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@article{faucris.230034823,
abstract = {The half-duplex (HD) multi-hop relay channel consists of a source, multiple HD relays connected in series, and a destination where links are present only between adjacent nodes. In this paper, we focus on decode-and-forward relays and assume that the links are impaired by block fading and additive white Gaussian noise. We design a new protocol which, unlike the conventional protocols for the multi-hop relay channel, does not adhere to a fixed and predefined pattern of using the transmit, receive, and silent states of the nodes. In particular, the proposed protocol selects the optimal states of the nodes and the corresponding optimal transmission rates based on the instantaneous channel state information (CSI) of the involved links in each fading block such that the achievable average rate from source to destination is maximized. To enable adaptive scheduling of the states of the nodes, the relay nodes have to be equipped with buffers for temporary storage of the information received from the preceding node. Additionally, we discuss and address two practical challenges arising in the implementation of the optimal protocol, namely the unconstrained end-to-end delay due to data buffering at the relays and the required CSI overhead. Numerical results confirm the superiority of the proposed buffer-aided protocols compared to existing multi-hop relaying protocols.
},
author = {Grebenstein, Laura and Kirchner, Jens and Stavracakis Peixoto, Renata and Zimmermann, Wiebke and Irnstorfer, Florian and Wicke, Wayan and Ahmadzadeh, Arman and Jamali Kooshkghazi, Vahid and Fischer, Georg and Weigel, Robert and Burkovski, Andreas and Schober, Robert},
doi = {10.1109/TNB.2018.2870910},
faupublication = {yes},
journal = {IEEE Transactions on Nanobioscience},
keywords = {Microorganisms; Protons; Biomedical optical Imaging; Optical pumping; Optical Receivers; Optical sensors; Chemicals},
pages = {31-42},
peerreviewed = {Yes},
title = {{Biological} {Optical}-to-{Chemical} {Signal} {Conversion} {Interface}: {A} {Small}-scale {Modulator} for {Molecular} {Communications}},
volume = {18},
year = {2018}
}
@article{faucris.226935576,
abstract = {A simple diamond half-duplex relay network composed of a source, two decode-and-forward half-duplex relays, and a destination is considered, where a direct link between the source and the destination does not exist. For this network, we study the case of buffer-aided relays, where the relays are equipped with buffers. Each relay can receive data from the source, store it in the buffer, and forward it to the destination, when the channel conditions are advantageous. Thereby, buffering enables adaptive scheduling of the transmissions and receptions over time, which allows the network to exploit the diversity offered by the fading channels. For the considered half-duplex network, four transmission modes are defined based on whether the relay nodes receive or transmit. In this paper, we derive the locally optimal scheduling of the transmission modes over time and investigate the achievable average rate, when the relays are affected by inter-relay interference. Since the proposed buffer-aided transmission policies introduce unbounded delay, we provide a sub-optimal buffer-aided transmission policy with limited delay. Moreover, for inter-relay interference cancellation, we consider two coding schemes with different complexities. In the first scheme, we employ dirty paper coding, which entails a high complexity, whereas in the second scheme, we adopt a low-complexity technique based on successive interference cancellation at the receiving relay nodes and optimal power allocation at the transmitting nodes. Our numerical results show that the proposed protocols, with and without delay constraints, outperform existing protocols for the considered network from the literature.
transfer (SWIPT) systems employing a practical nonlinear radio frequency (RF) energy harvesting (EH)
receiver. In particular, we consider a three-node system with one transmitter that broadcasts a common
signal to separated information decoding (ID) and EH receivers. Owing to the nonlinearity of the EH
receiver circuit, the efficiency of wireless power transfer depends significantly on the waveform of the
transmitted signal. In this paper, we aim to answer the following fundamental question: What is the
optimal input distribution of the transmit waveform that maximizes the rate of the ID receiver for a
given required harvested power at the EH receiver? In particular, we study the capacity of a SWIPT
system impaired by additive white Gaussian noise (AWGN) under average-power (AP) and peak-power
(PP) constraints at the transmitter and an EH constraint at the EH receiver. Using Hermite polynomial
bases, we prove that the optimal capacity-achieving input distribution that maximizes the rate-energy
region is unique and discrete with a finite number of mass points. Our numerical results show that the
rate-energy region is enlarged for a larger PP constraint and that the rate loss of the considered SWIPT
system compared to the AWGN channel without EH receiver is reduced by increasing the AP budge},
author = {Morsi, Rania and Jamali Kooshkghazi, Vahid and Ng, Derrick Wing Kwan and Schober, Robert},
booktitle = {IEEE International Conference on Communications (ICC)},
date = {2018-05-20/2018-05-24},
doi = {10.1109/ICC.2018.8422269},
faupublication = {yes},
keywords = {AWGN channels;channel capacity;decoding;energy harvesting;optimisation;polynomials;radio receivers;radiofrequency power transmission;telecommunication power supplies;rate-energy region;nonlinear energy harvesting circuit;information-theoretic limits;wireless power transfer;SWIPT system;nonlinear radio frequency energy harvesting receiver;information decoding;additive white Gaussian noise;average-power constraint;peak-power constraint;Hermite polynomial;simultaneous wireless information and power transfer;Receivers;Radio frequency;Integrated circuit modeling;Rectennas;Transmitters;RF signals;AWGN channels},
peerreviewed = {unknown},
title = {{On} the {Capacity} of {SWIPT} {Systems} with a {Nonlinear} {Energy} {Harvesting} {Circuit}},
url = {https://ieeexplore.ieee.org/document/8422269/},
venue = {Kansas City, Missouri},
year = {2018}
}
@inproceedings{faucris.229312206,
abstract = {Although extensively investigated, the capacity of the two-hop half-duplex (HD) relay channel is not fully understood. In particular, a capacity expression which can be evaluated straightforwardly is not available and an explicit coding scheme which achieves the capacity is not known either. In this paper, we derive a new expression for the capacity of the two-hop HD relay channel based on a simplified converse. Compared to previous results, this capacity expression can be easily evaluated. Moreover, we propose an explicit coding scheme which achieves the capacity. To achieve the capacity, the relay does not only send information to the destination by transmitting information-carrying symbols but also with the zero symbols resulting from the relay's silence during reception. As examples, we compute the capacities of the two-hop HD relay channel for the cases when the source-relay and relay-destination links are both binary-symmetric channels (BSCs) and additive white Gaussian noise (AWGN) channels, respectively, and numerically compare the capacities with the rates achieved by conventional relaying where the relay receives and transmits in a codeword-by-codeword fashion and switches between reception and transmission in a strictly alternating manner. Our numerical results show that the capacities of the two-hop HD relay channel for BSC and AWGN links are significantly larger than the rates achieved with conventional relaying.