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Satellite Connections

By Charlotte Gliddon-Bush

New technology from Chronos Technology Ltd. will allow utilities to receive SCADA telemetry and measurement data via a low earth orbit satellite network. The technology provides a secure method for transmitting data and offers a cost-effective solution for utilities operating in remote areas.

In October 2001, Chronos Technology Ltd. released the MiChroSat remote satellite terminal, a satellite data modem and application interface which works over the low earth orbit (LEO) satellite network. MiChroSat was developed to provide a cost effective, reliable data transfer solution that can be deployed in areas that are not currently served by existing technology.

The technology is suited to utilities needing to take meter readings or monitor substations in remote locations where there is no global standard for mobile telecommunications (GSM) network coverage. It can also be attached to electrical poles to detect faults in the distribution network.

Geraldine Beaufils, marketing assistant at Chronos Technology commented on the benefits of MiChroSat as an alternative to traditional communication services: “In the past, collecting data from a source which is outside the GSM coverage was a costly and time consuming exercise, often involving site visits or diverse communication technologies. Now with MiChroSat, it is quick and easy to deploy, fully automatic and very cost effective.

“MiChroSat is particularly useful for monitoring systems where data integrity and receipt of alarms is critical to the operational quality of the network. An example of this would be meter reading on a pipeline where data from the flow meter is used for billing generation, security and availability would then be critical,” she added.

This system will help utilities to meet the current legislation which requires them to have a diverse routing for communications. MiChroSat can therefore be used as the main communications system in remote areas where running several terrestrial telephone lines will be expensive, or as a secondary communication system for companies looking for a cost effective method for diverse communication routes.

“The MiChroSat should be able to replace expensive leased lines from terrestrial telephone companies with a more cost effective communications system. It is easy to deploy as it can be fitted within half an hour and gives utilities an independent means of communicating,” said Charles Curry, managing director of Chronos Technology.

A reliable service

Although the Globalstar and Iridium LEO satellites have been around for some time now, they have only become commercially available in the last two or three years. Until now the satellites were used for satellite calls and global roaming via mobile telephones. Chronos is the first company to be able to use the satellite network for telemetry or remote data services.

Figure 1. The typical MiChroSat network configuration
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“We have been in discussions with the LEO companies for the last two years to evolve their service into a data service,” said Curry.

Chronos decided to develop the technology after several requests from its current customers which were using traditional geostationary (GEO) satellite communication systems such as VSAT. These customers required a reliable data transmission service that could be used in remote locations where GSM coverage was not available. Some companies also required coverage of a number of different locations, so the product needed to be a more cost effective solution than the ones that were available at the time.

Curry explains that because the MiChroSat is small, it is less expensive for the customer: “It is so cost effective because it is much smaller than traditional VSAT systtems, roughly the size of a hardback book instead of a large satellite dish. LEO technology is inherently less expensive than GEO since it utilizes much lower frequencies which need less expensive components.”

Another of MiChroSat’s benefits is its ability to detect faults on electrical power lines. Once a fault is detected, MiChroSat can immediately send back an emergency alert to a utility’s headquarters, allowing it to dispatch a repair team and minimize outages for customers, and will, therefore, save time and money for the utility.

After contracts were signed with the LEO companies, the MiChroSat took six months to develop and is now available to customers almost on demand. Chronos is seeking its first commercial contract and is keen to work with utilities to implement its first project: “We would be offering MiChroSat almost as an off-the-shelf solution after the customer has evaluated if the application works well with the communication system. We would work with them through this process,” said Curry.

Figure 2. MiChroSat can help utilities retrieve data from remote locations cost-effectively
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The MiChroSat can be put in any location, although Chronos is currently focusing on the European market where the LEO satellites have 100 per cent coverage. It can be used in 18 countries, but current coverage is best in western Europe.

Although it cannot be placed inside a building, the MiChroSat is able to withstand harsh climatic conditions, and unlike VSAT solutions, it is unaffected by rain because of the lower orbit satellites. It is protected from the elements via an ABS plastic IP-65 enclosure, and reinforced polyester street furniture-type bollards are also available for further protection.

Transmitting data

MiChroSat uses the Globalstar and Iridium LEO satellite networks which are comprised of a constellation of mini satellites in orbit approximately 1500 km from the earth. They cover most of the earth’s surface ensuring that there is always more than one in view.

When making a call to transfer data, several satellites receive the call simultaneously via either the Globalstar system or the Iridium satellite network. Globalstar currently has 48 satellites orbiting the earth, covering 80 per cent of the earth’s surface as well as four spare satellites. Several of these, or Iridium’s satellites, are used to ensure transmission continuity and that the is call is picked up first time.

Figure 3. MiChroSat will be delivered as an off-the-shelf communications solution
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If there were any interference blocking the signal to one satellite, the signal will simply be picked up by one of the other three or four satellites focusing in on the area.

The call is transferred using code division multiple access (CDMA) to provide a soft handover if the satellite moves out of sight. The LEO satellites then use the ‘bent pipe’ principle to transfer the information down to the receiving customer’s earth station.

The bent pipe principle involves a single relay scheme in which a terrestrial-based signal is sent to several satellites which then relay the signal via CDMA technology to a satellite dish at the appropriate gateway. The call is then routed locally through the terrestrial telecommunications system.

LEO technology

MiChroSat communicates using the IP protocol either via the internet or a private intranet circuit. When it has application data to send back, MiChroSat establishes a dial-up connection to its host’s gateway, which is operated by the service provider, and then establishes a PPP session with the gateway.

The PPP provides a standard method for transporting packets of any protocol over a point-to-point link. It encapsulates network packets into a format suitable for a serial link.

The application data is then transported using either FTP, TFTP, email, Telnet or any of the other methods within the IP protocol, straight to the customer’s secure server either via the internet or a dedicated intranet connection. If the customer prefers, the data can be delivered and hosted to Chronos’ own servers and accessed via customer dedicated secure web pages.

The MiChroSat remote satellite terminal is a modular system which consists of a data acquisition engine and a communications module. Due to the unit’s unique configurable data acquisition and delivery engine, it can be configured to meet any customer requirement.

Thanks to its configurable nature, the data acquisition engine can be easily interfaced directly into existing applications without the need for expensive firmware or hardware modifications. Multiple-vendor hardware can also be integrated into the delivery engine and the data can be delivered from each site in an identical manner, reducing the need for multiple data acquisition and management systems.

The MiChroSat terminal is designed to be powered via a 12 V DC supply, and in remote locations Chronos can supply either a one year battery or a solar/wind power solution to meet power needs.

Chronos will also supply an expendable maintenance service on a next day replacement scheme with a 24 hour-a-day, 7 days-a-week technical help desk. An installation service could also be included in the contract. Curry explained further: “Chronos will supply the complete solution, supplying the total turnkey communications link. All the customer would have to do is install it, but we could even supply an installation service as well.”