E. Erkip

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

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Publications (207)135.01 Total impact

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    ABSTRACT: In this paper, a cooperative multicast scheme that uses Randomized Distributed Space Time Codes (R-DSTC), along with packet level Forward Error Correction (FEC), is studied. Instead of sending source packets and/or parity packets through two hops using R-DSTC as proposed in our prior work, the new scheme delivers both source packets and parity packets using only one hop. After the source station (access point, AP) first sends all the source packets, the AP as well as all nodes that have received all source packets together send the parity packets using R-DSTC. As more parity packets are transmitted, more nodes can recover all source packets and join the parity packet transmission. The process continues until all nodes acknowledge the receipt of enough packets for recovering the source packets. For each given node distribution, the optimum transmission rates for source and parity packets are determined such that the video rate that can be sustained at all nodes is maximized. This new scheme can support significantly higher video rates, and correspondingly higher PSNR of decoded video, than the prior approaches. Three suboptimal approaches, which do not require full information about user distribution or the feedback, and hence are more feasible in practice are also presented. The proposed suboptimal scheme with only the node count information and without feedback still outperforms our prior approach that assumes full channel information and no feedback.
    01/2014;
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    ABSTRACT: Millimeter wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multi-element antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low power micro- or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures and carrier aggregation can be leveraged in the mmW context.
    Proceedings of the IEEE 01/2014; 102(3). · 6.91 Impact Factor
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    ABSTRACT: With the severe spectrum shortage in conventional cellular bands, millimeter wave (mmW) frequencies between 30 and 300 GHz have been attracting growing attention as a possible candidate for next-generation micro- and picocellular wireless networks. The mmW bands offer orders of magnitude greater spectrum than current cellular allocations and enable very high-dimensional antenna arrays for further gains via beamforming and spatial multiplexing. This paper uses recent real-world measurements at 28 and 73 GHz in New York City to derive detailed spatial statistical models of the channels and uses these models to provide a realistic assessment of mmW micro- and picocellular networks in a dense urban deployment. Statistical models are derived for key channel parameters including the path loss, number of spatial clusters, angular dispersion and blocking. It is found that, even in highly non-line-of-sight environments, strong signals can be detected 100m to 200m from potential cell sites, potentially with multiple clusters to support spatial multiplexing. Moreover, a system simulation based on the models predicts that mmW systems with cell radii of 100m can offer an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks with similar cell density.
    12/2013;
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    Oner Orhan, Deniz Gunduz, Elza Erkip
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    ABSTRACT: Communication over a broadband fading channel powered by an energy harvesting transmitter is studied. Assuming non-causal knowledge of energy/data arrivals and channel gains, optimal transmission schemes are identified by taking into account the energy cost of the processing circuitry as well as the transmission energy. A constant processing cost for each active sub-channel is assumed. Three different system objectives are considered: i) throughput maximization, in which the total amount of transmitted data by a deadline is maximized for a backlogged transmitter with a finite capacity battery; ii) energy maximization, in which the remaining energy in an infinite capacity battery by a deadline is maximized such that all the arriving data packets are delivered; iii) transmission completion time minimization, in which the delivery time of all the arriving data packets is minimized assuming infinite size battery. For each objective, a convex optimization problem is formulated, the properties of the optimal transmission policies are identified, and an algorithm which computes an optimal transmission policy is proposed. Finally, based on the insights gained from the offline optimizations, online algorithms for the throughput and energy maximization problems are developed under the assumption that the energy/data arrivals and channel states are known causally at the transmitter.
    11/2013;
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    ABSTRACT: In various wireless systems, such as sensor RFID networks and body area networks with implantable devices, the transmitted signals are simultaneously used both for information transmission and for energy transfer. In order to satisfy the conflicting requirements on information and energy transfer, this paper proposes the use of constrained run-length limited (RLL) codes in lieu of conventional unconstrained (i.e., random-like) capacity-achieving codes. The receiver's energy utilization requirements are modeled stochastically, and constraints are imposed on the probabilities of battery underflow and overflow at the receiver. It is demonstrated that the codewords' structure afforded by the use of constrained codes enables the transmission strategy to be better adjusted to the receiver's energy utilization pattern, as compared to classical unstructured codes. As a result, constrained codes allow a wider range of trade-offs between the rate of information transmission and the performance of energy transfer to be achieved.
    11/2013;
  • Source
    Forty-Seventh Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, USA; 11/2013
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    ABSTRACT: With the severe spectrum shortage in conventional cellular bands, millimeter wave (mmW) frequencies between 30 and 300 GHz have been attracting growing attention as a possible candidate for next-generation micro- and picocellular wireless networks. The mmW bands offer orders of magnitude greater spectrum than current cellular allocations and enable very high-dimensional antenna arrays for further gains via spatial multiplexing. However, the propagation of mmW signals in outdoor non line-of-sight (NLOS) links remains challenging and the feasibility of wide-area mmW cellular networks is far from clear. This paper uses recent real-world measurements at 28 GHz in New York City to provide a realistic assessment of mmW picocellular networks in a dense urban deployment. It is found that, even under conservative propagation assumptions, mmW systems with cell radii of 100m can offer an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks with similar cell density. However, it is also shown that such mmW networks may operate in a largely power-limited regime where the full spatial and bandwidth degrees of freedom are not fully utilized. This power-limited regime contrasts significantly with current bandwidth-limited cellular systems, requiring alternate technologies for mmW systems that may unlock further gains that mmW frequency bands offer.
    04/2013;
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    ABSTRACT: In this paper multi-antenna half-duplex and full-duplex relaying are compared from the perspective of achievable rates. Full-duplexing operation requires additional resources at the relay such as antennas and RF chains for self-interference cancellation. Using a practical model for the residual self-interference, full-duplex achievable rates and degrees of freedom are computed for the cases for which the relay has the same number of antennas or the same number of RF chains as in the half-duplex case, and compared with their half-duplex counterparts. It is shown that power scaling at the relay is necessary to maximize the the degrees of freedom in the full-duplex mode.
    03/2013;
  • Source
    Xi Liu, Elza Erkip
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    ABSTRACT: This work considers communication over Gaussian interference channels with processing energy cost, which explicitly takes into account the energy expended for processing when transmitters are on. In the presence of processing energy cost, transmitting all the time as in the conventional no-cost case is no longer optimal. For a two-user Gaussian interference channel with processing energy cost, assuming that the on-off states of transmitters are not utilized for signaling, several transmission schemes with varying complexities are proposed and their sum rates are compared with an interference-free upper bound. Moreover, the very strong interference regime, under which interference does not incur any rate penalty, is identified and shown to be larger than the case of no processing energy cost for certain scenarios of interest. Also, extensions to a three-user cascade Gaussian Z interference channel with processing energy cost are provided, where scheduling of user transmissions based on the channel set-up is investigated.
    IEEE Transactions on Wireless Communications 01/2013; · 2.42 Impact Factor
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    ABSTRACT: In this paper, a novel decentralized cross-layer multi-hop cooperative network architecture is proposed and presented. This cross-layer architecture introduces a new cooperative flooding scheme and two decentralized opportunistic cooperative forwarding mechanisms based on randomized coding, and a Routing Enabled Cooperative Medium Access Control (RECOMAC) protocol that enables cooperative forwarding, while incorporating physical, medium access control (MAC) and routing layers. RECOMAC employs randomized coding to realize cooperative diversity, so that relay selection and actuation mechanisms are alleviated and the MAC costs are reduced. The coded packets are routed in the network via the proposed cooperative forwarding schemes, which opportunistically form cooperative sets within a region, not needing a prior route to be established. Essentially, in the RECOMAC architecture, the routing layer functionality is submerged into the MAC layer to provide seamless cooperative communication, while the messaging overhead to set up routes, select and actuate relays is reduced. We evaluate the performance of RECOMAC in terms of network throughput, delay and MAC and routing overhead, in comparison to the conventional architecture based on the well-known IEEE 802.11 MAC and Ad hoc On Demand Distance Vector (AODV) routing protocols. RECOMAC is shown to provide quite significant improvement by an order of magnitude difference in all investigated performance metrics, under a variety of scenarios, considering different network sizes, static and mobile scenarios and networks with multiple flows.
    Computer Networks. 01/2013; 57(18):4010–4029.
  • O. Orhan, E. Erkip
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    ABSTRACT: In wireless networks, management of harvested energy is important due to limited and stochastic energy sources. In this paper, throughput maximization for energy harvesting two-hop communication with half-duplex relays is considered. Optimal transmission policies are found for one relay and two parallel relays under the assumption of known energy arrivals at the source and the relays. For each case, a convex optimization problem is formulated to efficiently solve and identify properties of the optimal transmission policies. Performance comparisons are provided to investigate the impact of multiple relays and energy harvesting.
    Information Theory Proceedings (ISIT), 2013 IEEE International Symposium on; 01/2013
  • O. Orhan, D. Gunduz, E. Erkip
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    ABSTRACT: Energy harvesting (EH) technology enables wireless nodes to operate in a self-powered fashion; however, the stochastic nature of the harvesting process and the limited amount of harvested energy require efficient management of the available resources. In this paper, an EH transmitter communicating over a fading channel is studied considering jointly the energy costs of transmission and processing. In particular, under the assumption of known energy and data arrival profiles and fading states, optimal transmission policies are studied, so that, the remaining energy in the battery of the transmitter is maximized by a given deadline while all the arriving data packets are delivered to the receiver. A "directional glue pouring" interpretation is provided for the algorithm that computes the optimal offline transmission policy. The relation of this problem with the transmission completion time minimization problem is also discussed. Finally, a heuristic algorithm for online optimization, which performs close to the optimal offline transmission policy, is proposed.
    Communications (ICC), 2013 IEEE International Conference on; 01/2013
  • O. Orhan, D. Gunduz, E. Erkip
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    ABSTRACT: Distortion minimization for an energy harvesting sensor node communicating over a fading channel is studied. Slotted transmission is considered such that, new source samples and energy packets arrive at the beginning of each time slot (TS), and the fading channel state changes from one TS to the next. A delay constraint is imposed requiring each source sample to be reconstructed at the destination d TSs after its arrival. Assuming independent Gaussian samples with variances changing over TSs, total distortion is minimized under the offline optimization framework, i.e., energy arrivals, source variances and channel gains are assumed to be known non-causally. Optimal compression rates and transmission powers are found and some properties of the optimal strategy are discussed. A two-dimensional water-filling interpretation of the optimal solution is provided for a battery-run node with d = 1.
    Information Theory Proceedings (ISIT), 2013 IEEE International Symposium on; 01/2013
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    ABSTRACT: Distributed space-time coding (DSTC) is a key physical (PHY) layer technique to enable cooperative relaying in wireless networks. Compared with direct transmission and single-relay cooperation, DSTC exploits spatial diversity gain and achieves a higher end-to-end throughput performance. In particular, a novel variation of DSTC, which is called randomized DSTC (R-DSTC), further enhances the performance of conventional DSTC in a mobile environment due to its decentralized relay recruitment. This paper presents a medium access control (MAC) protocol, which is called CoopMAX, for Worldwide Interoperability for Microwave Access (WiMAX) systems to provide cooperative relaying with DSTC and R-DSTC techniques by the use of fixed and mobile relays. CoopMAX explores a joint PHY layer and MAC layer optimization for rate adaptation. The efficiency of CoopMAX is investigated, showing pronounced advantages, such as a doubling of throughput as compared with conventional WiMAX protocols in some typical scenarios.
    IEEE Transactions on Vehicular Technology 01/2013; 62(3):1399-1405. · 2.06 Impact Factor
  • Yuanpeng Liu, E. Erkip
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    ABSTRACT: In this paper, a class of Gaussian broadcast interference channels is investigated, where one of the two broadcast users is subject to the interference coming from a point-to-point transmission. Channel parameters are categorized into three regimes. For the first two, where an ordering of the decodability of the broadcast users exists, inner bounds based on superposition and rate splitting are obtained. Entropy-power-inequality-based outer bounds are derived by combining bounding techniques for Gaussian broadcast and interference channels. These inner and outer bounds lead to either exact or approximate characterizations of the capacity region and sum capacity under various conditions. For the remaining complementing regime, inner and outer bounds are also provided.
    Information Theory Proceedings (ISIT), 2013 IEEE International Symposium on; 01/2013
  • Source
    Oner Orhan, Deniz Gündüz, Elza Erkip
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    ABSTRACT: In wireless networks, energy consumed for communication includes both the transmission and the processing energy. In this paper, point-to-point communication over a fading channel with an energy harvesting transmitter is studied considering jointly the energy costs of transmission and processing. Under the assumption of known energy arrival and fading profiles, optimal transmission policy for throughput maximization is investigated. Assuming that the transmitter has sufficient amount of data in its buffer at the beginning of the transmission period, the average throughput by a given deadline is maximized. Furthermore, a "directional glue pouring algorithm" that computes the optimal transmission policy is described.
    08/2012;
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    Yuanpeng Liu, Elza Erkip
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    ABSTRACT: We study a class of discrete memoryless broadcast interference channels (DM-BICs), where one of the broadcast receivers is subject to the interference from a point-to-point transmission. A general achievable rate region $\mathcal{R}$ based on rate splitting, superposition coding and binning at the broadcast transmitter and rate splitting at the interfering transmitter is derived. Under two partial order broadcast conditions {\em interference-oblivious less noisy} and {\em interference-cognizant less noisy}, a reduced form of $\mathcal{R}$ is shown to be equivalent to the region based on a simpler scheme that uses only superposition coding at the broadcast transmitter. Furthermore, the capacity regions of DM-BIC under the two partial order broadcast conditions are characterized respectively for the strong and very strong interference conditions.
    06/2012;
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    Xi Liu, Osvaldo Simeone, Elza Erkip
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    ABSTRACT: This paper considers the problem of lossy compression for the computation of a function of two correlated sources, both of which are observed at the encoder. Due to presence of observation costs, the encoder is allowed to observe only subsets of the samples from both sources, with a fraction of such sample pairs possibly overlapping. The rate-distortion function is characterized for memory-less sources, and then specialized to Gaussian and binary sources for selected functions and with quadratic and Hamming distortion metrics, respectively. The optimal measurement overlap fraction is shown to depend on the function to be computed by the decoder, on the source statistics, including the correlation, and on the link rate. Special cases are discussed in which the optimal overlap fraction is the maximum or minimum possible value given the sampling budget, illustrating non-trivial performance trade-offs in the design of the sampling strategy. Finally, the analysis is extended to the multi-hop set-up with jointly Gaussian sources, where each encoder can observe only one of the sources.
    IEEE Transactions on Communications 06/2012; · 1.75 Impact Factor
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    ABSTRACT: Two-way real-time video communication in wireless networks requires high bandwidth, low delay and error resiliency. This paper addresses these demands by proposing a system with the integration of Network Coding (NC), user cooperation using Randomized Distributed Space-time Coding (R-DSTC) and packet level Forward Error Correction (FEC) under a one-way delay constraint. Simulation results show that the proposed scheme significantly outperforms both conventional direct transmission as well as R-DSTC based two-way cooperative transmission, and is most effective when the distance between the users is large.
    05/2012;
  • Source
    Oner Orhan, Elza Erkip
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    ABSTRACT: In this paper, a two-hop communication system with energy harvesting nodes is considered. Unlike battery powered wireless nodes, both the source and the relay are able to harvest energy from environment during communication, therefore, both data and energy causality over the two hops need to be considered. Assuming both nodes know the harvested energies in advance, properties of optimal transmission policies to maximize the delivered data by a given deadline are identified. Using these properties, optimal power allocation and transmission schedule for the case in which both nodes harvest two energy packets is developed.
    02/2012;

Publication Stats

6k Citations
135.01 Total Impact Points

Institutions

  • 2006–2013
    • Polytechnic Institute of New York University
      • Department of Electrical and Computer Engineering
      Brooklyn, New York, United States
  • 2009–2011
    • New Jersey Institute of Technology
      • Department of Electrical and Computer Engineering
      Newark, NJ, United States
  • 2010
    • CTTC Catalan Telecommunications Technology Centre
      Barcino, Catalonia, Spain
  • 2009–2010
    • TOBB University of Economics and Technology
      • Department of Electrical and Electronics Engineering
      Engüri, Ankara, Turkey
  • 2008–2010
    • University of Naples Federico II
      Napoli, Campania, Italy
    • Worcester State University
      Worcester, Massachusetts, United States
  • 2008–2009
    • Princeton University
      • Department of Electrical Engineering
      Princeton, NJ, United States
  • 2005–2009
    • CUNY Graduate Center
      New York City, New York, United States
  • 2007
    • University of California, Riverside
      • Department of Electrical Engineering
      Riverside, CA, United States
    • Alcatel Lucent
      Lutetia Parisorum, Île-de-France, France
  • 2005–2007
    • Brooklyn Research
      New York City, New York, United States
  • 2003–2007
    • Qualcomm
      San Diego, California, United States
    • Southern Methodist University
      • Department of Electrical Engineering
      Dallas, TX, United States
  • 1995–2007
    • Stanford University
      • • Department of Electrical Engineering
      • • Information Systems Laboratory
      Palo Alto, California, United States
  • 2004
    • City University of New York - Brooklyn College
      Brooklyn, New York, United States
  • 1997–2002
    • Rice University
      • Department of Electrical and Computer Engineering
      Houston, TX, United States