Nothing epitomizes the global nature of everyday life quite like satellite communications. From video and television to voice and basic messaging services, it's the heart and soul of the drive to instantly access information, anytime, anywhere. While many attribute the shrinking world to the Internet, satellites have been steadily shrinking our world for decades. That said, though, it's the Internet that allows us to take full advantage of the terrestrial and satellite networks that span the globe. Furthermore, it's the Internet that will be driving much of the innovation in both networks over the coming years.
While the advances in terrestrial networks will continue exponentially, satellite systems, by their very nature, tend to advance somewhat more slowly. The issue boils down to cost. It's both a lot easier as well as much cheaper to add another fiber-optic trunk line than to put another satellite in space. As a result, bandwidth in space is like gold dust, and it behooves designers to make maximum use of whatever spectrum is available.
This has lead to many advances in higher-order digital modulation schemes, such as 8-level phase-shift keying (8PSK), that lead to greater overall data throughput and spectral efficiency. In addition, techniques like turbo coding, with a promised 50% leap in performance, are about to hit the mainstream. These technologies will go a long way toward lifting the bottleneck that satellite systems are facing as they try to compete with their terrestrial brethren.
In many instances, "compete" may be too strong a word to use, if not downright misleading. Except for the satellite TV (STV) versus cable war, which lately has escalated—thanks to recent FCC rulings—satellite companies are starting to see that more can be gained by complementing terrestrial networks instead of competing with them. This is evident by the recent activation of voice-oriented, bent-pipe, satellite constellations that can connect a caller to virtually every part of the globe, while taking advantage of the current cellular network when appropriate.
Whatever the satellite network, and whether it's for voice, STV, or the more-recent digital radio and data casting, the rising number of subscribers has had the effect of making the semiconductors within the devices almost commodity items. Combined with an overall shortage in RF designers, this has led to a demand for highly integrated, low-cost, off-the-shelf solutions that allow manufacturers to get up and running quickly with minimum overhead.
A perfect example of this cutthroat, low-cost approach to satellite communications is the STV business. With DirecTV (DSS based) and EchoStar (DVB based) now battling both each other as well as the cable companies, cost is everything when it comes to penetrating the home. Beyond that, quality of service and available options are the next big separators, relative to cable.
Success With STV
To date, DirecTV and Echostar have both had favorable reviews in the service department, and the recent FCC ruling that allows them to carry local channels has given them appreciable boosts. Current figures put the number of satellite subscribers at about 14 million in the U.S. alone.
The calling card of STV has been the digital quality of its video and audio, as well as the broader content, but this is now being matched by cable companies that are quickly deploying digital set-top boxes (STBs). Running off upgraded lines and headends, these raise the number and the quality of channels available in order to match that of satellite service. This has already slowed satellite penetration in places like Texas, where digital-cable deployment has been particularly aggressive.
Until now, a major disadvantage of STV has been the need for multiple low-noise blocks (LNBs) to facilitate the picture-in-picture and record-and-watch capability. This almost doubles the cost of a satellite system, as everything including the LNB, tuner, demodulator, and finally the MPEG-2 decoder must be duplicated. But, the satellite companies aren't outdone here. Both DirecTV and Echostar have instituted promotions that practically give the basic equipment away—assuming the subscriber signs a contract for at least one year's service. The newer equipment almost invariably comes with dual LNBs, so the subscriber only has to pay for the additional STB and any required cabling.
Even if the cost and quality of service were equal, STV still has two major advantages over cable. The first strikes to the core of what satellites are all about—reach! No matter where a subscriber is, satellite reception is almost guaranteed to be within reach. Cable deployment is still restricted to populated areas. Furthermore, even potential subscribers in populated areas are tired of the monopolistic practices of cable companies, which often don't face competition from other cable companies in their home markets. This monopoly doesn't sit well with subscribers, causing many to opt for satellite in the face of constantly rising costs.
This competition, and the rising numbers of systems being deployed, have affected chip manufacturers. For instance, tuner manufacturers are seeing a rise in demand. For every subscriber there are now at least two STBs, each needing its own tuner. This suits companies like Mitel Semiconductor just fine. Recently, it introduced the SL1935 single-chip, synthesized, zero-IF, quadrature down-conversion tuner. Covering the range from 950 to 2150 MHz, the chip is both DVB (950 to 2150 MHz) and DSS (950 to 1450 MHz) compatible. The device integrates a low-phase-noise PLL frequency synthesizer, a low-noise amplifier, and automatic gain control (AGC). The local oscillator (LO) and crystal reference are off-chip (Fig. 1).
The chip signifies the recent dramatic shift away from the typical "canned" tuners that have taken up so much real estate in both cable and satellite STBs. The high integration is essential if OEMs are to meet the price points and time-to-market requirements that STV providers are demanding.
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