Elza Erkip

Polytechnic Institute of New York University, Brooklyn, New York, United States

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Publications (244)

  • Poster · Oct 2016
  • [Show abstract] [Hide abstract] ABSTRACT: The resource usage model for millimeter wave bands has been the subject of considerable debate. The massive band- width, highly directional antennas, high penetration loss and susceptibility to shadowing in these bands suggest certain advantages to spectrum and infrastructure sharing. In partic- ular, resources that are \open", such as unlicensed spectrum or a deployment of base stations open to all service providers, may o�er greater gains in mmWave bands than at conven- tional cellular frequencies. However, even when sharing is technically bene�cial (as recent research in this area suggests that it is), it may not be pro�table. In this paper, both the technical and economic implications of resource sharing in millimeter wave networks are studied. Millimeter wave service is considered in the economic framework of a network good, where consumers' utility depends on the network size. Detailed network simulations are used to understand data rates, pro�t, and demand for millimeter wave service, with and without open resources. The results suggest that \open" deployments of neutral small cells that serve subscribers of any service provider encourage market entry by making it easier for networks to reach critical mass, more than \open" (unlicensed) spectrum would.
    Conference Paper · Oct 2016
  • Conference Paper · Sep 2016
  • Roghayeh Joda · Farshad Lahouti · Elza Erkip
    [Show abstract] [Hide abstract] ABSTRACT: This paper investigates distortion-power tradeoffs in transmission of quasi-stationary sources over delay and buffer limited block fading channels by studying encoder and decoder buffering techniques to smooth out the source and channel variations. Four source and channel coding schemes that consider buffer and power constraints are presented to minimize the reconstructed source distortion. The first one is a high performance scheme, which benefits from optimized source and channel rate adaptation. In the second scheme, the channel coding rate is fixed and optimized along with transmission power with respect to channel and source variations; hence this scheme enjoys simplicity of implementation. The two last schemes have fixed transmission power with optimized adaptive or fixed channel coding rate. For all the proposed schemes, closed form solutions for mean distortion, optimized rate, and power are provided and in the high SNR regime, the mean distortion exponent and the asymptotic mean power gains are derived. The proposed schemes with buffering exploit the diversity due to source and channel variations. Specifically, when the buffer size is limited, fixed channel rate adaptive power scheme outperforms an adaptive rate fixed power scheme. Furthermore, analytical and numerical results demonstrate that with limited buffer size, the system performance in terms of reconstructed signal SNR saturates as transmission power increases, suggesting that appropriate buffer size selection is important to achieve a desired reconstruction quality.
    Article · Jul 2016 · IEEE Transactions on Wireless Communications
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: The rate-distortion dimension (RDD) of an analog stationary process is studied as a measure of complexity that captures the amount of information contained in the process. It is shown that the RDD of a process, defined as two times the asymptotic ratio of its rate-distortion function $R(D)$ to $\log {1\over D}$ as the distortion $D$ approaches zero, is equal to its information dimension (ID). This generalizes an earlier result by Kawabata and Dembo and provides an operational approach to evaluate the ID of a process, which previously was shown to be closely related to the effective dimension of the underlying process and also to the fundamental limits of compressed sensing. The relation between RDD and ID is illustrated for a piecewise constant process.
    Full-text available · Conference Paper · Jul 2016
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: The licensing model for millimeter wave bands has been the subject of considerable debate, with some industry players advocating for unlicensed use and others for traditional geographic area exclusive use licenses. Meanwhile, the massive bandwidth, highly directional antennas, high penetration loss and susceptibility to shadowing in these bands suggest certain advantages to spectrum and infrastructure sharing. However, even when sharing is technically beneficial (as recent research in this area suggests that it is), it may not be profitable. In this paper, both the technical and economic implications of resource sharing in millimeter wave networks are studied. Millimeter wave service is considered in the economic framework of a network good, where consumers' utility depends on the size of the network, and the strategic decisions of consumers and service providers are connected to detailed network simulations. The results suggest that "open" deployments of neutral small cells that serve subscribers of any service provider encourage market entry by making it easier for networks to reach critical mass, more than "open" (unlicensed) spectrum would. The conditions under which competitive service providers would prefer to share resources or not are also described.
    Full-text available · Article · May 2016
  • [Show abstract] [Hide abstract] ABSTRACT: In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop and two way two hop communication are compared in terms of degrees of freedom (DoF) and achievable rate, under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario, and achievable rates are computed at finite SNR levels for HD, antenna conserved (AC) and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, AC FD performs strictly below HD with imperfect SI cancellation, and RC FD DoF trade-off is superior, when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, HD is generally better than FD; for asymmetric traffic, FD can achieve better rate pairs than HD, provided the relay has sufficient number of antennas and SI suppression. Computed achievable rates for each scenario indicate that DoF results also extend to finite SNR.
    Article · Apr 2016
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Motivated by the intrinsic characteristics of mmWave technologies, we discuss the possibility of an authorization regime that allows spectrum sharing between multiple operators, also referred to as spectrum pooling. In particular, considering user rate as the performance measure, we assess the benefit of coordination among the networks of different operators, study the impact of beamforming both at the base stations and at the user terminals, and analyze the pooling performance at different frequency carriers. We also discuss the enabling spectrum mechanisms, architectures, and protocols required to make spectrum pooling work in real networks. Our initial results show that, from a technical perspective, spectrum pooling at mmWave has the potential for a more efficient spectrum use than a traditional exclusive spectrum allocation to a single operator. However, further studies are needed in order to reach a thorough understanding of this matter, and we hope that this paper will help stimulate further research in this area.
    Full-text available · Article · Mar 2016 · IEEE Communications Magazine
  • Efe Onaran · Siddharth Garg · Elza Erkip
    [Show abstract] [Hide abstract] ABSTRACT: Anonymized social network graphs published for academic or advertisement purposes are subject to de-anonymization attacks by leveraging side information in the form of a second, public social network graph correlated with the anonymized graph. This is because the two are from the same underlying graph of true social relationships. In this paper, we (i) characterize the maximum a posteriori (MAP) estimates of user identities for the anonymized graph and (ii) provide sufficient conditions for successful de-anonymization for underlying graphs with community structure. Our results generalize prior work that assumed underlying graphs of Erd\H{o}s-R\'enyi type, in addition to proving the optimality of the attack strategy adopted in the prior work.
    Article · Feb 2016
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Modern compression algorithms exploit complex structures that are present in signals to describe them very efficiently. On the other hand, the field of compressed sensing is built upon the observation that "structured" signals can be recovered from their under-determined set of linear projections. Currently, there is a large gap between the complexity of the structures studied in the area of compressed sensing and those employed by the state-of-the-art compression codes. Recent results in the literature on deterministic signals aim at bridging this gap through devising compressed sensing decoders that employ compression codes. This paper focuses on structured stochastic processes and studies the application of rate-distortion codes to compressed sensing of such signals. The performance of the formerly-proposed compressible signal pursuit (CSP) algorithm is studied in this stochastic setting. It is proved that in the very low distortion regime, as the blocklength grows to infinity, the CSP algorithm reliably and robustly recovers $n$ instances of a stationary process from random linear projections as long as their count is slightly more than $n$ times the rate-distortion dimension (RDD) of the source. It is also shown that under some regularity conditions, the RDD of a stationary process is equal to its information dimension (ID). This connection establishes the optimality of the CSP algorithm at least for memoryless stationary sources, for which the fundamental limits are known. Finally, it is shown that the CSP algorithm combined by a family of universal variable-length fixed-distortion compression codes yields a family of universal compressed sensing recovery algorithms.
    Full-text available · Article · Jan 2016
  • Yuanpeng Liu · Elza Erkip
    [Show abstract] [Hide abstract] ABSTRACT: In this paper, a class of broadcast interference channels (BIC) is investigated, where one of the two broadcast receivers is subject to interference coming from a point-to-point transmission. For a general discrete memoryless broadcast interference channel (DM-BIC), an achievable scheme based on message splitting, superposition and binning is proposed and a concise representation of the corresponding achievable rate region R is obtained. Two partial-order broadcast conditions interference-oblivious less noisy and interference-cognizant less noisy are defined, thereby extending the usual less noisy condition for a regular broadcast channel by taking interference into account. Under these conditions, a reduced form of R is shown to be equivalent to a rate region based on a simpler scheme, where the broadcast transmitter uses only superposition. Furthermore, if interference is strong for the interference-oblivious less noisy DM-BIC, the capacity region is given by the aforementioned two equivalent rate regions. For a Gaussian broadcast interference channel (GBIC), channel parameters are categorized into three regimes. For the first two regimes, which are closely related to the two partial-order broadcast conditions, achievable rate regions are derived by specializing the corresponding achievable schemes of DM-BICs with Gaussian input distributions. The entropy power inequality (EPI) based outer bounds are obtained by combining bounding techniques for a Gaussian broadcast channel (GBC) and a Gaussian interference channel (GIC). These inner and outer bounds lead to either exact or approximate characterizations of capacity regions and sum capacity under various conditions. For the remaining complementing regime, inner and outer bounds are also provided.
    Article · Aug 2015 · IEEE Transactions on Information Theory
  • Yuanpeng Liu · Elza Erkip
    [Show abstract] [Hide abstract] ABSTRACT: In a two-user channel, completion time refers to the number of channel uses spent by each user to transmit a bit pool with some given size. In this paper, the information-theoretic formulation of completion time is based on the concept of constrained rates, where users are allowed to employ different numbers of channel uses for transmission as opposed to the equal channel use of the standard information-theoretic formulation. Analogous to the capacity region, the completion time region characterizes all possible trade-offs among users' completion times. For a multi-access channel, it is shown that the completion time region is achieved by operating the channel in two independent phases: a multi-access phase when both users are transmitting, and a point-to-point phase when one user has finished and the other is still transmitting. Using a similar two-phase approach, the completion time region (or inner and outer bounds) is established for a Gaussian broadcast channel and a Gaussian interference channel. It is observed that although consisting of two convex subregions, the completion time region may not be convex in general. Finally an optimization problem of minimizing the weighted sum completion time for a Gaussian multi-access channel and a Gaussian broadcast channel is solved, demonstrating the utility of the completion time approach.
    Article · Aug 2015
  • Oner Orhan · Elza Erkip
    [Show abstract] [Hide abstract] ABSTRACT: Energy harvesting multi-hop networks allow for perpetual operation of low cost, limited range wireless devices. Compared with their battery operated counterparts, the coupling of energy and data causality constraints with half duplex relay operation makes it challenging to operate such networks. In this paper, a throughput maximization problem for energy harvesting two-hop networks with decode-and-forward half-duplex relays is investigated. For a system with two parallel relays, various combinations of the following four transmission modes are considered: Broadcast from the source, multi-access from the relays, and successive relaying phases I and II. Optimal transmission policies for one and two parallel relays are studied under the assumption of non-causal knowledge of energy arrivals and finite size relay data buffers. The problem is formulated using a convex optimization framework, which allows for efficient numerical solutions and helps identify important properties of optimal policies. Numerical results are presented to provide throughput comparisons and to investigate the impact of multiple relays, size of relay data buffers, transmission modes, and energy harvesting on the throughput.
    Article · Jul 2015 · IEEE Journal on Selected Areas in Communications
  • Roghayeh Joda · Elza Erkip · Farshad Lahouti
    [Show abstract] [Hide abstract] ABSTRACT: In this paper, the problem of lossy source coding with side information at the decoder is considered when the dependency between the source and the side information (SI) is quasi-stationary and unknown to the encoder. This dependency is modeled using a (virtual) block fading channel. In order to help the decoder estimate the dependency, a part of the transmitted source in each block is coded at high rate (disregarding the SI) to be decoded error-free at the decoder. The estimate of the virtual block fading channel is imperfect and its quality depends on the length of the estimation block. The decoder's estimate is then quantized and communicated back to the encoder using a limited rate feedback. The encoder encodes the rest of the source block with this knowledge of the SI dependency model. A source coding scheme that uses the estimated dependency structure is proposed and the appropriate length of the source assigned for the estimation phase is characterized so as to minimize the mean distortion. The effect of the feedback rate, the quantization step size and the dependency estimation error are also investigated.
    Article · Jun 2015
  • Mainak Chowdhury · Alexandros Manolakos · Felipe Gomez-Cuba · [...] · Andrea J. Goldsmith
    [Show abstract] [Hide abstract] ABSTRACT: This paper studies noncoherent wideband systems with a single antenna transmitter and a multiple antenna receiver with many elements, under signaling with peak-to-average power ratio constraints. The analysis considers the scaling behavior of capacity and achievable rates by letting both the number of antennas and the bandwidth go to infinity jointly. In contrast to prior work on wideband single input single output (SISO) channels without a-priori channel state information, it is shown that a sufficiently large number of receive antennas can make up for the vanishingly small SNR at each antenna. In particular, it is shown that when bandwidth grows sufficiently slowly with the number of antennas, the capacity scaling with an increasing number of receive antennas is the same as the optimal coherent capacity scaling. If the bandwidth grows faster than a certain threshold, however, the additional bandwidth does not help because a finite transmit power is spread over an excessively large bandwidth.
    Article · Jun 2015
  • Felipe Gomez-Cuba · Jinfeng Du · Muriel Medard · Elza Erkip
    Conference Paper · Jun 2015
  • Source
    Roghayeh Joda · Farshad Lahouti · Elza Erkip
    [Show abstract] [Hide abstract] ABSTRACT: This paper investigates delay-distortion-power trade offs in transmission of quasi-stationary sources over block fading channels by studying encoder and decoder buffering techniques to smooth out the source and channel variations. Four source and channel coding schemes that consider buffer and power constraints are presented to minimize the reconstructed source distortion. The first one is a high performance scheme, which benefits from optimized source and channel rate adaptation. In the second scheme, the channel coding rate is fixed and optimized along with transmission power with respect to channel and source variations; hence this scheme enjoys simplicity of implementation. The two last schemes have fixed transmission power with optimized adaptive or fixed channel coding rate. For all the proposed schemes, closed form solutions for mean distortion, optimized rate and power are provided and in the high SNR regime, the mean distortion exponent and the asymptotic mean power gains are derived. The proposed schemes with buffering exploit the diversity due to source and channel variations. Specifically, when the buffer size is limited, fixed channel rate adaptive power scheme outperforms an adaptive rate fixed power scheme. Furthermore, analytical and numerical results demonstrate that with limited buffer size, the system performance in terms of reconstructed signal SNR saturates as transmission power is increased, suggesting that appropriate buffer size selection is important to achieve a desired reconstruction quality.
    Full-text available · Article · May 2015
  • Roghayeh Joda · Elza Erkip · Farshad Lahouti
    [Show abstract] [Hide abstract] ABSTRACT: In this paper, the problem of lossy source coding with side information at the decoder is considered when the dependency between the source and the side information (SI) is quasi-stationary and unknown to the encoder. This dependency is modeled using a (virtual) block fading channel. In order to help the decoder estimate the dependency, a part of the transmitted source in each block is coded at high rate (disregarding the SI) to be decoded error-free at the decoder. The estimate of the virtual block fading channel is imperfect and its quality depends on the length of the estimation block. The decoder's estimate is then quantized and communicated back to the encoder using a limited rate feedback. The encoder encodes the rest of the source block with this knowledge of the SI dependency model. A source coding scheme that uses the estimated dependency structure is proposed and the appropriate length of the source assigned for the estimation phase is characterized so as to minimize the mean distortion. The effect of the feedback rate, the quantization step size and the dependency estimation error are also investigated.
    Conference Paper · May 2015
  • Sennur Ulukus · Elza Erkip · Pulkit Grover · [...] · Michele Zorzi
    [Show abstract] [Hide abstract] ABSTRACT: The papers in this special issue presents cutting-edge research results in the emerging area of energy harvesting wireless communications and wireless energy transfer. This first issue starts with a review article coauthored by the guest editors that summarizes recent results in the broad area of energy harvesting communications, in particular, in information-theoretic, offline and online schedulingtheoretic, medium access, networking approaches to energy harvesting communications, as well as in energy cooperation and simultaneous wireless energy and information transfer.
    Article · Mar 2015 · IEEE Journal on Selected Areas in Communications
  • Source
    Oner Orhan · Elza Erkip · Sundeep Rangan
    [Show abstract] [Hide abstract] ABSTRACT: The wide bandwidth and large number of antennas used in millimeter wave systems put a heavy burden on the power consumption at the receiver. In this paper, using an additive quantization noise model, the effect of analog-digital conversion (ADC) resolution and bandwidth on the achievable rate is investigated for a multi-antenna system under a receiver power constraint. Two receiver architectures, analog and digital combining, are compared in terms of performance. Results demonstrate that: (i) For both analog and digital combining, there is a maximum bandwidth beyond which the achievable rate decreases; (ii) Depending on the operating regime of the system, analog combiner may have higher rate but digital combining uses less bandwidth when only ADC power consumption is considered, (iii) digital combining may have higher rate when power consumption of all the components in the receiver front-end are taken into account.
    Full-text available · Article · Feb 2015

Publication Stats

15k Citations

Institutions

  • 2010-2013
    • Polytechnic Institute of New York University
      • Department of Electrical and Computer Engineering
      Brooklyn, New York, United States
    • CTTC Catalan Telecommunications Technology Centre
      Barcino, Catalonia, Spain
  • 2009
    • New Jersey Institute of Technology
      • Department of Electrical and Computer Engineering
      Newark, NJ, United States
  • 2007-2009
    • Princeton University
      • Department of Electrical Engineering
      Princeton, NJ, United States
  • 2008
    • University of Naples Federico II
      Napoli, Campania, Italy
  • 1995-2007
    • Stanford University
      • • Department of Electrical Engineering
      • • Information Systems Laboratory
      Palo Alto, California, United States
  • 2005
    • CUNY Graduate Center
      New York City, New York, United States
  • 2003-2004
    • Virginia State University
      Петербург, Virginia, United States
  • 1997-2002
    • Rice University
      • Department of Electrical and Computer Engineering
      Houston, TX, United States