Sprint's Mobile WiMAX Network

Sprint ( Sprint Nextel Corporation is the third largest cellular operator in USA, with 53.7 million subscribers) is engaged in design and deployment of Mobile WiMAX broadband network in full-swing. The Chicago and Washington D.C. areas have been chosen as initial WiMAX service areas with additional markets to be identified based on market-readiness estimates.The first market may be launched by the end of the year and they plan to reach at least 100 million people by year-end 2008.
Sprint's WiMax network is based on the IEEE 802.16e-2005 standard,operates in the 2.5GHz band and is also termed as 4G network.
The core 802.16e s contains three different air interfaces: single carrier, OFDM ( Orthogonal Frequency Division Multiplexing)and OFDMA (Orthogonal Frequency Domain Multiple Access). Single carrier systems are targeted at the 10-66 GHz band, point-to-point for backhaul. OFDM (more commonly referred to as 802.16d) is the first WiMAX standard, intended for fixed broadband wireless access.
The standard 802.16e-2005 used by Sprint, brings an enhanced air interface using OFDMA with enhanced performance and optimized to support mobility. It also adds support for advanced features such as MIMO ( Multiple-Input, Multiple-Output)and AAS (Advanced Antenna Systems) further improving the rate/reach of WiMAX technology in deployment.
OFDM works by dividing a given spectrum block into a number of sub-channels, each of which is individually modulated and then transmitted orthogonally to minimize interference with one another. The result is faster, more robust radio links than can be achieved with alternative modulation/multiplexing schemes. It is often claimed, for example, that OFDM is more efficient, in terms of bits per Hertz, than CDMA and WCDMA (wideband code division multiple access) technology used in 3G systems, and/or delivers better performance in non-line-of-sight urban environments due to better resistance to multipath interference.
OFDMA air interface has an added feature of multiple access duplexing in the time domain achieved by assigning ‘slots’ or ‘tiles’ on a dynamic per user basis. This scheme provides and efficient use of available spectrum allowing bandwidth (and ultimately usable data rate) sharing across users.WiMax is be the integration into existing 3GPP core networks.
MIMO technology allows for either enhanced datarate, or enhanced coverage or reach. MIMO systems have several antennas allowing many, distinct signals to be simultaneously sent at the same time. WiMAX supports several different MIMO techniques such as Matrix A ‘Alamouti’ for improved reach/indoor coverage and Matrix B ‘Blast’ for enhanced datarates.
The technique AAS also called beamforming, improves the spectral efficiency (bits/s/Hz) of the OFDMA air interface which can dramatically reduce the cost of deployments (Capex) and the typical throughput to the user. Multiple antennas give the ability to steer the beam from the base station to the user improves reach, and the ability to steer nulls reduces interference.

Sprint WiMax network will will offer downstream speeds of 2Mbps to 4Mbps and combined with fast uplinks, it will offer enough bandwidth for mobile videoconferencing, transfers of large enterprise files and other applications.At the current levels UMTS can not offer anything comparable at this stage but UMTS is already established itself and WiMax has still to prove itself as a viable cellular network in marketplace.