By: John Michael Pierobon
Are you thinking of upgrading to a faster modem?
I am. I am a cautious buyer who likes to carefully evaluate technology before jumping into it. After all, as an Internet consultant, I get paid to evaluate new products and new techologies for my clients. Sometimes taking a wait and see attitude towards new technologies pays off, as in the case of video cassette recorderes. BetaMax came out first, but VHS became the de facto standard.
Early last year USRobotics, the world's largest modem manufacturer, came out with their 56 Kbps modem, the X2, and they pattened/copyrighted their protocol so others could not copy/use it. So K56Flex was used by everybody else. K56Flex is a better protocol, but do not rush to buy a K56Flex modem, for it may soon be obsolete.
In February, the International Telecommunication Union (ITU) publised a 60-page draft standard, that should be ratified this month (September 1998). This new standard, known as V.90, is well thought out, and should in theory lead to interoperability between modems. This theory will soon be put into practice as modem vendors release new modems with V.90 firmware.
The limiting factor in the speed of data transmission is the inherent noise in analog telephone lines. Digital lines also have noise, but not as much. Too much noise on the line will cause your modem to disconnect.
Speed of data transmission and reliablity of data transmission are inversly porportional. Reliability suffers with higher speeds, causing modems to disconnect and forcing you to reconnect to resume data transfer. While you may have a high connection speed (baud rate) throughput (the time it takes for you to completely receive a batch of data) may actually be lower because you have to reconnect.
Modems running over analog lines have a theoretical upper limit of 33.6 Kbps for bi-directional data transfer. While these high baud rates can occasionally be achieved, in the real world a baud rate of about 21.6 Kbps seems to provide the best throughput. Several factors affect the reliability and speed of a modem connection over analog lines. They include: distance from the telephone company's Central Office, the type of phone switch(es) installed in the Central Office, age and quality of the copper wires from the Central Office to your home, and noise induced into your home or business telephone system by external sources such as high tension power lines.
To overcome these limitations, modem manufactures have created modems that transfer data in an aysymetric manner, meaning that modems upload data at 19.2 Kbps, but download the data at speeds approaching 56 Kbps. These modems can only achieve these types of speeds when their connection is made over digital telephone lines and to a compatable modem on the other end of that digital line.
V.90 employs one bidreictional channel for sending and receiving data. The receiving portion of the V.90 analog modem's channel is capable of higher speeds because no information is lost in the digital-to-analog conversion. In essence, V.90 isolates the analog component so it does not affect the transmission of data, and thus V.90 lets modems receive data at up to 56 Kbps even over analog lines, as long as their is a digital connection at one end. Most Internet Service Providers (ISP) now have a digital connection at their end.
Soon, after the bugs are worked out, the world will be totally V.90 compliant, but in the meantime ask your ISP if they are V.90 compliant, and find out if your new modem is also V.90 compliant.