LR-FHSS extends LoRa uplink coverage to tens of kilometers, but a fundamental asymmetry persists in practice: LR-FHSS nodes are transmit only, and although they contain LoRa receivers, LoRa downlinks fail far short of LR-FHSS ranges. Our outdoor experiments show that LoRa packet reception rate (PRR) collapses beyond 1–2 km while LR-FHSS maintains more than 79% PRR, making ACK, downlink control, and LR-FHSS to LoRa device communication infeasible at long range. Existing CTC techniques cannot address this gap because LoRa requires precise linear chirps, whereas LR-FHSS emits discrete frequency hopped GMSK bursts with mandatory hop gaps and continuous phase memory. We introduce a CTC technique that repurposes the LR-FHSS physical layer into a waveform synthesizer capable of generating LoRa compatible pseudo chirps using either pure tone emission or continuous phase tones derived from GMSK. At the LoRa receiver, a set of physical layer reconstruction mechanisms correct hop discontinuity, offset drift, and GMSK induced phase distortion so that commodity LoRa hardware can decode the resulting chirps. Implemented on USRP B200 with GNU Radio and evaluated across different outdoor scenarios, our technique improves long range reliability by up to 79% over LoRa and increases end to end LR-FHSS PRR by about 15%, enabling a practical long-range downlink and control path without RF front-end changes, assuming PHY-hook access at both the LR-FHSS gateway and the LoRa receiver.

This paper addresses the vulnerability of LoRa communications against attackers transmitting LoRa packet and proposes an effective anti-jamming technique. Mitigating jamming in a LoRa network is extremely challenging as the devices have low computation power and limited energy. The state-of-the-art work addresses this type of jamming by exploiting Received Signal Strength Indicator (RSSI). It is effective only against a single jammer and is ineffective against multiple jammers transmitting LoRa packets with coordinated timing. The variability in arrival times of jamming LoRa packets results in differing RSSI, rendering the technique impractical against multiple jammers. In this paper, we propose a new technique to handle jamming when multiple attackers transmit LoRa packet simultaneously. Our idea is to implicitly synchronize all the LoRa symbols from different packets to ensure the jammers' energy in FFT bins remain distinguishable. This method is link layer-agnostic, entails no overhead at the LoRa nodes, and enables packet decoding even when facing attacks from a single jammer or multiple jammers on a channel, effectively combating reactive jamming. We have implemented our anti-jamming system at the LoRa gateway and conducted experiments under various jamming scenarios on LoRa nodes. The results show that our anti-jamming technique improves packet reception rate and per packet energy consumption by up to 106.56 and 135.15 times under collaborative jamming.

While LoRa networks typically handle very infrequent communications, they can occasionally encounter sudden data bursts in response to unpredictable events such as a forest fire or volcanic eruption. LoRaWAN, the MAC protocol for LoRa, lacks a collision avoidance mechanism due to the severe energy constraints of the nodes. Burst traffic can result in substantial collisions, retransmissions, and packet loss when dealing with burst traffic, leading to rapid depletion of node batteries, increased network latencies, and significantly degraded throughput. In this paper, we propose Burst-MAC, a low-overhead MAC protocol for LoRa networks to efficiently handle burst traffic. When the network traffic is light and infrequent, Burst-MAC operates just like LoRaWAN. Upon detecting a data burst, it switches to burst mode that functions as follows: (i) nodes with bursty data are organized into virtual groups based on channel and spreading factor, and (ii) nodes within each group transmit in a semi-distributed TDMA fashion with each node determining its transmission time slots using a hash function to eliminate the need for centralized schedule distribution. Hash function collisions are resolved through piggybacking with acknowledgements from the gateway, ensuring bounded latencies for transmitted packets. We evaluate Burst-MAC through both physical experiments on LoRa devices and NS-3 simulations under various burst scenarios. Our results demonstrate that Burst-MAC significantly outperforms LoRaWAN and other baselines in several aspects, including a $4.5 \times$ improvement in packet reception rate, up to $6 \times$ reduction in energy consumption, and up to $2.5 \times$ decrease in latency.