Papers by Milena Stojanovic
An Algorithm For Multichannel Coherent Digital Communications Over Long Range Underwater Acoustic Telemetry Channels
OCEANS 92 Proceedings@m_Mastering the Oceans Through Technology
Abstract-The problem of achieving reliable digital communications over long range underwater acou... more Abstract-The problem of achieving reliable digital communications over long range underwater acoustic telemetry channels is addressed, and a receiver algorithm for multichannel coherent data detection is presented. The receiver consists of a T/2 ...
Towards robust adaptive acoustic communications
OCEANS 2000 MTS/IEEE Conference and Exhibition. Conference Proceedings (Cat. No.00CH37158)
Modulation and detection techniques used for underwater acoustic communications include phase coh... more Modulation and detection techniques used for underwater acoustic communications include phase coherent (PSK and QAM) and noncoherent (FSK) techniques. The objective of this work is the development of algorithms that can select the best technique for a given channel. The system of interest operates in shallow water over several kilometers in the 10-15 kHz band. A wideband probe is used
Sparse equalization for real-time digital underwater acoustic communications
'Challenges of Our Changing Global Environment'. Conference Proceedings. OCEANS '95 MTS/IEEE
... Acoustic Communications r\/larko Kocic, David Brady and Milica Stojanovic Department of Elect... more ... Acoustic Communications r\/larko Kocic, David Brady and Milica Stojanovic Department of Electrical and Computer Engineering Northeastern University, Boston, MA 02115, USA ... The use of a conventional DFE actually has a detrimental effect in a naturally sparse chan-nel. ...
Proceedings of IEEE Symposium on Autonomous Underwater Vehicle Technology (AUV'94)
This paper is concerned with the design of high data rate acoustic communication systems that emp... more This paper is concerned with the design of high data rate acoustic communication systems that employ adaptive equalization to overcome the effects of intersymbol interference and fading. (Our treatment is focused on the use of noiilinear decision-feedback equalization that is appropriate for high-speed, phase coherent digital communications on long range, deep water horizontal paths and medium range shallow water paths. The performance characteristics, limitations, and implementation complexities of adaptive eqiialization algorithms are also considered.
2010 IEEE International Symposium on Information Theory, 2010
Capacity scaling laws are analyzed in an underwater acoustic network with n regularly located nod... more Capacity scaling laws are analyzed in an underwater acoustic network with n regularly located nodes. A narrowband model is assumed where the carrier frequency is allowed to scale as a function of n. In the network, we characterize an attenuation parameter that depends on the frequency scaling as well as the transmission distance. A cut-set upper bound on the throughput scaling is then derived in extended networks. Our result indicates that the upper bound is inversely proportional to the attenuation parameter, thus resulting in a highly powerlimited network. Furthermore, we describe an achievable scheme based on the simple nearest-neighbor multi-hop (MH) transmission. It is shown under extended networks that the MH scheme is order-optimal as the attenuation parameter scales exponentially with √ n (or faster). Finally, these scaling results are extended to a random network realization.
TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference, 2009
We present a microfluidic biosensor suitable for selective detection of analytes with integrated ... more We present a microfluidic biosensor suitable for selective detection of analytes with integrated analyte preconcentration, isocratic elution and mass spectrometric detection. The device uses an aptamer (i.e., oligonucleotide that binds specifically to an analyte via affinity coupling) immobilized on microbeads to achieve highly selective analyte capture and concentration. Here, we demonstrate specific extraction and concentration of arginine vasopressin (a peptide hormone) by a vasopressin specific atpamer. In addition, the aptasensor is capable of isocratic elution and microbead regeneration via thermallyinduced reversibility of the aptamer-analyte binding mechanism, which renders the aptamer functionalized microbeads functional for repeated use. Furthermore, a microvalve directs the analyte onto an analysis plate for label-free detection by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS).
2008 International Symposium on Information Theory and Its Applications, 2008
The purpose of this paper is to show that convexity of the underwater acoustic channel and that n... more The purpose of this paper is to show that convexity of the underwater acoustic channel and that nearconvexity of an approximate closed-form model for that channel holds, in order to use network optimization techniques. We obtain a lower bound on transmission power using subgraph selection to establish minimumcost multicast connections in underwater acoustic networks with network coding. We solve this problem for a range of transmission distances that are of interest for practical systems and exploiting physical properties of the underwater acoustic channel. Since the complete model for the underwater channel is complex, an approximate model is used for numerical computations. We illustrate results numerically determining the lower bound on transmission power for different random twodimensional deployment scenarios and unicast rates. Also, we quantify the performance gap of two practical network layer schemes with respect to the lower bound.
Chirurgia (Bucharest, Romania : 1990)
Obstructive jaundice secondary to abdominal tuberculosis is extremely rare. We present a patient ... more Obstructive jaundice secondary to abdominal tuberculosis is extremely rare. We present a patient with jaundice secondary to compression of the common bile duct by TB lymphadenitis. A 49-year-old woman was admitted to our department for nausea,epigastric pain and jaundice. Abdominal ultrasonography and computer tomography scan were suggestive of stenosis of the distal common bile duct caused by a retro pancreatic mass. At laparotomy, an enlarged lymph node behind the head of the pancreas was found, causing compression and stenosis of the distal parts of the choledochus. The lymph node frozen section analysis showed epithelioid granuloma with caseous necrosis,strongly suggesting tuberculous origin. Choledochoduodenal anastomosis was performed. Definitive pathohistological examination confirmed TB lymphadenitis. ATB should be considered as a potential cause of jaundice especially in immuno compromised patients and endemic areas. Diagnosing abdominal tuberculosis can be a challenging ta...
A microfluidic device for isolation of cell-targeting aptamers
2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS), 2014
This paper presents a microfluidic device for affinity selection and amplification of cell membra... more This paper presents a microfluidic device for affinity selection and amplification of cell membrane protein-binding strands from a randomized single-strand DNA (ssDNA) oligomer library, thereby isolating specific cell-targeting aptamers. The device consists of the selection and amplification microchambers situated on a temperature control chip. Affinity selection, integrated with cell culturing, of cell-binding ssDNA is performed in the selection chamber; the selected strands are then amplified by bead-based polymerase chain reaction (PCR) in the amplification chamber. Transfer between the selection and amplification microchambers using pressure-driven flow realizes multi-round aptamer isolation on a single chip. Experimental results demonstrate the feasibility of using this device to develop aptamers that specifically bind to target cells.
2013 Asilomar Conference on Signals, Systems and Computers, 2013
Wireless Sensor Networks (WSNs) are commonly used to monitor physical or environmental parameters... more Wireless Sensor Networks (WSNs) are commonly used to monitor physical or environmental parameters such as temperature, sound, velocity, etc. Such networks find application in different areas including military, environmental, medical and industrial ones. For applications that require long term monitoring, data collection with limited resources (power, bandwidth) is a challenging problem. In addressing these challenges, we study a network architecture that relies on integrating sensing and random channel access to achieve energy efficiency. Specifically, this thesis focuses on the use of WSNs for target localization and tracking. In a random access framework, distributed sensor nodes transmit data packets to the fusion center at will, maintaining a given average transmission rate. The fusion center discards erroneous packets and those packets that have collided, and uses the remaining ones to recover the target information. Target localization is formulated as a sparse recovery problem, whose solution is sought through norm-1 regularized minimization techniques. This solution feeds the subsequent tracking phase, where the knowledge of target signatures is exploited to design an adaptive algorithm of low complexity. An adaptive framework is also developed, in which loss of tracking triggers a new localization phase. System performance is illustrated through computer simulation, showing that target localization and tracking can be achieved using only a fraction of sensors' measurements, conveyed in a random access fashion. I would also like to thank to my friends Melis Yetkinler, Seyhmus Guler, Umut Orhan, Mert Korkali, Cem Bila, and my fellow lab mates in Northeastern University CDSP Lab: Yashar M. Aval, Parastoo Qarabaqi, Rameez Ahmed and Osso Vahabzadeh for energizing conservations, academic supports and all the fun we have had in the last two years. Last but not the least; I would like to thank my family; my parents Mualla-Ilhan Kerse and my brother Can Kerse for supporting me in every way throughout my life.
2013 Asilomar Conference on Signals, Systems and Computers, 2013
Collecting data continuously from Wireless Sensor Networks (WSNs) with limited power and bandwidt... more Collecting data continuously from Wireless Sensor Networks (WSNs) with limited power and bandwidth is a challenging problem. Such networks have potential utility in a wide range of disciplines such as medical, industrial, environmental, and military applications. For long-term monitoring and surveillance applications, the objective is often times to cover as large an area as possible while still acquiring high-resolution information about the sensed environment. The main challenges involve energy-efficiency and scalability of the techniques used to acquire the substantial amount of data from the sensor network. Addressing these challenges, we propose a method that effectively exploits both spatial and temporal correlation inherent in sensor network data. The technique combines recent advances in Compressed Sensing (CS) theory, data compression, and a novel random access communication protocol. Sensor nodes perform in-situ temporal compression and transmit their compressed data over a random access channel to a fusion center (FC) to recover the field. If packets collide at the FC, they are simply discarded. A CS recovery algorithm, executed at the FC, allows the entire field to be recovered from the so-obtained observations. This method of spatiotemporal compression is decentralized and requires minimal feedback from the FC. Furthermore, the method does not require synchronized sensors and is robust to node failures, packet losses, and sensor noise. This approach is demonstrated on synthetic climate measurement data and seismic reflection data. Compared to a conventional time-division access without data compression, as well as to random access with CS but without temporal compression, the proposed method significantly improves energy and bandwidth efficiency. List of Figures 2.1 Four DSC encoding schemes [1]. (a) No Slepian-Wolf coding. (b) Sequential Slepian-Wolf.
Proceedings of the second workshop on Underwater networks - WuWNet '07, 2007
Spatial frequency reuse is considered for large area coverage in bandwidth-limited underwater aco... more Spatial frequency reuse is considered for large area coverage in bandwidth-limited underwater acoustic networks. The acoustic propagation laws-namely, the dependence of the path loss on both the distance and the frequency-lead to a set of constraints that the frequency reuse number N and the cell radius R must satisfy in order to constitute a valid solution for the network topology. For a required signal-to-interference ratio SIR0, and per-user bandwidth W0, the region of admissible solutions (R, N) depends on the desired user density ρ and the available bandwidth B. User capacity is defined as the maximal density ρmax that can be supported within a given bandwidth, and it is derived analytically. Numerical results illustrate the fact that capacity-achieving architectures are characterized by N that grows with ρmax. In a practical system, the bandwidth may be traded off for a smaller reuse number. The capacity is also shown to increase as the operational bandwidth is moved to higher frequencies. Although higher frequencies demand greater transmission power to span the same distance, they also imply a reduction in the cell size, which in turn provides an overall reduction in the transmission power. While complex relationships are involved in system optimization, the analysis presented offers a relatively simple tool for the design of autonomous underwater systems based on cellular network architectures.
Transactions on Emerging Telecommunications Technologies, 2012
We consider a hierarchical Q1 Q2 underwater acoustic sensor network architecture in which the sen... more We consider a hierarchical Q1 Q2 underwater acoustic sensor network architecture in which the sensors and the collector stations operate in distinct layers. The hierarchical architecture is motivated by the property of the acoustic underwater transmission medium that for each transmission distance, there exists an operating frequency for which the narrow-band signal-to-noise ratio is maximised. The sensors and the collector stations are consequently allocated different operating frequencies. We assume a uniform distribution of both sensors and collector stations over the finite area of the sensing field. The sensors are organised into clusters forming virtual transmit/receive arrays. The collector stations, on the other hand, are equipped with co-located transmit/receive arrays. We adopt a communication-theoretic approach and study the interdependence of the sustainable number of hops through the network, end-to-end frame error probability, power and bandwidth allocation. The analysis is performed under the assumption of Ricean fading and interference from other nodes within the same layer of the hierarchy. We present numerical examples that illustrate the network performance and demonstrate that there are preferred operating frequencies, which ensure network operation without any cross-interference between the collector network and the sensor network.
2010 IEEE International Conference on Communication Systems, 2010
We consider the performance of clustered underwater acoustic ad-hoc networks. We assume a uniform... more We consider the performance of clustered underwater acoustic ad-hoc networks. We assume a uniform distribution of nodes over a finite area. The nodes in the network form clusters. The information is transmitted across the network from cluster to cluster with nodes in each cluster organized as virtual transmit/receive arrays. The cluster-to-cluster channel is modeled as a Ricean fading channel. We adopt a communication theoretic approach and study the interdependence of the sustainable number of cluster-to-cluster hops through the network, end-toend frame error probability, power and bandwidth allocation. We assume an idealized scenario when there is no interference in the network. We present numerical examples that illustrate the results of the analysis. The results indicate that the network exhibits a bimodal behavior. For a given transmit power, bandwidth and cluster size, a certain minimum network density is required in order to guarantee full network connectivity.
2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers, 2010
Underwater acoustic (UWA) channels are typically characterized by a multipath structure with larg... more Underwater acoustic (UWA) channels are typically characterized by a multipath structure with large delay spread, where only a few propagation paths carry significant energy. Each path exhibits time variability, which, together with the transmitter and receiver motion, induces Doppler spreading and shifting of the signal. In this paper, we analyze the limits on the information rate achievable through multiple-input multipleoutput (MIMO) communications over UWA channels. Assuming full channel state information (CSI) at the receiver, we evaluate the ergodic capacity in two scenarios: one with partial CSI at the transmitter, and another with no CSI. Also, we consider the constrained capacity for practical modulations, e.g., BPSK and QPSK, and, exploiting the sparseness of the multipath structure, we provide new lower bounds on the achievable information rate. Statistical characterization and numerical examples are given based on the data collected in a recent experiment, conducted off the coast of Kauai, Hawaii, in June 2008.
Wireless Sensor Networks (WSNs) are used to monitor physical or environmental conditions, and to ... more Wireless Sensor Networks (WSNs) are used to monitor physical or environmental conditions, and to pass their data through the network to a central location. These networks have applications in diverse areas including environmental, health monitoring, home automation or military. The devices that form the network have limited resources, such as power and computational capacity. This thesis focus on the localization and tracking problem, presenting a method that can be used with objects that emit a signature signal. The localization step is performed using a mixed-norm minimization to retrieve a sparse vector with a discrete set of locations, whereas the tracking step is performed updating the amplitudes and locations explicitly by using a gradient descent algorithm. None of these methods rely on having the full set of measurements. Therefore, the network architecture is developed having in mind that the methods only use a subset of the measurements, with the objective of reducing the energy consumption of the system, which is one of the main challenges in designing a WSN. Focusing on the localization step, clustering algorithms are studied in order to improve the accuracy of the estimates. Concerning the tracking step, feedback of the estimated positions from the FC to the network is added. The feedback is used to instruct the sensors to increase/decrease their sampling rate, and, when mobile, to adjust their position. The goal in doing so is to improve both the energy efficiency of the system and the accuracy of the tracking. Additionally, a method to monitor the error in the tracking parameters is introduced. This method is used to restart the localization step when necessary.
Random Linear Packet Coding For Fading Channels
Random linear packet coding is considered for use over underwater acoustic channels where long de... more Random linear packet coding is considered for use over underwater acoustic channels where long delays challenge the efficiency of standard ARQ. Adaptive power control and rate control are explored to overcome the effect of fading, while minimizing the average energy per successfully transmitted bit of information. Two extreme scenarios are considered: independent fading where the channel varies independently from one data packet to the next, and block fading where the channel stays fixed over a block of packets. For the case of block fading, we design a power (rate) adaptation strategy under an outage criterion. We show that there exists an optimal transmission power (number of coded packets) for which the average energy per bit is minimized. Finally, we quantify the benefits of adaptive power (rate) control using real channel data recorded over a mobile link in the 10kHz acoustic band. These results show that energy savings are available from adaptive power (rate) control strategies.
Computationally Efficient Simulation of Underwater Acoustic Communication Systems
We propose a statistical model for underwater acoustic channel simulation which addresses acousti... more We propose a statistical model for underwater acoustic channel simulation which addresses acoustic propagation laws as well as fading. The fading effects are studied on small-scale (involving distances on the order of the wavelength) and large-scale (due to location uncertainty). These effects are caused by various phenomena such as scattering, system motion and changing environmental conditions, and result in the variation of the instantaneous channel response as well as the average signal to noise ratio. We compare the simulator with real underwater acoustic data obtained during the Kauai Acomms MURI (KAM'11) experiment which was held in July 2011. Simulated and experimental channels exhibit complex Gaussian path fading with a Bessel-type time-correlation on the small scale, and log-normal distribution with an exponentially decaying time-correlation on the large scale. MSE performance is compared for coherent and differentially coherent detection of experimental and simulated data.
This article considers the joint problem of packet scheduling and self-localization in an underwa... more This article considers the joint problem of packet scheduling and self-localization in an underwater acoustic sensor network where sensor nodes are distributed randomly in an operating area. In terms of packet scheduling, our goal is to minimize the localization time, and to do so we consider two packet transmission schemes, namely a collision-free scheme (CFS), and a collision-tolerant scheme (CTS). The required localization time is formulated for these schemes, and through analytical results and numerical examples their performances are shown to be generally comparable. However, when the packet duration is short (as is the case for a localization packet), and the operating area is large (above 3km in at least one dimension), the collision-tolerant scheme requires a smaller localization time than the collision-free scheme. After gathering enough measurements, an iterative Gauss-Newton algorithm is employed by each sensor node for self-localization, and the Cramér Rao lower bound is evaluated as a benchmark. Although CTS consumes more energy for packet transmission, it provides a better localization accuracy. Additionally, in this scheme the anchor nodes work independently of each other, and can operate asynchronously which leads to a simplified implementation.
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Papers by Milena Stojanovic