Softswitches are at the centre of the next-generation networks (NGN). Together with media gateways they would be key to the replacement of legacy central office (CO) TDM switches in the public telephone networks. Both wireline and wireless service providers' growing inclination towards IP and the growth in business-and consumer-VoIP services have been driving softswitch deployments in almost all major telecom markets. Even though softswitches are still far from completely replacing the legacy switches, they are certainly mainstream now.

Technology Options
Class 4 softswitches: Class 4 softswitches are meant for Internet offload and tandem switching applications. Internet offload has remained the most popular softswitch application till date. Operating at the network level, and providing connectivity between the PSTN and an IP network, these softswitches are often embedded in the hardware media gateways. Used for moving calls between two networks, these softswitches focus on the rapid offload of data (modem) calls from the PSTN to the Internet and cost-effectively free up TDM circuits for voice traffic. They are also used for packet-based tandem routing functions so that calls can traverse the PSTN effectively. The goal of this softswitch to provide call control, call routing, and interconnection at the core of the network and interface with the SS7 network.

Class 5 softswitches: These softswitches are meant for deployment in the access network. The three categories offering class 5 replacement services are residential softswitches, end office/IP-centrex softswitches, and the spplications-enabled softswitches. Residential softswitched offer basic features such as call forwarding and call waiting. They are meant for replacing the existing residential switches and enable service providers to offer call forwarding, call waiting, caller ID, and some other consumer services. The end office/IP-centrex softswitch offers functionalities such as call conferencing, call hold, call park/pickup, and hunt group routing, besides some Web-based provisioning. They are built to the needs of small to large businesses, scaling to thousands of lines and providing value-added, business features.

Softswitch Benefits
More work, less space: A softswitch gets rid of a lot of hardware. This saves operators a lot of real estate cost. According a US service provider, what today takes about 720 cubic feet, shrinks down to eight cubic feet. The saved space can now be utilized for some other functions.

Faster service creation: Compared to the TDM world, where everything is proprietary, softswitches are all about open standards. The proprietary nature of TDM switch ensured that service creation was impossible without vendor support. This is one of the reasons why new service creation is always a long drawn process in the TDM world. On the other hand, service creation in a softswitch environment is purported to be easy and fast and endless too. Service providers become independent of vendors and thereby gain more control over service creation. The softswitch service creation environment is good for service providers trying hard to create segmentation, because services targeting as little a 1,000 niche customers can be created.

Network efficiency, low opex: When compared to a traditional switch, they offer significantly lower capital and operational costs. They provide a cost reduction strategy to help service providers transition their circuit-switched networks to a packet-based infrastructure that allows for cheaper transport. Another great benefit offered by softswitches is that it does not matter where the customer is coming from-whether wireless, DSL, cable, leased line, or just plain copper. Software makes the network access neutral.

Deployment Trends
Market reports and vendor revenues suggest that the softswitch market is moving from trial mode to commercial deployments. A Dell'Oro Group report says that sales of next-generation VoIP equipment-including softswitches, media gateways, and hybrid media gateway softswitches-grew three percent worldwide in the Q2 2004. Purchases of softswitch trunk licenses, which are indicative of deployments in the service provider network core, grew four percent in Q2 2004 over Q1 2004, while subscriber licenses declined 12 percent during Q2. Year-on-year (Y-o-Y), sales of softswitch trunk licenses grew 36 percent.

According to Infonetics Research's quarterly market share and forecast service, the worldwide next-generation voice product revenue totaled $452 million in Q3 2004, up 13 percent from Q2 2004-and up 69 percent Y-o-Y. Annual revenue is projected to grow from $1.3 billion in 2003 to $4.8 billion in 2007, representing a strong CAGR of 39 percent. According to Infonetics, voice application servers, session border controllers, and softswitches, especially class 5 licenses and revenue, grew the most. This indicates that service providers are really beginning to change gears, from investing in infrastructure to investing in next-generation equipment, which will allow to offer new services.

Worldwide softswitch and media gateway revenues will reach $9.3 billion in 2009, a robust 47 percent CAGR from 2004 to 2009. According to IDC, softswitches and media gateways will combine to surpass total revenues for legacy switches for the first time in 2009. Wireless softswitch revenues will account for 27 percent of total worldwide revenues by 2009.

Even though most deployments are currently focused on core networks (replacing class 4 legacy switches), the access networks (class 5 switches) too are seeing good action. Infonetics Research found good growth in class 5 softswitch revenues that went up 34 percent Q-o-Q, to $76 million.

In the US there have been major deployments of both class 4 and 5 softswitches. While class 4 have been deployed by service providers like Sprint, Verizon, and Quest; class 5 switches are being used by Bridgecom, US Lec, and TDS Telecom among others.

In China, Shanghai Netcom has deployed softswitches; as has Brazilian operator VIVO. Australian incumbent Telstra is also all set to use softswitches and media gateways in its VoIP-over-broadband trials.

Softswitch-based Next Generation Network Architecture

In India, while only Tata Teleservices has deployed a softswitch (Motorola softswitch for CDMA (MSS-C) on its CDMA2000 1x network at Nagpur in Maharashtra), other operators have doing trials with different vendors. UTStarcom is doing a CDMA softswitch pilot with a private operator. So is Tekelec, which is trying out a combination of class 4 and class 5 MSC with some operators in India.

The incumbent BSNL too is now interested in the softswitch technology. One of its latest tenders is for procurement of softswitches (along with media gateways and other related elements) to be deployed at New Delhi and Chennai. What is interesting is that BSNL is keen to deploy softswitches that should have capability to support class 5 features as and when IP is introduced in the access network of BSNL.