rovide. A traditional analog telephone line can support, at most, a 56-kbps data stream, and yet the same copper twisted-pair wire, when not specifi- cally configured for voice, can support a data capacity 24 times higher in the form of a digital subscriber line (DSL). Certain design choices on the PSTN, such as the addition of filters that limit range of frequencies carried by local loops, are actually specifically disadvantageous for data service. The Internet, meanwhile, offers free long-distance Internet telephony, but when it comes to call quality, you get what you pay for. The challenge in growing CDMA systems is to develop and implement standards and designs that provide satisfactory QoS for both voice and data, ideally on the same car- rier. Meeting QoS requirements for voice and data but doing so by using data-only (DO) carriers is not an ideal solution. Using DO carriers alongside voice and data carriers limits the flexible allocation of carriers to meet subscriber demand for either voice or data. 17.1 The Customer Experience of Quality The market for cellular telephones is quickly reaching the point of saturation in North America and Europe. At this point, pretty much everyone who wants cellular service has it, and the market shifts from a phase of rapid growth into a mature phase of com- petition. Wireless service companies will not grow so much by entering new territory first. Instead, they will grow by offering better services to their customers and in- creasing market share by taking it from their competitors. 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. Quality of Service (QoS) Key Data Concepts In the mature competition phase of an industry, customer perception of quality and value is the key to success. However, much of the customer's perception involves things for which the cellular engineer is not primarily responsible.