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FOCUS: Use Of Extended C-Band With Mobile Antennas In India
by Paul Seguin, author, & Bhumika Bakshi, contributor, C-COM

From dial-up in the 90s to broadband connections in the early 2000s, and now to mobile satellite communications, Internet connectivity in the Asian sub-continent has evolved exponentially over the past decade. A growing demand for high speed Internet in the cities as well as in remote areas has led to an early penetration of satellite broadband in these countries.

C-COM entered the Asian market in 2005 when the Company sold its first iNetVu™ 1.2m mobile auto-pointing antenna system to Korea, followed by sales to other countries such as Australia, China, Japan, India, Malaysia, Indonesia, and Vietnam, to name a few. With huge populations in China and India, satellite communications is on the upswing and has an enormous potential for growth in these regions.

In mid 2008, C-COM received an order for six iNetVu™ systems from India. The order consisted of four Ku-band systems and two 1.8m extended C-band antenna systems with iNetVu 9000 controllers and high wattage transmitters (BUCs). Standard C-band is frequently used for broadcasting television signals, Internet delivery, data communication, voice telephony, and aviation systems. As it is less susceptible to rain fade than Ku-band, it is often used in tropical areas where heavy rainfall would interfere with standard Ku-band transmission.

Although Ku-band satellites broadcast at a higher power and higher frequency, this does not translate into more available bandwidth. In the past, VSAT operators migrated from C-band frequencies to Ku-band in order to benefit from smaller dish requirements, and lower equipment cost. Over time this trend has freed up bandwidth on C-band transponders, and thus now C-band is more readily available and typically less expensive.

Four of the iNetVu™ Ku-band systems were configured to be fully integrated with the Wavestream 25 Watt SSPA BUCs. This task required the iNetVu™ antennas to be modified to handle the Management and Control (M&C) features that were specific to the Wavestream BUCs. Physically, the iNetVu™ platforms could easily handle the size of the Wavestream BUCs, although a new method of attaching these BUCs had to be designed and developed.

The Wavestream BUCs have intelligence built into them and have the capability to provide a number of feedback features via a group of LEDs. Certain elements of their operational characteristics can be managed by discrete switches or by software using the M&C port. In an effort to provide the cleanest most user friendly solution possible, C-COM decided to design and build a Wavestream compatible rack mountable Power Supply with M&C port, LED display panel and control switches. This device was connected to the platform using a multi-conductor cable which provides for a very clean installation.

The platforms were configured and needed to be tested in-house for full functionality before they would pass the Quality Assurance (QA) checks. This presented a challenge as the LNBs used were designed for a frequency range used in India — this frequency was not readily available in North America. A decision was made to await shipment until the units preceding the order were fully tested in Canada. Following further investigations, it was found that by pushing the envelope slightly on the frequency range, we could test the LNBs for operational status.

The BUCs were also functionally tested and verified as were the BUC Power Supplies before the units were QA tested and prepared for shipment. When the systems were installed in India, all of the Ku-band systems were deployed with the client’s modem. The Ku-band systems were operating on a satellite where a DVB carrier was available that enabled smooth deployment of the systems.

Standard C-band is mostly used by SNG and TV operators and there is heavy employment of this bandwidth over existing satellites, whereas C-band linear extended transponders (often called Extended C-band) are more powerful and generally tend to be under-utilized.

In countries such as India where the climate is dominated by monsoons, convective thunderstorms are extremely common. Many satellite communication systems operate on C-band and extended C-band frequencies to minimize the rain fade effect and perform better under such adverse climatic conditions. On the other hand, clear weather fading can also affect the link reliability for satellite communication in a similar way as in rain or storm. C-band and extended C-band usually require bigger dishes due to lower density of signal but have the advantage of covering a wider geographical area and avoiding the need to double hop.

This was the first time C-COM had the opportunity to work with an extended C-band antenna system requirement that needed extensive customization by the client.

We were able to identify the wave guides for the extended frequency range for INSAT satellites. Our mechanical engineers custom designed a motorized polarization assembly to integrate the extended linear feed assembly. The polarization assembly then needed to be prototyped, manufactured, and tested with the 1.8m antenna. This entire process was completed within a month as it required only partial modifications from the standard linear C-band iNetVu antenna system.

The C-COM antenna controllers were designed to use one of three methods for locating the correct satellite. This particular client presented a situation whereby none of the existing methods could be used. The first method of finding the satellite that C-COM developed on their original iNetVu™ 5000 controller was the RF Search with modem confirmation. This method requires the iNetVu™ controller communicate to the modem in its native language, allowing the modem to confirm the satellite found was the correct satellite. While this method is deployed around the world with many users, in this case, due to the limitation of not knowing the frequency used until after the satellite had been locked onto, the modem could not confirm the appropriate satellite as correct.

The second method developed by C-COM was the DVB carrier method. DVB parameters are loaded into the on-board DVB receiver and through a custom software application, once the correct satellite is found, confirmation is given by the DVB receiver. In this particular case the satellite being used did not have a DVB carrier in the required band and polarity.

The third method uses DVB plus modem confirmation. As the client does not have an available DVB carrier, this method could not be used either. It was at this point that the engineers at C-COM had to look at an alternative method to “locate the satellite” for the client.

C-COM’s integration team began to investigate how to implement this extended C-band system solution, one that would allow the iNetVu™ 9000 controller to find the appropriate satellite the customer wished to use. Unfortunately, there was no DVB carrier in the extended C-band range. To use the RF with modem verification was not an option, as the particular modem the customer wanted to use was not yet integrated with the iNetVu controllers.

Given these were the only ways the iNetVu™ controller could locate the satellite, it was concluded that C-COM had but two options possible to make this system work. One was to integrate the iNetVu™ controller with a beacon receiver, and the second was to integrate the customer specific modem to work with the iNetVu™ controller. As beacon signals are not always unique, C-COM decided to pursue both options to assure system scalability and provide flexibility to the customer.

A technique exists in the satellite world of using a beacon signal provided by the satellite operator to allow remote clients to determine the attenuation or power of signals in such situations. A device that can lock onto this beacon signal is called a beacon receiver. It measures the RF input level of a signal with very specific electrical characteristics and provides this information to a control system. The main application of this device is in antenna tracking systems where the receiver provides the tracking signal level to the antenna controller. Other applications using this technique are used in pilot measurement and control loops such as uplink power control.

C-COM’s engineers integrated the iNetVu™ 9000 controller with a beacon receiver much the same way they would integrate an off the shelf satellite modem. They made it possible for the iNetVu™ 9000 controller to communicate with the receiver which would confirm to the controller that the receiver has located the required satellite.

The next step was to identify the modem the customer intended to use and gather all the parameters required to properly interface the modem to the iNetVu controller. Firmware and software was developed to allow the customer’s modem to interface with the iNetVu™ controller. This 1RU duplex modem covers virtually all Satellite IP, Telecom, Video and Internet applications. The iNetVu™ controllers now support two models of this off-the-shelf commercially available modem.

The customization for the system was not yet fully completed. After integrating the iNetVu™ controller with the modem, the engineers moved on to building a beacon receiver interface. This external 19-inch rack mount self contained 1U unit can detect the power density of the satellite beacon (930MHz - 2300MHz) and connects to the controller via an RS232 serial port interface. It has been integrated to work with all the iNetVu™ controllers.

The success of this project was that C-COM fully addressed the client requirements and added a Beacon Receiver solution as the fourth method to locate the satellite, the other three methods being RF, DVB, and RF/Modem. C-COM’s CTO, Bilal Awada says, “Our engineers have used their combined talents to come up with a unique solution for this specific application and we are very pleased with the outcome. It was a win-win situation for both of us. The customer got what he wanted and C-COM can now add two new integrated products into its product portfolio.”

To provide a comprehensive solution for the 1.8m extended C-band antenna system for India, C-COM used its in-house expertise in satellite RF, electronics, mechanical design, and software development. To ensure complete customer satisfaction, C-COM sent its RF technologist to the customer’s site in India to demonstrate both integrated solutions to the customer and to confirm the integrated solutions the customer was seeking worked as expected.

“This project, which was accomplished in a relatively short time, considering its complexity, confirms the flexibility of the iNetVu™ controller and the ability of the high quality engineering talent at C-COM. This team was able to create an imaginative and useful custom solution for this specific application which will be sold to many other customers’ world wide, who are looking for this type of flexibility. C-COM has received a significant follow up order from the same customer in India as a result of this effort, who was very impressed with the speed with which this solution was completed, the quality of the product he received and the ease of use of this unique custom application” said Dr. Leslie Klein, President and CEO of C-COM Satellite Systems Inc.

About the author
Paul Seguin is a Satellite Application Specialist with C-COM Satellite System Inc. Prior to joining C-COM, Paul spent 5 years working as a C-COM value added reseller, selling mobile and fixed systems throughout North America and the Caribbean. Paul has more than 18 years of communications experience which include developing software, hardware as well as communication and security applications for the Canadian Banking industry.

Contributors to the Article
  • Dr. Leslie Klein—President & CEO, C-COM Satellite Systems Inc.
  • Bilal Awada—CTO