The 21Net system enables Internet services on board high-speed trains. The system uses several communication technologies to access the internet: cellular, WiFi and satellite. A Mobile Access Router manages the links switching from one to the other depending on their availabilities. The goal of the project is to improve users ‘experience of the current system by optimizing the bandwidth usage.
The goals of the project are:
1) To improve users ‘experience of the current system by optimizing the bandwidth usage
2) Use a more efficient satellite technology permitting the use of the Adaptive Coding and Modulation (ACM) in both the forward link and the return link
3) Improve reacquisition time of the satellite system (modem) after long shadow zones
4) Develop a more robust TCP and HTTP acceleration system able to handle link with high delays but also to cope with the type of traffic generated by the users
5) Implement Quality of Service (QoS) management in order to filter unwanted traffic
6) Aggregate links of different nature (delays) in order to make them acting as one single link, getting away as much as possible the link per link management
Users and their needs
Users targeted are in Belgium/France/Netherlands and Germany (Thalys) and U.K (Caledonian Sleepers)
Service/ system concept
The system is composed of three key subsystems: the communication element in the train, the HUB and the backend.
The train subsystem is composed of:
- The wireless backbone
- The ACG: Access Control Gateway, It provides major functionalities to permit the customers to access the system
- The MAR: Mobile Access Router managing the access technologies
- The ACC: The Accelerator optimizes the TCP IP connection efficiency even with high latency link
- The Satellite modem/Cell/WiFi: used for the connections towards the Internet
The back end is composed of the coupled element of the MAR and the ACC.
The project is addressing the following features:
- Migrate from the current Constant Coding and Modulation (CCM) of DVB-RCS transmission system to the Adaptive Coding and Modulation (ACM) scheme, in order to provide more bandwidth and more cost effectively transmission
- Improve the performance of DVB-RCS in the harsh railway environment
- Develop a new Mobile Access Router that will convey the data packets from the train towards the Internet through link with heterogeneous end-to-end delay, maximizing the utilization of each of the available link
The MAR implementation has been performed in three successive stages:
MAR 2.0: To bond link of the same nature (cellular, WiFi)
MAR 3.0: To bond link of different nature (satellite, cellular, WiFi) using a packet switching technology
MAR 4.0 To bond link of different nature (satellite, cellular, WiFi) making a major step forward in terms of performance. MAR 4.0 embodies all the experience accumulated over the EOMST experimentation and testing in live conditions. It integrates packet-switching through a Multipath TCP (MPTCP) with major improvements based on TCP tunneling between TCP proxies residing at both ends of each link.
Space Added Value
Satellite communications complement the use of mobile network technologies increasing the availability and offering competitive solutions complementing terrestrial technology or replacing it when not available.
The main benefits for 21Net and its customers would be:
- increasing the availability of the “Internet on board” service: providing good services take only all its essence when the service is available. It is always better to have a system with slightly less functionalities but with higher availability.
- increasing the final user experience: the goal of this service is to offer to people the feeling they are still at home or the office when travelling and to fill up the disconnection they could experience when travelling on trains. With time, Internet and remaining connected has evolved from a service to almost a need. Getting closer to this homelike experience is something which isn’t achieved yet;
- increasing the ratio capacity/price: as said before, the Internet has become a need, getting closer and closer to gratuity is a must. In order to achieve this goal, developing or using more efficient technics for coding and sending information is a must.
The 21Net system architecture relies on two-way Ku-band satellite transmission to provide connectivity between the internet backbone and the train. The satellite operator selected for the project is Hispasat.
The system is composed of three key subsystems: the train, the HUB and the backend.
The train subsystem is composed of:
- The AGC: the AAA unit of 21Net system contains the captive portal.
- The MAR: Mobile Access Router managing the access technologies.
- The ACC: the Accelerator optimizes the TCP IP connection efficiency even with high latency link.
- The Satellite modem: main unit used for the connections towards the Internet.
- All these components have corresponding components on shore: in the satellite HUB for the satellite modem and in the backend for the others units (MAR, ACC). The ACG is a specific case.
The project proposes to address the following components:
- ACC: Improvement of the efficiency “acceleration system” to cope with the satellite link with algorithms focussed on the application used on the system.
- Bonding router/technology: one of the goal would be to bond link of different access technologies ( cellular and satellite, WiFi)
- Satellite modem: by the use of a new modem (iDirect) we expect to succeed in using ACM technology in both the forward and the return link at an improved ratio cost / bit.
- Filtering system: by installation an application based filtering system. Application highly consuming bandwidth will be filtered to leave bandwidth for other more applications.
Initially, the multilink router, satellite modems are building blocks sourced from third parties.
However, due to some technical limitation, the performance of the bonding of links of different natures were below expectations. Consequently, it has been decided to extend the development of the development to incorporate a new Mobile Access Router that allow an effective concurrent use of all available links. This development implies a redesign of the arbiter and the mobile multilink router. The picture below depicts in a simple way the principle of the product.
A link would be, in the context of our applicationm, cellular, satellite or WiFi.
As a results of the development, the end system architecture is depicted on the pitcure here under. The architecture remains globaly the same, the Arbiter and the Multilink router are replaced by the MAR3.0.
- Making ACM work in both FW and RT link in a mobile environment with frequent obstacles
- By nature cellular and satellite link are different, it will be a challenge to make them work together with generic components sourced from third parties and thus for whom there is limited possibility of customization to fit the specific needs of mobility on high speed trains (Multilink router, satellite modem).
- Organising a pilot fulfilling all the prerequisites can also be very challenging in a railway environment.
In the first project phase was successfully held on a train of the Thalys fleet between the April 2014 and May 2014. The results confirmed the correct functioning of the system. The availability of the service has increased by 5%. The biggest improvement has been made on the routes with a better cellular coverage. This shows that the bonding (only available between links of identical nature) technology helps significantly to increase service availability. The offered average bandwidth on trains has also been increased by 30%. Eventually the price of the satellite capacity had also decreased thanks to the more efficient satellite technology (ACM).
A second pilot was successfully held on a train of the Thalys fleet between October 2015 and January 2016. With a system availability average of 99%, the pilot was demonstrating that the new system is capable to satisfy the expectations of the customer in terms of Internet availability. The data collected during this time have shown a very good performance of the Internet Service on Thalys trains with values in most of the cases steadily over target. The results confirm the good working of the system. The bonding (working between links of different nature) technology helped significantly to increase the service availability compared to previous solutions. The offered average bandwidth on train has also been increased.
In the third phase of the project an enhanced Mobile Access Router (MAR 4.0) is under design.
The project has passed the Factory Acceptance Tests (FAT) in November 2017. A first trial on a Caledonian Sleepers train is expected in April 2018.