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

Xhonneux, Mathieu; Tapparel, Joachim; Afisiadis, Orion; Balatsoukas‐Stimming, Alexios; Burg, Andreas

doi:10.1109/ieeeconf51394.2020.9443502

Cited by 6 publications

(6 citation statements)

References 11 publications

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“…By applying the same development for K > 2 paths, the general expression is straightforward and given in (10).…”

Section: B Channel Effect On Lora Wave-formsmentioning

confidence: 99%

“…As channel delay spread is small in comparison with symbol duration, we may omit interference coming from previous symbol a − . Equation (10) can be then simplified as:…”

Section: B Channel Effect On Lora Wave-formsmentioning

confidence: 99%

“…One of the first paper to provide a rigorous mathematical representation of LoRa signals and its demodulation scheme was achieved in [4]. Since then, further researches were conducted focusing on specific issues such as network capacity enhancements [5], channel coding improvements [6], [7], temporal/frequency synchronization schemes [8], LoRa demodulation with LoRa interference [9], [10] or LoRa implementation on real world equipment such as Universal Software Radio Equipment (USRP) [11].…”

Section: Introductionmentioning

confidence: 99%

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Simple and Efficient LoRa Receiver Scheme for Multi-Path Channel

Demeslay,

Rostaing,

Gautier

2022

Preprint

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This paper presents a novel LoRa (Long Range) receiver operating in frequency selective Multi-Path Channel (MPC). The dechirped received LoRa wave-forms under MPC allows us to derive a simple and efficient LoRa receiver scheme by using a MF (Matched Filter) approach that aims to maximize the SNR (Signal-to-Noise Ratio) at the symbol index frequency of the DFT output. We show that the MF receiver can be seen as RAKE structure where interference peaks related to multipath, exhibited at DFT output, are recombined in a constructive way. Detection performance is driven by channel energy and the benefit of this novel MF/RAKE receiver over original coherent and non-coherent receiver appears only for MPC that exhibits significant paths energy. These two MF and RAKE receivers have however different implementation complexities that are studied in details. We provide in that sense recommendations on which receiver variant to use for real operations, depending on complexity constraints. Finally, the proposed MF/RAKE receiver outperforms previous results on TDEL (Time Delay Estimation LoRa) receiver over MPC, especially at low SNR and higher LoRa Spreading Factor (SF) parameter, at the cost of higher but reasonable complexity.

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“…By applying the same development for K > 2 paths, the general expression is straightforward and given in (10).…”

Section: B Channel Effect On Lora Wave-formsmentioning

confidence: 99%

“…As channel delay spread is small in comparison with symbol duration, we may omit interference coming from previous symbol a − . Equation (10) can be then simplified as:…”

Section: B Channel Effect On Lora Wave-formsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simple and Efficient LoRa Receiver Scheme for Multi-Path Channel

Demeslay,

Rostaing,

Gautier

2022

Preprint

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“…Contributions: In this work, we provide a detailed description of the two-user LoRa receiver initially introduced in [36]. This two-user receiver features a detector that is derived from the ML sequence estimator (MLSE) and performs individual decisions on the interfering symbols instead of a joint detection over the entire colliding frames.…”

Section: Introductionmentioning

confidence: 99%

“…This two-user receiver features a detector that is derived from the ML sequence estimator (MLSE) and performs individual decisions on the interfering symbols instead of a joint detection over the entire colliding frames. Whereas Xhonneux et al [36] only provided limited experimental results from a proof-ofconcept testbed, we conduct in this article a full derivation and performance analysis of the proposed receiver. We show that the described detector inherently leverages the difference of time, carrier frequency, and received power between users to demodulate the colliding symbols.…”

Section: Introductionmentioning

confidence: 99%

A Maximum-Likelihood-Based Two-User Receiver for LoRa Chirp Spread-Spectrum Modulation

Xhonneux

Tapparel

Balatsoukas‐Stimming

et al. 2022

IEEE Internet Things J.

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Long Range (LoRa) is an emerging low-power widearea network technology offering long-range wireless connectivity to Internet of Things (IoT) devices. For energy efficiency reasons, LoRa end nodes implement a nonslotted ALOHA multiple access scheme to transmit packets to the gateway. Due to the lack of synchronization between end nodes, collisions between uplink packets have been identified as the main obstacle to the scaling of dense LoRa networks. To tackle this issue, we present in this article a LoRa receiver that is capable of decoding colliding packets from two interfering end nodes. The proposed two-user detector is derived from the maximum-likelihood principle using a detailed model of two colliding LoRa packets. As the complexity of the maximum-likelihood sequence estimation is prohibitive, complexity-reduction techniques are introduced to enable practical implementations of the receiver. An in-depth performance analysis highlights that the proposed two-user detector inherently leverages the differences in received power, time offsets, and frequency offsets between the users to separate and demodulate their respective signals. To demonstrate the practicality of the proposed detector, an interference-robust synchronization algorithm is then designed and evaluated. Simulation results indicate that a LoRa receiver combining the proposed synchronization algorithm and two-user detector is capable of detecting and demodulating two interfering users with satisfactorily error rates.

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