--------------------------- Reviewer 1 English language and style ( ) Extensive editing of English language and style required ( ) Moderate English changes required (x) English language and style are fine/minor spell check required ( ) I don't feel qualified to judge about the English language and style Yes Can be improved Must be improved Not applicable Does the introduction provide sufficient background and include all relevant references? ( ) (x) ( ) ( ) Is the research design appropriate? (x) ( ) ( ) ( ) Are the methods adequately described? (x) ( ) ( ) ( ) Are the results clearly presented? ( ) (x) ( ) ( ) Are the conclusions supported by the results? ( ) (x) ( ) ( ) Comments and Suggestions for Authors The paper investigates the effect of placing TelosB motes at ground level to understand the wireless performance in this environment. Two ground level environments are investigated, a steep hill and a flat space. Overall the paper will be of interest to the WSN community as these practical realities need to be used in future work. However, there are two issues with the paper that limit the impact it will have. The first is that TelosB nodes are now old pieces of hardware and new WSN/IoT platforms have been released with improved hardware that may be better able to handle the situations described. The second is the decision to only use channel 11, 16 and 26 instead of a technique such as TSCH because using a single channel tends to perform poorly compared to channel hopping. Ideally there should be an additional set of experiments performing using TSCH to gauge its impact. For these experiments to be usable it would be very useful for the authors to create a new communications model in popular sensor network simulators (such as COOJA) that will allow other researchers to test in these environments. Especially as the results of Section 6 imply that existing link modelling approaches do not correctly simulate wireless links for certain environments. In terms of the related work it would be useful to also mention existing testbeds such as FlockLab and FIT/IoT-Lab and the physical environments that they exist in. For example, I believe that many of these sensors are ceiling mounted, so may have similar wireless characteristics to this analysis. · C. Adjih, E. Baccelli, E. Fleury, G. Harter, N. Mitton, T. Noel, R. Pissard-Gibollet,F. Saint-Marcel, G. Schreiner, J. Vandaele, and T. Watteyne. 2015. FIT IoT-LAB: A large scale open experimental IoT testbed. In 2015 IEEE 2nd World Forum on Internet of Things (WF-IoT). 459–464. https://doi.org/10.1109/WF-IoT.2015.7389098 · R. Lim, F. Ferrari, M. Zimmerling, C. Walser, P. Sommer, and J. Beutel. 2013.FlockLab: A testbed for distributed, synchronized tracing and profiling of wireless embedded systems. In 2013 ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN). 153–165. https://doi.org/10.1145/2461381.2461402 It may also be useful to cover some work that has looked at the impact of varying other aspects of WSNs, such as transmit power (especially as you do not consider the impact of varying transmit power in this work): · M. Bradbury, A. Jhumka, and C. Maple. 2019. The impact of decreasing transmit power levels on FlockLab to achieve a sparse network. In Proceedings of the 2nd Workshop on Benchmarking Cyber-Physical Systems and Internet of Things (CPS-IoTBench '19). ACM, New York, NY, USA, 7-12. DOI: https://doi.org/10.1145/3312480.3313171 I would also ask that the authors supply: (i) the source code for the application they implemented, (ii) the raw results gathered and (iii) the scripts used to analyse these raw results and (iv) a readme that describes the procedure to reproduce these experiments. Without these details it will be almost impossible for others to validate these experimental results. On page 20 you state that “frequency hopping is better”, however as you have not testing frequency hopping in this work you cannot claim that it is better. Please either provide a citation or perform additional experiments demonstrating the superiority of frequency hopping. Also, on page 20 you state “very small messages should be avoided” in recommendation number 5. I think it would be very useful to expand your investigation as to why this is the case. In section 6 you presented Figure 15 for the PRR validation, could you also include a figure for the RSSI validation. Overall, I think this is an interesting piece of work, that with a few minor changes could be very useful to the WSN community. Other minor issues: · In Figure 12 "Mediane" should be spelt "Median" · Line 543 on page 20, "results presented in Figure 10" should be "results presented in Figure 11" · On page 12 line 369 you state that there is a “non-negligible percent of poor links”, please quantify this (at what point is the number of poor links significant?) · It would have been useful to present the noise floor on the three different channels in Figure 5. · Change spelling of “heigth" to “height” (including in multiple figures such as Fig. 5 --------------------------- Reviewer 2 English language and style ( ) Extensive editing of English language and style required ( ) Moderate English changes required (x) English language and style are fine/minor spell check required ( ) I don't feel qualified to judge about the English language and style Yes Can be improved Must be improved Not applicable Does the introduction provide sufficient background and include all relevant references? ( ) ( ) (x) ( ) Is the research design appropriate? ( ) (x) ( ) ( ) Are the methods adequately described? (x) ( ) ( ) ( ) Are the results clearly presented? (x) ( ) ( ) ( ) Are the conclusions supported by the results? ( ) (x) ( ) ( ) Comments and Suggestions for Authors The authors propose a model for characterizing the link behavior in the WSN context. The idea sounds interesting and scientific; however, diverse points should be clarified: 1) Overall, the paper is well written and organized. The sections were divided properly and it is very easy to understand the message/contribution of the work. 2) WSN is a very consolidate are with more than 15 years of contributions. There are a vast number of contributions in the literature regarding characterizing of the link or physical layer (simulation, real experiment, mathematical models, so on). Despite of excellent organization of the text, it is not clear the contribution of the paper when compared with literature. The references are outdated, and a complete major revision is necessary for discussing recent works (2018, 2019, mainly). 3) Sections 1 and 2 do not clarify the contributions when compared with literature review. 4) It is not clear how figure 2 was generated. 5) The authors should introduce algorithms in Section 4 in order to describe, in a formal way, the methodology used in the results. It is imperative the describe this methodology to anyone can reproduce the results. 6) Sections 6 and 7 are the main contributions of the paper. That Sections could be merged. 7) Regarding all results, what is the confidence interval of them? This is very important due to reproducibility issues.