This paper discusses the improvements that uplink MIMO brings to Mobile WiMAX network deployments and introduces a new technique based on uplink MIMO, tile switched diversity (TSD). Uplink MIMO (UL-MIMO) provides extended coverage (up to 41 percent cell radius increase), and can also be used to reduce power consumption (up to 750 mW power savings) and greatly ease design constraints for high output power CPEs. Maximum performance is obtained when UL-MIMO is implemented both at the mobile station and the base station, but this analysis shows that significant gains can be achieved with UL-MIMO implemented at the mobile station only.

Intel and the WiMAX community may stick to their party line that WiMAX will complement cellular networks rather than challenge them, but the chief 802.16e flagwaver continually highlights areas where it claims its favorite platform can beat HSPA and even LTE hands-down. These are increasingly not directly about technology - given the similarities to LTE, those arguments are now only for teccies - but about the surrounding processes and business models. First there were the claims that royalties would be low or even non-existent in handsets; then that WiMAX would drive down cost per Mbps to a level undreamed-of by mobile operators. Now the focus is on time to market for devices, with Intel claiming the certification process for WiMAX will enable products to get to users in one-third of the time it takes on a 3G network, enhancing ROI, flexibility in service launches, and user satisfaction.

This may sound ironic, given that the chief complaint of early would-be WiMAX  operators, at least beyond the simple access market, is that usable and affordable devices are largely unavailable or delayed. Even in the laptop, expected to be the early driver of WiMAX services uptake in developed economies, there have been delays in certification of chips and dongles, and even Intel pushing out its deadlines for the WiMAX enabled Centrino. As for handsets and media devices, there are very few on the table, even though much of the success of any advanced mobile service launch relies on a good choice of attractive handsets (as the European 3G experience made bitterly clear in the early part of the decade). Currently there is a debate over which is the more concerning for US WiMAX - potential delays in the clearing of the Sprint Xohm/Clearwire venture, or potential non-appearance of fully certified handsets. The likelihood of both hitting their targets seems remote.