Mine Rescue Team Underground Disaster Relief Communication Dispatch System Solution

I Overview

1.1 Application Background

Currently, investment by coal mining enterprises in China in the field of emergency rescue is mainly concentrated on large equipment, such as drilling equipment, drainage systems, and escape capsules, while insufficient attention is paid to emergency communication systems. Within the limited communication system investment, resources are mostly allocated to surface facilities, such as communication command vehicles and command dispatch software. There is an extreme shortage of intrinsically safe communication equipment truly suitable for underground rescue operations. This situation is influenced not only by investment orientation and implementation difficulty, but also reflects the practical dilemma that underground emergency rescue communication technology has long failed to achieve substantial breakthroughs.

As the "perception hub" of post-disaster mine rescue, the emergency communication system undertakes key functions such as environmental monitoring, information transmission, and command dispatch. It can obtain real-time underground disaster dynamics and personnel status, optimize rescue resource allocation, and significantly improve rescue efficiency.

1.2 Deficiencies of Existing Technologies

Although various mine-used emergency communication devices are available on the market, they generally suffer from the following technical bottlenecks:

(1). Limited coverage capability: The effective transmission distance of existing devices is generally no more than 1-2 kilometers, making it impossible to build a complete communication link from the disaster area to the safe zone.

(2). Insufficient battery life: The continuous operating time of intrinsically safe communication base stations is generally less than 4 hours, which cannot support the continuous rescue operation demand of a single shift (8 hours).

(3). Data transmission bottleneck: The existing bandwidth is difficult to carry the concurrent transmission of multiple voice channels, environmental data, and high-definition video.

(4). Low deployment efficiency: System activation requires complex parameter debugging, placing excessively high technical requirements on operators.

(5). Weak network reliability: Base stations mostly use serial wireless connections, and a single point of failure can easily cause the entire communication system to collapse.

(6). Low functional integration: There is a lack of solutions integrating precise positioning systems with vital sign monitoring, posing hidden risks of secondary accidents.

(7). Poor anti-interference capability: High-intensity noise at the rescue site seriously affects voice communication clarity and reduces coordination efficiency.

II System Introduction

2.1 Design Concept

In response to the deficiencies of existing products and the special environment faced by coal mine rescue, the underground emergency rescue communication dispatch system must possess the core characteristics of full intrinsic safety, portability, ease of deployment, long communication distance, and strong battery endurance. The absence of any one of these features will greatly reduce the practicality of the system. Video surveillance provides the most intuitive video images and is the most effective means of on-site command and post-incident analysis when facing complex disaster scenarios. It is also a function that a new generation of emergency rescue communication dispatch systems must possess.

2.2 System Features

The core functions of the mine-used emergency rescue communication dispatch system mainly include the following aspects:

First, under extreme emergencies, in the case of "three disconnections" (road disconnection, network disconnection, and power outage), rapidly establish the main communication link between the surface and underground as well as rapid underground network coverage through various wired and wireless communication methods such as portable fiber optic cable, field wire, wireless MESH, and wireless WiFi Halow;

Second, after establishing the main communication link between the surface and underground and underground network coverage, access to more communication systems can be achieved through corresponding supporting modules, including wireless intercom systems, 4G/5G communication, satellite communication, trunked radio, etc., providing more communication means for assurance.

Third, after rapid network communication establishment, achieve integrated command dispatch functions between the surface and underground, including voice dispatch, video dispatch, audio/video conferencing, video surveillance, and wireless intercom functions.

2.2.1 Emergency Rescue Surface and Underground Communication

(1). The surface rescue command and underground use portable fiber optic cable and field wire transmission methods. Through underground converged communication terminals supporting fiber optic cascade and field wire bus-type access, the surface-underground main communication network is quickly established. Multiple communication methods improve the overall reliability of the system, and intelligent multi-routing technology resolves the adverse impact of single point failures on the system;

(2). Underground converged communication terminals can be further extended through fiber optic cable and field wire to expand network coverage;

(3). Underground converged communication terminals themselves support wired network access and can directly connect underground Ethernet communication terminals such as IP cameras, IP broadcast terminals, and IP phones;

(4). Underground converged communication terminals can also achieve wireless networking coverage through their built-in MESH self-organizing relay or WiFi Halow wireless relay, providing WiFi access for underground intrinsically safe phones and intrinsically safe wireless cameras, expanding coverage and achieving the贯通 of the entire communication channel from the underground disaster area, underground safe area, to the surface command center;

(5). Underground converged communication terminals are portable explosion-proof devices with built-in large-capacity batteries, configuration-free networking, easy portability and rapid deployment, and can provide continuous operating time of no less than 8 hours;

(6). If underground converged communication terminals operate only in field wire communication mode, they do not require power supply and have no battery life issues;

(7). Complete supporting communication terminals: can access other explosion-proof communication terminals supporting WiFi, such as WiFi integrated intercom safety mining helmets, ruggedized intrinsically safe smartphones, portable intrinsically safe wireless cameras, intrinsically safe tablet computers, and command system platforms.

2.2.2 Converged Communication

2.2.2.1 Cross-terminal Mixed Grouping

n Supports mixed grouping of terminals such as SIP intercom, portable command platform, narrowband trunked radio, public network POC, and 4G/5G terminals;

n Interoperates with narrowband trunked radio to supplement the capabilities of the existing narrowband trunked network;

n Command center dispatchers interact with on-site personnel's mobile terminals to achieve the exchange of multimedia messages such as voice, text, images, and video.

2.2.2.2 Wireless Intercom System Convergence

Supports access to commercial 130M trunked radio, public security 350MHz trunked radio (PDT) system, 370MHz emergency management trunked radio (PDT) system, 400MHz commercial trunked radio system, analog/digital conventional (DMR) system (channel point-to-point communication), and shortwave system. A dedicated gateway is provided on the basis of the user's existing wireless network to achieve converged interconnection. After convergence, interoperability with other communication means within the system can be achieved.

2.2.2.3 UAV Integration

Supports integration with various audio/video payloads of UAV systems, integrating UAV positioning and audio/video data for unified dispatch, enriching the collection and dispatch means of on-site command in converged communication.

2.2.2.4 Video Surveillance Access

Supports integration with video surveillance systems through national standard protocols, enabling retrieval of on-site surveillance images, and supports forwarding/distributing surveillance images to other multimedia terminals (mobile APP, dispatch console, etc.), supporting video formats such as H.264, MPEG, and MPEG-4.

Mainly accesses video signals from devices or terminals such as underground explosion-proof cameras, smart safety helmets, and intrinsically safe phones, providing clear underground video images.

2.2.2.5 Underground IoT Access

Supports access to underground IoT devices and terminals through wired and wireless methods such as WiFi, Ethernet, and LoRa, including intrinsically safe multi-parameter gas detectors (CH₄/O₂/CO/CO₂, etc.), dust concentration monitors, smart mining helmets, individual video recorders, drilling equipment tooling detection terminals, and emergency power management systems. This enables the access of environmental monitoring, personnel equipment, and rescue equipment, providing real-time and comprehensive data support for emergency rescue decision-making, effectively improving the success rate and safety of accident rescue.

Once the surface portable smart platform detects abnormal data from underground IoT monitoring, it provides pop-up alarm alerts and voice broadcast reminders, and displays the positions of personnel and equipment as well as specific data information in real time.

2.2.3 Emergency Rescue Command Dispatch

2.2.3.1 Voice Dispatch Functions

The surface portable command platform can initiate voice dispatch functions for underground phones, broadcast terminals, intrinsically safe phones, and individual soldier terminals, mainly including all basic voice communication and supplementary service functions, common dispatch functions, dispatch conference functions, recording, system management, dispatcher management, and other related functions. It supports command dispatch functions such as emergency call, dialing, monitoring, call pickup, hold, barge-in, forced release, transfer, conference, dial pad, editing, and broadcast for various communication terminals.

n Call: call function can be implemented through the screen dial pad or by selecting the target terminal;

n Emergency Call: emergency call. Emergency calls have a different ring tone from normal calls;

n One-number Call: clicking one-number call sequentially connects through various communication means in the order most likely to reach the user until a response is received;

n Hang Up: immediately ends the call of the selected terminal;

n Monitor: monitors the call of the selected terminal without the other party's awareness. It can be applied in modes such as call monitoring and ambient monitoring;

n Barge-in: turns the call of the selected terminal in conversation into a three-party conference mode;

n Whisper: communicates with the selected terminal in conversation without the other party's awareness;

n Forced Release: turns the call of the selected terminal in conversation into a call with the console, and the other party is forcibly disconnected;

n Transfer: transfers the call of the selected terminal to a designated terminal.

n Consultative Transfer: before transferring an incoming call to a designated extension, first seek the extension's opinion. Commonly used for transferring calls to important leaders or important locations.

n Roll Call: used to call all extensions in the group once. After connection, pre-recorded voice is played, the agent phone can monitor and interject, and finally call statistics records are provided. It can also be used for enterprise roll call, e-commerce sales, etc.;

n Polling: used to call all extensions in the group N times. Each round calls the extensions that were not connected in the previous round. It stops after N rounds or after manual intervention, and finally provides call statistics records. Commonly used for telephone notification services;

n On Duty: used to transfer the agent phone to the duty phone, also known as "night service" phone.

n Recording: records the designated phone call and automatically stops when hung up;

n Conference: used to create a temporary conference group for selected extensions, activate and switch to the conference group interface. Conference groups can also be created in the contacts interface.

n Broadcast: used to create a temporary broadcast group for selected extensions, activate and switch to the broadcast group interface.

n Intercom: used to create a temporary intercom group for selected extensions, activate and switch to the intercom group interface.

n Camera: used to display the video associated with the current user. If in a two-party call, both parties' videos are displayed simultaneously.

2.2.3.2 Audio/Video Dispatch Functions

Main functions include: call, receive, retrieve, monitor, video forwarding, video distribution, command issuance, screen sharing, consultation management, video fusion (screen management), video source management, audio/video recording, and data management.

n Call: the dispatch console calls the audio/video individual soldier terminal;

n Receive: when a call from the audio/video individual soldier terminal is received, click the terminal button to answer;

n Retrieve: used to view related business files stored on the server, including documents, parameter data, pictures, and images.

n Monitor: used for the dispatch console to automatically retrieve the content of the user's camera without the consent of the individual soldier terminal user. Individual soldier users can configure whether to enable this function. It also includes monitoring of cameras;

n Video Forwarding: Transfers the video of a terminal currently communicating with the dispatch console to other idle audio/video terminals;

n Video Distribution: Distributes the dispatch console video or a window containing multiple videos to multiple other audio/video terminals;

n Command Issuance: Sends text SMS command messages to one or more terminals; individual soldier terminals will reply with confirmation messages upon receipt;

n Screen Sharing: Refers to the dispatch console sharing its screen, or a window on its screen, with a terminal or video conferencing group;

n Create Conference: Refers to pulling multiple audio/video terminals into a meeting room group and naming the meeting room;

n Meeting Group Management: Modifies the meeting name and member list of an already created meeting room;

n Start Conference: Refers to inviting all members of a created meeting to join the conference. If a meeting member accepts the invitation, they join. If the invitee is a dumb terminal such as a network camera, it automatically joins. If the meeting has already started, the dispatch console automatically joins the meeting.

n Enter Conference: Refers to a dispatch console user directly entering an ongoing meeting. (An authorized dispatch console can freely enter and exit designated meetings.) This includes the following functions:

(1). Video Fusion: Used to output the images of a video conference in certain preset layout arrangements. It is typically used for output to large screens or to terminals such as mobile phones, and can also be used for meeting recording; video fusion modes include equal division mode, N+1 mode, VIP mode, etc.;

(2). Audio Output Selection: Used to select which audio sources can be output through a specific sound card; multiple audio sources can be selected for mixing;

n Audio/Video Recording: Used to record the audio/video of a terminal, and can also record the fused video of a meeting room;

n Search: Used for searching audio/video recordings, as well as searching system operation logs and user status records;

n Document Management: Management of shared document materials for each dispatch console and individual soldier terminal, including adding, deleting, and trigger settings.

2.2.3.3 Emergency Broadcast Function

The ground portable command platform supports emergency broadcast dispatching functions for underground emergency broadcast terminals, including intercom, voice insertion, file insertion, forced interrupt, monitoring, hold, transfer, forced release, time announcement on the hour, task creation, and other functions.

2.3 System Architecture

System Design Description:

The network communication infrastructure at the accident site is mostly damaged by the accident or disaster, or becomes unusable due to on-site power failure. Moreover, many locations have neither wireless network coverage nor fiber optic cable access. In such cases, the network needs to be rapidly rebuilt. Therefore, the mine emergency rescue system is centered on convenient, fast, and reliable networking to ensure the implementability and usability of the system.

Based on the distance from the accident site to the ground command center and the complexity of accident handling, the networking method is selected from all-wireless (WiFi Halow or MESH) networking, fiber + wireless networking, or field wire networking. The networking method is flexibly selected based on transmission distance and deployment conditions.

(I). Portable Fiber Optic Networking

Primarily connects the ground portable dispatch host with the underground converged communication terminals, establishing the main trunk communication between the surface and underground, providing high-bandwidth communication.

(II). WiFi Halow or MESH Wireless Networking

As underground converged communication terminals advance into the tunnel, WiFi Halow or MESH wireless relay networking can be adopted to reduce cabling work. This equipment supports built-in battery power supply; simply moving the equipment can expand network coverage. Other underground individual soldier devices or intrinsically safe phones can connect via WiFi.

(III). Field Wire Networking

Both the ground portable dispatch host and the underground converged communication terminals support field wire access. The underground converged communication terminals use field wire transmission for networking, which offers three major advantages:

n Bus-type access: Field wire can be quickly connected via clamping terminals, greatly reducing connection time;

n In field wire communication mode, the underground communication terminal can provide wired network access without external power supply;

n Long transmission distance: A maximum of 2M transmission bandwidth can be provided over 10KM of field wire, with up to 15 terminals connected in bus topology.

(IV). Hybrid Networking

Both the ground portable dispatch host and the underground converged communication terminals support simultaneous access via multiple communication methods. Based on the rescue site conditions, network communication functions can be implemented on multiple directions and multiple rescue chains.