Reliable IEEE 802.15.4g based smart utility networks via adaptive modulation selection and re-transmission shaping

In this thesis work, we propose and evaluate a strategy to improve transmission in IEEE 802.15.4g SUN networks. This kind of network is at the basis of many promising IoT applications that require high reliability while maintaining low power consumption. The proposed strategy consists of two distinct parts: re-transmission shaping and modulation selection. The re-transmission shaping mechanism keeps track of unused packet re-transmissions and allocates additional re-transmissions when the instantaneous link quality decreases due to channel impairments. The modulation selection strategies apply Multi-Armed Bandits algorithms to dynamically choose the best transmission modulation. The combined effect of these two mechanisms aims to maximize link reliability while minimizing energy consumption and meeting radio-frequency regulation constraints. To evaluate the proposed methods we use trace-based simulations using an IEEE 802.15.4g SUN data-set and two widely used metrics, the PDR (Packet Delivery Ratio) and the RNP (Required Number of Packets). The obtained results show that re-transmission shaping and modulation selection are useful mechanisms to improve link reliability of low-power wireless communications. Their combined use can increase PDR from 77.9% to 98.7% while sustaining an RNP of 1.7 re-transmissions per packet when compared to using a single re-transmission per packet

Intra-network interference robustness : an empirical evaluation of IEEE 802.15.4-2015 SUN-OFDM

While IEEE 802.15.4 and its Time Slotted Channel Hopping (TSCH) medium access mode were developed as a wireless substitute for reliable process monitoring in industrial environments, most deployments use a single/static physical layer (PHY) configuration. Instead of limiting all links to the throughput and reliability of a single Modulation and Coding Scheme (MCS), you can dynamically re-configure the PHY of link endpoints according to the context. However, such modulation diversity causes links to coincide in time/frequency space, resulting in poor reliability if left unchecked. Nonetheless, to some level, intentional spatial overlap improves resource efficiency while partially preserving the benefits of modulation diversity. Hence, we measured the mutual interference robustness of certain Smart Utility Network (SUN) Orthogonal Frequency Division Multiplexing (OFDM) configurations, as a first step towards combining spatial re-use and modulation diversity. This paper discusses the packet reception performance of those PHY configurations in terms of Signal to Interference Ratio (SIR) and time-overlap percentage between interference and targeted parts of useful transmissions. In summary, we found SUN-OFDM O3 MCS1 and O4 MCS2 performed best. Consequently, one should consider them when developing TSCH scheduling mechanisms in the search for resource efficient ubiquitous connectivity through modulation diversity and spatial re-use

Sub-GHz LPWAN network coexistence, management and virtualization : an overview and open research challenges

The IoT domain is characterized by many applications that require low-bandwidth communications over a long range, at a low cost and at low power. Low power wide area networks (LPWANs) fulfill these requirements by using sub-GHz radio frequencies (typically 433 or 868 MHz) with typical transmission ranges in the order of 1 up to 50 km. As a result, a single base station can cover large areas and can support high numbers of connected devices (> 1000 per base station). Notorious initiatives in this domain are LoRa, Sigfox and the upcoming IEEE 802.11ah (or "HaLow") standard. Although these new technologies have the potential to significantly impact many IoT deployments, the current market is very fragmented and many challenges exists related to deployment, scalability, management and coexistence aspects, making adoption of these technologies difficult for many companies. To remedy this, this paper proposes a conceptual framework to improve the performance of LPWAN networks through in-network optimization, cross-technology coexistence and cooperation and virtualization of management functions. In addition, the paper gives an overview of state of the art solutions and identifies open challenges for each of these aspects

Sincronização de quadro e frequência para OFDM no padrão IEEE 802.15.4g : algoritmos e implementação em hardware

Orientadores: Renato da Rocha Lopes, Eduardo Rodrigues de LimaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O objetivo deste trabalho é propor métodos de sincronização de quadro e de frequência de portadora para a camada física MR-OFDM do padrão IEEE 802.15.4g, começando pela pesquisa de algoritmos, passando pelas etapas de modelagem e simulação em alto nível, e finalmente implementando e avaliando os métodos propostos em hardware. A sincronização de quadro é o processo responsável por detectar o início do dado transmitido, ou seja, a primeira amostra válida do sinal de interesse. No caso de sistemas OFDM, onde o sinal transmitido é composto por um ou mais símbolos OFDM (cada símbolo sendo composto por uma quantidade fixa de amostras), o objetivo é detectar a borda ou janelamento de tais símbolos OFDM, ou seja, onde começa e termina cada um deles. A sincronização de frequência, por sua vez, consiste em estimar e compensar o erro de frequência de portadora, causado principalmente pelo descasamento dos osciladores do transmissor e do receptor. Com base em estudos preliminares, selecionamos o algoritmo de Minn para a detecção de quadro. Para a correção de erro de frequência, dividimos o processo em duas etapas, como é geralmente proposto na literatura: primeiro, o erro de frequência fracionário é estimado no domínio do tempo durante a detecção de quadro e compensado via rotação de sinal; após a conversão do domínio do tempo para o domínio da frequência, o erro de frequência inteiro é estimado e compensado utilizando um novo e simples algoritmo que será proposto e detalhado neste trabalho. Os algoritmos propostos foram implementados em hardware e uma plataforma de verificação baseada em FPGA foi criada para avaliar o seu desempenho. Os módulos implementados são parte de um projeto que está sendo desenvolvido no Instituto de Pesquisa Eldorado (Campinas) que tem como objetivo implementar em ASIC um transceptor compatível com o padrão IEEE 802.15.4gAbstract: The objective of this work is proposing methods of frame and frequency synchronization for the MR-OFDM PHY of IEEE 802.15.4g standard, starting with the research of state-of-the-art algorithms, passing through modeling, high-level simulations, and finally implementing and evaluating the proposed methods in hardware. Frame synchronization is the process responsible for detecting the beginning of transmitted data and, in the case of OFDM systems, the border of each OFDM symbol, while frequency synchronization consists of estimating and compensating the Carrier Frequency Offset (CFO) caused mainly by a mismatch between the transmitter and receiver oscillators. Based on the initial studies, we selected Minn¿s algorithm for frame detection. For the CFO correction, we split the process into two steps, as commonly proposed in the literature: first, the Fractional CFO is estimated in the time domain during the frame detection and compensated via signal rotation; after the conversion from time to frequency domain, the Integer CFO is estimated and compensated with a novel and simple algorithm that will be detailed in this work. The proposed algorithms were implemented in hardware and inserted in an FPGA-based verification platform for performance measurement. The implemented modules are part of a project that is under development at Eldorado Research Institute (Campinas) and aims to implement in ASIC a transceiver compliant to the IEEE 802.15.4g standardMestradoTelecomunicações e TelemáticaMestra em Engenharia Elétric

Comparação experimental do desempenho de tecnologias emergentes de low power wide area networks para IoT

Orientadores: Gustavo Fraidenraich, Eduardo Rodrigues de LimaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Esta dissertação apresenta resultados experimentais para a avaliação de dois circuitos integrados para conectividade IoT, usando uma abordagem sistemática. Um dos circuitos é dedicado a LoRa, enquanto o outro utiliza o padrão IEEE 802.15.4g adotado pela Wi-SUN Alliance. O objetivo desta avaliação é apresentar resultados que possam ajudar todos que pretendem utilizar LoRa, IEEE 802.15.4g/Wi-SUN ou outras opções de conectividade, facilitando a comparação entre essas tecnologias de forma justa e coerente. Os resultados mostram que existem diferenças entre os valores apresentados nos datasheet e os valores medidos durante os experimentos. Existem várias razões que justificam essas divergências, como a configuração dos experimentos, calibração dos equipamentos, o tamanho dos pacotes transmitidos e até as especificações dos testes. Esse resultado reforça a importância de uma abordagem sistemática para a comparação entre tecnologiasAbstract: This dissertation presents experimental results on the evaluation of two commercial integrated circuits for IoT connectivity, using a systematic approach. One of the integrated circuits is devoted to LoRa and the other to IEEE 802.15.4g, which is the physical layer adopted by the WI-SUN Alliance. The goal behind this evaluation is to present results to support those who will make use of LoRa, IEEE802.15.4g/Wi-SUN, or other types of connectivity to fairly compare the technologies. The results show that there are differences between datasheet values and the measures collected during the experiments. There are several reasons for this divergence, such as the experimental setup, equipment calibration, transmitted packet length, and test specifications. This highlights the importance of a systematical approach when comparing technologiesMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric