Poised for Takeoff

Fundamentals First

Alcatel, NEC and Nortel Networks all offer proprietary, and often expensive, wireless systems that integrate with their PBX systems. Some organizations might opt to use cell phones for mobile communications inside the organization, though this, too, is costly and in-building coverage can be spotty. Another popular solution is the use of licensed walkie-talkie-type private radio systems for internal communication.

VoWLAN systems aren't really new, either. SpectraLink, the current market leader, still earns a large proportion of its revenue from 900-MHz wireless LAN voice systems first introduced more than 10 years ago. However, system costs remained high until recently, when the company introduced its first phone priced less than $400. Deployment costs still can be high because organizations need broad radio coverage to take full advantage of VoWLAN. The data-focused hotspot conference-room and cafeteria deployments found in many organizations just don't cut it. If you are serious about VoWLAN, you'll need to design a WLAN that provides coverage everywhere, including elevators and stairwells.

Today's VoWLAN market is quite small, but growing quickly. According to a March 2003 report from communications research and analysis firm In-Stat/MDR, only 30,000 802.11 VoWLAN handsets were shipped in 2002, a number the firm predicts will triple in 2003. In-Stat/MDR doesn't think the market will reach 1 million units until 2007 (see "VoWLAN U.S. Handset and End-User Revenue Forecast," left).

However, we see a number of interesting factors conspiring to jump-start the market sooner. First, there's a new generation of WLAN infrastructure products designed from the start with telephony in mind. Second, Cisco Systems has entered the market with its slick new 7920 wireless VoIP phone that integrates with the company's mature VoIP product line. Cisco brings legitimacy to any emerging network market. Finally, we see a number of technical enhancements coming in 2004 and 2005 that will help overcome some of the limitations of current systems.By the third quarter of 2004, we expect the IEEE to release QoS enhancements to 802.11 (see "Quality of Service and 802.11e,"). Although 802.11e QoS won't be perfect, it will at least provide a standards-based approach that prioritizes voice traffic. Another development will be the release of more power-efficient WLAN chips, which will facilitate embedding WLAN functionality in smart phones, PDAs and other power-limited devices, all of which are becoming powerful enough to support VoWLAN services. This will reduce deployment costs significantly and enable development of new integrated voice/data applications.

We also predict the growing acceptance of the SIP (Session Initiation Protocol) VoIP standard, a move we think will further increase competition and reduce phone prices. Finally, there are continued improvements in voice-codec and voice-response technologies, plus the introduction of new cell phones during the coming year that will integrate 802.11 VoWLAN and conventional cellular protocols, including CDMA and GSM/GPRS.

Enterprise Features

Although it's possible to use any standards-based VoIP device over a wireless network, our experience using SIP phones designed for the Pocket PC platform was disappointing at best (see "SIP Soft Phones,"). Because none of the major VoWLANs support SIP, your best option is to find a hardware platform that was designed from the ground up with wireless in mind. However, these systems vary, with some providing a relatively simple voice overlay and others a more comprehensive voice solution. Those differences also make it difficult to compare prices, except for the phones themselves. Just be aware that a low-cost phone doesn't necessarily mean a low-cost system.

Some vendors, like Cisco, leverage an established VoIP infrastructure, adding a voice handset to a broad product line. Other products, like Vocera's, include their own call managers and PBX/PSTN gateways. In most cases, you can place calls directly to other wireless devices through the call manager. Otherwise, you'll need to route those calls through the PBX/PSTN gateway. Many products support multiparty calling and intercom capabilities, which can be useful for internal communications.

As with all wireless devices, VoWLAN has security considerations, with all vendors pledging support for future security standards. Meantime, you'll need to be satisfied with WEP (Wired Equivalent Privacy) and MAC (Media Access Control) ACLs (access-control lists) or use a vendor-specific security architecture like Cisco's LEAP or Symbol's implementation of Kerberos. Although security concerns should not be ignored, risk can be somewhat mitigated by using wireless VLANs that are isolated from secure systems. Thus, you could implement a wireless VLAN called "phone" and restrict traffic only to handheld devices, the call manager and, if desired, a PSTN/PBX gateway.

Our Tests

For this review, we immersed ourselves in the world of VoWLAN for a two-month period. We talked to vendors, analysts and IT professionals, and we invited a long list of vendors to submit products for testing. In light of the market's immaturity, we were flexible in our product solicitation criteria. In the end, we received a variety of products from large and small vendors alike, including all the major VoWLAN system vendors--Cisco, SpectraLink, Symbol Technologies, TeleSym and Vocera Communications. We also took a look at some smaller soft-phone vendors--SoftJoy Labs, VLI and Xten--whose products are advertised as operating over WLANs. Because the various VoWLAN systems are so different, we didn't develop our usual report card, but we do provide a critical assessment of the strengths and weaknesses of each product offering alongside our analysis.

Standards are also a major factor, with all the vendors using a mixture of open and proprietary protocols. Although all products run over 802.11b, none of the products we looked at included support for 802.11a or 802.11g. Many promise they will support strategic VoIP standards like SIP, but today, there's very limited interoperability between products from different vendors. Your choice of a product will depend in large part on your specific requirements and your existing infrastructure. For example, if you have already implemented a Cisco VoIP infrastructure, you'll choose between the new Cisco 7920 phone or phones from SpectraLink that support Cisco's call manager protocol (SCCP). All of the vendors provide connection to outside voice systems, even if it is only the lowest-common-denominator analog voice connection.When Cisco entered the WLAN market a few years ago after acquiring Aironet, demand for those products tripled in the first month. It's a safer enterprise buy when the box says Cisco, and we think that's also the case in the VoWLAN market. Unlike the other vendors, Cisco's offering is best seen as a complement to its enterprise VoIP architecture rather than a standalone offering.

Cisco shipped us a preinstalled Cisco Call Manager (CCM) server, two 350 APs (access points), a desktop 7960 VoIP phone, and several of the handsome new 7920 phones. CCM provides full IP/PBX capabilities, including a range of advanced features.Cisco has made no secret of its desire to dominate the enterprise telephony market, with VoIP Call Manager replacing the legacy PBX. Enterprise VoIP doesn't get the level of hype it once did, which may be an indication that it is maturing. Yes, there continue to be obstacles to deployment and costs are sometimes higher than expected, but many organizations seeking to provide tighter integration between voice and data view Cisco's offering as a solid solution. Adding wireless capabilities via the 7920 rounds out an already strong product offering. Still, the system is expensive, relies on the proprietary Cisco SCCP protocol and requires Cisco Aironet WLAN infrastructure. In the past, Cisco cooperated closely with wireless vendors like SpectraLink and Symbol, which both provide SCCP-based VoWLAN products, but it appears that Cisco is de-emphasizing those partnerships now that it has its own wireless solution. That's part of the price of buying into proprietary solutions.

The 7920 phones were without doubt the most elegantly designed and most sophisticated phones we reviewed. Cisco took a no-compromise approach on features, appropriate for the enterprise market, but its handsets aren't as rugged as offerings from SpectraLink and Symbol. The 7920's display provided a much cleaner, high-resolution, pixel-based interface than those found on other handsets. They were also the easiest handsets to configure. An excellent configuration menu is built into the phone, but most administrators likely will choose to perform the task via a USB connection to a PC running Cisco's Windows-based management utility, which can store configuration profiles and replicate them to multiple phones. For instance, you could use this to change WEP keys easily.

Cisco's setup wizard is well-designed, providing step-by-step prompts to configure various phone settings. However, we found areas where the user interface could use a little work. For example, initial use of the program requires running and then canceling the setup wizard to import and then access the phone settings. We pointed this and other deficiencies out to Cisco and the company agreed that the interface needed some work. Still, for a 1.0 release we were impressed, especially compared with the SpectraLink and Vocera configuration interfaces.Software updates are performed via TFTP upon phone start-up. However, CCM does not push device configurations to phones automatically, though that capability is planned for a future release. And though Cisco has done a credible job of replicating the functionality of its desktop VoIP phones on the 7920, some capabilities, including phone books and other XML-based applications, are not available on this platform, a deficiency Cisco says will be corrected by the first quarter of next year.

The Cisco 7920 sports a variable-output power capability that lets administrators configure the phones' radios to transmit at levels from 1 mW to 100 mW (0-20 dBm). This feature is useful in dense-AP deployment scenarios found in many enterprise WLAN environments. Lower power output not only reduces the potential for interference, it also helps extend battery life between charges. SpectraLink is the only other vendor to support this variable-output power capability.

The phones communicate using SCCP protocol to manage sessions. You must use Cisco's Aironet wireless access points if you want to take advantage of prioritization of SCCP traffic. Cisco recommends setting up a separate wireless VLAN just for the wireless phones and assigning that VLAN higher priority. It's a smart approach that lets you maintain different security profiles for voice and data traffic. Aironet's Proxy Mobile IP solution is not supported by these devices, so though you can roam between APs on the same network smoothly, you won't be able to roam across IP subnets without dropping calls.

The 7920 phones are registered in the same way as Cisco's desktop phone is registerd. We entered key configuration information (MAC address and telephone extension) into CCM using a well-designed Web-based interface. We also let CCM autoregister phones, assigning extensions automatically. This worked very smoothly, not only for the Cisco 7920 phones, but for the SpectraLink SCCP phones as well.

Cisco is usually closemouthed about future developments, but the company shared its wireless VoIP product road map for the coming year. It's reassuring that Cisco is sensitive to some of its shortcomings, such as multibay chargers and push-to-talk support--or hoot and holler, as Cisco likes to call it. There are also plans to include support for WPA (Wi-Fi Protected Access) security, Layer 3 roaming, local language support, SIP and voice-activated dialing. XML support will allow for access to corporate phone books.The overall performance of the 7920 phone was excellent, exceeding all the other products in both voice quality and range. Voice quality was very clear and the systems did not pick up as much background sound as other products we tested. The 7920 was the only phone able to maintain high-quality sound in spite of the large percentage of out-of-order packets that we threw at it. We walked out of AP range for more than 60 seconds and were able to walk back in and continue our call. We had to verify with a Cisco representative that nothing sneaky was happening to maintain the call.

Although Cisco's phones are easy to recommend, they are expensive. At a retail cost of $595, they were the most expensive of any product tested. In addition, you will need to factor in the cost of CCM infrastructure as well as CCM client licenses.

Cisco Wireless IP Phone 7920, $595. Cisco Systems, (800) 877-0519. www.cisco.comSpectraLink is the current voice over WLAN market leader and it's easy to see why. Its systems are mature and cost-effective, and they can be easily integrated into an existing PBX or Centrex phone system (both analog and digital options are available). At the same time, SpectraLink products have a certain industrial quality to them. Their system components are generic black boxes, and management requires use of an ASCII menu/command-line interface rather than a Web interface. In addition, we had some rather strange experiences upgrading firmware and dealing with battery incompatibilities, and we experienced intermittent failed-connection problems during our initial tests.

SpectraLink's strategy is not to replace your existing PBX, which Cisco proposes, but rather to provide WLAN connectivity into your existing telephony infrastructure. The product line consists of 802.11b wireless phones, the NetLink Telephony Gateway and the NetLink SVP (SpectraLink Voice Protocol) Server. The gateway is a 13-inch-wide box that serves as the link between wireless phones and your legacy telephony environment. The box we received was equipped with Ethernet, analog PBX and serial console interfaces, as well as two RJ-45 ports that stack up to 40 units, allowing for a total system capacity of 640 handsets. SpectraLink's greatest asset is the middleware it has developed to provide digital and analog interoperability with a large number of PBX products, including those from Avaya, Mitel Networks, NEC, Nortel Networks and others. We used an analog interface to connect to our lab's Centrex phone service for our testing.

The SVP server box is similar in shape and size to the telephony gateway and provides QoS enhancements, which are required for environments that have even moderate WLAN traffic. SpectraLink's proprietary SVP QoS mechanism has been integrated into many third-party access points, including those offered by Airespace, Avaya, Cisco, Proxim and Symbol. Packets entering or departing the wireless or wired LAN are routed through the SVP server to get encapsulated or tagged, so that they get priority access when the wireless phones want to communicate on the WLAN. SpectraLink is committed to supporting 802.11e once it's been ratified, but until then, the company is providing its SVP as a tactical solution.

The phones come in two models: the NetLink e340 ($399), designed for office and light use, and the NetLink i640 ($599), engineered for rugged and harsh environments. The two phones are some of the smallest and most durable units we tested. Their industrial utilitarian design includes a four-line text display, and keypads sport a layout similar to a typical cell phone.

The i640 has a push-to-talk feature that allows an unlimited number of persons in one of eight groups to communicate, a service popularized by Nextel and useful in the vertical markets from which SpectraLink derives most of its income. The push-to-talk feature uses multicast to minimize network traffic. The i640 has been designed to withstand a 28-foot drop (we didn't verify the claim but did accidentally drop it on the lab floor once with no apparent damage) and comes with a one-year unconditional warranty. True to its industrial form, a multibay charger is available for the i640.

SpectraLink had sent us some gear a couple of months before we began formal testing, so we ran into a few glitches with older firmware versions. We were unable to power the phones back on after turning them off unless we removed the battery first.Newer handset firmware solved that problem, but the upgrade process was tedious. And even after we had the new firmware installed, the units would power on with a "Bad Battery" message. We had to replace the existing batteries--perhaps part of some effort on SpectraLink's part to discourage the use of other batteries. We were also disappointed to discover that the batteries in the i640 and e340 phones are not interchangeable.

Managing the SpectraLink phone was easy, but unlike some of the other products, it was a decidedly manual process. The phone's interface is controlled using the keypad, and the amount of information you need to input is minimal: SSID, WEP key (if necessary) and the device IP address (we chose DHCP). Every time the phones are powered up, they check to see if they have the latest firmware installed. If not, it is retrieved via TFTP and the phones restart themselves. This check takes only a few seconds, but provides an easy way to deploy new code.

Although there is no Web interface on the telephony gateway, the text-based menu interface, accessible via serial port or telnet, is well-designed. There is also limited SNMP alert support on the gateway. Installing a device is as simple as going to the registration menu and selecting "On Air Register." The next time a phone is turned on, the MAC address of the phone is added to the list and a device name and phone extension can be assigned. One shortcoming of the registration process is that the phone's extension, as set in the menu, is not transmitted back to the phone. This could easily cause confusion, as it did for us.

Because the gateway is not a call manager, calls made from phone to phone always go through the PBX or analog interface. If you want more of a peer-to-peer VoIP environment, you can use SpectraLink phones on Cisco's CCM, since SpectraLink phones support SCCP. By changing the license type and SSID, we were able to make calls from our SpectraLink phones to Cisco VoIP clients. SpectraLink has mapped most of the features of the Cisco 7960 VoIP phone onto its system. Alas, you'll need to pay an extra $50 per device for an SCCP license, not to mention a Cisco CCM client license.

We experienced intermittent "No Gateway Found" messages during our initial testing using Cisco 1200 APs. SpectraLink acknowledged that there are outstanding problems with the Cisco 1200 APs, and the company recommended that we use the Cisco 350. Nevertheless, we still experienced problems until we cycled the power on the gateway and the SVP server. Once we got past these problems, the coverage was good and the phones performed as promised with good overall voice quality. The system performed well with moderate packet loss, but it did not handle our out-of-order packet test very effectively, resulting in muddy voice quality. The system performed well with Layer 2 roaming between APs.SpectraLink NetLink Wireless Telephones; NetLink e340, $399; NetLink i640, $599. SpectraLink Corp., (303) 440 5330, (800) 676-5465. www.spectralink.comSymbol has been a leader in mobile computing and wireless for many years, with particular strength in vertical markets, such as retail and distribution. For organizations that have deployed Symbol handhelds and wireless infrastructure to support business processes, adding voice capabilities makes a lot of sense. That's the primary market Symbol is addressing with its NetVision phones. We liked the design of these phones, but overall performance and functionality was somewhat disappointing.

We received two NetVision phones, as well as an Ericsson WebSwitch 100 voice gateway. Symbol gained its initial expertise in the VoIP market from a relationship with Selsius Systems, which was subsequently acquired by Cisco. Symbol acknowledged that the wireless VoIP market hasn't taken off to the degree hoped for, and it appears that the company's VoIP products aren't getting much attention from a development standpoint. Nonetheless, Symbol is still committed to being a player in this market. Much of the company's work is focused on incorporating voice capabilities into its handheld PocketPC based computing/bar-code readers. We think that strategy makes more sense for Symbol than producing a separate VoIP phone. Unfortunately, those products are not yet available for testing.

The NetVision phones are easy to configure. The Symbol-provided serial cable supports a CLI-based configuration via HyperTerminal or a more graphical Windows-based Netvision Phone Administrator interface. The software is based on the concept of sites. We configured a site with settings such as SSID and default phone preferences, and then added each phone to the site and uploaded the settings. This didn't always work, depending on the state of the phone and its previous settings, but a power cycle usually solved the problem. Because configuration is serial-based, it doesn't suffer from the annoying USB-disconnection warning that we experienced with Cisco's product. We were also able to configure user lists and PINs for each phone so that different people could share a single phone.

To make IP-phone-to-IP-phone calls, we had to use the command-line interface to add the phone IP addresses manually. Normally, a user would just call the extension number of the other phone and the PBX/gateway would make the connection, but our Centrex environment didn't let us test it in that mode. We would have liked to see something a little more transparent in making these peer-to-peer calls. Even under ideal network conditions, when we made calls with the NetVision phones, we perceived delays in speech that were much more noticeable than with other products. This was a little disconcerting for us because we could see the delay through windows in our lab, but for typical usage where the callers are not in visual range, it would not adversely impact communication.

We liked the system's easily accessible address book, something that none of the other phones provided. But on the whole, we found the phones from Cisco and SpectraLink somewhat more like cell phones and thus more intuitive for the typical user.

Symbol also provides SVP support, but this time it's Symbol Voice Protocol. It uses RTP (Realtime Transport Protocol) transport of audio streams. At least someone uses open standards! Any AP capable of prioritizing RTP traffic can provide higher priority for NetVision phones. Support for this mechanism is provided via checkbox on Cisco's 350 and 1200 series APs, and is also supported on Symbol's APs.

We wanted to test a Symbol phone with SCCP support, but the code that Symbol currently offers won't work with Cisco Call Manager 3.3(3), the version we used during testing. Symbol is re-evaluating its relationship with Cisco now that Cisco has its own competitive offering.

In our testing, the NetVision phone did not perform as well as the SpectraLink and Cisco offerings. It had the worst results for both voice quality and range. Range limitations might not be a huge issue for organizations with dense AP deployments, but that's not usually the case in enterprises that are the primary target market for these devices. When we walked to the fringes of the product's coverage areas, the system dropped calls, requiring us to constantly redial the other phone to continue. We did not experience any problems with Layer 2 roaming.At $580, the Symbol phones are priced just under the Cisco offering. That strikes us as a little expensive in light of the product's performance and may act to restrict the market to existing Symbol customers who value that business relationship.

Symbol NetVision Phone, $580. Symbol Technologies, (800) 722-6234. www.symbol.comTelesym is an established player in the soft-phone VoIP market, specializing in Pocket-PC-based devices. Although a number of vendors have begun to release soft-phone platforms for Pocket PC, Telesym delivers a full--albeit proprietary--VoIP telephone platform, including a call manager and integration with legacy phone systems. When we first tested its product in December 2002, we felt the system had potential, but the client interface was crude and the system was only compatible with the 3Com NBX 100 VoIP system.

The company has come a long way since then. The overall architecture remains unchanged: the SymPhone VoIP Call Server interconnects SymPhone clients over your IP-based intranet or the internet, and the SymPhone Connector (which supports the Intel Dialogic digital and analog telephony interfaces) provides an interface to your PBX and the PSTN. We installed the SymPhone Call Server and SymPhone Connectors on separate Windows 2000 Servers.

At the client end, we used two Compaq iPAQ 3800-series PDAs running Pocket-PC 2002 with CF (compact flash) wireless NICs from Symbol Technologies and Socket Communications. The overall performance of SymPhone is dependent on the PDA's sound subsystem. TeleSym can provide advice on which PDA products perform best (see www.telesym.com/support.php?page=recommended). It's worth noting that many Pocket PC systems have poor audio software and hardware, and most do not include combo headphone-microphone jacks, which makes it impossible to use typical cell-phone headsets. Industrial-grade portable computing devices from vendors like Intermec and Symbol have recently been released with standard 2.5-mm headphone/mic interfaces.

The install footprint for the SymPhone client has grown only slightly since our last tests-- from 500 KB to 612 KB, but the interface has improved significantly. We were pleased to find that we could talk on the phone while running other Pocket PC applications without any noticeable performance degradation.Setup was easy with the client application installed via ActiveSync from a device cradled to our desktop PC. Enterprises rolling out lots of devices can distribute CAB installation files from a third-party mobile device-management system. Although TeleSym is placing significant emphasis on WLAN connectivity, the system can be used from any broadband network connection. Many TeleSym customers use the product on the road with an Ethernet interface when WLAN services are not available. You could even use this system across 2.5-G CDMA and GPRS networks, as long as they supported IP connections in excess of 56 Kbps.

Although many organizations likely will be interested in taking advantage of the system's ability to integrate with existing telephony services, it's possible to implement TeleSym as a replacement for an internal walkie-talkie-type system with full multiparty intercom support.We ran the TeleSym system using a Dialogic analog interface to our Centrex system. It was easy to associate specific SymPhone devices with our phone numbers. TeleSym offers a demonstration call manager and telephony connector on a server in its Seattle office. Users can download and install SymPhone and make test calls across the PSTN to a Seattle number, a toll-free number or long distance to another phone using a calling card.

Under normal conditions, SymPhone call quality was excellent on our test iPaqs. The fidelity, particularly with headphones, was outstanding. TeleSym prides itself on the ability to maintain connections under highly variable network conditions and significant packet loss. We certainly noticed a difference between TeleSym and other products we tested. While network problems are typically manifested on most products through garbled sound or momentary drops, sound on the SymPhone platform remained intelligible under heavy packet loss, but it sounded like it was put through a flange or drain pipe sound effect. Out-of-order packets had acceptable, though not perfect, call quality.

SymPhone's range depends entirely on the client wireless interface you are running. We chose to test using Symbol and Socket WLAN CF Cards on our iPaq's because our previous experience suggests that they offer the best combination of range and performance. Range using this combination proved very good.

Many users will be less comfortable with a Pocket PC soft phone than with one of the more conventional form-factor wireless phones from Cisco, SpectraLink or Symbol. Although SymPhone supports a full range of standard phone features, including caller ID, hold and speed-dial from a contact list, generic Pocket PC devices require the use of a simulated keypad interface, which takes some getting used to. On the positive side, for organizations that have deployed PDAs to support other applications, the incremental cost of supporting telephony consists of simply installing the SymPhone software. And because they also support a standard Windows client, you can access VoIP phone services from that platform as well.

SymPhone NP System, $500 per user. TeleSym, (425) 233-3800, (800) 493-7518. www.telesym.comWhile all the products we tested drew the interest of lab visitors during our testing, Vocera's offering drew the biggest oohs and aahs. Indeed, Vocera's wireless VoIP solution has to be one of the slickest systems we've ever tested, providing wireless VoIP services on a miniature 1.5x4.5-inch wireless speakerphone weighing just 2 ounces--the Vocera Badge--using an intuitive spoken-command interface. The badges, which attach to your shirt with a clip or are worn around the neck using a lanyard, communicate via 802.11b with the Vocera server system, which manages call activity and provides connections to legacy telephony environments. Vocera shipped us several badges (including single-bay and eight-bay chargers) and a server equipped with Intel Dialogic analog interfaces to our Centrex phone service. Support for digital PBX interfaces is coming in version 2.0. Vocera's recommended server configuration is a 2-GHz CPU, 1 GB of RAM and 20 GB of disk storage.Vocera's offering is clearly different than the other products and is best-suited for environments where hands-free communication is needed and a voice-recognition telephony interface is desirable. Vocera's current primary target market, health care, clearly fits that mold. Most hospitals prohibit the use of cell phones, so VoWLAN provides a useful alternative for in-building voice communication.

The Windows-based Vocera server, which is managed through a well-thought-out Web interface, integrates a range of functions, including user management, call management, telephony connection management and speech recognition. We were able to manage user profiles and preferences, monitor system operation and create groups that can be used to manage one-to-many communications capabilities. At this time there is no way to leverage an existing enterprise directory for authentication, but there are interfaces to bulk-add users. Individual users also have control of many preferences, including call forwarding to/from desk phones, with some preferences configurable via both the Web interface and through voice commands. The Vocera server also includes complete voice-enabled voicemail capabilities.

Badge configuration is performed over the wireless network through a CLI from a network-attached PC. Although this system requires some training, its ability to generate automated scripts using the CLI language allows routine device configuration to be processed efficiently.Commands and call placement are done through voice commands issued to the Vocera badge (e.g., Call Frank Bulk). Vocera licenses voice-recognition technology from Nuance Communications. The voice recognition adds to the coolness factor of the devices, but also represents an Achilles' heel. There's no question that voice response has improved significantly in recent years, and Vocera has done a credible job of exploiting its power. However, since the voice commands themselves are digitized and sent over the wireless network to the server's speech-recognition engine (an 8-Kbps codec is used during conversation, but a full 64 Kbps is used to get the best quality when using voice commands), high packet loss and high background noise can cause the system to have trouble processing voice commands. Using a headset with a high-quality microphone can help. Under normal conditions, voice recognition proved extremely effective, but during some of our harsher simulated network conditions, the badges became a little difficult to use as the quality of voice recognition dropped.

Vocera relies on WEP for encryption services together with a sophisticated optional voiceprint-based authentication system. Once you initialize the system, it compares subsequent login attempts to the stored voiceprint. Vocera claims the system will continue to refine the voiceprint through subsequent use and eventually "capture the behavioral characteristics of the way a person speaks." This is a relatively new form of biometrics and our first opportunity to evaluate such a system. Aside from a slight delay during authentication, the system worked as advertised during testing. Vocera's Web site includes a white paper that provides detailed implementation guidelines designed to ensure HIPAA compliance, which is important given the company's target health-care market.

We easily integrated the Vocera system into our Centrex environment by using the telephony server together with a Dialogic analog voice interface. Using voice commands, we were able to request outside lines and make phone calls on the PSTN. It all worked without a hitch.

Overall, call quality with the Vocera badges was very good, despite the system's low-bandwidth requirements, particularly considering the microphone is usually located somewhere around the user's chest. Even under simulated network congestion, call quality remained consistently good. Range was also impressive, particularly considering the small size of the Vocera badges. Layer 2 roaming delays were virtually imperceptible.

Vocera's VoIP solution represents one of the more extensible solutions we tested. The broadcast message functions, user location and voice-recognition approach are some of the most innovative ideas we've seen. The only drawback to the Vocera approach is that voice recognition requires a good amount of both server and network overhead because the commands are issued over their own data streams. For those who find standards important to their enterprise, Vocera does not currently use SIP, but plans to add limited support for it in the future.Vocera Communications System, $6,500 (6-user Vocera Server Software License and four Communications Badges). Vocera Communications, (408) 790-4100, (800) 331-6356. www.vocera.com

Dave Molta is a Network Computing senior technology editor. He is also assistant dean for technology at the School of Information Studies at Syracuse University and director of the Center for Emerging Network Technologies. Molta's experience includes 15 years in IT and network management. Write to him at [email protected].

Sean Ginevan is a technology associate with the Center for Emerging Network Technologies at Syracuse University. Write to him at [email protected].

Frank Bulk is a technology associate with the Center for Emerging Network Technologies at Syracuse University. Write to him at [email protected].

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Is the marriage of voice over IP and wireless LANs a boon for the enterprise or one more headache for overloaded IT managers? The answer depends on both the scope and the timeframe of your proposed deployment. Today's offerings are maturing quickly, but the costs are still high, and standards and performance problems remain.We tested five VoWLAN (voice over wireless LAN) offerings--from Cisco Systems, SpectraLink Corp., Symbol Technologies, TeleSym and Vocera Communications--and were impressed with their capabilities. These systems provide mainstream telephony services over an existing WLAN infrastructure, including access through gateways to PBXs and the PSTN. Some of the products offer innovative capabilities, including multiparty intercom features and voice recognition. In our tests we found voice quality very good under lightly loaded network conditions, but network congestion can lead to unpredictable performance with some products, even if the platforms include basic quality and class-of-service guarantees.

For the immediate future, these products have the greatest appeal to vertical markets, such as health care, education, manufacturing, distribution and retail, but broader enterprise deployments are inevitable, particularly if next-generation WLAN infrastructure makes its way into a larger percentage of enterprises in 2004. System costs are still high, but we expect to see prices drop dramatically in the next two years. And we hope to see vendors make the move from proprietary protocols to standards like SIP (Session Initiation Protocol), a change that will enhance interoperability and push down costs.Standard methodologies for testing VoWLAN systems have not yet been developed, and many of the tools that can be used for wired VoIP systems cannot be used with wireless because they rely on wired Ethernet connectivity. Our primary goal in testing VoWLAN systems was to assess call quality under typical office conditions and under an environment with considerable background noise. We evaluated performance under both normal network conditions and congested conditions.

Our wireless test network used Cisco 1200 APs (access points), except in the case of SpectraLink and Cisco, which recommended the use of 350 APs. To measure voice quality, one wireless VoIP phone was placed near a speaker, where we played a professionally recorded audio speech. We then assessed sound quality using another phone from a different room, averaging the results of two independent testers listening to a minimum of one minute of source material. We graded each product on a 10-point scale. During these tests, we used the internal microphone/speaker as well as a headset for listening.

To simulate less-than-ideal network conditions, each device (source and destination) was assigned a unique SSID and associated with a different AP. The APs were connected to a Shunra Storm network simulator, where we introduced a variety of network problems. The first of these conditions was an aggregate round-trip packet loss of 10 percent, 20 percent, 35 percent and 60 percent. We also evaluated the effect of out-of-order packets, creating a model where packets had a 50 percent chance on either network port of being out of order. Finally, we simulated connection drops, where the device is still associated but wired network connection is not available.

In a slightly more real-world test, we set up 13 WLAN clients (a mix of Toshiba and Dell laptops using a combination of Cisco 350, Orinoco and onboard wireless NICs) performing NetIQ Chariot long-file transfers to simulate a condition of heavy WLAN traffic load.

In addition to performance tests, we conducted our standard range testing on the first floor of the Center for Science and Technology at Syracuse University. In order to allow for appropriate product-to-product comparisons, all range tests were conducted using Cisco 350 APs installed in a typical ceiling-level location. Although the Cisco 7920 had the best range, all of the products were roughly comparable, except for the Symbol NetVision, which had a much more limited range. See "WLAN Range Map," for a graphical depiction of our range tests.

Finally, to evaluate the effects of Layer 2 roaming, we set up two Cisco 350 APs on nonoverlapping channels with identical SSIDs, both configured at 1 mW (0 dBm) power output. Because the low power output created very small cells, we were able to assess the point at which each device roamed and the effect of roaming on call quality. --Sean GinevanThe increasing popularity of SIP (Session Initiation Protocol) has predictably stimulated the release of SIP-compatible soft phones, both for Windows and PDA platforms. Many of these soft phones are being touted as compatible with wireless LANs, so we decided to do a quick assessment of several of them.

SoftJoy Labs' SJphone is available on both Pocket PC and Windows platforms. Installation was very easy and followed the standard Microsoft ActiveSync procedure. We found the interface clunky compared with SymPhone, but essential features are all there. SJphone offers support for H.323 and SIP; we tested using SIP with an internal SIP server. Overall performance was adequate at best, with significant delay. Headphones are a must.

Xten's X-Pro (bottom left), a Pocket PC SIP soft phone, sports an extremely slick user interface that replicates an LCD display. We found the long startup time to be a significant annoyance, made worse by the fact that it is easy to exit the program accidentally. There are convenient microphone and speaker volume controls on the main screen, as well as mute, transfer and conference buttons. X-Pro supports multiple SIP proxies and has a full array of SIP options and tweaks. Xten also offers Windows and Mac OS versions of its software.

Although VLI's Gphone software seems to be targeted at personal users, the company also offers solutions for enterprise customers that use Pocket PC, PalmOS and Windows platforms. We looked at the Pocket PC version (Palm version, above). The heart of the Gphone system is the Gphone Buddy Service, a subscription-based Internet directory service. An enterprise version of the Gphone Buddy Server can be deployed inside the firewall. We found the Gphone interface relatively easy to use. Voice quality wasn't stellar, but we liked the product's ability to support text chats and file transfers during a phone call. We also were able to use other applications during a call without significant performance degradation. One can hardly mention VoIP without saying something about QoS (Quality of Service). For several years, VoIP developers have wrestled with the challenge of delivering high-quality telephony services over packet-switched networks, adopting an array of strategies to prioritize traffic. The requirements for wireless VoIP are similar, but the implementation challenges are even greater. The IEEE's 802.11e working group has been developing QoS enhancements to the 802.11 MAC since late 2000, and 2004 may be the year these specs find their way into the market.Most of today's 802.11 networks rely on the CSMA/CA MAC (media access control) protocol in conjunction with DCF (Distributed Coordination Function). The 802.11 standard provides for an alternative PCF (Point Coordination Function), which provides basic QoS capabilities, but it is generally considered too inefficient and too limited to support emerging needs. The 802.11e draft provides for two more mechanisms: EDCF (Enhanced DCF) and HCF (Hybrid Coordination Function). EDCF improves upon the existing DCF MAC specification by supporting up to eight priority traffic classes that map directly to the RSVP protocol priority levels.

Although stations are constantly transmitting and attempting to gain access to the medium, there are idle times between transmissions called interframe spaces. Several such spaces are already defined in 802.11, including SIFS, PIFS and DIFS. EDCF adds AIFS (Arbitration Interframe Space). Higher priority traffic will have lower AIFS idle times, providing media access priority over other stations. Even if there are several stations within the same priority traffic class, there is still a variable length contention window with its own countdown. HCF builds upon PCF's round-robin polling mechanism by providing more intelligent polling algorithms.

Since the IEEE 802.11e group is not expected to approve a QoS standard until mid-2004 at the earliest, interim QoS industry standards have begun to appear, in large part to address the needs of developers wishing to distribute multimedia content over WLANs. The WME (Wireless Multimedia Enhancements) standard has been touted as a stand-in for the uncompleted 802.11e. Already, Atheros Communications, Broadcom and Intersil are producing chipsets that include support for the WME standard. Cisco has pushed the envelope a bit by implementing a November 2002 draft specification of 802.11e in its newer products and firmware sets.

Most of the systems we reviewed took one of two approaches. SpectraLink has for several years offered its own voice-priority specification, SVP (SpectraLink Voice Priority), and support for the standard has been incorporated into many products from vendors such as Airespace, Avaya, Cisco, Enterasys, Intermec, Proxim and Symbol. SVP operates through a queuing mechanism built into the access points that provides priority to packets like voice that require real-time processing.

An alternative approach, such as the one used by Cisco on its upstream connection, involves lowering the value of the 802.11DCF CWmin (minimum contention window) parameter, which controls the idle wait time between frames used to determine when devices can transmit. Wireless devices choose a random value between 0 and CWmin before transmitting. Most wireless NICs and other devices have a CWmin value of 32 defined, so that on average, they must wait for 15.5 idle slots to pass by before they can transmit. Wireless phones that want early access to the medium merely lower their CWmin to 0 or 1, so that at most they need to wait only 1 idle slot before transmitting. This works well if there is only one device that has a small CWmin, but if there are multiple devices requiring prioritized access, it can lead to high collision rates. --Frank Bulk