Multicarrier phase modulated continuous waveform for automotive joint radar-communication system

in 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (2018)

Automotive radar implementation in the mm Wave band (79 G Hz) is being increasingly considered for the high bandwidths offered. While the radar systems and technology is maturing in mm Wave bands, the ... [more ▼]

Automotive radar implementation in the mm Wave band (79 G Hz) is being increasingly considered for the high bandwidths offered. While the radar systems and technology is maturing in mm Wave bands, the reuse of radar spectrum for low latency, limited throughput and safety critical communication has started to receive attention of late. Towards this, a joint radar-communication (JRC) system is proposed where the platform performs sensing and communication operations. The major challenge in JRC waveform design is the lack of degrees of freedom (DoF), due to need to estimate communication symbols in addition to the radar parameters. In this work, we propose a novel automotive JRC system based on multicarrier phase-modulated continuous waveform (MC-PMCW). MC-PMCW provides sufficient DoF to confine desired parameters, i.e., angles of arrival, Doppler shifts, ranges, and communication symbols in different dimensions. It can overcome the limitations of conventional PMCW and OFDM waveforms by leveraging the multicarrier feature of OFDM and the code sequence of PMCW to embed radar and communication. Further, the separation of parameters into different domains reduces complexity and enhances robustness; this is desirable in automotive scenarios characterized by dynamic scenes. Numerical results demonstrate the effectiveness of the proposed system. [less ▲]

Coverage Extension via Side-Lobe Transmission in Multibeam Satellite System

in 23rd Ka and Broadband Communications Conference (2017, October 16)

In this paper, we study feasibility of coverage extension of a multibeam satellite network by providing low-rate communications to terminals located outside the coverage of main beams. Focusing on the MEO ... [more ▼]

In this paper, we study feasibility of coverage extension of a multibeam satellite network by providing low-rate communications to terminals located outside the coverage of main beams. Focusing on the MEO satellite network, and using realistic link budgets from O3b networks, we investigate the performance of both forward and return-links for terminals stationed in the side lobes of the main beams. Particularly, multi-carrier transmission for forward-link and single carrier transmission for return-link are examined and the resulting coverage and data rate for different setups are evaluated. Simulation results verifies that side-lobe transmission can extend the coverage area and provide considerable data rate, thereby providing a solution for enhancing capacity of existing networks. [less ▲]

Random Phase Center Motion Technique for Enhanced Angle-Doppler Discrimination Using MIMO Radars

in European Signal Processing Conference (EUSIPCO) 2017 (2017, August)

A random Phase Center Motion (PCM) technique is presented in this paper, based on Frequency Modulated Continuous Wave (FMCW) radar, in order to suppress the angle- Doppler coupling in Time Division ... [more ▼]

A random Phase Center Motion (PCM) technique is presented in this paper, based on Frequency Modulated Continuous Wave (FMCW) radar, in order to suppress the angle- Doppler coupling in Time Division Multiplex (TDM) Multiple- Input-Multiple-Output (MIMO) radar when employing sparse array structures. The presented approach exploits an apparently moving transmit platform or PCM due to spatio-temporal transmit array modulation. In particular, the work considers a framework utilizing a random PCM trajectory. The statistical characterization of the random PCM trajectory is devised, such that the PCM and the target motion coupling is minimal, while the angular resolution is increased by enabling the virtual MIMO concept. In more details, this paper discusses sidelobe suppression approaches within the angle-Doppler Ambiguity Function (AF) by introducing a phase center probability density function within the array. This allows for enhanced discrimination of multiple targets. Simulation results demonstrate the suppression angle- Doppler coupling by more than 30 dB, even though spatiotemporal transmit array modulation is done across chirps which leads usually to strong angle-Doppler coupling. [less ▲]

Multi-Target Localization in Asynchronous MIMO Radars Using Sparse Sensing

in IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP) (2017)

Multi-target localization, warranted in emerging applications like autonomous driving, requires targets to be perfectly detected in the distributed nodes with accurate range measurements. This implies ... [more ▼]

Multi-target localization, warranted in emerging applications like autonomous driving, requires targets to be perfectly detected in the distributed nodes with accurate range measurements. This implies that high range resolution is crucial in distributed localization in the considered scenario. This work proposes a new framework for multi-target localization, addressing the demand for the high range resolution in automotive applications without increasing the required bandwidth. In particular, it employs sparse stepped frequency waveform and infers the target ranges by exploiting sparsity in target scene. The range measurements are then sent to a fusion center where direction of arrival estimation is undertaken. Numerical results illustrate the impact of range resolution on multi-target localization and the performance improvement arising from the proposed algorithm in such scenarios. [less ▲]

Max-min transmit beamforming via iterative regularization

in 50th Asilomar Conference on Signals, Systems and Computers, November 2016 (2016, November)

This paper introduces an iterative optimization framework to tackle the multi-group multicast Max-Min transmit beamforming problem. In each iteration, the optimization problem is decomposed into four sub ... [more ▼]

This paper introduces an iterative optimization framework to tackle the multi-group multicast Max-Min transmit beamforming problem. In each iteration, the optimization problem is decomposed into four sub-problems, all of which can be solved using computationally efficient algorithms. The advantage of proposed method lies in its ability to handle different types of signal constraints like total power and unimodularity; a feature not exhibited by other techniques. The proposed technique outperforms the well-known semidefinite relaxation method in terms of quality of solutions [less ▲]

Return Link Optimized Resource Allocation for Satellite Communications in the Ku/Ka-Band

in Proceedings on the 22nd Ka and Broadband Communications Conference and the 34th AIAA International Communications Satellite Systems Conference (ICSSC) (2016, October)

Broadband satellite networks play an important role in today’s worldwide telecommunication infrastructure, providing services to an increasing number of users. Therefore, an efficient management of the ... [more ▼]

Broadband satellite networks play an important role in today’s worldwide telecommunication infrastructure, providing services to an increasing number of users. Therefore, an efficient management of the spectrum resources is required in order to meet the fast-growing service demand. To this purpose, this paper addresses the optimization of the return carrier frequency plan for a broadband network benefiting from adaptive return channel selection (ARCS). The optimization problem is formulated as a multiobjective instance aiming at minimizing the total bandwidth and the unused throughput by using integer linear programming techniques. So as to capture events in which multiple terminals experience fade simultaneously, the spatial correlation of the attenuation fields has been incorporated in the optimization process. Moreover, physical layer characteristics and a minimum guaranteed throughput per user have been included as optimization constraints. Hence, the final outcome of this paper is a general technique providing an optimized carrier allocation plan, i.e., the number of carriers required to cover a certain area and guarantee a given throughput to each user. [less ▲]

An Iterative Approach to Nonconvex QCQP with Applications in Signal Processing

in 2016 IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) (2016, July 10)

This paper introduces a new iterative approach to solve or to approximate the solutions of the nonconvex quadratically constrained quadratic programs (QCQP). First, this constrained problem is transformed ... [more ▼]

This paper introduces a new iterative approach to solve or to approximate the solutions of the nonconvex quadratically constrained quadratic programs (QCQP). First, this constrained problem is transformed to an unconstrained problem using a specialized penalty-based method. A tight upper-bound for the alternative unconstrained objective is introduced. Then an efficient minimization approach to the alternative unconstrained objective is proposed and further studied. The proposed approach involves power iterations and minimization of a convex scalar function in each iteration, which are computationally fast. The important design problem of multigroup multicast beamforming is formulated as a nonconvex QCQP and solved using the proposed method. [less ▲]

Joint Predistortion and PAPR Reduction in Multibeam Satellite Systems

in Proceedings of IEEE ICC 2016 (2016, May)

Precoding for multibeam satellites with aggressive frequency reuse has attracted interest of late towards enhancing system capacity. Most of the works on precoding mitigate the linear co-channel ... [more ▼]

Precoding for multibeam satellites with aggressive frequency reuse has attracted interest of late towards enhancing system capacity. Most of the works on precoding mitigate the linear co-channel interference between the beams caused by frequency reuse. How- ever, the high power amplifier (HPA), an integral part of the satellite payload, is inherently non linear. Non-linear amplification combined with the linear co-channel interference introduces non- linear co-channel distortions at the receiver. Further, signals with very high peak to average power ratios (PAPR), typical of spectrally efficient modulations, are sensitive to the non-linear characteristic of the HPA and necessitate large back-off to have manageable distortion levels. In this work, a novel architecture comprising multistream Crest Factor Reduction (signal pre-clipping) and Signal Predistortion (SPD) in cascade, is devised to counter the non- linearities and co-channel interference in multibeam satellite sys- tems. An iterative algorithm to optimize the parameters of the signal clipping and predistortion is devised taking recourse to analytical derivations. The proposed joint estimation paradigm is shown to compare favorably with state-of-art and provides a framework to combine predistortion and precoding. [less ▲]

Grab-n-Pull: An Optimization Framework for Fairness-Achieving Networks

in IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) 2016 (2016, March 20)

In this paper, we present an optimization framework for designing precoding (a.k.a. beamforming) signals that are instrumental in achieving a fair user performance through the networks. The precoding ... [more ▼]

In this paper, we present an optimization framework for designing precoding (a.k.a. beamforming) signals that are instrumental in achieving a fair user performance through the networks. The precoding design problem in such scenarios can typically be formulated as a non-convex max-min fractional quadratic program. Using a penalized version of the original design problem, we derive a simplified quadratic reformulation of the problem in terms of the signal (to be designed). Each iteration of the proposed design framework consists of a combination of power method-like iterations and the Gram-Schmidt process, and as a result, enjoys a low computational cost. Moreover, the suggested approach can handle various types of signal constraints such as total-power, per-antenna power, unimodularity, or discrete-phase requirements—an advantage which is not shared by other existing approaches in the literature. [less ▲]

Cooperative Estimation of Power and Direction of Transmission for a Directive Source

in IEEE Transactions on Cognitive Communications and Networking (2016)

Reliable spectrum cartography of directive sources depends on an accurate estimation of the direction of transmission (DoT) as well as the transmission power. Joint estimation of power and DoT of a ... [more ▼]

Reliable spectrum cartography of directive sources depends on an accurate estimation of the direction of transmission (DoT) as well as the transmission power. Joint estimation of power and DoT of a directive source using ML estimation techniques is considered in this paper. We further analyze the parametric identifiability conditions of the problem, develop the estimation algorithm, and derive the Cramer-Rao-Bound (CRB) for the two situations: a) where the source signal is known to the sensors, and b) where the sensors are not aware of the source signal but its distribution. Particularly, we devise a specific sensor placement/selection setup for the symmetric antenna patterned sources which leads to identifiability of the problem. Finally, numerical results verifies the efficiency and accuracy of the provided estimation algorithms in this paper. [less ▲]