Exploitable results
The aim of the Twister project has been to provide applications and services that meet the needs of user communities in rural areas. The following drivers and associated objectives have been identified at the beginning of the Twister project as key:
Objective 1: Provide content and applications adapted to the specific needs of rural areas.
Remote monitoring and control
Several such applications have been developed and deployed in different application domains. For the area of agriculture, Cemagref has developed an application for the remote surveillance of animals in loose housing as well as an application allowing to monitor and control the position of irrigation pivot's. Warsaw University of Technology has put in place a wireless sensor in an industrial production facility monitoring temperature, light and noise level. Both CNES and Warsaw University of Technology have put in place a web camera which can be remotely controlled allowing tourists to view onsite the environment at the site of Vianne and Hancza respectively.
Videoconferencing
Videoconferencing has been used by several validation sites in Twister. FORTH-ICS has used the Marratech videoconferencing tool to provide training on pre-hospital emergency care to 110 users on 10 different health care sites. The University of Malta has used videoconferencing to provide a 2 year Diploma course between October 2004 and June 2006 for students at Malta and Gozo. In addition, the schools of Vianne and Francescas have been equipped with webcams, loudspeakers, video projectors and video screens and a videoconferencing session between two classes has been organised.
Public internet access points
A number of communities have put in place public internet access points. DPZ has installed kiosks in the town halls of the villages. In the villages of Vianne and Ramonjuan an outdoor WiFi hotspot provides public internet access to tourists and guests respectively. Furthermore, in Vianne and Francescas the public at large had broadband access to the internet through self-service PCs in the town hall, tourist office or a cybercafé.
Web site development
CNES has developed a tourist web site for Pays d'Albret, the region in which the sites of Vianne and Francescas a.re located. Similarly, Warsaw University of Technology has developed a virtual pension web site to make room reservation for the guest house in Hancza. FORTH has set up a web portal in support of their tele-education on pre-hospital emergency care while Cemagref has put in place a contributory web site for the agricultural Twister users. Finally, DPZ has implemented a web site for Zaragoza as regional authority.
Objective 2: Investigate and validate in real operational conditions and on test beds the integration of DVB-RCS satellite solutions with wireless terrestrial technologies.
Based on the user and service requirements expressed by the Twister site coordinators a number of generic hybrid satellite-wireless network architectures has been designed, validated and implemented allowing to propose different solutions for different types of users:
1. Institutional users: employees of institutional bodies such as town halls, public libraries, schools, tourism offices, cultural houses, agricultural chambers, universities, hospitals, etc.
2. Business users: employees of private SMEs.
3. Residential users: citizens connected either through a public Internet access point (kiosk) installed for instance at their town hall premises, or through a dedicated connection at home.
4. Guest users: in general, laptop users visiting the validation site in an occasional way (meeting, tourism, ...), connected through the intermediary of a hotspot access point.
A broadband access solution that is highly scalable and easy to deploy, is a key factor for the success of broadband internet service in rural areas. Satellite technology provides reliable, fast but expensive connectivity. Therefore, the ideal way to use satellite systems for internet access is to combine them with other technologies to provide local shared access. The Twister system is a hybrid satellite-terrestrial wireless network solution which allows share the immediate and far-reaching connectivity of satellite solutions between multiple users through a wireless local loop.
The Twister solution consists of three main components:
1. Satellite component
A total of 105 satellite access points (SAP) have been deployed of which 69 have been combined with local loops. Picopoint AAA services have been deployed and activated for 24 kernel validation sites. After the Twister project 41 satellite access points remain operational, representing around 40 % of all deployments. The sustainability of the services has been ensured through the creation of partnerships between on the one hand regional authorities and user representatives and on the other hand services and technology providers.
2. Security, management and monitoring component
The Twister project has identified and analysed the latest security techniques at different levels of the protocol stack and studied their interaction with the aim of ensuring a complete and end-to-end security over the hybrid satellite-wireless network. The key issues that have been addressed are:
- protection against security attacks from the internet
- wireless network security
- virtual private networks
- user authentication, authorisation and accounting.
Different QOS mechanisms and equipments have been investigated and validated to ensure an efficient use of the satellite and wireless network resources. The solutions that have been selected allow to manage the bandwidth so as to ensure that critical applications receive high quality service and to allow to fairly share the bandwidth between different users.
Different levels of priority can be allocated depending on the type of user, type of protocol or type of day. For each QOS class the following parameters are controlled: guaranteed / maximum bandwidth, priorities, number of connections. On the Twister sites, peer-to-peer traffic is controlled so as to avoid it monopolising all the resources.
3. Wlireless network component, including wireless backbone and user segment
Objective 3: Develop and validate a system monitoring and evaluation methodology allowing to quantity key parameters for network sizing such as resource utilisation at different points in the network topology or end-to-end quality of service.
Major efforts have been concentrated on the usage and evaluation of sites. The 105 satellite access points deployed have totalled more than 1500 months of cumulated operations which has led the Twister project to obtain a significant and representative database of more than 40 gigabytes of statistics on the usage and reliability of the hybrid satellitewireless networks.
A first level of analysis and synthesis of this enormous amount of data has been made through the statistics reports for the kernel sites. More than 72 statistics reports have been generated quantifying and synthesising for a given period, between three and six months, the day to day usage of the site based on data collected by the Twister technical partners and by the different network equipments, Following processing and analysis the following key parameters are extracted and reported upon such as distribution of usage between users or groups of users, daily, weekly, monthly usage profile, protocol distribution and network problems. These reports have allowed to adapt the equipment configurations to the evolving needs of the end-users and have been correlated with the feedback and information obtained by the site administrators / site coordinators.
Objective 4: Complement ESA activities on interoperable terminals by validating the perfomance of these terminals at application level in a real operational environment.
The IP Access and IP Connect services provided by Eutelsat/Skylogic in Twister use a Viasat solution with Linkstar user terminals. Again, the equipments deployed in Twister are based on a hardware / software release prior to certification of the Viasat equipment by Cetecom and could not be upgraded to be DVB-RCS compliant, Eutelsat did not consider it feasible within the budget and planning constraints of the Twister project to upgrade the hub to allow operations with certified Satlabs terminals.
Although no interoperability at transmission layer / MAC layer has been achieved, the project has demonstrated the behaviour and performance of different types of applications (web browsing, file transfer, streaming, P2P, VOIP and videoconferencing, etc.) over different types of terminals and services packages from different vendors and operators. In addition to the Aramiska/ Ouranos networks and Eutelsat solutions which have been widely deployed on 105 sites in total, Ansur and EADS Astrium have tested in a laboratory environment VOIP and videoconferencing applications using respectively the STM Satlink 1000/1910 terminals in combination with an STM hub from Telenor and the Newtec integrated POP IDU terminal in combination with the Newtec hub belonging to Belgacom.
Objective 5: Improve the use of satellite capacity. Potential techniques that have already been identified are multicast protocols adapted to satellite environment intelligent caching mechanisms or higher coding/modulation schemes.
Techniques to increase the performance of the satellite link have been successfully addressed include:
- layered IP-SEC solutions such as ML-IPSEC allow to combine end-to-end security with high throughput achieved by PEP mechanisms.
- multicasting solutions adapted to the satellite environment such as the S-MRP protocol allow to make more efficient use of the satellite bandwidth.
- the use of adaptive coding and modulation (ACM) over DVB-S2 on the forward link allows a very high gain on system capacity and availability. On the return link several Fade mitigation techniques (FMT) have shown good potential of which uplink power control (UPC) is the most simple to implement.
- a split multilink solution allowing to distribute traffic between two satellite terminals in function of the traffic load has been validated.
- The Twister project has investigated how DVB-RCS traffic priority mechanisms can be used for supporting IP QOS in general. The concepts have been tested and validated using VOlP as a key application needing efficient QOS.
Objective 6: Define and disseminate a set of technical and quality guidelines for resellers on the installation and exploitation of DVB-RCS services.
Following each validation site installation, EADS Astrium and its partners reviewed the quality and delay of the installation. The following conclusions and recommendations for a successful and efficient deployment of hybrid satellite-wireless networks a.re being proposed:
Before installation:
- ensure the completion of technical prerequisites
- on-factory tests before the delivery of equipments on-site.
During the installation
- ensure the presence of users at their locations, so that they can provide logistic support if necessary to the installers (access to premises, provision of ladders, telephone access, etc.)
- distribute to users guidelines on PC / CPE configuration parameters.
Following on-site installation
- network acceptance test review on two levels: equipment level, testing the correct operation of each equipment and network level, testing the end-to-end operation of the deployed network.
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