Take a Trip on a Train
Unique challenges in serving the emerging railroad segment include high voltage overhead electric power cables, speed and vibration, accelerations, and terrain blockage. But Ku-band on-the-move technology is being deployed to bring broadband to trains moving at up to 320 kilometers per hour to allow onboard Wi-Fi hot spots for passengers. For the past few years, National Express, a U.K.-based rail service carrying 18 million passengers per year, has offered onboard Wi-Fi using a hybrid 3G and a 4 megabit-per second satellite downlink provided by Icomera of Sweden. Also in Europe, 21Net of Ledbury, England, is delivering broadband to trains via Ku-Band on-the-move VSATs. It teamed up with Nokia Siemens and Telenet to implement the ThalysNet service on Thalys’ TGC high-speed train network between France, Belgium, the Netherlands and Germany. A first for North America, VIA Rail Canada, Canada’s largest rail operator, recently replaced its terrestrial delivery network for broadband on passenger trains running between Windsor, Toronto, Ottawa, Montreal and Quebec City with a satellite-based solution from 21Net.
Moving Forward
Near-term growth in some of the exciting new consumer-driven on-the-move entertainment and broadband applications coming into the fore could be slowed by current automotive and airline industry problems. But there is no question that on-the-move is generating significant new demand for commercial Ku-band satellite network solutions and bandwidth. It is also bringing promising new ground systems technology and innovations into commercial markets.
On the Move Technologies
Innovation in the design of low profile, lightweight and low-power-draw amplifiers has helped make on-the-move services via Ku-band more viable. A case in point is the solid-state power amplifier (SSPA) and block-up converter (BUC) technology found in on-the-move systems from TracStar, SeaTel, RaySat ThinKom and others. Technology supplied by WaveStream of San Dimas, Calif., employing the company’s patented spatial-power combining technology, allows WaveStream to deliver uplink amplifiers that are about half the size and weight of comparably rated SSPAs while drawing about one-third less power of conventional Ku-band SSPAs. “In many systems, the difference between a solution that will or won’t operate or make business sense is an issue of the temperature, size or weight,” says Gary Echo vice president of business development for WaveStream. “We overcome that challenge with our Ku-band technology.”
- An Array of New Antenna Options
Electronically steerable phased-array antenna technology, long-used in military space applications, promises flat panel antennas – perfect for low-drag or low-profile on-the-move communications, but opinions differ on its commercial viability. According to Bill Milroy, chairman and CEO of ThinKom of Torrance, Calif., “People are working on low-cost phased arrays, as are we, but there are two problems. First, they are too expensive. Second, they are not very efficient. You have to use a lot of area to get the same performance.”
ThinKom is bringing to market what it says will be the most efficient low-profile, commercial, two-way, on-the-move antenna system on the market. The ThinSat300 antenna will offer a 40 percent to 65 percent lower profile and 4 times to 10 times higher spectral efficiency than competing on-the-move products, ThinKom says. “Only 11 centimeters high, it can deliver comparable performance to a typical 90-centimeters by 50-centimeter parabolic dish,” says Milroy. “Also, because of its efficiency, low sidelobes and very narrow beam width, no signal spreading is required even at Ku-band.” The product, which goes into beta trials in cars and SUVs later this year, uses a variable inclination continuous transverse stub (VICTS) array technology, proven at X-, Ku-, Ka-, Q-band in years of military applications. The VICTS array is 100 percent mechanical anduses a stack less than 11.5 centimeters high of two circular metal-coated plastic plates which rotate.
Zachi Bejerik, CTO of antenna manufacturer Commtact, agrees that phased array technology is too expensive. “Until phased arrays are mature — probably several more years — and until it introduces good efficiencies, we believe our reflective technology is the best in terms of performance and price. We see the market ranging from $125,000 down to $40,000 to $45,000 for considerable quantities of terminals, and this is where we come into the picture.” An advantage of Commtact’s reflector and feed array approach compared to phased array-based products is that converting from Ku-band to Ka-band only requires replacing the feed.
Another technology seen as important in getting the most efficient usage of capacity is DVB-S2 with ACM (adaptive coding and modulation). On top of the 30 percent improvement over DVB-S systems, a gain of 50 percent in bandwidth efficiency is possible by adding ACM to DVB-S2 systems, manufacturers say. With ACM, a specific VSAT in a broadband network can adjust its transmit data rate on-the-fly to accommodate its site-specific link parameters. “This can be very useful for maritime where you often have bad weather, and have ships in different areas,” says Deasington.
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