Terry Koziniec

Global communications without reliance on an engineered communications network make the ionosphere an attractive medium for wireless sensors in remote deployments. However, ionospheric circuits’ temporary availability is a challenge in scheduling transmissions for a sensor with limited power, communications and computational capacity, particularly where cost and antenna constraints limit operation to a single frequency. We describe a technique for scheduling transmissions based on precomputed propagation models. The models predict the time-varying Signal to Noise Ratio (SNR) at the receiver. We describe methods to determine threshold SNR values, using the Weak Signal Propagation Reporter (WSPR) database to determine if a time slot is suitable for transmission.Two techniques are investigated to quantify the failed receptions: the Inverse Square Law method uses a statistical approach and a sampling measurement technique called Goldilocks. The two approaches yielded threshold SNR values of −21 dB and −19 dB, respectively, for a time slot with a 90% successful reception goal. Applying these thresholds to the modelled SNR, we generate a precomputed hourly transmission schedule. With the schedule determined monthly, a 12-month plan requires 36 bytes of wireless sensor storage. A six-day experiment, using a 1677 km path, found that the schedule resulted in an 83% reception rate when used with a power level of 200 mW.

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.

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.

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.

Flipped learning has been the subject of significant hype and attention but descriptions of the development and the evaluation of this pedagogical model are lacking. Flipped learning is an inverted teaching approach where students learn the basics via short videos at home, then come to class to complete challenges and clarify any misunderstandings. This paper describes how an IT unit was delivered using the flipped learning approach. A survey was used to determine how students perceived flipped learning. Students were generally positive about the approach, particularly the convenience and flexibility of the flipped videos. Although face to face teaching time was reduced in this flipped learning implementation, students felt that they interacted more with their instructors and peers. Students felt strongly positive to walkthroughs and were mixed as to the need for the instructors face. Significant efforts to produce high quality and engaging videos were made, but the survey suggested that students learnt the most during tutorial time. The relative importance of interactive tutorials is congruent with a large body of research and pedagogical approaches advocating the importance of active student-centred learning.

The Ethernet speed has increased to 40–100 Gbps since the release of IEEE P802.3ba. In this paper, we have extended the Intel's Large Receive Offload Linux software driver function to process the UDP/IP packets and to manage the out-of-order packets as well as design a scalable programmable Network Interface-based RISC core to support these functions in the Network Interface. The processing methodology and cycle processing of UDP packets inside the Network Interface are also discussed. Besides, the three-pipeline RISC's performance and data movements for high communication rates up to 100 Gbps have been measured too. The results presented herein show that an 800 MHz cost-effective embedded processor core can provide the required efficiency of the network interface to support a wide range of transmission line speeds, up to 100 Gbps. Furthermore, we have found several techniques that can contribute to packet processing and work with fewer headers and data transferring in a network interface.

The Ethernet speed has increased to 40-100 Gbps since the release of IEEE P802.3ba. In this paper, we have enhanced the Intel's Large Receive Offload Linux software driver function to manage the out-of-order packets and designed a scalable Network Interface based RISC core to support this function in the Network Interface. The RISC's performance and data movements for high communication rates up to 100 Gbps have been measured, and the results presented herein show that a cost-effective embedded RISC core can provide the required efficiency of the network interface to support a wide range of transmission line speeds, up to 100 Gbps. Furthermore, we have found several techniques that can contribute to packet processing and work with fewer headers and less data copying in a host memory.

Ethernet data rates have increased many orders of magnitudes since standardisation in 1982. Despite these continual data rates increases, the 1500 byte Maximum Transmission Unit (MTU) of Ethernet remains unchanged. Experiments with varying latencies, loss rates and transaction lengths are performed to investigate the potential benefits of Jumboframes on the Internet. This study reveals that large MTUs offer throughputs much larger than a simplistic overhead analysis might suggest. The reasons for these higher throughputs are explored and discussed.

The Ethernet speed has increased sending and receiving frames from 40 to 100 Gbps after the IEEE P802.3ba released. The industry and academia have focused scaling up the TCP/IP protocol processing for 40-100 Gbps. LSO is a de facto standard, which is offloaded to network interface for sending packets up to 10 Gbps. It not clears whether a network interface can support such function for new 40-100 Gbps. The widely use of the hardware-based NIC such as the use of a fully customized logic based network interface can be due to the following reasons; Still it is not clear whether the General Purpose Processor (GPP) can provide the processing required for high-speed line beyond the 10 Gbps. Also, the limit of the GPP's clock in supporting the processing of network interfaces. However, using a RISC core engine for offloading the LSO function can deliver some important features to network interfaces design, such as simplicity, scalability, shorter developing cycle time. In this paper, we have investigated using a specialized RISC core to process the LSO functions for TCP/IP and UDP/IP for high-speed communications rate up to 100 Gbps. To achieve this, we have enhanced the LSO algorithm to scale it to 100 Gbps. A fast DMA is used to support transferring data in the network interface. The LSO processing methodology on the network has presented. In addition, the RISC's performance and data movements for high communication rate up to 100 Gbps have been measured. A 148 MHz RISC core can support the sending-side processing for up to 100 Gbps transmission speed for the TCP/IP and UDP/IP protocol when the MTU is applied (1500 bytes). A DMA with 3759 MHz is required to eliminate the idle cycles while transferring data over the 64-bit local bus.