31 research outputs found
Network Coding: Connections Between Information Theory And Estimation Theory
In this paper, we prove the existence of fundamental relations between
information theory and estimation theory for network-coded flows. When the
network is represented by a directed graph G=(V, E) and under the assumption of
uncorrelated noise over information flows between the directed links connecting
transmitters, switches (relays), and receivers. We unveil that there yet exist
closed-form relations for the gradient of the mutual information with respect
to different components of the system matrix M. On the one hand, this result
opens a new class of problems casting further insights into effects of the
network topology, topological changes when nodes are mobile, and the impact of
errors and delays in certain links into the network capacity which can be
further studied in scenarios where one source multi-sinks multicasts and
multi-source multicast where the invertibility and the rank of matrix M plays a
significant role in the decoding process and therefore, on the network
capacity. On the other hand, it opens further research questions of finding
precoding solutions adapted to the network level.Comment: IEEE Wireless Communications and Networking Conference (WCNC), April,
201
Piggybacking Codes for Network Coding: The High/Low SNR Regime
We propose a piggybacking scheme for network coding where strong source
inputs piggyback the weaker ones, a scheme necessary and sufficient to achieve
the cut-set upper bound at high/low-snr regime, a new asymptotically optimal
operational regime for the multihop Amplify and Forward (AF) networks
Network Coding Power Control Mechanisms for Time Varying Channels
In this paper, we propose a model for large scale fading channels via markov
process. We exploit the channel delay profile and the dependency between
channel states via a first order autoregressive model that cast insight to the
channel variations under fading and the closed form delay induced. We propose a
network-coding structure that can be employed to compensate for the channel
variations under fixed power and to the period of zero packet transmissions
under adaptive power control. Satellite communications is an application to the
model proposed
ANTI-MICROBIAL EVALUATION OF NEW THIAZOLO PYRIMIDINE DERIVATIVES
Twelve new heterocyclic compounds containing thiazolo pyrimidine moiety were thus synthesized.. Compound 2 was synthesized by reaction of α-amino naphthol 1 with potassium isothiocyanate. Reaction of compound 2 with sodium nitrite and hydrochloric acid afforded the corresponding diazonuim salt 3, which converted to 2-hydrazino thiazolo derivatives 4. Compound 2 carried out to synthesize imidazolo thiazolo derivative 5, 6 and thiazolo pyrimidino derivative 7, 8 and 9 respectively. Compound 4 was carried out to synthesize of compound 10. Compound 10 was carried out to synthesize of triazolo thiazolo and thiadiazolo derivatives 11 and 12 respectively. The structures of all newly synthesized compounds were elucidated by elemental analysis, IR, 1H-NMR and mass spectral data. The assignments of the new products were tested for Anti-microbial activities. Results are suggesting thiazolo pyrimidine derivatives emerge as valuable compounds with great potential to be used as antibacterial and antifungal agents, and as promising candidates for further efficiency evaluation. The detailed synthesis, spectroscopic data and Anti-microbial activities are reported
Energy Efficient Adaptive Network Coding Schemes for Satellite Communications
In this paper, we propose novel energy efficient adaptive network coding and
modulation schemes for time variant channels. We evaluate such schemes under a
realistic channel model for open area environments and Geostationary Earth
Orbit (GEO) satellites. Compared to non-adaptive network coding and adaptive
rate efficient network-coded schemes for time variant channels, we show that
our proposed schemes, through physical layer awareness can be designed to
transmit only if a target quality of service (QoS) is achieved. As a result,
such schemes can provide remarkable energy savings.Comment: Lecture Notes of the Institute for Computer Sciences, Social
Informatics and Telecommunications Engineering, 24 March 201
Network Coding Channel Virtualization Schemes for Satellite Multicast Communications
In this paper, we propose two novel schemes to solve the problem of finding a
quasi-optimal number of coded packets to multicast to a set of independent
wireless receivers suffering different channel conditions. In particular, we
propose two network channel virtualization schemes that allow for representing
the set of intended receivers in a multicast group to be virtualized as one
receiver. Such approach allows for a transmission scheme not only adapted to
per-receiver channel variation over time, but to the network-virtualized
channel representing all receivers in the multicast group. The first scheme
capitalizes on a maximum erasure criterion introduced via the creation of a
virtual worst per receiver per slot reference channel of the network. The
second scheme capitalizes on a maximum completion time criterion by the use of
the worst performing receiver channel as a virtual reference to the network. We
apply such schemes to a GEO satellite scenario. We demonstrate the benefits of
the proposed schemes comparing them to a per-receiver point-to-point adaptive
strategy