ion from cable and wireless companies represents a threat to wireline service providers on several fronts. First, cable modems enjoy a significant amount of press and, therefore, are gaining well-deserved market share; in fact, more than 65 percent of the broadband installed base today is delivered via cable modems, not via DSL. The service they provide, for the most part, is well received and offers high-quality, high- speed access. Wireless, on the other hand, is a slumbering beast. It has largely been ignored as a serious competitor for data transport, but the wild success of Wi-Fi, EV-DO, and CDMA-1x solutions have pushed wire- less into the limelight. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Chapter 6 The second challenge is unmet customer demand. If DSL is to satisfy the broadband access requirements of the marketplace, it must be made available throughout ILEC service areas. This means that incum- bent providers must equip their central offices with DSLAMs that will provide the line-side redirect required at the initial stage of DSL deploy- ment. The law of primacy is evident here: The ILECs must get to market first with broadband offerings if they are to achieve and keep a place in the burgeoning broadband access marketplace. The third and fourth challenges to rapid and ubiquitous DSL deploy- ment are installation issues and plant quality. A significant number of impairments have proven to be rather vexing for would-be deployers of widespread DSL. These challenges fall into two categories: electrical dis- turbances and physical impairments. While solutions have been crafted for most of these, they still pop up occasionally as vexing problems. Electrical Disturbances The primary cause of electrical disturbance in DSL is crosstalk, caused when the electrical energy carried on one pair of wires "bleeds" over t