WO2019149370A1

WO2019149370A1 - A mobility management entity database to support emergency cell broadcast

Info

Publication number: WO2019149370A1
Application number: PCT/EP2018/052673
Authority: WO
Inventors: Rajesh Babu NATARAJAN; Paromita CHINTAN SHAH
Original assignee: Nokia Technologies Oy
Priority date: 2018-02-02
Filing date: 2018-02-02
Publication date: 2019-08-08

Abstract

A mobility management entity (MME) adds a location of a small cell to a database stored in the MME in response to the MME receiving a registration message from the small cell including the location. The MME receives an emergency alert message including location information for a region affected by an emergency. The MME selects the small cell by comparing the location information for the region and the location included in the database. The MME transmits the emergency alert message to the small cell. A cell broadcasting center (CBC) receives an emergency alert that identifies a region affected by the emergency alert. The CBC maps the emergency alert to one or more mobility management entity (MMEs) serving the region. The CBC transmits an emergency alert message including location information that identifies the region to the MMEs.

Description

A MOBILITY MANAGEMENT ENTITY DATABASE TO SUPPORT EMERGENCY

CELL BROADCAST

BACKGROUND

[0001] Wireless communication systems are used to provide public safety notices and notifications of emergencies such as man-made or natural disasters. For example, a cell broadcasting center (CBC) is able to broadcast commercial mobile alert system (CMAS) messages such as wireless emergency alerts (WEA) to the user equipment in areas affected by the emergency. The CBC maintains a database of locations of base stations and small cells. The locations stored in the CBC database are provisioned to the CBC by an operator of the wireless communication system. In order to convey an alert to the appropriate user equipment, the CBC transmits a message that identifies one or more base stations or small cells that are to be notified of the alert, as indicated by the database of locations. In some cases, the message is a WRITE-REPLACE -REQUEST message ( e.g ., as defined in 3GPP TS 29T68-eOO, section 4.3.3.2) that includes an information element indicating a tracking area that overlaps with the affected area. A mobility management entity (MME) receives the message and forwards the message to the base stations or small cells in the tracking area. In other cases, the message is a WRITE-REPLACE- REQUEST message that includes a list of information elements that identify the base stations or small cells that provide service to the area affected by the emergency. The CBC transmits the alert message to one or more MMEs that serve the base stations or the small cells in the list. The information elements include global identifiers such as a Global eNB ID information element. The MME forwards the alert message to the base stations or small cells that are indicated in the list. The base stations or small cells then broadcast the alert message to the user equipment served by the base stations or the small cells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items.

[0003] FIG. 1 is a block diagram of a first example of a wireless communication system that is configured to provide emergency alert messages according to some embodiments.

[0004] FIG. 2 is a block diagram of a second example of a wireless communication system that is configured to provide emergency alert messages according to some embodiments.

[0005] FIG. 3 is a flow diagram of a method of adding location information for a small cell to a database in an MME according to some embodiments.

[0006] FIG. 4 is a flow diagram of a method of removing location information for a small cell to a database in an MME according to some embodiments.

[0007] FIG. 5 is a flow diagram of a method of forwarding an alert message to small cells in a region affected by an emergency according to some embodiments.

[0008] FIG. 6 is a block diagram of a communication system that supports broadcast of emergency alert messages to regions of arbitrary size according to some embodiments.

DETAILED DESCRIPTION

[0009] There are a number of drawbacks to the conventional techniques for broadcasting emergency alerts to user equipment. For example, the database of base stations and small cells maintained by the CBC is not dynamic and only changes in response to updates that are provided by the operator. The operator updates are typically provided at

predetermined intervals and not necessarily in response to a base station or small cell registering or de-registering from the system. The CBC database is therefore likely to be out-of-date, which results in the list of base stations or small cells transmitted by the CBC with an alert message including base stations or small cells that are no longer registered with the system and not including base stations or small cells that have registered with the system since the last operator update. This is a particular problem for small cells, which are typically more numerous and change registration and location status more frequently than base stations. Furthermore, the high density of small cells increases the overhead incurred by transmitting a list of small cells from the CBC to the MME.

[0010] The combination of these two drawbacks makes the conventional alerting system less than optimal in many important use cases. For example, if an emergency occurs in an area that is much smaller than a tracking area and includes a high density of small cells, such as a football stadium or concert arena, the two broadcast options available to the emergency alert system both have undesirable consequences. First, broadcasting alerts to all base stations and small cells within a tracking area that includes the football stadium or concert arena will unnecessarily alert numerous users outside of the affected area, potentially causing a widespread panic. Second, transmitting a list including all of the small cells within the affected area will incur a significant amount of overhead, which can strain or compromise the system, potentially delaying or interrupting broadcast of the alert messages to some or all of the users in the affected area.

[0011] FIGs. 1-6 illustrate a low overhead technique of providing emergency alert messages to a dynamically changing list of small cells. The technique includes identifying a location of a small cell based on location information included in a registration message used to register the small cell with a mobility management entity (MME). A location database maintained by the MME is updated to include the location of the small cell based on the location information in the registration message. Some embodiments of the small cells determine their location coordinates using Global Positioning System (GPS) signals or Global Navigation Satellite System (GNSS) signals. The small cells include the location coordinates in the registration message transmitted to the MME. Some embodiments of the registration message include other location information (in addition to or instead of the location coordinates) including altitude, direction, latitude, longitude, or one or more radii of an ellipsoid around the location coordinates. Location information for a small cell is removed from the location database in response to receiving a de -registration message from the small cell.

[0012] A cell broadcasting center (CBC) receives emergency alerts and generates emergency alert messages for transmission to the MME. The message received by the CBC includes information that delineates or otherwise identifies a region affected by the emergency. The CBC maps the affected region to the MME. In some cases, the affected region is smaller than tracking areas that include multiple base stations or small cells served by the MME. The CBC transmits location information for the affected region to the MME. Some embodiments of the emergency alert message include an ellipsoid point and one or more radii that define an ellipsoid that encompasses the affected region. The emergency alert message can also include other information that defines the affected region, such as map coordinates, location identifiers, and the like. In response to receiving an emergency alert message including information indicating an affected region, the MME identifies small cells or base stations that provide service in the affected region based on the locations of small cells indicated in the location database. The MME then forwards the emergency alert to the small cells that provide service in the affected region. Some embodiments of the MME are able to identify a location of the user equipment that initiates an emergency call from a small cell based on the location information for the small cell stored in the location database. The location of the user equipment can be used to identify or modify a boundary of the affected region associated with an emergency alert.

[0013] FIG. 1 is a block diagram of a first example of a wireless communication system 100 that is configured to provide emergency alert messages according to some embodiments. The wireless communication system 100 includes a cellular network 105 that provides wireless connectivity to one or more user equipment 110. The cellular network 105 includes an Internet Protocol (IP) Multimedia Subsystem (IMS) 1 15 that provide an architectural framework for delivering IP multimedia services. The IMS 1 15 is connected to a core network 120 within the cellular network 105. The core network 120 includes a mobility management entity (MME) 125 and a cell broadcasting center (CBC) 130. Some embodiments of the core network 120 also include other entities such as a home subscriber server, one or more call session control functions, a subscriber location function, and the like, which are not shown in FIG. 1 in the interest of clarity.

[0014] Some embodiments of the MME 125 implement an Sl-MME stack to support a corresponding interface with base stations or small cells and an Sl 1 stack to support a corresponding interface with a serving gateway such as the gateway 135. The stacks in the MME 125 support a Stream Control Transmission Protocol (SCTP) that uses IP services to provide a reliable datagram delivery service. The stacks in the MME 125 also support an Sl Application Part (S1AP) protocol to support a signaling service that is used to manage bearers, perform context transfers, support mobility functions for the user equipment 110, page the user equipment 1 10, support nonaccess stratum (NAS) signaling, and the like.

[0015] Some embodiments of the CBC 130 are configured to transmit cell broadcast messages that are received from information providers. The CBC 130 is able to modify the messages, as well as add or modify control data for the messages such as a specified area for the broadcast, a transmission period, a transmission repetition frequency, and the like. The CBC 130 transmits the broadcast messages to the MME 125, which is able to forward the broadcast messages to one or more base stations or small cells such as the small cell 140 via the gateway 135. Some embodiments of the small cell 140 are able to determine their location coordinates using Global Positioning System (GPS) signals or Global Navigation Satellite System (GNSS) signals.

[0016] As used herein, the term“base station” refers to a device that provides wireless connectivity to user equipment 110 within a corresponding geographic area or cell. A base station is typically owned by a service provider and is deployed in a fixed location, e.g., on a cell tower or building. As used herein, the term“small cell” refers to a device that provides wireless connectivity within a corresponding geographic area (also referred to as a small cell) that is typically smaller than the cells that are served by base stations. Small cells also overlap with the cells that are served by base stations. Small cells are typically owned by organizations or individuals and are used to provide connectivity within smaller geographic areas associated with the organization or individual. Small cells are also referred to as home base stations, home eNodeBs, metrocells, picocells, femtocells, and the like. Small cells transmit registration messages to register with the wireless communication system 100 so that the small cell can provide wireless connectivity to the user equipment 1 10. Small cells transmit de-registration messages to de -register when they are no longer being used to provide wireless connectivity. [0017] The wireless communication system 100 supports broadcast of emergency alert messages to alert user equipment 110 in the event of an emergency that affects an area that includes the user equipment 110. The emergency alert messages originate in an information provider such as a Federal Emergency Operation Center (EOC) 145, a state EOC 150, an E91 1 response center 155, or other entities. The alert messages are provided to an alert gateway 160 that gathers, aggregates, or consolidates alert messages and provides the alert messages to a control broadcast entity (CBE)/commercial mobile service provider (CMSP) gateway 165 in the cellular network 105. In some

embodiments, messages are exchanged between the gateways 160, 165 according to the common alerting protocol (CAP), which is an XML-based data format for exchanging public warnings and emergencies between alerting technologies. For example, the alert gateway 160 can transmit commercial mobile alert system (CMAS) messages such as wireless emergency alerts (WEA) to the CBE/CMSP gateway 165.

[0018] The MME 125 maintains a database of entries that include identifiers of small cells associated with the MME 125 (such as the small cell 140) and information that indicates locations of the small cells. In some embodiments, the location information includes geographical coordinates. The location information can also include other information (in addition to or instead of the geographical coordinates) such as an altitude, a direction, a latitude, longitude, or one or more radii of an ellipsoid around an ellipsoid point defined by the location coordinates. As discussed above, small cells determine their location using GNSS or GPS signals. The small cells transmit the location information to the MME 125 in the registration messages that are used to register the small cell to provide wireless connectivity in the wireless communication system 100. The MME 125 uses this information to populate the database. The small cells are also able to transmit de-registration messages that are used to de-register the small cell when the small cell is no longer providing wireless connectivity. The MME 125 uses this information to remove entries associated with the small cell from the database. Thus, the database is dynamically updated and includes the most accurate record of the currently active small cells in the wireless communication system 100. [0019] Since the MME 125 maintains the database including location information for the small cells, the CBC 130 is not required to transmit a list of small cells that are to broadcast emergency alert messages within a region affected by an emergency. Instead, the CBC 130 maps emergency alerts received from the CBE/CMSP gateway 165 to one or more MMEs (including the MME 125) that serve base stations or small cells (such as the small cell 140) that provide service in the affected region. The CBC 130 forward the emergency alert message to the MME 125. The emergency alert message includes location information that identifies the region affected by the emergency. In some embodiments, the location information includes geographical coordinates of an ellipsoid point and one or more radii that define an ellipsoid that encompasses the affected region. The MME 125 selects one or more small cells (including the small cell 140) by comparing the location information for the affected region and the small cell locations included in the database. The MME 125 transmits the emergency alert message to the small cells that provide wireless connectivity in the affected region. Thus, emergency alert messages are provided to small cells within affected regions of any size, including regions that are smaller than tracking areas associated with the MME 125.

[0020] FIG. 2 is a block diagram of a second example of a wireless communication system 200 that is configured to provide emergency alert messages according to some embodiments. The wireless communication system 200 includes a CBC 205 that is used to implement some embodiments of the CBC 130 shown in FIG. 1. The wireless communication system 200 also includes an MME 210 that is used to implement some embodiments of the MME 125 shown in FIG. 1. The MME 210 serves a set of small cells 21 1, 212, 213, 214, 215 (collectively referred to herein as“the small cells 211-215”) that provide wireless connectivity to user equipment 220, 221, 222, 223, 224, 225, 226, which are collectively referred to herein as“the user equipment 220-226.” Some embodiments of the MME 210 also serve one or more base stations (not shown in FIG. 2 in the interest of clarity).

[0021 ] The small cells 211 -215 are deployed within a tracking area 230. As used herein, the term“tracking area” refers to a set of base stations or small cells that are grouped together to optimize signaling. For example, the MME 210 transmits paging messages via the small cells 211-215 (and any other base stations within the tracking area 230) in response to receiving a message for an idle user equipment that may be located within the tracking area 230. The MME 210 maintains lists of tracking areas, which are configured on the user equipment 220-226. Tracking area updates are performed periodically or in response to one of the user equipment 220-226 roaming into a tracking area that is not included in its list of tracking areas. In some cases, tracking areas are also referred to as location areas or routing areas.

[0022] The CBC 205 forwards emergency alert messages to the MME 210. The emergency alert messages include location information that identifies a region 235 that is affected by the emergency indicated in the emergency alert message. Some embodiments of the location information include coordinates of an ellipsoid point and one or more radii that define an ellipsoid that encompasses the region 235. However, other types of location information are used to identify boundaries of the region 235 in some embodiments. For example, map coordinates or other location identifiers such as place names, street names, or other identifiers associated with the region 235 can also be included in the location information. The MME 210 uses the location information that identifies the region 235 to select a subset of the small cells 211-215 that are to receive the emergency alert message. In the illustrated embodiment, the MME 210 compares locations of the user equipment 220-226 and the location information that identifies the region 235. Based on the comparison, the MME 210 determines that the small cells 21 1, 212 are providing coverage within the region 235. The MME therefore forwards the emergency alert message to the small cells 211 , 212. In some embodiments, the coverage areas of the small cells 211, 212 are not completely enclosed within the boundaries of the region 235 and some portions of the coverage areas ofthe small cells 21 1, 212 extend beyond the boundaries of the region 235.

[0023] Some embodiments of the MME 210 are configured to modify boundaries of the region 235 in response to signaling received from one or more ofthe user equipment 220- 226. For example, the MME 210 identifies locations ofthe user equipment 222, 223 in response to the small cell 213 receiving messages from the user equipment 222, 223 that indicate that the emergency is affecting a region outside of the region 235. The MME 210 then extends the boundary of the region 235 to encompass the small cell 213 and the user equipment 222, 223 in response to receiving the messages from the user equipment 222, 223. The MME 210 is also able to reduce the size of the region 235 in response to receiving messages from one or more of the user equipment 220, 221 indicating that the user equipment 220, 221 are not affected by the emergency.

[0024] FIG. 3 is a flow diagram of a method 300 of adding location information for a small cell to a database in an MME according to some embodiments. The method 300 is implemented in some embodiments of the wireless communication system 100 shown in FIG. 1 and the wireless communication system 200 shown in FIG. 2. For example, some portions of the method 500 are implemented in some embodiments of the small cell 140 shown in FIG. 1 and the small cells 211 -215 shown in FIG. 2. Other portions of the method 500 are implemented in an MME such as some embodiments of the MME 125 shown in FIG. 1 and the MME 210 shown in FIG. 2.

[0025] At block 305, a small cell determines its location. Some embodiments of the small cell determine their locations using GNSS or GPS signals received by the small cell from a corresponding satellite network. At block 310, the small cell transmits a registration message to the MME to register the small cell to provide wireless

connectivity within a wireless communication system. The registration message includes information identifying the location of the small cell. At block 315, the MME adds an identifier of the small cell and the location information to the database.

[0026] In some embodiments of the method 300, the registration message transmitted from the small cell to the MME includes an information element for providing the location information. For example, the message can include a small cell Focation

Information parameter used by a small cell (which is sometimes referred to as an HeNB) in an Sl AP Sl Setup Request message towards MME:

[0027] Some embodiments of the information element include information identifying a geographical location. For example, the following information element identifies an ellipsoid point with altitude (as in 3GPP TS 23.032).

[0028] For another example, the following information element contains the geographical coordinates of an ellipsoid point.

[0029] For yet another example, the following information element contains the altitude and direction of an ellipsoid point.

[0030] In some embodiments, the small cell location information element is defined for home base stations ( e.g ., small cells) and used in a home base station Registration Request message as defined in 3GPP TS 25.469vl4.0.0. However, corresponding parameters for home evolved node base stations (HeNBs, which are referred to as small cells in 4G technology) are not defined in the current specifications. The format and definition of the geographical location and all its sub-parameters are derived from the corresponding base station location information->Geographical location parameter, so that the same format can be universally followed for base stations and small cells.

[0031] In some embodiments, the small cell location information element parameter is defined as an optional parameter in the S1AP Sl Setup Request message, so that the small cell location information is stored at the MME during registration of the small cell. For example, the small cell transmits an Sl Setup Request (as per 3GPP specification TS 36.413) that is referred to as Sl SETUP REQUEST. This message is sent by the small cell to transfer information for a TNL association. The direction of the messages from the base station to the MME. An example of the Sl setup request message is provided in the following tables.

[0032] FIG. 4 is a flow diagram of a method 400 of removing location information for a small cell to a database in an MME according to some embodiments. The method 400 is implemented in some embodiments of the wireless communication system 100 shown in FIG. 1 and the wireless communication system 200 shown in FIG. 2. For example, the method 400 is implemented in an MME such as some embodiments of the MME 125 shown in FIG. 1 and the MME 210 shown in FIG. 2.

[0033] At block 405, the MME determines that the small cell is no longer in service. In some cases, the MME determines that the small cell is not in service by detecting that an Sl link associated with the small cell has gone down, e.g. using the SCTP transport layer protocol. At block 410, the MME removes an entry from the database that includes the identifier of the small cell and the location information for the small cell in response to determining that the small cell is no longer in service. In some embodiments, the MME updates the entry in the database in response to the same small cell registering from a different location.

[0034] FIG. 5 is a flow diagram of a method 500 of forwarding an alert message to small cells in a region affected by an emergency according to some embodiments. The method 500 is implemented in some embodiments of the wireless communication system 100 shown in FIG. 1 and the wireless communication system 200 shown in FIG. 2. For example, portions of the method 500 are implemented in a CBC such as the CBC 130 shown in FIG. 1 and the CBC 205 shown in FIG. 2. Other portions of the method 500 are implemented in an MME such as some embodiments of the MME 125 shown in FIG. 1 and the MME 210 shown in FIG. 2.

[0035] At block 505, the CBC receives an emergency alert message such as an emergency alert message that is provided by the Federal EOC 145, the State EOC 150, or the E911 Response Center 155 shown in FIG. 1. The emergency alert message indicates a region that is affected by the emergency. At block 510, the CBC forwards the emergency alert message or another emergency alert message that includes information in the originally received emergency alert message in a different format, potentially in combination with other information. The emergency alert message transmitted by the CBC includes information identifying the affected region. In some embodiments, the location information includes geographical coordinates of an ellipsoid point and one or more radii that define an ellipsoid around an ellipsoid point. The parameters that define the ellipsoid are selected so that the ellipsoid encompasses the affected region.

[0036] At block 515, the MME receives the emergency alert message from the CBC and uses the location information in the emergency alert message to identify small cells that provide service in coverage areas that overlap (at least partially) with the affected region. The MME identifies the small cells associated with the affected region by comparing the location information in the emergency alert message with locations of the small cells indicated in a database stored by the MME. Some embodiments of the database are maintained in accordance with the method 300 shown in FIG. 3 and the method 400 shown in FIG. 4. At block 520, the MME forwards an alert message to the small cells associated with the affected region.

[0037] Some embodiments of a CBC that implements the method 500 transmit an emergency alert message that includes location information in an information element such as a Location Range information parameter included in a SBc-AP message that is transmitted towards the MME. One example of the location range parameter is as follows:

The radius information element is defined as:

[0038] The location range information defines an ellipsoid point and a radius to define an area that is affected by the emergency. The MME uses this area as a reference and selects all the small cells and base stations serving in this area boundary. The MME can then broadcast emergency alert messages such as CMAS messages to the selected small cells. For example, the 3GPP TS 23.032 defines the“Ellipsoid Point with uncertainty Circle” in section 5.2 and its encoding is defined in the same document in the section 7.3.2. This definition and the parameter is used in Diameter message AVP and defined in 3GPP TS 29.172, but no equivalent parameter and its usage exists in S1AP or SBc-AP protocol messages. In some embodiments, equivalent parameters are implemented on the SBc-AP interface between the CBC and the MME, as discussed above.

[0039] Some embodiments of the small cell location range parameter are implemented as an optional parameter in an alert message that is transmitted over the interface between the CBC and the MME, such as an SBc-AP Write-Replace Warning message. The MME therefore uses this information to broadcast the small cells that provide service within the specified location area boundary. For example, the message transmitted from the CBC to the MME can include an SBc-AP: WRITE-REPLACE WARNING message defined according to 3GPP TS 29. l68vl 4.0.0. This message is sent by the CBC to request start or overwrite of a warning message broadcast. An example of the message is shown in the following tables.

[0040] FIG. 6 is a block diagram of a communication system 600 that supports broadcast of emergency alert messages to regions of arbitrary size according to some embodiments. The communication system 600 includes an CBC 605 that is used to implement some embodiments of the CBC 130 shown in FIG. 1 and the CBC 205 shown in FIG. 2. The communication system 600 also includes an MME 610 that is used to implement some embodiments of the MME 125 shown in FIG. 1 and the MME 210 shown in FIG. 2.

[0041] The CBC 605 includes a transceiver 615 that is used to support communication over an interface 628 with the MME 610. The interface 628 is used to implement some embodiments of an SBc interface that supports the SBc-AP protocol, as discussed herein. Some embodiments of the transceiver 615 are implemented using one or more receivers and one or more transmitters. The CBC 605 also includes a processor 620 and a memory 625. The processor 620 is configured to execute instructions such as instructions stored in the memory 625 and the memory 625 is configured to store instructions, data that is to be operated upon by the instructions, or the results of instructions performed by the processor 620. The CBC 605 is therefore able to implement some embodiments of the method 500 shown in FIG. 5.

[0042] The MME 610 includes a transceiver 630 that is used to support communication over the interface 628 with the CBC 605. Some embodiments of the transceiver 630 are implemented using one or more receivers and one or more transmitters. The transceiver 630 is configured to broadcast emergency alert messages to selected small cells 636, 637, 638. The MME 610 also includes a processor 635 and a memory 640. The processor 635 is configured to execute instructions such as instructions stored in the memory 640 and the memory 640 is configured to store instructions, data that is to be operated upon by the instructions, or the results of instructions performed by the processor 635. The memory 640 is used to implement a database 645 that stores entries including identifiers of small cells and location information that indicates locations of the small cells. The MME 610 is therefore able to implement some embodiments of the method 300 shown in FIG. 3, the method 400 shown in FIG. 4, and the method 500 shown in FIG. 5.

[0043] As discussed herein, some embodiments of a communication system make use of location information derived using GNSS/GPS receiver or chip that is implemented in the small cells. The location information is used to selectively provide messages to small cells within regions affected by an emergency. The GNSS encompasses all global satellite positioning systems, which include constellations of satellites orbiting over the earth's surface and continuously transmitting signals that enable small cells to determine their position. Due to the relatively small coverage areas of small cells, the GNSS receiver or chip in the small cell also provides an accurate estimate of the position of the user equipment being served by the small cell. This information is very useful during lawful interception user tracking and during any user initiated emergency call for the emergency response centre to dispatch rescue team to the accurate location. Some embodiments of the techniques disclosed herein are therefore implemented in conjunction with a public warning system (PWS) or CMAS, which is also known as WEA (Wireless Emergency Alert) in CBS.

[0044] In an emergency situation, the CMAS or WEA CBE needs to provide a broadcast alert message to a region affected by the emergency. The CMAS or CBE therefore provides the information to a CBC. As discussed herein, the locations of small cells are stored in a database at the MME. Consequently, instead of sending a complete list of all the small cells in the region affected by the emergency, the CBC only specifies a location area boundary or range to the MME, e.g., using GPS coordinates of an area boundary or range. The MME identifies the small cells in the affected region using the location information included in the message received from the CBC and then broadcasts and emergency alert to the appropriate small cells. This approach allows emergency alert messages to be broadcast to the most up-to-date listing of the small cells in the affected region. Transmitting information defining the region instead of a list of small cells also reduces the overhead for transmissions between the CBC and the MME.

[0045] Another important advantage or use case is when any user initiates an emergency call from a small cell, e.g., according to the standards set forth in 3GPP TS 23.271 , section 9.1.17. In that case, the MME does not necessarily need to calculate a position of the user equipment with the help of information provided by an Evolved Serving Mobile Location Center (E-SMLC), which allows the system to avoid the related messaging overhead. The MME is also able to directly update the SMLC with the locations of the small cells (e.g., by transmitting a subscriber LCS_report message) since the accuracy of the estimate of the user equipment’s location is within lO-meter range. The location infonnation is then sent to a PSAP or E91 1 emergency response center. This approach to determining the location of the user equipment avoids the complex algorithms that are conventionally used to derive the location of the user equipment. Related messaging overhead is also reduced, thus making the call flow more efficient, without compromising on the accuracy of the estimated location of the user equipment.

[0046] In some embodiments, certain aspects of the techniques described above may implemented by one or more processors of a processing system executing software. The software comprises one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer readable storage medium. The software can include the instructions and certain data that, when executed by the one or more processors, manipulate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer readable storage medium can include, for example, a magnetic or optical disk storage device, solid state storage devices such as Flash memory, a cache, random access memory (RAM) or other non-volatile memory device or devices, and the like. The executable instructions stored on the non- transitory computer readable storage medium may be in source code, assembly language code, object code, or other instruction format that is interpreted or otherwise executable by one or more processors.

[0047] A computer readable storage medium may include any storage medium, or combination of storage media, accessible by a computer system during use to provide instructions and/or data to the computer system. Such storage media can include, but is not limited to, optical media (e.g., compact disc (CD), digital versatile disc (DVD), Blu- Ray disc), magnetic media (e.g., floppy disc, magnetic tape, or magnetic hard drive), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or Flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer readable storage medium may be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., a magnetic hard drive), removably attached to the computing system (e.g., an optical disc or FTniversal Serial Bus (FTSB)-based Flash memory), or coupled to the computer system via a wired or wireless network (e.g., network accessible storage (NAS)).

[0048] Note that not all of the activities or elements described above in the general description are required, that a portion of a specific activity or device may not be required, and that one or more further activities may be performed, or elements included, in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed. Also, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0049] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. Moreover, the particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

adding a location of a small cell to a database stored in a mobility management entity (MME) in response to the MME receiving a registration message from the small cell including the location;

receiving, at the MME, an emergency alert message including location

information for a region affected by an emergency;

selecting, at the MME, the small cell by comparing the location information for the region and the location included in the database; and

transmitting the emergency alert message from the MME to the small cell.

2. The method of claim 1 , further comprising:

receiving the registration message from the small cell including location

coordinates of the small cell.

3. The method of claim 2, wherein receiving the registration message including the location coordinates comprises receiving a registration message including at least one of an altitude, a direction, a latitude, longitude, or one or more radii of an ellipsoid around an ellipsoid point defined by the location coordinates.

4. The method of claim 1 , wherein receiving the emergency alert message including the location information comprises receiving an emergency alert message including an ellipsoid point and one or more radii that define an ellipsoid that encompasses the region.

5. The method of claim 4, wherein selecting the small cell comprises selecting the small cell in response to the location of the small cell being within the ellipsoid.

6. The method of claim 1, wherein receiving the emergency alert message including the location information comprises receiving an emergency alert message including at least one of a map coordinate or a location identifier associated with the region.

7. The method of claim 1, further comprising:

removing the location of the small cell from the database in response to receiving a de -registration message from the small cell.

8. The method of claim 1, further comprising:

identifying a location of a user equipment that initiates an emergency call from the small cell based on the location information stored in the database; and modifying a boundary of the region based on the location of the user equipment.

9. A method comprising:

receiving an emergency alert at a cell broadcasting center (CBC), wherein the emergency alert identifies a region affected by the emergency alert;

mapping, at the CBC, the emergency alert to at least one mobility management entity (MME) serving the region; and

transmitting, from the CBC to the at least one MME, an emergency alert message including location information that identifies the region.

10. The method of claim 9, wherein transmitting the emergency alert message including the location information comprises transmitting an emergency alert message including an ellipsoid point and one or more radii that define an ellipsoid that encompasses the region.

11. The method of claim 10, wherein the MME is configured to determine, in response to receiving the emergency alert message from the CBC, at least one location of at least one small cell based on a database stored in the MME, and wherein the MME is configured to select the at least one small cell in response to the at least one location being within the ellipsoid.

12. The method of claim 9, wherein transmitting the emergency alert message including the location information comprises transmitting an emergency alert message including at least one of a map coordinate or a location identifier associated with the region.

13. A mobility management entity (MME) comprising:

a memory configured to store a database of locations of small cells;

a transceiver configured to receive a registration message from a small cell

including a location of the small cell; and

a processor configured to add the location of the small cell to the database in response to receiving the registration message,

wherein the transceiver is configured to receive an emergency alert message including location information for a region affected by an emergency, wherein the processor is configured to select the small cell by comparing the location information for the region and the location included in the database, and

wherein the transceiver is configured to transmit the emergency alert message to the small cell.

14. The MME of claim 13, wherein the transceiver is configured to receive the registration message from the small cell including location coordinates of the small cell.

15. The MME of claim 14, wherein the transceiver is configured to receive a registration message including at least one of an altitude, a direction, a latitude, longitude, or one or more radii of an ellipsoid around an ellipsoid point defined by the location coordinates.

16. The MME of claim 13, wherein the transceiver is configured to receive an emergency alert message including an ellipsoid point and one or more radii that define an ellipsoid that encompasses the region.

17. The MME of claim 16, wherein the processor is configured to select the small cell in response to the location of the small cell being within the ellipsoid.

18. The MME of claim 13, wherein the transceiver is configured to receive an emergency alert message including at least one of a map coordinate or a location identifier associated with the region.

19. The MME of claim 13, wherein the processor is configured to remove the location of the small cell from the database in response to receiving a de -registration message from the small cell.

20. The MME of claim 13, wherein the processor is configured to:

identify a location of a user equipment that initiates an emergency call from the small cell based on the location information stored in the database; and modify a boundary of the region based on the location of the user equipment.

21. A cell broadcasting center (CBC) comprising:

a transceiver configured to receive an emergency alert that identifies a region affected by the emergency alert; and

a processor configured to map the emergency alert to at least one mobility

management entity (MME) serving the region,

wherein the transceiver is configured to transmit, to the at least one MME, an emergency alert message including location information that identifies the region.

22. The CBC of claim 21 , wherein the transceiver is configured to transmit the emergency alert message including an ellipsoid point and one or more radii that define an ellipsoid that encompasses the region.

23. The CBC of claim 22, wherein the MME is configured to determine, in response to receiving the emergency alert message from the CBC, at least one location of at least one small cell based on a database stored in the MME, and wherein the MME is configured to select the at least one small cell in response to the at least one location being within the ellipsoid.

24. The CBC of claim 21 , wherein the transceiver is configured to transmit the emergency alert message including at least one of a map coordinate or a location identifier associated with the region.