Intelligent Network Solution for Improved Efficiency in 6G-Enabled Expanded IoT Network
, Nitin Saluja 1, Shalli Rani 1,*, Aman Singh 2,3, Fahd S. Alharithi 4 and Sultan Mesfer Aldossary 5
Round 1
Reviewer 1 Report
The paper uses quite a detailed power consumption model to evaluate energy efficiency of a cell-free massive MIMO system, and in particular to find optimum AP density and evaluate the trade-off between spectrum and energy efficiency. This is an interesting issue and worthy of analysis.
The main deficiency of the paper is that it is not at all clear where the parameters used in the energy efficiency model come from: there doesn't appear to be a reference providing a source in section 3 where the parameters are listed in Table 2. Nor is there any justification of the values used: without this it is difficult to see what sort of system is being considered, and whether the values are appropriate. I am also concerned by some details of the power consumption model, and especially how the power consumption of the user terminals is accounted for - it seems that power consumption is proportional to the product of the number of APs and the number of users, which I'm not sure makes sense.
There are also some omissions in the description of other aspects of the network model, in particular of how the pilot allocation is performed (this could have significant impact on SINR and hence spectrum efficiency). I'm also concerned about the steep increase in spectrum efficiency at high AP density shown in Fig 2, which is unexpected and needs justification (otherwise it casts doubt on the results).
Other more minor comments are marked in my PDF copy of the manuscript, some listed here for convenience:
p2 l44 Network densification does not necessarily lead to increased power consumption 3 - if transmit powers are decreased in proportion to path loss reduction it might reduce power consumption.
p3 Fig 1 needs more explanation if it is to add anything useful to the paper
sect. 1.3 The "Related Work" survey is rather random: quite a lot of the references are irrelevant (e.g. SWIPT), and those included are not used to clearly motivate the need for the work described in this paper
Top of p6 Reference to \psi doesn't define mean square pilot symbol amplitude - presumably this is unity
sects 2.1 and 2.2 It would be useful to define the sizes of the vectors and matrices referred to here: it is difficult to confirm that the matrix equations are consistent
Following eq (7): C_i doesn't seem to be defined - and in any case an explanation of the meaning of the term Z_i here would be helpful
eq (14) isn't really a definition of APC
eq (15) needs explanation and/or a reference to its source
In section 4 "number of" is used repeatedly but is in fact redundant - for example instead of "100 number of setups" simply "100 setups" is correct English
p8 l 173 In Fig 3 ASE is plotted against pilot reuse factor, which is inverse to pilot length
In addition a number of typos, spelling errors and other English errors are highlighted.
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Reviewer 2 Report
The paper presents an intelligent network solution for improving energy efficiency in 6G enabled expanded IoT networks.
The proposed scheme aims to achieve maximum energy efficiency by the optimal allocation of pilot reuse factor and AP density for a given number of antennas at each AP and number of users.
Performance evaluation results collected by using MATLAB are also included in the paper.
The system model is well-defined.
Maybe the authors could use a network simulator to show the benefits and impact of the proposed scheme.
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Reviewer 3 Report
The authors propose ​an energy-aware network design based on a ​cell-free approach. ​ They define a power consumption model for the proposed network strategy and compute the power components related to data transmission, circuitry associated with the frontend radio frequency transceiver chains, signal processing, site-cooling, and backhaul. ​They provide an energy-efficiency analysis for schemes, ​evaluate the proposed design for average spectral efficiency, area throughput, and power consumption, and the impact of trade-offs between energy efficiency and area throughput on the system performance.​The paper provides good contributions but the evaluation of the proposed system is insufficiently explained. The authors should explain the graphs in depth and discuss the reasons behind the system behavior depicted in the graphs.
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