The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Shalabh Gupta - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of an LO-less, DSP-free QPSK Receiver for Data Center Interconnects
arXiv: Signal Processing, 2019Co-Authors: Rashmi Kamran, Nandakumar Nambath, Nandish Bharat Thaker, Mehul Anghan, Sarath Manikandan, Rakesh Ashok, Shalabh GuptaAbstract:We present the first demonstration of a local oscillator (LO)-less digital signal processing (DSP)-free coherent receiver for high-capacity short distance optical links. Experimental results with an Analog Domain constant modulous algorithm (CMA)-based equalizer chip for the self-homodyne quadrature phase shift keying (SH-QPSK) system validate the employability of an all-Analog and LO-less receiver for low-power interconnects.
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WOCC - Demonstration of a polarization diversity based SH-QPSK system with CMA-DFE equalizer
2017 26th Wireless and Optical Communication Conference (WOCC), 2017Co-Authors: Rashmi Kamran, Nandakumar Nambath, Nandish Bharat Thaker, Mehul Anghan, Shalabh GuptaAbstract:An optimum solution for a low power and low cost coherent optical receiver design can be obtained by a self homodyne (SH) system that uses Analog Domain processing. An SH system eliminates the need of a local oscillator (LO) and a carrier phase recovery (CPR) module at the receiver. Due to the inherent line-width tolerance of SH systems, an expensive laser is not required at the transmitter. In digital processing based receivers, Analog-to-digital converters (ADC) are the dominant source of power and cost; signal processing in the Analog Domain can get rid of the usage of ADCs. Combination of these two approaches can lead to a huge power and cost saving. An SH-QPSK system with a polarization multiplexed carrier is experimentally demonstrated with a 28km standard single mode fiber (SSMF) channel and off-line signal processing at the receiver side. The system does not use any optical amplification and dispersion compensating fiber. A novel Analog Domain constant modulus algorithm-decision feedback equalizer (CMA-DFE) is proposed which is a cascade combination of two different types of equalizers. This proposed scheme gives improvement in the performance over an optimum CMA equalizer, because of the difference of minimum mean square errors (MMSE) of two different cost functions.
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WOCC - Analog Domain decision feedback equalizer for repeater-less DP-QPSK coherent optical links
2016 25th Wireless and Optical Communication Conference (WOCC), 2016Co-Authors: Mukul Ratwani, Nandakumar Nambath, Rashmi Kamran, Shalabh GuptaAbstract:Optimization of high speed coherent optical receivers in terms of power consumption and complexity can be achieved by processing received signals in the Analog Domain without converting them into the digital Domain. At a particular data rate an equalizer based on Analog delay cells alone will be limited by the link distance. It is due to the reduction of the overall bandwidth of cascaded delay cells needed to compensate for more dispersion. This issue can be addressed by including digital delay cells in a feedback path which reduces the number of Analog delay cells without compromising the performance of the equalizer. We present a low power Analog Domain decision feedback equalizer for dual polarization-quadrature phase shift keying systems which can be used for a repeater-less distance of up to 80km of non zero dispersion shifted fiber. The proposed equalizer gives a pre forward error correction bit error rate of 10−4 at a received signal to noise ratio of 20 dB.
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VLSI Design - Wideband Active Delay Cell Design for Analog Domain Coherent DP-QPSK Optical Receiver
2016 29th International Conference on VLSI Design and 2016 15th International Conference on Embedded Systems (VLSID), 2016Co-Authors: Saurabh Anmadwar, Nandakumar Nambath, Shalabh GuptaAbstract:Signal processing in Analog Domain is an attractive technique for achieving low-power coherent optical link receivers as opposed to DSP (digital signal processing) based receivers. The linear equalizer is one of the most important building blocks in these receivers. An Analog Domain equalizer requires wideband delay circuits for providing a constant delay with the desired bandwidth. This paper discusses the delay-bandwidth-area trade-off encountered while designing these delay circuits with low power consumption. A novel topology of a wideband active delay cell for a 100 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) receivers has been presented. As the delay cell has a 60 GHz bandwidth, several such delay cells can be cascaded to obtain larger delay with an overall acceptable bandwidth (for example, a delay of 100 ps with 20 GHz bandwidth). With this delay circuit designed in a 130 nm BiCMOS technology, we are able to achieve a delay × bandwidth/power product that is about 3 times better than the available state-of-the-art.
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Analog Domain Signal Processing-Based Low-Power 100-Gb/s DP-QPSK Receiver
Journal of Lightwave Technology, 2015Co-Authors: Nandakumar Nambath, Rejin K Raveendranath, Debopam Banerjee, Atishay Sharma, Appu Sankar, Shalabh GuptaAbstract:Coherent techniques are expected to be used to meet the demand for higher data rates in short-reach optical links in the near future. Digital coherent receivers used for long haul applications are not suitable for short-reach links because of excessive power dissipation, size, and cost. The power consumption, size, and cost of the receiver can be drastically reduced by processing signals in the Analog Domain itself. A 100 Gb/s dual-polarization quadrature phase-shift keying receiver that uses Analog Domain signal processing is presented. The receiver, designed in 130-nm BiCMOS technology, consumes 3.5 W of power. Simulations show bit error rates of less than $10^{-3}$ in the presence of dispersion up to 160 ps/nm, laser linewidths of up to 200 kHz, and a frequency offset of 100 MHz between the transmitter and the receiver lasers.
Nandakumar Nambath - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of an LO-less, DSP-free QPSK Receiver for Data Center Interconnects
arXiv: Signal Processing, 2019Co-Authors: Rashmi Kamran, Nandakumar Nambath, Nandish Bharat Thaker, Mehul Anghan, Sarath Manikandan, Rakesh Ashok, Shalabh GuptaAbstract:We present the first demonstration of a local oscillator (LO)-less digital signal processing (DSP)-free coherent receiver for high-capacity short distance optical links. Experimental results with an Analog Domain constant modulous algorithm (CMA)-based equalizer chip for the self-homodyne quadrature phase shift keying (SH-QPSK) system validate the employability of an all-Analog and LO-less receiver for low-power interconnects.
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WOCC - Demonstration of a polarization diversity based SH-QPSK system with CMA-DFE equalizer
2017 26th Wireless and Optical Communication Conference (WOCC), 2017Co-Authors: Rashmi Kamran, Nandakumar Nambath, Nandish Bharat Thaker, Mehul Anghan, Shalabh GuptaAbstract:An optimum solution for a low power and low cost coherent optical receiver design can be obtained by a self homodyne (SH) system that uses Analog Domain processing. An SH system eliminates the need of a local oscillator (LO) and a carrier phase recovery (CPR) module at the receiver. Due to the inherent line-width tolerance of SH systems, an expensive laser is not required at the transmitter. In digital processing based receivers, Analog-to-digital converters (ADC) are the dominant source of power and cost; signal processing in the Analog Domain can get rid of the usage of ADCs. Combination of these two approaches can lead to a huge power and cost saving. An SH-QPSK system with a polarization multiplexed carrier is experimentally demonstrated with a 28km standard single mode fiber (SSMF) channel and off-line signal processing at the receiver side. The system does not use any optical amplification and dispersion compensating fiber. A novel Analog Domain constant modulus algorithm-decision feedback equalizer (CMA-DFE) is proposed which is a cascade combination of two different types of equalizers. This proposed scheme gives improvement in the performance over an optimum CMA equalizer, because of the difference of minimum mean square errors (MMSE) of two different cost functions.
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WOCC - Analog Domain decision feedback equalizer for repeater-less DP-QPSK coherent optical links
2016 25th Wireless and Optical Communication Conference (WOCC), 2016Co-Authors: Mukul Ratwani, Nandakumar Nambath, Rashmi Kamran, Shalabh GuptaAbstract:Optimization of high speed coherent optical receivers in terms of power consumption and complexity can be achieved by processing received signals in the Analog Domain without converting them into the digital Domain. At a particular data rate an equalizer based on Analog delay cells alone will be limited by the link distance. It is due to the reduction of the overall bandwidth of cascaded delay cells needed to compensate for more dispersion. This issue can be addressed by including digital delay cells in a feedback path which reduces the number of Analog delay cells without compromising the performance of the equalizer. We present a low power Analog Domain decision feedback equalizer for dual polarization-quadrature phase shift keying systems which can be used for a repeater-less distance of up to 80km of non zero dispersion shifted fiber. The proposed equalizer gives a pre forward error correction bit error rate of 10−4 at a received signal to noise ratio of 20 dB.
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VLSI Design - Wideband Active Delay Cell Design for Analog Domain Coherent DP-QPSK Optical Receiver
2016 29th International Conference on VLSI Design and 2016 15th International Conference on Embedded Systems (VLSID), 2016Co-Authors: Saurabh Anmadwar, Nandakumar Nambath, Shalabh GuptaAbstract:Signal processing in Analog Domain is an attractive technique for achieving low-power coherent optical link receivers as opposed to DSP (digital signal processing) based receivers. The linear equalizer is one of the most important building blocks in these receivers. An Analog Domain equalizer requires wideband delay circuits for providing a constant delay with the desired bandwidth. This paper discusses the delay-bandwidth-area trade-off encountered while designing these delay circuits with low power consumption. A novel topology of a wideband active delay cell for a 100 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) receivers has been presented. As the delay cell has a 60 GHz bandwidth, several such delay cells can be cascaded to obtain larger delay with an overall acceptable bandwidth (for example, a delay of 100 ps with 20 GHz bandwidth). With this delay circuit designed in a 130 nm BiCMOS technology, we are able to achieve a delay × bandwidth/power product that is about 3 times better than the available state-of-the-art.
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Analog Domain Signal Processing-Based Low-Power 100-Gb/s DP-QPSK Receiver
Journal of Lightwave Technology, 2015Co-Authors: Nandakumar Nambath, Rejin K Raveendranath, Debopam Banerjee, Atishay Sharma, Appu Sankar, Shalabh GuptaAbstract:Coherent techniques are expected to be used to meet the demand for higher data rates in short-reach optical links in the near future. Digital coherent receivers used for long haul applications are not suitable for short-reach links because of excessive power dissipation, size, and cost. The power consumption, size, and cost of the receiver can be drastically reduced by processing signals in the Analog Domain itself. A 100 Gb/s dual-polarization quadrature phase-shift keying receiver that uses Analog Domain signal processing is presented. The receiver, designed in 130-nm BiCMOS technology, consumes 3.5 W of power. Simulations show bit error rates of less than $10^{-3}$ in the presence of dispersion up to 160 ps/nm, laser linewidths of up to 200 kHz, and a frequency offset of 100 MHz between the transmitter and the receiver lasers.
Sridhar Rajagopal - One of the best experts on this subject based on the ideXlab platform.
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multimode precoding in millimeter wave mimo transmitters with multiple antenna sub arrays
Global Communications Conference, 2013Co-Authors: Omar El Ayach, Sridhar Rajagopal, Robert W. Heath, Zhouyue PiAbstract:Millimeter wave (mmWave) systems must use beamforming to overcome the heavy attenuation at mmWave frequencies and establish high-quality communication links with reasonably high spectral efficiency. When received signal power is sufficiently large and the propagation channel is sufficiently rich, beamforming with multiple data streams, known as precoding, could further increase data rates in mmWave systems. The high cost of digital devices in mmWave systems, however, implies that precoding is predominantly done in the Analog Domain, making mmWave precoding significantly more constrained than traditional multiple-input multiple-output (MIMO) solutions. In this paper, we propose an iterative precoding algorithm for a practical mmWave transmitter architecture in which all precoding is done in the Analog Domain. In addition to precoding, the proposed algorithm allows the mmWave system to adapt the rank of its transmission in response to varying propagation conditions. We present numerical results showing that the proposed multimode precoding algorithm allows systems to achieve large data rates, in some cases approaching channel capacity.
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GLOBECOM - Multimode precoding in millimeter wave MIMO transmitters with multiple antenna sub-arrays
2013 IEEE Global Communications Conference (GLOBECOM), 2013Co-Authors: Omar El Ayach, Robert W. Heath, Sridhar RajagopalAbstract:Millimeter wave (mmWave) systems must use beamforming to overcome the heavy attenuation at mmWave frequencies and establish high-quality communication links with reasonably high spectral efficiency. When received signal power is sufficiently large and the propagation channel is sufficiently rich, beamforming with multiple data streams, known as precoding, could further increase data rates in mmWave systems. The high cost of digital devices in mmWave systems, however, implies that precoding is predominantly done in the Analog Domain, making mmWave precoding significantly more constrained than traditional multiple-input multiple-output (MIMO) solutions. In this paper, we propose an iterative precoding algorithm for a practical mmWave transmitter architecture in which all precoding is done in the Analog Domain. In addition to precoding, the proposed algorithm allows the mmWave system to adapt the rank of its transmission in response to varying propagation conditions. We present numerical results showing that the proposed multimode precoding algorithm allows systems to achieve large data rates, in some cases approaching channel capacity.
Omar El Ayach - One of the best experts on this subject based on the ideXlab platform.
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multimode precoding in millimeter wave mimo transmitters with multiple antenna sub arrays
Global Communications Conference, 2013Co-Authors: Omar El Ayach, Sridhar Rajagopal, Robert W. Heath, Zhouyue PiAbstract:Millimeter wave (mmWave) systems must use beamforming to overcome the heavy attenuation at mmWave frequencies and establish high-quality communication links with reasonably high spectral efficiency. When received signal power is sufficiently large and the propagation channel is sufficiently rich, beamforming with multiple data streams, known as precoding, could further increase data rates in mmWave systems. The high cost of digital devices in mmWave systems, however, implies that precoding is predominantly done in the Analog Domain, making mmWave precoding significantly more constrained than traditional multiple-input multiple-output (MIMO) solutions. In this paper, we propose an iterative precoding algorithm for a practical mmWave transmitter architecture in which all precoding is done in the Analog Domain. In addition to precoding, the proposed algorithm allows the mmWave system to adapt the rank of its transmission in response to varying propagation conditions. We present numerical results showing that the proposed multimode precoding algorithm allows systems to achieve large data rates, in some cases approaching channel capacity.
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GLOBECOM - Multimode precoding in millimeter wave MIMO transmitters with multiple antenna sub-arrays
2013 IEEE Global Communications Conference (GLOBECOM), 2013Co-Authors: Omar El Ayach, Robert W. Heath, Sridhar RajagopalAbstract:Millimeter wave (mmWave) systems must use beamforming to overcome the heavy attenuation at mmWave frequencies and establish high-quality communication links with reasonably high spectral efficiency. When received signal power is sufficiently large and the propagation channel is sufficiently rich, beamforming with multiple data streams, known as precoding, could further increase data rates in mmWave systems. The high cost of digital devices in mmWave systems, however, implies that precoding is predominantly done in the Analog Domain, making mmWave precoding significantly more constrained than traditional multiple-input multiple-output (MIMO) solutions. In this paper, we propose an iterative precoding algorithm for a practical mmWave transmitter architecture in which all precoding is done in the Analog Domain. In addition to precoding, the proposed algorithm allows the mmWave system to adapt the rank of its transmission in response to varying propagation conditions. We present numerical results showing that the proposed multimode precoding algorithm allows systems to achieve large data rates, in some cases approaching channel capacity.
David V. Anderson - One of the best experts on this subject based on the ideXlab platform.
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ICASSP - Compressive sensing on a CMOS separable transform image sensor
2008 IEEE International Conference on Acoustics Speech and Signal Processing, 2008Co-Authors: Ryan Robucci, Leung Kin Chiu, J.d. Gray, Justin Romberg, Paul Hasler, David V. AndersonAbstract:This paper discusses the application of a computational image sensor, capable of performing separable 2-D transforms on images in the Analog Domain, to compressive sensing. Instead of sensing and transmitting raw pixel data, this image sensor first projects the image onto a separable 2-D basis set. The inner products computed in these projections are computed in the Analog Domain using a computational focal-plane and a computational Analog vector-matrix multiplier. Since this operation is performed in the Analog Domain, components such as the Analog-to-digital converters can be taxed less when a only subset of correlations are performed. Compressed sensing theory prescribes the use of a pseudo-random, incomplete basis set, allowing for sampling at less than the Nyquist rate. This can reduce power consumption or increase frame rate.
