Evaluation of Multi-Beam Massive MIMO Considering MAC Layer Using IEEE802.11ac and FDD-LTE

Round 1

Reviewer 1 Report

This paper presents the simulation study of an adaptive modulation scheme which can be applied to the multi-beam massive MIMO. In my opinion, it is an interesting topic and the manuscript seems technically solid. But, I have following comments and concerns. 

- The organization of the paper should be improved, 

for example, there is only one subsection in Section 2 and 3.

- Typos

 . Multiple-output (MIMO) -> Multiple-Intput Multiple-output (MIMO)

 . This rest of this paper -> The rest of this paper, etc.

- English language should be improved. 

- Only simulation study has been performed, relevant level of theoretical analysis could be a plus. 

Author Response

Response to the reviewer comments

We thank the reviewers for taking time to review our submitted paper. We really appreciate their advice and comments, which were very helpful to us in improving our paper. Below, we present point-by-point responses to the reviewers’ comments. We have made every effort to address all issues raised in the previous review and to make the necessary adjustments to the revised manuscript.

Reviewer

This paper presents the simulation study of an adaptive modulation scheme which can be applied to the multi-beam massive MIMO. In my opinion, it is an interesting topic and the manuscript seems technically solid. But I have following comments and concerns.

Comment 1

- The organization of the paper should be improved,

for example, there is only one subsection in Section 2 and 3.

Response to 1:

We have corrected organization of Section 2 and 3, the both of subsections have been deleted.

In addition, the title of Section 2, “Massive MIMO transmission” has been changed to “Massive MIMO transmission and proposed system”.

We also added the following text in order to improve the context for Section 3.

“Here, we explain the beam-selection and amplitude correlation in multi-beam massive MIMO.”

Comment 2

- Typos

 Multiple-output (MIMO) -> Multiple-Intput Multiple-output (MIMO)

 This rest of this paper -> The rest of this paper, etc.

Response to 2:

We have corrected these typos. “Multiple-output (MIMO)” has been changed to “Multiple-Input Multiple-output (MIMO). “This rest of this paper” has been changed to “The rest of this paper”, etc.

Comment 3

English language should be improved.

Response to 3:

We have carefully checked the manuscript. The English was also revised by native speakers.

Comment 4

Only simulation study has been performed, relevant level of theoretical analysis could be a plus.

Response to 4:

Theoretical analysis about multi-beam massive MIMO is a future work and it will be clarified by experiment using the butler matrix circuit. Therefore, the following text has been added to the conclusion; Section 5.

“Future works include the further theoretical analysis and experimental evaluation using the analog multi-beam by Butler matrix circuit.”

Reviewer 2 Report

The simulation of massive MIMO over WiFi and cellular networks is important, and especially valuable for MAC layers.

The authors claim that CSI estimation is unnecessary, then what about multi-cell scenario and pilot contamination? Better to add some explanations along this line.

A minor comment: in the first paragraph of the introduction, 10 Gbps standard appears too low to me for next generation. Please do a check. 

Author Response

Response to the reviewer comments

We thank the reviewers for taking time to review our submitted paper. We really appreciate their advice and comments, which were very helpful to us in improving our paper. Below, we present point-by-point responses to the reviewers’ comments. We have made every effort to address all issues raised in the previous review and to make the necessary adjustments to the revised manuscript.

Reviewer

The simulation of massive MIMO over Wi-Fi and cellular networks is important, and especially valuable for MAC layers.

Comment 1

The authors claim that CSI estimation is unnecessary, then what about multi-cell scenario and pilot contamination? Better to add some explanations along this line.

Response to 1:

Since multi-beam massive MIMO system can perform beam-forming without CSI estimation, there is no need to consider pilot contamination in multi-cell scenario. To clarify this point, the following text has been added to Section 2.

“This system is also effective from the viewpoint of the pilot contamination problem in multi-cell scenario because the signals by multiple UTs without the CSI estimation by the multi-beam circuit.”

Comment 2

A minor comment: in the first paragraph of the introduction, 10 Gbps standard appears too low to me for next generation. Please do a check.

Response to 2:

We have modified this point by the following reference. "10 Gbps" have changed to "20 Gbps or more". We also added the following reference as [2] to the manuscript.

[2] Obara, T.; Suyama, S.; Shen, J.; Okumura, Y. Joint Processing of Analog Fixed Beamforming and CSI-Based Precoding for Super High Bit Rate Massive MIMO Transmission Using Higher Frequency Bands. IEICE Trans. Commun., 2015, E98-B 1474-1481.

Round 2

Reviewer 1 Report

The necessary revision has been appropriately made.