Evaluation of prediction accuracy for the Longley-Rice model in the FM and TV bands

Accurate geographical coverage predictions maps for FM and TV are needed for channel and frequency allocations and in order to avoid unwanted interferences. The Longley-Rice model has been used for this purpose over the last four decades and still being used almost exclusively by the FCC in the United States. In this work a comparison is presented between the relative accuracy of this model in the VHF-FM and UHF-TV frequency bands. Simulations were made with accurate and up to date input data (antenna height, location, gain, transmit power, etc.) for the FM-TV stations provided by the ERT S.A. public broadcaster in the region of Thessaloniki – Greece. Finally, the calculated – simulated results were confronted to field measurements using a Rohde & Schwarz FSH3 portable spectrum analyzer and high precision calibrated biconical and log-periodic antennas, and the errors between predictions and measurements were statistically analyzed in the two frequency bands. It has been found in this study that the Longley-Rice model, in general, overestimates field-strength values, but this overestimation is much higher in the VHF – FM radio band (88-108 MHz) than in the UHF-TV band (470-790 MHz)

Translation validation for compilation verification

Modern optimizing compilers such as LLVM and GCC are huge and complex, and mature releases routinely have uncaught bugs. Beyond harm to software development, the lack of formal correctness guarantees for the compilation process seriously limits the guarantees other software systems can provide, since the compiler that generates the final executable cannot be trusted. These circumstances have motivated broad interest in compilation verification: providing a formal guarantee that a compilation of a program is correct. Translation Validation is a commonly used compilation verification technique that aims to prove the correctness of a single instance of compilation, by considering only the specific input and output programs and treating the compiler mostly as a black box. Translation Validation techniques are well-suited to the compilation verification problem because they can be composed to validate a sequence of compilation steps, they can easily retrofit to existing compilers, and they can be maintained independently from the compiler itself by a separate team of formal method experts. The basic components of a Translation Validation system are (1) a formal notion of program equivalence, (2) a verification condition generator that generates a relation between program points and variables in the input and output programs, (3) a proof system that accepts the verification conditions, generates a machine-checkable equivalence proof, and checks the proof for correctness. Ideally, such a system is completely agnostic to the specifics of transformation from the input to the output as well as independent of the input/output languages. This allows the same system to be reused across the many transformation and translation passes found in modern compilers. However, this is not true in the state of the art: most existing systems are custom-tailored for a particular sequence of transformations, and moreover, specialized for a specific, common intermediate language for the input and output programs. The overall goal of this work is to show that it is possible to develop a (mostly) language-independent, transformation-agnostic translation validation system with support for different input/output languages for an optimizing, production-quality compiler. In this thesis, we present such a system as well as the theoretical and practical advances needed to arrive to it. First, we present a formal framework for program equivalence checking that is transformation-agnostic and language-independent. This framework can serve as-is as the proof system for any number of Translation Validation systems targeting different transformation and/or translation phases within an existing compiler. The basis of the framework is a rigorous formalization, namely cut-bisimulation, for weak bisimulation variants that serve as a generalization of the various (sometimes ad-hoc) notions of program equivalence found in the literature. We develop a program equivalence checking algorithm that proves two programs equivalent by reducing a proposed relation between corresponding program states to a cut-bisimulation relation. We implement this algorithm in KEQ, a new tool for checking program equivalence that accepts the operational semantics of the input and output languages as parameters, and is independent of the transformation used to generate the output. This is the first program equivalence checking tool known to the authors that is language-parametric instead of containing hard-coded language semantics as is the norm in the literature. Then, we use KEQ as the equivalence checker for two different Translation Validation systems targeting two phases of the LLVM compiler: the Instruction Selection phase and the Register Allocation phase. The two systems share the same notion of equivalence (cut-bisimulation), the same proof system (KEQ), as well as the semantic definitions for the input/output languages (LLVM IR and x86-64 based Machine IR), which are separate artifacts and not hardcoded into the logic of the systems. The only components that are transformation-specific are the two verification condition generators. The Instruction Selection one requires minimal support from the compiler in the form of compiler-generated hints, while the Register Allocation one is employing a novel inference algorithm for register allocation and related optimizations. These systems were evaluated on the GCC SPEC 2006 benchmark, where they correctly validated 4331 / 4732 (91.52%) and 4574 / 4732 (96.67%) functions with supported features respectively

Comparative study of Radio Mobile and ICS Telecom propagation prediction models for DVB-T

In this paper, a comparative study between the results of a measurement campaign conducted in northern Greece and simulations performed with Radio Mobile and ICS Telecom radio planning tools is performed. The DVB-T coverage of a transmitting station located near the city of Thessaloniki is estimated using three empirical propagation models (NTIA-ITS Longley Rice, ITU-R P.1546 and Okumura-Hata-Davidson) and one deterministic model (ITU-R 525/526). The best results in terms of minimum average error and standard deviation are obtained using the deterministic model and the NTIA-ITS Longley Rice empirical model. In order to improve the results, the tuning options available in the ICS Telecom software are used on the Okumura-Hata-Davidson model, leading to a significant increase in accuracy

Modelling and coverage improvement of DVB-T networks

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe necessity of accurate point-to-area and point-to-point prediction tools arises from the enormous demand in designing broadcasting systems for digital TV and cellular communications. Up to now, a considerable number of coverage prediction models for radio coverage has been developed. In electromagnetic wave propagation theory, there are three types of propagation models. Empirical models that are based on a large quantity of measurement data are elementary but not very accurate. Semi-deterministic models that are based on measurement data and electromagnetic theory of propagation, which are more precise. Finally, deterministic models based on theoretical physics, like diffraction theory and Fresnel theory, that require a significant amount of geometrical data about the propagation terrain profile but are the most accurate. The primary outcomes of this research are the comparative study and improvement of several propagation models, using a significant quantity of measurements and simulations and the deduction of useful conclusions to be used by engineers to improve propagation predictions further. In this research, the Longley-Rice (ITM) Irregular Terrain Model model was used, a classic model used for TV coverage prediction, which model is to date the preferred model of the FCC (Federal Communications Commission) in the US for FM-TV coverage calculations. To run the model, the Radio Mobile program (Radio Propagation and Virtual Mapping Freeware) was used based on the Longley-Rice Model ITM, including the 3-arc-second Satellite Radar Terrain Mission (SRTM) maps and the SPLAT! program (an RF Signal Propagation, Loss, And Terrain analysis tool), which also relies on the Longley-Rice ITM model and makes use of SRTM maps. Both programs work in Windows operating system (Windows7 Professional, 64 bits). Another model used in this research was SPLAT! with ITWOM (Irregular Terrain with Obstructions Model) which combines empirical data from the ITU-R P.1546 model and other ITU recommendations in conjunction with Beer's and Snell's laws. The ITU-R Recommendation P.1546 model and the empirical Hata-Davidson model using HAAT were also utilized in this research. The Single Knife-Edge (SKE) model was coded in MATLAB and utilized in this research as a simple reference model, where only one main obstacle is considered. Other well-known multiple knife-edge diffraction models employed in this study are the Epstein-Peterson, Deygout, and Giovaneli models. For these deterministic models, individual MATLAB programs were written. Simulations produced by the models were limited to the main two knife-edges of the propagation path for immediate comparison with the Longley-Rice model which uses the “double knife-edge” approach. All measurement campaigns took place in Northern Greece and Southern (F.Y.R.O.M) Former Yugoslav Republic of Macedonia using a Rohde & Schwarz FSH-3 portable spectrum analyser and precision calibrated antennas

IELE: An Intermediate-Level Blockchain Language Designed and Implemented Using Formal Semantics

Most languages are given an informal semantics until they are implemented, so the formal semantics comes later. Consequently, there are usually inconsistencies among the informal semantics, the implementation, and the formal semantics. IELE is an LLVM-like language for the blockchain that was specified formally and its implementation, a virtual machine, generated from the formal specification. Moreover, its design was based on problems observed formalizing the semantics of the Ethereum Virtual Machine (EVM) and from formally specifying and verifying EVM programs (also called “smart contracts”), so even the design decisions made for IELE are based on formal specifications. A compiler from Solidity, the predominant high-level language for smart contracts, to IELE has also been implemented, so Ethereum contracts can now also be executed on IELE. The virtual machine automatically generated from the semantics of IELE is shown to be competitive in terms of performance with the state of the art and hence can stand as the de facto implementation of the language in a production setting. Indeed, IOHK, a major blockchain company, is currently experimenting with the IELE VM in order to deploy it as its computational layer in a few months. This makes IELE the first practical language that is designed and implemented as a formal specification. It took only 10 man-months to develop IELE, which demonstrates that the programming language semantics field has reached a level of maturity that makes it appealing over the traditional, adhoc approach even for pragmatic reasons.Ope

Protein hydrolysates supplement in the nutrient solution of soilless grown fresh peppermint and spearmint as a tool for improving product quality

7openInternationalInternational coauthor/editorThe present study investigated the potential of fresh peppermint (Mentha × piperita L.) and spearmint (Mentha spicata L.) production on a floating raft system combined with a commercial protein hydrolysate supplement (Amino16®) in a nutrient solution aiming to improve plant product quality. Three levels of the protein hydrolysate solution (0, 0.25 and 0.50%) were added in the nutrient solution, and the plants were harvested after twenty-four days. Plant growth characteristics were recorded, and nutritional, essential oil and polyphenolic composition were determined in fresh tissue. The addition of protein hydrolysates did not affect the fresh or dry weight but reduced plant height. Nitrate content significantly decreased, while total chlorophyll and essential oil content increased in both species. Moreover, the protein hydrolysate solution further increased total antioxidant capacity, total soluble phenol and carotenoid contents in spearmint plants, while it did not affect the essential oil and polyphenolic composition in both species. In conclusion, protein hydrolysates solution may be added in the nutrient solution, to improve the quality of peppermint and spearmint grown in a floating system, without adverse effects on crop yield or the essential oil and polyphenolic profile.openAktsoglou, D.; Kasampalis, D.; Sarrou, E.; Tsouvaltzis, P.; Chatzopoulou, P.; Martens, S.; Siomos, A.Aktsoglou, D.; Kasampalis, D.; Sarrou, E.; Tsouvaltzis, P.; Chatzopoulou, P.; Martens, S.; Siomos, A

Performance comparison of LS, LMMSE and Adaptive Averaging Channel Estimation (AACE) for DVB-T2

© 2015 IEEE. In this paper the performance of the Adaptive Averaging Channel Estimator (AACE-LS) which is a modified Least Square (LS) estimator and the AACE-LMMSE which is a modified Linear Minimum Mean Error (LMMSE) estimator, are compared with respect to the conventional LS and the LMMSE estimators. The AACE is an estimator which is based on the averaging of the last N Scattered Pilots (SP) from the DVB-T2 model carried in the received OFDM symbols. The proposed method could in general be applied to any pilot based estimator. The noise introduced by the channel is considered as Additive White Gaussian Noise (AWGN) with zero mean and thus an averaging process is used to eliminate it. The estimator adaptively follows the fluctuations of the amplitude envelope in the time domain and adapts the size of the buffer N, with respect to the coherence time (Tc). Finally, based on the averaged estimated channel, the LS or the LMMSE equalizer is applied to the received signal in the frequency domain. Simulations clearly show that the performance of the AACE-LS is superior to the conventional LS estimator and is near to the performance of the LMMSE with no need of a prior knowledge of the statistics and the noise of the channel and thus if the channel is unknown to the receiver, the AACE is a good choice

IELE: A Rigorously Designed Language and Tool Ecosystem for the Blockchain

This paper proposes IELE, an LLVM-style language, together with a tool ecosystem for implementing and formally reasoning about smart contracts on the blockchain. IELE was designed by specifying its semantics formally in the K framework. Its implementation, a IELE virtual machine (VM), as well as a formal verification tool for IELE smart contracts, were automatically generated from the formal specification. The automatically generated formal verification tool allows us to formally verify smart contracts without any gap between the verifier and the actual VM. A compiler from Solidity, the predominant high-level language for smart contracts, to IELE has also been (manually) implemented, so Ethereum contracts can now also be executed on IELE.Ope

Securing Smart Contract On The Fly

We present Solythesis, a source to source Solidity compiler which takes a smart contract code and a user specified invariant as the input and produces an instrumented contract that rejects all transactions that violate the invariant. The design of Solythesis is driven by our observation that the consensus protocol and the storage layer are the primary and the secondary performance bottlenecks of Ethereum, respectively. Solythesis operates with our novel delta update and delta check techniques to minimize the overhead caused by the instrumented storage access statements. Our experimental results validate our hypothesis that the overhead of runtime validation, which is often too expensive for other domains, is in fact negligible for smart contracts. The CPU overhead of Solythesis is only 0.12% on average for our 23 benchmark contracts

Designing AfriCultuReS services to support food security in Africa

ABSTRACT: Earth observation (EO) data are increasingly being used to monitor vegetation and detect plant growth anomalies due to water stress, drought, or pests, as well as to monitor water availability, weather conditions, disaster risks, land use/land cover changes and to evaluate soil degradation. Satellite data are provided regularly by worldwide organizations, covering a wide variety of spatial, temporal and spectral characteristics. In addition, weather, climate and crop growth models provide early estimates of the expected weather and climatic patterns and yield, which can be improved by fusion with EO data. The AfriCultuReS project is capitalizing on the above to contribute towards an integrated agricultural monitoring and early warning system for Africa, supporting decision making in the field of food security. The aim of this article is to present the design of EO services within the project, and how they will support food security in Africa. The services designed cover the users' requirements related to climate, drought, land, livestock, crops, water, and weather. For each category of services, results from one case study are presented. The services will be distributed to the stakeholders and are expected to provide a continuous monitoring framework for early and accurate assessment of factors affecting food security in Africa.This paper is part of the AfriCultuReS project "Enhancing Food Security in African Agricultural Systems with the Support of Remote Sensing", which received funding from the European Union's Horizon 2020 Research and Innovation Framework Programme under grant agreement No. 77465