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Feature Article
October 2004

Sidebar: SIP over WLAN: Enterprise Goes Wireless

BY Sunil Mahajan

Public wireless networks are experiencing tremendous growth. Increasingly operators worldwide have adopted the strategy to focus more on mobile users with innovative services such as SMS, MMS, PTT, gaming, converged voice and data terminal (GPRS), roaming across operators, single number while roaming etc. However, despite high growth in the end user segment, wireless communication has not been rapidly adopted in the enterprise environment. Most of the enterprises (barring few in European countries) are still using fixed line phones and innovation (the set of services offered) remains relatively unchanged. Enterprises are still at first generation (1G) network level, though there is a big overlap between the people who use public mobile network and people who use enterprise networks. So why is the set of services and user experiences so different in these two networks?

Network architecture has evolved in recent times to make the enterprise experience as enriching as it is in public wireless networks. While defining the next generation of enterprise networks, we need to concentrate on following issues:

  • Affordability.
  • Innovation.

With advancements in WiFi technology, in terms of QoS, security, and reduction in equipment cost, enterprises have started evaluating WLAN for supporting voice services. Enterprise-wide WLAN deployments will help people to be mobile within enterprise environments and hence increase the overall employee productivity. In addition, this will help in converging the data and voice traffic on the same infrastructure. Most of the solutions available in the market use SIP as the signaling protocol to support enterprise voice services, which means SIP servers are now being positioned as IP-PBXs. This convergence can help build new innovative services for the enterprise. In addition to providing mobility within an enterprise, this setup can also provide roaming across enterprises or across enterprise and public mobile networks.

To provide seamless roaming, enterprises need dual-mode handsets, which can support both WLAN and GSM (or any other mobile standards). SIP will be the protocol of choice for dual mode handsets, as this ensures:

  • Standards-based interface between handset and servers;
  • Environment to create more innovative services for enterprise as well as services which can exploit converged mobile and enterprise networks;
  • Compliance to next generation mobile networks (e.g. 3GPP, 3GPP2);
  • SIP-based registration (location update), authentication, and call transfer across enterprise servers, enabling true roaming.

So a WiFi-based enterprise network combined with SIP-based infrastructure components can provide a true next-generation enterprise environment, which can provide bandwidth higher than that of public mobile networks. This opens the scope for more innovation and a higher degree of convergence within enterprises. However, there are still challenges related to QoS, security, and IP mobility, which network managers need to solve before widespread adoption of a converged enterprise network architecture.

So, what will drive adoption of a successful converged architecture in the enterprise?

  • Security over WiFi network. WiFi network deployment within enterprise should be resistant to security attacks.
  • WiFi network providing service for real time traffic such as voice.
  • Solution deployment shall support seamless roaming between enterprise network and public network, providing a common authentication/security mechanism.
  • Availability of dual-mode handsets.

Once some of these initial hiccups are resolved, the market will start seeing increased enterprise deployments based on WiFi and SIP, with the goal of manifestly transforming the enterprise communications experience.

Sunil Mahajan is chief systems engineer at Hughes Software Systems. For more information, please visit the company online at

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