In order to optimize the dispatching and deployment of the fleet, live data from the vehicles is required, which flows into the control center. Consequently, digitalization begins with the network design in the vehicles. It should meet the requirements of public transport operators – on the one hand, to ensure a high quality of service for passengers, and on the other hand, to optimize the effectiveness of internal operations.
In the following, we will design an IP network for digitalized public transport buses in 7 steps. This network will have a high degree of data transparency and thus the best prerequisites for efficient operations.
For many transport operators, the digitization of operations and thus of the vehicle fleet is a key issue. However, the approaches differ: depending on the condition, age and equipment of the vehicles, a conversion of the entire fleet must be weighed up against continuous renewal via new vehicle procurement.
Conversion requires a high level of investment in a short period of time, the vehicles have to be rewired, and the new equipment installed and put into operation. In return, the conversion to digital systems takes place in a short time. Transport companies can benefit from live data earlier and, if necessary, generate additional revenue from ticket sales (contactless, via app/smartphone) or target group- and location-based advertising. The effort required to support two systems (analog and digital) is lower in the case of a retrofit, as the changeover takes place in a short time here.
The path to a digital bus fleet via new vehicle procurement takes longer. Transport companies replace about 10 percent of their bus fleet every year. Assuming a service life of 10 years, the changeover would therefore be completed in 10 years. The advantage is the comparatively low investment and the low cost of installation and cabling, as these can be handled directly by the bus manufacturer. The disadvantage is the long transition period during which two systems exist in parallel and have to be maintained.
Regardless of which path you take as a transport company, it is important to address the issue of network infrastructure in the vehicle at an early stage, so that implementation, whether through retrofitting or new vehicle procurement, is quick and easy.
In a typical case, all or nearly all existing devices in the vehicle are connected into a network. In this example, we equip a solo bus with all the devices we consider important for efficient operation and an optimal passenger experience. This includes interior and exterior displays, ticketing systems, passenger counting systems, digital cameras or recorders, and passenger Wi-Fi. In the network design, we also consider the on-board computer, which plays a central role in network control, and the router, which sends network data to the control center.
All devices are components that have their own IP addresses and can be accessed remotely. The device configuration itself is not covered here.
All onboard devices that are to be installed are summarized in a list:
- Board computer x1
- Driver control unit x1
- Ticket validator x2
- Passenger counting system x2
- Camera x3
- Video recorder x1
- Travel indicator x3
- Passenger information system x2
- Router x1
- Managed Fast Ethernet Switch x2
We decide on the type of switches we will use to build our network at the end. We choose managed switches because they provide the visibility and control we need for our digitalized city bus. We make the number of switches and the number of ports per switch primarily dependent on the total number of peripherals. To provide maintenance access to the entire network and for future network expansion, at least one port per switch is left free.
Taking into account the function that each device performs in the bus as well as the space available, we determine the exact installation location for each device. We arrange the devices schematically as they will later be installed in the vehicle.
The power supply for the IP devices is also important for the installation and network planning. Therefore, when determining the installation location of switches, the cable routing must also be considered. The same applies to retrofits where cables are already installed. Devices powered via Power over Ethernet (PoE) do not require a separate power supply cable and are powered directly by the switch. For this, the Ethernet switch used should support the PoE function.
Practice shows that line topologies are most practical in buses and therefore make the most sense. For our solo city bus, we also decide on a simple line topology, which we implement with two Ethernet switches. Both switches have PoE and Gigabit ports (for connection between both switches and switch router). Thanks to 16+10 ports, all intended devices can be connected, leaving ports for future network expansion.
Leaving ports free is a common practice and is also recommended by the Public Transport Interoperability Organization ITxPT.
In a network with many participants, it is often not absolutely necessary or even desirable for all of them to be able to communicate with each other. To prevent this, a precise communication plan is necessary. It schematically shows which devices in the bus should communicate with each other and which should not. This also results in the logical network infrastructure.
A limited communication capability of the devices within the network is essential in complex, digital IP networks. Managed switches make this possible by dividing the entire network into logical subnetworks. This ensures, for example, that the passenger Wi-Fi is separated from the rest of the systems (e.g. camera). Thus, unwanted intrusions are prevented and the security level of the data is increased. This is meant to prevent unwanted intrusions and increase the security level of the data.
After defining the logical network infrastructure, we implement it schematically using virtual LANS (VLANs). The network separation can be seen in the figure below. Thus, cameras and VTRs exchange data with each other, but they do so only within the virtual video network. Only network-critical IP participants such as the on-board computer and the router have access to all data or forward it.
Note: Typically, not all devices in a network are VLAN-capable. If necessary, the managed Ethernet switch takes over the separation, whereby a fixed VLAN is assigned to the respective switch port. Thus, the connected subscriber can only communicate within this VLAN.
Under certain circumstances, the problem of logical network separation can also be solved by the router. In some cases, the passenger Wi-Fi can be connected to the router or is already integrated into it.
The detection of the individual devices in the network is done via individual IP addresses, which are to be assigned at this point.
|Node||IP address||VLAN Member|
|Vehicle Communication Gateway||10.13.201.1||Management, journey data, video, Wi-Fi, ticket|
|Switch 1||10.13.201.3||Management, journey data, video, Wi-Fi, ticket|
|Switch 2||10.13.201.4||Management, journey data, video, Wi-Fi, ticket|
|Destination sign 1||10.13.201.10||Journey data|
|Destination sign 2||10.13.201.11||Journey data|
|Destination sign 3||10.13.201.12||Journey data|
|Passenger info 1||10.13.201.40||Journey data|
|Passenger info 2||10.13.201.41||Journey data|
|Ticket validator 1||10.10.201.10||Ticket|
|Ticket validator 2||10.10.201.11||Ticket|
|Passenger counting system 1||10.13.201.60||Journey data|
|Passenger counting system 2||10.13.201.61||Journey data|
|Maintenance access||10.13.201.250||Management, journey data, video, Wi-Fi, ticket|
To ensure the smooth functionality of the digital IP network on board our city bus, we include permanent network monitoring in the network design. In some cases, this is made possible via the on-board computer. Since the switch has a physical connection to each node in the network, diagnostics using a managed Ethernet switch are more effective.
Permanent monitoring makes sense for two main reasons:
- For troubleshooting
- Control over the running operation.
Managed Ethernet Switches can provide information about the network status using special protocols:
- ITxPT Inventory Service x-status: Monitoring is event-based. If an undesired event occurs, a message is sent to all nodes via DNS. The fault can be forwarded directly to the control center via the router. This function is suitable for keeping an overview of the entire vehicle fleet. It is essential, functionally relevant monitoring.
- Remote logging: All events that are logged in the switch are also forwarded to a remote server in the control center. Extensive monitoring and initial diagnostics are possible here.
- SNMP Trap: Error messages can be sent using the Simple Network Management Protocol.
Please check in advance which of these protocols your Ethernet switch supports.
To get a working network design for our line bus, we finally determine how to configure the whole IP network. The first thing to do is to clarify what mechanisms are available to make settings in the vehicle. The classic case of manually configuring each individual device or switch can be very time-consuming with regard to an entire fleet. A simpler option for this is offered by ROQSTAR Ethernet switches from TRONTEQ. A new solution allows all switches in a predefined network to configure each other. In practice this means that the configuration has to be done only once per bus and not per device.
In any case, when thinking about configuration, the entire fleet must be considered and not just a single vehicle.
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