Auction Mechanism-Based Sectored Fractional Frequency Reuse for Irregular Geometry Multicellular Networks

Round 1

Reviewer 1 Report

The authors should accurately address the below minor comments.

-          Acronyms must define before using in the first appearance such as CDF, PHPP … etc. This comment requires a response (please check the entire paper).

 

-          The authors did not respond to this comment. The main contribution/s should be made clear at the end of the introduction. Lines84-87 are not enough.

Author Response

The authors would like to thank the reviewer for the valuable and suggestions. The manuscript is revised accordingly. 

Author Response File: Author Response.pdf

Reviewer 2 Report

1. authors have presented cellular system with 8 cells' standard, which has not been used in any standard

2. frequency taken is 2 GHz, which is not normal standard, it should be clarified which standard is having this carier frequency

3. Equation 4 does not give any insight of advantage in its use

4. what does sub region means in the work is not clarified

5. BS does not have any auction capabilities in any standard

6. needs result analysis as it is based on hit and trial method and does not have standard specific input

Author Response

The authors would like to thank the reviewer for the valuable and suggestions. The manuscript is revised accordingly. 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1. the 8 cell concept has not been justified with the standards

2. the results are on hit and trial method and does not comply to the standards

3. concept should have been validated with standard frequency carier and band

4. how sectorisation is achieved is not visible in the paper

Author Response

Dear Reviewer,

The authors would like to thank you for the valuable comments/suggestions. All the comments/suggestions are addressed in detail, please find the attached file. 
Thank you for you kind cooperation. 

Best Regards,

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

Result analysis needs more input and text

cellular protocols to be explained

Author Response

Dear Reviewer,

Thank you very much for the valuable comments and suggestions that greatly help us to improve the quality of the manuscript. The detail of the corrections in the revised manuscript is attached, please find the attachment.
Thank you for your kind cooperation.

Best Regards,

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

1. Introduction

The concept of FFR seems very similar to Reuse Partitioning, which was first described at least 35 years ago. The introduction and some references should be updated to reflect this.

Since it seems like the proposed scheme can be applied to intercell interference in LTE and 5G, it could also be useful with some reference to ICIC/eICIC.

2. System Model

Practical sector antennas have lower gain at the edges of the sector than in the main direction due to antenna element radiation pattern (e.g., patch antenna or dipole over groundplane) and therefore the cell borders (Voronoi lines) will not be straight lines as opposed to Figure 1 in the paper. Maybe it is not critical for the results, but on a regular hexagonal grid, sites are placed at intersections between three hexagons (not in the center of a hexagon) to better reflect actual cell shapes.

In what way is the proposed auction-based scheme better than one where the BS makes scheduling decisions based on QoS requirements for different services and some prioritization of users based on their waiting time? In C-RAN (as in ref [3]), the information from many cells is available in the same location. Further, the BS has pretty good knowledge about the achievable throughput for a UE when allocated a specific set of subcarriers (from uplink measurements in TDD mode, or from UE reporting in FDD mode), and from buffer sizes, it should also know the short-term amount of data to send.

3. Proposed AMS-FFR Scheme

In practice, it is unlikely to have individual fading on each subcarrier since this would require an extreme delay spread in the channel. Further, in LTE and NR, it is not possible to schedule individual subcarriers, only resource blocks of 12 subcarriers. Coherence bandwidth is typically assumed to be at least a few resource blocks.

About selfish behavior (not telling the truth): If users falsely report too good channel conditions in LTE or NR, the BS will at least initially configure a too high modulation and coding scheme (MCS) for the particular channel, which means that the block error rate will go up and throughput will be reduced. If users report worse channel conditions, the selected MCS will be too low, which also leads to throughput reduction. Thus, current cellular systems already encourage reporting the truth.

How is the payment intended to work in practice? Will users get a limited set of tokens that they can use in the auctions, or is the intention that users should actually pay more for data when demand is high (leading to unpredictable monthly bills)?

4. Performance Analysis

Since you state that you model LTE, it is incorrect to use Shannon capacity. If we ignore practical limitations such as non-zero noise figure and transmitter distortions, there are limitations in link adaptation: For a single data stream between the BS and a UE, all subcarriers must use the same MCS, which means that throughput will at least partially be limited by the subcarriers with the worst channel condition. Depending on code rate, error correction could handle a fraction of subcarriers with bad channel conditions, but when this capacity is used up, it is the worst of the remaining subcarriers that will determine achievable throughput. Having individual modulation scheme for each subcarrier (as in ADSL/VDSL) would cost too much signaling over the air interface in a cellular system and thus reduce throughput.

It would have been good to also compare results with some full-reuse scheme, for example using random allocation of subcarriers (which might work well under low load and could be of interest as a benchmark in figure 7), and/or a centralized "genie" scheme with information from all cells (to see how much throughput is lost by your AMS-FFR at different loads).

General

The irregular grid is used in an attempt to model more realistic deployment, but other parts of the analysis are far from realistic (including modeling of LTE as commented above), which decreases the value of the results.

Can AMS-FFR be combined with MIMO, which is supported in practically all modern cellular deployments, including LTE and NR? What about beamforming, which is becoming popular in 5G?

Reviewer 2 Report

1. the basic concept taken by the athors is conflicting with the standards applicable for the proposed work

2. Dynamics of sectorisation and the modeling is not specified and explained in the work done

3. Maximising problem stated is not related to the secorisation scheme presented

4. how bidding for bandwidth is achieved; is not clear from the work not mathematical model is given with validation

5. Simulation parameters are not consistent with the scheme presented, the parameters arre for general cellular scheme

6. through put is just on the basis of hit and trial mechanism using simulation software and not based on concrete calculations

Reviewer 3 Report

The authors should accurately address the below comments.

-          Paper Title: It contains some acronyms (such as FFR) that makes it unclear. We recommend to replace them with words.

-          Keywords: We suggest that the authors should replace keywords such as “Auction Mechanism” because these keywords are already found in the article title. It is better that they replace them with other keywords to increase the reach of the article.

-          Acronyms must define before using in the first appearance such as OFDMA, BS, CDF, PHPP … etc.

-          Abstract: Authors should add numeric findings at the end of the abstract to make it more comprehensive.

-          The main contributions should be made clear at the end of the introduction.

-          English writing: This article requires minor proofreading, there are a little of typos and grammatical mistakes. The authors should carefully scrutinize the entirety of the article.

- References List: The number of references is sufficient for this study. Also, all references are related to the manuscript topic. However, the references should follow Electronics-MDPI style. For example, some search names in the reference list begin an uppercase letter for each word (such as [4], [5], [6] ... etc.) and others use only an uppercase letter in the first word (such as [1], [2], [3] … etc.), authors should standardize style. Authors should accurately check list of references to remove all problems.