David Murray

This paper provides real-world measurements based on experiments with LoRaWAN. We also detail our motivation and methods for reliably transporting image data over LoRaWAN. This paper initially situates LoRa among existing and emerging wireless link types and provides a primer for those experienced with traditional wireless technologies. Some unique measurements, based on experiments, show the real-world relationship between payload size, spreading factor and airtime to demonstrate the characteristics of LoRaWAN. Furthermore, data on the reliability of transmissions given different payload sizes and the benefits of multiple overhearing gateways is provided. Finally, the limits of LoRaWAN are explored by describing an approach to recover lost LoRaWAN frames efficiently. The efficient reliability mechanism enables the transport of images over LoRaWAN.

A large volume of research has been undertaken to improve short range mesh based sensor networks. This paper considers a contrasting, but less established, research position that long range single hop HF transmissions suit many applications. HF transmissions are, however, not without challenges and this paper details an experiment to evaluate the viability of using spatial diversity to mitigate the intermittent and cyclical availability of HF circuits. Four transmitting nodes were placed across Australia and six days of packet transmissions at 14 MHz were analysed. The findings support the use of spatial diversity to maximise HF circuit availability and the presence of redundant circuits suggests the system has the capacity to accommodate antenna radiation patterns that present nulls in return for targeted gain.

Network hosts in private enterprises require local connectivity without any external connections. These networks operated using TCP/IP protocol and require a private address space. This article proposes a novel algorithm for IPv4 address allocation for this type of networks. This algorithm can be used by educators of subnetting, ISPs, university students and researchers to simplify the process of IPv4 address allocation. A tool called Private Subnetting One (PS1) programmed under Java is introduced in this article. This tool can be used by network engineers or university tutors to explain complex subnetting problems to students in introductory networking courses, such as CCNA.

Increasing use of online backup services, as well as the popularity of user-generated content, has increased the demand for bandwidth. However, traffic generated by these applications can impact on the responsiveness of delay-sensitive applications if they receive a 'fair-share' of the available bandwidth. Less-than-Best-Effort TCP congestion control mechanisms aim to allow lower-priority applications to utilise excess bandwidth with minimum impact to regular TCP traffic. We evaluated the performance of six Less-than-Best-Effort congestion control algorithms in different scenarios in a Linux testbed, only three of which had existing implementations for modern operating systems. The findings of this study suggest that Nice provides background throughput comparable to that of regular TCP, while maintaining low queuing delay, while CAIA Delay-Gradient (CDG) has the least impact on regular TCP traffic, at the expense of reduced throughput.

Network Address Translation (NAT) allows multiple devices with private addresses to share one public address. NAT was mainly confined to home gateways, but with the exhaustion of the IPv4 address space, large-scale NATs have been deployed. Other technologies causing large-scale address sharing are on the rise as well (e.g. VPNs). Large-scale address sharing is problematic, since it limits the number of concurrent TCP connections and severely limits geolocation and geoblocking. We investigate the presence of large-scale address sharing in the Internet, including how frequently it occurs, in which types of organisations it occurs, where it occurs geographically, how many users share addresses, and whether its presence is linked to IPv4 address shortage. Our results show that there are thousands of addresses with significant large-scale sharing with up to a few thousand users sharing a single address. Most of this sharing occurs within ISPs, many of which are located in countries with IPv4 address shortage, indicating that large-scale NATs may be a consequence of IPv4 shortages.

Adapting web pages to cultural preferences has been shown to improve communication effectiveness. However, the lack of a set of research-based web design guidelines or best practices renders the creation of culturally tailored versions of a website a time-consuming, costly task which is rarely undertaken by designers. This research aims to develop guidelines for cross-cultural web design to overcome these issues. The authors' prior work has provided empirical data showing significant cultural differences in the usage of design web attributes. These are used to determine a relationship between design attributes, cultural factors, and HCI factors. The result is a synthesis of culturally specific design attributes and published theories of culture to create a set of website design guidelines. The development process involved five steps: evaluation of the usage of design elements between cultures, identification of prominent design elements, organisation of cultural factors, organisation of HCI factors, and finally development the cross-cultural design guidelines. It is hoped that these evidence and research based guidelines will ultimately enhance website usability for users from different cultural backgrounds.

Studies on the composition and nature of Internet protocols are crucial for continued research and innovation. This study used three different methods to investigate the presence and level of support for various Internet protocols. Internet traffic entering and exiting a university network was passively captured, anonymised and analysed to test protocol usage. Active tests probed the Internet's most popular websites and experiments on the default behaviour of popular client, server and mobile operating systems were performed to reconcile the findings of the passive data collection. These results are valuable to research areas, such as those using emulations and simulations, where realism is dependent on the accuracy of the underlying assumptions about Internet traffic. Prior work is leveraged to explore changes and protocol adoption trends. This study shows that the majority of Internet traffic is now encrypted. There has also been an increase in large UDP frames, which we attribute to the Google QUIC protocol. Support for TCP options such as Selective Acknowledgements (SACK) and Maximum Segment Size (MSS) can now be assumed. Explicit Congestion Notification (ECN) usage is still marginal, yet active measurement shows that many servers will support the protocol if requested. Recent IETF standards such as Multipath TCP and TCP Fast Open have small but measurable levels of adoption.

The majority of Internet traffic now involves wireless devices. Increasing use of online backup services and the popularity of user-generated content have increased the demand for bandwidth and may impact on delay-sensitive applications. Less-than-Best-Effort TCP congestion control mechanisms aim to minimise the impact of lower-priority applications on regular TCP traffic, but their performance over wireless networks is not well understood. We evaluate the performance of six Less-than-Best-Effort congestion control algorithms over 802.11n in a Linux testbed. We also consider the effect of high fixed-path delay on the performance of LBE mechanisms. The findings of this study suggest that Nice and CAIA Delay-Gradient (CDG) have the lowest impact on regular TCP traffic at low-delay settings, at the expense of reduced throughput. However, while CDG experiences even greater reductions to throughput in high-delay settings, Nice has a greater impact on regular traffic.

As new congestion control mechanisms are developed, their performance relative to existing mechanisms needs to be understood; in particular over wireless networks. This study aimed to evaluate existing TCP congestion control mechanisms using a comprehensive and reproducible methodology designed to be representative of real world usage of wireless networks. The study sought to investigate whether any existing mechanism could provide significant performance benefits over CUBIC and be recommended for adoption. The findings of this study showed that YeAH demonstrated an increase in throughput of 3%–5% over CUBIC, with no penalty to latency. While this small improvement may assist applications requiring the highest available performance, it is unlikely that it will provide a significant improvement over existing congestion control mechanisms. As such, it is the conclusion of this study that use of alternate congestion control mechanisms would not provide noticeable improvements in performance in most applications.

Over half of the transmission time in WiFi networks is dedicated to ensuring that errors are corrected or detected. Despite these mechanisms, many studies have concluded that frame error rates vary. An increased understanding of why frames are lost is a pragmatic approach to improving real world 802.11 throughput. The potential beneficiaries of this research, include rate control algorithms, Modulation and Coding Schemes, simulation models, frame size selection and 802.11 configuration guidelines. This paper presents a measurement study of the factors which correlate with packet loss in 802.11 WiFi. Both passive and active approaches were used to investigate how the frame size, modulation and coding scheme and airtime effect the loss rate. Overall, packet errors were high, but the size of frames were not a major determinant of the loss rate. The loss rate decreased with the airtime but at substantially lower rates than those suggested in simple packet error models. Future work will further try to isolate and investigate specific errors, such as head on collisions in the preamble.