SymPhone Organizes and Takes Calls

If your environment combines PDAs and WLANs or you are planning to deploy one that does, take a look at this voice-over-WLAN application.

December 9, 2002

6 Min Read
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SymPhone consists of three main software components: the SymPhone Client; the SymPhone Call Server; and the SymPhone Connector for the 3Com NBX 100. The Client is a VoIP softphone that runs on PDAs using Microsoft Pocket PC 2002. The interface includes an easy-to-use dial pad, a directory and intercom features. The Call Server enables SymPhone to make peer-to-peer calls within an enterprise and provides real-time call-lookup capabilities. The Connector works with 3Com's NBX 100 to extend SymPhone's capabilities to the public switched telephone network so you can make and receive calls to any telephone in the world. TeleSym is currently working on supporting other VoIP PBX products.

You can evaluate SymPhone free for 30 days using TeleSym's Connector, which is installed at the company's facility in Seattle. This will give you an idea of how the system works over the Internet connecting to a 3Com NBX 100 at a remote location. With the download, you can make local calls to Seattle-area exchanges for free. For long-distance calls, you'll need to use a credit card. For evaluation purposes, TeleSym provided us with free long-distance access. After making a number of calls, we can say the system worked remarkably well.

In the future, TeleSym plans to bundle the 3Com NBX 100, Connector and Call Server to run on a single server. We persuaded TeleSym to send a 3Com NBX 100 to our Syracuse Labs for testing. After getting a little help from TeleSym on the NBX 100 setup, we checked it out using a variety of lab wireless equipment, ranging from a high-end Cisco Aironet 350 Access Point to a D-Link SOHO router. It ran as expected.

We installed the 500-KB-footprint SymPhone Client on a 3800 series Compaq iPaq, a Toshiba E740, an Intermec 700 and an HP Jornada. Although all the more popular clients are available for download on TeleSym's Web site, we had to specifically request a build for the Intermec device--a specialized Pocket PC handheld computer with integrated WiFi wireless and a small keyboard. What sets the Intermec device apart for this application is its combination headphone/microphone jack, which lets you use traditional cell phone headsets. In contrast, while you can listen through the headphones for standard Pocket PC devices, you need to speak into the integrated microphone.

The Tests and The Results

To see the SymPhone in action, we simulated VoIP traffic on our WLAN using NetIQ's Chariot 4.3 with the latest VoIP endpoints using the G.711u codec. With 30 simultaneous calls (64 Kbps each direction) on the network, we initiated a call with the SymPhone and experienced a round-trip delay of approximately 185 milliseconds. Under congestion, the average lost data between the endpoints was 70 percent. Dropping the number of calls to 20, we observed that the SymPhone's integrated call-quality meter changed from "poor" to "good." With 10 calls, round-trip latency averaged 70 milliseconds and average data loss between the endpoints was less than one percent. With no additional VoIP traffic, the meter returned to normal. Even under significant congestion, SymPhone's voice quality was good. It's important to note, however, that normal sound for the SymPhone is nothing short of spectacular; it approaches CD quality. TeleSym obviously has spent a lot of time and effort tuning the codec for high quality.

We also tested the effects of call quality while moving in and out of access point range. Calls were interrupted when moving out of range, but reconnected when we came back into range. Although the SymPhone indicated that it was trying to re-establish the call, there was no indication to the party who stayed within range that we had moved out of range and were trying to re-establish the call. The average time before the call was actually dropped was around 55 seconds--a tad long. Happily, SymPhone calls reconnected even when the Cisco network card or Symbol compact flash card was removed and re-inserted.

The Client

The SymPhone Client is unique in a few ways. Rather than dialing with the tiny stylus that comes with the PDA, you can exercise your fingers with a full-screen dial pad. Additionally, the phonebook is integrated with Microsoft Outlook and is only a touch away from the dial pad.

Under Options, SymPhone displays such current settings as IP address, subnet mask, default gateway and DNS servers used by the PDA. This is very helpful when trying to troubleshoot networking issues. Most vendors only provide a view of your association and signal strength with the access point.

SymPhone takes another step toward making mobile life simpler by providing a profile option. We configured two different profile SSIDs: one for the lab and one for the home. Rather than change the network settings when we moved from lab to home and back, we only needed to change the profile.

With SymPhone, you also can specify power-up behavior as well as walkie-talkie and intercom settings. The power behavior settings let you start SymPhone when the PDA is powered on, or you can start it manually for more control over the applications running on your PDA. The walkie-talkie mode is half-duplex, and it might be useful for PDA-to-PDA conversations. The intercom feature, which is similar to that provided on NexTel cell phones, comes in handy if you want to page all the PDAs in your network simply by pressing a button on your PDA. You can even indicate what personal information is displayed to the other party's PDA when calls are made. Plus, SymPhone indicates whether a Call Server was located and lets you configure a Connector's IP address with ease.

Finally, the quality meter and ready indicator are very useful in determining the levels of call quality and connectivity, respectively, to the Call Server. Although not currently provided, call history, redial and voicemail indicators would be among the more useful features, and TeleSym indicated that these offerings are scheduled in the next release.

We Want SymPhone

SymPhone has some great applications in enterprises, factories, warehouses and retailing environments where WLANs and PDAs are used to provide mobile applications. It's also a handy tool for organizations that have 3Com NBX 100 VoIP systems installed and wish to provide employees with same-number access both in the office and on the road--basically, anywhere they have WLAN access. The system offers excellent voice quality and very low latency, even under conditions of fairly high traffic contention.

Saurabh Bhasin is a research associate with the Center for Emerging Network Technologies at Syracuse, N.Y. He has extensive experience in open-source, systems administration and various wireless networking technologies. Send your comments on this article to him at [email protected].

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