Comm Corner - August, 1997

Comm Corner
56 kbps Modem Followup
What Other Writers are Saying
by John Woody

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This month, we will follow-up on the 56 Kbps analog modem venture. This article is for those of us who may have been on Mars in the last six months. If you didn't know it, there is a battle for our hearts and money going on between US Robotics and the rest of the modem industry concerning whose standard (protocol) will be accepted as the industry standard for data transmission at 56,000 bits per second (bps).

As those of you who were here and not on Mars remember, the industry heavies are using the market place to gain acceptance of which version of the 56 Kbps protocol will become the standard. There are two versions of the protocol being pushed, one version by USR (x2) and the other by the other heavies, Rockwell/Lucent (56 Flex). Only four manufacturers make the communication chip sets for all of the modems in the world. USR makes it's own. Rockwell, Lucent, and Motorola each make the remainder, with Motorola using some version of the other three sets.

From the May article, we learned that

the two protocols are incompatible with one another
that only about twenty-five percent of the telephone lines in the U. S. Will handle 56 Kbps data transfer
that the phone companies are restricted by the Federal Communications Commission (FCC) to 53 Kbps on signal strength.

In light of all these caveats, it would seem that we are being fleeced of our money to some extent in the heat of the marketing battle. USR even has a phone line test procedure at their facility so that you can test your line connection for x2 compatibility. We tested the line at Central Park Mall which passed with flying colors, leading the Power SIG group to believe that the USR test may be a marketing gimmick. Earlier, during the SIG we had all sorts of problems just trying to connect at 28.8 Kbps.

We also learned that the national and international bodies who have the responsibility for settling the standard will not have their review work completed for at least a year in the case of the U. S. Group, Telecommunications Industry Association (TIA); and, in two years in the case of the international group, International Telecommunications Union (ITU).

USR was first to release its remote server program in order for Internet Service Providers (ISP) to be able to handle their end of the transmission. Remember, modem basics, the two modems must be able to speak the same language. This brings us to the first of the incompatibilities we discovered in May, i.e., the protocols are incompatible. The ISP must set up a special connection in order to be able to handle the x2 or 56flex protocol at any speed. The 56flex remote server has just been released and is now in place at some ISPs.

Both protocols take advantage of the fact that the telecommunications infrastructure (phone system) is now primarily a digital network. The phone system is no longer limited by analog phone lines and their 35 Kbps transfer speed limitations. Let me try to explain what has taken place from the analog to digital phone network.

In a V.32 or V.34 modem connection over an analog line, the two modems perform digital-to-analog and analog-to-digital data conversions as the signals move between the two PCS over the Public Switched Telephone Network (PSTN). This conversion alters the signal, creating a reconstructed or corrupted signal different from the original. This difference is called quantization noise and limits transfer rates to 35 Kbps. Quantization noise only takes place during analog-to-digital conversion. When the conversion noise is eliminated, the transfer speed can increase.

The PSTN is primarily digital, the only exception being the local service loop from the user's connection to the central office (CO). Both x2 and 56flex assume that this is the only analog segment to handle, the upstream connection, which is limited to the V.32 or V.34 analog transfer speed. The downstream connection or download is digital and theoretically can be at 56 Kbps, of course except for the FCC rule of 53 Kbps, and all those other exceptions.

Testing by various individuals and laboratories are confirming the limitations. One truth being confirmed is that the closer you are to the phone company CO, the better your chances of making a connection close to the 53 Kbps speed.

I think this is really a truth in all analog modem connections in that I have the V.34bis (33.6 Kbps protocol) installed in my USR Courier and I hardly ever get a connection above 28.8 Kbps. Once in a while, I get 33.4 Kbps, but I do get a solid 28.8 Kbps connection nearly every time. My connection to the SW Bell CO goes through at least one local switch, Wetmore, before it gets to the CO. I feel this is the primary reason for my non-33.6 Kbps capability

What Other Writers are Saying

Bill Machrone, in PC Week stated after informal testing in his home and others on his block, "At a friend's home, I got connections between 44 Kbps and 48 Kbps on both his lines. His property abuts Bell Laboratories, and the central office (CO) is just down the street. If he doesn't have good phone lines, nobody does." He further states, "My analog lines only managed 22 Kbps and 24 Kbps connections, and the diagnostics showed heavy attenuation at the higher end of the frequency spectrum". He further tested other lines on his block and found they were like his or worse.

Michael Caton of PC Week's laboratories stated, "In initial tests of 56 Kbps modems, PC Week Labs had difficulty connecting at the advertised throughput rate. In further tests, we managed to connect at these higher rates using modems from U. S. Robotics Corp., but we aren't changing our original recommendation: Make sure these modems will work from a given location before buying".

Businesses who want these higher speeds may have to invest in like hardware for each end of the connection to gain the higher speeds. The modems will require a special switch at the point of service, i.e., the ISP, in order to connect close to 56 Kbps. Dialing another modem, even another 56 Kbps modem will probably not give speeds above V.34 (28.8 Kbps). USR has such a switch called the Total Control Net-Server/8 I-modem. A business desiring that it's remote access be at this higher rate would have to install one of these switches.

An employee attempting to call into the switch still may not achieve the 56 Kbps level transfer rates due to other intervening factors such as the motel PBX phone system. PBX's add conversion (analog-to-digital) which slows down to the transmission.

USR has set up a test site for individuals to test their phone line against to determine if the line will carry the 56 Kbps rates. The service includes "A try-before-you-buy-line testing utility that enables prospective x2 purchasers to evaluate the condition of their copper phone line." Here is how the test is conducted.

What is needed in the USR Test:

There are two requirements:

Any manufacturer's V.34 modem, installed and connected to a phone line
Any terminal communication application (such as Win95's HyperTerminal, RapidComm tm, Quicklink II or MacComCenter)

Open the communications application's terminal window, following that application's instructions.

Dial this number: 1-888-877-9248

Use the terminal dialing procedure; or, type ATDT18888779248 in the terminal screen.

You will be connected to the LineTest system, and asked if your system supports graphics. Press the <Enter> key to proceed. You will then be prompted for your name.

Type in: <Line Test> The test system will then perform a series of diagnostics on your connection, and will inform you of its conclusion. The first statement is one which tells you if your connection works at 56 Kbps. There is a <More> which gives good statistics on your connection.

Remember that this test is by U. S. Robotics, who has a great stake in selling 56 Kbps x2 modems.

The Analog/Digital Future

There are exciting things in the near future for high speed modems. As the telephone companies add more Digital Subscriber Line technology, the really rapid communication speeds will take place, i.e., as we lose the local loop analog connection in favor of all digital connection loops, we will see much faster speeds. Just around the time/year corner is the use of these modems in combination with Asymmetric Digital Subscriber Line (ASDL) connections.

Remote access routers which combine the data-carrying capacity of multiple analog modems are being introduced by USR and Ramp Networks. These access routers, which can be used as stand-alone remote PCS or as connections to local area networks (LAN) combine two or more analog modems based on the 56 Kbps technology which can be combined or used separately. The USR product is LANLinker Dual Analog Router and the Ramp Networks product is WebRamp M3. The WebRamp M3 has three 56 Kbps modems in the same router.

The LANLinker router contains two analog channels of 56 Kbps each which can be used separately or in combination giving up to 116 Kbps transmission speed. This bandwidth is close to Integrated Digital Network (ISDN) capabilities of 64 Kbps per B channel and combinations of 128 Kbps, and the analog channels are from regular low-speed telephone lines without the ISDN cost tariff. Two analog channels would be like ISDN in that data could be moved on one channel while talking on the other channel. The multiple analog routers do require multiple analog phone lines.

Conclusion

Again, my advice is to wait for the standards war to be completed before making any permanent move to 56 Kbps analog service. If you just must have a "need for speed", then get a written assurance from the modem manufacturer that the final standard (protocol) for 56 Kbps service will be upgradable when it is set.

Also, talk to your ISP and make sure that they handle the other end of the connection.

JOHN WOODY IS A TELECOMMUNICATIONS CONSULTANT SPECIALIZING IN SMALL BUSINESS COMMUNICATION, NETWORKS, AND INTERNET BUSINESS TRAINING.