With the rapid development of China’s national economy and accelerating urbanization, rapid population growth in the mobile ground public transportation to the city to bring heavy pressure, making more and more city builders to solve the problem of public transportation subway and sights trams and other public transport facilities, modern city life urgently require people always grasp the dynamic global information, passengers in the car not only know the car notes, train schedules and other text information, but also need to understand the stock information, media, political news, events dynamic information broadcast, advertising, high-bandwidth data wirelessly car carrying capacity makes PIS (Passenger Informaiton System) passenger information service system and CCTV (Close Circuit Television) CCTV system into a possible application of PIS + CCTV system, so that the original closed the cabin space into a & ldquo; the car to the integration of information and entertainment center & rdquo ;, increased passenger comfort。

PIS+CCTVSystems business needs explanation
PIS passenger information service system is between open and closed compartments ground information most intuitive information exchange platform, the need for strict stability to ensure reliable operation of the train at the highest 100KM / H when the vehicle to communicate real-time information will be passed to the car floor end play. CCTV CCTV system needs to train internal monitoring data uploaded to the ground control center in real-time to help train dispatchers, police security center emergency incidents. The early lack of subway construction vehicles to wireless communication technology, multimedia playback and video surveillance can only be limited to the station level and simulation technology, mainly due to the high cost of analog monitor large-scale deployment and history does not support remote access to features such as image search, available is often not very high efficiency, a new trend of development of IP-based digital surveillance system to Ethernet IP technology as the core of PIS + CCTV systems integration solutions enable video broadcast control systems, surveillance systems, storage systems and other sharing resources and centralized management systems, reduce project implementation costs, but also improve the efficiency of operation and maintenance management。
From the perspective of the required bandwidth hosting business systems analysis, the PIS system and CCTV systems generally require vehicles to remain stable at 15Mbit wireless bandwidth above, which includes land to the car PIS system 8Mbit (MPEG2 format) video bandwidth, ground vehicle CCTV system to 4Mbit bandwidth。

Implementation of technology from the perspective of network analysis system, high-speed train traveling, trackside deployed along the AP and AP-car average will conduct a wireless MESH link switching (AP trackside distribution to 200 m intervals every 12 seconds to deploy, train speed to 60KM / H calculation and analysis), as well as a host for the purposes of car ground server is unable to determine wireless MESH link perception and timely handover process and change the MAC address forwarding, Layer 2 data forwarding in accordance with the principles will still switch from the original site port forwarding data, resulting in the loss of video data streams or network outages, and therefore, in program design needs from product configuration, network planning and other technical point of view, to protect the security of the entire network system reliability。

Overall network design and analysis of vehicle wirelessly PIS + CCTV system
Subway ride to the network systems are generally in the range of relatively independent platform for a network unit, maintaining the network structure within their respective ranges, each station by the network reasonable intervals in series to form a huge final overall PIS + CCTV network system . But this rail project will not only invest huge long construction period, and the structure of complex systems, subsystems, once construction is completed after any changes are very difficult to want to do with the increase in the provinces and subway lines, the lines cross through the entire province City subway network integration for an increasingly large share of the overall structure of the system resources, which makes subway operating company from the perspective of system operation and maintenance management urgently requires a long-term plan to improve the overall network system maintenance convenience and later line intersection easy expansion of the link. Therefore, the network system should be deployed to fully consider the above issues, the following guidelines from the overall design。

High availability and reliability
Network equipment and systems must have online resilience to avoid a single point of failure, the key equipment, lines can be done in real-time backup and automatic failover backup, network system has strong fault tolerance to ensure the normal operation of a variety of applications, with high availability and reliability。

Scalability and manageability
All system equipment not only to meet current needs, and after the expansion module to meet demand for the foreseeable future, such as the expansion of bandwidth and equipment, applications, extensions, and so extend the subway station, after the completion of the construction of the system when upgrading to new technologies now ensure stability of the system. Taking into account the future operation and maintenance of the subway, the entire network management subsystem should be easy to maintain, easy to operate security, data flow, performance and other aspects of well monitoring and control, and remote management and troubleshooting。

Normative and mature nature of security
Technology and equipment used in the system design should be consistent with industry standards, that is, the use of advanced technology is mature, standard technology to provide network-layer security measures to prevent unauthorized access and leapfrog operate outside the system operator members, protection secure and reliable network system。

Economical use of
Under the system to meet the requirements and needs of the existing premise, give full play equipment performance, while saving the investment needs of developing full consideration to determine the size of the system。

PIS system application layer：
Business applications are deployed in the service sector supports video broadcast control, equipment operation and maintenance management functions, wireless controller manages all access layer switches hanging platform trackside AP, 1 + 1 fast heat between two wireless controllers backup, business systems to achieve smooth handoff when a line fault, OCC control center deployment of a network management system to realize all of the devices in the network system, service configuration, performance, alarm monitoring and management of unified。

PIS system core network layer：
In the OCC control center equipped with two high-reliability industrial Ethernet switches MISCOM8600S Series devices achieve through cable and interval and depot Ethernet switches interconnected 8600S two core switches in the fast ring redundancy as the intersection node is connected to both two ring network access layer, dual-core technology access network node using VRRP avoid a core switch failure led to the whole network business interruption, improve network reliability of the overall solution。

PIS system network access layer
Access layer network using two rings, trackside AP within the same interval adjacent access method using a cross between the two stations switch to avoid project implementation from the perspective of a single platform access switch failure resulting in paralysis of the entire range of issues。

PIS system car wirelessly access layer
Car as an extension to the wireless access layer terrestrial network to provide two-way transmission channel between the ground and the train, through the actual sentinel survey analysis tunnels and elevated trackside environment AP points were reasonable deployment。

Car LAN
Car access to the AP-board video controller cab vehicle network, a train PIS system and CCTV systems are interconnected via an internal switch compartment; Car AP sends a wireless link to the trackside signal scanning AP, in the process of moving trains with real-time computing o trackside seamless switching between AP and achieve vehicle networks and terrestrial communications network connection。

Terrestrial transmission network system – Ring Design
Special industrial environment metro project design and operational requirements of the network system with high reliability and redundancy protection, early terrestrial network design typically uses a star network structure or ring + STP protection agreement, but poor star network redundancy while the STP convergence time is generally larger diameter second stage and the network convergence longer using RSTP / MSTP or south dedicated fast ring redundancy protocol convergence time can be reduced, for the use of harsh conditions PIS rail transportation systems and CCTV systems solve the problem of network delay, prevent broadcast storms caused by data loops. With several fast convergence, convergence is independent of time and the number of nodes on the ring features。

OCC ground control center core switches and switches each station two intersecting rings, according to the station platform switch interval deploy two rings are connected to networks, OCC core switches are simultaneously access both in the ring。
Station staggered switch connected to the two rings, when there is a fault of a ring network, the policy does not affect the work of the other ring, and when the project implementation wired staggered deployment loop network access and trackside wireless AP can cooperate closely staggered deployment after the realization of a ring network paralyzed, another ring still work。
 

Terrestrial network systems – Control Center Network Design
OCC terrestrial network control center to achieve under each platform passenger terminal and car terminal hair guided by information and public multimedia capabilities hee hee, issued by the following transmission network is transmitted to each relay station controllers, PIS data transmission network or depot equipment, control Center system Access Figure

Combined network system design requirements into account many aspects reliability, product performance, service features, security features and scalability, the ground control center switches use two OCC MISCOM8600S switch and allows VRRP protocol to protect the core layer of the network, through the bicyclic each station and depot network and switch interconnects to achieve Internet communication with the control center。

Terrestrial network systems – station and depot network design
According to the station and depot network requirements are relatively independent of each station to configure an Ethernet switch each MISCOM8020M, OCC is connected to the control center via fiber optic core switch, the controller simultaneously access relay station of each system, the station management workstation, PDP display controller, and through Optical achieve orbit mobile wireless transmission network interconnection AP, AP trackside during implementation of the project within each interval adjacent to a crossover between the two stations switch access methods, from the perspective of project implementation to ensure that each individual site access switch malfunction trackside radio signal can still achieve full coverage throughout the PIS greatly improve the reliability of data transmission system。

Car to the wireless network system – wireless two-way data transmission network design
The most important part of the overall risk of transmission network system design point is the largest part of the car to the wireless network bidirectional data transmission network, wireless two-way controller, Optical, laying rail depot paraneoplastic library use wireless AP and antenna, car wireless AP, part of the antenna and automotive switches, wireless networking solutions designed to meet the access layer Ethernet networks through between WLAN 802.11a / b / g standards, wireless controller and trackside interoperability AP。