Kunming, known as the "Spring City", is the capital of Yunnan Province and a gateway city for China's opening to Southeast and South Asia. It is a national historical and cultural city, an important tourism and commercial city, and a key central city in western China.
Kunming Rail Transit Line 6 is the first line of Kunming Rail Transit, connecting the Wujiaba Central Business District and Kunming New Airport, with a total length of 26.6 kilometers.
On June 28, 2012, the first phase of the project opened for trial operation. The second phase will be completed in 2017, with a new city terminal near the starting station Tangzixiang Station. The new city terminal will be connected to the starting station of Phase II of Line 6, allowing passengers to check in luggage, print boarding passes, and other aviation services in the city.
However, the communication system of the already-built Phase I of Line 6 faces many problems:
Insufficient line bandwidth
The original transmission backbone used RPR technology networking, with a maximum line bandwidth of 2.5G and actual bandwidth of 1.25G. Subsequent bandwidth improvement through RPR technology is impossible. With the gradual application of high-definition video technology and intelligent analysis technology in urban rail transit, the metro communication backbone network must match it. The construction of 10G, 20G, or even 40G backbone networks has become a common consensus in current domestic metro construction. The bandwidth limitation of RPR technology has become a bottleneck in metro construction and development.
Weak full-service carrying capacity
Kunming Metro Line 6 was built over a long period, with many types of services and interface styles. There are more than 10 types of services carried by Ethernet technology (such as office OA, video surveillance, PIS, AFC, etc.); narrowband voice dedicated wireless and dedicated telephone are carried by TDM technology; in addition, services such as SCADA, trackside telephone, and signal systems need to be carried through low-speed PCM interfaces. Diverse services are carried by different technologies. Correspondingly, the transmission backbone network must also be a converged platform containing multiple transmission technologies.
Poor security and reliability
The metro communication network is a dedicated private network. The dedicated private nature is reflected in the fact that each business system is networked separately from the station access end, the transmission layer uses time slot division for service isolation, and finally the services are terminated at the control center by subsystem. Different business systems cannot be integrated with each other to avoid single-system failures affecting the normal operation of other business systems. The protection means of the transmission network must be complete, and single point failures must not be allowed to affect the normal service operation of other nodes on the line.
Based on the above requirements, the traditional RPR solution cannot meet the bandwidth requirements of Kunming Metro's business development. Adopting a converged transmission technology platform that supports physical isolation of business systems to upgrade the existing transmission backbone network has become the best choice for Kunming Metro Line 6.
Huawei Enhanced MSTP Solution for Metro
After strict selection, Kunming Metro decided to adopt Huawei's enhanced MSTP technology as the basic bearer network. This solution, with "soft and hard pipes" and "Smart 40G" as its core, can uniformly transmit TDM, packet, and PCM services, achieving effective integration of service security and transmission efficiency. Enhanced MSTP includes the following key technologies:
Smart 40G Intelligent Line Card
Enhanced MSTP features the Smart 40G intelligent line card, with single-port bandwidth four times that of traditional MSTP. It innovatively introduces OTN technology. The 40G port of the line card is implemented through OTU3 granularity, and the port can be split into multiple small-granularity ODU2/ODU1/ODU0 pipes. Therefore, the Smart 40G line card can simultaneously support 10G/2.5G/GE small-granularity transmission pipes, and can carry different metro services through different ODUK pipes, thereby achieving physical isolation of services, ensuring high reliability, high security, and hard pipe bearing of services, and improving end-to-end bandwidth guarantee to prevent a sudden burst of one service from affecting other system services; in addition, ODUK granularity supports binding into packet or SDH pipes, thereby realizing the bearing of metro SDH and packet services on the same optical fiber. The line side of enhanced MSTP can provide 10G/20G/30G/40G bandwidth, and users can flexibly choose according to service volume and smoothly upgrade as services grow. By upgrading the bandwidth license, an "on-demand payment" investment model is realized. Kunming Metro Line 3 and Line 6 both adopt the Smart 40G intelligent line card networking solution for transformation and upgrade. The line bandwidth is initially configured according to 10G requirements, and later can be evaluated and expanded to 40G bandwidth through license software upgrade, providing super-large line bandwidth for various systems, meeting existing high-bandwidth demands while having the ability to smoothly evolve without replacing hardware.
Integrated Unified Switching
The enhanced MSTP solution realizes unified switching of TDM services, packet services, and PCM services on one device, and realizes unified bearing of all services on a pair of optical fibers on the line side, thereby realizing a single network that uniformly carries TDM, packet services, and PCM services in metro communication, avoiding the waste of equipment and optical fiber investment caused by packet networking. The enhanced MSTP solution provides two types of pipes: MPLS-TP packet and SDH. Among them, 2M services such as official telephone and dedicated telephone are carried in traditional SDH hard pipes to ensure security and low latency; IP services such as CCTV and passenger information are carried in MPLS-TP packet soft pipes to improve packet bearing efficiency, and users can obtain the same excellent operation and maintenance experience as SDH networks.
MPLS-TP Packet Transport Technology
MPLS-TP is a connection-oriented packet-switched network technology. It provides packet soft pipes through MPLS label switching, realizes efficient statistical multiplexing of packet services, and greatly improves the transmission efficiency of packet services; MPLS-TP inherits the SDH-like OAM mechanism of transport and has powerful OAM functions; in addition, MPLS-TP uses network management E2E static configuration, without the complexity of MPLS signaling and IP functions. At the same time, MPLS-TP also supports cross-ring communication, ensuring independent switching of each sub-ring. A single ring supports up to 64 nodes, greatly enhancing networking capability and meeting the expansion needs of metro line cards. Enhanced MSTP provides comprehensive protection mechanisms. 2M SDH services such as official telephone and dedicated telephone adopt SDH protection; IP services such as CCTV and passenger information adopt MPLS-TP ring network protection. Both SDH and MPLS-TP ring network protection can achieve 50ms telecommunication protection switching.
Enhanced MSTP Facilitates Upgrade of Kunming Metro Line 6
At present, part of the transmission backbone network transformation and upgrade of Kunming Metro Line 6 has been commissioned, making full preparations for the online commissioning of various business systems. After the transformation, the communication system of Metro Line 6:
Adopts a mature 20G platform, with subsequent smooth upgrade to 40G; smooth upgrade of large bandwidth saves customer investment.
Provides customers with a reliable end-to-end integrated service transmission network, achieving unified bearing of all services.
Physical isolation ensures service security.
After a short wait, the upgraded Line 6 will certainly provide better service quality and a better travel experience for Kunming's transportation.