This article first appeared in the December 1999 issue of Monitoring Times.


What does it mean these days to stay in touch?

Personal Communications Services (PCS) have evolved rapidly from the early days of cellular telephones. Bulky car-mounted phones have given way to sleek, hand-held terminals offering voice, electronic mail, and even access to the worldwide web.

Wireless services have become very popular. At the end of last year there were more than 300 million subscribers around the world, compared to just 11 million in 1990. Since 1996 the number of new mobile subscribers has exceeded the number of new fixed wireline customers, and nearly a third of all telephone connections now involve at least one mobile phone.

PCS continues to evolve and diverge into different market niches. One such niche involves moving the cellular towers into space. Such systems, formally called global personal communications by satellite (GMPCS), are part of the next generation of "anytime, anywhere" connectivity.

Satellite handsets typically support several air interfaces and frequencies, allowing a subscriber to use one phone throughout the world over multiple cellular systems as well as on satellite-based networks.


The next Big LEO to enter the market is California-based Globalstar. Their $3.3 billion system uses 48 satellites in low earth orbit to communicate with both fixed and mobile users, linking them to terrestrial Global System for Mobiles (GSM) and Code Division Multiple Access (CDMA) cellular networks.

Globalstar announced a "phased roll-out" of their service on October 11, 1999. Nine operational gateways provide service to "friendly users" in a dozen countries around the world. Full commercial voice service is expected in early 2000, with 9600 bit per second data and facsimile later in the year. Handsets built by Qualcomm, Ericsson, and Telital will retail between $1000 and $1500, while international calls will run anywhere from $1 to $2 per minute.

Several technical issues distinguish Globalstar, although none of them may save the company from suffering the same fate as the earlier GMPCS entrant, Iridium.

Coverage Global 70 degrees North to 70 degrees South
Transponder Proprietary Bent Pipe
Access Method Time Division Code Division

Perhaps the most significant technical difference is that Globalstar satellites operate as bent pipes, simply retransmitting a band of received frequencies back to the ground. Iridium satellites process signals on-board, making them useless for purposes the designers had not foreseen. Unlike Iridium, if Globalstar cannot make a go of their voice service they may be able to sell unused capacity to other companies wishing to rent L and S band transponders.

To keep construction costs down, Globalstar satellites are significantly smaller and less powerful than Iridium. Because of this, calls placed from portable phones may require two or even three satellites working together to complete a call. Using a process called diversity combining, handsets and earth stations assemble several relatively weak signals from different satellites into one strong signal.

More fundamentally, however, is the simple business question: is there a market for mobile satellite voice service?

Globalstar predicts they'll have 250,000 customers by mid-2000, and their business plan calls for three million customers by 2002.

Rivals Iridium LLC and ICO Global Communications, Ltd. are in bankruptcy, each having failed to generate sufficient confidence from the investment community. Iridium is in operation despite having relatively few customers, while ICO has yet to launch their first satellite. Iridium in particular suffers from poor management and an expensive, ill-conceived marketing plan, but all three ventures are essentially competing with terrestrial cellular service.

Each of these Big LEO systems was designed a decade ago, when cellular coverage was limited and prices were high. In the time it took to design, build, and launch these multibillion dollar systems, the terrestrial market lowered airtime costs, created inexpensive handsets, and built out coverage in most places where people travel. Whether there is a large enough market for mobile voice service via satellite remains to be seen.


In contrast to the complicated and hugely expensive voice systems, Virginia-based Orbcomm has taken a different approach. Backed by Orbital Sciences Corporation and two other partners, Orbcomm provides a simple, low cost electronic messaging service via twenty-eight satellites in low earth orbit.

In April 1995, Orbcomm launched a pair of "microsats" to test the feasibility of an orbiting "store and forward" message system. These satellites were designed to receive a short electronic mail message during one part of their orbit and transmit it back to Earth in a later part of the orbit. Additional launches in 1997 and 1998 brought the constellation up to its present total of 28. These satellites cannot process voice calls or high bandwidth messages, but the entire system cost less than $500 million. As a result, Orbcomm can offer low prices to customers that need occasional, low bandwidth communications for such applications as vehicle tracking, environmental monitoring, and equipment telemetry.

Several manufacturers, including Pioneer and Scientific Atlanta, build subscriber terminals, although Orbcomm is presently having difficulty generating revenue. As of June 1999, more than 116,000 subscriber units had been ordered, but only 11,000 were actually installed. Orbcomm hopes to have 50,000 units installed by January.

Orbcomm satellites weigh 95 pounds and fly at an altitude of about 500 miles, taking just over an hour and a half to orbit the Earth. For communicating with customers, each satellite contains one transmitter, typically operating at 20 watts, and seven receivers, each tuned to a frequency between 148 MHz and 150 MHz. Satellites transmit to subscribers via VHF radio links between 137 MHz and 138 MHz. Each Orbcomm spacecraft also has the capability of transmitting an UHF beacon at 400.1 MHz through a separate one-watt transmitter.

Monitoring Orbcomm satellites

Orbcomm satellites can easily be heard on most scanners and receivers capable of tuning in the 137 MHz band. The chart below indicates the frequency on which the corresponding satellites transmit. For those listeners interested in tracking these satellites via radio, John David Corby runs an excellent website at that contains updated information for many satellites, including the Orbcomm constellation.

137.2500 C1, C2, C4, C5, C7
137.4400 A3, A7
137.4600 F2
137.6625 A8, C3, C6, C8
137.6875 G1, G2
137.7175 A1, A2, A4, A5, A6
137.7375 B2, B3, B6, B7, B8
137.8000 B1, B4, B5

Because the Orbcomm satellites are in low earth orbit, they may only appear above the horizon for 10 or 15 minutes at a time. A satellite tracking program from the Radio Amateur Satellite website at along with current satellite position information (called "elements," available from as well as other sites) will allow you to predict which satellites will be overhead as you're listening.

Also keep in mind that because of Doppler effects of the moving satellite, the received frequency may not be exactly as depicted in the frequency table. The maximum Doppler for Orbcomm satellites is about 3 kHz.

Future of PCS

Personal Communications Systems will continue to evolve. The first generation of cellular telephones - the analog networks - are rapidly being replaced by a second generation of digital systems. The chart below indicates the percentage of wireless subscribers using each of these new technologies.

GSM 44 4
CDMA 7 9
PDC 11 -
PHS 2 -
AMPS 23 60

The goal of third generation (3G) cellular technology is to bring together terrestrial wireless, cordless, and satellite networks into a global standard. This initiative is called International Mobile Telecommunications-2000 (IMT-2000) and promises seamless roaming and higher transmission rates. Target dates for 3G include Japan in 2001, Europe in 2002, and other areas afterward. Build out of these advanced networks will probably occur in high population density areas first, gradually replacing earlier systems as customer demand warrants.

These new systems will also be linked to location reporting technologies, such as the Global Positioning System (GPS).

Other market niches for PCS will be found. One such area is prepaid wireless service, which is growing rapidly. Prepaid is a win-win situation: operators receive their money up front and incur little risk; subscribers control their costs, obtain service where they might otherwise be denied due to poor credit, and keep some anonymity.

Such anonymity, and the mobility that wireless service affords, does not sit well with law enforcement agencies, who wish to maintain their easy wiretapping capability. Expect legislation such as the Communications Assistance for Law Enforcement Act (CALEA) and various encryption regulations to alter the services operators offer, and not to the benefit of the consumer.

It is also likely that prices for wireless service will continue to fall. Prices stayed high in the 1980s due to limited supply and a lack of competition, and held high in the 1990s due to a rapidly expanding market - lower prices were not needed to attract new customers. With more competition and fewer new customers, prices should drop much more rapidly in the coming years. Profit margins of 10 to 20 percent, enjoyed by such operators as AirTouch, Bell Atlantic Mobile, BellSouth, and SBC, should become a thing of the past.

And that's it for PCS Front Line. This is the last regular column to appear in Monitoring Times, as I make way for someone else. I've enjoyed writing for MT these past three years almost as much as receiving electronic mail and letters from readers. I will continue to be available by e-mail at, and my website at will continue to have PCS, cellular, satellite, and other information related to communications technology. So for now, happy monitoring!

Comments to Dan Veeneman

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