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LoRa technology promises to connect billions of battery-powered devices over a long range for years. However, recent studies and industrial deployment find that LoRa suffers severe signal attenuation because of signal blockage in smart cities and long communication ranges in smart agriculture applications. As a result, weak LoRa packets cannot be correctly demodulated or even be detected in practice. To address this problem, this paper presents the design and implementation of MALoRa: a new LoRa reception scheme which aims to improve LoRa reception performance with antenna diversities. At a high level, MALoRa improves signal strength by reliably detecting and coherently combining weak signals received by multiple antennas of a gateway. MALoRa addresses a series of practical challenges, including reliable packet detection, symbol edge extraction, and phase-aligned constructive combining of weak signals. Moreover, MALoRa can also be applied to mobile devices. Experiment results show that MALoRa can effectively expand communication range, increase battery life of LoRa devices, and improve packet detection and demodulation performance especially in ultra-low SNR scenarios.

This paper describes our design and implementation of a covert channel over LoRa physical layer (PHY). LoRa adopts a unique modulation scheme (chirp spread spectrum (CSS)) to enable long range communication at low-power consumption. CSS uses the initial frequencies of LoRa chirps to differentiate LoRa symbols, while simply ignoring other RF parameters (e.g., amplitude and phase). Our study reveals that the LoRa physical layer leaves sufficient room to build a covert channel by embedding covert information with a modulation scheme orthogonal to CSS. To demonstrate the feasibility of building a covert channel, we implement CloakLoRa. CloakLoRa embeds covert information into a regular LoRa packet by modulating the amplitudes of LoRa chirps while keeping the frequency intact. As amplitude modulation is orthogonal to CSS, a regular LoRa node receives the LoRa packet as if no secret information is embedded into the packet. Such an embedding method is transparent to all security mechanisms at upper layers in current LoRaWAN. As such, an attacker can create an amplitude modulated covert channel over LoRa without being detected by current LoRaWAN security mechanism. We conduct comprehensive evaluations with COTS LoRa nodes and receive-only software defined radios and experiment results show that CloakLoRa can send covert information over 250m.

LoRa adopts a unique modulation scheme (chirp spread spectrum (CSS)) to enable long range communication at low power consumption. CSS uses the initial frequencies of LoRa chirps to differentiate LoRa symbols, while simply ignoring other RF parameters (e.g., amplitude and phase). Driven by this observation, we build a covert channel (named CLoRa) by embedding covert information with a modulation scheme orthogonal to CSS. We implement CLoRa with a COTS LoR a node (Tx) and a low-cost receive-only SDR dongle (Rx), The experiment results show that CLoRa can send covert information over 250 m. This demo reveals that the LoRa physical layer leaves sufficient room to build a covert channel by embedding covert information with a modulation scheme orthogonal to CSS.

In this paper, ant colony (ACO) algorithm and steering model of robotic fish are combined for path planning. Firstly, an environmental model with multiple obstacles is established. Then, the ACO algorithm is used to generate feasible path. An optimal path is obtained which satisfies the principle of shortest path and least energy consumption. Sharp turns in the generated optimal path are replaced by small arcs that allow the robotic fish to move normally. Finally, a series of simulation experiments are carried out to verify the excellent performance and effectiveness of proposed algorithm.

In this paper, a novel dynamic model with the data-assisted method of robotic fish is proposed, and a discrete-time sliding mode controller for robotic fish is implemented to effectively control the steering. Considering the interference including frequency nonlinearity and angular speed delay term etc., the dynamic model is established based on experimental data which is added into the nonlinear interference. Aiming at solving the problem of the uncertainty of robotic fish system, a discrete-time sliding mode controller for steering control is designed, in the sense that not only the nonlinear interference can be weakened and the strong robustness can be obtained but also the steering angle of robotic fish can converge to the reference angle asymptotically. The simulation results show the effectiveness of the proposed dynamic model and the discrete-time sliding mode controller for steering tracking.