ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / The theoretical capacity of communication channel in the presence of additive white Gaussian noise (AWGN) as defined by Shannon's channel capacity theorem has been well understood since 1940s. This theorem bounds the bit error rate (BER) of RF data links achievable for a particular noise level. The development in digital technology over the last decade has made it possible not just to design devices that operate close to the Shannon's limit, but also to explore techniques, such as best source and best data selectors, for further improvements in performance of RF data links where frequency, spatial or polar diverse reception is possible. This paper discusses an approach to improving quality of data links using an advanced diversity technique that does not select one source at a time but aligns and combines soft values from each. It shows how the overall bit error rate of RF data link can be improved by combining signals from multiple receivers and/or transmitters. Test results showing practical performance improvements are presented and discussed.

Random access schemes are primarily used for data transmission in the uplink of cellular networks. Every user in a random access network is programmed to follow a predetermined transmit control policy that is designed to achieve optimal network performance. This approach, however, is not very efficient in cellular networks where channel conditions vary from time to time. Employing a fixed transmission policy may not guarantee optimal performance. To alleviate this problem, recently, channel aware random access schemes have been proposed wherein information available at the physical (PHY) layer is utilized at the higher layers to maximize network throughput. Such a cross-layer approach naturally has its share of challenges and problems. The objective of the proposed research is to study the effect of multicarrier diversity on channel aware random access schemes. First, we describe two generic random access schemes - channel aware multicarrier random access (CAMCRA) and no selection random access (NS-RA) for multicarrier networks. The former is based on judicious carrier selection and exploits multicarrier diversity while the latter does not perform carrier selection. For illustration purposes, we consider the well-known Aloha protocol and study the effect of channel state imperfection on the overall network throughput. We show that networks employing the NS-RA scheme are extremely sensitive to channel measurement errors. More precisely, the asymptotic average throughput of the NS-RA scheme under uncertain channel conditions is zero. The CAMCRA scheme, however, is very robust to channel estimation errors and maintains the same order of throughput.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / A remotely-operated ground telemetry tracking and receiving station is described. The station, operating in a space-diversity mode, is capable of reception and tracking both at VHF and at UHF. The station can be configured and operated from a distance of 240 km using a wide-band land data link. Uplink command at VHF is included as part of the station.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The relative anti-jam (AJ) performance of several diversity combiners are investigated. The modulation is 8-ary frequency-shift-keying (FSK), the demodulation process consists of energy detection of the eight frequency bins at each hop and the subsequent combining of detector outputs. Three combiners are considered : the linear combiner, where the detector outputs of each hop (corresponding to the same frequency bin) are summed without any processing; the self-normalized combiner, where the eight detector outputs of any particular hop are normalized so that they add to unity; and the max-normalized combiner, where the eight detector outputs of any hop are divided by the maximum value among those eight outputs. Results indicate that under worst-case tone jamming, the selfnormalized combiner performs the best, the max-normalized combiner second best, and the linear combiner performs the worst among the three.

Reader response to original column article by Eric Jennings in Vol 23 Issue 1, re librarian stereotypes and image. / This is an Accepted Manuscript of an article published by Taylor & Francis in College & Undergraduate Libraries on July 6, 2016, available online: http://www.tandfonline.com/10.1080/10691316.2016.1188609

Management improvements have caused a decline in plant species diversity in traditionally managed haymeadows. The aim of this study was examine the effects and causes of management improvements on the soil microbialocmmunity with particular emphasis on the fungal component. A seasonal study of 3 sites showed that management improvements to haymeadows consistently reduced soil microbial biomass C, but had no effect on dehydrogenase activity and basal respiration. Management improvements to these sites also caused a significant reduction in VAM spore numbers, soil fungal biomass, measured as soil ergosterol content and the PLFA 18:w6, and a decrease in the fungal:bacteria PLFA ratio. VAM spore numbers were not correlated with the possibly mycorrhizal NLFA 16:w5. In the Welsh haymeadow, fungi of the genera Fusarium, Mucor, Absidia, Cladosporium, Trichodenna, Acremonium, Zygorhynchus and Paecilomyces were commonly isolated on litter and soil. Commonly isolated fungi had proteolytic and urease activity, and approximately half had cellulose and lignin decay abilities. Management improvements induced shifts in the isolation frequency of these fungi, resulting in an increase in more general resource fungi, capable of growth on both litter and soil. Management improvements to haymeadows, may also have reduced species diversity of litter fungi. Agar and microcosm experiments established that changes in fungal community structure observed in the field could be in response to changes in plant litter inputs and applications of NPK fertiliser. Pairings of fungi on PDA showed that there was a combative hierarchy amongst the fungi, but was not able to show if this hierarchy was affected by NPK. A field experiment found no response of the soil microbial community to short term applications (2 years) of fertiliser or fungicide. The findings of this study suggest that management improvements to grasslands will induce changes in microbial and fungal community structure, this will be discussed.

International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Methods to improve reception during multipath fading of telemetry data received aboard ships participating in missile exercises include various diversity techniques. Among these techniques are polarization, angle, height, and frequency diversity. In this paper, a two-ray multipath model is used to investigate the various techniques and determine the merits of each. Possible ways of implementing the promising ones are discussed.

International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, Nevada / A major factor in the performance of a Telemetry System over the sea is the effect of multipath. The reflected signal from the surface of the sea may, in general, add to or subtract from the direct signal, and may therefore lead to severe fading and possible loss of useful signal. The multipath is a function of the sea state and the polarization of the signal. In order to reduce the effect of multipath on performance, a dual polarization diversity system is being built for the Airborne Telemetry Relay System for the Gulf Range. An analysis of the performance of the dual polarization diversity system in the presence of multipath for different sea states, different reflection angles, and different initial polarization angles is presented. For comparison, a similar analysis is presented for a circular polarization receiving antenna system.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Telemetry receiving sites at missile test ranges almost always use polarization diversity to maximize the quality of the telemetry signals collected from missiles during developmental tests. If the sites are operating optimally, their sensitivity should be independent of received polarization. In this paper a technique to test the sensitivity of each receiving site is presented that involves radiating from a central location with selectable polarization and precise power level. Results of testing five telemetry sites are presented and compared with performance predicted through link analysis using site G/T and location information.

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