Adaptive Sub-Band Nulling for OFDM-Based Wireless Communication Systems

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Abstract
In this paper, we propose an adaptive sub-band nulling technique in order to improve the performance of orthogonal frequency division multiplexing (OFDM)-based wireless communication systems. It excludes some sub-bands experiencing deep-fading and the transmission power for the excluded sub-bands is reallocated for the remaining sub-bands. We compute the optimal number of nulled sub-bands in order to maximize the capacity. Water-filling is one well-known optimal resource allocation scheme. However, it has tremendous complexity at the transmitter and requires full channel state information from the receiver. We compare the performance of the proposed scheme with that of the water-filling scheme and the result shows that the performance of the proposed scheme is similar to that of the water-filling in a wide range of signal-to-noise ratio (SNR) values. Furthermore, the proposed adaptive sub-band nulling can be used as an enhanced distributed transmission mode in future OFDM-based wireless communication systems after a small modification in the frame structure.