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ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / This experiment has two purposes. One, to determine if a modern diversity combiner normally used in missile telemetry for polarization diversity can be used for spatial diversity to obtain a gain in the signal quality. Two, to determine if a simple test can be designed such that a non-laboratory test can be performed by the average telemetry operator in order to assess the first purpose.

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In this dissertation, the problem of synchronization for OFDM-based wireless communication systems is studied. In the first part of this dissertation, the sensitivity of both single input single output (SISO) OFDM and multiple input multiple output (MIMO) OFDM receivers to carrier and timing synchronization errors are analyzed. Analytical expressions and numerical results for the power of inter-carrier interference (ICI) are presented. It is shown that the OFDM-based receivers are quite sensitive to residual synchronization errors. In wide-sense stationary uncorrelated scattering (WSSUS) frequency-selective fading channels, the sampling clock timing offset results in rotation of the subcarrier constellation, while carrier frequency offsets and phase jitter cause inter-carrier interference. The overall system performance in terms of symbol error rate is limited by the inter-carrier interference. For a reliable information reception, compensatory measures must be taken. The second part of this dissertation deals with the impact of spatial diversity (usage of multiple transmit/receive antennas) on synchronization. It is found that with multiple transmit and receive antennas, MIMO-OFDM systems can take advantage of the spatial diversity to combat carrier and timing synchronization imperfections. Diversity can favorably improve the synchronization performance. Data-aided and non-data-aided maximum likelihood symbol timing estimators for MIMO-OFDM systems are introduced. Computer simulations show that, by exploiting the spatial diversity, synchronization performance of MIMO-OFDM systems in terms of mean squared error (MSE) of residual timing offset becomes significantly more reliable when compared to conventional SISO OFDM systems. Therefore, spatial diversity is a useful technique to be exploited in the deployment of MIMO-OFDM communication systems. In MIMO systems with synchronization sequences, timing synchronization is treated as a multiple hypotheses testing problem. Generalized likelihood ratio test (GLRT) statistics are developed for MIMO systems in frequency flat channels and MIMO-OFDM systems in frequency selective fading environments. The asymptotic performance of the GLRT without nuisance parameters is carried out. It is shown that the asymptotic performance of the GLRT can serve as an upper bound for the detection probability in the presence of a limited number of observations as well as a benchmark for comparing the performances of different timing synchronizers.

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Frequency selective multipath is a key performance limiter for aeronautical telemetry applications. Our research explores multipath mitigation techniques with ARTM Tier-1 waveforms using linear adaptive filters, multiple receive antennas and error-based best source selection. Single antenna adaptive equalization alone is unable to substantially improve performance under certain channel conditions. Analytical investigations demonstrate that nonlinear channel phase response is the principal cause of performance loss. In this adverse environment, spatial diversity with multiple receive antennas along with error-based best source selection are capable of improving bit error rate performance by 5dB for each additional antenna.

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / A method for combining telemetry data and quantifying the resulting coding gain for a ballistic missile test flight is presented. Data received from five ground stations in 54 data files with 18 million intermittent frames is combined, to create a single file with 1.5 million continuous frames. Coding gain provided by data combining is as high as 30 dB, with a useful improvement of 5 dB at boost and terminal stages. With frame reconstruction techniques, erroneous words in a frame are reduced from 2.1% to 0.12 %.

Advances in Multimedia communications have shown the need for high data rate wireless links over short distances. This is to enhance flexibility, accessibility, portability and mobility of devices in home and enterprise environment thereby making users more productive. In 2004, the WiMedia group proposed the Multiband Orthogonal Frequency Division Multiplex Ultra Wideband (MB-OFDM UWB) system with a target of delivering data rate of 480Mbps over 3 metres. However, by now no existing commercial UWB product can meet this proposed specification. The project aims to investigate the reason why UWB technology has failed to realise its potential by carrying out detailed analysis and to seek ways of solving the technical problems. Detailed system analyses were carried out on the UWB technology using a commercial UWB product and a MB-OFDM UWB Evaluation kit. UWB channel measurements of different scenarios were carried out in order to characterise both time varying and time invariant channels. The scenarios are the realistic environments where UWB devices are operating with human subjects in various movement patterns. It gives insight into the effects of human object blocking on the MB-OFDM system performance and estimates an acceptable feedback rate in a UWB time varying channel when implementing an adaptive modulation. The adaptive modulation was proposed and implemented in the MB-OFDM system model to demonstrate the improved Bit Error Rate (BER) performance. Modulating bits are varied across the sub-channels depending on the signal to noise ratio (SNR). Sub-channels experiencing severe fading employ lower or no bit-loading while sub-channels with little or no fading utilise higher bit-loading to maintain a constant system data rate. Spatial diversity was employed to exploit different properties of the radio channel to improve performance. Good diversity gain of two receiving diversity systems using maximal ratio combining and antenna selection techniques is demonstrated in the measurements with the different antenna orientations. An antenna selection circuit is designed and implemented working together with AT90CAP9 UWB Evaluation kit, verifying an improved performance of the UWB system in an indoor environment. The maximal ratio combining technique is also implemented and demonstrated to give a better system performance on a test bed after post-processing.

Ants are highly abundant and ubiquitous in many terrestrial ecosystems. They perform many important ecological functions and have been widely employed as bioindicators for various terrestrial monitoring programmes. In agroecosystems, their role is controversial because ants can act as predators against herbivorous pest but also associate with and protect honeydew-producing hemipteran pests. The ecology, function and interactions of ants with other arthropods in vineyards are poorly known and this thesis therefore examines their distribution and ecology in south-eastern Australian vineyards. / An extensive survey of 50 vineyards distributed in five regions in South Australia and Victoria recorded 147 native ant species and one invasive species, Linepithema humile (Mayr). Species richness, compositional similarities and assemblage structure varied within and across regions. High species turnover and variation in assemblage structure were found across regions and implications of these patterns are discussed. The invasive L. humile was only detected in some vineyards in one region. The potential impact of management practices and off-farm vegetation on augmenting ant diversity and conserving biodiversity are considered. / The impact of non-target agrochemical applications on ants was investigated in 19 vineyards that received varying levels of agrochemical input. Ant assemblage structure and assemblages were not found to be impacted by pesticides. In contrast, ant assemblage structure was influenced by the presence of shelterbelts near the sampling area. Reasons for the resilience of ants to pesticides are given and assessment at the colony level instead of worker abundance is suggested. / An ant-exclusion experiment was designed to test the impact of native ants on both canopy and ground arthropods concurrently. The potential influence of ants on predation and parasitism on eggs of light brown apple moth (LBAM), a grape pest, was also examined. Adult grapevine scale insects and earwigs under bark were also counted after a season of ant-exclusion. While ant exclusion was successful, there was no detectable difference in the abundance of most arthropod orders and feeding groups between ant-excluded and control vines, although ground spiders were more abundant under ant-excluded vines, despite increased ground ant foraging pressure. LBAM egg parasitism and predation were low and probably affected by weather and other arthropods. Ant exclusion did not reduce survival of scale insects, although the distribution and abundance of scale insects were negatively associated with earwigs. Reasons for the lack of negative effects of ants are discussed. / The spatial patterns of ants were investigated with intensive pitfall trappings in two vineyards to examine if non-random patterns occur and whether these might be the result of competitive species interactions as well as non-crop vegetation adjacent to the vineyards. Null model analyses suggested competitive species interactions within ant assemblages that might have been driven by dominant species even though both positive and negative associations between dominants were also found. Consistent spatial aggregations indicated significant spatial overlap in distributions of some species. Such overlap suggests that potential co-existence might be attributed to temporal partitioning or differences in foraging strategies. The presence of vegetation had a marked influence on ant assemblage structure and competitive interactions, and might also facilitate co-existence by increasing resource heterogeneity. The implications of these findings for sampling strategies and ecological processes within vineyards are discussed. / This thesis has provided new information about ants in vineyards. The high ant diversity could be important in maintaining ecosystem services. Among the 33 ant genera recorded, Iridomyrmex, Paratrechina and Rhytidoponera have the greatest potential in contributing to canopy pest suppression although their associations with honeydew-producing hemipterans need to be considered. Stable isotope analysis or/and molecular gut content analysis should reveal their trophic position in vineyards. Evaluation of crop yield that is directly attributed to soil conditioning by ants in agroecosystems should be explored. The importance of landscape composition, complexity and connectivity is highlighted and role of agroecosystems in conserving biodiversity is emphasised. Future research should be directed towards understanding how landscape composition and complexity may enhance ant diversity and alter dynamics and interactions that may be functionally important (biological control, soil conditioning, etc) in a landscape context.

In this thesis, we argue for node selection in cooperative decode-and-forward networks. In a single-hop network with multiple relays, we show that selecting a single node to aid in the transmission between a source and a destination outperforms both traditional orthogonal transmissions and distributed space-time codes. In networks where sources transmit information over multiple hops and relays can communicate with each other, we study the relationship between cooperation and channel-adaptive routing. We show that cooperation is only beneficial if designed jointly with a routing scheme. This motivates a search for optimal algorithms in generalized relay networks. In networks without restrictions on the relays in terms of whom they can communicate with, we study the problem of optimal resource allocation in terms of transmission time. The resource allocation selects the relays to participate in the transmission and optimally allocates time resource between the selected relays. To implement this resource allocation algorithm, we propose a recursive solution which reduces the computational complexity of the algorithm. For large networks, the resulting computational complexity of implementing the algorithm is exponential in the size of the network and is likely to preclude its implementation. We thus propose that the resource allocation be implemented sub-optimally through node selection: a subset of the nodes in the network should be selected and used as input to the optimal resource allocation algorithm. We provide guidelines for selecting the nodes and propose four heuristics which offer various complexity-performance trade-offs. Compared to the optimal resource algorithm, all four heuristics significantly decrease the required computation complexity of the optimal algorithm.

In this thesis, we argue for node selection in cooperative decode-and-forward networks. In a single-hop network with multiple relays, we show that selecting a single node to aid in the transmission between a source and a destination outperforms both traditional orthogonal transmissions and distributed space-time codes. In networks where sources transmit information over multiple hops and relays can communicate with each other, we study the relationship between cooperation and channel-adaptive routing. We show that cooperation is only beneficial if designed jointly with a routing scheme. This motivates a search for optimal algorithms in generalized relay networks. In networks without restrictions on the relays in terms of whom they can communicate with, we study the problem of optimal resource allocation in terms of transmission time. The resource allocation selects the relays to participate in the transmission and optimally allocates time resource between the selected relays. To implement this resource allocation algorithm, we propose a recursive solution which reduces the computational complexity of the algorithm. For large networks, the resulting computational complexity of implementing the algorithm is exponential in the size of the network and is likely to preclude its implementation. We thus propose that the resource allocation be implemented sub-optimally through node selection: a subset of the nodes in the network should be selected and used as input to the optimal resource allocation algorithm. We provide guidelines for selecting the nodes and propose four heuristics which offer various complexity-performance trade-offs. Compared to the optimal resource algorithm, all four heuristics significantly decrease the required computation complexity of the optimal algorithm.