Network coding-based survivability techniques for multi-hop wireless networks

Multi-hop Wireless Networks (MWN) have drawn a lot of attention in the last decade, and will continue to be a hot and active research area in the future also. MWNs are attractive because they require much less effort to install and operate (compared to wired networks), and provide the network users with the flexibility and convenience they need. However, with these advantages comes a lot of challenges. In this work, we focus on one important challenge, namely, network survivability or the network ability to sustain failures and recover from service interruption in a timely manner. Survivability mechanisms can be divided into two main categories; Protection and restoration mechanisms. Protection is usually favored over restoration because it usually provides faster recovery. However, the problem with traditional protection schemes is that they are very demanding and consume a lot of network resources. Actually, at least 50% of the used resources in a communication session are wasted in order to provide the destination with redundant information, which can be made use of only when a network failure or information loss occurs. To overcome this problem and to make protection more feasible, we need to reduce the used network resources to provide proactive protection without compromising the recovery speed. To achieve this goal, we propose to use network coding. Basically, network coding allows intermediate network nodes to combine data packets instead of just forwarding them as is, which leads to minimizing the consumed network resources used for protection purposes. In this work we give special attention to the survivability of many-to-one wireless flows, where a set of N sources are sending data units to a common destination T. Examples of such many-to-one flows are found in Wireless Mesh Networks (WMNs) or Wireless Sensor Networks (WSNs). We present two techniques to provide proactive protection to the information flow in such communication networks. First, we present a centralized approach, for which we derive and prove the sufficient and necessary conditions that allows us to protect the many-to-one information flow against a single link failure using only one additional path. We provide a detailed study of this technique, which covers extensions for more general cases, complexity analysis that proves the NP-completeness of the problem for networks with limited min-cuts, and finally performance evaluation which shows that in the worst case our coding-based protection scheme can reduce the useful information rate by 50% (i.e., will be equivalent to traditional protection schemes). Next, we study the implementation of the previous approach when all network nodes have single transceivers. In this part of our work we first present a greedy scheduling algorithm for the sources transmissions based on digital network coding, and then we show how analog network coding can further enhance the performance of the scheduling algorithm. Our second protection scheme uses deterministic binary network coding in a distributed manner to enhance the resiliency of the Sensors-to-Base information flow against packet loss. We study the coding efficiency issue and introduce the idea of relative indexing to reduce the coding coefficients overhead. Moreover, we show through a simulation study that our approach is highly scalable and performs better as the network size and/or number of sources increases. The final part of this work deals with unicast communication sessions, where a single source node S is transmitting data to a single destination node T through multiple hops. We present a different way to handle the survivability vs. bandwidth tradeoff, where we show how to enhance the survivability of the S-T information flow without reducing the maximum achievable S-T information rate. The basic idea is not to protect the bottleneck links in the network, but to try to protect all other links if possible. We divide this problem into two problems: 1) pre-cut protection, which we prove it to be NP-hard, and thus, we present an ILP and a heuristic approach to solve it, and 2) post-cut protection, where we prove that all the data units that are not delivered to T directly after the min-cut can be protected against a single link failure. Using network coding in this problem allows us to maximize the number of protected data units before and after the min-cut

Reliability analysis of triple modular redundancy system with spare

Hardware redundant fault-tolerant systems and the different design approaches are discussed. The reliability analysis of fault-tolerant systems is usually done under permanent fault conditions. With statistical data suggesting that up to 90% of system failures are caused by intermittent faults, the reliability analysis of fault-tolerant systems must concentrate more on this class of faults. In this work, a reconfigurable Triple Modular Redundancy (TMR) with spare system that differentiates between permanent and intermittent faults has been built. The reconfiguration process of this system depends on both the current status of its modules and their history. Based on this, a different approach for reliability analysis under intermittent fault conditions using Markov models is presented. This approach shows a much higher system reliability compared to other redundant and non-redundant configurations

A Bibliometric Analysis of Published Articles on Management Information Systems (MIS)

This paper aimed to explore trends in management information systems (MIS) research from 2017 to 2021 and compare their contributions based on different countries and authors. In particular, this study presents a bibliometric analysis of MIS highlighting key themes including, effective top MIS journals, authors, contributing countries, source types, sponsoring institutions, document languages, and subject areas, within the past five years. The data were chosen from Web of Science and Scopus databases based on defined search terms relating to MIS. Microsoft Excel 2016 was used to summarize bibliometric features, including the number of publications, subject areas and country contributions. Based on the search results, a total of 3624 papers were included. The results showed that most of the articles were published in journals and conferences, mainly in English. Additionally, most of the research in MIS was in the computer, engineering, medicine and management sciences fields and China contributed the largest percentage of articles (17%). The “Journal of Physics”and the“International Conference on Information Systems Development” had the highest publication number, while, the European Commission, the National Natural Science Foundation of China, and the National Science Foundation were the top funding institutions.The outcomes provide a global perspective of the MIS field, identifying the works that have had the greatest impact, the main study traditions or themes that have been explored in MIS studies. Structural analyses revealed changes in the MIS over time. The paper concluded with suggestions and accumulated knowledge for future study. Keywords: Bibliometric analysis, Information Systems, Management Information Systems, MIS field. DOI: 10.7176/IKM/11-4-14 Publication date:November 30th 2021

Dynamic Modeling Approach to Quantify Change Orders Impact on Labor Productivity

In construction projects, change orders are commonly faced. These change orders, which are issued by the owner, may cause interruption to the contractor\u27s work, resulting in damages such as loss of labor productivity, delay damages, and cost overruns which may lead to claims. The relationship between change orders and loss of labor productivity is not well understood because of the difficulty in linking the cause of the productivity loss to the change order. So, to receive compensation, the contractor needs to prove with a credible calculation that the productivity loss was a result of the change order issued by the owner. Compared to all available productivity loss quantification methods, the Measured Mile approach is considered the most acceptable and popular approach in litigation. In this study, loss of labor productivity due to change orders is studied using a system dynamics method. A system dynamics model is developed using Vensim Software, validated, and utilized to quantitatively measure the impact of the change in the project scope on labor productivity. Different road construction projects were analyzed using both methods: measured mile analysis and system dynamics model; then, the results from those two approaches were compared

A two-stage power amplifier design for ultra-wideband applications

In this paper, a two-stage 0.18 μm CMOS power amplifier (PA) for ultra-wideband (UWB) 3 to 5 GHz based on common source inductive degeneration with an auxiliary amplifier is proposed. In this proposal, an auxiliary amplifier is used to place the 2nd harmonic in the core amplified in order to make up for the gain progression phenomena at the main amplifier output node. Simulation results show a power gain of 16 dB with a gain flatness of 0.4 dB and an input 1 dB compression of about -5 dBm from 3 to 5 GHz using a 1.8 V power supply consuming 25 mW. Power added efficiency (PAE) of around 47% at 4 GHz with 50 Ω load impedance was also observed

Inside the Black Box of Search Algorithms

A behind-the-scenes look at the algorithms that rank results in Bloomberg Law, Fastcase, Lexis Advance, and Westlaw

Inside the Black Box of Search Algorithms

A behind-the-scenes look at the algorithms that rank results in Bloomberg Law, Fastcase, Lexis Advance, and Westlaw