Mihaly Varga

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Cooperative hybrid ARQ (HARQ) protocols have been widely studied in recent years and they were shown to provide higher efficiency than cooperative protocols. This paper proposes a joint design within which the HARQ protocol collaborates with the link adaptation functionality and the cooperative transmission scheme in order to adapt the behavior of the HARQ(More)
We propose a link adaptation algorithm for cooperative transmissions in an OFDMA-based wireless system. The algorithm aims at maximizing the spectral efficiency of a relay-aided communication link, while satisfying the block error rate constraints at both the relay and the destination nodes. The optimal solution would be to perform an exhaustive search over(More)
This paper proposes a practical approach to load balancing in heterogeneous wireless networks, which is based on the adaptation of the multiple knapsack problem to this specific scenario. Several algorithms capable of solving the knapsack problem are considered, namely a brute force, a dynamic programming and a greedy approach. The algorithms are evaluated(More)
In this paper, we propose a method to predict the block error rate performance of the wireless links in OFDM communication systems. Our approach relies on a performance prediction methodology that uses the mean mutual information per coded bit as quality measure. We make a simplification within this methodology such that, contrary to existing approaches,(More)
Nowadays the Always Best Connected paradigm becomes more and more important, but fulfilling the requirements of this paradigm is not an easy task. Providing ubiquitous connectivity in the particular case of intelligent transportation systems requires, in most of the cases, the joint usage of the transmission capacities offered by several wireless access(More)
To provide a high system performance, the link adaptation algorithms need an accurate method to predict the Block Error Rate (BLER) performance of a transmission on a given realization of the wireless multipath propagation channel. A promising BLER prediction technique is based on mean mutual information of the received bits (MI). The main objective of this(More)
The existence and importance of free radicals are well established both theoretically and in in vivo experiments. Methods and techniques are now available to demonstrate the formation of free radical metabolites of natural substances and xenobiotics. Theories of the biological effects of free radicals could be unified and used for a better understanding of(More)
A priority-based scheduling algorithm which exploits both the multi-user and cooperative diversity of a cell that uses cooperative-relaying is proposed and analysed. The proposed scheduling algorithm jointly performs resource allocation and link adaptation, trying to find the transmission scheme (cooperative or direct, coding rates and modulation orders)(More)
The paper analyzes the BER and spectral efficiency performances of convolutionally-coded square QAM constellations that map non-coded bits, besides the coded ones, in an OFDM environment that imposes a user bin with only 81 QAM payloadsymbols. It shows that the QAM constellations that map only coded bits using coding rates higher than 2/3 are outperformed ,(More)