Papers by Oshri Naparstek
arXiv (Cornell University), Jan 8, 2014
Design of energy efficient protocols for modern wireless systems has become an important area of ... more Design of energy efficient protocols for modern wireless systems has become an important area of research. In this paper, we propose a distributed optimization algorithm for the channel assignment problem for multiple interfering transceiver pairs that cannot communicate with each other. We first modify the auction algorithm for maximal energy efficiency and show that the problem can be solved without explicit message passing using the carrier sense multiple access (CSMA) protocol. We then develop a novel scheme by converting the channel assignment problem into perfect matchings on bipartite graphs. The proposed scheme improves the energy efficiency and does not require any explicit message passing or a shared memory between the users. We derive bounds on the convergence rate and show that the proposed algorithm converges faster than the distributed auction algorithm and achieves near-optimal performance under Rayleigh fading channels. We also present an asymptotic performance analysis of the fast matching algorithm for energy efficient resource allocation and prove the optimality for large enough number of users and number of channels. Finally, we provide numerical assessments that confirm the energy efficiency gains compared to the state of the art. Index Terms-Auction algorithm, bipartite graph, channel assignment, energy efficiency (EE), linear programming, distributed protocol, multi-access channel, Rayleigh fading channel, resource management, wireless networks. I. INTRODUCTION Communication networks have been designed to optimize conventional performance measures such as bit-error-rate, latency, and data-rate in the past few decades. In the last few years, the issue of energy-efficient network design has gained more importance [1], [2], [3], [4]. Information and communication technologies (ICT) represent about 2% of the entire world's energy consumption, and the situation is likely to reach a point where ICT equipment in large cities will require more energy than is actually available [5]. For data networks, contrary to the intuition, more energy is consumed in access networks than in core networks. This happens because the number of devices in access networks (i.e. mobile terminals, base stations, and data modems installed on customers' premises) is much larger than the number of communication devices (routers, multiplexers, etc.) in the core network. This has sparked research in the field of wireless networks with a focus on the problem of optimizing the energy Oshri Naparstek was a Ph.D. student with Faculty of Engineering,
In this paper we describe the optimization of an information theoretic criterion for radar wavefo... more In this paper we describe the optimization of an information theoretic criterion for radar waveform design. The method is used to design radar waveforms suitable for simultaneously estimating and tracking parameters of multiple targets. Our approach generalizes the information theoretic water-lling approach of Bell. The paper has two main contributions. First, a new information theoretic design criterion for designing multiple waveforms under a joint power constraint when beamforming is used both at transmitter and receiver. Then we provide a highly ef cient algorithm for optimizing the transmitted waveforms, by approximating the information theoretic cost function. We show that using Lagrange relaxation the optimization problem can be decoupled into a parallel set of lowdimensional search problems at each frequency, with dimension de ned by the number of targets instead of the number of frequency bands used.
Bounds on the expected optimal channel assignment in Rayleigh channels
ABSTRACT The channel assignment problem is highly important to OFDMA cognitive radio systems. Tig... more ABSTRACT The channel assignment problem is highly important to OFDMA cognitive radio systems. Tight bounds on the optimal channel assignment are crucial for the performance evaluation of various channel assignment schemes. In this paper we derive the mean of the maximal sum rate channel assignment for iid Rayleigh fading channels. We provide upper and lower bounds on the expected optimal assignment. We then show that the bounds are asymptotically tight in both high SNR and as the number of users increases.
We consider the problem of dynamic spectrum access for network utility maximization in multichann... more We consider the problem of dynamic spectrum access for network utility maximization in multichannel wireless networks. The shared bandwidth is divided into K orthogonal channels, and the users access the spectrum using a random access protocol. In the beginning of each time slot, each user selects a channel and transmits a packet with a certain attempt probability. After each time slot, each user that has transmitted a packet receives a local observation indicating whether its packet was successfully delivered or not (i.e., ACK signal). The objective is to find a multiuser strategy that maximizes a certain network utility in a distributed manner without online coordination or message exchanges between users. Obtaining an optimal solution for the spectrum access problem is computationally expensive in general due to the large state space and partial observability of the states. To tackle this problem, we develop a distributed dynamic spectrum access algorithm based on deep multiuser reinforcement leaning. Specifically, at each time slot, each user maps its current state to spectrum access actions based on a trained deep-Q network used to maximize the objective function. Experimental results have demonstrated that users are capable to learn good policies that achieve strong performance in this challenging partially observable setting only from their ACK signals, without online coordination, message exchanges between users, or carrier sensing.
IEEE Journal of Selected Topics in Signal Processing, Jun 1, 2007
In this paper, we use an information theoretic approach to design radar waveforms suitable for si... more In this paper, we use an information theoretic approach to design radar waveforms suitable for simultaneously estimating and tracking parameters of multiple extended targets. Our approach generalizes the information theoretic water-filling approach of Bell to allow optimization for multiple targets simultaneously. Our paper has three main contributions. First, we present a new information theoretic design criterion for a single transmit waveform using a weighted linear sum of the mutual informations between target radar signatures and the corresponding received beams (given the transmitted waveforms). We provide a family of design criteria that weight the various targets according to priorities. Then, we generalize the information theoretic design criterion for designing multiple waveforms under a joint power constraint when beamforming is used both at the transmitter and the receiver. Finally, we provide a highly efficient algorithm for optimizing the transmitted waveforms in the cases of single waveform and multiple waveforms. We also provide simulated experiments of both algorithms based on real targets and comment on the generalization of the proposed technique for other design criteria, e.g., the linearly weighted noncausal MMSE design criterion. I. INTRODUCTION T HE problem of radar waveform design is of fundamental importance in designing state-of-the-art radar systems. The possibility to vary the transmitted signal on a pulse-by-pulse basis opens the door to great enhancement in estimation and detection capability as well as improved robustness to jamming. Furthermore modern radars can detect and track multiple targets simultaneously. Therefore, designing the transmitted waveforms for detecting and estimating multiple targets becomes a critical issue in radar waveform design. Most of existing waveform design literature deals with designs for a single target. One of the important tools in such de-Manuscript
Hybrid opportunistic radar over long term evolution networks
Passive radar systems that use an illuminator of choice have been extensively studied over the pa... more Passive radar systems that use an illuminator of choice have been extensively studied over the past decade because they are difficult to detect and cheaper to deploy. Among the signals investigated for passive radar are FM radio, DVB-T and cellular networks. Recently, UMTS and Long Term Evolution (LTE) signals have been considered for passive radar. In this paper we study specific aspects of LTE signals that make them profoundly different from other signals for passive radars. We show that the LTE protocol can be exploited to serve as an active radar when combined with an LTE enabled receiver. We explain how the transmitted waveforms can be controlled by PMI feedback and from the cellular unit to the base station to form an active MIMO radar.
In this paper we use information theoretic approach to design radar waveforms suitable for simult... more In this paper we use information theoretic approach to design radar waveforms suitable for simultaneously estimating and tracking parameters of multiple targets. Our approach generalizes the information theoretic water-filling approach of Bell. The paper has three main contributions: A new information theoretic design criteria for single transmit waveform with a receiving array using a weighted linear sum of the mutual informations between targets' radar signatures and the corresponding received beams (given the transmitted waveforms), we proivde a family of design criteria that weight the various targets according to priorities. Then we generalize the information theoretic design criteria for designing multiple waveforms under joint power constraint when beamforming is used both at transmitter and receiver. Finally we provide a highly efficient optimization algorithm for optimizing the transmitted waveforms both for single target and multiple targets. We show that the optimization problem in both cases can be decoupled into a parallel set of low dimensional search problems at each frequency, with dimension defined by the number of targets, instead of the number of frequency bands used. The power constraint is forced through the optimization of a single Lagrange multiplier for the dual problem. We end with comments on the generalization of the proposed technique for other design criteria, e.g., for the linearly weighted MMSE design criterion.
Fully distributed auction algorithm for spectrum sharing in unlicensed bands
Abstract In this paper we introduce a modified auction algorithm that can be applied in a fully d... more Abstract In this paper we introduce a modified auction algorithm that can be applied in a fully distributed manner. The algorithm requires an auctioneer but does not require shared memory or message passing between bidders. We show that an opportunistic carrier sensing scheme can be used to replace the auctioneer in a manner that does not require any message passing, control channel or any other explicit information sharing between users. Bounds on optimality are given as well as simulated results.
A fast matching algorithm for asymptotically optimal distributed channel assignment
ABSTRACT The channel assignment problem is a special case of a very well studied combinatorial op... more ABSTRACT The channel assignment problem is a special case of a very well studied combinatorial optimization problem known as the assignment problem. In this paper we introduce an asymptotically optimal fully distributed algorithm for the maximum cardinality matching problem. We show that with high probability, the running time of the algorithm on random bipartite graphs is less than O (N log(N)/log Np)) . We then show that the proposed algorithm can be used to produce asymptotically optimal solutions for the max sum assignment problem.
IEEE Transactions on Wireless Communications, 2019
We consider the problem of dynamic spectrum access for network utility maximization in multichann... more We consider the problem of dynamic spectrum access for network utility maximization in multichannel wireless networks. The shared bandwidth is divided into K orthogonal channels. In the beginning of each time slot, each user selects a channel and transmits a packet with a certain transmission probability. After each time slot, each user that has transmitted a packet receives a local observation indicating whether its packet was successfully delivered or not (i.e., ACK signal). The objective is a multiuser strategy for accessing the spectrum that maximizes a certain network utility in a distributed manner without online coordination or message exchanges between users. Obtaining an optimal solution for the spectrum access problem is computationally expensive in general due to the large state space and partial observability of the states. To tackle this problem, we develop a novel distributed dynamic spectrum access algorithm based on deep multiuser reinforcement leaning. Specifically, at each time slot, each user maps its current state to spectrum access actions based on a trained deep-Q network used to maximize the objective function. Game theoretic analysis of the system dynamics is developed for establishing design principles for the implementation of the algorithm. Experimental results demonstrate strong performance of the algorithm.
Joint adaptive waveform design and direction-of-arrival tracking
Abstract The ability to adapt waveforms to the changing properties of targets is a very important... more Abstract The ability to adapt waveforms to the changing properties of targets is a very important feature for radars. Adaptive waveform design can improve the estimation and tracking of targets dramatically. In this paper we propose a joint scheme for adaptive multiple waveforms design and multi-target parameter estimation and tracking for extended targets. We combine our previous work on information theoretic waveform design for multiple extended targets with an iterative joint direction-of-arrival and target frequency response ...
IEEE Communications Letters, Mar 1, 2012
The performance of Digital Subscriber Line (DSL) systems is tightly dependent on network deployme... more The performance of Digital Subscriber Line (DSL) systems is tightly dependent on network deployment. The users (lines) in the binder create mutual interference, thus decreasing the rates of all users. The Optimal Spectrum Balancing (OSB) algorithm solves the spectrum management problem to increase user rates. However, the computational complexity of the OSB algorithm is extremely high. In this paper we introduce a novel low-complexity sub-optimal algorithm, dubbed PArametric Spectrum Shaping (PASS). The complexity of the suggested algorithm is independent of the number of tones. Simulation results show that the PASS algorithm matches OSB performance in many typical DSL scenarios.
arXiv (Cornell University), Dec 31, 2013
In this paper we analyze the expected time complexity of the auction algorithm for the matching p... more In this paper we analyze the expected time complexity of the auction algorithm for the matching problem on random bipartite graphs. We prove that the expected time complexity of the auction algorithm for bipartite matching is O N log 2 (N) log(N p) on sequential machines. This is equivalent to other augmenting path algorithms such as the HK algorithm. Furthermore, we show that the algorithm can be implemented on parallel machines with O(log(N)) processors and shared memory with an expected time complexity of O(N log(N)).
Phased
Information theoretic waveform design for tracking multiple targets using
arXiv (Cornell University), Jul 4, 2022
For digitizing or indexing physical documents, Optical Character Recognition (OCR), the process o... more For digitizing or indexing physical documents, Optical Character Recognition (OCR), the process of extracting textual information from scanned documents, is a vital technology. When a document is visually damaged or contains non-textual elements, existing technologies can yield poor results, as erroneous detection results can greatly affect the quality of OCR. In this paper we present a detection network dubbed BusiNet aimed at OCR of business documents. Business documents often include sensitive information and as such they cannot be uploaded to a cloud service for OCR. BusiNet was designed to be fast and light so it could run locally preventing privacy issues. Furthermore, BusiNet is built to handle scanned document corruption and noise using a specialized synthetic dataset. The model is made robust to unseen noise by employing adversarial training strategies. We perform an evaluation on publicly available datasets demonstrating the usefulness and broad applicability of our model. CCS CONCEPTS • Information systems → Document structure; • Applied computing → Document analysis; Optical character recognition; • Computing methodologies → Object detection.
Abstract—In this paper, we use an information theoretic approach to design radar waveforms suitab... more Abstract—In this paper, we use an information theoretic approach to design radar waveforms suitable for simultaneously estimating and tracking parameters of multiple extended targets. Our approach generalizes the information theoretic water-filling approach of Bell to allow optimization for multiple targets simultaneously. Our paper has three main contributions. First, we present a new information theoretic design criterion for a single transmit waveform using a weighted linear sum of the mutual informations between target radar signatures and the corresponding received beams (given the transmitted waveforms). We provide a family of design criteria that weight the various targets according to priorities. Then, we generalize the information theoretic design criterion for designing multiple waveforms under a joint power constraint when beamforming is used both at the transmitter and the receiver. Finally, we provide a highly efficient algorithm for optimizing the transmitted waveforms...
Chapter CX-5 Information theoretic waveform design for tracking multiple targets using phased array radars
The problem of radar waveform design is of fundamental importance in designing state-of-the-art r... more The problem of radar waveform design is of fundamental importance in designing state-of-the-art radar systems. The possibility to vary the transmitted signal on a pulse-by-pulse basis opens the door to great enhancement in estimation and detection capability as well as improved robustness to jamming. Furthermore modern radars can detect and track multiple targets simultaneously. Therefore, designing the transmitted waveforms for detecting and estimating multiple targets becomes a critical issue in radar waveform design.
Information Theoretic Waveform Design for Tracking Multiple Targets Using Phased Array Radars
Principles of Waveform Diversity and Design
In this chapter we discussed the optimization of multiple waveforms for multiple targets under jo... more In this chapter we discussed the optimization of multiple waveforms for multiple targets under joint power constraint. This type of waveform design is suitable for unresolved extended targets. We have derived computationally efficient algorithms and presented the result of the optimization in simulations. Further results, as well as design of a single waveform optimized for multiple targets, can be found in [12]. The combination of waveform design and direction-of-arrival estimation is discussed in [13].
Hybrid opportunistic radar over long term evolution networks
2015 IEEE Radar Conference (RadarCon), 2015
Passive radar systems that use an illuminator of choice have been extensively studied over the pa... more Passive radar systems that use an illuminator of choice have been extensively studied over the past decade because they are difficult to detect and cheaper to deploy. Among the signals investigated for passive radar are FM radio, DVB-T and cellular networks. Recently, UMTS and Long Term Evolution (LTE) signals have been considered for passive radar. In this paper we study specific aspects of LTE signals that make them profoundly different from other signals for passive radars. We show that the LTE protocol can be exploited to serve as an active radar when combined with an LTE enabled receiver. We explain how the transmitted waveforms can be controlled by PMI feedback and from the cellular unit to the base station to form an active MIMO radar.
IEEE Communications Letters, 2012
The performance of Digital Subscriber Line (DSL) systems is tightly dependent on network deployme... more The performance of Digital Subscriber Line (DSL) systems is tightly dependent on network deployment. The users (lines) in the binder create mutual interference, thus decreasing the rates of all users. The Optimal Spectrum Balancing (OSB) algorithm solves the spectrum management problem to increase user rates. However, the computational complexity of the OSB algorithm is extremely high. In this paper we introduce a novel low-complexity sub-optimal algorithm, dubbed PArametric Spectrum Shaping (PASS). The complexity of the suggested algorithm is independent of the number of tones. Simulation results show that the PASS algorithm matches OSB performance in many typical DSL scenarios.
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Papers by Oshri Naparstek