Resilient Peer-to-Peer Ranging using Narrowband High-Performance Software-Defined Radios for Mission-Critical Applications

There has been a growing need for resilient positioning for numerous applications of the military and emergency services that routinely conduct operations that require an uninterrupted positioning service. However, the level of resilience required for these applications is difficult to achieve using the popular navigation and positioning systems available at the time of this writing. Most of these systems are dependent on existing infrastructure to function or have certain vulnerabilities that can be too easily exploited by hostile forces. Mobile ad-hoc networks can bypass some of these prevalent issues making them an auspicious topic for positioning and navigation research and development. Such networks consist of portable devices that collaborate to form wireless communication links with one another and collectively carry out vital network functions independent of any fixed centralized infrastructure. The purpose of the research presented in this thesis is to adapt the protocols of an existing narrowband mobile ad-hoc communications system provided by Terrafix to enable range measuring for positioning. This is done by extracting transmission and reception timestamps of signals exchanged between neighbouring radios in the network with the highest precision possible. However, many aspects of the radios forming this network are generally not conducive to precise ranging, so the ranging protocols implemented need to either maneuver around these shortcomings or compensate for loss of precision caused. In particular, the narrow bandwidth of the signals that drastically reduces the resolution of symbol timing. The objective is to determine what level of accuracy and precision is possible using this radio network and whether one can justify investment for further development. Early experiments have provided a simple ranging demonstration in a benign environment, using the existing synchronization protocols, by extracting time data. The experiments have then advanced to the radio’s signal processing to adjust the synchronization protocols for maximize symbol timing precision and correct for clock drift. By implementing innovative synchronization techniques to the radio network, ranging data collected under benign conditions can exhibit a standard deviation of less than 3m. The lowest standard deviation achieved using only the existing methods of synchronization was over two orders of magnitude greater. All this is achieved in spite of the very narrow 10−20kHz bandwidth of the radio signals, which makes producing range estimates with an error less than 10−100m much more challenging compared to wider bandwidth systems. However, this figure is beholden to the relative motion of neighbouring radios in the network and how frequently range estimates need to be made. This thesis demonstrates how such a precision may be obtained and how this figure is likely to hold up when applied in conditions that are not ideal

29th Annual Computational Neuroscience Meeting: CNS*2020

Meeting abstracts This publication was funded by OCNS. The Supplement Editors declare that they have no competing interests. Virtual | 18-22 July 202

LU(S)TI in the global South: an empirical analysis of land use and socio-economic transport interaction in Tanzania using mobile network data

The majority of rural-urban migration is filtered through slums: informally established, unplanned, and unrecognised by the government, scientists have a minimal understand- ing of the 200,000 that exist worldwide, never mind enough insight into the millions of individuals living there. This limited understanding often coincides with a more general absence of data in traditional urban planning approaches, leading to most cities seeing development, positive or otherwise, preceding planning. Wesolowski and Eagle (2010) highlighted the key need to use models of human mobility to help guide effective spatial planning policies. Previous research has shown that thinking about the built environment alone cannot account for individual differences in behaviour, and that we must also consider factors such as socio-economic circumstance and context (which are far more likely to contain explanatory value than the geographies of points of interest, such as home and work locations of individuals alone). However, this remains a very difficult topic to study. Emerging economies are often characterised by institutions struggling to keep even demographic data streams up to date. Combined with ineffective data collection strategies, it is often realistic to expect stakeholders to retain an overview of the dynamics of urban systems. This gap causes many issues, but particularly in East Africa: expense and logistics restrict the ability to deploy sensor technologies; fast-changing environments reduce the utility of traditional household and census surveying; and even when raw data exists there are distinct skill gaps for data analysis. To address this, this thesis extends nascent work, and systematically investigates the use of Call Detail Records (CDR) and Mobile Financial Service (MFS) transaction logs to model mobility, demographics, land use and their interplay. Data used was automatically generated as part of day-to-day operations of a major Tanzanian Mobile Network Operator. As part of this thesis, three empirical analyses are carried out to test the boundaries of inferring activity-based land use, predicting cell tower coverage level socio-economic levels and generating mobility metrics in the form of Origin-Destination matrices and synthetic daily activity plans for the Tanzanian port city of Dar Es Salaam. Further, shortcomings of CDR and MFS data, and ways to overcome these, are identified. Empirical chapters form the basis for the identification of factors from the spatial dimension focused on assessing the impact of the built environment, socio-economic circum- stance and mobility behaviour allowing for the extension of traditional land use-transport interaction (LUTI) models, through the inclusion of socio-economic characteristics. This culminates in a new empirical LU(S)TI analysis for a sub-Saharan context. The metropolitan area of the port city of Dar es Salaam, Tanzania, is a pertinent case study area as it is facing similar challenges to many other fast-growing metropolitan areas in emerging economies globally

LU(S)TI in the global South: an empirical analysis of land use and socio-economic transport interaction in Tanzania using mobile network data

The majority of rural-urban migration is filtered through slums: informally established, unplanned, and unrecognised by the government, scientists have a minimal understand- ing of the 200,000 that exist worldwide, never mind enough insight into the millions of individuals living there. This limited understanding often coincides with a more general absence of data in traditional urban planning approaches, leading to most cities seeing development, positive or otherwise, preceding planning. Wesolowski and Eagle (2010) highlighted the key need to use models of human mobility to help guide effective spatial planning policies. Previous research has shown that thinking about the built environment alone cannot account for individual differences in behaviour, and that we must also consider factors such as socio-economic circumstance and context (which are far more likely to contain explanatory value than the geographies of points of interest, such as home and work locations of individuals alone). However, this remains a very difficult topic to study. Emerging economies are often characterised by institutions struggling to keep even demographic data streams up to date. Combined with ineffective data collection strategies, it is often realistic to expect stakeholders to retain an overview of the dynamics of urban systems. This gap causes many issues, but particularly in East Africa: expense and logistics restrict the ability to deploy sensor technologies; fast-changing environments reduce the utility of traditional household and census surveying; and even when raw data exists there are distinct skill gaps for data analysis. To address this, this thesis extends nascent work, and systematically investigates the use of Call Detail Records (CDR) and Mobile Financial Service (MFS) transaction logs to model mobility, demographics, land use and their interplay. Data used was automatically generated as part of day-to-day operations of a major Tanzanian Mobile Network Operator. As part of this thesis, three empirical analyses are carried out to test the boundaries of inferring activity-based land use, predicting cell tower coverage level socio-economic levels and generating mobility metrics in the form of Origin-Destination matrices and synthetic daily activity plans for the Tanzanian port city of Dar Es Salaam. Further, shortcomings of CDR and MFS data, and ways to overcome these, are identified. Empirical chapters form the basis for the identification of factors from the spatial dimension focused on assessing the impact of the built environment, socio-economic circum- stance and mobility behaviour allowing for the extension of traditional land use-transport interaction (LUTI) models, through the inclusion of socio-economic characteristics. This culminates in a new empirical LU(S)TI analysis for a sub-Saharan context. The metropolitan area of the port city of Dar es Salaam, Tanzania, is a pertinent case study area as it is facing similar challenges to many other fast-growing metropolitan areas in emerging economies globally

The role of phonology in visual word recognition: evidence from Chinese

Posters - Letter/Word Processing V: abstract no. 5024The hypothesis of bidirectional coupling of orthography and phonology predicts that phonology plays a role in visual word recognition, as observed in the effects of feedforward and feedback spelling to sound consistency on lexical decision. However, because orthography and phonology are closely related in alphabetic languages (homophones in alphabetic languages are usually orthographically similar), it is difficult to exclude an influence of orthography on phonological effects in visual word recognition. Chinese languages contain many written homophones that are orthographically dissimilar, allowing a test of the claim that phonological effects can be independent of orthographic similarity. We report a study of visual word recognition in Chinese based on a mega-analysis of lexical decision performance with 500 characters. The results from multiple regression analyses, after controlling for orthographic frequency, stroke number, and radical frequency, showed main effects of feedforward and feedback consistency, as well as interactions between these variables and phonological frequency and number of homophones. Implications of these results for resonance models of visual word recognition are discussed.postprin

Interactive effects of orthography and semantics in Chinese picture naming

Posters - Language Production/Writing: abstract no. 4035Picture-naming performance in English and Dutch is enhanced by presentation of a word that is similar in form to the picture name. However, it is unclear whether facilitation has an orthographic or a phonological locus. We investigated the loci of the facilitation effect in Cantonese Chinese speakers by manipulating—at three SOAs (2100, 0, and 1100 msec)—semantic, orthographic, and phonological similarity. We identified an effect of orthographic facilitation that was independent of and larger than phonological facilitation across all SOAs. Semantic interference was also found at SOAs of 2100 and 0 msec. Critically, an interaction of semantics and orthography was observed at an SOA of 1100 msec. This interaction suggests that independent effects of orthographic facilitation on picture naming are located either at the level of semantic processing or at the lemma level and are not due to the activation of picture name segments at the level of phonological retrieval.postprin

Network-Compute Co-Design for Distributed In-Memory Computing

The booming popularity of online services is rapidly raising the demands for modern datacenters. In order to cope with data deluge, growing user bases, and tight quality of service constraints, service providers deploy massive datacenters with tens to hundreds of thousands of servers, keeping petabytes of latency-critical data memory resident. Such data distribution and the multi-tiered nature of the software used by feature-rich services results in frequent inter-server communication and remote memory access over the network. Hence, networking takes center stage in datacenters. In response to growing internal datacenter network traffic, networking technology is rapidly evolving. Lean user-level protocols, like RDMA, and high-performance fabrics have started making their appearance, dramatically reducing datacenter-wide network latency and offering unprecedented per-server bandwidth. At the same time, the end of Dennard scaling is grinding processor performance improvements to a halt. The net result is a growing mismatch between the per-server network and compute capabilities: it will soon be difficult for a server processor to utilize all of its available network bandwidth. Restoring balance between network and compute capabilities requires tighter co-design of the two. The network interface (NI) is of particular interest, as it lies on the boundary of network and compute. In this thesis, we focus on the design of an NI for a lightweight RDMA-like protocol and its full integration with modern manycore server processors. The NI capabilities scale with both the increasing network bandwidth and the growing number of cores on modern server processors. Leveraging our architecture's integrated NI logic, we introduce new functionality at the network endpoints that yields performance improvements for distributed systems. Such additions include new network operations with stronger semantics tailored to common application requirements and integrated logic for balancing network load across a modern processor's multiple cores. We make the case that exposing richer, end-to-end semantics to the NI is a unique enabler for optimizations that can reduce software complexity and remove significant load from the processor, contributing towards maintaining balance between the two valuable resources of network and compute. Overall, network-compute co-design is an approach that addresses challenges associated with the emerging technological mismatch of compute and networking capabilities, yielding significant performance improvements for distributed memory systems