Reliable multicast with pipelined network coding using opportunistic feeding and routing

Multicast is an important mechanism in modern wireless networks and has attracted significant efforts to improve its performance with different metrics including throughput, delay, energy efficiency, etc. Traditionally, an ideal loss-free channel model is widely used to facilitate routing protocol design. However, the quality of wireless links is affected or even jeopardized resulting in transmission failures by many factors like collisions, fading or the noise of environment. In this paper, we propose a reliable multicast protocol, called CodePipe, with energy-efficiency, high throughput and fairness in lossy wireless networks. Building upon opportunistic routing and random linear network coding, CodePipe can not only eliminate coordination between nodes, but also improve the multicast throughput significantly by exploiting both intra-batch and inter-batch coding opportunities. In particular, four key techniques, namely, LP-based opportunistic routing structure, opportunistic feeding, fast batch moving and inter-batch coding, are proposed to offer significant improvement in throughput, energy-efficiency and fairness.Moreover, we design an efficient online extension of CodePipe such that it can work in a dynamic network where nodes join and leave the network as time progresses. We evaluate CodePipe on ns2 simulator by comparing with other two state-of-art multicast protocols,MORE and Pacifier. Simulation results show that CodePipe significantly outperforms both of them.

Loss of periodicity in breeding success of waders links to changes in lemming cycles in Arctic ecosystems

Lemming population cycles in the Arctic have an important impact on the Arctic food web, indirectly also affecting breeding success in Arctic-nesting birds through shared predators. Over the last two decades lemming cycles have changed in amplitude and even disappeared in parts of the Arctic. To examine the large scale effect of these recent changes we re-analysed published data from the East Atlantic Flyway (EAF), where a relationship between lemming cycles and wader breeding success was earlier found, and new data on breeding success of waders in the East Asian-Australasian Flyway (EAAF). We found that 1) any long-term periodicities in wader breeding success existed only until the year 2000 in the EAAF and until the 1980s in the EAF; 2) studying these patterns at a smaller spatial scale, where the Siberian-Alaskan breeding grounds were divided into five geographical units largely based on landscape features, breeding success of waders from the EAAF was not correlated to an index of predation pressure, but positively correlated to Arctic summer temperatures in some species. We argue that fading out of lemming cycles in some parts of the Arctic is responsible for faltering periodicity in wader breeding success along both flyways. These changed conditions have not yet resulted in any marked changing trends in breeding success across years, and declining numbers of waders along the EAAF are therefore more likely a result of changing conditions at stop-over and wintering sites.

There will be no more night

Exploring how the body and light are connected in interdisciplinary practice, in this work I make sound design and moving image re inscribing physical yet out of body experiences of light in near death – recorded from youtube. The image of fading light is in real time and constitutes a symbolic interpretation of eternity mirroring the audio. This work has been curated into a group exhibition at ‘Strange Neighbour’ alongside internationally recognised artists such as Peter Booth and Sam Shmith. The work has also been curated in my solo exhibition by Conny Dietzschold and is the subject of the essay in the catalogue by Sean Redmond and was presented in my paper ‘Motion and stillness: a bodily approach to photography.’ and is mentioned in the journal article to be published titled ‘Technology as Collaborator in Somatic Photographic Practice.’ Intellect Books

Channel estimation for time-varying MIMO relay systems

In this paper, we investigate the channel estimation problem for multiple-input multiple-output (MIMO) relay communication systems with time-varying channels. The time-varying characteristic of the channels is described by the complex-exponential basis expansion model (CE-BEM). We propose a superimposed channel training algorithm to estimate the individual first-hop and second-hop time-varying channel matrices for MIMO relay systems. In particular, the estimation of the second-hop time-varying channel matrix is performed by exploiting the superimposed training sequence at the relay node, while the first-hop time-varying channel matrix is estimated through the source node training sequence and the estimated second-hop channel. To improve the performance of channel estimation, we derive the optimal structure of the source and relay training sequences that minimize the mean-squared error (MSE) of channel estimation. We also optimize the relay amplification factor that governs the power allocation between the source and relay training sequences. Numerical simulations demonstrate that the proposed superimposed channel training algorithm for MIMO relay systems with time-varying channels outperforms the conventional two-stage channel estimation scheme.

Queering archives: intimate tracings

In the longer introduction of Radical History Review’s two thematic issues “Queering Archives,” we frame the archive as an evasive and dynamic space animated by the tensions of knowledge production, absence, and presence. As Jeffrey Weeks argued in RHR in 1979, “The evolution of sexual meanings and identities that we have traced over the past hundred years or so are by no means complete.”1 Fragments of information float unfixed — historically unraveled — and we form archives when we pull the fragments into the orbit of efforts to know. Yet the business of knowing is unsteady, as scholars of sexuality and gender have amply demonstrated. Between the fraught and necessary practices of historicization, anachronism, interpretation, bias, and partial readings that propel historical scholarship, archival fragments fall in and out of the frame of an easily perceptible knowledge. Queer historical knowledge thus is evasive — like a coin dropped in the ocean and for which one grasps, reaching it only for it to slip away again, rolling deeper into the beyond. To say that the knowledge work of animating queer historical fragments is marked by such slipperiness is to underline how the archive negotiates the decomposition and recomposition of knowledge’s materials. We pull and push at the fading paper, the fraying fabric, the photographs bleaching into their backgrounds, and manipulate technologies on their way to obsolescence, all as part of some suturing effort of one kind or another.

Superimposed channel training algorithm for time-varying MIMO relay systems

Two-way relaying systems are known to be capable of providing higher spectral efficiency compared with one-way relaying systems. However, the channel estimation problem for two-way relaying systems becomes more complicated. In this paper, we propose a superimposed channel training scheme for two-way MIMO relay communication systems, where the individ-ual channel information for users-relay and relay-users links are estimated. The optimal structure of the source and relay training sequences are derived when the mean-squared error (MSE) of channel estimation is minimized. We also optimize the power allocation between the source and relay training sequences to improve the performance of the algorithm. Numerical examples are shown to demonstrate the performance of the proposed channel training algorithm.

Comparative assessment of denim garments treated with laser bleaching and enzymatic bleaching methods

The performance of denim garments was evaluated after laser bleaching and enzymatic bleaching. Laser is an eco-friendly way to bleach the denim garment, and the color-fading of denim garments treated with laser and enzymatic bleaching was examined in this study.

Streaming analysis in wireless sensor networks

Two new incremental models for online anomaly detection in data streams at nodes in wireless sensor networks are discussed. These models are incremental versions of a model that uses ellipsoids to detect first, second, and higher-ordered anomalies in arrears. The incremental versions can also be used this way but have additional capabilities offered by processing data incrementally as they arrive in time. Specifically, they can detect anomalies 'on-the-fly' in near real time. They can also be used to track temporal changes in near real-time because of sensor drift, cyclic variation, or seasonal changes. One of the new models has a mechanism that enables graceful degradation of inputs in the distant past (fading memory). Three real datasets from single sensors in deployed environmental monitoring networks are used to illustrate various facets of the new models. Examples compare the incremental version with the previous batch and dynamic models and show that the incremental versions can detect various types of dynamic anomalies in near real time.