Сигнально-кодовые конструкции для передачи информации с минимальной межканальной интерференцией

В работе рассмотрены математические основы формирования оптимального комплексного ортогонального базиса для конечного набора частотных диапазонов и методы кодирования и декодирования сигнально-кодовой конструкции. Приводятся результаты сравнительных вычислительных экспериментов по оценке доли внеполосного излучения для различных частотных интервалов передачи. Показана возможность кодирования и декодирования сигнально-кодовых конструкции с высоким уровнем устойчивости к воздействию флуктуационных помех при передач

An Open-Source LoRa Physical Layer Prototype on GNU Radio

LoRa is the proprietary physical layer (PHY) of LoRaWAN, which is a popular Internet-of-Things (IoT) protocol enabling low-power devices to communicate over long ranges. A number of reverse engineering attempts have been published in the last few years that helped to reveal many of the LoRa PHY details. In this work, we describe our standard compatible LoRa PHY software-defined radio (SDR) prototype based on GNU Radio. We show how this SDR prototype can be used to develop and evaluate receiver algorithms for LoRa. As an example, we describe the sampling time offset and the carrier frequency offset estimation and compensation blocks. We experimentally evaluate the error rate of LoRa, both for the uncoded and the coded cases, to illustrate that our publicly available open-source implementation is a solid basis for further research.Comment: GNU Radio source code available at: https://tcl.epfl.ch/resources-and-sw/lora-phy

Coded LoRa Frame Error Rate Analysis

In this work, we study the coded frame error rate (FER) of LoRa under additive white Gaussian noise (AWGN) and under carrier frequency offset (CFO). To this end, we use existing approximations for the bit error rate (BER) of the LoRa modulation under AWGN and we present a FER analysis that includes the channel coding, interleaving, and Gray mapping of the LoRa physical layer. We also derive the LoRa BER under carrier frequency offset and we present a corresponding FER analysis. We compare the derived frame error rate expressions to Monte Carlo simulations to verify their accuracy

A Maximum-Likelihood-based Multi-User LoRa Receiver Implemented in GNU Radio

LoRa is a popular low-power wide-area network (LPWAN) technology that uses spread-spectrum to achieve long-range connectivity and resilience to noise and interference. For energy efficiency reasons, LoRa adopts a pure ALOHA access scheme, which leads to reduced network throughput due to packet collisions at the gateways. To alleviate this issue, in this paper we analyze and implement a LoRa receiver that is able to decode LoRa packets from two interfering users. Our main contribution is a two-user detector derived in a maximum-likelihood fashion using a detailed interference model. As the complexity of the maximum-likelihood sequence estimation is prohibitive, a complexity-reduction technique is introduced to enable a practical implementation of the proposed two-user detector. This detector has been implemented along with an interference-robust synchronization algorithm on the GNU Radio Software-Defined-Radio (SDR) platform. The SDR implementation shows the effectiveness of the proposed method and also allows its experimental evaluation. Measurements indicate that our detector inherently leverages the time offset between the two colliding users to separate and demodulate their contributions.Comment: 2020 Asilomar Conference on Signals, Systems, and Computers, Pacific Grove, CA, US

LoRa Backscatter Communications: Temporal, Spectral, and Error Performance Analysis

LoRa backscatter (LB) communication systems can be considered as a potential candidate for ultra low power wide area networks (LPWAN) because of their low cost and low power consumption. In this paper, we comprehensively analyze LB modulation from various aspects, i.e., temporal, spectral, and error performance characteristics. First, we propose a signal model for LB signals that accounts for the limited number of loads in the tag. Then, we investigate the spectral properties of LB signals, obtaining a closed-form expression for the power spectrum. Finally, we derived the symbol error rate (SER) of LB with two decoders, i.e., the maximum likelihood (ML) and fast Fourier transform (FFT) decoders, in both additive white Gaussian noise (AWGN) and double Nakagami-m fading channels. The spectral analysis shows that out-of-band emissions for LB satisfy the European Telecommunications Standards Institute (ETSI) regulation only when considering a relatively large number of loads. For the error performance, unlike conventional LoRa, the FFT decoder is not optimal. Nevertheless, the ML decoder can achieve a performance similar to conventional LoRa with a moderate number of loads.Comment: Early access in IEEE Journal of Internet of Things. Codes are provided in Github: https://github.com/SlinGovie/LoRa-Backscatter-Performance-Analysi

Avaliação do esquema de modulação LoRa implementado em GNURadio e sintetizado em SDR

Os sistemas de comunicação LPWA, (do inglês, Low Power Wide Area), buscam atender a necessidade de transmissão de dados em longas distâncias com baixo consumo energético e com tolerância a altos valores de latência. O esquema de modulação LoRa vem ao encontro à essa necessidade e busca transmitir símbolos através de uma técnica de espalhamento de espectro utilizando modulação M-ária para faixas de frequências não licenciadas. Pelas características intrínsecas dos sistemas de grandes áreas de abrangência, quando não se emprega técnica de prevenção de colisão de pacotes, é comum que hajam colisões. Uma característica da modulação LoRa é a capacidade de autocoexistência por ortogonalidade de portadoras moduladas por diferentes transmissores, sincronizados ou não. Dessa forma, como as colisões podem gerar perda de informação, gasto energético adicional pela retransmissão de dados ou jamming não proposital, buscou-se realizar simulações que avaliam se a ortogonalidade gerada por diferentes fatores de espalhamento garantem que não haja interferência inter símbolos. Para isso, utilizando o GNU Radio com blocos disponibilizados pelo Laboratório de Telecomunicações da EPFL, que mapeiam todas operações em bit que a patente do LoRa usada como base menciona, bem como a modulação e demodulação, buscou-se simular e explorar trabalhos comparativos que pudessem fornecer referência para os resultados encontrados. O ajuste do software GNU Radio, o procedimento de coleta de dados de simulação, e o script para geração de gráficos desenvolvidos, serve como base para avaliações futuras deste protocolo de IoT. Resultados preliminares indicaram discrepância da simulação com o esperado na literatura, revelando a necessidade de aprofundar o entendimento dos blocos utilizados na simulação.Low Power Wide Area communication systems seek to meet the need for data transmission over long distances with low energy consumption and tolerance to high latency values. The LoRa modulation scheme meets this need and seeks to transmit symbols through a spread spectrum technique using M-ary modulation for unlicensed frequency bands. Due to the intrinsic characteristics of large coverage systems, when there is no package collision prevention system, it inevitably leads to collisions. A feature of LoRa modulation is the ability of self-coexistence by orthogonality of carriers modulated by different transmitters, synchronized or not. So, collisions can generate information loss, additional energy expenditure by data retransmission or unintentional jamming, we sought to carry out simulations that assess whether the orthogonality generated by different sampling factors ensure that there is no inter-symbol interference. For this, using GNU Radio with blocks made available by the EPFL Telecommunications Laboratory, which map all bit operations that the patent usade as base mentions, as well as modulation and demodulation, we sought to simulate and explore comparative works that could provide reference to the results found. The adjustmente of the GNURadio software, the simulation data collection procedure and the graph generation script developed are the basis for the future of this IOT protocol. Preliminary results indicated a discrepancy between the simulation and what was expected int the literature, revealing the need to deepen the knowledge of the blocks used in the simulation

Development of LoRaWAN-based IoT system for water quality monitoring in rural areas

This article delineates the design and deployment of an innovative real-time water quality monitoring system tailored for rural regions, focusing on monitoring the water resource quality parameters. We propose a solar-powered, waterproof, portable, and Internet of Things (IoT)-enabled solution that leverages Long Range Wide Area Network (LoRaWAN) technology. Central to this system is a sophisticated LoRa node outfitted with an array of sensors for capturing key water parameters, such as pH, total dissolved solids, turbidity and temperature. A conjunction of an Arduino microcontroller-based board and a LoRa shield facilitates real-time data capture and transmission to a LoRaWAN gateway. The acquired data is transmitted to The Things Network server, which is seamlessly integrated with a ThingSpeak web-based IoT server and ThingView mobile applications. We incorporate a solar cell with a solar shield to ensure sustainable energy provision for powering the entire system through a rechargeable battery. This allows users to access vital water quality information online simultaneously and continuously in real-time. As a testament to its robustness, the system was empirically tested at Gambang Lake to demonstrate its effectiveness, functionality, buoyancy, and waterproof capabilities. We further validated the results by comparing them with laboratory sample analysis findings. Experimental evaluations confirmed the system's reliability, as evidenced by the strong agreement between the water conditions measured using our solution and those obtained from laboratory instruments. Moreover, our system efficiently and remotely updated data across multiple IoT platforms using the LoRa radio interface over the LoRaWAN gateway