However, there are still opportunities to maximize mobile-voice business. Ericsson has pinpointed three areas operators should consider: voice service portfolio, service-delivery efficiency and pricing strategy.

Americans spend far more time chatting on the phone than their global counterparts, and mobile voice telephony in the US is booming. The use of "bucket pricing," based on an "all-you-can-eat" principle, is perceived as a near flat rate by customers and has resulted in increased voice usage. Subscribers pay a set fee and have a set number of minutes to use per month which, in many cases, exceeds actual usage.

Voice still accounts for 80-85 percent of mobile operators' total revenues. Analysts predict mobile voice will remain the dominant revenue source over the next five years. However, in comparison with much higher growth rates previously, absolute mobile-voice revenue figures are only expected to increase moderately, by 3-4 percent year on year. Meanwhile, mobile traffic figures are expected to grow significantly.

This pattern of stagnation or moderate revenue growth can be attributed to aggressive competition in the market place, according to Sven Bolthausen, head of Ericsson's advice service for Northern Europe. "We will see drastic price reductions on voice calls that will not be compensated by increased voice usage," he says. "Therefore, many operators are shifting their focus on attacking the huge fixed-net traffic market." By 2010, mobile voice will account for about 60-70 percent of operators' total revenues in Western Europe.

With saturation point drawing near, operators need to encourage existing subscribers to talk more, rather than getting new subscribers to sign up. "New subscribers today are the over-65s and the under-10s who do not use their phones extensively, as well as second or third SIM cards from existing mobile users." Bolthausen says. "The lucrative user groups have already been acquired, so the focus for operators is definitely on increasing usage and retaining existing customers."

In order to increase average revenue per user (ARPU) and win valuable customers from competitors, operators need to implement innovative price models, and should look to the US as a successful example. As Bolthausen says: "Bucket pricing is a very simple, yet effective, pricing structure and we can expect more of this kind of pricing in Europe."

Bolthausen adds, however, that an operator cannot survive simply by cutting costs. "There is a dangerous threat for operators that pull only the price trigger," he says. "They also need to consider network performance, voice quality and voice-completion effectiveness, new services and customer care – these key issues should not be neglected when trying to stimulate mobile voice growth."

Indeed, there is untapped potential elsewhere for mobile growth. Operators with optimal voice-service portfolios can exploit the most attractive markets. In-depth knowledge of consumer behavior enables operators to respond to customer need, satisfy subscribers in terms of quality and ease of use, and stay ahead of competitors.

Operators also need to ensure their service-delivery efficiency is first class in order to maximize mobile-voice business. Strong network performance with consistent quality for users and an increase in voice-call success ratios are vital for operators to avoid loss of mobile-voice revenues by uncompleted calls.

"It's not about implementing a single technical solution," Bolthausen says. "It's about employing a complete call completion strategy covering network availability, user behavior and the deployment of segment-specific call completion solutions for busy or unavailable subscribers."

Bolthausen concludes that there is potential for all operators, even in the most saturated markets, to benefit. "Our strategy projects have proven that uncompleted calls represent a huge untapped market potential of more than 30 percent of all call attempts, which can easily be turned into revenue," he says.