1,721,095 research outputs found
“Modello di Intervento per l’Individuazione dei Fabbisogni di Innovazione ed il Trasferimento Tecnologico”
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Diversity, Coding and Multiplexing Trade-Off of Network-Coded Wireless Cooperative Networks
No full textAbstract— In this paper, we study the performance of network– coded cooperative diversity systems with practical communica- tion constraints. More specifically, we investigate the interplay between diversity, coding, and multiplexing gain when the relay nodes do not act as dedicated repeaters, which only forward data packets transmitted by the sources, but they attempt to pursue their own interest by forwarding packets which contain a network–coded version of received and their own data. We provide a very accurate analysis of the Average Bit Error Prob- ability (ABEP) for two network topologies with three and four nodes, when practical communication constraints, i.e., erroneous decoding at the relays and fading over all the wireless links, are taken into account. Furthermore, diversity and coding gain are studied, and advantages and disadvantages of cooperation and binary Network Coding (NC) are highlighted. Our results show that the throughput increase introduced by NC is offset by a loss of diversity and coding gain. It is shown that there is neither a coding nor a diversity gain for the source node when the relays forward a network–coded version of received and their own data. Compared to other results available in the literature, the conclusion is that binary NC seems to be more useful when the relay nodes act only on behalf of the source nodes, and do not mix their own packets to the received ones. Analytical derivation and findings are substantiated through extensive Monte Carlo simulations
Network Code Design from Unequal Error Protection Coding: Channel-Aware Receiver Design and Diversity Analysis
No full textIn this paper, we propose Unequal Error Protection (UEP) coding theory as a viable and flexible method for the design of network codes for multi-source multi-relay cooperative networks. As opposite to state-of-the-art solutions available for improving the diversity gain of cooperative networks, it is shown that the proposed method allows us to assign each source node the desired diversity gain, according to, e.g., the requested Quality of Service (QoS) or power constraints. The diversity advantage of the UEP-based network code design over conventional relay-only and XOR-only solutions is shown for the canonical two-source two-relay network. Furthermore, Maximum-Likelihood (ML-) optimum channel-aware receivers for multi-source multi-relay cooperative networks are developed, and their Average Bit Error Probability (ABEP) and achievable diversity over fading channels analytically studied. It is shown that only a cross-layer (joint) implementation of demodulation and network-decoding allows the destination to fully exploit the diversity inherently provided by the distributed network code. Finally, analytical derivations and findings are substantiated via Monte Carlo simulations
Error Performance and Diversity Analysis of Multi-Source Multi-Relay Wireless Networks with Binary Network Coding and Cooperative MRC
No full textIn this paper, we contribute to the theoretical understanding, the design, and the performance evaluation of multi-source multi-relay network-coded cooperative diversity protocols. These protocols are useful to counteract the spectral inefficiency of repetition-based cooperation. We provide a general analytical framework for analysis and design of wireless networks using the Demodulate-and-Forward (DemF) protocol with binary Network Coding (NC) at the relays and Cooperative Maximal Ratio Combining (C-MRC) at the destination. Our system model encompasses an arbitrary number of relays which offer two cooperation levels: i) full-cooperative relays, which postpone the transmission of their own data frames to help the transmission of the sources via DemF relaying and binary NC; and ii) partial-cooperative relays, which exploit NC to transmit their own data frames along with the packets received from the sources. The relays can apply NC on different subsets of sources, which is shown to provide the sources with unequal diversity orders. Guidelines to choose the packets to be combined, i.e., the network code, to achieve the desired diversity order are given. Our study shows that partial-cooperative relays provide no contribution to the diversity order of the sources. Theoretical findings and design guidelines are validated through extensive Monte Carlo simulations
On Diversity Order and Coding Gain of Multisource Multirelay Cooperative Wireless Networks With Binary Network Coding
No full textIn this paper, a multisource multirelay cooperative wireless network with binary modulation and binary network coding is studied. The system model encompasses 1) a Demodulate-and-Forward (DemF) protocol at the relays, where the received packets are forwarded, regardless of their reliability, and 2) a maximum-likelihood optimum demodulator at the destination, which accounts for possible demodulation errors at the relays. An asymptotically tight and closed-form expression of the end-to-end error probability is derived, which showcases the diversity order and coding gain of each source. Unlike other papers available in the literature, the proposed framework has three main distinguishable features: 1) It is useful for general network topologies and arbitrary binary encoding vectors; 2) it shows how network code and two-hop forwarding protocol affect diversity order and coding gain; and 3) it accounts for realistic fading channels and demodulation errors at the relays. The framework provides four main conclusions: 1) Each source achieves a diversity order equal to the separation vector of the network code; 2) the design of diversity-achieving network codes is equivalent to the design of systematic block codes over fully interleaved point-to-point links; 3) the coding gain of each source decreases with the number of mixed packets at the relays; and 4) if the destination cannot take into account demodulation errors at the relays, it loses approximately half of the diversity order. Our theoretical findings are validated through extensive Monte Carlo simulations
Autophagy inhibitors in the treatment of colorectal cancer: a brief review
Full text linkColorectal cancer (CRC) is the third most frequent cancer. The first-line adjuvant or neoadjuvant chemotherapy is represented by 5-fluorouracil (5-FU) but its application is limited due to induction of chemoresistance. Recent studies showed that the 5-FU resistance in CRC is closely related to the activation of autophagy. During human carcinogenesis, autophagy has been demonstrated to play opposite roles of inhibitor or promoter of malignant progression depending on initial or advanced stages of growth. Currently, the autophagy inhibitor chloroquine (CQ) and its derivate, hydroxychloroquine (HCQ), are the only Food and Drug Administration (FDA)-approved drugs for clinical use. This review summarizes recent findings on the possible employment of autophagy inhibitors to overcome chemoresistance engaged in the CRC
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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