Microstrip to parallel strip balun as spiral antenna feed

This paper presents the design and implementation of a microstrip to parallel strip balun which are frequently used as balanced antennas feed. This wideband balun transition is composed of a parallel strip which is connected to the spiral antenna and a microstrip line where the width of the ground plane is gradually reduced to eventually resemble the parallel strip. The taper accomplishes the mode and impedance transformation. This balun has significantly improved bandwidth characteristics. The entire circuit was fabricated on RT Duriod 5880 substrate. The circuit designs were simulated and optimised using CST Microwave Studio and the simulated results are compared with the measured results. The back-to-back microstrip to parallel strip has a return loss of better than 10 dB over a wide bandwidth from 1.75 to 15 GHz. The performance of the proposed balun was validated with the spiral antenna. The measured results were compared with the simulated results and it shows that the antenna operates well in wideband frequency range from 2.5 to 15 GHz

Effective link operation duration: a new routing metric for mobile ad hoc networks

The dynamic topology of mobile ad hoc networks (MANETs) is caused by node mobility and fading of the wireless link. Link reliability is often measured by the estimated lifetime and the stability of a link. In this paper we propose that the stability of a link can be represented by the time duration in which the two nodes at each end of a link are within each other’s transmission range and the fading is above an acceptable threshold. A novel routing metric, called effective link operation duration (ELOD), is proposed and implemented into AODV (AODV-ELOD). Simulation results show that proposed AODVELOD outperforms both AODV and the Flow Oriented Routing Protocol (FORP)

Ergodic capacity of the exponentially correlated slotted amplify and forward relay channel

In this paper we analyze the performance degradation of slotted amplify-and-forward protocol in wireless environments with high node density where the number of relays grows asymptotically large. Channel gains between source-destination pairs in such networks can no longer be independent. We analyze the degradation of performance in such wireless environments where channel gains are exponentially correlated by looking at the capacity per channel use. Theoretical results for eigenvalue distribution and the capacity are derived and compared with the simulation results. Both analytical and simulated results show that the capacity given by the asymptotic mutual information decreases with the network density

Deterministic diffraction loss modelling for novel broadband communication in rural environments

This paper presents a deterministic modelling approach to predict diffraction loss for an innovative Multi-User-Single-Antenna (MUSA) MIMO technology, proposed for rural Australian environments. In order to calculate diffraction loss, six receivers have been considered around an access point in a selected rural environment. Generated terrain profiles for six receivers are presented in this paper. Simulation results using classical diffraction models and diffraction theory are also presented by accounting the rural Australian terrain data. Results show that in an area of 900 m by 900 m surrounding the receivers, path loss due to diffraction can range between 5 dB and 35 dB. Diffraction loss maps can contribute to determine the optimal location for receivers of MUSA-MIMO systems in rural areas

Inter-Slice Mobility Management in 5G: Motivations, Standard Principles, Challenges and Research Directions

Mobility management in a sliced 5G network introduces new and complex challenges. In a network-sliced environment, user mobility has to be managed not only among different base stations or access technologies, but also among different slices. This motivates the need for new mobility management solutions, which, by convention are required to be standards-compliant. This article, presented as a tutorial, focuses on the problem of inter-slice mobility from the perspective of 3GPP standards for 5G. A detailed overview of the relevant 3GPP standard principles is provided. Accordingly, the key technical gaps, challenges and the corresponding research directions are identified towards achieving seamless inter-slice mobility within the current 3GPP network slicing framework

Inter-Slice Mobility Management in 5G: Motivations, Standard Principles, Challenges and Research Directions

Mobility management in a sliced 5G network introduces new and complex challenges. In a network-sliced environment, user mobility has to be managed among not only different base stations or access technologies but also different slices. Managing user mobility among slices, or inter-slice mobility, motivates the need for new solutions. This article, presented as a tutorial, focuses on the problem of inter-slice mobility from the perspective of 3GPP standards for 5G. It provides a detailed overview of the relevant 3GPP standard principles. Accordingly, key technical gaps, challenges, and corresponding research directions are identified toward achieving seamless inter-slice mobility within the current 3GPP network slicing framework

Using reflective writing and textual explanations to evaluate students' conceptual knowledge

BACKGROUND OR CONTEXT - Writing is one method used to prompt students to reflect on their own thought processes. Eliciting students’ explanations in the form of text, or writing, also provides lecturers with information about students’ thinking (Goncher, Boles, Jayalath, 2014; Boles, Goncher, Jayalath, 2015). Often in engineering courses, students adopt algorithmic problem-solving approaches without demonstrating conceptual reasoning. Adding a written, or explanatory component, to problems or questions is one approach that can elicit conceptual reasoning. PURPOSE OR GOAL - The purpose of this study was to identify and compare affordances of using students’ written explanations based the type of problem and response. This comparative study sought to answer two research questions, 1) How were the students’ textual answers different for the type of problem and requested explanations? and 2) What does the type and organization of the text of students’ explanations reveal about their conceptual knowledge? APPROACH - We analyzed students’ explanations for procedurally based problems in the statics discipline and conceptually based problems in the signal processing discipline. The first method used “process problems” that required students to explain, using only words, the process that they used to solve a statics homework problem. The second method utilized the Signals and Systems Concept Inventory items, and required students to provide a written explanation for their multiple-choice selection to each item. We categorized responses by the type of problem and structure of the written explanations to evaluate conceptual knowledge. DISCUSSION - We found that the structure of the text and type of problem provided different insights into students’ reasoning. The results showed that students approach learning in statics with varying emphasis placed on procedural and conceptual knowledge, and some students had difficulties explaining underlying concepts in signal processing and reverted to procedural explanations. Regardless of the type of problem, students that are able to get feedback on their thought processes can use the feedback to formatively evaluate their own understanding. RECOMMENDATIONS/IMPLICATIONS/CONCLUSION - Educators who incorporate or require students to reflect on their thinking through textual explanations can promote the revision of incorrect and/or inconsistent knowledge, leading to improved conceptual knowledge development. Assignments or activities that include more incidental writing will engage students in more freethinking and reflection (Essig et al., 2014;Hawkins, Coney, & Bystrom, 1996), and can lead to a richer understanding of technical concepts