Continued pressure on voice tariffs, coupled with a steady influx of new subscribers, is forcing operators to continuously expand network coverage and improve cost efficiency. The latter is particularly pertinent in developing markets that have poor initial coverage and where new users may yield relatively low average revenues.

Transporting voice calls around the network represents one of the largest cost elements for most operators, especially those in emerging markets. One of the best ways to reduce operational expenditure is to capitalize on the predominance of local calls in the network, typically more than 70 percent. The implementation of softswitching separates signaling from payload and enables switching to be distributed to the edges of the network for maximum transmission efficiency.

In Ericsson's Mobile Softswitch Solution (MSS), all signaling is handled in centrally located Mobile Switching Centers (MSCs), while the payload – the actual voice traffic – is taken care of by Media Gateways (MGws). Before, the Classic MSC took care of both payload and signaling.

Among the unique benefits, says marketing manager Andy Williamson at Ericsson, is that it simplifies core network design and allows operators to start migrating traffic to a layered architecture, where circuit-switched services, such as voice, are efficiently carried over a packet backbone based on IP or ATM.

Williamson says: "Softswitching provides enormous benefits but it takes experience to maximize efficiency savings and manage the risk of this major technology shift. Ericsson deployed softswitch solutions commercially 18 months before anyone else did, and is the only vendor with high-capacity mobile softswitch networks in commercial service. After more than 50 installations – of which more than 20 are mobile – Ericsson knows the best ways to design and build softswitched networks."

Uniquely smooth evolution path
Ericsson MSS supports both GSM and WCDMA, enabling a safe and standardized implementation of carrier-grade mobile voice for 2G and 3G networks. Evolution and efficiency, says Williamson, are the cornerstones behind the constantly ongoing development work. "Ericsson has successfully designed a uniquely smooth evolution path from 2G to 3G and from circuit- to packet-based technology with full investment protection."

Efficiency, on the other hand, is an immediate benefit from implementing Ericsson MSS. "You are able to put in place a much more efficient core network design where the sophisticated equipment handling all of the call control and service intelligence is located at just a few sites, close to existing operations centers," Williamson says.

Efficiency can be further improved by placing a number of individual MSCs in a pool. Williamson says: "This significantly boosts MSC capacity, improves in-service performance and reduces operation and maintenance requirements."

The signaling traffic processed by the MSC-Servers contains a lot of important information but requires very little transmission bandwidth. The actual voice traffic, which is handled by the MGws, drives transmission capacity requirements. "The less you have to transmit, the cheaper it gets. Connectivity savings are instant with our solution," Williamson says.

The solution also brings savings from reduced power consumption and from the closing down of sites. To operators that need to expand network coverage, Ericsson MSS is cheaper than conventional setups, because the distribution of MGws is sufficient to reach previously non-serviced rural areas and the MSCs may be localized to urban areas.

One of the recent adopters of Ericsson MSS is leading sub-Saharan operator Celtel. Holding mobile licenses covering 30 percent of Africa's population, many of Celtel´s customers are found in remote, rural areas and offer limited spending power. Steve Torode, of Celtel, says: "The contract for Ericsson MSS will enable Celtel Tanzania to expand, enhance and further upgrade our network in the most cost-efficient manner."