Multi-Service Optical Transmission System Dual-Network Hot Standby System
In some important remote dispatch and control sites (such as subways, airports, and military facilities), high system reliability is often required. Services are frequently transmitted over two or more networks, and user terminals must be able to automatically select the normal transmission network.
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1 Overview
In some important remote dispatch and control sites (such as subways, airports, and military facilities), high system reliability is often required. Services are frequently transmitted over two or more networks, and user terminals must be able to automatically select the normal transmission network and channel. This necessitates a service automatic switching system that features high reliability, strong maintainability, the ability to accept independent network management control from multiple networks, and automatic switching based on service interface status. Therefore, the switching equipment should use as few active components as possible to reduce its own failure rate, and must incorporate multi-network switching interlock functionality!
Common methods to enhance system reliability include dual-interface mutual backup (such as dual optical ports or optical/electrical mutual backup), dual-board mutual backup, dual-unit mutual backup, and dual-network mutual backup. Dual-board mutual backup is typically used within equipment, such as dual power supply boards and dual main control boards. Dual-unit mutual backup includes cold standby and hot standby. Dual-network backup requires each service to be transmitted over two networks, with the receiving end selecting the better signal, usually through a selection switching device at the user interface.
Common user service interfaces include Ethernet interfaces, narrowband data ports (such as V.24/V.35/RS422/RS485), audio interfaces, and telephone interfaces. The backup methods employed are dual-interface mutual backup, dual-board mutual backup, dual-unit mutual backup, and dual-network mutual backup. To achieve optimal selection switching and manual forced switching of user ports, different interface types require different handling approaches.
For dual-interface mutual backup, dual-board mutual backup, dual-unit mutual backup, and dual-network mutual backup, Ethernet interfaces typically adopt simultaneous transmission and reception over both networks. When one network fails, the bandwidth is automatically reduced by half. For narrowband data switching, both networks typically transmit identical content simultaneously, and the receiving end automatically accepts data from the first network that delivers data. For these data channels, line bit errors are not considered; when bit errors occur on the line, a switching command is issued through the network management system. For voice channels, the signaling status is prioritized for judgment. When signaling statuses are identical, the presence of voice data is then checked. If both signaling and data are identical, the default network is preferred. Typically, these judgments are implemented on digital lines.
2 Backup Switching Mechanism
The dual-network hot standby switching equipment primarily provides hot standby protection for E1, telephone, and V.22 services. When a fault occurs in the primary ring equipment or a channel alarm is generated for a service (E1, telephone, or V.22), the hot standby switching equipment automatically switches the corresponding channel service to the standby ring transmission equipment based on the monitored alarm status.
When the fault in the original primary equipment is resolved or the channel alarm for the service (E1, telephone, or V.22) disappears, the equipment can serve as standby equipment for future fault switching.
