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SIPquest: Latent Genius? By Gerry Blackwell
Voice over Wi-Fi works, but it continues to present some interesting technological challenges. For example, what happens when a user is talking on a Wi-Fi phone and starts to move out of the coverage area provided by one access point into the coverage of another? If the user were transmitting only data over the network—a doctor with a PDA moving around in a hospital, for example—it wouldn't be a problem. With an IP telephone call, it's not so simple. Without any technological intervention, there is a break in the flow of voice packets that, while typically less than a second, is enough to seriously degrade a voice connection and very likely drop the call. This latency goes unnoticed in data applications, but not IP voice connections. It is a problem faced by cellular networks as well, of course, but one that had to be solved before cellular was even possible. Original Wi-Fi LANs were never intended to carry voice, however, and most existing WLANs were installed with the intention of only ever using them for data. There are solutions. Most involve using specially designed access points—from companies such as Meru Networks. They typically require replacing existing WLAN infrastructure. SIPquest, a Canadian developer, says it has a better solution. The company's recently announced SIPquest Fast WiFi Handoff software, which it describes as "non-proprietary," runs on client devices and works in virtually any Wi-Fi network and VoIP environment that is SIP (Session Initiation Protocol) enabled. "We can even support roaming in multi-vendor access point environments, with no changes to the infrastructure," says SIPquest CEO Alain Mouttham. "The software is all on the client." SIPquest is mainly targeting enterprise Wi-Fi equipment vendors. They can embed the Fast Wi-Fi Handoff software in their client devices. The initial end market for such devices will be enterprise wired/wireless VoIP installations featuring IP PBXs and SIP servers. The company already has versions of the software for—or is in the process of porting it to work on—Pocket PC, Palm OS, smart phone and Symbian platforms. The Wi-Fi Handoff software is not SIPQuest's only product. The company has been in business for about two years and selling for over a year—including to 3Com. It offers SIP server and SIP-to-H.323 gateway software, application software for SIP servers to do audio, video and data conferencing and voice mail and auto attendant, plus client software for collaboration and mobile collaboration. The hand-off latency in a Wi-Fi network is fundamental to the technology. Three things happen as signal strength from the original AP begins to fall off. The client starts to scan for other access points in range. The signal strength from the original AP meanwhile continues to weaken, reducing call quality. Finally, when the client device finds the next nearest access point, it has to authenticate with it. All of which takes time—typically between 400 and 600 milliseconds. "If you didn't have any special roaming capability, there would be noticeable degradation in call quality during this process and probably some echo on the line," Mouttham says. "If the latency reaches 400 to 600 milliseconds, there's also a high liklihood of the call dropping." To ensure trouble-free IP voice hand-offs from AP to AP, it's necessary to reduce latency to below 150 milliseconds. The SIPquest technology, which was mainly developed at Columbia University's Internet Real-Time Lab and provided to the company under an exclusive licensing arrangement, gets the latency below 10 milliseconds. It uses algorithms that help the client device begin the process of scanning for a new AP sooner and authenticate with it faster. While the SIPquest solution does not require reprogramming or replacing access points, it does require the presence of a SIP server and other SIP infrastructure in the network. SIP is a signalling protocol for Internet conferencing and telephony. It initiates call setup, routes calls, authenticates clients and relays messages about calling features among endpoints in an IP domain. According to Mouttham, SIP is becoming "pervasive" in wired and wireless VoIP implementations. "SIP allows functionality such as presence management and instant messaging that H.323, [the International Telecommunication Union standard for Internet voice and video conferencing,] doesn't," he points out. "Microsoft was one of the first to adopt SIP. Now everybody is in the process of adopting it—or it's on their road map. That's why SIP is so important." With the SIPquest solution, thanks to Internetworking features in the protocol, a user could even move between an AP in a corporate WLAN and one in an adjacent public hotspot or hotzone without interruption or loss of call quality. Furthermore, the phone would continue to function as if attached to the corporate IP PBX—with access to all the features and services available on the corporate network. The public hotzone must, of course, be SIP-enabled. It's not clear how many are at this point. Mouttham may be over-stating the case when he says that "SIP is becoming pervasive in the hotspot and hotzone community." Most if not all hotzones that support voice over Wi-Fi may be SIP-enabled, but as Mouttham concedes, "Many hotzones don't yet support voice." That may or may not change in the short term. Meanwhile, the next step—or "the last phase," as Mouttham puts it—is developing SIP-based technology that will allow dual-mode Wi-Fi/cell phones to transparently roam between a Wi-Fi network and a cellular network. Columbia and SIPquest are already working on it. The technology will allow hand-offs not just to and from current 2.5/3G cellular but also older 2G GSM and CDMA networks. "Work on development [of the Wi-Fi/cellular hand-off technology] is ongoing—it's being tested in the Columbia labs now," Mouttham says. "And we've begun talking to lead customers. Our plans today are to release something in mid-2005." While the primary market for the Fast Wi-Fi Handoff software is enterprise Wi-Fi equipment vendors, SIPquest is also getting interest from Internet telephony service providers (ITSPs). They could integrate the technology into their soft phone offerings or into Wi-Fi-enabled IP voice gateways. "But those are opportunistic sales," Mouttham says of the service provider customers. The main focus remains equipment vendors. SIPquest appears to be a serious player. It received a total $3.5 million in first-round financing from Covington Capital and Skypoint Capital, two Canadian venture capital firms, and from Venturelab of Santa Monica, Calif. It's now two months into a second round of financing. Revenues for calendar 2004 will top $1 million—not bad for a young company selling bleeding-edge technology.
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