Offline Scheduling Algorithms for Time-Slotted LoRa-based Bulk Data Transmission

Zorbas, Dimitrios; Abdelfadeel, Khaled Q.; Cionca, Victor; Pesch, Dirk; O’Flynn, Brendan

doi:10.1109/wf-iot.2019.8767277

Cited by 30 publications

(26 citation statements)

References 8 publications

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“…The possibility to use offline scheduling has also been investigated in [9] to reach realtime constraints with duty-cyle requirements, and in [10] by splitting the beacon window onto sub-periods with and without contention. In [11] and [12], Zorbas et al explore the solutions in which data is stored within the nodes and then collected in bulk. Clock-based synchronization has also been studied in [13] and [14], which additionally features a full scheduling mechanism built on top of Class A.…”

Section: Overview and Related Workmentioning

confidence: 99%

Short: Achieving Energy Efficiency in Dense LoRaWANs through TDMA

Chasserat

Accettura

Berthou

2020

2020 IEEE 21st International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM)

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Long Range Wide Area Networks (LoRaWANs) have recently emerged as a hot research topic for their capability to collect sporadic data from a great number of widely spread low power devices. By enabling low-cost low-traffic wireless communications at large scale, such networks can be adopted in many application domains, including smart agriculture, logistics, and emergency detection among others. LoRaWAN employs a pure ALOHA default medium access scheme, that limits the maximum achievable throughput to 18%. Increasing the number of terminals would lead to more frame collisions, and eventually to network collapse. The easiest way to allow bigger network sizes is to synchronize devices, so that they can discretize time into slots, and use them to schedule frame transmissions. Herein, a Time Division Multiple Access (TDMA) scheme on the top of LoRaWANs is highly desired. However, since keeping synchronization can lead to heavy energy consumption, the design of such scheme should enforce energy-efficiency. This contribution describes the technical issues related to the implementation of such mechanism, that as a matter of fact represents the cornerstone on which more sophisticated random access protocols or even scheduling techniques can be designed. In dense networks, the proposed scheme combined with a very simple slotted ALOHA mechanism has also been shown to outperform the default LoRaWAN access protocol in terms of expected energy consumption.

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Section: Overview and Related Workmentioning

confidence: 99%

Short: Achieving Energy Efficiency in Dense LoRaWANs through TDMA

Chasserat

Accettura

Berthou

2020

2020 IEEE 21st International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM)

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“…In our previous work [ 11 ], we investigated the gains of using two centralised scheduling algorithms when the number of nodes and their transmission settings (e.g., reliable SFs) are known. The proposed algorithms assign SFs and allocate time slots for transmissions, aiming at generating collision-free schedules with the minimum possible data collection time.…”

Section: Introductionmentioning

confidence: 99%

Optimal Data Collection Time in LoRa Networks—A Time-Slotted Approach

Zorbas

Caillouet

Abdelfadeel

et al. 2021

Sensors

Self Cite

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LoRa is a low-power and long range radio communication technology designed for low-power Internet of Things devices. These devices are often deployed in remote areas where the end-to-end connectivity provided through one or more gateways may be limited. In this paper, we examine the case where the gateway is not available at all times. As a consequence, the sensing data need to be buffered locally and transmitted as soon as a gateway becomes available. However, due to the Aloha-style transmission policy of current LoRa-based standards, such as the LoRaWAN, delivering a large number of packets in a short period of time by a large number of nodes becomes impossible. To avoid bursts of collisions and expedite data collection, we propose a time-slotted transmission scheduling mechanism. We formulate the data scheduling optimisation problem, taking into account LoRa characteristics, and compare its performance to low complexity heuristics. Moreover, we conduct a set of simulations to show the benefits of synchronous communications on the data collection time and the network performance. The results show that the data collection can reliably be achieved at least 10 times faster compared to an Aloha-based approach for networks with 100 or more nodes. We also develop a proof-of-concept to assess the overhead cost of communicating the schedule to the nodes and we present experimental results.

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“…Taking into account this independence, FREE allocates the best possible spreading factor for each device, according to the chosen objective function. In [25], we investigated an offline version of the spreading factor allocation in which the global state information of the network is assumed to be known in advance of the data collections. The offline algorithm works by scheduling transmissions in a decreasing order of the spreading factors.…”

Section: B Spreading Factor and Slot Numbermentioning

confidence: 99%

“…The only other work that addresses bulk data transmission in LoRaWAN is our earlier work in [25]. In [25], we considered a static network configuration by assuming that the global state information of the network is known before each data collection.…”

Section: Related Workmentioning

confidence: 99%

$FREE$ —Fine-Grained Scheduling for Reliable and Energy-Efficient Data Collection in LoRaWAN

Abdelfadeel

Zorbas

Cionca

et al. 2020

IEEE Internet Things J.

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LoRaWAN promises to provide wide-area network access to low-cost devices that can operate for up to 10 years on a single 1000mAh battery. This makes LoRaWAN particularly suited to data collection applications (e.g. monitoring applications), where device lifetime is a key performance metric. However, when supporting a large number of devices, LoRaWAN suffers from a scalability issue due to the high collision probability of its Aloha-based MAC layer. The performance worsens further when using acknowledged transmissions due to the duty cycle restriction at the gateway. For this, we propose FREE, a fine-grained scheduling scheme for reliable and energyefficient data collection in LoRaWAN. FREE takes advantage of applications that do not have hard delay requirements on data delivery by supporting synchronized bulk data transmission. This means data is buffered for transmission in scheduled time slots instead of transmitted straight away. FREE allocates spreading factors, transmission powers, frequency channels, time slots, and schedules slots in frames for LoRaWAN end-devices. As a result, FREE overcomes the scalability problem of LoRaWAN by eliminating collisions and grouping acknowledgments. We evaluate the performance of FREE versus different legacy LoRaWAN configurations. The numerical results show that FREE scales well and achieves almost 100% data delivery and the device lifetime is estimated to over 10 years independent of traffic type and network size. Comparing to poor scalability, low data delivery and device lifetime of fewer than 2 years for acknowledged data traffic in the standard LoRaWAN configurations.

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Offline Scheduling Algorithms for Time-Slotted LoRa-based Bulk Data Transmission

Cited by 30 publications

References 8 publications

Short: Achieving Energy Efficiency in Dense LoRaWANs through TDMA

Short: Achieving Energy Efficiency in Dense LoRaWANs through TDMA

Optimal Data Collection Time in LoRa Networks—A Time-Slotted Approach

$FREE$ —Fine-Grained Scheduling for Reliable and Energy-Efficient Data Collection in LoRaWAN

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