A little update on Hayai Lite: we're seriously considering a change in technology (yay for last-minute changes).
Even though we have access to a WiMax network in Mumbai, we're now thinking that we should use 2.4GHz WiFi (802.11n) with high-gain antennas so that users can have internet access without a CPE, but it's also due (in part) to some manufacturers scaling back their WiMax equipment offerings.
For subscribers who don't have WiFi (or if the signal is weak), we can provide an a CPE with an outdoor antenna to be attached to the window cage to give a better signal, and although using WiFi instead of WiMax will mean that we will have to install more APs (in some cases, one AP for each apartment building plus repeaters as necessary), we think that the combination of technology and increase density of APs will give us better coverage, reliability & speed than what we were working on with WiMax. 802.11g/n also offers faster speeds.
The reason for this new consideration is because in NZ we're using 5GHz WiFi (802.11n) due to 2.4GHz being widely used in NZ and the limited availability of WiMax equipment. The advantage to this is that we don't have any interference, the disadvantage is that because most WiFi cards don't support 5GHz by default, this requires everyone to have a CPE on their roof (which contributes about Rs300/month to the fee). The good news is that so far the tests are giving us speeds in excess of what the wired line actually handles, even at distances of 2.2km.
Authentication & security in both cases would be taken care of by WPA2-Enterprise (when you connect to the wifi, you enter a username & password, such as user@lite.hayai.net.in).
Did you look at 802.16m(also called wimax 2).
Samsung demostrated 330Mbps speeds.