Study of Issues Related to Adaptive Channel Estimation in OFDM System-MWBA Aspects

Mobile Wireless Broadband Access (MWBA) in latest WiMax versions (IEEE 802.16e onwards) has critical requirement of vehicular mobility. OFDM is a wideband multicarrier digital modulation scheme, very much suitable for applications like WiMax because of its features such as ISI elimination and high speed support due to parallel transmissions. Now, complexity in the WiMax system is because of fast varying channel due to vehicular mobility and frequency selective channel due to wideband transmission. At the same time for the portable battery operated device, power consumption should be less i.e signal processing must be minimum and fast and it should support higher bit rate. Always the tradeoff exists in any of the selection. In addition to this, while using modulation mapping schemes like QAM, channel effects are more critical and estimation at the receiver becomes compulsory. Channel estimation related issues become very important in this scenario, because FFT and Adaptive channel estimation stages mostly consumes the power due to heavy processing burden. Different issues related to channel estimation methods are studied in this paper and efforts are made to find out the optimum solutions for best BER performance. Few innovative ideas are also suggested.