A SIDEBAR- from the February, 1999 issue of Aviation International News

Scott Smith, airborne email expert and managing partner of Empire D & D, Inc.


Scott Smith is the reigning champion of airborne email.

An international captain with the Texas Instruments flight department, Smith has gradually taken on the role of chief airborne email guru at his company. Four years ago, TI installed its first AT&T AT-496 two-transceiver digital radiotelephone in one of its Challengers. The installation didn't go smoothly, and Smith ended up helping troubleshoot some antenna and rack bonding problems. Then, having had a longtime interest in personal computers, Smith became interested in using the radiotelephone to send and receive email. Once the installation problems were resolved, Smith found that emailing was a hit and miss proposition. Sometimes it would work, many times it failed. "It took quite a while to figure out it was the modem," he said. After months of testing a huge variety of notebook computers, Smith consulted with engineers at Texas Instruments and finally figured out that modems containing AT&T chipsets were not compatible with AT&T's digital radiotelephone. [The AT&T radiotelephone network was included in AT&T's purchase of McCaw Cellular-Ed.] Smith was instrumental in discovering the AT&T chipset problem and immediately notified engineers at AT&T Wireless. The most compatible chipset for the AT&T radiotelephone, he found, is

Rockwell's, which is common in modern modems. Once those problems were solved, TI's corporate passengers started logging on during every flight. "Before we had airborne email," Smith said, "maybe one in ten passengers would get onboard with a notebook computer. Now every one is there with a laptop." To ensure that passengers would achieve success in airborne emailing, Smith, who is also the flight department network manager, makes sure that all notebooks that are used on the airplane are configured properly. (See box page 00). In the beginning, Smith did this work himself, but it took too much of his time so he wrote up instructions for TI's information services department, which now handles notebook configuration.

TI's flight department is based at Love Field in Dallas, which is convenient because the airport has an AT&T ground station to serve its phones installed on the Southwest Airlines 737 fleet, as well as in local corporate operators' aircraft. TI passengers cope with "a huge amount of email correspondence," Smith said. "We have some who get 100 to 150 messages a day." They log on as soon as they climb into the airplane, he said. "Now, if you get onboard without a computer, everybody's trying to figure out what's wrong with you." The Challengers have AC outlets and AT&T fax adaptors at most seats. The AT-496 systems in the Challengers allow two simultaneous 4,800 bps data calls. Most users spend an average of seven minutes per call up- and downloading email, Smith said. TI has two Challenger 604s undergoing completion at KC Aviation in Dallas. Instead of installing the AT-496, which is really an airline product and must be installed inside the pressure vessel, the 604s will feature dual RT-108s tied together by a satellite interface unit. AT&T is completing final testing of its SIU, and this will not only allow an AT&T handset to be used for satcom, but will make two RT-108s work together like a dual-transceiver AT-496.

When it came time to decide how to equip the new 604s, Smith, with his networking background, figured there's no reason a local-area network couldn't work in an airplane. The advantages of a network are many and include the fact that all calls can be routed through one modem installed in the network's central server computer. "If I do a network," Smith said, "I'm dealing with one modem. Its our modem, we have control over it, we configure it. Nobody else has to worry about changes to their computer." Instead of plugging a modem in a notebook computer into the handset or fax adaptor, in the 604s, TI passengers will plug into an RJ-45 (network) jack next to their seats. Their notebooks will not have modems but will be equipped with network interface cards (credit-card style PC Cards). If someone wants to send or receive email, they simply do so using the software installed on their notebook. This sends a request to the network server, a Compaq Proliant 850 running Windows NT 4.0, which then makes the data call to the ground. All passengers can do their emailing at any time. The network queues the requests and takes care of them one at a time. To passengers, this network activity will be transparent. Depending on how much traffic there is through the server, email could be delayed waiting for everyone's request to get through the 4,800 bps AT&T radiotelephone line, but most people don't expect instant responses to email anyway. With the 604s, Smith is going beyond a network relying on one modem and the two RT-108s' data lines. On the ground, networks share information via packet-mode, instead of circuit-mode, which is what a normal analog phone call uses. Analog circuit-mode calls take up all available bandwidth in a given phone line. Data sent via packet-mode is divided into small "packets," usually about 16 bytes, but it varies from system to system. Each packet contains some data and the destination information. Network traffic, like an email message, can be split into many packets and sent via the Internet to the message's destination. Each packet could travel entirely independent routes to reach the destination because the necessary routing information is contained in the packet. The bottom line is that packet-mode data is much faster than sending something via circuit-mode.

The current TI Challenger setup and even the network server with modem described above still uses circuit-mode for the communications link from the air to the ground. The process is cumbersome and looks like this:

1. An email message is created inside the computer. The message is digital.

2. The modem converts the message to an analog signal that can be sent on a
phone line or radiotelephone connection.

3. At the AT&T handset or fax adaptor, the message is converted back to
digital, because that is what the AT&T system uses for its internal
architecture (it's actually ISDN).

4. At the transceiver, the message is sent to a ground station, where it is converted back to analog to travel over circuit-mode phone lines.

5. The message is converted back to digital when it is delivered to the recipient's email box, awaiting retrieval. This back-and-forth conversion, which involves a lot of error checking, imposes a burden on the system, partially explaining why the AT&T system offers data transmission at just 4,800 bps. "Every time it converts," Smith said, "it takes time and bandwidth and overhead." What if, he wondered, we could set up a packet-mode pipe to the airplane? At a meeting with AT&T Wireless engineers and executives at the division's headquarters in Seattle, Wash., Smith was asked what the company could do to fulfill TI's airborne telecommunications needs. He asked for a packet-mode pipe to TI's airplanes, connected to the server. "I told them I'd handle the
network end of it. All I need is the connection from their radio to our computer."

It turned out the AT&T engineers had been working on just such a project, what Smith calls "an ISDN line to the airplane." Of course, data rates will be nowhere near as fast as ISDN, but much improved over the current 4,800 bps. With a network interface card installed in one of the AT&T transceivers installed in the 604, AT&T plans to keep a packet-mode pipe live in real-time up to the airplane. AT&T's work involves software changes and the design of the network interface card for the transceiver. The AT&T radiotelephone network already tracks digital RT-equipped airplanes, so there is no big bandwidth draw to make the system live all the time in packet mode.

The limited number of channels on the AT&T radiotelephone network means that a certain number of callers can overwhelm the system, which restricts access to additional users. A busy morning at Love Field, for example, fills up that airport's ground station quickly. But with packet mode, the server in the airplane delivers packets of information as the pipe can handle them. If the channel is full handling packets from another airplane, then as soon as room become available on that channel, more packets can flow. Or packets from one airplane can intermingle with packets from another. The result is an effective increase in bandwidth per aircraft, easily to 9,600 bps and perhaps higher.

In the cabin, passengers will be able to send and receive email and log on to the World Wide Web simultaneously, just as they do with their ground-based networks. The more people on the Web at the same time, the slower each person's downloading. But for email, multiple users probably won't even notice a slowdown. Six to eight passengers should be able to do data at the same time, Smith said, using the transceiver that is wired to the server. This leaves the other transceiver's two voice channels for voice calls. Smith has tested the server on the ground and is ready to install it in the 604s, which are in completion at KC Aviation and due for delivery later this summer. The AT&T packet-mode service should be ready by then, but if not, the airborne network can run off the modem in the server. The server modem is also the backup in case the packet-mode pipe is down.

"The next generation is to get this certified for aviation use so crews can use it for upcoming messages and weather data," Smith said. "The doors that will open up are enormous."



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