Joint Channel Estimation and Synchronization Techniques for Time-Interleaved Block-Windowed Burst OFDM
Round 1
Reviewer 1 Report
The paper present a scheme for joint estimation and synchronization for TIBWB-OFDM. In my opinion the paper does not have enough novelty for publication. In fact, most of the paper is just presentation of existing techniques, and approaches for transmission/equalization/channel estimation. The core of the paper is the transmission protocol of Fig. 1 and the scheme of Fig.2. However, the proposed approach is quite trivial, with the transmission of a conventional preamble sequence used for synchronization and channel estimation. The algorithms for synchronization and channel estimation are minor variations (or exactly the same) of existing algorithms.
Thus, I do not see enough innovative content in this paper for publication.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper addresses the implementation of the TIBWB8 OFDM system in a more realistic and practical wireless link scenarios by addressing the challenges of proper and reliable channel estimation and frame synchronization. They incorporate a preamble formed by optimum correlation training sequences, such as the Zadoff-Chu (ZC) sequences to jointly estimate the frame beginning and acquire the channel state information (CSI).
The research is well described; a clear objective has been set. The theoretical models are marked and supported in the literature.
The technical terms have explained, and the topic of the paper is clear and understandable. The necessary background for the readers has been included in the paper. The methods and experiments are scientific solid.
I think this article has a good foundation and potential but, before being considered ready for publication, some aspects need to be clarified and improved.
1) Minor details on English grammar require review.
2)The bibliography is insufficient. My suggestion is to increase the number of references to allow for deeper discussion and comparisons with the state-of-the-art.
3)I suggest the authors add a section of Discussion highlighting the motivation of this research and summarize the challenges of previous studies. For discussion, I would like to know the limitations and the potential issues of this study. A discussion about the results obtained by this work and the previous works on this topic is necessary.
4) ) Moreover, conclusions can discuss future research directions and extensions of the study. The conclusion section could be further improved to highlight the simulation results.
5) I recommend the authors include more recent references and from MDPI as well.
In general, the article has a very well-formulated problem. Overall, the main contribution is clear and its presentation sufficient for a research article.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The paper uses the context of 5G as motivation, but the modulation format for 5G has already been chosen as conventional OFDM, with optional DFT-spread OFDM in the uplink. Therefore, the motivation might need some improvement.
Language is generally good, but can still benefit from additional proofreading (e.g. on page 2, the sentence starting on line 54 is strange)
The original version of TIBWB-OFDM is said to have better properties than regular OFDM regarding e.g. power efficiency and spectral confinement. The paper would benefit from some analysis and discussion whether this still holds after adding the ZC and additional ZP. Also, boosting the preamble by e.g. 6 dB may negatively affect PAPR, but I could not find anything on this topic either. Since TIBWB-OFDM was originally motivated based on its advantages in these areas, it is important to assess that it still performs well regarding those aspects when the scheme is modified.
In the introduction, it it said that the paper focuses on a more realistic scenario than earlier publications on this scheme, and that the radio channel can be highly dynamic. However, the paper does not include any analysis with mobility, which means that dynamic channels have not been evaluated. Also, the paper could have benefited from some performance comparison with traditional OFDM.
A lot of text is spent on the synchronization procedure (correlation), which is a common and well-known signal processing task. This part seems quite trivial and could be shortened a bit.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I still believe that the novelty is quite limited. Apart from this I do not have further remarks.
Reviewer 3 Report
The update done by the authors addresses my comments in a good way.
I still think that it is important (for future work) to compare the scheme with regular CP-OFDM and/or DFT-spread CP-OFDM (and possibly other schemes as well) for mobile users (e.g. 3 km/h, 30 km/h, ...). How will the scheme perform versus OFDM when channel coherence time is shortened and the block size must shrink to accommodate denser ZC bursts?
