Amrit Singh Bedi

BER-Optimized Precoders for OFDM Systems With Insufficient Cyclic Prefix

This letter considers precoder design for orthogonal frequency division multiplexing (OFDM) systems with insufficient cyclic prefix (CP). Interference alignment is utilized to formulate the precoder design problem as a bit error rate (BER) minimization problem subject to a total power constraint. Subsequently, a novel closed-form solution is derived for the optimal precoder by exploiting Schur convexity and interference alignment-based interblock interference (IBI) suppression. The resulting precoder is also shown to be mean-square-error (MSE) optimal, and generalizes the existing designs. Closed-form expressions are also developed for quantifying the signal-to-noise ratio (SNR) gain of the proposed design over existing designs for practical channels with a decaying power-delay profile. Simulation results corroborate the performance improvements over existing MSE optimal designs considering the availability of both full and partial channel state information at the transmitter (CSIT) for various power delay profiles.

Optimal utilization of storage systems under real-time pricing

This paper considers the problem of optimal battery usage under real-time pricing scenarios. The problem is formulated as a finite-horizon optimization problem, and solved via an incremental algorithm that is provably optimal in the long run. The proposed approach gives rise to a class of algorithms that utilize the battery state-of-charge to make usage decisions in real-time. The proposed algorithm is simple to implement, easy to modify for a variety use cases, and outperform the state-of-the-art technique such as Markov Decision Process (MDP) based. The robustness and flexibility of the proposed algorithm is tested extensively via numerical studies.

Asynchronous resource allocation in distributed heterogeneous networks

Stochastic network optimization problems entail finding resource allocation policies that are optimum on an average but must be designed in an online fashion. Such problems are ubiquitous in communication networks, where resources such as energy and bandwidth are divided among nodes to satisfy certain long-term objectives. This paper proposes an asynchronous incremental dual decent resource allocation algorithm that utilizes delayed stochastic gradients for carrying out its updates. It is shown that with constant step size, the proposed resource allocation policy is asymptotically near-optimal. An application involving multi-cell coordinated beamforming is detailed, demonstrating the usefulness of the proposed algorithm.

BER-Optimized Robust Precoder Design for MIMO-OFDM Systems with Insufficient CP

This paper considers a robust precoder design for MIMO-OFDM systems with insufficient cyclic prefix (CP). Interference alignment is utilized to formulate the precoder design problem as a bit error rate (BER) minimization problem subject to a total power constraint. To this end, the precoder is designed to be robust to the errors in the available channel estimates, by considering the worst-case BER for optimization. Interestingly, channel estimates at both transmitter and receiver are allowed to be in error. Extensive simulations are carried out to compare the performance of various MIMO-OFDM systems with and without robust precoders.