Backhaul link adaptive 5G emergency base station communication method and system

Abstract

The invention relates to the technical field of mobile communication and emergency communication, in particular to a backhaul link adaptive 5G emergency base station communication method and system, and an emergency base station continuously monitors the state of a backhaul link with a 5G core network; when the backhaul link is stable and available, the base station works in a standard access mode to provide a conventional access service; when it is detected that a return link is interrupted or the link quality is lower than a threshold value, the base station automatically switches to a local emergency mode, the service leading to the core network is stopped, and local emergency communication is organized through a local computing power unit; a base station broadcasts a local emergency mode indication, a public emergency ID list and emergency random access configuration through an extended system information block, and a terminal completes access registration according to a special leader sequence and obtains a local emergency communication ID. In the local emergency mode, the terminals can realize local exchange communication through the transfer of the emergency base station, or perform device-to-device direct connection communication under the coordination of the base station; and after the return link is recovered, the base station switches back to the standard access mode and notifies the terminal. According to the invention, minimum necessary communication can be guaranteed in an extreme scene, and the emergency communication reliability is improved.

Description

[Technical Field] This invention relates to the fields of mobile communication and emergency communication technology, and in particular to a 5G emergency base station communication method and system with adaptive backhaul links. [Background Technology] In scenarios such as natural disasters, public safety incidents, or damage to network infrastructure, fixed backhaul networks (such as fiber optics and microwave) may be interrupted, causing macro base stations that rely on traditional backhaul links to become paralyzed. At this time, emergency base stations with satellite and wireless self-backhaul capabilities (such as vehicle-mounted base stations and portable base stations) are rapidly deployed to restore network coverage.

[0001] However, existing emergency base station technology has significant shortcomings: 1. Strong backhaul dependency: Most emergency base station operating modes still assume that the backhaul link between the base station and the core network is stable and available. Once the quality of the backhaul link deteriorates or is completely interrupted (such as when the satellite link is affected by weather, the wireless self-backhaul distance is too far, or it is interfered with), even if the base station air interface is normal, user equipment will not be able to carry out any communication, including critical emergency communications.

[0002] 2. Lack of autonomous local communication capabilities: Current standards do not specify how a base station can autonomously organize point-to-point or local network communication among terminals within its coverage area when the emergency base station loses connection with the core network. Terminals cannot perceive changes in the base station's status, nor can they perform identification and paging without core network support.

[0003] Therefore, there is an urgent need for an intelligent and adaptive mechanism that enables emergency base stations to automatically switch to a degraded but usable local emergency mode when the backhaul link is unstable, ensuring minimal communication. [Summary of the Invention] To overcome the aforementioned problems, this invention proposes a 5G emergency base station communication method and system with adaptive backhaul link that can effectively solve these issues. The core idea is to incorporate a local computing unit into the emergency base station, enabling it to have dual-mode adaptive switching capability: when the backhaul link is available, it functions as a standard base station; when the backhaul link is unavailable, it automatically degrades to a local emergency communication coordinator, organizing local emergency communication for terminals within its coverage area.

[0004] The technical solution provided by this invention to solve the above-mentioned technical problems is: A 5G emergency base station communication method based on backhaul link state adaptation includes the following steps: Step 1: The emergency base station is powered on and starts up, attempting to establish or maintain a backhaul link connection with the 5G core network, and continuously monitoring the availability and stability of the backhaul link.

[0005] Step 2: When the backhaul link is stable and available, the emergency base station operates in standard access mode, serving as a standard gNB to provide communication services for user equipment within the coverage area to access the 5G core network.

[0006] Step 3: When the emergency base station detects a backhaul link interruption or quality below a preset threshold, it automatically switches to local emergency mode. In local emergency mode, the emergency base station stops providing services to the core network and provides local emergency communication. A unique local emergency communication ID is assigned to each terminal requesting access within the coverage area to uniquely identify and page the terminal in local emergency mode. Its format can be simplified to the standard 5G-GUTI. The local emergency mode entry notification is broadcast through an extended system information block, which at least includes a mode indicator, a list of available public numbers in the cell, and a random access configuration for terminal emergency communication access.

[0007] Step 4: After receiving the extended system information block, the terminal in the idle or connected state parses it to obtain the mode switching instruction; when the terminal has an emergency communication need, it initiates a random access procedure using a dedicated preamble sequence according to the configuration in the extended system information block, applies for and obtains the local emergency communication ID from the emergency base station, thereby completing the registration in the local emergency mode.

[0008] Step 5: In local emergency mode, terminals that have obtained local emergency communication IDs communicate via relay through the emergency base station (which acts as a local switching center), or through direct device-to-device communication coordinated by the emergency base station; all communication processes occur only within the local coverage area of ​​the emergency base station.

[0009] Step 6: When the emergency base station detects that the backhaul link has been restored and stabilized, it automatically switches back to the standard access mode and notifies all terminals through the system information block; the terminal decides whether to initiate the attach process to the standard 5G network according to the protocol requirements.

[0010] Furthermore, the emergency base station includes the following modules: The backhaul link monitoring module is used to monitor the connection status, latency, bandwidth and packet loss rate of the backhaul link between the emergency base station and the core network in real time, and generate a link quality report.

[0011] The mode decision and handover control module determines whether the current mode should be the standard access mode or the local emergency mode based on the link quality report, and controls the various protocol stack entities of the base station to perform mode switching.

[0012] The local emergency communication management module is responsible for generating, allocating, deactivating, and resolving conflicts of local emergency communication IDs in local emergency mode.

[0013] The extended system information management module is responsible for generating extended system information blocks that include local emergency mode entry notifications and related configuration information, and broadcasting them periodically or by triggering.

[0014] The local service processing module is responsible for handling communication requests between registered terminals in local emergency mode. It enables voice, messaging, and other services to be established and exchanged locally within the base station without uplinking to the core network.

[0015] Compared with existing technologies, the backhaul link adaptive 5G emergency base station communication method and system of the present invention have the following beneficial effects: To ensure uninterrupted communication in extreme circumstances, address the communication blind spots of emergency base stations after backhaul link failure, and provide emergency communication support for the last mile.

[0016] Adaptive and requiring no manual intervention, the base station automatically and smoothly switches modes based on the link status, improving emergency response speed and reliability.

[0017] It has good standard compatibility, transmits information by extending the system information blocks in the existing 5G protocol, requires little modification to the terminal, and its main functions are concentrated on the base station side, which facilitates industrialization and deployment.

[0018] Resource efficiency is ensured; in local emergency mode, only the minimum necessary communication functions are maintained, saving base station processing and air interface resources, and prioritizing emergency communication.

[0019] It is highly scalable and can provide more services when resources are sufficient, such as video telephony and data services, to better support disaster relief. [Attached Image Description] Figure 1 This is a block diagram of the adaptive backhaul link 5G emergency base station system of the present invention; Figure 2 This is a flowchart illustrating the switching of the 5G emergency base station system with adaptive backhaul link to local emergency mode according to the present invention. Figure 3 This is a flowchart illustrating terminal registration in emergency mode of the 5G emergency base station system with adaptive backhaul link according to the present invention; Figure 4 This is a flowchart illustrating the communication process between terminals in the emergency mode of the adaptive backhaul link 5G emergency base station system of the present invention.

Detailed Implementation Methods

[0020] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are limited to relative positions on the specified view, rather than absolute positions.

[0021] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0022] Please see Figures 1 to 4 The backhaul link adaptive 5G emergency base station communication method of the present invention is specifically a 5G emergency base station communication method and system based on backhaul link state adaptation and local computing power unit, comprising: After the emergency base station is powered on, it establishes or maintains a backhaul link connection with the 5G core network and continuously monitors the availability and stability of the backhaul link. When the backhaul link is stable and available, the emergency base station operates in standard access mode, serving as a standard gNB to provide communication services for terminals within the coverage area to access the 5G core network. When the emergency base station detects that the backhaul link is interrupted or the link quality is lower than a preset threshold, the emergency base station automatically switches to local emergency mode. In local emergency mode, the emergency base station stops providing services to the core network and provides local emergency communication, and assigns a unique local emergency communication ID to each terminal requesting access within the coverage area. The local emergency communication ID is used to uniquely identify the paging terminal in local emergency mode. The emergency base station broadcasts a local emergency mode entry notification through an extended system information block. The extended system information block includes at least: a local emergency mode indication, a list of available public emergency IDs within the cell, and a random access configuration for terminal emergency communication access. After receiving the extended system information block, the terminal initiates a random access procedure using a dedicated preamble sequence according to the random access configuration, and applies for and obtains the local emergency communication ID from the emergency base station to complete the registration. In the local emergency mode, terminals that have obtained the local emergency communication ID can communicate via relay through the emergency base station, or communicate directly from device to device under the coordination of the emergency base station. Once the emergency base station detects that the backhaul link has been restored and stabilized, the emergency base station automatically switches back to the standard access mode and notifies the terminal through the system information block.

[0023] The continuous monitoring includes obtaining the connection status, round-trip time, available bandwidth, and packet loss rate of the backhaul link through ICMP probes and SCTP link detection, and generating a link quality report.

[0024] The preset threshold includes at least one of a latency threshold, a bandwidth threshold, and a packet loss rate threshold, and the emergency base station adopts a hysteresis threshold or a continuous time window strategy to suppress mode jitter.

[0025] The extended system information block is encapsulated as extended information of SIB1 and broadcast within the cell. The extended system information block further includes a service type indication field, which is an 8-bit bit string that includes at least indication bits for voice service, SMS service, video telephony service and data service.

[0026] The maximum number of public emergency IDs in the list is 64, and each public emergency ID is a 39-bit bit string; the random access configuration includes an emergency preamble sequence range, which includes at least an integer with a start index of 1 to 63 and an integer with a length of len of 1 to 64.

[0027] When a terminal initiates the random access procedure, the MSG1 it sends uses the emergency preamble sequence; when the emergency base station receives an MSG1 that does not use the emergency preamble sequence, the emergency base station returns an RRCReject message to the terminal.

[0028] After completing the RRC establishment, the terminal sends an MSG5 containing an emergency registration request to the emergency base station. The emergency registration request contains the terminal's identity ID. The emergency base station forwards the emergency registration request to the local emergency communication management module, which allocates a 39-bit local emergency communication ID and records the mapping relationship between the identity ID and the local emergency communication ID in the database.

[0029] The local emergency communication ID is formed by combining the base station ID and the local ID, wherein the base station ID is used to distinguish different emergency base stations, and the local ID is used to distinguish different terminals within the coverage area of ​​the same emergency base station.

[0030] Inter-terminal relay communication includes: the source terminal sending an emergency communication request to the emergency base station containing the source-side local emergency communication ID and the target-side local emergency communication ID; the local service processing module of the emergency base station querying the routing information corresponding to the source-side and target-side local emergency communication IDs from the local emergency communication management module, and paging the target terminal to access via Paging messages to establish a communication connection between the source terminal and the target terminal.

[0031] The present invention also provides a 5G emergency base station system with adaptive backhaul link, characterized in that it includes a local computing power unit and a system connected to the local computing power unit: The backhaul link monitoring module is used to monitor the connection status, latency, bandwidth and packet loss rate of the backhaul link between the emergency base station and the 5G core network, and generate a link quality report. The mode decision and switching control module is used to control the emergency base station to switch between standard access mode and local emergency mode according to the link quality report. The extended system information management module is used to generate an extended system information block containing local emergency mode entry notification and random access configuration in local emergency mode and broadcast it within the cell; The local emergency communication management module is used to generate, allocate, deactivate, and resolve conflicts of local emergency communication IDs in local emergency mode. The local service processing module is used to process communication requests between registered terminals in local emergency mode, and to complete local switching or collaborative device-to-device direct communication within the emergency base station.

[0032] The extended system information block includes at least: a local emergency mode indication field, a service type indication field, a public emergency ID list field, and an emergency lead sequence range field.

[0033] The local computing unit includes a processor, a memory, and a local database. The local database is used to store the mapping relationship between the terminal identity ID and the local emergency communication ID, as well as the routing information corresponding to the local emergency communication ID.

[0034] Specifically, the present invention relates to a method and system for an emergency base station to adaptively switch its working mode when the backhaul link status changes, and to organize local emergency communication of terminals using local computing power units when the backhaul is unavailable.

[0035] The emergency base station of this invention can be a vehicle-mounted 5G base station, a portable 5G base station, or other rapidly deployable gNB form factor, possessing air interface coverage capability, and establishing a backhaul link with the 5G core network via satellite link, wireless self-backhaul, or other methods. This invention configures a local computing unit within the emergency base station to handle local emergency communication coordination and necessary service processing when backhaul is unavailable.

[0036] like Figure 1As shown, an emergency base station includes at least a backhaul link monitoring module, a mode decision and handover control module, an extended system information management module, a local emergency communication management module, and a local service processing module. The backhaul link monitoring module can periodically acquire backhaul link connection status, round-trip time, available bandwidth, and packet loss rate based on ICMP probes, SCTP link detection, and other methods, generate a link quality report, and report it to the mode decision and handover control module.

[0037] The mode decision and handover control module compares the link quality report with preset thresholds. When a backhaul link interruption is detected or the link quality falls below a threshold (e.g., latency exceeds a threshold, bandwidth falls below a threshold, or packet loss rate exceeds a threshold), a handover from standard access mode to local emergency mode is triggered. When the backhaul link recovers and stabilizes above the recovery threshold, a handover from local emergency mode to standard access mode is triggered. To avoid jitter, a hysteresis strategy or a continuous time window satisfaction strategy can be adopted.

[0038] like Figure 2 As shown, the backhaul link detection module periodically detects the backhaul link, including ICMP probes and SCTP link detection, and sends reports to the mode decision and handover control module. The mode decision and handover control module determines whether the backhaul link is functioning correctly. If it is not functioning correctly, it switches the mode to local emergency mode and notifies the extended system information management module. Extended SIB information is generated and notified to the standard protocol stack module. The standard protocol stack module combines the extended SIB information to generate new SIB information and broadcasts it within the cell. When an emergency base station enters local emergency mode, the extended system information management module generates an extended system information block, which is used to broadcast local emergency mode entry notification and related access configurations to terminals within the cell. The extended system information block includes at least: a local emergency mode indicator (e.g., the emergencies-Enable field), an available service type indicator (e.g., the service-type field), a list of available public emergency IDs within the cell (e.g., the public-ID-List field), and a dedicated preamble sequence range for emergency random access (e.g., the preamble-Range field).

[0039] Extended system information blocks can be encapsulated as extended information of SIB1 and broadcast within the cell by standard protocol stack modules. To reduce the probability of terminals that do not support emergency communication functions continuing to access the network, the preamble sequence range in the emergency random access configuration is set differently from the preamble sequence range of the regular contention access configuration. Terminals only initiate access using the emergency preamble sequence when they detect a local emergency mode and support emergency functions.

[0040] The following is an example of the ASN.1 definition for the extended system information block: -- ASN1START -- SIB1-EMERGENCE-EXT-START maxNrofPublicId ::= 64 SIB1-EMERGENCE-EXT ::=SEQUENCE { emergence-EnableBOOLEAN, service-typeBIT STRING (SIZE (8)) public-ID-ListSEQUENCE (SIZE (1.. maxNrofPublicId)) OF BIT STRING (SIZE (39)), preamble-RangeSEQUENCE { startINTEGER (1..63), lenINTEGER (1..64) } ... } -- SIB1-EMERGENCE-EXT-STOP -- ASN1STOP The specific list of IE browsers for ASN1 is as follows:

[0041] When a terminal receives information from the emergency communication system, it should register in emergency mode and save the list of public emergency IDs.

[0042] like Figure 3 As shown, the registration process for a terminal in emergency mode may include the following steps: The terminal sends MSG1, using the emergency preamble determined in the extended system information block, and randomly selects one to send.

[0043] The basic protocol stack records that the terminal is in emergency mode and performs a standard RRC establishment process; if the received message is not an emergency preamble, it directly responds with an RRCReject message.

[0044] The terminal sends an MSG5 message with emergency registration to the base protocol stack. The emergency registration message includes the terminal's identity ID, such as IMSI.

[0045] The basic protocol stack forwards the emergency registration request to the local emergency communication management module; the local emergency communication management module assigns a 39-bit emergency ID to the terminal and records the mapping relationship between the identity ID and the emergency ID in the database.

[0046] The local emergency communication management module forwards the assigned emergency ID to the basic protocol stack module.

[0047] The basic protocol stack module delivers the registration response information to the terminal via NAS direct transmission, and the terminal records the emergency ID.

[0048] The terminal enters an idle state and remains in an idle state through the standard RRC release procedure.

[0049] An emergency ID can be defined as a combination of a base station ID and a local ID. The base station ID is used to distinguish different emergency base stations, while the local ID is used to distinguish different terminals within the coverage area of ​​the same base station.

[0050] like Figure 4 As shown, the communication process between terminals in emergency mode may include the following steps: Terminal 1 sends MSG1, using the emergency preamble determined in the extended system information block, and randomly selects one to send.

[0051] The basic protocol stack records that the terminal is in emergency mode and performs the standard RRC establishment process; if the received message is not an emergency preamble, it directly responds with an RRCReject message; the emergency ID assigned to terminal 1 is contained in MSG3.

[0052] Terminal 1 sends an MSG5 message with an emergency communication request to the basic protocol stack. The message contains the emergency IDs of the source and target sides.

[0053] The basic protocol stack forwards emergency communication requests to the local business processing module.

[0054] The local business processing module queries the local emergency communication management module for the emergency IDs on the source and target sides to obtain routing information.

[0055] The local emergency communication management module retrieves relevant information from the database and forwards it to the local business processing module.

[0056] The local service processing module initiates a paging request to the target terminal 2 and forwards it to the basic protocol stack module.

[0057] The basic protocol stack module uses Paging messages to request terminal 2 to connect.

[0058] The connection between terminal 1 and terminal 2 is established through a standard communication establishment process. In one embodiment, the service bearer can be locally switched within the emergency base station by the local service processing module without uplinking to the core network.

[0059] In some embodiments, the emergency base station can provide two types of communication in local emergency mode: one is local switching communication relayed through the emergency base station; the other is device-to-device direct communication coordinated by the emergency base station. For the latter, the emergency base station can send direct connection resource configuration and synchronization information to relevant terminals to reduce end-to-end latency and save air interface resources.

[0060] Once the backhaul link is restored and stabilized, the emergency base station switches back to the standard access mode and notifies the terminals in the cell of the mode restoration through the system information block; the terminals can decide whether to initiate the attachment or reconstruction process to the standard 5G network according to the protocol requirements.

[0061] Compared with existing technologies, the backhaul link adaptive 5G emergency base station communication method and system of the present invention have the following beneficial effects: To ensure uninterrupted communication in extreme circumstances, address the communication blind spots of emergency base stations after backhaul link failure, and provide emergency communication support for the last mile.

[0062] Adaptive and requiring no manual intervention, the base station automatically and smoothly switches modes based on the link status, improving emergency response speed and reliability.

[0063] It has good standard compatibility, transmits information by extending the system information blocks in the existing 5G protocol, requires little modification to the terminal, and its main functions are concentrated on the base station side, which facilitates industrialization and deployment.

[0064] Resource efficiency is ensured; in local emergency mode, only the minimum necessary communication functions are maintained, saving base station processing and air interface resources, and prioritizing emergency communication.

[0065] It is highly scalable and can provide more services when resources are sufficient, such as video telephony and data services, to better support disaster relief.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A 5G emergency base station communication method with adaptive backhaul link, characterized in that, include: After the emergency base station is powered on, it establishes or maintains a backhaul link connection with the 5G core network and continuously monitors the availability and stability of the backhaul link. When the backhaul link is stable and available, the emergency base station operates in standard access mode, serving as a standard gNB to provide communication services for terminals within the coverage area to access the 5G core network. When the emergency base station detects that the backhaul link is interrupted or the link quality is lower than a preset threshold, the emergency base station automatically switches to local emergency mode. In local emergency mode, the emergency base station stops providing services to the core network and provides local emergency communication, and assigns a unique local emergency communication ID to each terminal requesting access within the coverage area. The local emergency communication ID is used to uniquely identify the paging terminal in local emergency mode. The emergency base station broadcasts a local emergency mode entry notification through an extended system information block. The extended system information block includes at least: a local emergency mode indication, a list of available public emergency IDs within the cell, and a random access configuration for terminal emergency communication access. After receiving the extended system information block, the terminal initiates a random access procedure using a dedicated preamble sequence according to the random access configuration, and applies for and obtains the local emergency communication ID from the emergency base station to complete the registration. In the local emergency mode, terminals that have obtained the local emergency communication ID can communicate via relay through the emergency base station, or communicate directly from device to device under the coordination of the emergency base station. Once the emergency base station detects that the backhaul link has been restored and stabilized, the emergency base station automatically switches back to the standard access mode and notifies the terminal through the system information block.

2. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1, characterized in that, The continuous monitoring includes obtaining the connection status, round-trip time, available bandwidth, and packet loss rate of the backhaul link through ICMP probes and SCTP link detection, and generating a link quality report.

3. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1, characterized in that, The preset threshold includes at least one of a latency threshold, a bandwidth threshold, and a packet loss rate threshold, and the emergency base station adopts a hysteresis threshold or a continuous time window strategy to suppress mode jitter.

4. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1, characterized in that, The extended system information block is encapsulated as extended information of SIB1 and broadcast within the cell. The extended system information block further includes a service type indication field, which is an 8-bit bit string that includes at least indication bits for voice service, SMS service, video telephony service and data service.

5. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1 or 4, characterized in that, The maximum number of public emergency IDs in the list is 64, and each public emergency ID is a 39-bit string. The random access configuration includes an emergency preamble sequence range, which includes at least an integer with a start index of 1 to 63 and an integer with a length of len of 1 to 64.

6. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1, characterized in that, When a terminal initiates the random access procedure, the MSG1 it sends uses the emergency preamble sequence; when the emergency base station receives an MSG1 that does not use the emergency preamble sequence, the emergency base station returns an RRCReject message to the terminal.

7. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1, characterized in that, After completing the RRC establishment, the terminal sends an MSG5 containing an emergency registration request to the emergency base station. The emergency registration request contains the terminal's identity ID. The emergency base station forwards the emergency registration request to the local emergency communication management module, which allocates a 39-bit local emergency communication ID and records the mapping relationship between the identity ID and the local emergency communication ID in the database.

8. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1 or 7, characterized in that, The local emergency communication ID is formed by combining the base station ID and the local ID, wherein the base station ID is used to distinguish different emergency base stations, and the local ID is used to distinguish different terminals within the coverage area of ​​the same emergency base station.

9. The 5G emergency base station communication method with adaptive backhaul link as described in claim 1, characterized in that, Inter-terminal relay communication includes: the source terminal sending an emergency communication request to the emergency base station containing the source-side local emergency communication ID and the target-side local emergency communication ID; the local service processing module of the emergency base station querying the routing information corresponding to the source-side and target-side local emergency communication IDs from the local emergency communication management module, and paging the target terminal to access via Paging messages to establish a communication connection between the source terminal and the target terminal.

10. A 5G emergency base station system with adaptive backhaul link, characterized in that, Includes a local computing unit and components connected to the local computing unit: The backhaul link monitoring module is used to monitor the connection status, latency, bandwidth and packet loss rate of the backhaul link between the emergency base station and the 5G core network, and generate a link quality report. The mode decision and switching control module is used to control the emergency base station to switch between standard access mode and local emergency mode according to the link quality report. The extended system information management module is used to generate an extended system information block containing local emergency mode entry notification and random access configuration in local emergency mode and broadcast it within the cell; The local emergency communication management module is used to generate, allocate, deactivate, and resolve conflicts of local emergency communication IDs in local emergency mode. The local service processing module is used to process communication requests between registered terminals in local emergency mode, and to complete local switching or collaborative device-to-device direct communication within the emergency base station.

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