@article{articled,

title = {Time-slotted LoRa MAC with variable payload support},

author = {Anna Triantafyllou and Dimitrios Zorbas and Panagiotis Sarigiannidis},

url = {https://www.researchgate.net/publication/361718810_Time-slotted_LoRa_MAC_with_variable_payload_support},

doi = {10.1016/j.comcom.2022.06.043},

year  = {2022},

date = {2022-09-01},

journal = {Computer Communications},

volume = {193},

abstract = {LoRaWAN is an upcoming Low Power Wide Area Network (LPWAN) technology for Internet of Things implementations in various application domains. Despite its various advantages, LoRaWAN employs an Aloha-based MAC, which in terms of performance can not guarantee high packet delivery ratio and low latency. To overcome this issue, we propose a time-slotted scheme, called TS-VP-LoRa, which supports multiple transmission times and packet sizes at the same time. In TS-VP-LoRa, scheduling is coordinated by the LoRa gateway, broadcasting beacon frames periodically for the synchronization of LoRa end-devices. A channel hopping mechanism is also proposed in order to minimize the occurrence of collisions and to evenly split the transmission load among all channels. TS-VP-LoRa is evaluated and compared to three other MAC-layer schemes in single gateway simulation scenarios with up to 500 nodes. The proposed scheme has proven to achieve low latency with high packet delivery ratios, significantly minimize collisions and maintain a relatively low energy consumption despite the scaling of the LoRa network.},

keywords = {LoRaWAN, time-slotted scheme, TS-VP-LoRa},

pubstate = {published},

tppubtype = {article}

}

@article{Moysiadis2021b,

title = {Extending ADR mechanism for LoRa enabled mobile end-devices},

author = {V. Moysiadis and T. Lagkas and V. Argyriou and A. Sarigiannidis and I. Moscholios and P. Sarigiannidis},

url = {https://www.researchgate.net/publication/353860976_Extending_ADR_mechanism_for_LoRa_enabled_mobile_end-devices},

doi = {10.1016/j.simpat.2021.102388},

year  = {2021},

date = {2021-08-08},

journal = {Simulation Modelling Practice and Theory},

volume = {102388},

abstract = {A considerable percentage of Internet of Things end-devices are characterised by mobility, a feature that adds extra complexity to protocols used in Wireless Sensor Networks. LoRa is one of the newly introduced wireless sensor protocols, capable of delivering messages in long distances and consuming low energy, features that make it proper for low cost devices. Although LoRa was introduced as a technology for stationary devices, it can also be used for mobile devices of low speed. In this paper, we introduce an enhancement to Adaptive Data Rate (ADR) mechanism to enable mobile LoRa, by improving the connection reliability of mobile end-devices, while keeping energy consumption at low levels. Firstly, we propose the Linear Regression - ADR (LR-ADR) mechanism for the Network Server side to smooth the Signal to Noise Ratio (SNR) estimates per gateway and predict the SNR of the next transmission. Secondly, we propose the Linear Regression + ADR (LR+ADR) mechanism, an adaptive method for the end-device side to regain the connectivity faster with the Network Server. We conducted simulation modelling to evaluate the performance of our implementation while we compared our results with four alternative solutions ADR, ADR+, EMA-ADR, G-ADR. The results prove that our first approach (LR-ADR) performs better than the best competitor, and our second approach (LR+ADR) brings an additional improvement in terms of Packet Delivery Ratio (PDR), while they retain the Energy Consumption per Packet Delivered (ECPD) at low levels. In particular, in a scenario that mimics real world conditions, LR+ADR presents an increase of up to 520% for PDR compared to the original ADR and an improvement of up to 38% compared to the best competitor (G-ADR). Moreover, it reduces ECPD up to 74% compared to the original ADR, while keeping it at the same level with the best competitor (G-ADR).},

keywords = {adaptive data rate, energy consumption, LoRa, LoRaWAN, mobile devices},

pubstate = {published},

tppubtype = {article}

}

@article{Triantafyllou2021,

title = {Leveraging fairness in LoRaWAN: A novel scheduling scheme for collision avoidance},

author = { A. Triantafyllou, P. Sarigiannidis, T. Lagkas, I. D. Moscholios and A. Sarigiannidis},

url = {https://www.researchgate.net/publication/346627962_Leveraging_Fairness_in_LoRaWAN_A_Novel_Scheduling_Scheme_for_Collision_Avoidance},

doi = {10.1016/j.comnet.2020.107735},

year  = {2021},

date = {2021-02-01},

journal = {Computer Networks},

volume = {186},

pages = {107735},

publisher = {Elsevier BV},

abstract = {The employment of Low-Power Wide Area Networks (LPWANs) has proven quite beneficial to the advancement of the Internet of Things (IoT) paradigm. The utilization of low power but long range communication links of the LoRaWAN technology promises low energy consumption, while ensuring sufficient throughput. However, due to LoRa's original scheduling process there is a high chance of packet collisions, compromising the technology's reliability. In this paper, we propose a new Medium Access Control (MAC) protocol, entitled the FCA-LoRa leveraging fairness and improving collision avoidance in LoRa wide-area networks. The novel scheduling process that is introduced is based on the broadcasting of beacon frames by the network's gateway in order to synchronize communication with end devices. Our results demonstrate the benefits of FCA-LoRa over an enhanced version of the legacy LoRaWAN employing the ALOHA protocol and an advanced adaptive rate mechanism, in terms of throughput and collision avoidance. Indicatively, in a single gateway scenario with 600 nodes, FCA-LoRa can increase throughput by nearly 50%while in a multiple gateway scenario, throughput reaches an increase of 49% for 500 nodes. © 2020 Elsevier B.V.},

keywords = {Collision avoidance, Fairness, Internet of things, LoRa, LoRaWAN, Low-Power Wide Area Networks, Medium Access Control, Scalability},

pubstate = {published},

tppubtype = {article}

}