According to Ovum, the key events moving against Iridium are:

• the introduction of the WorldPhone from the end of 1999. This will enable mobile subscribers to roam between GSM (global systems for mobile communications), AMPS and D-AMPS networks. These technologies cover over 80% of the mobile subscriber population. However, Ovum anticipates that the phone will take a couple of years to become established.
• the continued roll out of cellular networks. For example, coverage of GSM networks in the US is currently only limited to some urban areas. However, the continued build out of these networks (licensees that are committed to GSM cover over 90% of the US population) over the next few years will reduce Iridium's potential market.
• Introduction of third generation mobile systems from 2002 onwards.

"The Iridium project represents one of the largest ever global service launches," says Alex Nourouzi, senior analyst at Ovum and a world authority on MSS. "It is significant because it is the first of potentially 10 MSS systems that are planning to launch over the next three or four years. If all systems launch, collectively around $20 billion will have been spent pursuing the market for mainly voice based mobile satellite services.

The Iridium service will be sold mainly by approved service providers, many of these are existing cellular operators. Nourouzi continues, "Although Iridium will be complementary to existing cellular services, there will be a number of constraints to the service which mean that users will not get a seamless transition between cellular and Iridium. For the Iridium system to be a success, service providers must make potential subscribers aware of the differences between cellular and Iridium, as people's expectations will be set by the performance of their cellular services."

Ovum believes Iridium must address four critical factors to ensure its success:

• terminal appearance - the Iridium phone compares unfavourably with a high-end cellular phone. The Iridium phone will be larger, heavier and will have a shorter battery life.
• service offerings - at present, the most widely used digital cellular service is GSM. The most important difference between GSM services and MSS will be data services. For international business travellers in particular, the seamless availability of data services is critical. GSM data rates will increase to 64 kbit/s from 2000 and will be packet based. Iridium's 2.4 kbit/s service will look increasingly inadequate.
• in-building usage - cellular operators are increasingly looking at ways to encourage the substitution of call traffic from fixed networks to mobile networks. This trend will continue with the introduction of cellular home base stations. While cellular subscribers are using, and will continue to use, their phones in buildings, Iridium subscribers will need line of sight of an Iridium satellite to be able to communicate with the system. This not only greatly limits usage in buildings, but also makes usage in built up areas problematic. The minimum angle of elevation that an Iridium subscriber could experience is about eight degrees.
• cost - the monthly fee and cost of an Iridium terminal will vary between individual service providers. If terminals are not subsidised, they will cost about $3,000. Usage costs will also be dependent on service providers, although expectations are that $3 per minute will be a likely average initial tariff. Although the Iridium system will be a complementary service to existing cellular, its tariffs will have to bear some relation to cellular tariffs, particularly roaming tariffs. Ovum's price comparisons show that in only 14% of cases would using the Iridium system be cheaper. A similar comparison in 1996 revealed that Iridium would have been cheaper in 52% of cases.

"The Iridium system was mainly developed to enable international travellers to use a mobile phone anywhere in the world," concludes Nourouzi. "In the late 1980's, the idea was a good one. At the time, the mobile industry was plagued by more than ten incompatible proprietary technologies making roaming difficult. But the originators of handheld MSS, Motorola, could not have foreseen the ensuing changes that have resulted in the development of GSM. We see GSM as the primary threat to the success of MSS."