My\u00a0last column\u00a0on technological discontinuities in 2003 generated significant reader e-mail regarding the feasibility of voice becoming the "killer" application for IEEE 802.11 (Wi-Fi). In the past few months, global capital commitments and scheduled deployment into public areas such as hotels, airports, caf\u00e9s, stadiums and truck stops have fueled Wi-Fi growth. This aggressive rollout counters the notion that it will be impossible for Wi-Fi to achieve the ubiquity of cellular wireless. In all probability, cellular mobility will coexist with and complement public and private Wi-Fi deployment until the IEEE solves the distance limitation problems.Wi-Fi's strength - and cellular wireless's weakness - is data. Cellular wireless deployment for data has been hampered by cost and throughput issues that equate to high usage charges. Data will not be the increased call-minute panacea that carriers hoped would pay for licenses and upgrades to\u00a03G\u00a0and other cellular technologies.To make an analogy to the wireline world, at one time the PBX was considered a data switch with connection speeds of 1.2K to 9.6K bit\/sec. The IEEE 802.3 LAN arrived to compete with the PBX and delivered increasingly higher data rates to users. As the technology matured, IEEE 802.3p\/q added quality of service to the LAN and let low-bit-rate real-time voice use the "Ethernet highway." Today, the PBX and LAN coexist, but the PBX faces inevitable retirement. Similarly, in the WAN, data traffic has surpassed voice traffic in carrier networks. Class 5 networks designed to support voice and disastrously redesigned to support data using ISDN are now pass\u00e9. Coexistence is still the case, but voice over IP will be the eventual victor. The data highway always will be the winner when compared with the voice highway.Technological history has a way of repeating itself. What occurred in the wireline arena will replicate itself in the wireless arena. Wireless technologies such as cellular, IEEE 802.11, IEEE 802.15 and IEEE 802.16 will coexist for a time. Cellular was designed for voice, the other three for data. How long they coexist will be, as in the wireline space, an economic, rather than a technological, issue.One reader commented on the limitations of Wi-Fi with respect to the number of users that can be serviced per base-station access points and the allocation of finite resources per user. At least four approaches have emerged to address this problem. The first uses high-capacity, longer-range Wi-Fi switch\/access points to transmit narrow beams of packets only to designated wireless devices. The second uses distributed dumb Wi-Fi access points and a new generation of intelligent Ethernet switch that centrally aggregates and controls multiple access points. The third creates a multiple smart-antenna access point that can aggregate hundreds or thousands of users. The fourth uses an intelligent base-station switch to aggregate and control distributed smart antennas. My bet is that the second approach will win out because of cost, ease of implementation and management.Many readers discussed security for the user and the economics of the business case for the public Wi-Fi hot spot. Security is being addressed in the transmission layer of Wi-Fi with IEEE 802.11i and at the IP applications layer with standards- and policy-based authentication and access control. Economics are another matter.The issue today with public hot spots is that flat-fee charges do not return enough revenue to pay for the cost of WAN Internet access facilities, let alone voice charges. The most advantageous approach seems to be to treat the Wi-Fi equipment and WAN access as a sales expense, embedding that overhead cost across all goods and services. The only other alternative will be on-demand or multilocation\/vendor flat-fee billing at an equitable rate structure to stimulate use and recover cost.The success of Wi-Fi is analogous to the success of the cellular industry. Technology was secondary to simplifying universal roaming and creating a sound demand-based economic and business model. The wheel turns; cellular today, Wi-Fi tomorrow.