The Latest Advances In Modem Technologies By Christopher Smith   As the popularity of mobile computing steadily grows, so do the needs of the mobile user. One of the most urgent needs to satisfy is the quickly changing requirements for modems used for accessing resources in a variety of settings. The ability to "hook up" from anywhere and obtain the fastest throughput possible also guarantees the highest possible utilization of those resources. In this Buyer's Guide, we'll look at how modem vendors are working to develop features for mobile connectivity and enhanced throughput, as well as how the PC Card industry is changing with the introduction of 56-Kbps technology (and how you can prepare for it). The International Te lecommunication Union Telecommunication Standardization Sector (ITU-T) recently approved a revision to the 28.8-Kbps standard, V.34. This revision will result in the top speed of data c ommunications equipment (DCE) jumping to a maximum of 33.6 Kbps. How does this affect you if you can't even hit 28.8 Kbps? Provisions have been made to the V.34 chipset standard to drive overall connection rates higher, though you may not always hit the higher rates. The more important issue here is not simply the new faster high-end speeds, but the ability to obtain consistently higher connection rates. Most manufacturers claim that you will see a 2,400- to 4,800-bps faster connection rate than was seen in the original V.34 standard, but only when connecting two modems that are both compliant with the most recent standard. The revision of the V.34 standard was first suggested by Rockwell Semiconductor Systems as V.34+, but that proposal to the ITU was later withdrawn. Before the final draft of the new extensions, vendor s used other names like V.34 Plus and Extended Rate V.34 to describe the additions. In the end, the ITU decided to keep the original moniker. As confusing as it is, it only gets worse--the new V.34 standard is also used as half of the equation of the 56-Kbps technology that's beginning to arrive on the market and it lacks its own ubiquitous standard. With different chipset vendors touting their 56-Kbps technology, you may find yourself wondering how you can get 56-Kbps transmissions. Because the 56-Kbps market is still burgeoning, industry standards have yet to be implemented. However, a final standard seems to be only a few years away, thanks to the development of 56-Kbps chipsets by Lucent Technologies, Rockwell Semiconductor Systems and U.S. Robotics. Chipping Away at the Equation Two modems may conform to the same standards, but contain chipsets implemented differently by the vendor. This can affect the modem's performance. For your purchase, you should consider two chips within the modem: the firmware controller and the digital signal processor (DSP). The DSP is the main chip, and it performs the actual modulation and demodulation of the signal that travels through the telep hone system. Approximately 70 percent of modem manufacturers buy DSPs from Rockwell. The firmware controller is the chip that controls the DSP. Of the manufacturers that use Rockwell chipsets, some write their own firmware controller code, and others purchase the code directly from Rockwell. We've found that manufacturers that write their own code rather than purchase it from Rockwell have much higher transfer rates, fewer dropped calls and better compression (see "Good Things Come in Small Packages: Combo PC Cards," April 1, 1996, page 108, or techweb.cmp.com/nc/705/705rev1.html). Today, most modems' controller firmware can be upgraded easily since the firmware resides in Flash memory. U.S. Robotics has differentiated itself from other modem manufacturers by producing a flash-upgradable DSP, as well as the firmware controller. This gives U.S. Robotics a slight edge in the nascent 56-Kbps market by guaranteeing its customers free upgrades to the 56-Kbps standard when it's finally settled. Vendors also are looking to enhance connectivity through methods other than traditional standards. Microcom has developed a desktop modem technology, Advanced Parallel Technology (APT). The company found that by using the parallel port instead of the serial port to send data, it can achieve a higher transfer rate. To download an Adobe Acrobat .pdf format version of the V.34 & 56-Kbps Modem Buyer's Guide charts, click here.

Adapting To Your Environment Updated Ju ne 27, 1997