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Increasing demand for high-performance 4G broadband wireless is enabled by the use of multiple antennas at both transmitter and receiver ends. Multiple antenna technologies enable high capacities suited for Internet and multimedia services, and also dramatically increase range and reliability. The combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the data rates of next-generation wireless communication systems operating in frequencyselective fading environments. In this paper ,we focus mainly on Internet users in hotspots like Airport etc., requiring high data rate services. A high data rate WLAN system design is proposed using MIMO-OFDM. In the proposed WLAN system, IEEE 802.11a standard design is adopted but the results prove a data rate enhancement from the conventional IEEE 802.11a.

As the demand for broadband multimedia wireless services increases, the need to provide QoS and higher data rate enhancements to the widely deployed IEEE 802.11 wireless LAN has become apparent. However, currently deployed IEEE 802.11 standards have little or no QOS support functions built in to the MAC layer. The IEEE 802.11e EDCF mechanism is currently being developed to provide QoS functions in the MAC layer based on service differentiation and traffic class prioritization. Along with the 802.11e QoS amendment, 802.11n defines advanced ARQ policies designed to increase the channel utilization efficiency by reducing MAC protocol overhead. Although these techniques provide vast improvements over the legacy 802.11 protocol, opportunities exist with in this framework to optimize performance based on the type of traffic being serviced. In this paper a distributed medium access scheme called EDCF, which is adopted in an upcoming standard IEEE 802.11e to allow prioritized medium access for applications with QoS requirements is analyzed and its performance is evaluated using OPNET Modeler. We also investigate the performance optimization of the 802.11 Block Ack ARQ policy, and discuss adaptive block size algorithm for throughput improvement.

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