Netvision Wireless Phone System

By Fred Heiman, Executive Vice President, Symbol Technologies, Inc.

A History of Innovation Continues

Building on its history of technological innovation, Symbol Technologies is adding a breakthrough new product to its family of Spectrum24^®-based wireless LAN appliances, called the NetVision^® Phone. It looks and functions like an ordinary cell phone, with one big advantage - you don't pay for calls between locations covered by your company's internal data network. And, with the addition of a gateway, you can make and receive calls over the public switched telephone network. It's like having a cell phone at work, without paying cell phone charges.

The NetVision^® Phone is based on revolutionary new technology called 'Voice-Over-IP', a technique for sending real-time full duplex voice communications over the internet or internal IP network.

As the name implies, voice information can be sent over the Internet, or over a company's internal TCP/IP network or Intranet, just like email. Only a few conversions are required to the voice signal.

Converting From Voice To Data

First, digital samples of the analog voice signal are obtained with a common chip called a CODEC, which stands for Coder-Decoder. For telephone quality sound, 8-bit samples taken at a rate of 8,000 per second result in a data rate of 64 Kbps, as shown in Figure 1.

Since there is silence and redundancy in voice, the signal can be compressed by about a factor of 10 to minimize the amount of data that needs to be transmitted. This is done with a special chip called a digital signal processing chip, which conforms to internationally-accepted compression standards.

Next, data packets are created from the compressed data bit stream and put in a format that is suitable for transmission over a TCP/IP data network. Typically, a small packet of about 130 bytes, which includes the TCP/IP overhead, is sent every 30 milliseconds, as shown in Figure 2. At the other end, the process is reversed. The packets are converted to a serial data stream, uncompressed and converted back to an analog voice signal. The entire process, including call set-up, is described in the international standard H.323. The NetVision^® phone system is based on this specification.

Normal data traffic is carried between PCs, servers, printers and other networked devices through a company's worldwide TCP/IP network, as shown in Figure 3. Each device on the network has an IP address, which is attached to every packet for routing. Voice-Over-IP packets are no different. To place a call from one PC to another, simply enter the IP address of the called party using one of several voice conferencing software packages available today, such as NetMeeting^TM from Microsoft or ProShare^TM from Intel.

Intranet and Public Switched Network Calls

With Symbol's Spectrum24^® wireless network installed, you can use your portable NetVision^® Phone to talk to other IP phones or to desktop PC-based phones located at any company site, worldwide, provided that a Spectrum24^® network is installed at the site (see Figure 4). Since the voice packets travel over the data network, there are no charges for these calls. The system is fast and designed to coexist with other data transactions on the network.

Since the voice transmission is compressed to less than 1,000 bytes per second, even dozens of simultaneous phone calls represent very little data traffic. In fact, each Spectrum24^® access point can handle more than 25 simultaneous, full-duplex calls. For added flexibility, convenience and return on investment, calls can be made out to the Public Switched Telephone network, with the addition of a gateway.

The gateway shown in Figure 5, such as the model 3620 Voice-Over-IP router from Cisco Systems, performs functions similar to the NetVision^® Phone. But instead of passing the analog voice signal out through a telephone handset, it places the signal over a telephone line. This line can run into your PBX system, or into the public switched telephone network, allowing users of NetVision^® phones to make and receive traditional telephone calls -to anywhere in the world. Of course, toll charges apply to these traditional telephone calls.

Added Features For Added Value

Use the NetVision^® Phone like an ordinary cell phone. It can be programmed with a telephone directory for easy speed dialing of both internal IP calls and external calls. Press 9 for an outside line and you will hear the standard dial tone transmitted directly from the telephone line. It features call waiting and caller identification. Calls can be forwarded, placed on hold and two calls can be conferenced. Remember, there are no charges for calls placed over the internal data network to company sites anywhere in the world.

The addition of the NetVision^® Phone, as well as other LAN appliances and capabilities, such as pagers and browsers, to the Spectrum24^® wireless network, clearly demonstrates our continued commitment to innovation that is the hallmark of Symbol Technologies. Installation of the NetVision^® Phone System into business-critical applications in retail, healthcare and package delivery, where the Spectrum24^® wireless LAN infrastructure already exists, is as easy as assigning an IP address to each wireless handset. This innovation could be the spark that opens up the nascent wireless LAN market for office applications around the world. No additional infrastructure cost is incurred in implementing the NetVision^® Phone system, greatly enhancing the value of their Spectrum24^® network.

NetVision^® Phone Features:

• 3-line display
• Headset port
• External serial port
• Vibrating, visual and audio ring signals
• Volume control for ringer and handset
• Call waiting
• Call forwarding/transfer
• Redial key/busy redial
• Speed dial/Address book
• Last number redial
• Paging
• External (POTS/PBX) calls via gateway
• Roaming
• Caller ID
• Mute/Hold