Jonas Hansen

CORE: COPE with MORE in Wireless Meshed Networks

State-of-the-art in network coding for wireless, meshed networks typically considers two problems separately. First, the problem of providing reliability for a single session. Second, the problem of opportunistic combination of flows by using minimalistic coding, i.e., by XORing packets from different flows. Instead of maintaining these approaches separate, we propose a protocol (CORE) that brings together these coding mechanisms. Our protocol uses random linear network coding (RLNC) for intra- session coding but allows nodes in the network to setup inter- session coding regions where flows intersect. Routes for unicast sessions are agnostic to other sessions and setup beforehand, CORE will then discover and exploit intersecting routes. Our approach allows the inter-session regions to leverage RLNC to compensate for losses or failures in the overhearing or transmitting process. Thus, we increase the benefits of XORing by exploiting the underlying RLNC structure of individual flows. This goes beyond providing additional reliability to each individual session and beyond exploiting coding opportunistically. Our numerical results show that CORE outperforms both forwarding and COPE-like schemes in general. More importantly, we show gains of up to 4 fold over COPE-like schemes in terms of transmissions per packet in one of the investigated topologies.

Network coded software defined networking: enabling 5G transmission and storage networks

Software defined networking has garnered large attention due to its potential to virtualize services in the Internet, introducing flexibility in the buffering, scheduling, processing, and routing of data in network routers. SDN breaks the deadlock that has kept Internet network protocols stagnant for decades, while applications and physical links have evolved. This article advocates for the use of SDN to bring about 5G network services by incorporating network coding (NC) functionalities. The latter constitutes a major leap forward compared to the state-ofthe- art store and forward Internet paradigm. The inherent flexibility of both SDN and NC provides fertile ground to envision more efficient, robust, and secure networking designs, which may also incorporate content caching and storage, all of which are key challenges of the upcoming 5G networks. This article not only proposes the fundamentals of this intersection, but also supports it with key use cases and a thorough performance evaluation on an implementation that integrated the Kodo library (NC) into OpenFlow (SDN). Our results on singlehop, multihop, and multi-path scenarios show that gains of 3x to 11x are attainable over standard TCP and multi-path TCP.

Stable intermediates determine proteins' primary unfolding sites in the presence of surfactants

Despite detailed knowledge of the overall structural changes and stoichiometries of surfactant binding, little is known about which protein regions constitute the preferred sites of attack for initial unfolding. Here we have exposed three proteins to limited proteolysis at anionic (SDS) and cationic (DTAC) surfactant concentrations corresponding to specific conformational transitions, using the surfactant‐robust broad‐specificity proteases Savinase and Alcalase. Cleavage sites are identified by SDS‐PAGE and N‐terminal sequencing. We observe well‐defined cleavage fragments, which suggest that flexibility is limited to certain regions of the protein. Cleavage sites for α‐lactalbumin and myoglobin correspond to regions identified in other studies as partially unfolded at low pH or in the presence of organic solvents. For Tnfn3, which does not form partially folded structures under other conditions, cleavage sites can be rationalized from the structure of the proteins folding transition state and the position of loops in the native state. Nevertheless, they are more sensitive to choice of surfactant and protease, probably reflecting a heterogeneous and fluctuating ensemble of partially unfolded structures. Thus, for proteins accumulating stable intermediates on the folding pathway, surfactants encourage the formation of these states, while the situation is more complex for proteins that do not form these intermediates.

Bridging inter-flow and intra-flow Network Coding for video applications: Testbed description and performance evaluation

Network Coding (NC) for Wireless Mesh Network (WMN) has received a lot of attention from the research community in recent years due to its ability to provide higher throughput, reliability, and efficiency in the use of the available wireless spectrum. NC has had two main research lines focused on inter-flow and intra-flow coding. However, these two domains have historically been studied separately. This paper proposes a testbed implementation of CORE, the first protocol to bridge both approaches such that the structure of intra-flow coding can be exploited during inter-flow coding to both enhance reliability, common of the former, while maintaining an efficient spectrum usage, typical of the latter. This paper uses the intuition provided in [1] to propose a practical implementation of the protocol leveraging Random Linear Network Coding (RLNC) for intra-flow coding, a credit based packet transmission approach to decide how much and when to send redundancy in the network, and a minimalistic feedback mechanism to guarantee delivery of generations of the different flows. Given the delay constraints of video applications, we proposed a simple yet effective coding mechanism, Block Coding On The Fly (BCFly), that allows a block encoder to be fed on-the-fly, thus reducing the delay to accumulate enough packets that is introduced by typical generation based NC techniques. Our measurements and comparison to forwarding and COPE show that CORE not only outperforms these schemes even for small packet losses, but that the gains can be of five fold and two orders of magnitude, respectively, for higher packet losses.

Sub-Transport Layer Coding: A Simple Network Coding Shim for IP Traffic

Packet losses in wireless networks dramatically curbs the performance of TCP. This paper introduces a simple coding shim that aids IP-layer traffic in lossy environments while being transparent to transport layer protocols. The proposed coding approach enables erasure correction while being oblivious to the congestion control algorithms of the utilised transport layer protocol. Although our coding shim is indifferent towards the transport layer protocol, we focus on the performance of TCP when ran on top of our proposed coding mechanism due to its widespread use. The coding shim provides gains in throughput that exceed 10x for TCP traffic while requiring a limited sacrifice in terms of fairness towards other flows on the channel.

On the construction of jointly superregular lower triangular Toeplitz matrices

Superregular matrices have the property that all of their submatrices, which can be full rank are so. Lower triangular superregular matrices are useful for e.g., maximum distance separable convolutional codes as well as for (sequential) network codes. In this work, we provide an explicit design for all superregular lower triangular Toeplitz matrices in GF(2p) for the case of matrices with dimensions less than or equal to 5 × 5. For higher dimensional matrices, we present a greedy algorithm that finds a solution provided the field size is sufficiently high. We also introduce the notions of jointly superregular and product preserving jointly superregular matrices, and extend our explicit constructions of superregular matrices to these cases. Jointly superregular matrices are necessary to achieve optimal decoding capabilities for the case of codes with a rate lower than 1/2, and the product preserving property is necessary for optimal decoding capabilities in network recoding.

Performance evaluation of coded meshed networks

We characterize the performance of intra- and inter-session network coding (NC) in wireless networks using real-life implementations. We compare this performance to a recently developed hybrid approach, called CORE, which combines intra- and inter-session NC exploiting the code structure of the former to enhance the gains of the latter. We first motivate our work through measurements in WiFi mesh networks. Later, we compare state-of-the-art approaches, e.g., COPE, RLNC, to CORE. Our measurements show the higher reliability and throughput of CORE over other schemes, especially, for asymmetric and/or high loss probabilities. We show that a store and forward scheme outperforms COPE under some channel conditions, while CORE yields 3dB gains.

Solid-phase synthesis of peptide β-aminoboronic acids

Peptide/boronic acid conjugates are attractive scaffolds for chemical probe discovery and drug design. There are only a few reactions that allow for rapid incorporation of boron into peptides. Herein, we report a new approach towards the synthesis of peptide β‐aminoboronic acids on solid support using 2‐chlorotrityl resin and solid‐phase peptide synthesis techniques with only one purification required. Evaluation of model compounds demonstrate the stability of peptide boronic acids toward degradation at physiological pH. This straightforward conjugation process should allow access to a wide range of peptide boronic acid scaffolds for both synthetic and medicinal use.

Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), 2013 IEEE 18th International Workshop on

Network Coding (NC) for Wireless Mesh Network (WMN) has received a lot of attention from the research community in recent years due to its ability to provide higher throughput, reliability, and efficiency in the use of the available wireless spectrum. NC has had two main research lines focused on inter-flow and intra-flow coding. However, these two domains have historically been studied separately. This paper proposes a testbed implementation of CORE, the first protocol to bridge both approaches such that the structure of intra-flow coding can be exploited during inter-flow coding to both enhance reliability, common of the former, while maintaining an efficient spectrum usage, typical of the latter. This paper uses the intuition provided in [1] to propose a practical implementation of the protocol leveraging Random Linear Network Coding (RLNC) for intra-flow coding, a credit based packet transmission approach to decide how much and when to send redundancy in the network, and a minimalistic feedback mechanism to guarantee delivery of generations of the different flows. Given the delay constraints of video applications, we proposed a simple yet effective coding mechanism, Block Coding On The Fly (BCFly), that allows a block encoder to be fed on-the-fly, thus reducing the delay to accumulate enough packets that is introduced by typical generation based NC techniques. Our measurements and comparison to forwarding and COPE show that CORE not only outperforms these schemes even for small packet losses, but that the gains can be of five fold and two orders of magnitude, respectively, for higher packet losses.