Riaan Wolhuter

Energy-efficient beaconless geographic routing in energy harvested wireless sensor networks

We propose a routing scheme called energy‐efficient beaconless geographic routing with energy supply (EBGRES) for wireless sensor networks. EBGRES provides loop‐free, fully stateless, energy‐efficient source‐to‐sink routing with minimal communication overhead without the help of prior neighborhood knowledge. It locally determines the duty‐cycle of each node, based on an estimated energy budget for each period, which includes the currently available energy, the predicted energy consumption and the energy expected from the harvesting device. In EBGRES, each node sends out the data packet first rather than a control message. By sending a data packet first, EBGRES performs the neighbor selection only among those neighbors that successfully received the data packet. EBGRES uses a three‐way (DATA/ACK/SELECT) handshake and a timer‐assignment function, the Discrete Dynamic Forwarding Delay (DDFD). We investigate the lower and upper bounds on hop count and the upper bound on energy consumption under EBGRES for source‐to‐sink routing. We further demonstrate the expected total energy consumption along a route toward the sink with the proposed EBGRES approach including a lower bound on energy consumption when the node density increases. Copyright

An Architectural Scheme for Real-Time Multiple Users Beam Tracking Systems

In this paper, the design, building, and functioning of a complete communication system with 16 antenna elements, software-defined radio, and beam-tracking capabilities for up to four users is reported. Since the design uses components off the shelf, it is relatively low cost, which makes it feasible to be used in high-volume commercial applications. A key feature is that all digital beamforming and advanced direction-of-arrival tracking algorithms are integrated into one segment—the multiple users beam tracker. Experimental results with regard to system performance, responding time, and efficiency illustrate the effectiveness of the concept.

Notice of Violation of IEEE Publication Principles Value chain scenarios for M2M ecosystem

Recently attention has been directed to Machine to Machine (M2M) wireless communications by a number of stakeholders which include device manufacturers, applications developers and mobile network operators across the globe. As voice revenues for most mobile operators enter a decline due to the new data oriented networks and services being availed into the market, there is growing need to adopt new revenue models through adoption of wireless connectivity in a wide range of devices. With the introduction of these new applications and services, new stakeholders come into play in the M2M communications value chain. A way to market these M2M devices can thus involve creating a platform of services that adds value and functionality to the devices and is a result of a combination of synergies between device manufacturers, application developers and mobile operators. This paper discusses several value chain scenarios which form the M2M ecosystem wherein all stakeholders assume different levels of control over the customer relationship and the assets that make up the value proposition.

An Adaptive Congestion Control and Fairness Scheduling Strategy for Wireless Mesh Networks

Wireless mesh networks (WMNs) are a promising technology for low cost deployments for telemetry networks in rural areas. The popular contention based carrier sense multiple access with collision avoidance (CSMA/CA) technique is widely used in WMN implementations as it does not require time synchronization compared to time division multiple access (TDMA). The IEEE 802.11e standard was introduced to provide data differentiation services to data on a network with data of different priority. With this standard, the enhanced distributed channel access (EDCA) technique for contention based services experiences an fairness problem where high data can starve lower priority data. CSMA/CA was originally developed for single-hop networks. Collisions tend to increase in multi-hop networks as the contention for the medium increases. To address the fairness and performance degradation with an increase in contention in multi-hop network problems, a novel adaptive congestion control and fairness scheduling (CCFS) strategy is proposed in this paper. The proposed strategy is simulated in OMNeT++ and the INETMANET library to ascertain the performance of the strategy. The strategy was compared with EDCA in terms of end-to-end latency, packet loss percentage and Jains fairness index. The proposed adaptive strategy is shown to reduce packet loss in most test cases as well as provide an overall more fair system with data of different priority when compared to EDCA.

Traffic Class Prediction and Prioritization on a Diversified IP Network Using Machine Learning

As more homes are becoming broadband enabled, a huge strain is placed on the underlying IP infrastructure. In being able to predict the types of traffic that nodes might generate, preference can be given to high priority, latency sensitive traffic. Traditionally, a home had a single computer utilizing a link to the Internet. In recent years this single computer was replaced by a multitude of smart devices with the same ultimate goal: embedding the user into the social fabric of the Internet. With the home still connected via a single link, these nodes are all contending for bandwidth and a novel QoS scheme is needed. In this paper, various models characterizing packet flow on a network will be developed. These are subsequently used to predict as accurately as possible, the immediate future traffic classes to be expected from nodes. This will eventually be used as a dynamic QoS criteria for pre-emptively assigning transmission slots to specific hosts. A number of techniques to accomplish this important task of node traffic pattern prediction, are presented. Lastly, evaluation of our approach, based on an 802.11b/g SOHo implementation, is also covered.

Comparison and optimisation of CSMA/CA back-off distribution functions for a low earth orbit satellite link

This paper presents a comparison of several random number distributions for use in the back-off random variable, in a CSMA/CA protocol. These distributions are optimised for the specific case of a low earth orbit (LEO) satellite communicating with several ground stations, where the propagation time from satellite to different stations is diverse. The results of using these different distributions are presented, with a proposed Boolean- type distribution shown to be optimal. The results are confirmed using OMNeT++ simulations.

A digitally beam-steerable antenna array system for positioning-based tracking applications

In line-of-sight airborne applications, deployment of a steerable antenna array with higher directivity and gain makes sense for reducing ground-station complexity and cost, while still maintaining a reasonable link budget. This paper reports on the design, development, and successful testing of a digitally beam-steerable phased-array antenna integrated as a complete system, comprising the antenna, hosting platform, ground station, and aircraft-based emulator to facilitate convenient aircraft-based testing of the antenna array and ground-air space communication link. Based on the measurements, the 4 × 4 element prototype tested reduced the error rate by a factor of seven in comparison with a 4 × 4 array without steering. For the same link quality, the power required was 12 dB lower than in the case of a single-element antenna. With only minor modifications, the concept can even be used in a Low Earth Orbit (LEO) satellite environment.

An Aircraft Based Emulation Platform for LEO Satellite Antenna Beam Steering

A joint project between the KU Leuven- and Stellenbosch Universities are currently underway to develop a space borne electronically beam steerable antenna and the associated ground-space segments. This paper covers the development of an Aircraft based Satellite Emulator to facilitate convenient aircraft based testing of an antenna array, intended for Low Earth Orbit satellite deployment. A flight strategy is developed to emulate such a satellite pass as best possible, with the strategy implemented in software on in-flight PC hardware. A full interface between the aircraft avionics and satellite bus system has been developed to enable generation of the required antenna steering commands and to create a satellite bus image to the payload. Successful test results are presented, as obtained from the actual aircraft flight simulator. The paper describes the successful development and initial testing of a low altitude flight test strategy for certain satellite borne systems, as a cost-effective and realistic interim step to actual and very expensive space flight testing.

An Overview of Automatic Behaviour Classification for Animal-Borne Sensor Applications in South Africa

Although South Africa has a rich wildlife heritage and a thriving domestic agricultural sector,thousands of animals are brutally poached or stolen every year. We describe a system capable of real-time automatic on-animal behaviour classification using animal-borne sensors. These classification decisions can be transmitted to a monitoring station to trigger appropriate and immediate response. We show how the system can be applied to the real-time monitoring of rhinoceros,thereby demonstrating its potential in nature conservation applications such as the fight against poaching. We also show the systems application to sheep to demonstrate its utility in the monitoring of livestock behaviour for precision farming applications.

A survey of cross-layer protocols for IEEE 802.11 wireless multi-hop mesh networks

Summary There has been an escalation in deployment and research of wireless mesh networks by both the business community and academia in the last few years. Their attractive characteristics include low deployment cost, a low-cost option to extend network coverage and ease of maintenance due to their self-healing properties. Multiple routes exist between the sender and receiver nodes because of the mesh layout that ensures network connectivity even when node or link failures occur. Recent advances among others include routing metrics, optimum routing, security, scheduling, cross-layer designs and physical layer techniques. However, there are still challenges in wireless mesh networks as discussed in this paper that need to be addressed. Cross-layer design allows information from adjacent and non-adjacent layers to be used at a particular layer for performance improvement. This paper presents a survey of cross-layer protocol design approaches applied to the IEEE 802.11 standards for wireless multi-hop mesh networks that have been proposed over the last few years for improved performance. We summarize the current research efforts in cross-layer protocol design using the IEEE 802.11 standard in identifying unsolved issues that are a promising avenue to further research. Copyright