We may also have problems with capacity as lots of users attempt to access the relatively limited number of channels available. The solution here is simple in one respect -- just add more base stations. Cellular carriers have to deal with this problem on a daily basis, but, again, the expense involved is one of the reasons that cellular systems still feature dropped calls, occasional gaps in service and (often) slow data throughput.

In fact, comparisons with cellular are quite appropriate here, since the challenges faced by cellular and mobile WiMax are almost identical. And therein lies the biggest challenge -- can mobile WiMax really compete with cellular? Cellular-based wireless broadband services like 1xEV-DO, available from Sprint and Verizon, and HSDPA (High-Speed Downlink Packet Access), available from Cingular, will eventually offer multimegabit data services -- exactly the territory mobile WiMax is targeting. While it's been theorized that the cost of mobile WiMax base stations will be less than that of corresponding cellular equipment, the real costs in operating any wireless network are in spectrum (it's auctioned to the highest bidder), real estate and customer-related functions like marketing, sales and support. WiMax won't have any advantage in these.

Many people have been thinking of WiMax as "Wi-Fi on steroids," and even that WiMax w

ill replace Wi-Fi over time. Both of these suggestions are outside the bounds of reality. Wi-Fi is a wireless LAN and well on its way to ubiquity. Nothing can stop Wi-Fi, and it will challenge WiMax in metro-scale applications.

More importantly, however, Wi-Fi is a "small cell" technology with a range of perhaps a couple of hundred meters under the right circumstances. WiMax is a "big cell" approach, designed to cover kilometers. As it turns out, the combination of big and small is likely the best solution to the coverage and capacity problem. But I don't think the combination of WiMax and Wi-Fi is likely to prevail; cellular is well established in the big-cell space, and WiMax will have a difficult time indeed penetrating that opportunity.