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Nikhil Gulati

Publications and source records attributed to Nikhil Gulati.

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Learning Sequential Channel Selection for Interference Alignment using Reconfigurable Antennas

In recent years, machine learning techniques have been explored to support, enhance or augment wireless systems especially at the physical layer of the protocol stack. Traditional ML based approach or optimization is often not suitable due to algorithmic complexity, reliance on existing training data and/or due to distributed setting. In this paper, we formulate a reconfigurable antenna based channel selection problem for interference alignment in a multi-user wireless network as a learning problem. More specifically, we propose that by using sequential learning, an effective channel or combination of channels can be selected in order to enhance interference alignment using reconfigurable antennas. We first formulate the channel selection as a multi-armed problem that aims to optimize the sum rate of the network. We show that by using an adaptive sequential learning policy, each node in the network can learn to select optimal channels without requiring full and instantaneous CSI for all the available antenna states. We conduct performance analysis of our technique for a MIMO interference channel using a conventional IA scheme and quantify the benefits of pattern diversity and learning channel selection.

eess.SP

Experimental Evaluation of a Reconfigurable Antenna System for Blind Interference Alignment

In recent years, several experimental studies have come out to validate the theoretical findings of interference alignment (IA), but only a handful of studies have focused on blind interference alignment. Unlike IA and other interference mitigation techniques, blind IA does not require channel state information at the transmitter (CSIT). The key insight is that the transmitter uses the knowledge of channel coherence intervals and receivers utilize reconfigurable antennas to create channel fluctuations exploited by the transmitter. In this work, we present a novel experimental evaluation of a reconfigurable antenna system for achieving blind IA. We present a blind IA technique based on reconfigurable antennas for a 2-user multipleinput single-output (MISO) broadcast channel implemented on a software defined radio platform where each of the receivers is equipped with a reconfigurable antenna. We further compare this blind IA implementation with traditional TDMA scheme for benchmarking purposes. We show that the achievable rates for blind IA can be realized in practice using measured channels under practical channel conditions. Additionally, the average error vector magnitude and bit error rate (BER) performances are evaluated.

cs.IT