Zero-Delay Joint Source-Channel Coding in the Presence of Interference Known at the Encoder

Zero-delay transmission of a Gaussian source over an additive white Gaussian noise (AWGN) channel is considered in the presence of an additive Gaussian interference signal. The mean squared error (MSE) distortion is minimized under an average power constraint assuming that the interference signal is known at the transmitter. Optimality of simple linear transmission does not hold in this setting due to the presence of the known interference signal. While the optimal encoder-decoder pair remains an open problem, various non-linear transmission schemes are proposed in this paper. In particular, interference concentration (ICO) and one-dimensional lattice (1DL) strategies, using both uniform and non-uniform quantization of the interference signal, are studied. It is shown that, in contrast to typical scalar quantization of Gaussian sources, a non-uniform quantizer, whose quantization intervals become smaller as we go further from zero, improves the performance. Given that the optimal decoder is the minimum MSE (MMSE) estimator, a necessary condition for the optimality of the encoder is derived, and the numerically optimized encoder (NOE) satisfying this condition is obtained. Based on the numerical results, it is shown that 1DL with nonuniform quantization performs closer (compared to the other schemes) to the numerically optimized encoder while requiring significantly lower complexity

On Reliability-Aware Server Consolidation in Cloud Datacenters

In the past few years, datacenter (DC) energy consumption has become an important issue in technology world. Server consolidation using virtualization and virtual machine (VM) live migration allows cloud DCs to improve resource utilization and hence energy efficiency. In order to save energy, consolidation techniques try to turn off the idle servers, while because of workload fluctuations, these offline servers should be turned on to support the increased resource demands. These repeated on-off cycles could affect the hardware reliability and wear-and-tear of servers and as a result, increase the maintenance and replacement costs. In this paper we propose a holistic mathematical model for reliability-aware server consolidation with the objective of minimizing total DC costs including energy and reliability costs. In fact, we try to minimize the number of active PMs and racks, in a reliability-aware manner. We formulate the problem as a Mixed Integer Linear Programming (MILP) model which is in form of NP-complete. Finally, we evaluate the performance of our approach in different scenarios using extensive numerical MATLAB simulations.Comment: International Symposium on Parallel and Distributed Computing (ISPDC), Innsbruck, Austria, 201

Distributed VNF Scaling in Large-scale Datacenters: An ADMM-based Approach

Network Functions Virtualization (NFV) is a promising network architecture where network functions are virtualized and decoupled from proprietary hardware. In modern datacenters, user network traffic requires a set of Virtual Network Functions (VNFs) as a service chain to process traffic demands. Traffic fluctuations in Large-scale DataCenters (LDCs) could result in overload and underload phenomena in service chains. In this paper, we propose a distributed approach based on Alternating Direction Method of Multipliers (ADMM) to jointly load balance the traffic and horizontally scale up and down VNFs in LDCs with minimum deployment and forwarding costs. Initially we formulate the targeted optimization problem as a Mixed Integer Linear Programming (MILP) model, which is NP-complete. Secondly, we relax it into two Linear Programming (LP) models to cope with over and underloaded service chains. In the case of small or medium size datacenters, LP models could be run in a central fashion with a low time complexity. However, in LDCs, increasing the number of LP variables results in additional time consumption in the central algorithm. To mitigate this, our study proposes a distributed approach based on ADMM. The effectiveness of the proposed mechanism is validated in different scenarios.Comment: IEEE International Conference on Communication Technology (ICCT), Chengdu, China, 201

Zero-delay source-channel coding

In this thesis, we investigate the zero-delay transmission of source samples over three different types of communication channel models. First, we consider the zero-delay transmission of a Gaussian source sample over an additive white Gaussian noise (AWGN) channel in the presence of an additive white Gaussian (AWG) interference, which is fully known by the transmitter. We propose three parameterized linear and non-linear transmission schemes for this scenario, and compare the corresponding mean square error (MSE) performances with that of a numerically optimized encoder, obtained using the necessary optimality conditions. Next, we consider the zero-delay transmission of a Gaussian source sample over an AWGN channel with a one-bit analog-to-digital (ADC) front end. We study this problem under two different performance criteria, namely the MSE distortion and the distortion outage probability (DOP), and obtain the optimal encoder and the decoder for both criteria. As generalizations of this scenario, we consider the performance with a K-level ADC front end as well as with multiple one-bit ADC front ends. We derive necessary conditions for the optimal encoder and decoder, which are then used to obtain numerically optimized encoder and decoder mappings. Finally, we consider the transmission of a Gaussian source sample over an AWGN channel with a one-bit ADC front end in the presence of correlated side information at the receiver. Again, we derive the necessary optimality conditions, and using these conditions obtain numerically optimized encoder and decoder mappings. We also consider the scenario in which the side information is available also at the encoder, and obtain the optimal encoder and decoder mappings. The performance of the latter scenario serves as a lower bound on the performance of the case in which the side information is available only at the decoder.Open Acces

Edge-Interior Gradient Effects on the Understorey Bird Community in an Isolated Ayer Hitam Forest Reserve, Malaysia

The fact that the world is losing its biodiversity due to human activities, particularly around the tropical forest region, has been widely known. One of the biggest threats to biodiversity is the edge effects, especially in isolated and fragmented habitats. Thus, to investigate the edge effects on the community of understorey birds, an isolated tropical rain forest of Malaysia was chosen. The objectives of this study were: (1) to examine the species composition, richness, abundance, and density changes across edge-interior gradient; (2) to detect any distinct bird communities associated with certain habitat types and the factors affecting the association (3) to distinguish the interior and edge specialist species and guilds. The point-count sampling method was used in a 1248-ha lowland rain forest patch of Ayer Hitam Forest Reserve to carry out a survey on the individual understorey bird and species, at each of the 93 survey points, between December 2006 and July 2008 Birds and environmental variables were recorded within a 25 m radius of each point. A total of 2263 observations, 72 species, representing 19 families were recorded in this study. The species composition, density, abundance, and diversity of birds showed some significant differences across the edge-interior gradient at the guild and species levels. Based on the bird-habitat association, along the edge-interior gradient, two groups were distinguished. These were the edge-specialist group which was positively correlated with ground cover, light intensity, shrub cover, temperature, and percentage of shrub cover between 0.5 and 2 m in height; meanwhile the interior-specialist group was highly sensitive to the forest edge and could indicate good habitat quality of forest interior with high humidity, dense canopy cover, high number of dead trees, high percentage of litter cover, and deep litter layer. At the guild level, the results showed that the terrestrial insectivores and sallying insectivores are sensitive to edge and have positive correlation with distance from the edge, leaf litter depth, canopy cover, and the number of tall trees (>10 m). The presence of some species such as the Yellow-vented Bulbul, Cream-vented Bulbul, and Plaintive Cuckoo was associated with high light intensity and shrub cover, which are the best indicators of the edge. Meanwhile, the presence of Short-tailed Babbler, Moustached Babbler, and Black-caped Babbler was associated with high relative humidity and leaf litter cover, which are the best indicators of forest interior. Changes in the micro-environment at the edge are a key factor to indicate the understorey avian responses to the edge-interior gradient. As edge specialists can be widely found in the matrix surrounding the patch, they require less conservation against being declined or endangered; i.e. they can be well managed in the matrix surrounding the forest patches. Interior-specialists, on the other hand, especially terrestrial insectivores, should be given the most attention in conservation of forest areas. From the conservation viewpoint, the forest remnants in the lowlands of Peninsular Malaysia are of considerable concern. Due to the characteristics including thick leaf litter layer, dense canopy cover, high number of dead trees, and high relative humidity, these remnants have the capability of supporting the understorey bird species sensitive to edge effects