Wireless networks have been widely deployed for many Internet-of-Things (IoT) applications, like smart cities and precision agriculture. Low Power Wide Area Networking (LPWAN) is an emerging IoT networking paradigm to meet three key requirements of IoT applications, i.e., low cost, large scale deployment and high energy efficiency. Among all available LPWAN technologies, LoRa networking has attracted much attention from both academia and industry, since it specifies an open standard and allows us to build autonomous LPWAN networks without any third-party infrastructure. Many LoRa networks have been developed recently, e.g., managing solar plants in Carson City, Nevada, USA and power monitoring in Lyon and Grenoble, France. However, there are still many research challenges to develop practical LoRa networks, e.g., link coordination, resource allocation, reliable transmissions and security. This article provides a comprehensive survey on LoRa networks, including the technical challenges of deploying LoRa networks and recent solutions. Based on our detailed analysis of current solutions, some open issues of LoRa networking are discussed. The goal of this survey paper is to inspire more works on improving the performance of LoRa networks and enabling more practical deployments.

A Survey on LoRa Networking: Research Problems, Current Solutions, and Open Issues

Long Range (LoRa) is a Low-power Wide-area Network technology designed for the Internet of Things. In recent years, it has gained significant momentum among industrial and research communities. Patented by Semtech, LoRa makes use of chirp spread spectrum modulation to deliver data with promises of long battery life, far-reaching communication distances, and a high node density at the cost of data rate. In this article, we conduct a series of experiments to verify the claims made by Semtech on LoRa technology. Our results show that LoRa is capable of communicating over 10km under line-of-sight environments. However, under non-line-of-sight environments, LoRa’s performance is severely affected by obstructions such as buildings and vegetations. Moreover, the promise of prolonged battery life requires extreme tuning of parameters. Last, a LoRa gateway supports up to 6,000 nodes with PRR requirement of >70%. This study also explores the relationship between LoRa transmission parameters and proposes an algorithm to determine optimal settings in terms of coverage and power consumption under non-line-of-sight environments. It further investigates the impact of LoRa Wide-area Networks on energy consumption and network capacity along with implementation of a LoRa medium access mechanism and possible gains brought forth by implementing such a mechanism.

Known and Unknown Facts of LoRa: Experiences from a Large-scale Measurement Study

In this article, a symbiotic radio (SR) system is proposed to support passive Internet of Things (IoT), in which a backscatter device (BD), also called IoT device, is parasitic in a primary transmission. The primary transmitter (PT) is designed to assist both the primary and BD transmissions, and the primary receiver (PR) is used to decode the information from the PT as well as the BD. The symbol period for BD transmission is assumed to be either equal to or much greater than that of the primary one, resulting in parasitic SR (PSR) or commensal SR (CSR) setup. We consider a basic SR system which consists of three nodes: 1) a multiantenna PT; 2) a single-antenna BD; and 3) a single-antenna PR. We first derive the achievable rates for the primary and BD transmissions for each setup. Then, we formulate two transmit beamforming optimization problems, i.e., the weighted sum-rate maximization (WSRM) problem and the transmit power minimization (TPM) problem, and solve these nonconvex problems by applying the semidefinite relaxation (SDR) technique. In addition, a novel transmit beamforming structure is proposed to reduce the computational complexity of the solutions. The simulation results show that for CSR setup, the proposed solution enables the opportunistic transmission for the BD via energy-efficient passive backscattering without any loss in spectral efficiency, by properly exploiting the additional signal path from the BD.

Symbiotic Radio: A New Communication Paradigm for Passive Internet of Things

This book explains how UHF tags and readers communicate wirelessly It gives an understanding of what limits the read range of a tag, how to increase it (and why that might result in breaking the law), and the practical things that need to be addressed when designing and implementing RFID technology Avoiding heavy math but giving breadth of coverage with the right amount of detail, it is an ideal introduction to radio communications for engineers who need insight into how tags and readers work
New to this edition:
• Examples of near-metal antenna techniques
• Discussion of the wakeup challenge for battery-assisted tags, with a BAT architecture example
• Latest development of protocols: EPC Gen 120
• Update 18000-6 discussion with battery-assisted tags, sensor tags, Manchester tags and wakeup provisions


The only book to give an understanding of radio communications, the underlying technology for Radio Frequency Identification (RFID)
Praised for its readability and clarity, it balances breadth and depth of coverage
New edition includes latest developments in chip technology, antennas and protocols

The RF in RFID : UHF RFID in Practice Ed. 2

We present Piezo-Acoustic Backscatter (PAB), the first technology that enables backscatter networking in underwater environments. PAB relies on the piezoelectric effect to enable underwater communication and sensing at near-zero power. Its architecture is inspired by radio backscatter which works well in air but cannot work well underwater due to the exponential attenuation of radio signals in water. PAB nodes harvest energy from underwater acoustic signals using piezoelectric interfaces and communicate by modulating the piezoelectric impedance. Our design introduces innovations that enable concurrent multiple access through circuit-based frequency tuning of backscatter modulation and a MAC that exploits the properties of PAB nodes to deliver higher network throughput and decode network collisions. We built a prototype of our design using custom-designed, mechanically fabricated transducers and an end-to-end battery-free hardware implementation. We tested our nodes in large experimental water tanks at the MIT Sea Grant. Our results demonstrate single-link throughputs up to 3 kbps and power-up ranges up to 10 m. Finally, we show how our design can be used to measure acidity, temperature, and pressure. Looking ahead, the system can be used in ocean exploration, marine life sensing, and underwater climate change monitoring.

https://dl.acm.org/doi/pdf/10.1145/3341302.3342091

Underwater backscatter networking

This paper presents PLoRa, an ambient backscatter design that enables long-range wireless connectivity for batteryless IoT devices. PLoRa takes ambient LoRa transmissions as the excitation signals, conveys data by modulating an excitation signal into a new standard LoRa "chirp" signal, and shifts this new signal to a different LoRa channel to be received at a gateway faraway. PLoRa achieves this by a holistic RF front-end hardware and software design, including a low-power packet detection circuit, a blind chirp modulation algorithm and a low-power energy management circuit. To form a complete ambient LoRa backscatter network, we integrate a light-weight backscatter signal decoding algorithm with a MAC-layer protocol that work together to make coexistence of PLoRa tags and active LoRa nodes possible in the network. We prototype PLoRa on a four-layer printed circuit board, and test it in various outdoor and indoor environments. Our experimental results demonstrate that our prototype PCB PLoRa tag can backscatter an ambient LoRa transmission sent from a nearby LoRa node (20 cm away) to a gateway up to 1.1 km away, and deliver 284 bytes data every 24 minutes indoors, or every 17 minutes outdoors. We also simulate a 28-nm low-power FPGA based prototype whose digital baseband processor achieves 220 μW power consumption.

https://dl.acm.org/doi/pdf/10.1145/3230543.3230567

PLoRa: a passive long-range data network from ambient LoRa transmissions

The invention discloses a passive backstage long-distance communication system According to the system, LoRa, WiFi, GSM, Bluetooth and other signals in the environment can be used as excitation signals, the excitation signals are modulated into another standard signal to transmit data, and the new signal is shifted to different channels, so that the obtained backscattered signals are received ina standard network

Qian Yujie

Papers

PLoRa: a passive long-range data network from ambient LoRa transmissions

Passive backstage long-distance communication system, in particular to passive backstage long-distance communication system