Publications
374 results found
Isikman AO, Yuksel M, Gunduz D, 2016, A Low-complexity policy for outage probability minimization with an energy harvesting transmitter, IEEE Communications Letters, Vol: 21, Pages: 917-920, ISSN: 1558-2558
Outage probability in an energy harvesting(EH) block-fading communication system is studied in thefinite-horizon online setting. First, the offline version ofthe problem is considered, and formulated as a mixedinteger linear program (MILP). Then, the infinite-horizononline problem (IIL) is considered relaxing the batteryconstraints. Solutions of these two problems provide lowerbounds on the finite-horizon online problem, for which weprovide a low-complexity heuristic scheme, called the fixedthreshold transmission (FTT) scheme. Numerical resultsshow that the FTT scheme achieves an outage performanceclose to the MILP lower bound for a wide range ofoperation regimes, and close to IIL when the EH rate islow. It is also observed that the power allocated by the FTTscheme resembles the optimal offline solution with highprobability, despite the lack of information about futurechannel states and energy arrivals.
Koken E, Gunduz D, Tuncel E, 2016, Energy-distortion exponents in lossy transmission of Gaussian sources over Gaussian channels, IEEE Transactions on Information Theory, Vol: 63, Pages: 1227-1236, ISSN: 1557-9654
Lossy transmission of Gaussian sources over energy limited Gaussian point-to-point and broadcast channels is studied under the infinite bandwidth regime, i.e., when the number of channel uses is unlimited. Using previously known asymptotic achievability and converse results, the energy-distortion exponent, defined as the rate of decay of the square-error distortion as the available energy-to-noise ratio increases without bound, is completely characterized for both the point-to-point and broadcast channel cases. Turning then to the scenario of zero delay transmission, where outage events with arbitrarily small probability are allowed, it is shown that the same energyd istortion exponent as in the infinite-delay case can be achieved in all the studied scenarios.
Varasteh M, Rassouli B, Gunduz D, et al., 2016, Zero-delay joint source-channel coding with a one-bit ADC front end and receiver side information, IEEE Information Theory Workshop, Publisher: IEEE
Zero-delay transmission of a Gaussian source over an additive white Gaussian noise (AWGN) channel with a 1-bit analog-to-digital converter (ADC) front end is investigated in the presence of correlated side information at the receiver. The design of the optimal encoder is considered for the mean squared error (MSE) distortion criterion under an average power constraint on the channel input. A necessary condition for the optimality of the encoder is derived. A numerically optimized encoder (NOE) is then obtained that aims that enforcing the necessary condition. It is observed that, due to the availability of receiver side information, the optimal encoder mapping is periodic, with its period depending on the correlation coefficient between the source and the side information. We then propose two parameterized encoder mappings, referred to as periodic linear transmission (PLT) and periodic BPSK transmission (PBT), which trade-off optimality for reduced complexity as compared to the NOE solution. We observe via numerical results that PBT performs close to the NOE in the high signal-to-noise ratio (SNR) regime, while PLT approaches the NOE performance in the low SNR regime.
Mohammadi Amiri M, Yang, gunduz, 2016, Coded caching for a large number of users, Information Theory Workshop (ITW), Publisher: IEEE
We consider the coded caching problem with a central server containing N files, each of length F bits, and K users, each equipped with a cache of capacity MF bits. We assume that coded contents can be proactively placed into users' caches at no cost during the placement phase. During the delivery phase, each user requests exactly one file from the database, and all the requests are served simultaneously by the server over an error-free common link. The goal is to utilize the local cache memories at the users to reduce the delivery rate from the server during the peak period. Here, we focus on a system which has more users than files, i.e., K > N. We first consider the centralized caching problem, in which the number and identity of active users are known in advance, and propose a group-based coded caching scheme for M = N/K, which improves upon the best achievable scheme in the literature. The proposed centralized caching scheme is then exploited in a decentralized setting, in which neither the number nor the identity of the active users are known during the placement phase. It is shown that the proposed coded caching scheme improves upon the best known decentralized delivery rate as well.
Abad MSH, Gunduz D, Ercetin O, 2016, Energy harvesting wireless networks with correlated energy sources, IEEE Wireless Communications and Networking Conference (WCNC), Publisher: IEEE, ISSN: 1525-3511
This work considers a system with two energy harvesting (EH) nodes transmitting to a common destination over a random access channel. The amount of harvested energy is assumed to be random and independent over time, but correlated among the nodes possibly with respect to their relative position. A threshold-based transmission policy is developed for the maximization of the expected aggregate network throughput. Assuming that there is no a priori channel state or EH information available to the nodes, the aggregate network throughput is obtained. The optimal thresholds are determined for two practically important special cases: i) at any time only one of the sensors harvests energy due to, for example, physical separation of the nodes; ii) the nodes are spatially close, and at any time, either both nodes or none of them harvests energy.
Giaconi G, Gunduz D, 2016, Smart meter privacy with renewable energy and a finite capacity battery, 17th IEEE International Workshop on Signal Processing Advances in Wireless Communications, Publisher: IEEE
We address the smart meter (SM) privacy problem by considering the availability of a renewable energy source (RES) and a battery which can be exploited by a consumer to partially hide the consumption pattern from the utility provider (UP). Privacy is measured by the mutual information rate between the consumer's energy consumption and the renewable energy generation process, and the energy received from the grid, where the latter is known by the UP through the SM readings, and the former two are to be kept private. By expressing the information leakage as an additive quantity, we cast the problem as a stochastic control problem, and formulate the corresponding Bellman equations.
Murin Y, Kaspi Y, Dabora R, et al., 2016, Energy-distortion tradeoff for the gaussian broadcast channel with feedback, IEEE International Symposium on Information Theory (ISIT), Publisher: IEEE, Pages: 1829-1833, ISSN: 2157-8117
This work focuses on the minimum transmission energy required for communicating a pair of correlated Gaussian sources over a two-user Gaussian broadcast channel with noiseless and causal channel output feedback (GBCF). We study the fundamental limit on the required transmission energy for broadcasting a pair of source samples, such that each source can be reconstructed at its respective receiver to within a target distortion, when the source-channel bandwidth ratio is not restricted. We derive a lower bound and three distinct upper bounds on the minimum required energy. For the upper bounds we analyze three transmission schemes: Two schemes are based on separate source-channel coding, and apply coding over multiple samples of source pairs. The third scheme is based on joint source-channel coding obtained by extending the Ozarow-Leung (OL) transmission scheme, which applies uncoded linear transmission. Numerical simulations show that despite its simplicity, the energy-distortion tradeoff of the OL-based scheme is close to that of the better separation-based scheme, which indicates that the OL scheme is attractive for energy-efficient source transmission over GBCFs.
Yang Q, Gunduz D, 2016, Centralized coded caching for heterogeneous lossy requests, IEEE International Symposium on Information Theory (ISIT), Publisher: IEEE, Pages: 405-409, ISSN: 2157-8117
Centralized coded caching of popular contents is studied for users with heterogeneous distortion requirements, corresponding to diverse processing and display capabilities of mobile devices. Users' distortion requirements are assumed to be fixed and known, while their particular demands are revealed only after the placement phase. Modeling each file in the database as an independent and identically distributed Gaussian vector, the minimum delivery rate that can satisfy any demand combination within the corresponding distortion target is studied. The optimal delivery rate is characterized for the special case of two users and two files for any pair of distortion requirements. For the general setting with multiple users and files, a layered caching and delivery scheme, which exploits the successive refinability of Gaussian sources, is proposed. This scheme caches each content in multiple layers, and it is optimized by solving two subproblems: lossless caching of each layer with heterogeneous cache capacities, and allocation of available caches among layers. The delivery rate minimization problem for each layer is solved numerically, while two schemes, called the proportional cache allocation (PCA) and ordered cache allocation (OCA), are proposed for cache allocation. These schemes are compared with each other and the cut-set bound through numerical simulations.
Guler B, Gunduz D, Yener A, 2016, On lossy transmission of correlated sources over a multiple access channel, IEEE International Symposium on Information Theory (ISIT), Publisher: IEEE, Pages: 2009-2013, ISSN: 2157-8117
We study lossy communication of correlated sources over a multiple access channel. In particular, we provide a joint source-channel coding scheme for transmitting correlated sources with decoder side information, and study the conditions under which separate source and channel coding is optimal. For the latter, the encoders and/or the decoder have access to a common observation conditioned on which the two sources are independent. By establishing necessary and sufficient conditions, we show the optimality of separation when the encoders and the decoder both have access to the common observation. We also demonstrate that separation is optimal when only the encoders have access to the common observation whose lossless recovery is required at the decoder. As a special case, we study separation for sources with a common part. Our results indicate that side information can have significant impact on the optimality of source-channel separation in lossy transmission.
Varasteh M, Gunduz, Osvaldo Simeone, 2016, Joint source-channel coding with one-bit ADC front end, 2016 IEEE International Symposium on Information Theory
This paper considers the zero-delay transmission of aGaussian source over an additive white Gaussian noise (AWGN)channel with a one-bit analog-to-digital converter (ADC) frontend. The optimization of the encoder and decoder is tackledunder both the mean squared error (MSE) distortion and theoutage distortion criteria with an average power constraint. ForMSE distortion, the optimal transceiver is identified over thespace of symmetric encoders. This result demonstrates that thelinear encoder, which is optimal with a full-precision front end,approaches optimality only in the low signal-to-noise ratio (SNR)regime; while, digital transmission is optimal in the high SNRregime. For the outage distortion criterion, the structure of theoptimal encoder and decoder are obtained. In particular, it isshown that the encoder mapping is piecewise constant and cantake only two opposite values when it is non-zero.Index Terms-Joint source channel coding, zero-delay transmis-sion, average distortion, outage distortion, one-bit ADC.
Tan O, Gunduz D, Gomez-Vilardebo J, 2016, Linear Transmission of Composite Gaussian Measurements over a Fading Channel under Delay Constraints, IEEE Transactions on Wireless Communications, Vol: 15, Pages: 4335-4347, ISSN: 1536-1276
Delay constrained linear transmission (LT) strategiesare considered for the transmission of composite Gaussianmeasurements over an additive white Gaussian noise fadingchannel under an average power constraint. If the channel stateinformation (CSI) is known by both the encoder and decoder,the optimal LT scheme in terms of the average mean-squareerror distortion is characterized under a strict delay constraint,and a graphical interpretation of the optimal power allocationstrategy is presented. Then, for general delay constraints, twoLT strategies are proposed based on the solution to a particularmultiple measurements-parallel channels scenario. It isshown that the distortion decreases as the delay constraint isrelaxed, and when the delay constraint is completely removed,both strategies achieve the optimal performance under certainmatching conditions. If the CSI is known only by the decoder, theoptimal LT strategy is derived under a strict delay constraint.The extension to general delay constraints is elusive. As a firststep towards understanding the structure of the optimal schemein this case, it is shown that for the multiple measurementsparallelchannels scenario, any LT scheme that uses only a oneto-onelinear mapping between measurements and channels issuboptimal in general.
Varasteh M, Gunduz D, Ertem T, 2016, Zero-Delay Joint Source-Channel Coding in the Presence of Interference Known at the Encoder, IEEE Transactions on Communications, Vol: 64, Pages: 3311-3322, ISSN: 0090-6778
Zero-delay transmission of a Gaussian source over an additive white Gaussian noise (AWGN) channel is considered in the presence of an additive Gaussian interference signal. The mean squared error (MSE) distortion is minimized under an average power constraint assuming that the interference signal is known at the transmitter. Optimality of simple linear transmission does not hold in this setting due to the presence of the known interference signal. While the optimal encoder-decoder pair remains an open problem, various non-linear transmission schemes are proposed in this paper. In particular, interference concentration (ICO) and one-dimensional lattice (1DL) strategies, using both uniform and non-uniform quantization of the interference signal, are studied. It is shown that, in contrast to typical scalar quantization of Gaussian sources, a non-uniform quantizer, whose quantization intervals become smaller as we go further from zero, improves the performance. Given that the optimal decoder is the minimum MSE (MMSE) estimator, a necessary condition for the optimality of the encoder is derived, and the numerically optimized encoder (NOE) satisfying this condition is obtained. Based on the numerical results, it is shown that 1DL with nonuniform quantization performs closer (compared to the other schemes) to the numerically optimized encoder while requiring significantly lower complexity.
Gregori M, Gomez-Vilardebo J, Matamoros J, et al., 2016, Wireless Content Caching for Small Cell and D2D Networks, IEEE Journal on Selected Areas in Communications, Vol: 34, Pages: 1222-1234, ISSN: 1558-0008
The fifth generation wireless networks must provide fast and reliable connectivity while coping with the ongoing traffic growth. It is of paramount importance that the required resources, such as energy and bandwidth, do not scale with traffic. While the aggregate network traffic is growing at an unprecedented rate, users tend to request the same popular contents at different time instants. Therefore, caching the most popular contents at the network edge is a promising solution to reduce the traffic and the energy consumption over the backhaul links. In this paper, two scenarios are considered, where caching is performed either at a small base station, or directly at the user terminals, which communicate using Device-to-Device (D2D) communications. In both scenarios, joint design of the transmission and caching policies is studied when the user demands are known in advance. This joint design offers two different caching gains, namely, the pre-downloading and local caching gains. It is shown that the finite cache capacity limits the attainable gains, and creates an inherent tradeoff between the two types of gains. In this context, a continuous time optimization problem is formulated to determine the optimal transmission and caching policies that minimize a generic cost function, such as energy, bandwidth, or throughput. The jointly optimal solution is obtained by demonstrating that caching files at a constant rate is optimal, which allows reformulation of the problem as a finite-dimensional convex program. The numerical results show that the proposed joint transmission and caching policy dramatically reduces the total cost, which is particularised to the total energy consumption at the Macro Base Station (MBS), as well as to the total economical cost for the service provider, when users demand economical incentives for delivering content to other users over the D2D links.
Aguerri IE, Gunduz D, 2016, Distortion Exponent in MIMO Fading Channels With Time-Varying Source Side Information, IEEE Transactions on Information Theory, Vol: 62, Pages: 3597-3617, ISSN: 1557-9654
Transmission of a Gaussian source over a time-varying multiple-input multiple-output (MIMO) channel is studied under strict delay constraints. Availability of a correlated side information at the receiver is assumed, whose quality, i.e., its correlation with the source signal, also varies over time. A block-fading model is considered for the states of the time-varying channel and side information; perfect state information at the receiver is assumed, while the transmitter knows only the statistics. The high signal to noise ratio performance, characterized by the distortion exponent, is studied for this joint source-channel coding problem. An upper bound is derived and compared with several lower bounds based on list decoding (LD), hybrid digital-analog transmission, as well as multi-layer schemes, which transmit successive refinements of the source, relying on progressive or superposition transmission with LD. The optimal distortion exponent is characterized for the single-input multiple-output and multiple-input single-output scenarios by showing that the distortion exponent achieved by multi-layer superposition encoding with joint decoding meets the proposed upper bound. In the MIMO scenario, the optimal distortion exponent is characterized in the low bandwidth ratio regime, and it is shown that the multi-layer superposition encoding performs very close to the upper bound in the high bandwidth ratio regime.
Aguerri IE, Gunduz D, 2016, Capacity of a Class of State-Dependent Orthogonal Relay Channels, IEEE Transactions on Information Theory, Vol: 62, Pages: 1280-1295, ISSN: 1557-9654
The class of orthogonal relay channels in which the orthogonal channels connecting the source terminal to the relay and the destination, and the relay to the destination, depend on a state sequence, is considered. It is assumed that the state sequence is fully known at the destination, while it is not known at the source or the relay. The capacity of this class of relay channels is characterized, and shown to be achieved by the partial decode-compress-and-forward (pDCF) scheme. Then, the capacity of certain binary and Gaussian state-dependent orthogonal relay channels are studied in detail, and it is shown that the compress-and-forward (CF) and partial-decode-and-forward (pDF) schemes are suboptimal in general. To the best of our knowledge, this is the first single relay channel model for which the capacity is achieved by pDCF, while pDF and CF schemes are both suboptimal. Furthermore, it is shown that the capacity of the considered class of state-dependent orthogonal relay channels is in general below the cut-set bound. The conditions under which pDF or CF suffices to meet the cut-set bound, and hence, achieve the capacity, are also derived.
Estella-Aguerri I, Gunduz D, 2016, Joint source-channel coding with time-varying channel and side-information, IEEE Transactions on Information Theory, Vol: 62, Pages: 736-753, ISSN: 0018-9448
Transmission of a Gaussian source over a timevarying Gaussian channel is studied in the presence of timevarying correlated side information at the receiver. A block fading model is considered for both the channel and the side information, whose states are assumed to be known only at the receiver. The optimality of separate source and channel coding in terms of average end-to-end distortion is shown when the channel is static while the side information state follows a discrete or a continuous and quasiconcave distribution. When both the channel and side information states are time-varying, separate source and channel coding is suboptimal in general. A partially informed encoder lower bound is studied by providing the channel state information to the encoder. Several achievable transmission schemes are proposed based on uncoded transmission, separate source and channel coding, joint decoding as well as hybrid digital-analog transmission. Uncoded transmission is shown to be optimal for a class of continuous and quasiconcave side information state distributions, while the channel gain may have an arbitrary distribution. To the best of our knowledge, this is the first example in which the uncoded transmission achieves the optimal performance thanks to the time-varying nature of the states, while it is suboptimal in the static version of the same problem. Then, the optimal distortion exponent, that quantifies the exponential decay rate of the expected distortion in the high SNR regime, is characterized for Nakagami distributed channel and side information states, and it is shown to be achieved by hybrid digital-analog and joint decoding schemes in certain cases, illustrating the suboptimality of pure digital or analog transmission in general.
Cocco G, Gunduz D, Ibars Casas C, 2015, Throughput and Delay Analysis in Video Streaming over Block-Fading Channels, IEEE Transactions on Communications, Vol: 63, Pages: 5206-5217, ISSN: 1558-0857
We study video streaming over a slow fading wireless channel. In a streaming application video packets are required to be decoded and displayed in the order they are transmitted as the transmission goes on. This results in per-packet delay constraints, and the resulting channel can be modeled as a physically degraded fading broadcast channel with as many virtual users as the number of packets. In this paper we study two important quality of user experience (QoE) metrics, namely throughput and inter-decoding delay. We introduce several transmission schemes, and compare their throughput and maximum interdecoding delay performances. We also introduce a genie-aided scheme, which provides theoretical bounds on the achievable performance. We observe that adapting the transmission rate at the packet level, i.e., periodically dropping a subset of the packets, leads to a good tradeoff between the throughput and the maximum inter-decoding delay. We also show that an approach based on initial buffering leads to an asymptotically vanishing packet loss rate at the expense of a relatively large initial delay. For this scheme we derive a condition on the buffering time that leads to throughput maximization.
Yang Q, Gunduz D, 2015, Variable-Power Scheduling for Perpetual Target Coverage in Rechargeable Wireless Sensor Networks, Twelfth International Symposium on Wireless Communication Systems, Publisher: IEEE
Orhan O, Gunduz D, Erkip E, 2015, Source-Channel Coding Under Energy, Delay, and Buffer Constraints, IEEE Transactions on Wireless Communications, Vol: 14, Pages: 3836-3849, ISSN: 1536-1276
Source and channel coding for an energy-limited wireless sensor node is investigated. The sensor node observes independent Gaussian source samples with variances changing over time slots. The channel is modeled as a flat fading channel, whose gain remains constant during each time slot, and changes from one time slot to the next. The compressed samples are stored in a finite data buffer, and need to be delivered to the destination in at most d time slots. The objective is to minimize the average squared-error distortion between the source samples and their reconstructions. First, a battery operated system, in which the sensor node has a finite amount of energy at the beginning of transmission, is investigated. Then, the impact of energy harvesting, and the energy cost of processing and sampling are considered. The optimal compression and transmission policy is formulated as the solution of a convex optimization problem, and the properties of the optimal policies are identified. For the strict delay case, d=1, a two-dimensional (2D) waterfilling interpretation is provided. Numerical results are presented to illustrate the structure of the optimal policy, and to analyze the effect of the delay constraints, data buffer size, energy harvesting, and processing and sampling costs.
Varasteh M, Gunduz D, Tuncel E, 2015, Delay limited transmission of a uniform source over an AWGN channel, International Symposium on Information Theory
Varasteh M, Gunduz D, Tuncel E, 2015, Zero-Delay Joint Source-Channel Coding in the Presence of Interference Known at the Encoder, International Conference on Communication (ICC)
Giaconi G, Gunduz D, Poor HV, 2015, Smart Meter Privacy with an Energy Harvesting Device and Instantaneous Power Constraints, IEEE International Conference on Communications (ICC) 2015, Publisher: IEEE, Pages: 7216-7221
A smart meter (SM) periodically measures end-user electricity consumption and reports it to a utility provider (UP). Despite the advantages of SMs, their use leads to serious concerns about consumer privacy. In this paper, SM privacy is studied by considering the presence of an energy harvesting device (EHD) as a means of masking the user's input load. The user can satisfy part or all of his/her energy needs from the EHD, and hence, less information can be leaked to the UP via the SM. The EHD is typically equipped with a rechargeable energy storage device, i.e., a battery, whose instantaneous energy content limits the user's capability in covering his/her energy usage. Privacy is measured by the information leaked about the user's real energy consumption when the UP observes the energy requested from the grid, which the SM reads and reports to the UP. The minimum information leakage rate is characterized as a computable information theoretic single-letter expression when the EHD battery capacity is either infinite or zero. Numerical results are presented for a discrete binary input load to illustrate the potential privacy gains from the existence of a storage device.
Blasco P, Gunduz D, 2015, Multi-Access Communications With Energy Harvesting: A Multi-Armed Bandit Model and the Optimality of the Myopic Policy, IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, Vol: 33, Pages: 585-597, ISSN: 0733-8716
Gangula R, Gesbert D, Gunduz D, 2015, Optimization of Energy Harvesting MISO Communication System With Feedback, IEEE Journal on Selected Areas in Communications, Vol: 33, Pages: 396-406, ISSN: 1558-0008
Gomez-Vilardebo J, Gunduz D, 2015, Smart Meter Privacy for Multiple Users in the Presence of an Alternative Energy Source, IEEE Transactions on Information Forensics and Security, Vol: 10, Pages: 132-141, ISSN: 1556-6021
Tan O, Gunduz D, Gomez Vilardebo J, 2015, Delay Constrained Linear Transmission of a Mixture of Gaussian Measurements over a Fading Channel, IEEE International Conference on Communications (ICC), Publisher: IEEE, Pages: 4107-4112, ISSN: 1550-3607
Tan O, Gunduz D, Gomez Vilardebo J, 2015, Optimal Privacy-Cost Trade-off in Demand-Side Management with Storage, 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Publisher: IEEE, Pages: 370-374, ISSN: 2325-3789
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Aguerri IE, Gunduz D, 2015, Correlated Gaussian Sources over Gaussian Weak Interference Channels, IEEE Information Theory Workshop, Publisher: IEEE, Pages: 84-88
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Murin Y, Kaspi Y, Dabora R, et al., 2015, On the Transmission of a Bivariate Gaussian Source Over the Gaussian Broadcast Channel With Feedback, IEEE Information Theory Workshop (ITW), Publisher: IEEE
Aguerri IE, Gunduz D, 2015, Gaussian Joint Source-Channel Coding for the Strong Interference Channel, IEEE Information Theory Workshop (ITW), Publisher: IEEE
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