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Installing equipment is only part of the cost of a wireless infrastructure because it must be managed, which turns out to be expensive. The centralized management of cellular networks makes this easier because workers can be trained and equipment can be standardized, which is unlike the heterogeneous equipment used with the 802.11 infrastructure where each user decides which vendor's equipment to use. Standard equipment and widespread deployment simplified these management aspects. When managing equipment, the centralized structure of 3G has value.
Spatial Reuse Efficiency
One important difference between the 802.11 and 3G technologies is ownership of spectrum. The spectrum with 802.11 is public and must be shared with other users, while the service provider owns the spectrum with cellular technology. Ownership of spectrum creates value by locking in customers because nobody else can use this spectrum. But, is this lock-in worth the cost of the spectrum? How great a handicap is public spectrum? These important questions remain unanswered.
Spectrum ownership decreases network implementation uncertainty because ownership means control over its use. This uncertainty has two forms. First, there is uncertainty about your neighbor's spectrum use
Coexistence of 802.11 and 3G Cellular: Leaping the Garden Wall 209
because it might interfere with yours, and because you both have the same rights to the spectrum, you can't do much. There are many other uses for this public spectrum, such as X.10 cameras and microwave ovens, with equal rights as 802.11 to use this spectrum. The second type of uncertainty is what type of government regulations might affect your network buildout. The benefits of spectrum ownership are clear, but the value of this ownership is not.
Wireless transmission is hard because many factors interfere with the propagation of signals. The centralized structure of cellular networks fits well with the large-scale planning required to efficiently place the wireless Base Stations. Spectrum is very expensive, which implies that service providers must maximize the number of users in a region. This is possible only with careful positioning of the Base Stations to maximize spatial reuse. Large centralized cellular providers are in an ideal position to design and implement efficient wireless structure because they have the rights to spectrum and typically have some leeway as to where Base Stations are located.
There is a trade-off with 802.11 and cellular services in the context of spectrum versus the management efficiency of the centralized structure. Spectrum can be expensive, but if you own it, you can apply advanced engineering techniques to use it more efficiently (most bandwidth for the most users). Planning how to reuse the limited spectrum most efficiently over large areas is key to affordable cellular services because spectrum is such a limited resource. Spectrum can't be manufactured, so business models demand the most efficient use of this most critical scarce resource. Is this ability to centrally plan and manage your spectrum worth the cost of the spectrum? Even though 802.11 spectrum is also limited, it is free. Are the inefficiencies of managing 802.11 spectrum overcome because this spectrum is free? These are complex questions that will be addressed in future research. This chapter points out the complex relationship between cost of spectrum and management cost of the spectrum — what is the value of free, hard-to-manage spectrum compared to expensive, easy-to-manage spectrum?
The preceding text illustrates the complex trade-offs between 802.11 and 3G. The case for coexistence is strong. Compatibility between 802.11 and 3G is essential to capturing the most value from network services in general and wireless network services in particular. Figure 11.8 is one view of the future world. It demonstrates the ubiquitous nature of current and next-generation cellular technology. The entire region is blanketed with cellular service. This works everyplace, in buildings, subways, and outside the city. It is not the highest speed, but the ubiquitous coverage makes it a valuable technology. There are other spots where the economics determine
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that it makes sense to build a higher-speed, and more expensive 802.11 infrastructure. Locations such as airports, offices, and even homes are examples where this approach works well. Even business parks and dense neighborhoods might be good candidates for 802.11 wireless coverage. There are many places where wired connectivity makes the most sense. My desktop systems at home and in the office fit this category nicely. They never move, and I want the highest bandwidth and security, which the standard Ethernet-switched LAN networks provide. This figure demonstrates that there is room for all three technologies, and all three will coexist and thrive — each service creating value for the other services because of the coexistence of these technologies.