FAST LINK ADAPTATION TECHNIQUE FOR TIME VARYING MULTIPATH CHANNELS

Abstract

Multicarrier communication systems with adaptive modulation and coding systems such as OFDM are well suited for high speed and mobility oriented networks like mobile WiMAX, that has to support users in different fading and mobility conditions. It is also important in practical wireless systems for improving the accuracy of the link adaptation and the efficiency of radio-resource-management. Bit Error Rate (BER) prediction over fast varying channel has emerged as an active research area. Exponential Effective SINR Mapping (EESM) is a mapping scheme that facilitates system level simulations by accounting the system performance in multi state channel in terms of an Additive White Gaussian Noise (AWGN) Channel. The method comprises of the steps of providing individual channel quality values for the different channels and determining a quality measure indicative of the link quality by averaging the individual channel quality values in exponential domain. The BER of the system in that multi state channel thus gives an insight of the modulation and coding schemes to be used for the given link. The simulation results are discussed for different channel realizations, different modulation and coding schemes. This method can be extended to handle more advanced link enhancement such as Alamouti coding and the resulting scheme would be Alamouti based EESM scheme