Manuscript Number: PHYCOM-D-20-00058
Optimal Energy-Efficiency Under Power Allocation Beyond 5G
Dear Professor Kim,
Thank you for submitting your manuscript to Physical Communication.
I regret to inform you that the reviewers recommend against publishing your manuscript, and I must therefore reject it. My comments, and any reviewer comments, are below.
For alternative journals that may be more suitable for your manuscript, please refer to our Journal Finder (http://journalfinder.elsevier.com).
We appreciate you submitting your manuscript to Physical Communication and thank you for giving us the opportunity to consider your work.
Professor Michalis Matthaiou
Editor and Reviewer comments:
The authors consider the problem of energy-efficient heterogeneous cellular networks for 5G and beyond. In particular, they investigate the use of a C-RAN network of small cell base stations with limited fronthaul capacity.
The topic is relevant and timely, and the introduction of the paper describes it quite well. However, in my opinion, the quality of the paper is insufficient for journal publication. More importantly, I think the technical contribution lacks novelty and awareness of the state-of-the-art.
On page 4 of the Introduction the authors present a bullet-list of the novel contributions claimed in this manuscript. However, as far as I can tell, all four bullet points describe well-established and extensively researched problems in the wireless communication domain:
1) Instead of using a conventional cellular network, a C-RAN is used. Are the authors claiming the invention of C-RAN?
2) Instead of using base stations with backhaul, fronthaul is used. Again, the authors simply describe a well-known feature of C-RAN.
3) Beamforming - again, an extensively studied technique (and already operating in the real world) for cellular networks.
4) Each user is served by many APs. Again, although this is a more cutting edge topic, Coordinated Multi-Point, PHY layer network coding, distributed antenna systems all aim to address this challenge, so I was not sure how this contribution stands out from the state-of-the-art.
The performance evaluation section is also insufficient and poorly written. For example, page 14: "The power amplifier efficiency ¥ì is set to 2.4. The simulation results were conducted under MATLAB R20186a environment, running on an Intel Core i3-7100 3.90 GHz CPU with RAM of 8Gb." What does an efficiency greater than 1 mean? What MATLAB version is it? The RAM is 8 GB, not Gb, I am guessing? This is a minor point, but it reflects the overall quality of the manuscript.
The comparison with just a "conventional heterogeneous cellular network" does not look credible to me, as there is a myriad of proposed protocols and schemes for HetNets, including those focusing on the energy efficiency, so the authors would need to compare the performance with some of those.
From the reviewer's aspect, the current manuscript suffers from severe deficiencies. The presentation of the paper could be heavily improved. There are so many grammatical errors and typos throughout the paper, e.g., incorrect use of "a/an", "the" and wrong spellings. Also, abbreviations such as AP, CHCN and MIMO need to be used clearly throughout the paper. For details, please refer to the following:
1The system model has not been addressed properly. For example, "L" represents the number of users in pager 5, but in page 13, it is the number of AP. Also, "P" is the number of channels, but what is "P users" in page 12?
2. In System model, it is not clear to see how the system is modelled in terms of multiple antennas or single antenna for the users. The authors considered single antenna for the users in the system model, but massive MIMO (which may use multiple antennas for the users) is considered for the simulation. In this context, it is not clearly described why and how many antennas are considered for the small cell BSs and APs to employ massive MIMO.
3. In References, please use coherent reference format.