a GPRS attach or perform a GPRS attach procedure as well as activate PDP context(s) to replace any previously active PDP context(s). This will re-establish a Non-Access-Stratum (NAS) connection between the wireless devices and the core network (SGSNs), and thereby, the wireless devices will receive new P-TMSI assignments. Though this mechanism will work to notify all wireless devices served by a given core network node (SGSN) that the wireless devices need to perform a RAU procedure, it is undesirable because this mechanism will take a significant period of time in order to complete the notification process, during which there may be a substantial reduction in paging capacity due to the transmission of IMSI-based pages (i.e., a P-TMSI-based page requires 32 bits, whereas an IMSI-based page requires 64 bits). As discussed next, this IMSI-based paging mechanism is also a problem when wireless devices implement the new Extended DRX (eDRX) feature.
Extended DRX (eDRX) is a new feature under development that extends the paging cycles up to the hour range while the legacy paging cycle range is in the order of 1-10 seconds (see 3GPP TSG-GERAN Meeting #64 Tdoc GP-140910, entitled “MS Energy Consumption Evaluation, PSM vs. eDRX”—the contents of this document are hereby incorporated herein by reference for all purposes). In the legacy DRX operation, a DRX cycle, defined as the time between instances where the wireless device wakes up to monitor its Paging Channel (PCH), occurs on the order of once every few seconds and the same DRX cycle applies to all wireless devices in the same cell (i.e., the legacy DRX cycle lengths are cell specific). However, when the DRX cycle is extended, the eDRX cycle will be set per wireless device connection, and not per cell. Hence, an eDRX cycle will be determined for a specific wireless device suitable for the wireless device's service, e.g., a wireless device that needs to be contacted every 30 min to see that the wireless device is still operable.
However, when the core network (SGSN) requires a restart such as after a power failure, all information on the wireless device-specific eDRX cycles will be lost, and hence, the wireless devices will wake up according to their last registered eDRX cycle and monitor the PCH. In this case, the core network (SGSN) will no longer know when each wireless device wakes up, and therefore, all wireless devices will effectively become unreachable until the next registration event (e.g., until the next periodic registration event which may occur only once every 24 hours). Accordingly, there is a need to address these problems and other problems associated with a network restart in a pool of core network (CN) nodes.
SUMMARY
A radio access network node (e.g., BSS, eNodeB), a wireless device (e.g., MS) and various methods for addressing at least the aforementioned problems are described in the independent claims. Advantageous embodiments of the radio access network node (e.g., BSS, eNodeB), the wireless device (e.g., MS) and the various methods are further described in the dependent claims.
In one aspect, the present disclosure provides a RAN node configured to interact with a plurality of wireless devices. The RAN node comprises a processor and a memory that stores processor-executable instructions, wherein the processor interfaces with the memory to execute the processor-executable instructions, whereby the RAN node is operable to perform a signal operation, and a receive operation. In the signaling operation, the RAN node is operable to signal to the wireless devices an indication that a network restart has occurred in a CN node in a pool of CN nodes. In the receive operation, the RAN node is operable to receive from at least one of the wireless devices a re-registration message in response to the signaling of the indication that the network restart has occurred. An advantage of the RAN node implementing these operations is that this entails a faster and much more paging bandwidth-efficient technique for indicating a network restart event to multiple wireless devices when compared to the existing RAN node that individually informs each wireless device of a network restart event using IMSI-based paging.
In another aspect, the present disclosure provides a method in a RAN node configured to interact with a plurality of wireless devices. The method comprises a signaling step, and a receiving step. In the signaling step, the RAN node signals to the wireless devices an indication that a network restart has occurred in a CN node in a pool of CN nodes. In the receiving step, the RAN node receives from at least one of the wireless devices a re-registration message in response to the signaling of the indication that the network restart has occurred. An advantage of the RAN node implementing these steps is that this entails a faster and much more paging bandwidth-efficient technique for indicating a network restart event to multiple wireless devices when compared to the existing RAN node that individually informs each wireless device of a network restart event using IMSI-based paging.
In yet another aspect, the present disclosure provides a wireless device configured to interact with a RAN node. The wireless device comprises a processor and a memory that stores processor-executable instructions, wherein the processor interfaces with the memory to execute the processor-executable instructions, whereby the wireless device is operable to perform a receive operation, and a transmit operation. In the receive operation, the wireless device is operable to receive from the radio access network node an indication that a network restart has occurred in a core network node in a pool of core network nodes. In the transmit operation, the wireless device is operable to transmit to the radio access network node a re-registration message in response to the receipt of the indication that the network restart has occurred. An advantage of the wireless device implementing these operations is that this entails a faster and much more paging bandwidth-efficient technique for learning that a network restart event has occurred when compared to the existing mechanism where the wireless device would learn of a network restart event by IMSI-based paging.
In still yet another aspect, the present disclosure provides a method in a wireless device configured to interact with a RAN node. The method comprises a receiving step, and a transmitting step. In the receiving step, the wireless device receives from the radio access network node an indication that a network restart has occurred in a core network node in a pool of core network nodes. In the transmitting step, the wireless device transmits to the radio access network node a re-registration message in response to the receipt of the indication that the network restart has occurred. An advantage of the wireless device implementing these steps is that this entails a faster and much more paging bandwidth-efficient technique for learning that a network restart event has occurred when compared to the existing mechanism where the wireless device would learn of a network restart event by IMSI-based paging.
Additional aspects of the present disclosure will be set forth, in part, in the detailed description, figures and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.



BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present disclosure may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings:
FIG. 1 is a diagram of an exemplary wireless communication network which includes multiple CN nodes, multiple RAN nodes, and multiple wireless devices which are configured in accordance with an embodiment of the present disclosure;
FIG. 2 is an illustration of a super channel technique where the RAN node uses a modulation angle to achieve a low bit rate channel (supplemental information channel) on top of existing channels in order to signal that a network restart has occurred and possibly other related information to wireless devices in accordance with an embodiment of the present disclosure;
FIG. 3 is a flowchart of a method implemented in the RAN node in accordance with an embodiment of the present disclosure;
FIG. 4 is a block diagram illustrating an exemplary structure of the RAN node configured in accordance with an embodiment of the present disclosure;
FIG. 5 is a flowchart of a method implemented in the wireless device in accordance with an embodiment of the present disclosure; and,
FIG. 6 is a block diagram illustrating an exemplary structure of the wireless device configured in accordance with an embodiment of the present disclosure.



DETAILED DESCRIPTION
A discussion is provided first herein to describe an exemplary wireless communication network that includes multiple CN nodes (e.g., SGSNs, MMEs), multiple RAN nodes (e.g., BSSs, eNodeBs), and multiple wireless devices (e.g., MSs) in accordance with an embodiment of the present disclosure (see FIG. 1). Then, a discussion is provided to disclose different techniques that the RAN node can use to signal that a network restart has occurred and if desired other related information to the wireless devices in accordance with various embodiments of the present disclosure (see FIG. 2). Thereafter, a discussion is provided to explain the basic functionalities-configurations of the RAN node (e.g., BSSs, eNodeBs) and the wireless device (e.g., MS) in accordance with different embodiments of the present disclosure (see FIGS. 3-6).
Exemplary Wireless Communication Network 100
Referring to FIG. 1, there is illustrated an exemplary wireless communication network 100 in accordance with the present disclosure. The wireless communication network 100 includes a core network 106 (which comprises a pool of CN nodes 1071, 1072 . . . 107n) and multiple RAN nodes 1021 and 1022 (only two shown) which interface with multiple wireless devices 1041, 1042, 1043 . . . 104n. The wireless communication network 100 also includes many well-known components, but for clarity, only the components needed to describe the features of the present disclosure are described herein. Further, the wireless communication network 100 is described herein as being a GSM/EGPRS wireless communication network 100 which is also known as an EDGE wireless communication network 100. However, those skilled in the art will readily appreciate that the techniques of the present disclosure which are applied to the GSM/EGPRS wireless communication network 100 are generally applicable to other types of wireless communication systems, including, for example, WCDMA, LTE, and WiMAX systems.
The wireless communication network 100 includes the RAN nodes 1021 and 1022 (wireless access nodes—only two shown) which provide network access to the wireless devices 1041, 1042, 1043 . . . 104n. In this example, the RAN node 1021 is providing network access to wireless device 1041 while the RAN node 1022 is providing network access to wireless devices 1042, 1043 . . . 104n. The RAN nodes 1021 and 1022 are connected to the core network 106 (e.g., SGSN core network 106) and, in particular, to the pool of CN nodes 1071, 1072 . . . 107n (e.g., SGSNs 1071, 1072 . . . 107n). The core network 106 is connected to an external packet data network (PDN) 108, such as the Internet, and a server 110 (only one shown). The wireless devices 1041, 1042, 1043 . . . 104n may communicate with one or more servers 110 (only one shown) connected to the core network 106 and/or the PDN 108.
The wireless devices 1041, 1042, 1043 . . . 104n may refer generally to an end terminal (user) that attaches to the wireless communication network 100, and may refer to either a MTC device (e.g., a smart meter) or a non-MTC device. Further, the term “wireless device” is generally intended to be synonymous with the term mobile device, mobile station (MS). “User Equipment,” or UE, as that term is used by 3GPP, and includes standalone wireless devices, such as terminals, cell phones, smart phones, tablets, and wireless-equipped personal digital assistants, as well as wireless cards or modules that are designed for attachment to or insertion into another electronic device, such as a personal computer, electrical meter, etc.
Likewise, unless the context clearly indicates otherwise, the term RAN node 1021 and 1022 (wireless access node 1021 and 1022) is used herein in the most general sense to refer to a base station, a wireless access node, or a wireless access point in a wireless communication network 100, and may refer to RAN nodes 1021 and 1022 that are controlled by a physically distinct radio network controller as well as to more autonomous access points, such as the so-called evolved Node Bs (eNodeBs) in Long-Term Evolution (LTE) networks.
Each wireless device 1041, 1042, 1043 . . . 104n may include a transceiver circuit 1101, 1102, 1103 . . . 110n for communicating with the RAN nodes 1021 and 1022, and a processing circuit 1121, 1122, 1123 . . . 112n for processing signals transmitted from and received by the transceiver circuit 1101, 1102, 1103 . . . 110n and for controlling the operation of the corresponding wireless device 1041, 1042, 1043 . . . 104n. The transceiver circuit 1101, 1102, 1103 . . . 110n may include a transmitter 1141, 1142, 1143 . . . 114n and a receiver 1161, 1162, 1163 . . . 116n, which may operate according to any standard, e.g., the GSM/EDGE standard. The processing circuit 1121, 1122, 1123 . . . 112n may include a processor 1181, 1182, 1183 . . . 118n and a memory 1201, 2102, 1203 . . . 120n for storing program code for controlling the operation of the corresponding wireless device 1041, 1042, 1043 . . . 104n. The program code may include code for performing the procedures as described hereinafter with respect to FIG. 5.
Each RAN node 1021 and 1022 (wireless access node 1021 and 1022) may include a transceiver circuit 1221 and 1222 for communicating with wireless devices 1041, 1042, 1043 . . . 104n a processing circuit 1241 and 1242 for processing signals transmitted from and received by the transceiver circuit 1221 and 1222 and for controlling the operation of the corresponding RAN node 1021 and 1022, and a network interface 1261 and 1262 for communicating with the core network 106. The transceiver circuit 1221 and 1222 may include a transmitter 1281 and 1282 and a receiver 1301 and 1302, which may operate according to any standard, e.g., the GSM/EDGE standard. The processing circuit 1241 and 1242 may include a processor 1321 and 1322, and a memory 1341 and 1342 for storing program code for controlling the operation of the corresponding RAN node 1021 and 1022. The program code may include code for performing the procedures as described hereinafter with respect to FIG. 3.
Each CN node 1071, 1072 . . . 107n (e.g., SGSN 1071, 1072 . . . 107n, MME 1071, 1072 . . . 107n) may include a transceiver circuit 136 for communicating with the RAN nodes 1021 and 1022, a processing circuit 138 for processing signals transmitted from and received by the transceiver circuit 136 and for controlling the operation of the CN node 1071, 1072 . . . 107n, and a network interface 140 for communicating with the RAN nodes 1021 and 1022. The transceiver circuit 136 may include a transmitter 142 and a receiver 144, which may operate according to any standard, e.g., the GSM/EDGE standard. The processing circuit 138 may include a processor 146 and a memory 148 for storing program code for controlling the operation of the CN node 1071, 1072 . . . 107n. The program code may include code for performing the procedures as described hereinafter.
Signaling Core Network Restart
A discussion is provided hereinafter to describe various techniques that the RAN node 1022 (for example) can use to signal to the wireless devices 1042, 1043 . . . 104n (for example) that a network restart has occurred and optionally also signal which CN node 1071, 1072 . . . 107n in the pool area has been restarted. Some of these techniques are as follows:
I. Add bits in one or more messages to indicate that the network restart has occurred and optionally which CN node 1071, 1072 . . . 107n in the pool area has been restarted, where the one or more of the messages are (i) mapped onto channel(s) which the wireless devices 1042, 1043 . . . 104n regularly (periodically) wake up to monitor prior to attempting to receive pages for reading the wireless device's paging group, or (ii) mapped onto channel(s) that is/are monitored regularly (periodically) by the wireless devices 1042, 1043 . . . 104n while in idle mode. Such a message could, for example, be conveyed as one or more of the following: (1) over a Synchronization Channel (SCH), (2) as one or more of the Broadcast Channel System Information (SI) messages, and (3) over the Common Control Channels (CCCHs), such as the Access Grant Channel (AGCH) and the Paging Channel (PCH).
II. An ‘in-band’ signaling in existing channels. ‘In-band’ in this regard refers to the use of procedures that result in the addition of supplemental information bits in conjunction with a message transfer without changing the content of the message itself, where the supplemental information bits indicate that a network restart has occurred and optionally which CN node 1071, 1072 . . . 107n in the pool area has been restarted. This ‘in-band’ signaling can, for example, be realized by having the RAN node 1022 use a so-called “super channel” wherein existing channel(s) are overlayed with a low bit rate channel (i.e., a supplemental information channel) which indicates that a network restart has occurred and optionally which CN node 1071, 1072 . . . 107n in the pool area has been restarted by using (1) different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern in the message, for example, the message-specific Cyclic Redundancy Check (CRC) bits. A more detailed discussion is provided below with respect to FIG. 2 about the super channel and how different modulation symbol rotations or modulation indexes can be used for signaling to the wireless devices 1042, 1043 . . . 104n that a network restart has occurred and optionally which CN node 1071, 1072 . . . 107n in the pool area has been restarted. The basic technical features of the super channel were first discussed in the co-assigned U.S. Provisional Application Ser. No. 62/023,453, filed Jul. 11, 2014, and entitled “Transmitter, Receiver and Methods Therein”. The contents of this document are hereby incorporated herein by reference for all purposes.
Furthermore, the network (e.g., the RAN node 1022) can provide the wireless devices 1042, 1043 . . . 104n with information indicating the longest-used paging cycle in the cell to allow the wireless devices 1042, 1043 . . . 104n to understand that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the identified longest used paging cycle. This information may be provided either:
1. By the Base Station Subsystem (BSS)/Base Transceiver Station (BTS), Radio Network Controller (RNC)/Node B (NB)/Evolved Node B (eNB), in one of the SI messages;
or
2. By the SGSN/Mobility Management Entity (MME) in one of the downlink NAS messages, e.g., GPRS Attach Accept, RAU Accept.
An alternative technique would be to have a predefined maximum duration wherein the network restart indication is in effect. That is, once a network restart is first signaled, the network restart notification remains in effect for this predefined maximum duration. As such, upon first detecting that a network restart has occurred, the wireless device 1042 (for example) will only perform a single re-registration while the network restart notification remains in effect (e.g., enabled). Once the network restart notification is determined to no longer be in effect (e.g., disabled), the wireless device 1042 (for example) shall once again be subject to detecting another network restart notification and, therefore, responding by performing another re-registration. As an example, with EC-GSM where it is proposed to set the maximum eDRX cycle to 52 minutes, the core network restart indication could have a predefined maximum duration of 1 hour (the maximum eDRX cycle length plus eight minutes can be used to keep signaling of the predefined maximum duration simple). For general details about EC-GSM, reference is made to 3GPP TSG GERAN Adhoc#1 on FS_IoT_LC Tdoc GPC150081, entitled “EC-GSM—eDRX and TDMA FN Space Wrap Around”, dated 2-5 Feb. 2015. The contents of this document are hereby incorporated herein by reference for all purposes.
In the following discussion several exemplary techniques are described which the RAN node 1022 (for example) could use for signaling an indication 303 to the wireless devices 1042, 1043 . . . 104n (for example) that a network restart has occurred and optionally also signal which CN node 1071, 1072 . . . 107n in the pool area has been restarted and/or the longest used paging cycle. The following detailed discussion is based on a scenario where the RAN node 1022 (for example) signals the core network restart etc . . . to wireless devices 1042, 1043 . . . 104n (for example) operating in an eDRX mode in an EC-GSM system 100. Further, the techniques described hereinafter for signaling that a network restart has occurred etc . . . depend on the operation of the wireless devices 1042, 1043 . . . 104n (for example), e.g., if the signaling is to a normal coverage wireless device 1042 (for example) or to an extended coverage wireless device 1043 (for example). Recall: the normal coverage wireless device 1042 (for example) is operating with radio interface performance attributes corresponding to the reference coverage which is considered to be in the best coverage class (i.e., coverage class 1) and therefore does not make blind transmissions. The extended coverage wireless device 1043 (for example) is operating with radio interface performance attributes corresponding to an extended coverage (i.e., coverage class greater than 1) and therefore needs to make blind transmissions. In the following detailed discussion, only the applicability to GSM is described. However, the described principles and techniques would apply to any technology where paging-based reachability is supported or where a wireless device needs to be notified that there has been a core network error resulting in a loss of device-specific information such that the wireless devices will have to perform a re-registration.
Signaling of Core Network Restart to Normal Coverage Wireless Device 1042 (For Example)
The normal coverage wireless device 1042 (for example) uses timeslot zero (TS0) for reading SI, downlink Common Control Channels (CCCHs), such as the AGCH and PCH, as well as for reading the Frequency Correction Channel (FCCH) and the Synchronization Channel (SCH). The latter channels (i.e., FCCH and SCH) are used by the wireless device 1042 to synchronize to the network 100 before making a network access and/or reading a page. In the present disclosure, the normal coverage wireless device 1042 that operates in eDRX mode and that has been in a power saving state for a while, e.g., 5 minutes, may have drifted both in frequency and time and thus needs to re-synchronize itself to the network 100 in order to successfully read a page.
In one embodiment, the normal coverage wireless device 1042 would, while synchronizing itself with the network 100, also acquire information about a core network 106 namely that a network restart has occurred and optionally which CN node 1071, 1072 . . . 107n in the pool area has been restarted and/or the longest used paging cycle. The signaling of this information by the RAN node 1022 and the wireless device 1042 acquiring this information may be achieved by the use of the so-called super channel solution (e.g., briefly discussed above) which provides a low bit rate channel (e.g., in-band channel, supplement information channel) on top of at least one existing channel without impacting legacy wireless devices. The basic idea is to use, for example, relative changes in the phase of the burst (i.e., modulation angle) as a means to carry information (e.g., a network restart has occurred, the particular CN node 1071, 1072 . . . 107n in the pool area that has been restarted, the longest used paging cycle). Since the wireless device 1042 needs to synchronize itself to the network 100 it needs to read the FCCH and SCH burst on TS0, where the phase information of these two bursts and the immediately following bursts are ideal for conveying additional information (e.g., a network restart has occurred, the particular CN node 1071, 1072 . . . 107n in the pool area that has been restarted, the longest used paging cycle) to the wireless device 1042 in eDRX mode. It is to be noted that, since all bursts sent on TS0 in GSM need to be transmitted with full power, using Gaussian Minimum Phase Shift Keying (GMSK) modulation, and using the same Training Sequence Code (TSC) signal (e.g., applying for the Broadcast Control Channel (BCCH), AGCH, and PCH), it is suitable to be used as a carrier for the super channel (i.e., the supplemental information channel) since it will reach all the wireless devices 1042, 1043 . . . 104n (for example) in the cell.
Referring to FIG. 2, there is a diagram illustrating an example where the RAN node 1022 (for example) can provide a low bit rate channel (i.e., the supplemental information channel) through the use of different phase angles (i.e., illustrated by “+” and “−”signs, corresponding to 0 degree or 180 degree phase shift, for example) on the first two bursts on the FCCH and SCH, and the eight additional bursts of TS0 occurring immediately thereafter. In this case, within any given 51-multiframe, 5 sets of these 10 consecutive bursts of TS0 (each starting with a pair of FCCH and SCH bursts on TS0) will be supported. The first set of these 10 bursts occurring in TS0 of the first 10 TDMA frames within a 51-multiframe occur on the first pair of FCCH and SCH bursts in the 51-multiframe followed by 4 BCCH bursts and 4 BCCH EXT/AGCH bursts which can be used to signal that a network restart has occurred and other related information (see above) to the wireless device 1042 (for example) in accordance with an embodiment of the present disclosure. The “+” and “−” phases illustrated may, e.g., correspond to “1” and “0”, respectively, and thus, in this example of the first 10 bursts within a 51-multiframe, the signal would be “1110101000” which can indicate to the wireless device 1042 that a network restart has occurred and other related information as discussed in more detail next. In this example, the most significant bit (i.e., the first bit position out of the total ten bits “1110101000”) can be used as a phase reference to which bit positions 2-10 change their phases. For example, to signal a core network restart, the second bit could use a phase difference of 180 degrees relative to the reference bit (e.g., first bit in FIG. 2), while no phase change relative to the reference bit is used if there is no core network restart. The other 8 bits may be used to indicate which CN node 1071, 1072 . . . 107n in the pool area has been restarted, the longest used paging cycle, and/or a SI version/vintage counter. The advantage of including a SI version/vintage counter would be that, during the synchronization process, the wireless device 1042 (for example) would also be able to determine if there is a need to re-acquire any of the SI messages. Note: the previously described signaling techniques that do not involve the use of the “super channel” can if desired also signal the SI version/vintage counter.
In another embodiment, these 8 bits can carry the Network Resource Identifier (NRI) or parts of the NRI bitmap of the CN node 1071, 1072 . . . 107n that has restarted. The wireless device 1042 (for example) can then compare this NRI value with the NRI portion of their P-TMSI to determine if they need to perform a re-registration.
In yet another embodiment, some of these 8 bits can be used to convey the SI version/vintage counter without the need to also carry the identity of the particular CN node 1071, 1072 . . . 107n in the pool area that has been restarted. In this case, when the wireless device 1042 (for example) detects that the value of the SI version/vintage counter has changed, the wireless device 1042 thereby knows it needs to re-acquire SI. The SI can include new information that indicates when one or more CN nodes 1071, 1072 . . . 107n have experienced a restart and the identities of the specific CN nodes 1071, 1072 . . . 107n (e.g., a list of NRIs) which has experienced a restart. In this example, the wireless device 1042 plus other normal coverage wireless devices in possession of a P-TMSI whose NRI portion matches one of the NRIs in the SI's information will determine that they need to perform the RAU procedure (re-registration procedure) to acquire a new P-TMSI. It is to be noted that the NRI of a CN node 1071, 1072 . . . 107n is expected to remain the same whenever that CN node 1071, 1072 . . . 107n experiences a restart event.
In another embodiment, 5 of these 8 bits are used to signal a pool unique identity for the CN node 1071, 1072 . . . 107n that has restarted (e.g., 5 bits), while the other 3 bits are used to identify a SI version/vintage counter. The wireless device 1042 (for example) thereby detects that the signaled pool unique identity corresponds to the CN node 1071 (for example) that it last registered with and therefore it performs a new NAS registration procedure (after first re-acquiring system information if required according to the SI version/vintage counter). Note that when any given NAS registration procedure is performed the CN node 1071 (for example) responsible for handling the wireless device 1042 (for example) may include the pool unique identity in a new Information Element (IE) in any of the downlink NAS messages, such as the RAU accept message, for example.
The aforementioned exemplary scheme shown in FIG. 2 is just one possible realization of the super channel. In another embodiment, in order to be able to handle multiple core network restarts within the duration of the longest supported paging cycle in the cell, more than one bit may be needed to signal a core network restart. In yet another embodiment that does not entail the supper channel, the messages on the AGCH and the PCH are updated to carry an indication that a network restart has taken place. For instance, the indication that a restart has taken place can be provided in a completely new IE or by reusing an unused code point “11” in the Page Mode IE, for example. The identity of the impacted CN node(s) 1071, 1072 . . . 107n may be included in a new IE in the AGCH/PCH messages or as a new IE in an existing or a new SI message. A wireless device 1042 (for example) in eDRX mode can then detect that the CN node 1071, 1072 . . . 107n to which it is registered has restarted and then can proceed, as when a legacy device receives a page with IMSI, i.e., by sending a re-registration message to the RAN node 1022.
Signaling of Core Network Restart to Extended Coverage Wireless Device 1043 (For Example)
The extended coverage wireless device 1043 (for example) will read SI as well as the synchronization channels on timeslot 1 (TS1). The redesign of the SCH, where the complete set of EC-SCH blocks are transmitted over the first seven Time Division Multiple Access (TDMA) frames in two consecutive 51-multiframes, results in 6 spare bits in the EC-SCH content. These 6 spare bits are realized by re-organizing the 25 bit payload space of the legacy SCH to instead provide a reduced amount of TDMA frame number information which is sufficient for wireless devices 1041, 1042, 1043 . . . 104n that operate using extended coverage. The extended coverage wireless devices 1041, 1042, 1043 . . . 104n will commonly acquire the EC-SCH which can serve as a convenient logical channel for indicating when a network restart has occurred using one or more of these 6 spare bits. In fact, it has already been proposed to use some of these 6 bits to convey overload control information and BCCH_CHANGE_MARK information. This proposal was discussed, for example, in 3GPP TSG GERAN Adhoc#1 on FS_IoT_LC Tdoc GPC150064, entitled “EC-GSM—EC-SCH design, performance and mapping” dated 2-5 Feb. 2015—the contents of which are hereby incorporated herein by reference for all purposes). In one embodiment, it is proposed to use one of these spare bits to signal that a network restart has occurred to the wireless device 1043 (for example), followed by having the wireless device 1043 read one or more SI messages to determine the identity (e.g., NRI or pool unique identity) of the CN node 1071, 1072 . . . 107n that has restarted. In another embodiment, the super channel may be used, similar to the aforementioned normal coverage scenario for indicating both that a network restart has occurred as well as which CN node 1071, 1072 . . . 107n has been restarted. In extended coverage, redundancy might need to be added to the coding of the super channel in order to reach the wireless devices currently in extended coverage.
In another embodiment, the SI version/vintage counter, i.e., the indication to the wireless device 1043 (for example) that the SI has changed, may be used to communicate the core network restart. For instance, if a change in SI version/vintage counter occurs, then the wireless device 1043 will reacquire the SI, and by that, read a flag in the SI that indicates that a core network restart has occurred as well as the identity of the CN node 1071, 1072 . . . 107n that has restarted.
In yet another embodiment, a bit-wise modulo 2 operation may be performed on a known part of a message monitored by the wireless device 1043 (for example). This known part can, for example, be the CRC bits of the EC-SCH message, and a bit would be obtained in the decoding process of the message. If the bit indicates that a restart has occurred, then the wireless device 1043 (for example) would re-acquire the SI, and by that, read a flag in the SI that indicates that a core network restart has occurred as well as the identity of the CN node 1071, 1072 . . . 107n that has restarted.
In yet another embodiment, the signaling of a core network restart may be performed using a negative modulation index for GMSK-modulated bursts, the basics of this signaling scheme are discussed, for example, in U.S. Provisional Application No. 62/039,489, filed Aug. 20, 2014, entitled “Radio Network Node, Wireless Device and Methods Thereof Using GMSK Modulation Applying Negative Modulation Index” (the contents of this document are hereby incorporated herein by reference for all purposes). In this case, the wireless device 1043 (for example) detects which of two modulation indices is used where one indicates that a core network restart has not occurred, and the other one indicates that a core network restart has occurred.
In all these embodiments, an effective result is that a wireless device 1043 (for example) in extended coverage and in eDRX mode would detect that the CN node 1071, 1072 . . . 107n, to which the wireless device 1043 is registered, has restarted, and therefore, the wireless device 1043 would proceed as when a legacy wireless device receives a page with IMSI, i.e., the wireless device 1043 would know it needed to perform a re-registration.
Signaling of Longest-Used Paging Cycle in the Cell
In order for the network 100 to be able to signal to all wireless devices 1042, 1043 . . . 104n (for example) in the cell that a network restart has occurred, the core network restart signaling could as discussed above be enabled for at least the duration of the longest paging cycle that is in use in the cell. As an example, assume the longest paging cycle in use in the cell is 30 minutes. This would mean that a wireless device 1042 (for example) with a 5 minute paging cycle duration would detect that a core network restart has occurred up to 6 times within a 30 minute window and, if no other information was available, the wireless device 1402 would perform a re-registration 6 times when re-registering once would have been sufficient.
In order to allow a wireless device 1042 (for example) to determine whether another re-registration is needed after initially detecting a network restart indication and registering, it is proposed to signal in addition to the network restart information an indication indicating the longest-used paging cycle in the cell if the maximum specified value is not already used in the cell. With this additional information the wireless device 1042 (for example) that initially detects a network restart indication and therefore registers will ignore any additional network restart indications detected thereafter for a time period indicated by the longest-used paging cycle in the cell. If the maximum specified value for the longest paging cycle that can be used in the cell is assumed to be fixed (i.e., it will never be changed in a future release of the specifications), then the wireless device 1042 could default to using the longest paging cycle supported by the specifications to determine the maximum-used paging cycle in the cell and would therefore not need to be explicitly signaled the longest-used paging cycle in the cell. With this assumption the wireless device 1042 would implicitly know that the signaling of a core network restart will remain in effect for a time period determined using the longest paging cycle supported by the specifications (i.e., a predefined maximum duration). In summary, if the wireless device 1042 is explicitly signaled the longest-used paging cycle used for the cell then that is what it uses to determine the time period for which it ignores any additional network restart indications detected after first detecting an initial restart indication and registering. For the case where the longest-used paging cycle used for the cell is not explicitly signaled the wireless device 1042 can default to using the maximum paging cycle supported by the specifications as the maximum-used paging cycle in the cell and therefore use this default value to determine a predefined maximum duration (e.g., 1 hour) for which it ignores any additional network restart indications detected after first detecting an initial restart indication and registering.
Once the network restart notification is determined to not be in effect (i.e., disabled), the wireless device 1042 shall once again be subject to detecting another network restart notification and therefore responding by performing another re-registration. As an example, with EC-GSM where it is proposed to set the maximum eDRX cycle to 52 minutes (e.g., as discussed in the aforementioned GPC150081), a predefined maximum duration for the core network restart indication could be 1 hour (the maximum eDRX cycle length plus eight minutes can be used to keep signaling of the predefined maximum duration simple).
It is proposed, but not limited, to either broadcast the maximum-used paging cycle in the cell in the SI or to provide the wireless device 1042 (for example) with this information whenever the wireless device 1042 performs an attach to the network 100 or to not signal this information and thereby allow the wireless device 1042 (for example) to default to using the longest paging cycle supported by the specifications as the maximum-used paging cycle in the cell. Alternatively, this information may be sent from the CN node 1071, 1072 . . . 107n (e.g., SGSN 1071, 1072 . . . 107n) to the wireless device 1042 in any of the downlink NAS messages, such as GPRS Attach Accept, Routing Area Update Accept, or Activate PDP Context Accept, for example. The wireless device 1042 can then determine the predefined maximum duration (e.g., from the broadcast/provided maximum-used paging cycle or from the default longest paging cycle supported by the specifications) so that it may send only one re-registration message during this determined predefined maximum duration.
Basic Functionalities-Configurations of RAN Node 1022 and Wireless Device 1042 (For Example)
Referring to FIG. 3, there is a flowchart of a method 300 implemented in the RAN node 1022 (e.g., BSS 1022, eNodeB 1022) in accordance with an embodiment of the present disclosure. At step 302, the RAN node 1022 signals to the wireless devices 1042, 1043 . . . 104n (for example) an indication 303 that a network restart has occurred in a CN node 1071 (for example) in a pool of CN nodes 1071, 1072 . . . 107n (note: the indication 303 does not necessarily have to indicate the particular CN 1071 (for example) that has been restarted but instead just has to indicate that a CN node has been restarted). As discussed above, there are various exemplary ways that the RAN node 1022 can perform step 302 some of which are as follows:

    
    
        (1) The RAN node 1022 is operable to signal the indication 303 by mapping a message including the indication 303 onto a channel (e.g., BCCH, SCH), which each of the wireless devices 1042, 1043 . . . 104n periodically wakes up to monitor prior to attempting to receive a paging message, wherein this periodicity of monitoring the channel may be higher (more frequent) than the periodicity that each of the wireless device 1042, 1043 . . . 104n uses for monitoring paging messages (see step 302a).
        (2) The RAN node 1022 is operable to signal the indication 303 by mapping a message including the indication 303 onto a channel (e.g., BCCH, SCH), which is periodically monitored by each of the wireless devices 1042, 1043 . . . 104n while in idle mode, wherein the periodicity of monitoring the channel may be higher (more frequent) than the periodicity that each of the wireless devices 1042, 1043 . . . 104n uses for monitoring paging messages (see step 302b).
        (3) The RAN node 1022 is operable to signal the indication 303 by ‘in-band’ signaling that includes signaling the indication 303 in conjunction with a transfer of a message without changing a content of the message. In one example, the RAN node 1022 is operable to perform the ‘in-band’ signaling by overlaying the at least one channel (e.g., the SCH or EC-SCH), which is periodically monitored by the wireless devices 1042, 1043 . . . 104n with a supplemental information channel (e.g., the super channel, low bit rate channel) that signals the indication 303 (the network restart information etc . . . ) by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern (step 302c).
    
    


The indication 303 in addition to indicating that a network restart has occurred could also indicate at least one the following (for example): (1) identify the particular CN node 1071 (for example) that has been restarted; (2) identify a longest used paging cycle in a cell to indicate to the wireless device 1042 (for example) that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and (3) identify a SI version or SI vintage counter.
At step 304, the RAN node 1022 receives from at least one of the wireless devices 1042, 1043 . . . 104n (e.g., all or a subset of the wireless devices 1042, 1043 . . . 104n) a re-registration message 305 (e.g., RAU Request message 305) in response to the signaling of the indication that the network restart has occurred. After step 304, the RAN node 1022 can operate to forward the re-registration message 305 to the appropriate CN node 1071 (for example). Upon receiving the re-registration message 305, the CN node 1071 completes the RAU procedure along with any additional NAS signaling procedures (e.g., PDP Context Activation) with the re-registering wireless device 1042 (for example) thereby resulting in the CN node 1071 having re-acquired all necessary information for that wireless device 1042 (for example) subsequent to the CN node 1071 experiencing a restart condition. The RAN node 1022 by operating in this manner results in a faster and much more paging bandwidth-efficient scheme to address a network restart when compared to the existing mechanism where the traditional RAN node individually informs each mobile station of a network restart event using IMSI-based paging. The other RAN node 1021 can also be configured in a similar manner to perform method 300.
Referring to FIG. 4, there is a block diagram illustrating structures of an exemplary RAN node 1022 (for example) configured in accordance with an embodiment of the present disclosure. In one embodiment, the RAN node 1022 may comprise a signal module 402, and a receive module 404. The signal module 402 is configured to signal to the wireless devices 1042, 1043 . . . 104n (for example) an indication 303 that a network restart has occurred in a CN node 1071 (for example) in a pool of CN nodes 1071, 1072 . . . 107n (note: the indication 303 does not necessarily have to indicate the particular CN 1071 (for example) that has been restarted but instead just has to indicate that a CN node has been restarted). There are various exemplary ways that the signal module 402 can be configured to signal to the wireless devices 1042, 1043 . . . 104n the indication 303 that the network restart has occurred in a CN node 1071 (for example) some of which are as follows:

    
    
        (1) The signal module 402 is configured to signal the indication 303 by mapping a message including the indication 303 onto a channel (e.g., BCCH, SCH), which each of the wireless devices 1042, 1043 . . . 104n periodically wakes up to monitor prior to attempting to receive a paging message, wherein this periodicity of monitoring the channel may be higher (more frequent) than the periodicity that each of the wireless devices 1042, 1043 . . . 104n uses for monitoring paging messages (see step 302a).
        (2) The signal module 402 is configured to signal the indication 303 by mapping a message including the indication onto a channel (e.g., BCCH, SCH), which is periodically monitored by each of the wireless devices 1042, 1043 . . . 104n while in idle mode, wherein the periodicity of monitoring the channel may be higher (more frequent) than the periodicity that each of the wireless devices 1042, 1043 . . . 104n uses for monitoring paging messages (see step 302b).
        (3) The signal module 402 is configured to signal the indication 303 by ‘in-band’ signaling that includes signaling the indication 303 in conjunction with a transfer of a message without changing a content of the message. In one example, the signal module 402 is configured to perform the ‘in-band’ signaling by overlaying the at least one channel (e.g., SCH or EC-SCH), which is periodically monitored by the wireless devices 1042, 1043 . . . 104n with a supplemental information channel (e.g., the super channel, low bit rate channel) that signals the indication 303 (the network restart information etc . . . ) by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern (see step 302c).
    
    


The indication 303 in addition to indicating that a network restart has occurred could also indicate at least one the following (for example): (1) identify the particular CN node 1071 (for example) that has been restarted; (2) identify a longest used paging cycle in a cell to indicate to the wireless device 1042 (for example) that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and (3) identify a SI version or SI vintage counter.
The receive module 404 is configured to receive from at least one of the wireless devices 1042, 1043 . . . 104n (e.g., all or a subset of the wireless devices 1042, 1043 . . . 104n) a re-registration message 305 (e.g., RAU Request message 305) in response to the signaling of the indication that the network restart has occurred. The RAN node 1022 can include one or more additional modules which upon receipt of the re-registration messages 305 can be configured to forward the re-registration message 305 to the appropriate CN node 1071 (for example). Upon receiving the re-registration message 305, the CN node 1071 completes the RAU procedure along with any additional NAS signaling procedures (e.g., PDP Context Activation) with the re-registering wireless device 1042 (for example) thereby resulting in the CN node 1071 having re-acquired all necessary information for that wireless device 1042 (for example) subsequent to the CN node 1071 experiencing a restart condition. The RAN node 1022 is specially configured to implement a faster and much more paging bandwidth-efficient scheme to address a network restart when compared to the existing mechanism where the traditional RAN node individually informs each mobile station of a network restart event using IMSI-based paging. The other RAN node 1021 can also be configured in a similar manner with the illustrated structures (or similar structures) of the exemplary RAN node 1022 of FIG. 4. Further, it should be noted that the RAN node 1022 may also include other components, modules or structures which are well-known, but for clarity, only the components, modules or structures needed to describe the features of the present disclosure are described herein.
As those skilled in the art will appreciate, the above-described modules 402 and 404 of the RAN node 1022 (e.g., BSS 1022, eNodeB 1022) may be implemented separately as suitable dedicated circuits. Further, the modules 402 and 404 can also be implemented using any number of dedicated circuits through functional combination or separation. In some embodiments, the modules 402 and 404 may be even combined in a single application specific integrated circuit (ASIC). As an alternative software-based implementation, the RAN node 1022 may comprise a memory 1342, a processor 1322 (including but not limited to a microprocessor, a microcontroller or a Digital Signal Processor (DSP), etc.) and a transceiver 1222. The memory 1342 stores machine-readable program code executable by the processor 1322 to cause the RAN node 1022 (e.g., BSS 1022, eNodeB 1022) to perform the steps of the above-described method 300. It should be appreciated that the other RAN nodes 1021 (for example) can also be configured in a similar manner as the RAN node 1022 to perform method 300.
Referring to FIG. 5, there is a flowchart of a method 500 implemented in the wireless device 1042 (for example) in accordance with an embodiment of the present disclosure. At step 502, the wireless device 1042 receives a signal from the RAN node 1022, where the signal has an indication 303 that a network restart has occurred in a CN node 1071 (for example) in a pool of CN nodes 1071, 1072 . . . 107n (note: the indication 303 does not necessarily have to indicate the particular CN 1071 (for example) that has been restarted but instead just has to indicate that a CN node has been restarted). As discussed above, there are various exemplary ways that the wireless device 1042 can perform step 502 some of which are as follows:

    
    
        (1) The wireless device 1042 is operable to receive the indication 303 included in a message that is mapped onto a channel (e.g., BCCH, SCH), which the wireless device 1042 periodically wakes up to monitor prior to attempting to receive a paging message, wherein the periodicity of monitoring the channel may be higher (more frequent) than the periodicity that the wireless device 1042 uses for monitoring paging messages (see step 502a).
        (2) The wireless device 1042 is operable to receive the indication 303 included in a message that is mapped onto a channel (e.g., BCCH, SCH), which is periodically monitored by the wireless device 1042 while in idle mode, wherein the periodicity of monitoring the channel may be higher (more frequent) than the periodicity that the wireless device 1042 uses for monitoring paging messages (see step 502b).
        (3) The wireless device 1042 is operable to receive the indication 303 via ‘in-band’ signaling which includes the indication 303 being obtained upon receiving a message where a content of the message does not include the indication 303. In one example, the wireless device 1042 is operable to obtain the indication 303 from a supplemental information channel that overlays at least one channel (e.g., SCH or EC-SCH) that is periodically monitored by the wireless device 1042, wherein the supplemental information channel signals the indication 303 by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern (step 502c).
    
    


The indication 303 in addition to indicating that a network restart has occurred could also indicate one or more of the following (for example): (1) identify the particular CN node 1071 (for example) that has been restarted; (2) identify a longest used paging cycle in a cell to indicate to the wireless device 1042 (for example) that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and (3) identify a SI version or SI vintage counter.
At step 504, the wireless device 1042 transmits to the RAN node 1022 a re-registration message 305 (e.g., RAU Request message 305) in response to the receipt of the indication 303 that the network restart has occurred. After transmitting the re-registration message 305, the wireless device 1042 completes the RAU procedure along with any additional NAS signaling procedures (e.g., PDP Context Activation) with the appropriate CN node 1071 (for example) thereby resulting in the CN node 1071 having re-acquired all necessary information for that wireless device 1042 subsequent to the CN node 1071 experiencing a restart condition. The wireless device 1042 by operating in this manner results in a faster and much more paging bandwidth-efficient scheme to address a network restart when compared to the existing mechanism wherein the traditional RAN node informed the individual mobile stations of a network restart event using IMSI-based paging. The other wireless device 1041, 1043 . . . 104n can also be configured in a similar manner to perform method 500.
Referring to FIG. 6, there is a block diagram illustrating structures of an exemplary wireless device 1042 (for example) configured in accordance with an embodiment of the present disclosure. In one embodiment, the wireless device 1042 may comprise a receive module 602, and a transmit module 604. The receive module 602 is configured to receive a signal from the RAN node 1022, where the signal has an indication 303 that a network restart has occurred in a CN node 1071 (for example) in a pool of CN nodes 1071, 1072 . . . 107n (note: the indication 303 does not necessarily have to indicate the particular CN 1071 (for example) that has been restarted but instead just has to indicate that a CN node has been restarted). There are various exemplary ways that the receive module 602 can be configured to receive the indication 303 that the network restart has occurred in a CN node 1071 (for example) some of which are as follows:

    
    
        (1) The receive module 602 is configured to receive the indication 303 included in a message that is mapped onto a channel (e.g., BCCH, SCH), which the wireless device 1042 periodically wakes up to monitor prior to attempting to receive a paging message, wherein the periodicity of monitoring the channel may be higher (more frequent) than the periodicity that the wireless device 1042 uses for monitoring paging messages (see step 502a).
        (2) The receive module 602 is configured to receive the indication 303 included in a message that is mapped onto a channel (e.g., BCCH, SCH), which is periodically monitored by the wireless device 1042 while in idle mode, wherein the periodicity of monitoring the channel may be higher (more frequent) than the periodicity that the wireless device 1042 uses for monitoring paging messages (see step 502b).
        (3) The receive module 602 is configured to receive the indication 303 via ‘in-band’ signaling which includes the indication 303 being obtained upon receiving a message where a content of the message does not include the indication 303. In one example, the wireless device 1042 is operable to obtain the indication 303 from a supplemental information channel that overlays at least one channel (e.g., SCH or EC-SCH) that is periodically monitored by the wireless device 1042, wherein the supplemental information channel indicates the indication 303 by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern (step 502c).
    
    


The indication 303 in addition to indicating that a network restart has occurred could also indicate one or more of the following (for example): (1) identify the particular CN node 1071 (for example) that has been restarted; (2) identify a longest used paging cycle in a cell to indicate to the wireless device 1042 (for example) that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and (3) identify a SI version or SI vintage counter.
The transmit module 604 is configured to transmit to the RAN node 1022 a re-registration message 305 (e.g., RAU Request message 305) in response to the receipt of the indication 303 that the network restart has occurred. The wireless device 1042 can include one or more additional modules which after transmitting the re-registration message 305 can be configured to complete the RAU procedure along with any additional NAS signaling procedures (e.g., PDP Context Activation) with the appropriate CN node 1071 (for example) thereby resulting in the CN node 1071 having re-acquired all necessary information for that wireless device 1042 subsequent to the CN node 1071 experiencing a restart condition. The wireless device 1042 by operating in this manner results in a faster and much more paging bandwidth-efficient scheme to address a network restart when compared to the existing mechanism wherein the traditional RAN node informed the individual mobile stations of a network restart event using IMSI-based paging. The other wireless devices 1041, 1043 . . . 104n can also be configured in a similar manner with the illustrated structures (or similar structures) of the exemplary wireless device 1042 of FIG. 6. The wireless device 1042 may also include other components, modules or structures which are well-known, but for clarity, only the components, modules or structures needed to describe the features of the present disclosure are described herein.
As those skilled in the art will appreciate, the above-described modules 602 and 604 of the wireless device 1042 may be implemented separately as suitable dedicated circuits. Further, the modules 602 and 604 can also be implemented using any number of dedicated circuits through functional combination or separation. In some embodiments, the modules 602 and 604 may be even combined in a single application specific integrated circuit (ASIC). As an alternative software-based implementation, the wireless device 1042 may comprise a memory 1202, a processor 1182 (including but not limited to a microprocessor, a microcontroller or a Digital Signal Processor (DSP), etc.) and a transceiver 1102. The memory 1202 stores machine-readable program code executable by the processor 1182 to cause the wireless device 1042 to perform the steps of the above-described method 500. It should be appreciated that the other wireless devices 1041, 1043 . . . 104n can also be configured in a similar manner as the wireless device 1042 to perform method 500.
In view of the foregoing, one skilled in the art will readily appreciate that the aforementioned techniques of the present disclosure are a marked improvement over the prior art in that the disclosed techniques result in a faster and much more paging bandwidth-efficient process for indicating a network restart event to multiple wireless devices when compared to the existing mechanism where the traditional RAN node individually informed each wireless device of a network restart event using the IMSI-based paging technique. Furthermore, the present disclosure, by introducing techniques to signal to wireless device(s) operating in eDRX mode that a core network restart has taken place as well as providing a means for the wireless device(s) to know for how long this signaling will be enabled, provides the following advantages:

    
    
        The core network is provided with tools to effectively recover from a network error.
        The battery life time of the wireless device(s) is enhanced since the wireless device(s) will not need to re-register more than once for the duration of a network restart event.
        NAS signaling is reduced since the wireless devices do not need to re-register more than once for the duration of a network restart event.
        The new techniques enable the wireless devices that need to perform the RAU procedure (re-registration procedure) to be informed of this without having to reduce the paging capacity through the use of IMSI-based pages. For example, wireless devices that make use of eDRX cycles (e.g., 5 minutes) will wake up according to their nominal paging groups and, at this point, an alternate means of informing them of the need to perform the RAU procedure (re-registration procedure) can be used as described in the present disclosure without having to reduce the paging capacity through the use of IMSI-based pages.
        It is to be noted that due to the use of blind repetitions for wireless devices in extended coverage, the use of the legacy IMSI-based method for informing wireless devices of the need to perform the RAU procedure will become even more expensive from a paging capacity reduction perspective (e.g., up to 32 paging blocks may be needed to convey a single IMSI-based page). In this regard, the techniques of the present disclosure are a marked-improvement when compared to the prior art.
    
    


Those skilled in the art will appreciate that the use of the term “exemplary” is used herein to mean “illustrative,” or “serving as an example,” and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms “first” and “second,” and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term “step,” as used herein, is meant to be synonymous with “operation” or “action.” Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.
Of course, the present disclosure may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. One or more of the specific processes discussed above may be carried out in a cellular phone or other communications transceiver comprising one or more appropriately configured processing circuits, which may in some embodiments be embodied in one or more application-specific integrated circuits (ASICs). In some embodiments, these processing circuits may comprise one or more microprocessors, microcontrollers, and/or digital signal processors programmed with appropriate software and/or firmware to carry out one or more of the operations described above, or variants thereof. In some embodiments, these processing circuits may comprise customized hardware to carry out one or more of the functions described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Although multiple embodiments of the present disclosure have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications and substitutions without departing from the present disclosure that as has been set forth and defined within the following claims.

## Claims

1. A radio access network node configured to interact with a plurality of wireless devices, the radio access network node comprising:
a processor; and,
a memory that stores processor-executable instructions, wherein the processor interfaces with the memory to execute the processor-executable instructions, whereby the radio access network node is operable to:
determine that a network restart has occurred in a core network node in a pool of core network nodes;
signal, to the wireless devices, an indication that the network restart has occurred, wherein the signal operation further comprises:
transmit, to the wireless devices, Extended Coverage Synchronization Channel (EC-SCH) content where one or more of six spare bits therein are used to indicate that the network restart has occurred; and

receive, from at least one of the wireless devices, a re-registration message in response to the signaling of the indication that the network restart has occurred.

2. The radio access network node of claim 1, wherein the indication further identifies at least one of the following:
the core network node in which the network restart has occurred;
a longest used paging cycle in a cell to indicate to the wireless devices that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and
a System Information (SI) version or a SI vintage counter.

3. The radio access network node of claim 1, wherein the radio access network node is operable to signal the indication by mapping a message including the indication onto a channel, which each of the wireless devices periodically wakes up to monitor prior to attempting to receive a paging message.

4. The radio access network node of claim 1, wherein the radio access network node is operable to signal the indication by mapping a message including the indication onto a channel, which is periodically monitored by each of the wireless devices while in idle mode.

5. The radio access network node of claim 1, wherein the radio access network node is operable to signal the indication by ‘in-band’ signaling that includes signaling the indication in conjunction with a transfer of a message without changing a content of the message.

6. The radio access network node of claim 5, wherein the ‘in-band’ signaling includes overlaying at least one channel which is periodically monitored by each of the wireless devices with a supplemental information channel that signals the indication by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern.

7. The radio access network node of claim 1, wherein the signal operation further comprises: transmit, to the wireless devices, one or more System Information (SI) messages to identify the core network node that has restarted.

8. A method in a radio access network node configured to interact with a plurality of wireless devices, the method comprising:
determining that a network restart has occurred in a core network node in a pool of core network nodes;
signaling, to the wireless devices, an indication that the network restart has occurred, wherein the signaling step further comprises:
transmitting, to the wireless devices, Extended Coverage Synchronization Channel (EC-SCH) content where one or more of six spare bits therein are used to indicate that the network restart has occurred; and

receiving, from at least one of the wireless devices, a re-registration message in response to the signaling of the indication that the network restart has occurred.

9. The method of claim 8, wherein the indication further identifies at least one of the following:
the core network node in which the network restart has occurred;
a longest used paging cycle in a cell to indicate to the wireless devices that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and
a System Information (SI) version or a SI vintage counter.

10. The method of claim 8, wherein the signaling step further comprises mapping a message including the indication onto a channel, which each of the wireless devices periodically wakes up to monitor prior to attempting to receive a paging message.

11. The method of claim 8, wherein the signaling step further comprises mapping a message including the indication onto a channel, which is periodically monitored by each of the wireless devices while in idle mode.

12. The method of claim 8, wherein the signaling step further comprises ‘in-band’ signaling that includes signaling the indication in conjunction with a transfer of a message without changing a content of the message.

13. The method of claim 12, wherein the ‘in-band’ signaling includes overlaying at least one channel which is periodically monitored by each of the wireless devices with a supplemental information channel that signals the indication by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern.

14. The method of claim 8, wherein the signaling step further comprises: transmitting, to the wireless devices, one or more System Information (SI) messages to identify the core network node that has restarted.

15. A wireless device configured to interact with a radio access network node, the wireless device comprising:
a processor; and,
a memory that stores processor-executable instructions, wherein the processor interfaces with the memory to execute the processor-executable instructions, whereby the wireless device is operable to:
receive, from the radio access network node, an indication that a network restart has occurred in a core network node in a pool of core network nodes, wherein the receive operation further comprises:
receive, from the radio access network node, Extended Coverage Synchronization Channel (EC-SCH) content where one or more of six spare bits therein are used to indicate that the network restart has occurred; and

determine that the network restart has occurred; and
transmit, to the radio access network node, a re-registration message in response to the determination that the network restart has occurred.

16. The wireless device of claim 15, wherein the indication further identifies at least one of the following:
the core network node in which the network restart has occurred;
a longest used paging cycle in a cell to indicate to the wireless device that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and
a System Information (SI) version or a SI vintage counter.

17. The wireless device of claim 15, wherein the wireless device is operable to receive the indication included in a message mapped onto a channel, which the wireless device periodically wakes up to monitor prior to attempting to receive a paging message.

18. The wireless device of claim 15, wherein the wireless device is operable to receive the indication included in a message mapped onto a channel, which is periodically monitored by the wireless device while in idle mode.

19. The wireless device of claim 15, wherein the wireless device is operable to receive the indication via ‘in-band’ signaling which includes receiving the indication in conjunction with receiving a message where a content of the message does not include the indication.

20. The wireless device of claim 19, wherein the wireless device is operable to obtain the indication from a supplemental information channel that overlays at least one channel periodically monitored by the wireless device, wherein the supplemental information channel signals the indication by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern.

21. The wireless device of claim 15, wherein the receive operation further comprises: receive, from the radio access network node, one or more System Information (SI) messages to identify the core network node that has restarted.

22. A method in a wireless device configured to interact with a radio access network node, the method comprising:
receiving, from the radio access network node, an indication that a network restart has occurred in a core network node in a pool of core network nodes, wherein the receiving step further comprises:
receiving, from the radio access network node, Extended Coverage Synchronization Channel (EC-SCH) content where one or more of six spare bits therein are used to indicate that the network restart has occurred; and

determining that the network restart has occurred; and
transmitting, to the radio access network node, a re-registration message in response to the determination that the network restart has occurred.

23. The method of claim 22, wherein the indication further identifies at least one of the following:
the core network node in which the network restart has occurred;
a longest used paging cycle in a cell to indicate to the wireless device that a re-registration is not required every time that an indication that a network restart has occurred is signaled during a time period spanned by the longest used paging cycle; and
a System Information (SI) version or a SI vintage counter.

24. The method of claim 22, wherein the receiving step further comprises receiving the indication included in a message mapped onto a channel, which the wireless device periodically wakes up to monitor prior to attempting to receive a paging message.

25. The method of claim 22, wherein the receiving step further comprises receiving the indication included in a message mapped onto a channel, which is periodically monitored by the wireless device while in idle mode.

26. The method of claim 22, wherein the receiving step further comprises receiving the indication via ‘in-band’ signaling which includes receiving the indication in conjunction with receiving a message where a content of the message does not include the indication.

27. The method of claim 26, wherein the wireless device obtains the indication from a supplemental information channel that overlays at least one channel periodically monitored by the wireless device, wherein the supplemental information channel signals the indication by (1) using a different modulation symbol rotation or modulation index, or (2) using a bit-wise modulo 2 operation with a known bit pattern.

28. The method of claim 22, wherein the receiving step further comprises: receiving, from the radio access network node, one or more System Information (SI) messages to identify the core network node that has restarted.