arXiv subjects

S. J. Darak

Publications and source records attributed to S. J. Darak.

7 recordsLinked to original sources

arXiv2021

Resource Constrained Neural Networks for 5G Direction-of-Arrival Estimation in Micro-controllers

With the introduction of shared spectrum sensing and beam-forming based multi-antenna transceivers, 5G networks demand spectrum sensing to identify opportunities in time, frequency, and spatial domains. Narrow beam-forming makes it difficult to have spatial sensing (direction-of-arrival, DoA, estimation) in a centralized manner, and with the evolution of paradigms such as artificial intelligence of Things (AIOT), ultra-reliable low latency communication (URLLC) services and distributed networks, intelligence for edge devices (Edge-AI) is highly desirable. It helps to reduce the data-communication overhead compared to cloud-AI-centric networks and is more secure and free from scalability limitations. However, achieving desired functional accuracy is a challenge on edge devices such as microcontroller units (MCU) due to area, memory, and power constraints. In this work, we propose low complexity neural network-based algorithm for accurate DoA estimation and its efficient mapping on the off-the-self MCUs. An ad-hoc graphical-user interface (GUI) is developed to configure the STM32 NUCLEO-H743ZI2 MCU with the proposed algorithm and to validate its functionality. The performance of the proposed algorithm is analyzed for different signal-to-noise ratios (SNR), word-length, the number of antennas, and DoA resolution. In-depth experimental results show that it outperforms the conventional statistical spatial sensing approach.

eess.SP↗

arXiv2021

Reconfigurable Architecture for Spatial Sensing in Wideband Radio Front-End

The deployment of cellular spectrum in licensed, shared and unlicensed spectrum demands wideband sensing over non-contiguous sub-6 GHz spectrum. To improve the spectrum and energy efficiency, beamforming and massive multi-antenna systems are being explored which demand spatial sensing i.e. blind identification of vacant frequency bands and direction-of-arrival (DoA) of the occupied bands. We propose a reconfigurable architecture to perform spatial sensing of multi-band spectrum digitized via wideband radio front-end comprising of the sparse antenna array (SAA) and Sub-Nyquist Sampling (SNS). The proposed architecture comprises SAA pre-processing and algorithms to perform spatial sensing directly on SNS samples. The proposed architecture is realized on Zynq System on Chip (SoC), consisting of the ARM processor and FPGA, via hardware-software co-design (HSCD). Using the dynamic partial reconfiguration (DPR), on-the-fly switching between algorithms depending on the number of active signals in the sensed spectrum is enabled. The functionality, resource utilization, and execution time of the proposed architecture are analyzed for various HSCD configurations, word-length, number of digitized samples, signal-to-noise ratio (SNR), and antenna array (sparse/non-sparse).

eess.SP↗

arXiv2021

Design and Implementation of Low Complexity Reconfigurable Filtered-OFDM based LDACS

L-band Digital Aeronautical Communication System (LDACS) aims to exploit vacant spectrum in L-band via spectrum sharing, and orthogonal frequency division multiplexing (OFDM) is the currently accepted LDACS waveform. Recently, various works dealing with improving the spectrum utilization of LDACS via filtering/windowing are being explored. In this direction, we propose an improved and low complexity reconfigurable filtered OFDM (LRef-OFDM) based LDACS using novel interpolation and masking based multi-stage digital filter. The proposed filter is designed to meet the stringent non-uniform spectral attenuation requirements of LDACS standard. It offers significantly lower complexity as well as higher transmission bandwidth than state-of-the-art approaches. We also integrate the proposed filter in our end-to-end LDACS testbed realized using Zynq System on Chip and analyze the performance in the presence of $L$-band legacy user interference as well as LDACS specific wireless channels. Via extensive experimental results, we demonstrate the superiority of the proposed LRef-OFDM over OFDM and Filtered-OFDM based LDACS in terms of power spectral density, bit error rate, implementation complexity, and group delay parameters.

eess.SP↗

arXiv2020

Spectral Coexistence of LDACS and DME: Analysis via Hardware Software Co-Design in Presence of Real Channels and RF Impairments

To meet the exponentially increasing air traffic, L-band (960-1164 MHz) digital aeronautical communication system (LDACS) has been introduced. The LDACS aims to exploit the vacant spectrum between incumbent Distance Measuring Equipment (DME) signals and envisioned to follow an orthogonal frequency division multiplexing (OFDM) approach to support high-speed delay-sensitive multimedia services. This paper deals with the design and implementation of end-to-end LDACS the transceiver on the Zynq System on Chip platform, consisting of FPGA as programmable logic (PL) and ARM as processing system (PS). We consider OFDM based LDACS and improve it further using windowing and/or filtering. We propose a hardware-software co-design approach and analyze various transceiver configurations by dividing it into PL and PS. We demonstrate the flexibility offered by such a co-design approach to choose the configuration as well as word-length for a given area, delay and power constraints. The transceiver is also integrated with the programmable analog front-end to validate its functionality in the presence of various RF impairments and wireless channels and interference specific to the LDACS environment. Via in-depth performance analysis concerning parameters such as out-of-band attenuation, DME interference, bit-error-rate, word-length, and complexity, we demonstrate wide bandwidth filtered OFDM as an attractive solution for the next generation LDACS.

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arXiv2016

FPGA Implementation of High Speed Reconfigurable Filter Bank for Multi-standard Wireless Communication Receivers

In next generation wireless communication system, wireless transceivers should be able to handle wideband input signals compromising of multiple communication standards.Such multi-standard wireless communication receivers (MWCRs) need filter bank to extract the desired signal of interest from wideband input spectrum and bring it to the baseband for further signal processing tasks such as spectrum sensing, modulation classification,demodulation etc.In MWCRs,rather any wireless receivers, modulated filter banks, such as Discrete Fourier Transform Filter Banks (DFTFB), are preferred due to their advantages such as lower area, delay and power requirements. To support multi-standard operation, reconfigurable DFTFB (RDFTFB) was proposed by integrating DFTFB with the coefficient decimation method. In this paper, an efficient high speed implementation of RDFTFB on Virtex-7 field programmable gate arrays (FPGA) has been proposed.The proposed approach minimizes the critical path delay between clocked registers thereby leading to significant improvement in the maximum operating frequency of the RDFTFB. Numerically, the proposed implementation leads to 89.7% improvement in the maximum frequency at which RDFTFB can be clocked.Furthermore,proposed implementation leads to 18.5% reduction in the dynamic power consumption.

cs.IT↗

arXiv2016

Design of Variable Bandpass Filters Using First Order Allpass Transformation And Coefficient Decimation

In this paper, the design of a computationally efficient variable bandpass digital filter is presented. The center frequency and bandwidth of this filter can be changed online without updating the filter coefficients. The warped filters, obtained by replacing each unit delay of a digital filter with an allpass filter, are widely used for various audio processing applications. However, warped filters fail to provide variable bandwidth bandpass responses for a given center frequency using first order allpass transformation. To overcome this drawback, our design is accomplished by combining warped filter with the coefficient decimation technique. The design example shows that the proposed variable digital filter is simple to design and offers a total gate count reduction of 36% and 65% over the warped filters compared to the designs presented in [3] and [1] respectively

cs.SD↗

arXiv2016

A Low Complexity Spectrum Sensing Scheme for Estimating Frequency Band Edges in Multi-Standard Military Communication Receivers

In a typical multi-standard military communication receiver, fast and reliable spectrum sensing unit is required to extract the information of multiple channels (frequency bands) present in a wideband input signal. In this paper, an energy detector based on our reconfigurable filter bank, in [5], for detecting the edge frequencies of the channels is proposed. Simulation results are presented to show the trade-off between the time required to calculate edge frequencies of all the channels and the maximum normalized error in estimating the edge frequencies. The proposed method is compared with existing energy detector methods for complexity and performance. It is shown that, for a fixed number of input samples, error decreases with time in the proposed algorithm as compared to other methods where error is constant. Design examples and simulations show that the complexity of the proposed method is lower than the other methods for a given error in estimating the edge frequencies

cs.IT↗