Basic Satellite Technology

There are two primary satellite systems in use today: geostationary and low earth orbit (a third, middle earth orbit, is less common). Low earth orbit (LEO), due to its proximity to the Earth's surface, requires considerably less power for transmission, both to and from the satellite. Commercial enterprises, such as Teledesic, intend to use LEO systems to provide high-bandwidth Internet connectivity to areas of the world not readily serviced by terrestrial networks. LEOs can also be used for handheld mobile telephones in any location where there is a reasonably direct line-of-sight to the satellite.

This post focuses on geostationary satellite systems. Satellites in geostationary orbit appear to move only slightly in the sky, hence the term "geostationary." Flying high at 35,800 kilometers (22,000 miles), a geostationary satellite orbits the Earth in the same amount of time it takes the Earth to revolve once. From Earth, therefore, the satellite appears to be stationary, always above the same area of the Earth. The area to which it can transmit is called the satellite footprint.

Exhibit 1 is a simplified diagram of a typical geostationary satellite system using small receiving (end user) VSAT dishes.

Exhibit 1: Geosynchronous Satellite System

Advantages of geosynchronous satellite systems include:

  • Quick to deploy at field locations. Once agreements with the satellite and hub providers are in place, additional VSAT dishes can be installed within a few days. Terrestrial lines, on the other hand, can require months to install, depending on the carrier, location, and other logistical factors. Some organizations have mounted VSAT dishes on flatbed trucks so that they can be set up quickly; they can then be moved to another location.

  • Only practical solution for very remote locations. For example, in the natural gas industry, pipelines must be run across thousands of miles, some parts of which may be ten to hundreds of miles away from the nearest telecom point of presence (POP). In those cases, satellite transmission of technical data (e.g., pipeline pressure and flow) is the only reasonable way to monitor the pipeline. Similarly, some rural locations cannot get terrestrial services (other than ordinary telephone service) because their usage does not justify the high investment required by the local telephone company to run the conduit.

  • Low cost relative to terrestrial lines. In many cases, satellite communications will cost one third to one half that of its terrestrial counterpart. One-way video, in particular, is drastically less expensive than alternatives because of the satellite's ability to carry broadband transmissions. Sometimes, satellite communications are used solely as a backup in case terrestrial lines are down.

    Exhibit 2: Sample Costs to Transfer Internationally 600 Megabytes to 10,000 Subscribers


    Transmission Rate (Mbps)

    Transfer Time

    Transfer Cost (U.S. $)

    Telephone line


    2 days




    12 hours




    1 hour




    20 minutes




    2 minutes


  • Works when parts of the public network are down. As recent world events have reminded us, a temporary slowdown in the public switched telephone network is often a consequence of high-visibility disasters. Telephone lines and cellular phones (which ultimately use terrestrial lines) become swamped. In contrast, VSAT dishes need only electrical power and a clear line of sight with the appropriate satellite. They are unaffected by congestion on the public network or any circuit/equipment breakdown in the POP itself. The one exception to satellite independence from terrestrial carriers is the need to use conventional lines for the backhaul circuit.

  • Capable of efficiently multicasting text, images, video, and audio over large geographic areas. In contrast, multicasting via terrestrial lines often equates to repeated transmissions of the same information, wasting valuable band-width. Note that multicasting is a one-way, one-to-many medium.

  • Bypasses Internet congestion points when used for Internet transmissions.

  • Only one or two providers needed for end-to-end international communications. For terrestrial leased line management of international connections, each individual carrier usually manages its segment of the link. A satellite connection, on the other hand, may use only a single supplier who is responsible for the quality and management of the international backbone connection.

Disadvantages include:

  • Weather interference. Bad weather (discussed in detail later) can disrupt satellite communications. Heavy rains, ice storms, and even the vernal/ autumnal equinox can sometimes disrupt the signal.

  • Propagation delay. Geosynchronous satellites must be positioned so high above the Earth that even traveling near the speed of light, signals do not instantly traverse from end to end. Voice carried over geosynchronous satellite, while still used for mobile communications such as Inmarsat satellite phones, is considered inferior to landlines for routine business communications. The one-half to one-second delay is disconcerting for most individuals who are used to the full duplex mode of the traditional public network (i.e., both parties can talk at the same time, without delay). From a data communications perspective, this limitation makes both Internet access and highly interactive applications unsuitable for routine use over satellite links.

  • Limited two-way bandwidth. While video "downlinks" from the satellite are carried over a large bandwidth, uplinks (from the VSAT dish to the satellite) are narrowband (typically 64 to 256 kbps).

Call Centers

There are a number of technology solutions that can reduce overall organizational costs, even if they add slightly to the telecom budget. Call centers provide one such solution.

Call Centers

Although call centers would be an obvious choice for heavy massing of technological firepower, many organizations still rely too heavily on human agents to do work that could be done by computers and telephone systems. Examples include:

  • Predictive dialers. Anathema to families that enjoy a quiet dinner together without telemarketer interruption, predictive dialers allow agents to call efficiently. Not only does the predictive dialer actually make the call, but it "uses complex mathematical algorithms that consider, in real-time, the number of available phone lines, the number of available operators, the length of an average conversation and the average time operators need between calls, and constantly adjusts their dialing rates based on these factors." Also, the best predictive dialers screen out calls where there is no answer or those that are answered by an answering machine. Most of the time, the calling agent hears a quiet "zip" in the headphone and a live person is then on the line. While manual dialing may result in 15 to 20 minutes of productive calling time per hour, predictive dialers allow agents to productively talk 40 to 57 minutes per hour. Given that call center agents are paid between $12 and $20 per hour (as well as incentives), any device that makes them more efficient is likely worth the investment. It is interesting to note that, in the eternal war between "push" or outbound call centers and potential customers, technology solutions are found on both sides. Telemarketer "zappers" are now sold that intercept telemarketing calls. In Texas, some 77,000 households have signed up for a blocking service since the law went into effect on January 1, 2001.

  • Call center workforce management software. Although scheduling agents via software would seem to be a "nice to have," akin to a deluxe PDA, it strongly affects call center costs. Beyond a certain number of agents, it becomes difficult to mentally juggle schedules, demand, holidays, incentives, shifts, etc. One of the highest expense items is overtime; without an automated system for scheduling and reporting, absenteeism and overtime will climb to unacceptable levels (for mid- to large-sized call centers). Steven J. Cain, Gartner Group's Call Center Benchmarking Practice Research Director, says that, "When you consider that, in some industries, contact center turnover reaches as high as 50 percent, there is significant opportunity to reduce turnover, building an experienced and tenured agent base to deliver the highest quality customer interactions while minimizing the expense of recruiting, training and productivity shortfalls while getting up to speed."

  • Interactive Voice Response System (IVR) The familiar "press 1 for account balances, press 2 to transfer funds," is the public face of interactive voice response technology. Some call centers shun IVR systems because of the acknowledged public preference for human interaction. This philosophy should be reconsidered in some cases. For example, is it better to staff from 7 a.m. until 10 p.m. and then leave a message for the customer to "call back during business hours" or to have an IVR after-hours that provides the customer with some useful information. Second, as the public becomes more familiar with IVR, there are situations where non-human interaction is faster and preferred. For example, when people call about booking reservations for deluxe resorts, they want to talk to someone and ask multiple questions. However, if they must cancel those reservations, they merely want to cancel — why take the time to explain? In this case, the transaction can be handled without agent contact, saving money for the company and time for the customer.

Digital Subscriber Line (DSL)

DSL (digital subscriber line), cable modem, and other high-speed technologies should be considered in areas where they are available.

DSL services are growing rapidly as local access carriers continue to install DSL access modules ("DSLAMs"). Most service providers break down their DSL services into three main categories: residential, SOHO (small office/home office), and enterprise. ADSL (asymmetric DSL, where up- and downstream speeds differ) appears to be the offering of choice for residential customers, while SDSL (symmetric DSL) is usually marketed to businesses because it has T1 or more speeds both ways.

Depending on the geographic location, installation time for DSL circuits can range anywhere from one week to over ten weeks. Quality of service (QoS) is an issue. Most service providers, because of the multiple risk factors, do not guarantee QoS with DSL service. For example, DSL can potentially be unavailable for a few hours or longer. However, unlike cable, DSL provides consistent bandwidth to the user and does not depend on how many other (unrelated) customers are using the service at any one time.

DSL, more prevalent than cable modem, has a number of potential advantages:

  • Internet access for smaller offices.

  • Backup Internet connection. Many organizations implement DSL as a fail-over device because it is so inexpensive compared to a T1. Although costs vary by provider, a business typically pays at least twice as much and sometimes three or four times as much every month for a T1 line as it would for DSL. In other words, for the cost of a single T1 1.54 Mbps connection, three 1.1 Mbps DSL connections can be supported.

  • Primary connection for the Internet and data services (note: many organizations do not consider DSL sufficiently robust for their primary link, but if cost is the primary consideration, DSL will provide the necessary functionality).

  • Decreased installation charges. Typically, installation costs for a T1 line are three to four times as much as installation and setup of DSL services. DSL uses traditional telephone lines as opposed to T1, which requires installation of special (conditioned) lines.

  • Multiple pricing categories. Depending on needs, more or less bandwidth (line speeds) can be purchased (if available in the area).

  • Combined data and voice services over a single connection (for small offices). Although not yet widely deployed, Voice-over-DSL (VoDSL), shown in Exhibit 1, is starting to be implemented in selected locations in the United States, such as Santa Clara, California, and Boston, Massachusetts. By combining multiple voice channels and data on one copper wire, local telecom companies can offer a competitive package to small businesses that need only Internet access and a few voice lines. Jim Greenberg, chief architect at Rhythms NetConnections Inc., estimates small businesses could save about 30 to 40 percent on additional voice lines and get it all from one company.

    Exhibit 1: Voice-over-DSL (VoDSL)

  • An "always-on" technology, unlike ISDN, which requires a sign-on.

  • More secure than cable modem, because the bandwidth is not shared with other users (due to DSL's copper wire to the user legacy ar architecture — dedicated to a single user).

Disadvantages include:

  • DSL installation, while generally faster and cheaper than T1 or T3 installation, may experience technical problems. DSL runs over lines designed prior to World War I. It was originally intended to carry only miniscule traffic. For such a scrawny system to shoulder mountains of Internet data is akin to one writer's quip about a dog walking on its hind legs — "It is not done well, but you are surprised to find it done at all." Exhibit 2 shows an analysis of the percent of DSL installations completed versus time required for the install.

    Exhibit 2: DSL Installation History: Percentage of Installs over Time of Order

  • Multiple parties are involved. Typically, when a local telephone company, ISP, and possibly a DSL provisioning company are involved at some point in providing the service, the potential for billing errors and increased repair time is greater.

  • DSL bandwidth varies considerably. The distance from the POP largely determines the bandwidth that is available to a DSL customer. The distance limitation is usually considered 18,000 feet but "loop extenders" from companies like Symmetricom can extend the distance considerably. Exhibit 3 shows the relationship between bandwidth and distance from the central office.

    Exhibit 3: Distance versus Bandwidth for DSL