Papers by Daniela Tuninetti
arXiv (Cornell University), Jan 21, 2014
In multiuser information theory it is often assumed that every node in the network possesses all ... more In multiuser information theory it is often assumed that every node in the network possesses all codebooks used in the network. This assumption is however impractical in distributed ad-hoc and cognitive networks. This work considers the twouser Gaussian Interference Channel with one Oblivious Receiver (G-IC-OR), i.e., one receiver lacks knowledge of the interfering cookbook while the other receiver knows both codebooks. We ask whether, and if so how much, the channel capacity of the G-IC-OR is reduced compared to that of the classical G-IC where both receivers know all codebooks. Intuitively, the oblivious receiver should not be able to jointly decode its intended message along with the unintended interfering message whose codebook is unavailable. We demonstrate that in strong and very strong interference, where joint decoding is capacity achieving for the classical G-IC, lack of codebook knowledge does not reduce performance in terms of generalized degrees of freedom (gDoF). Moreover, we show that the sum-capacity of the symmetric G-IC-OR is to within O(log(log(SNR))) of that of the classical G-IC. The key novelty of the proposed achievable scheme is the use of a discrete input alphabet for the non-oblivious transmitter, whose cardinality is appropriately chosen as a function of SNR.
arXiv (Cornell University), Jun 8, 2015
arXiv (Cornell University), Sep 8, 2014
This paper considers a variation of the classical two-user interference channel where the communi... more This paper considers a variation of the classical two-user interference channel where the communication of two interfering source-destination pairs is aided by an additional node that has a priori knowledge of the messages to be transmitted, which is referred to as the cognitive relay. For this Interference Channel with a Cognitive Relay (ICCR) novel outer bounds and capacity region characterizations are derived. In particular, for the class of injective semi-deterministic ICCRs, a sum-rate upper bound is derived for the general memoryless ICCR and further tightened for the Linear Deterministic Approximation (LDA) of the Gaussian noise channel at high SNR, which disregards the noise and focuses on the interaction among the users' signals. The capacity region of the symmetric LDA is completely characterized except for the regime of moderately weak interference and weak links from the CR to the destinations. The insights gained from the analysis of the LDA are then translated back to the symmetric Gaussian noise channel (GICCR). For the symmetric GICCR, an approximate characterization (to within a constant gap) of the capacity region is provided for a parameter regime where capacity was previously unknown. The approximately optimal scheme suggests that message cognition at a relay is beneficial for interference management as it enables simultaneous over the air neutralization of the interference at both destinations.
Shannon theoretic multiuser capacity problems are traditionally formulated under the assumption t... more Shannon theoretic multiuser capacity problems are traditionally formulated under the assumption that all decoding nodes possess all codebooks. However, for certain networks such as cognitive ones, this may be an unrealistic assumption. We work towards understanding the impact of lack of codebook knowledge at some decoding nodes in the network. We do so by considering a two-user interference channel in which one of the receivers has no information about the codebook of the interfering transmitter, while the other receiver has both codebooks. We derive a novel outer bound for the special class of injective semi-deterministic interference channels which incorporates this codebook knowledge explicitly. For the linear deterministic channel, which models the Gaussian channel at high SNR, we demonstrate the surprising fact that non i.i.d. Bernoulli(1/2) points achieve points on the outer bound not achievable by Bernoulli(1/2) inputs. We then show that this is achievable to within a constant gap by a modified Han-Kobayashi scheme. We characterize the capacity region of the Gaussian noise channel to within 1/2 bit, even though we could not determine the set of optimal input distributions. Numerical evaluations suggest that if the non-oblivious transmitter uses a discrete input a larger sum-rate is achievable compared to the case where both users employ Gaussian codebooks or use time division in strong interference regime at high SNR.
IEEE Transactions on Information Theory
2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
The results presented in this paper indicate that future on-demand Deep Brain Stimulation (DBS) s... more The results presented in this paper indicate that future on-demand Deep Brain Stimulation (DBS) systems for chronic use in patients with movement disorders should continuously and adaptively “learn” in order to maintain high symptom control efficacy. In this work, two machine learning algorithms-Decision Tree and LArge Memory STorage And Retrieval (LAMSTAR) neural network, both with surface Electromyography and accelerometry as control signals-are used to predict onset of tremor after DBS has been switched off in two patients, one suffering from Parkinson’s disease and the other from essential tremor. The novelty of this work is that training and testing are done by using different data recorded during sessions at least one week apart. The question is whether the applied algorithms are robust to long-term operation (as patient’s control signal may change over time due to disease progression, displacement of the wearable sensor, etc.). Various metrics are used to compare the performance of the proposed approach to those available in the literature, where training and testing are done on data from the same recording session. It is shown that a 100% sensitivity is achieved for training and testing over the same session; however, the sensitivity reduces when tested over a different session. The ratio of predicted stimulation-off time to observed stimulation-off time value is also found to be lower when training and testing on data from separate sessions. These results point to the need of adaptive learning in on-demand DBS systems.
Entropy
This paper considers the Strongly Asynchronous, Slotted, Discrete Memoryless, Massive Access Chan... more This paper considers the Strongly Asynchronous, Slotted, Discrete Memoryless, Massive Access Channel (SAS-DM-MAC) in which the number of users, the number of messages, and the asynchronous window length grow exponentially with the coding blocklength with their respective exponents. A joint probability of error is enforced, ensuring that all the users’ identities and messages are correctly identified and decoded. Achievability bounds are derived for the case that different users have similar channels, the case that users’ channels can be chosen from a set which has polynomially many elements in the blocklength, and the case with no restriction on the users’ channels. A general converse bound on the capacity region and a converse bound on the maximum growth rate of the number of users are derived. It is shown that reliable transmission with an exponential number of users with an exponential asynchronous exponent with joint error probability is possible at strictly positive rates.
2021 IEEE International Symposium on Information Theory (ISIT)
Coded caching aims to minimize the network's peaktime communication load by leveraging the inform... more Coded caching aims to minimize the network's peaktime communication load by leveraging the information prestored in the local caches at the users. The original single file retrieval setting by Maddah-Ali and Niesen has been recently extended to general Scalar Linear Function Retrieval (SLFR) by Wan et al., who proposed a linear scheme that surprisingly achieves the same optimal load (under the constraint of uncoded cache placement) as in single file retrieval. This paper's goal is to characterize the conditions under which a general SLFR linear scheme is optimal and gain practical insights into why the specific choices made by Wan et al. work. This paper shows that the optimal decoding coefficients are necessarily the product of two terms, one only involving the encoding coefficients and the other only the demands. In addition, the relationships among the encoding coefficients are shown to be captured by the cycles of certain graphs. Thus, a general linear scheme for SLFR can be found by solving a spanning tree problem.
IEEE Transactions on Information Theory, Jan 25, 2021
Maddah-Ali and Niesen (MAN) in 2014 showed that coded caching in single bottleneck-link broadcast... more Maddah-Ali and Niesen (MAN) in 2014 showed that coded caching in single bottleneck-link broadcast networks allows serving an arbitrarily large number of cache-equipped users with a total link load (bits per unit time) that does not scale with the number of users. Since then, the general topic of coded caching has generated enormous interest both from the information theoretic and (network) coding theoretic viewpoint, and from the viewpoint of applications. Building on the MAN work, this paper considers a particular network topology referred to as cache-aided Fog Radio Access Network (Fog-RAN), that includes a Macro-cell Base Station (MBS) co-located with the content server, several cache-equipped Small-cell Base Stations (SBSs), and many users without caches. Some users are served directly by the MBS broadcast downlink, while other users are served by the SBSs. The SBSs can also exchange data via rounds of direct communication via a side channel, referred to as "sidelink". For this novel Fog-RAN model, the fundamental tradeoff among (a) the amount of cache memory at the SBSs, (b) the load on the downlink (from MBS to directly served users and SBSs), and (c) the aggregate load on the sidelink is studied, under the standard worst-case demand scenario. Several existing results are recovered as special cases of this network model and byproduct results of independent interest are given. Finally, the role of topology-aware versus topology-agnostic caching is discussed.
In the coded caching problem as originally formulated by Maddah-Ali and Niesen, a server communic... more In the coded caching problem as originally formulated by Maddah-Ali and Niesen, a server communicates via a noiseless broadcast link to multiple users that have local storage capability. In order for a user to decode the desired file from the coded multicast transmission, the demands of all the users must be globally known, which may violate the privacy of the users. To overcome this privacy problem, Wan and Caire recently proposed several schemes that attain coded multicasting gain while simultaneously guarantee information theoretic privacy of the users'demands. In device to device (D2D) networks, the demand privacy problem is further exacerbated by the fact that each user is also a transmitter, which should know the demanded messages of the other users in order to form coded multicast transmissions. This paper solves this seemingly unfeasible problem with the aid of a trusted server. Specifically, during the delivery phase, the trusted server collects the users' demands a...
ArXiv, 2018
This paper considers a novel cache-aided "fog" Radio Access Network (Fog-RAN) architect... more This paper considers a novel cache-aided "fog" Radio Access Network (Fog-RAN) architecture including a Macro-cell Base Station (MBS) and several Small-cell Base Stations (SBSs), serving users without caches. Some users, not in the reach of SBSs, are directly served by the MBS. Other users, in the reach of SBSs, are "offloaded" and receive information only from the SBSs through high throughput links. The SBSs have their own local caches. The MBS broadcasts packets to the SBSs and the directly served users. Subsequently, the SBSs can communicate among each other such that each SBS can obtain enough information to decode demanded files by its connected users. For the proposed Fog-RAN we study the memory-loads tradeoff for the worst-case demands. The main contribution of this paper is the design of a novel inter-file coded cache placement and a novel D2D caching scheme with shared-caches to handle the inter-SBS communication phase. The proposed scheme is proved to be...
2016 Information Theory and Applications Workshop (ITA), 2016
This paper considers a Gaussian channel with one transmitter and two receivers. The goal is to ma... more This paper considers a Gaussian channel with one transmitter and two receivers. The goal is to maximize the communication rate at the intended/primary receiver subject to a disturbance constraint at the unintended/secondary receiver. The disturbance is measured in terms of minimum mean square error (MMSE) of the interference that the transmission to the primary receiver inflicts on the secondary receiver. The paper presents a new upper bound for the problem of maximizing the mutual information subject to an MMSE constraint. The new bound holds for vector inputs of any length and recovers a previously known limiting (when the length for vector input tends to infinity) expression from the work of Bustin et al. The key technical novelty is a new upper bound on MMSE. This new bound allows one to bound the MMSE for all signal-to-noise ratio (SNR) values below a certain SNR at which the MMSE is known (which corresponds to the disturbance constraint). This new bound complements the ‘single...
2016 IEEE Global Communications Conference (GLOBECOM), 2016
In the near future, radar and communication systems will share the spectrum. This motivates the s... more In the near future, radar and communication systems will share the spectrum. This motivates the study of how the two systems, which have traditionally operated in different bands, may co-exist. This paper investigates the effect of radar interference (unaltered, beyond the communication system designer's control) on an uncoded communication system, using complex-valued modulation schemes when the Maximum-A-Posteriori (MAP) detector is used. For all commonly used higher order modulation schemes, the Symbol Error Rate (SER) exhibits an "error floor" for the radar interference much larger than the signal power, which can be exactly characterized; in this regime the optimal MAP detector behaves like an interference canceller; interestingly, in this regime the channel behaves as a real-valued phase- fading AWGN channel with receiver CSI, thus indicating a loss of one of the two complex dimensions compared to the complex-valued interference-free channel.
IEEE Transactions on Information Theory, 2016
This paper considers the end-to-end mean squared error distortion in reconstructing a memoryless ... more This paper considers the end-to-end mean squared error distortion in reconstructing a memoryless proper-complex Gaussian source transmitted over a set of parallel block-fading Gaussian noise channels, where the fading gains are modeled as correlated Rayleigh distributed random variables with different average powers, thus resulting in asymmetric average received signal noise ratios (SNRs). The distortion exponent (i.e., how fast the average distortion decays to zero as the average received SNR increases) of several coding strategies based on separate source and channel coding is characterized. The definition of distortion exponent commonly used in the literature for SNR-symmetric channels is generalized to the case of SNR-asymmetric channels. It is shown that fading correlation degrades the achievable mean squared error distortion, but does not affect the distortion exponent in the analyzed achievable schemes. The logarithm of the determinant of the fading correlation matrix is found to be a proxy for measuring the performance degradation due to correlation as compared with the case of independent fading. The proposed framework allows one to study any number of correlated parallel channels, contrary to the most of the literature that restricts attention to two channels only, with the same received SNR and with independent fading. In particular, a scheme based on the multiple description coding with more than two descriptions is analyzed; it is shown that determining the distortion exponent in this setting reduces to solving a linear program, which can be done numerically very efficiently. The proposed methodology relies on combining the ideas from linear innovation sequences and properties of determinant of sub-matrices. Interestingly, it is found that SNR-asymmetry is beneficial for multiple description coding when the total average received SNR in decibel is held constant. Even in the SNR-symmetric case, asymmetry in the compression rates is shown to lead to a larger distortion exponent than symmetric rates.
2016 IEEE Information Theory Workshop (ITW), 2016
This paper considers the minimum mean p-th error (MMPE) estimation problem: estimating a random v... more This paper considers the minimum mean p-th error (MMPE) estimation problem: estimating a random vector in the presence of additive white Gaussian noise (AWGN) in order to minimize an Lp norm of the estimation error. The MMPE generalizes the classical minimum mean square error (MMSE) estimation problem. This paper derives basic properties of the optimal MMPE estimator and MMPE functional. Optimal estimators are found for several inputs of interests, such as Gaussian and binary symbols. Under an appropriate p-th moment constraint, the Gaussian input is shown to be asymptotically the hardest to estimate for any p ≥ 1. By using a conditional version of the MMPE, the famous “MMSE single-crossing point” bound is shown to hold for the MMPE too for all p ≥ 1, up to a multiplicative constant. Finally, the paper develops connections between the conditional differential entropy and the MMPE, which leads to a tighter version of the Ozarow-Wyner lower bound on the rate achieved by discrete inputs on AWGN channels.
2015 49th Asilomar Conference on Signals, Systems and Computers, 2015
Recent work demonstrated that for the two-user Gaussian Interference Channel (G-IC) sub-optimal p... more Recent work demonstrated that for the two-user Gaussian Interference Channel (G-IC) sub-optimal point-to-point codes can outperform optimal (Gaussian) point-to-point codes. However, it is not clear how far from capacity such sub-optimal codes operate. This work demonstrates a family of sub-optimal codes, generated from a mixture of Gaussian and discrete random variables, that is optimal up to an additive gap for the G-IC. The developed tools are of interest on their own and can be used in a variety of channel models. For example, it can be shown that the capacity of the block-asynchronous G-IC where the decoders are prevented from decoding the interfering signals is to within an additive gap of the capacity of the classical G-IC where the receivers are fully synchronized and informed about the interfering codebooks.
The interference channel is a model for a wireless network where several source-destination pairs... more The interference channel is a model for a wireless network where several source-destination pairs compete for the same resources. When the sources transmit simultaneously the destinations experience unwanted interference. Determining how to optimally manage the interference is a long standing open problem in network information theory. In this talk we review one emerging interference management technique: cooperation. Cooperation can occur among source nodes only (Source Cooperation or Generalized Feedback), or among destination nodes only (Destination Cooperation), or among all nodes (General Cooperation). For the special case of Gaussian noise channels, we compare the different forms of cooperation in terms of symmetric generalized degrees of freedom. When known, we also discuss capacity results to within a constant number of bits.
IEEE Transactions on Cognitive Communications and Networking, 2015
This paper provides a survey of the state-of-the-art information theoretic analysis for overlay m... more This paper provides a survey of the state-of-the-art information theoretic analysis for overlay multiuser (more than two pairs) cognitive networks and reports new capacity results. In an overlay scenario, cognitive / secondary users share the same frequency band with licensed / primary users to efficiently exploit the spectrum. They do so without degrading the performance of the incumbent users, and may possibly even aid in transmitting their messages as cognitive users are assumed to possess the message(s) of primary user(s) and possibly other cognitive user(s). The survey begins with a short overview of the two-user overlay cognitive interference channel. The evolution from two-user to three-user overlay cognitive interference channels is described next, followed by generalizations to multiuser (arbitrary number of users) cognitive networks. The rest of the paper considers K-user cognitive interference channels with different message knowledge structures at the transmitters. Novel capacity inner and outer bounds are proposed. Channel conditions under which the bounds meet, thus characterizing the information theoretic capacity of the channel, for both Linear Deterministic and Gaussian channel models, are derived. The results show that for certain channel conditions distributed cognition, or having a cumulative message knowledge structure at the nodes, may not be worth the overhead as (approximately) the same capacity can be achieved by having only one global cognitive user whose role is to manage all the interference in the network. The paper concludes with future research directions.
2015 IEEE Information Theory Workshop (ITW), 2015
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Papers by Daniela Tuninetti