Igor Bjelakovic

• Dr. rer. nat.
• Technische Universität Berlin

We propose a reconfigurable intelligent surface (RIS)-assisted wiretap channel, where the RIS is strategically deployed to provide a spatial separation to the transmitter, and orthogonal combiners are employed at the legitimate receiver to extract the data streams from the direct and RIS-assisted links. Then we derive the achievable secrecy rate un...

We propose a new proof method for direct coding theorems for wiretap channels where the eavesdropper has access to a quantum version of the transmitted signal on an infinite-dimensional Hilbert space and the legitimate parties communicate through a classical channel or a classical input, quantum output (cq) channel. The transmitter input can be sub...

We study communication over a Gaussian multiple-access channel (MAC) with two types of transmitters: Digital transmitters hold a message from a discrete set that needs to be communicated to the receiver with vanishing error probability. Analog transmitters hold sequences of analog values. Some functions of these distributed values (but not the valu...

Ultra-Wideband (UWB) technology re-emerges as a groundbreaking ranging technology with its precise micro-location capabilities and robustness. This paper highlights the security dimensions of UWB technology, focusing in particular on the intricacies of device fingerprinting for authentication, examined through the lens of state-of-the-art deep lear...

In this paper, we introduce Over-the-Air Multi-Party Communication, a novel approach to achieve efficiently scalable, private, secure, and dependable data aggregation using Over-the-Air computation. The main idea of our approach lies in a combination of techniques from lattice coding, Over-the-Air computation and secure Multi-Party Computation to s...

Lagrange coded computation (LCC) is essential to solving problems about matrix polynomials in a coded distributed fashion; nevertheless, it can only solve the problems that are representable as matrix polynomials. In this paper, we propose AICC, an AI-aided learning approach that is inspired by LCC but also uses deep neural networks (DNNs). It is a...

We propose a new proof method for direct coding theorems for wiretap channels where the eavesdropper has access to a quantum version of the transmitted signal on an infinite dimensional Hilbert space. This method yields errors that decay exponentially with increasing block lengths. Moreover, it provides a guarantee of a quantum version of semantic...

The Open-RAN architecture is a highly promising and future-oriented architecture. It is intended to open up the radio access network and enable more innovation and competition in the market. This will lead to RANs for current 5G networks, but especially for future 6G networks, to move away from the current centralised, provider-specific 3G RAN arch...

The Open RAN architecture is a promising and future-oriented architecture. It is intended to open up the radio access network (RAN) and enable more innovation and competition in the market. This will lead to RANs for current 5G networks, but especially for future 6G networks, evolving from the current highly integrated, vendor-specific RAN architec...

Commercial radar sensing is gaining relevance and machine learning algorithms constitute one of the key components that are enabling the spread of this radio technology into areas like surveillance or healthcare. However, radar datasets are still scarce and generalization cannot be yet achieved for all radar systems, environment conditions or desig...

Over-the-Air (OTA) computation is the problem of computing functions of distributed data without transmitting the entirety of the data to a central point. By avoiding such costly transmissions, OTA computation schemes can achieve a better-than-linear (depending on the function, often logarithmic or even constant) scaling of the communication cost a...

This paper addresses the problem of Over-The-Air (OTA) computation in wireless networks which has the potential to realize huge efficiency gains for instance in training of distributed ML models. We provide non-asymptotic, theoretical guarantees for OTA computation in fast-fading wireless channels where the fading and noise may be correlated. The d...

Motivated by various applications in distributed Machine Learning (ML) in massive wireless sensor networks, this paper addresses the problem of computing approximate values of functions over the wireless channel and provides examples of applications of our results to distributed training and ML-based prediction. The ``over-the-air'' computation of...

We revisit the problem of distributed approximation of functions over multiple-access channels. Contrary to previous works, however, we do not consider the approximation problem itself, but instead we propose a method of incorporating security constraints into a class of approximation schemes to protect against passive eavesdropping. We specificall...

In this work, we consider the problem of distributed approximation of functions over multiple-access channels with additive noise. In contrast to previous works, we take fast fading into account and give explicit probability bounds for the approximation error allowing us to derive bounds on the number of channel uses that are needed to approximate...

We characterize the resolvability region for a large class of point-to-point channels with continuous alphabets. In our direct result, we prove not only the existence of good resolvability codebooks, but adapt an approach based on the Chernoff-Hoeffding bound to the continuous case showing that the probability of drawing an unsuitable codebook is d...

Building upon previous work on the relation between secrecy and channel resolvability, we revisit a secrecy proof for the multiple-access channel (MAC) from the perspective of resolvability. We then refine the approach in order to obtain some novel results on the second-order achievable rates. Establishing a conceptually simple converse proof for r...

Building upon previous work on the relation between secrecy and channel resolvability, we revisit a secrecy proof for the multiple-access channel from the perspective of resolvability. We then refine the approach in order to obtain some novel results on the second-order achievable rates.

Inspired by group testing algorithms and the coded computation paradigm, we propose and analyze a novel multiple access scheme for detecting active users in large-scale networks. The scheme consists of a simple randomized detection algorithm that uses computation coding as intermediate steps for computing logical disjunction functions over the mult...

We consider a discrete memoryless broadcast channel consists of two users and a sender. The sender has two independent confidential messages for each user. We extend the work of Liu et al.\ on broadcast channels with two confidential messages with weak secrecy criterion to strong secrecy. Our results are based on an extension of the techniques deve...

We determine the optimal rates of universal quantum codes for entanglement transmission and generation under channel uncertainty. In the simplest scenario the sender and receiver are provided merely with the information that the channel they use belongs to a given set of channels, so that they are forced to use quantum codes that are reliable for t...

We consider compound as well as arbitrarily varying classical-quantum channel models. For classical-quantum compound channels, we give an elementary proof of the direct part of the coding theorem. A weak converse under average error criterion to this statement is also established. We use this result together with the robustification and elimination...

In this work the arbitrarily varying wiretap channel AVWC is studied. We derive a lower bound on the random code secrecy capacity for the average error criterion and the strong secrecy criterion in the case of a best channel to the eavesdropper by using Ahlswede's robustification technique for ordinary AVCs. We show that in the case of a non-symmet...

In this work the arbitrarily varying wiretap channel AVWC under the average error criterion and the strong secrecy criterion is studied. We show that in the case of a non-symmetrisable channel to the legitimate receiver the deterministic code secrecy capacity equals the random code secrecy capacity and thus we establish a result for the AVWC simila...

We give an overview of the problem of Over-the-Air (OTA) computation and the currently available research, and of two important applications: Distributed consensus algorithms and distributed Machine Learning. For the latter, we specifically consider an application of OTA computation in Horizontal and Vertical Federated Learning. We then survey some...

We consider quantum state merging under uncertainty of the state held by the merging parties. More precisely we determine the optimal entanglement rate of a merging process when the state is unknown up to membership in a certain set of states. We find that merging is possible at the lowest rate allowed by the individual states.

We determine the optimal entanglement rate of quantum state merging when assuming that the state is unknown except for its membership in a certain set of states. We find that merging is possible at the lowest rate allowed by the individual states. Additionally, we establish a lower bound for the classical cost of state merging under state uncertain...

We derive a lower bound on the secrecy capacity of the compound wiretap channel with channel state information at the transmitter which matches the general upper bound on the secrecy capacity of general compound wiretap channels given by Liang et al. and thus establishing a full coding theorem in this case. We achieve this with a stronger secrecy c...

We derive a lower bound on the secrecy capacity of the compound wiretap channel with channel state information at the transmitter which matches the general upper bound on the secrecy capacity of general compound wiretap channels given by Liang et al. and thus establishing a full coding theorem in this case. We achieve this with a quite strong secre...

The concept of bidirectional relaying is a key technique to improve the performance in future wireless networks. It applies to three-node networks, where a relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. It divides the whole communication into two phases, namely the multiple access a...

We characterize the capacity region of the compound Discrete Memoryless Multiple Access Channel, where both transmitters have an additional common message. The channel state information is as follows: for each transmitter, there is a finite partition of the set of channels. Each transmitter knows which element of his partition the channel actually...

Bidirectional relaying is a promising approach to improve the performance in wireless networks such as sensor, ad-hoc, and even cellular systems. Bidirectional relaying applies to three-node networks, where a relay establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. First, the two nodes transmit th...

We investigate entanglement transmission over an unknown channel in the presence of a third party (called the adversary), which is enabled to choose the channel from a given set of memoryless but non-stationary channels without informing the legitimate sender and receiver about the particular choice that he made. This channel model is called an arb...

For a downlink scenario with two base stations and one receiving mobile, where the base stations are connected by a noiseless finite-capacity backbone, we determine the optimal cooperation and coding strategy. The performance is not influenced by the degree of channel state information at the mobile, but it increases with increasing channel state i...

We derive a regularized formula for the common randomness assisted entanglement transmission capacity of finite arbitrarily varying quantum channels (AVQC's). For finite AVQC's with positive capacity for classical message transmission we show, by derandomization through classical forward communication, that the random capacity for entanglement tran...

The concept of bidirectional relaying shows the potential to improve the performance in wireless networks such as sensor, ad-hoc, and even cellular systems. It applies to three-node networks, where a relay node establishes a bidirectional communication between two other nodes. In the first phase of a decode-and-forward protocol, the two nodes trans...

The goal of this paper is to provide a rigorous information-theoretic analysis of subnetworks of interference networks. We prove two coding theorems for the compound multiple-access channel with an arbitrary number of channel states. The channel state information at the transmitters is such that each transmitter has a finite partition of the set of...

The concept of bidirectional relaying is a key technique to improve the performance in wireless networks such as sensor, ad-hoc, and even cellular systems. It applies to three-node networks, where a relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. We assume that the communication is d...

One key feature to improve the performance of future wireless communication systems will be the use of relays. In this work, we consider the bidirectional relay channel, where a relay node establishes a bidirectional communication between two nodes, and study coding strategies for the case of unknown varying channels. In the first phase of a decode...

In this work we study optimal coding strategies for bidirectional relaying under the condition of arbitrarily varying channels. We consider a three-node network where a relay node establishes a bidirectional communication between two nodes using a spectrally efficient decode-and-forward protocol. In the first phase the two nodes transmit their mess...

We determine the optimal achievable rate at which entanglement can be reliably transmitted when the memoryless channel used during transmission is unknown both to sender and receiver. To be more precise, we assume that both of them only know that the channel belongs to a given set of channels. Thus, they have to use encoding and decoding schemes th...

We determine the capacity of compound classical-quantum channels. As a consequence, we obtain the capacity formula for the averaged classical-quantum channels. The capacity result for compound channels demonstrates, as in the classical setting, the existence of reliable universal classical-quantum codes in scenarios where the only a priori informat...

We consider the broadcast phase of a spectrally efficient two-phase decode-and-forward protocol which is used by a relay node to establish a bidirectional communication between two nodes. In the first phase the two nodes transmit their message to the relay node which decodes the messages. In the succeeding phase the relay node broadcasts a re-encod...

We consider transmission over a wireless multiple antenna communication system operating in a Rayleigh flat fading environment with no channel state information at the receiver and the transmitter. We show that, subject to the average power constraint, the support of the capacity achieving input distribution is bounded. Moreover, we show by a simpl...

In this paper we address the issue of universal or robust communication over quantum channels. Specifically, we consider memoryless communication scenario with channel uncertainty which is an analog of compound channel in classical information theory. We determine the quantum capacity of finite compound channels and arbitrary compound channels with...

We consider the broadcast phase of a three-node network, where a relay node establishes a bidirectional communication between two nodes using a spectrally efficient two-phase decode-and-forward protocol. In the first phase the two nodes transmit their messages to the relay node. Then the relay node decodes the messages and broadcasts a re-encoded c...

In this paper we extend recent coding results by Datta and Dorlas on classical capacity of averaged quantum channels with finitely many memoryless branches to arbitrary number of branches. Only assumption in our approach is that the channel satisfies some weak measurability properties. Our approach to the direct coding theorem is based on our previ...

We determine the capacity of compound classical quantum channels. The capacity result for compound channels demonstrates, as in the classical setting, the existence of reliable universal classical-quantum codes in scenarios where the only a priori information about the channel used for the transmission of information is that it belongs to a given s...

Discrete stationary classical processes as well as quantum lattice states are asymptotically confined to their respective typical support, the exponential growth rate of which is given by the (maximal ergodic) entropy. In the iid case the distinguishability of typical supports can be asymptotically specified by means of the relative entropy, accord...

In this paper, we consider ergodic causal classical-quantum channels (cq-channels) which additionally have a decaying input memory. In the first part, we develop some structural properties of ergodic cq-channels and provide equivalent conditions for ergodicity. In the second part, we prove the coding theorem with weak converse for causal ergodic cq...

In a three-node network bidirectional communication between two nodes can be enabled by a half-duplex relay node with a decode-and-forward protocol. In the first phase, the messages of two nodes are transmitted to the relay node. In the second phase a re-encoded composition is broadcasted by the relay node. In this work the capacity region of the b...

In our previous work we determined the weak capacity region for the broadcast phase of two-phase bidirectional relay channel. It turned out that the set of achievable rates obtained by optimizing over the two communication phases exceeds that obtained by using the network coding principle, i.e. by applying XOR to the decoded messages. In this paper...

In this contribution we describe some structural properties of ergodic classical-quantum channels and provide several equivalent conditions of ergodicity of such channels. In the second part we sketch the coding theorem with the weak converse for ergodic input-memoryless causal classical-quantum channels. Full proofs and several extensions of the r...

In this work, the capacity region of the broadcast channel in a two phase bidirectional relay communication scenario is proved. Thereby, each receiving node has perfect knowledge about the message intended for the other node. The capacity region can be achieved using an auxiliary random variable taking two values, i.e., by the principle of time-sha...

In a three-node network a half-duplex relay node enables bidirectional communication between two nodes with a spectral efficient two phase protocol. In the first phase, two nodes transmit their message to the relay node, which decodes the messages and broadcast a re-encoded composition in the second phase. In this work we determine the capacity reg...

We consider ergodic causal classical-quantum channels (cq-channels) which additionally have a decaying input memory. In the first part we develop some structural properties of ergodic cq-channels and provide equivalent conditions for ergodicity. In the second part we prove the coding theorem with weak converse for causal ergodic cq-channels with de...

We describe the structure of optimal Input covariance matrices for single user multiple-input/multiple-output (MIMO) communication system with covariance feedback and for general correlated fading. Our approach is based on the novel concept of right commutant and recovers previously derived results for the Kronecker product models. Conditions are d...

We present our recent results on limit theorems for quantum entropies and their applications in quantum information theory. They include the full extensions of the fundamental asymptotic equipartition property (AEP) to ergodic quantum informations sources and the ergodic version of Stein¿s Lemma on quantum hypothesis testing. These limit theorems...

The projective Hilbert space carries a natural symplectic structure which enables one to reformulate quantum dynamics as a classical Hamiltonian one.

We extend the data compression theorem to the case of ergodic quantum information sources. Moreover, we provide an asymptotically optimal compression scheme which is based on the concept of high probability subspaces. The rate of this compression scheme is equal to the von Neumann entropy rate.

We present a quantum version of Sanov's theorem focussing on a hypothesis testing aspect of the theorem: There exists a sequence of typical subspaces for a given set Ψ of stationary quantum product states asymptotically separating them from another fixed stationary product state. Analogously to the classical case, the separating rate on a logarithm...

We prove the ergodic version of the quantum Steins lemma which was conjectured by Hiai and Petz. The result provides an operational and statistical interpretation of the quantum relative entropy as a statistical measure of distinguishability, and contains as a special case the quantum version of the Shannon-McMillan theorem for ergodic states. A ve...

In der vorliegenden Dissertationsschrift werden einige Grenzwertsätze für die mittlere von-Neumann-Entropie und die mittlere relative Entropie für ergodische Quantenzustände auf quasi-lokalen C*-Algebren bewiesen. Für die mittlere von-Neumann-Entropie konnte bewiesen werden, dass das vollständige quantenmechanische Analogon des Satzes von Shannon-M...

We derive the monotonicity of the quantum relative entropy by an elementary operational argument based on Stein's lemma in quantum hypothesis testing. For the latter we present an elementary and short proof that requires the law of large numbers only. Joint convexity of the quantum relative entropy is proven too, resulting in a self-contained eleme...

We prove the ergodic version of the quantum Stein's lemma which was conjectured by Hiai and Petz. The result provides an operational and statistical interpretation of the quantum relative entropy as a statistical measure of distinguishability, and contains as a special case the quantum version of the Shannon-McMillan theorem for ergodic states. A v...

We extend the data compression theorem to the case of ergodic quantum information sources. Moreover, we provide an asymptotically optimal compression scheme which is based on the concept of high probability subspaces. The rate of this compression scheme is equal to the von Neumann entropy rate.

We give an equivalent finitary reformulation of the classical Shannon-McMillan-Breiman theorem which has an immediate translation to the case of ergodic quantum lattice systems. This version of a quantum Breiman theorem can be derived from the proof of the quantum Shannon-McMillan theorem presented in our previous work (math.DS/0207121).

We extend the data compression theorem to the case of ergodic quantum information sources. Moreover, we provide an asymptotically optimal compression scheme which is based on the concept of high probability subspaces. The rate of this compression scheme is equal to the von Neumann entropy rate.

We formulate and prove a quantum Shannon-McMillan theorem. The theorem demonstrates the significance of the von Neumann entropy for translation invariant ergodic quantum spin systems on n-dimensional lattices: the entropy gives the logarithm of the essential number of eigenvectors of the system on large boxes. The one-dimensional case covers quantu...

We give a self-contained, new proof of the monotonicity of the quantum relative entropy which seems to be natural from the point of view of quantum information theory. It is based on the quantum version of Stein's lemma which provides an operational interpretation of the quantum relative entropy.

We derive a regularized formula for the common randomness assisted entanglement transmission capacity of finite arbitrarily varying quantum channels (AVQC's). For finite AVQC's with positive capacity for classical message transmission we show, by derandomization through classical forward communication, that the random capacity for entanglement tran...