Gateway Energy-Oriented TDMA for LoRa Networks

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors address a gateway energy oriented communication protocol for LoRaWAN
networks, which offers fine granularity in energy consumption. The work is interesting, but some minor adjustments would warrant a better clarity of manuscript.

Battery capacity in Table 1 is redundant. It can be determined from previous parameters: 90 Wh at 12 V. You should keep one value: either 90 Wh, or 7500 mAh.
It is better to number and place the figures in the order they are mentioned in the text. The authors should mention Fig 4 before Fig. 5 in the text, not the other way around. The same thing happens with Fig. 7 and 8. They are mentioning Fig. 8 before Fig. 7. In my opinion, they shouldn't mention Figure 8 here at all, because this section is for uniform distribution. It's better to move this statement where it belongs, in the section 5.2.

Also, for an easier reading, the actual figures should be placed after they are mentioned in the text and, again, in the same section. For example, Figure 4 and 5 are mentioned in the beginning of chapter 5, but the figures are placed in the section 5.1, where figures 6 and 7 are, in fact, described. The same is true for Fig. 13.
At line 497, replace "above Figs" with actual figure numbers for better clarity.

Another issue: the authors should correctly write the numbers with commas separation and measurement units separated by a blank character (e.g., at lines 490-497).

In the Conclusion section, the authors should present in short the demonstration stated in the abstract: " The analysis reveals that, in comparison to an established solution customized for the getaway operation, GEOT succeeds in extending the network operation up to 6 times". In other words, they should present the results from the conducted analysis in a clear and concise manner.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this work a Time Division Multiple Access (TDMA)-based protocol is tested for the energy longevity of the GWs in a LoRa network. My detailed comments and suggestions are as follows:

1. The paper repeatedly asserts the renewable energy sources, yet offers no renewable energy-harvesting or power‐consumption model, nor any analytic or numeric validation. Without modeling the solar-generation profile, payload constraints, or energy‐budget trade‐offs, these statements remain speculative.
2. In fact, LPWAN is not a brand new scenario, there are still a lot of research works, which focuses on the communication issue of LPWAN. As the reviewer knows, there are even multiple papers which have adopted the TDMA schemes for LPWAN. However, the literature review of the current paper missed these papers. In addition, this also affects the novelty of the current paper.
3. Key contribution of the paper should be mentioned in bullets form at the end of introduction section. In addition, text in figures is not clearly visible, authors need to enhance the figures completely.
4. Related work is not comprehensive enough and literature is not well studied. Authors need to enhance related work and do also add up a table in related work discussing the advances, drawbacks, key contributions, and loop holes of previous work in accordance with the presented work.
5. Some practical applications on the TDMA technologies should be investigated and discussed in this paper. a) "Outage Probability Analysis of MISO-NOMA Downlink Communications in UAV-Assisted Agri-IoT With SWIPT and TAS Enhancement," in IEEE Transactions on Network Science and Engineering; b) "Full-Duplex UAV Relaying for Multiple User Pairs," in IEEE Internet of Things Journal (the author is free to cite recommendations).
6. The parameters for the TDMA scheme and LPWAN have not been provided accurately. For instance, how many time slots are allocated for communication? What to do in case of a collision; how are the number of antennas and transmission power of the nodes set?
7. The future research directions section is quite brief.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper presented proposals a gateway energy oriented communication protocol for long-range networks which offers fine granularity in energy consumption. Analysis and simulations were also preformed to verify the proposed protocol. Besides, the paper exhibited satisfactory organization, but the language should still be carefully checked and revised. Additionally, some issues should be carefully addressed before further consideration.

 

1. In the abstract, the authors should address the research motivation and the novelty of this work. Besides, the result description of the proposed protocol should be shortened into less than two sentences. Additionally, the authors should provide the numerical results in the abstract for verification.
2. In the introduction, the authors are suggested to list out their main contributions in an isolate paragraph.
3. In the related work, the way of citation should be checked and revised, such as “Similarly, [25] Jabbar et al. developed a renewable energy–powered LoRaWAN system for water quality monitoring in remote regions, showing that variability in environmental energy availability may lead to service disruption when the power supply is depleted” in Line 117.
4. The language mistake, such as in Line 134, should be revised. And the long sentence as in Line 135 is suggested to be divided into several shorter sentences.
5. In the section IV, the flowchart of the proposed protocol is suggested to provide.
6. In Equation 1, the authors are suggested to rewrite in the form with more details, especially the F function in Line 280.
7. In Equation 2, the authors should provide more explanation for the selection of S.
8. In section V, the authors considered “a system consisting of 2000 static EN in total shared among 3 GWs randomly positioned”, I wonder if the change of the number of EN or GWs will affect the simulation results.
9. For the simulation results, I suggest the authors to describe the results in percentage instead of absolute value, which may help indicate the improvement.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

In this manuscript, the authors research the effects of the energy consumption of the gateways， and propose a novel communication scheme. The results are reasonable and intriguing, and it can be accepted for publication after minior revisions. The detail comments are listed as follows:

1.The manuscript assumes gateway operation on renewable energy but omits consideration of supply fluctuations(e.g. the diurnal energy variations in solar generation, power reduction during cloudy conditions). It would be valuable to incorporate an energy supply model under such unstable power conditions and explain whether the model will affect the lifespan of the node.

2.In section 4, the authors assume that the portion of the timeslot is at the levels of µs when there is a high data rate of the uplink(1Mbps). However, in remote areas, the LTE rate may be lower than 1Mbps, which will extend the timeslot to the ms or even s level. Under such circumstances, will the LTE transmission energy consumption of the gateway increase significantly? It is necessary to re-verify the impact of timeslot on the gateway's lifetime.

3. 3.In section 4.2, GEOT reduces gateway listening time through "node reassignment andSF-grouped parallel transmission". However, when multiple nodes are assigned to the same SF timeslot of the same GW, whether data packet loss will occur due to LoRa co-channel interference? If such interference exists, whether GEOT is equipped with an interference avoidance mechanism?
4. 4.Table 1 only provides the power consumption of various static states in the GW (e.g., sleep: 1.8 W, listen: 6 W), but does not consider the energy consumption when the state transits(e.g., GW-sleep to listen or GW-listen to sleep). It is recommended to incorporate a transition energy model to avoid underestimating the actual gateway energy consumption and ensure more accurate lifetime analysis.
5. In section5, each GW was equipped with a 90Wh battery. However, in practical off-grid scenarios, GW may employ batteries of different capacities(e.g., 45Wh, 180Wh). It would be valuable to supplement the analysis with a comparative evaluation of network lifetime under different battery capacities. This would effectively validate GEOT's adaptability under diverse energy constraints.

6.Please carefully check if the formulas in the article are correct.

7.Please carefully examine the grammatical errors and typos in the manuscript.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Accept in present form.

Reviewer 3 Report

Comments and Suggestions for Authors

All my concerns have been addressed with satisfactory.

Reviewer 4 Report

Comments and Suggestions for Authors

 Accept in present form