Wi-Fi: 802.11 may be not the best way for last mile connection. The use of 802.11-based hardware for metropolitan-sized networks decreases costs, but 802.11 has performance limitations when supporting larger numbers of users needing guaranteed bandwidth. In addition, RF interference is often a significant problem with 802.11 when covering large areas due to license free operation. A competitor may install an 802.11 network which interferes with yours, and users will suffer due to sporadic, poor performance. There's really nothing you can do about that because there are no legal grounds to remedy the situation. I summary it as follows: 802.11 is a free frequency, it is not controled by govenment and orgination. As we get the free service, we have to endure all the private activities. We need a method to make users of 802.11 keep friendly with each other. Maybe cognitive network is a good start.
WiMAX: 802.16 is on its way. 802.16 supports point-to-multipoint architecture in the 10-66 GHz range, transmitting at data rates up to 120Mbps. At those frequencies, transmission requires line-of-site, and roofs of buildings provide the best mounting locations for base and subscriber stations. The base station connects to a wired backbone and can transmit wirelessly up to 30 miles to a large number of stationary subscriber stations, possibly hundreds.
To accommodate non-line-of-site access over lower frequencies, IEEE published 802.16a in January 2003, which includes support for mesh architecture. 802.16a operates in the licensed and unlicensed frequencies between 2GHz and 11GHz using orthogonal frequency division multiplexing (OFDM), which is similar to 802.11a and 802.11g.
The 802.16 medium access control (MAC) layer (define) supports many different physical layer specifications, both licensed and unlicensed. Through the 802.16 MAC, every base station dynamically distributes uplink and downlink bandwidth to subscriber stations using time-division multiple access (TDMA). This is a dramatic difference from the 802.11 MAC, with current implementations operating through the use of carrier sensing mechanisms that don't provide effective bandwidth control over the radio link.