A new generation of public transportation on-board computers is coming

New demands on the behavior of public transportation and mainly municipal public transportation vehicles require a changed conception of vehicle installation. To meet these demands the vehicle layout has to come closer to the standard computer environment. The new demands on vehicles applying mainly to modern checking systems, vehicle data collection, fast data transfers from/to the surroundings of a vehicle, and new functions of video calls or camera recording transfers change the current layout. A new generation of computers designed to perform all the above mentioned functions has to come to meet those demands and further develop the systems. The EPIS 4.0C system equipped with many of the above listed standard functions was created to meet the new demands on on-board vehicle technology.

New conception of vehicle data distribution

At the Czechbus exhibition in 2016, our presentation about the gradual change of information system installation in vehicles from the point of view of historical development took place. (link https://www.herman.cz/cs/produkty/clanky-2/clanky/komunikacni-systemy). This presentation described the contemporary state. In one year the demands on data transfers from transporters rose significantly. This included for example checking data (e.g. a database of several GB of photos), transfers of video recordings from vehicles, transfers of various logs (e.g. happenings on the CAN busbar of a vehicle) and records from vehicles (tachographs), passenger accesses to the public internet as a part of making public transportation more attractive, on-line advertisements or live news broadcasts (vehicles are directly connected to news servers).

At the moment many competitive tenderings for new arrangement of vehicle informatics and mainly control on-board computers are under way. The choice will affect the development of in-vehicle services for at least 10 years. For this reason it is necessary to choose the correct vehicle solutions applying to computer networks, especially when we want to use all the abilities of today’s technologies.

A fundamental scheme of a new system that meets the new demands can be seen in Pic.no.1. Public transportation vehicles are newly being equipped with 1 GBit/s busbars that we only know from fixed distributions in buildings. Is it necessary? We all know the standard computer distribution 100 Mbit/s. However, only a few know that thanks to the method of negotiation on busbars this Ethernet (100 Mbit/s) only reaches 30% of its effective communication speed, i.e. the real communication speed among devices will be about 30 Mbit/s. This speed is proving insufficient for really fast transfers, therefore overloads (losses) of communication can happen.

There is a simple reason behind this – wifi as per the IEEE 802.11 ac standard is required in depots now. This wifi’s communication speed is 1 Gbit/s or higher using a radio interface. If the wifi communication is to work in a reasonable fashion and use these speeds vehicles have to be equipped with suitable devices able to distribute this data current in a vehicle – i.e. Ethernet 1 Gbit/s (e.g. former wifi standards actually allowed max. 27 Mbit/s data transfers using the UDP protocol which really meant about 8 Mbit/s between a depot server and an on-board computer).

Another reason is using cameras displaying „real time“ pictures while a vehicle is backing up or while „on-trolleying“ of a collector is in progress which can now be displayed on the LCD of a driver terminal. If the camera shots are to be good and displayed to the driver with 100 – 200 ms delay and in a sufficient resolution it can mean sudden data currents of even 25 Mbit/s (simulating analogue signal). Such data currents limit the usage of other communications that can go via the busbar.

This also applies to the usage of LTE modems that are able to provide data currents of even 40 Mbit/s. Even in this case Ethernet busbar overloads can happen and the data current of the radio interface will be limited by the vehicle distribution. We could find even more reasons why vehicle busbars should be capable of higher speeds than those provided by Ethernet 100 Mbit/s.

A demonstration of such a situation can be seen in pic. no.2.

We have to realize that based on technical solution instructions of competitive tenderings large amounts of data will be created in vehicles in the future and this data will be stored on SSD drives. If the radio communication does not work (has difficulties) it will be necessary to perform reading/updates manually. If this reading is to be effective and not to limit the time of the manual operation a new type of updated USB 3.x will have to be available. In this way data reading/updates will be performed at speeds of a number of Gbit/s.

New types of checking

In cities and regions, new ways of checking are starting to appear that are based on new types of passenger controls based on photos contained in vehicles, black lists, white lists, etc… Vehicles have to regularly download checking information from „Data clearing centers“. For example the demands in the South Morava region are as follows – up to 500 thousand photos or white lists can be stored in a vehicle and the content of the databases in the clearing center can be 5-10 Gbytes of data. In a situation when the checking system has to be updated at once, this update can take a little under an hour when LTE is used or a couple of minutes if wifi as per IEEE 802.11 ac is used. If we want to really achieve this speed vehicles have to be equipped with 1 Gbit/s Ethernet busbars.

A new type of on-board computer has to be equipped with devices for quick data processing and performance high enough to find the correct photograph in the database and display it to the driver. Picture no.4 shows a possible layout of a checking system and clearly indicates that the „self-service“ passenger checking in validators outside of the place of the driver does not need a fast Ethernet busbar. The photo has to be displayed when the checking takes place at the driver so it is not necessary to spread the photo to other checking units in the vehicle.

The picture shows the checking section of a vehicle. Individual validators with ticket printers (e.g. when using the Plzeň card) or without printers (e.g. when ODIS is used) can thus be connected via a 100 Mbit/s busbar. The driver uses the checking unit in the front when selling tickets. There, passenger photographs are checked. There are multiple solutions ranging from connecting an independent validator to connecting individual validators directly to the on-board computer (a passive checking unit).

Passenger checking also triggers feedback communication from the vehicle – on-line communication with the backoffice where information is sent to the central office or it is sent to the communication central office and from there back to vehicles.

In this case the appropriate display size of the driver LCD terminal has to be chosen based on the number of tariffs – the 8“ (low number of tariffs) or 10,1“ (full checking) size is possible. An example of installation can be found in the following Picture 4.

What type of processor to choose for an on-board computer?

A competition is taking place in the field of processors for high performance calculations mainly between the PC-x86 architecture and the ARM (Advanced RISC Machines). From the point of view of high-performance processor usage the x86 architecture is still more efficient and it will probably remain more efficient for the next few years. It does not require support compilers (Cross compiler) i.e. optimized instructions applying to the speed of executing an instruction while this one can have more machine cycles.

Another reason for using the PC architecture (apart from its higher performance) is that if an application e.g. for searching connections can be run on a desktop PC it will also be functional on an on-board computer that is based on the PC architecture. Codes do not have to be changed and there has to be no translation into the language (assembler) currently used by an ARM processor. I.e. it can be used immediately without the necessity of rewriting (translating) it to the ARM processor environment. It will be easier to develop applications, however we have to take into account that applications can have issues with interfaces that do not occur on regular PCs (CAN busbar, IBIS busbar, etc.).

On the other hand, ARM processors can be found in almost all smartphones and tablets. These portable devices are versatile small computers that have applications written for them while their lifespan is counted in years in comparison with the x86 architecture (after such time the processor as well as the operation system are obsolete). ARM processors are not designed to achieve the highest possible performance that can be measured using FLOPS (operations with a movable point in a second). Instead of that, the important role is moved to parameters such as efficient processor construction, low energy consumption ensuring the longest battery operation time, minimum heat loss (to keep low operation temperature), low production costs and license fees (see below). In the case of public transportation vehicles a few watt lower power consumption (3W – 5W) is not an argument for using this type of processor considering the performance we would get.

The ARM philosophy creates independent software models in many variants so applications and operation systems have to be compiled specifically for a concrete architecture, a concrete programming environment and an ARM processor type. The disadvantage of the limited RISC command line is that operations such as calculations and dividing with a movable part cannot be executed in one cycle of hours but require at least a few.

Note: ARM type computer is a software model provided in a form of a license (for a payment) to individual processor manufacturers who add their own peripheries to this model (there are many SW models). The creator of this architecture is a British company called ARM Limited formerly known as Acorn. Although the ARM model started to be massively used in recent years the architecture itself is 30 years old.

New generation of on-board computers

To meet the above described demands a new generation of on-board computer has to be available. Their basic properties have to be:

• a permanent solution conception – it has to be able to perform all functions of the previous units without changing the installation in a vehicle – it is not necessary to change vehicle installation and „replace“ all the components.
• measurements identical with the previous on-board units so that placement does not have to be changed significantly and „electronics boxes“ do not have to be remade.
• a standard solution of on-board computers without ventilators and without the necessity of flowing surrounding air (there are computers without an inner cooler that require outer ventilators for casing cooling). There are industrial computers that require surrounding air to be flowing mainly in closed spaces
• the possibility of using multiple core (quad core) processors with significantly higher computing performance (each core can be utilized independently) equipped with up to 4 GB RAM memory – type DDR3. Such performance is necessary for solving quick data transfers (transferring required logs simulating tachographs, video processing, …)
• performance sufficient to process more than 10 camera currents including encryption – recordings from chosen cameras, video calls with the dispatching including secured camera recordings are possible. Thus in chosen solutions, the on-board computer can replace a camera system including meeting the requirements of the Office for Personal Data Protection.
• the possibility of connecting cameras for backing up or on-trolleying. 25 Mbit/s data currents are needed to process picture in real time (display delay 100-200 ms) which significantly burdens the 100 Mbit/s Ethernet vehicle data network.
• the possibility of using an internal SSD drive or MLC chips without the necessity of using significantly slower SD cards (250 Mbit/s). SSD drives are more reliable and can have communication speeds of up to 3 Gbit/s (given by the on-board computer) while the recent speed is about 600 Mbit/s (i.e. almost 3x faster). This solution significantly lowers the computer starting time to 35 seconds while keeping a full operation system. This brings the advantage of using various SW on the on-board computer without having to change the operation system.
• new modern interfaces: 1GB Ethernet (a necessity) and a USB norm 3.0 (for quick emergency data reading from the on-board computer) – they are again meant for quick data transfers.
• a unified interface for various radio station types – analogue, digital and TETRA including a 24V/12V convertor. Newly it is possible to connect all radio stations in Czechia to an on-board computer. This also includes a TETRA radio station interface. Interfaces for radio networks are suitable mainly for urban agglomerations as they ensure vehicle surveillance system functionality independently of mobile operators – a safe solution for cities in problematic situations.
• full preparation for checking at the driver – a new interface for checking at the driver consisting of a checking unit equipped with ticket selling (contains a printer), a bank and non-bank card reader, a QR code reader. Then the on-board computer contains a ticket sale transaction database.
• 2x video output with a resolution of up to 2560 x 1600 and an integrated high performance graphic unit.
• integrated unit – multiple use: contains an intelligent power supply unit, a digital annunciator, a command receiver, a GPS module, a modem for wake up frequencies of requested recording, a radio communication adapter and other previous properties of known on-board computer types.
• Integrated SW for controlling: information systems, checking, camera systems, vehicle preference, automatic throwing of the traffic route, reading tachographs, solving vehicle logs obtained from the CAN busbar, etc.

How to conclude?

If a really high performance on-board system capable of further development for at least 10 years providing that after this time there will still be a development environment i.e. it will be possible to perform further modifications in the program is to be used it is definitely good to choose (maybe multi core) computers based on the PC architecture with at least a 1Gbit/s busbar and a USB 3 interface. Those make it possible to better integrate more functions and ensure quick communication with the surroundings.

If a single purpose device with a limited number of functions without expected significant development is to be created some of the advanced ARM processor architectures can be used. It has to be taken into consideration that in the following years these systems may not be supported by processor and operation system manufacturers (it is an individual solution of a given processor manufacturer).

The decision which on-board computer solution and installation is more suitable has to be made by the user. The price difference can be a couple thousand for one device. Generally it can be said that the PC architecture is more suitable for municipal public transportation and the ARM type architecture is more suitable for regional public transportation.