Imperial College London

DrDenizGunduz

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Reader in Information Theory and Communications
 
 
 
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Contact

 

+44 (0)20 7594 6218d.gunduz Website

 
 
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Assistant

 

Ms Joan O'Brien +44 (0)20 7594 6316

 
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Location

 

1016Electrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

181 results found

Amiri MM, Gunduz D, 2018, Caching and Coded Delivery over Gaussian Broadcast Channels for Energy Efficiency, IEEE Journal on Selected Areas in Communications, ISSN: 0733-8716

IEEE A cache-aided K-user Gaussian broadcast channel (BC) is considered. The transmitter has a library of N equalrate files, from which each user demands one. The impact of the equal-capacity receiver cache memories on the minimum required transmit power to satisfy all user demands is studied. Considering uniformly random demands across the library, both the minimum average power (averaged over all demand combinations) and the minimum peak power (minimum power required to satisfy all demand combinations) are studied. Upper bounds are presented on the minimum required average and peak transmit power as a function of the cache capacity considering both centralized and decentralized caching. The lower bounds on the minimum required average and peak power values are also derived assuming uncoded cache placement. The bounds for both the peak and average power values are shown to be tight in the centralized scenario through numerical simulations. The results in this paper show that proactive caching and coded delivery can provide significant energy savings in wireless networks.

JOURNAL ARTICLE

Amiri MM, Gunduz D, 2018, On the Capacity Region of a Cache-Aided Gaussian Broadcast Channel with Multi-Layer Messages, Pages: 1909-1913, ISSN: 2157-8095

© 2018 IEEE. A cache-aided K-user Gaussian broadcast channel (BC) is studied. The transmitter has a library of N files, from which each user requests one. The users are equipped with caches of different sizes, which are filled without the knowledge of the user requests in a centralized manner. Differently from the literature, it is assumed that each file can be delivered to different users at different rates, which may correspond to different quality representations of the underlying content, e.g., scalable coded video segments. Accordingly, instead of a single achievable rate, the system performance is characterized by a rate tuple, which corresponds to the vector of rates users' requests can be delivered at. The goal is to characterize the set of all achievable rate tuples for a given total cache capacity by designing joint cache and channel coding schemes together with cache allocation across users. Assuming that the users are ordered in increasing channel quality, each file is coded into K layers, and only the first k layers of the requested file are delivered to user k, k=1, \ldots, K. Three different coding schemes are proposed, which differ in the way they deliver the coded contents over the BC; in particular, time-division, superposition, and dirty paper coding schemes are studied. Corresponding achievable rate regions are characterized, and compared with a novel outer bound. To the best of our knowledge, this is the first work studying the delivery of files at different rates over a cache-aided noisy BC.

CONFERENCE PAPER

Bharath BN, Nagananda KG, Gunduz D, Poor HVet al., 2018, Caching With Time-Varying Popularity Profiles: A Learning-Theoretic Perspective, IEEE Transactions on Communications, ISSN: 0090-6778

IEEE Content caching at the small-cell base stations (sBSs) in a heterogeneous wireless network is considered. A cost function is proposed that captures the backhaul link load called the “offloading loss”, which measures the fraction of the requested files that are not available in the sBS caches. As opposed to the previous approaches that consider time-invariant and perfectly known popularity profile, caching with non-stationary and statistically dependent popularity profiles (assumed unknown, and hence, estimated) is studied from a learning-theoretic perspective. A probably approximately correct result is derived, which presents a high probability bound on the offloading loss difference, i.e., the error between the estimated and the optimal offloading loss. The difference is a function of the Rademacher complexity, the β-mixing coefficient, the number of time slots, and a measure of discrepancy between the estimated and true popularity profiles. A cache update algorithm is proposed, and simulation results are presented to show its superiority over periodic updates. The performance analyses for Bernoulli and Poisson request models are also presented.

JOURNAL ARTICLE

Cao D, Zhang D, Chen P, Liu N, Kang W, Gunduz Det al., 2018, Coded Caching with Heterogeneous Cache Sizes and Link Qualities: The Two-User Case, Pages: 1545-1549, ISSN: 2157-8095

© 2018 IEEE. The centralized coded caching problem is studied under heterogeneous cache sizes and channel qualities from the server to the users, focusing on the two-user case. A server holding N files is considered to be serving two users with arbitrary cache capacities of M-{1} and M-{2}, and it is assumed that in addition to a shared common link, each user also has a private link from the server available during the delivery phase. Optimal caching and delivery strategies that minimize the worst-case delivery latency are presented for an arbitrary N. The converse proof benefits from Tian's observation that it suffices to consider file-index symmetric caching schemes, while the achievability is obtained through memory-sharing among certain special (M-{1}, M-{2}) pairs. The optimal scheme is shown to exploit the private link capacities by transmitting part of the corresponding user's request in an uncoded fashion. When there are no private links, the results presented here improve upon the two known results in the literature, namely, i) equal cache capacities and arbitrary number of files; and ii) unequal cache capacities and N = 2 files.

CONFERENCE PAPER

Ceran ET, Gunduz D, Gyorgy A, 2018, Average age of information with hybrid ARQ under a resource constraint, Wireless Communications and Networking Conference (WCNC), Publisher: IEEE, ISSN: 1525-3511

Scheduling the transmission of status updates over an error-prone communication channel is studied in order to minimize the long-term average age of information (AoI) at the destination under a constraint on the average number of transmissions at the source node. After each transmission, the source receives an instantaneous ACK/NACK feedback, and decides on the next update without prior knowledge on the success of future transmissions. First, the optimal scheduling policy is studied under different feedback mechanisms when the channel statistics are known; in particular, the standard automatic repeat request (ARQ) and hybrid ARQ (HARQ) protocols are considered. Then, for an unknown environment, an average-cost reinforcement learning (RL) algorithm is proposed that learns the system parameters and the transmission policy in real time. The effectiveness of the proposed methods are verified through numerical simulations.

CONFERENCE PAPER

Coon JP, Badiu M-A, Gunduz D, 2018, On the Conditional Entropy of Wireless Networks, 16th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), Publisher: IEEE

CONFERENCE PAPER

Giaconi G, Gunduz D, Poor HV, 2018, Smart Meter Privacy With Renewable Energy and an Energy Storage Device, IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, Vol: 13, Pages: 129-142, ISSN: 1556-6013

JOURNAL ARTICLE

Guler B, Gunduz D, Yener A, 2018, Lossy Coding of Correlated Sources Over a Multiple Access Channel: Necessary Conditions and Separation Results, IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 64, Pages: 6081-6097, ISSN: 0018-9448

JOURNAL ARTICLE

Mital N, Gunduz D, Ling C, 2018, Coded Caching in a Multi-Server System with Random Topology, IEEE Wireless Communications and Networking Conference (WCNC), Publisher: IEEE, ISSN: 1525-3511

CONFERENCE PAPER

Mohammadi Amiri M, Gunduz D, 2018, Cache-aided content delivery over erasure broadcast channels, IEEE Transactions on Communications, Vol: 66, Pages: 370-381, ISSN: 0090-6778

A cache-aided broadcast network is studied, in which a server delivers contents to a group of receivers over a packet erasure broadcast channel (BC). The receivers are divided into two sets with regards to their channel qualities: the weak and strong receivers, where all the weak receivers have statistically worse channel qualities than all the strong receivers. The weak receivers, in order to compensate for the high erasure probability they encounter over the channel, are equipped with cache memories of equal size, while the receivers in the strong set have no caches. Data can be pre-delivered to weak receivers’ caches over the off-peak traffic period before the receivers reveal their demands. Allowing arbitrary erasure probabilities for the weak and strong receivers, a joint caching and channel coding scheme, which divides each file into several subfiles, and applies a different caching and delivery scheme for each subfile, is proposed. It is shown that all the receivers, even those without any cache memories, benefit from the presence of caches across the network. An information theoretic trade-off between the cache size and the achievable rate is formulated. It is shown that the proposed scheme improves upon the state-of-the-art in terms of the achievable trade-off.

JOURNAL ARTICLE

Ozfatura E, Gunduz D, 2018, Mobility and Popularity-Aware Coded Small-Cell Caching, IEEE COMMUNICATIONS LETTERS, Vol: 22, Pages: 288-291, ISSN: 1089-7798

JOURNAL ARTICLE

Rassouli B, Gunduz D, 2018, On Perfect Privacy, Pages: 2551-2555, ISSN: 2157-8095

© 2018 IEEE. For a pair of (dependent) random variables (X, Y), the following problem is addressed: What is the maximum information that can be revealed about Y, while disclosing no information about X? Assuming that a Markov kernel maps Y to the revealed information U, it is shown that the maximum mutual information between Y and U, i.e., I(Y; U), can be obtained as the solution of a standard linear program, when X and U are required to be independent, called perfect privacy. The resulting quantity is shown to be greater than or equal to the non-private information about X carried by Y. For jointly Gaussian (X, Y), it is shown that perfect privacy is not possible if the kernel is applied to only Y; whereas perfect privacy can be achieved if the mapping is from both X and Y; that is, if the private variables can also be observed at the encoder. Finally, it is shown that when Y is not a deterministic function of X, perfect privacy is always feasible when the mapping has access to both X and Y.1

CONFERENCE PAPER

Roushdy A, Motahari AS, Nafie M, Gunduz Det al., 2018, Cache-Aided Fog Radio Access Networks with Partial Connectivity, IEEE Wireless Communications and Networking Conference (WCNC), Publisher: IEEE, ISSN: 1525-3511

CONFERENCE PAPER

Shi J, Liu L, Gündüz D, Ling Cet al., 2018, Polar codes and polar lattices for the heegard-berger problem, Pages: 100-105

© 2018 VDE VERLAG GMBH. Explicit coding schemes are proposed to achieve the rate-distortion bound for the Heegard-Berger problem using polar codes. Specifically, a nested polar code construction is employed to achieve the rate-distortion bound for the binary case. The nested structure contains two optimal polar codes for lossy source coding and channel coding, respectively. Moreover, a similar nested polar lattice construction is employed for the Gaussian case. The proposed polar lattice is constructed by nesting a quantization polar lattice and an AWGN capacityachieving polar lattice.

CONFERENCE PAPER

Shi J, Liu L, Gunduz D, Ling Cet al., 2018, Polar Codes and Polar Lattices for the Heegard-Berger Problem, IEEE TRANSACTIONS ON COMMUNICATIONS, Vol: 66, Pages: 3760-3771, ISSN: 0090-6778

JOURNAL ARTICLE

Somuyiwa SO, Gyorgy A, Gunduz D, 2018, A Reinforcement-Learning Approach to Proactive Caching in Wireless Networks, IEEE Journal on Selected Areas in Communications, Vol: 36, Pages: 1331-1344, ISSN: 0733-8716

© 1983-2012 IEEE. We consider a mobile user accessing contents in a dynamic environment, where new contents are generated over time (by the user's contacts) and remain relevant to the user for random lifetimes. The user, equipped with a finite-capacity cache memory, randomly accesses the system and requests all the relevant contents at the time of access. The system incurs an energy cost associated with the number of contents downloaded and the channel quality at that time. Assuming causal knowledge of the channel quality, the content profile, and the user-access behavior, we model the proactive caching problem as a Markov decision process with the goal of minimizing the long-term average energy cost. We first prove the optimality of a threshold-based proactive caching scheme, which dynamically caches or removes appropriate contents from the memory, prior to being requested by the user, depending on the channel state. The optimal threshold values depend on the system state and hence are computationally intractable. Therefore, we propose parametric representations for the threshold values and use reinforcement-learning algorithms to find near-optimal parameterizations. We demonstrate through simulations that the proposed schemes significantly outperform classical reactive downloading and perform very close to a genie-aided lower bound.

JOURNAL ARTICLE

Sreekumar S, Gunduz D, 2018, Testing Against Conditional Independence under Security Constraints, Pages: 181-185, ISSN: 2157-8095

© 2018 IEEE. A distributed binary hypothesis testing problem involving three parties, a remote node, called the observer, a legitimate decoder, called the detector, and an adversary, is studied. The remote node observes a discrete memoryless source, and communicates its observations over a rate-limited noiseless public channel to the detector, which tests for the conditional independence of its own observations from that of the remote node, conditioned on some additional side information. The adversary, in addition to observing the public message, has access to its own correlated side-information. Considering the type 2 error exponent for a given type 1 error probability constraint as the performance measure for the hypothesis test at the detector, and equivocation of the source at the adversary as the secrecy measure, a single-letter characterization of the rate-error exponent-equivocation trade-off is established. Additionally, for a general distortion measure, imposing the average distortion at the adversary as the measure of secrecy achieved, an inner bound on the trade-off between the rate, error exponent and average distortion is obtained. This bound is shown to be tight under the less noisy condition on the adversary's side information.

CONFERENCE PAPER

Yang Q, Gunduz D, 2018, Coded Caching and Content Delivery With Heterogeneous Distortion Requirements, IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 64, Pages: 4347-4364, ISSN: 0018-9448

JOURNAL ARTICLE

Yang Q, Hassanzadeh P, Gunduz D, Erkip Eet al., 2018, Centralized Caching and Delivery of Correlated Contents over a Gaussian Broadcast Channel, 16th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), Publisher: IEEE

CONFERENCE PAPER

Abad MSH, Gunduz D, Ercetin O, 2017, Communication over a Time Correlated Channel with an Energy Harvesting Transmitter, International Symposium on Wireless Communication Systems (ISWCS), Publisher: IEEE, Pages: 331-336, ISSN: 2154-0217

CONFERENCE PAPER

Amiri MM, Gunduz D, 2017, Fundamental Limits of Coded Caching: Improved Delivery Rate-Cache Capacity Tradeoff, IEEE TRANSACTIONS ON COMMUNICATIONS, Vol: 65, Pages: 806-815, ISSN: 0090-6778

JOURNAL ARTICLE

Amiri MM, Gunduz D, 2017, Decentralized Caching and Coded Delivery over Gaussian Broadcast Channels, IEEE International Symposium on Information Theory (ISIT), Publisher: IEEE, Pages: 2785-2789

CONFERENCE PAPER

Amiri MM, Gunduz D, 2017, Cache-aided data delivery over erasure broadcast channels, ISSN: 1550-3607

© 2017 IEEE. A cache-aided erasure broadcast channel is studied. The receivers are divided into two sets: the weak and strong receivers, where the receivers in the same set all have the same erasure probability. The weak receivers, in order to compensate for the high erasure probability, are equipped with cache memories of equal size, while the receivers in the strong set have no caches. Data can be pre-delivered to weak receivers' caches over the off-peak traffic period before the receivers reveal their demands. A joint caching and channel coding scheme is proposed such that all the receivers, even the receivers without any cache memories, benefit from the presence of caches across the network. The trade-off between the cache size and the achievable rate is studied, and it is shown that the proposed scheme significantly improves the achievable trade-off upon the state-of-the-art.

CONFERENCE PAPER

Amiri MM, Yang Q, Gunduz D, 2017, Decentralized Caching and Coded Delivery With Distinct Cache Capacities, IEEE TRANSACTIONS ON COMMUNICATIONS, Vol: 65, Pages: 4657-4669, ISSN: 0090-6778

JOURNAL ARTICLE

Bharath BN, Nagananda KG, Gunduz D, Poor HVet al., 2017, Learning-Based Content Caching with Time-Varying Popularity Profiles, IEEE Global Communications Conference (GLOBECOM), Publisher: IEEE, ISSN: 2334-0983

CONFERENCE PAPER

Faqir OJ, Kerrigan EC, Gunduz D, 2017, Joint optimization of transmission and propulsion in aerial communication networks, IEEE 56th Annual Conference on Decision and Control (CDC), Publisher: IEEE, ISSN: 0743-1546

CONFERENCE PAPER

Giaconi G, Gunduz D, Poor HV, 2017, Optimal Demand-Side Management for Joint Privacy-Cost Optimization with Energy Storage, IEEE International Conference on Smart Grid Communications (SmartGridComm), Publisher: IEEE, Pages: 265-270, ISSN: 2373-6836

CONFERENCE PAPER

Guler B, Gunduz D, Yener A, 2017, On the Necessary Conditions for Transmitting Correlated Sources over a Multiple Access Channel, IEEE International Symposium on Information Theory (ISIT), Publisher: IEEE, Pages: 923-927

CONFERENCE PAPER

Isikman AO, Yuksel M, Gunduz D, 2017, A Low-Complexity Policy for Outage Probability Minimization With an Energy Harvesting Transmitter, IEEE COMMUNICATIONS LETTERS, Vol: 21, Pages: 917-920, ISSN: 1089-7798

JOURNAL ARTICLE

Koken E, Gunduz D, Tuncel E, 2017, Energy-Distortion Exponents in Lossy Transmission of Gaussian Sources Over Gaussian Channels, IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 63, Pages: 1227-1236, ISSN: 0018-9448

JOURNAL ARTICLE

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