Performance Investigation of Peak Shrinking and Interpolating the PAPR Reduction Technique for LTE-Advance and 5G Signals
Round 1
Reviewer 1 Report
The manuscript comes with a new PAPR reduction technique for OFDM signals. The paper is interesting and has some merits to be conveyed to the community.
On the other hand, I would suggest a couple of issues:
1. Why the inclusion of the words "LTE-A and 5G signals" in the title is not worthy. The paper does not work with LTE-A and 5G signal at all. Rather, the paper works on OFDM-based systems in general. The paper is basically an extended version of their conference paper. It does not mean the technique is a new one. So, the inclusion of the word "Extended" in the title is also misleading. Indeed, PAPR is an OFDM issue. So, I recommend authors to change the title similar to "Performance Analysis of Peak Shrinking and Interpolating PAPR Reduction Technique for OFDM-based systems".
2. The length of introduction is not sufficient. Please discuss more on OFDM and OFDM-based systems in general. At this place, it would be nice if authors can add an extended discussion on 5G systems in general and high capacity enabling techniques for 5G such as mmWave, ultra-dense networks, and beamforming.
3. To support high capacity for 5G systems, OFDMA must be integrated with advanced radio access techniques such as NOMA. Please provide some insights into how the proposed extended PSI can be combined with the power domain NOMA. The paper "Resource Allocation for Downlink NOMA Systems: Key Techniques and Open Issues (IEEE Wireless Communications, 2018)" can be included as a reference in this discussion.
4. Providing reference in the Abstract is not a good practice.
Author Response
Response to Reviewer 1 Comments
Point 1: Why the inclusion of the words "LTE-A and 5G signals" in the title is not worthy. The paper does not work with LTE-A and 5G signal at all. Rather, the paper works on OFDM-based systems in general. The paper is basically an extended version of their conference paper. It does not mean the technique is a new one. So, the inclusion of the word "Extended" in the title is also misleading. Indeed, PAPR is an OFDM issue. So, I recommend authors to change the title similar to "Performance Analysis of Peak Shrinking and Interpolating PAPR Reduction Technique for OFDM-based systems".
Response 1: The PSI algorithm is indeed for OFDM based signals. The relationship between 5G, LTE, and OFDM, and associated PAPR effects are explained in the abstract and introduction sections. The title is also amendedas recommended, and “Extended” is replaced with “Performance Investigation”.
Point 2: The length of introduction is not sufficient. Please discuss more on OFDM and OFDM-based systems in general. At this place, it would be nice if authors can add an extended discussion on 5G systems in general and high capacity enabling techniques for 5G such as mmWave, ultra-dense networks, and beamforming.
Response 2: More discussions about 5G systems and how PAPR and OFDM play important role is further discussed, and the introduction’s length is improved as recommended. The authors endeavoured to balance the requests to shorten the Introduction from Reviewer 3, we have not extended the Introduction section greatly.
Point 3: To support high capacity for 5G systems, OFDMA must be integrated with advanced radio access techniques such as NOMA. Please provide some insights into how the proposed extended PSI can be combined with the power domain NOMA. The paper "Resource Allocation for Downlink NOMA Systems: Key Techniques and Open Issues (IEEE Wireless Communications, 2018)" can be included as a reference in this discussion.
Response 3: Non Orthogonal Multiple Access technology associated with 5G networks is studied, and related discussions are added in the Introduction. References for OFDM-NOMA technology from two journals, including IEEE Wireless Communications journal, are studied and cited as recommended.
Point 4: Providing reference in the Abstract is not a good practice.
Response 4: The reference in abstract was for the original paper, however it is removed as recommended.
Reviewer 2 Report
This paper is generally well written. The topic of reducing PAPR in OFDM systems is worth investigating. The contents are quite close to the level of publication. My comments are listed as follows:
1. Conventionally we don’t see a lot that a reference number is shown in Abstract. It is better to describe PSI technique in a couple of sentences. Also, ACPR is not defined, while PAPR has been defined twice.
2. I also suggest that those items in Keywords should be found in Abstract as well. The manuscript is an extended version of the authors’ previous work. Please review the contributions in [1], describe the differences between these two, and highlight the new contribution of this paper.
3. It considers many forms of signals in the title and subsection 3.5, such as LTE and 5G. Please describe the connections between these wireless communication systems and the OFDM signals used in the simulations and the experiments in this paper.
4. Is there any possible factor that could influence the degree of performance improvement? It seems that a stable 4dB reduction on PAPR is supported under various conditions, based on the results in this paper.
Author Response
Response to Reviewer 2 Comments
Point 1: Conventionally we don’t see a lot that a reference number is shown in Abstract. It is better to describe PSI technique in a couple of sentences. Also, ACPR is not defined, while PAPR has been defined twice.
Response 1: The reference number in abstract was for referring to the original paper, however it is removed as recommended.
More description of the PSI technique is added as “The main idea behind the PSI technique is to extract high peaks, scale them down, and interpolate them back into the signal” in abstract, and also in Section 2, page 4.
More explanation about ACPR and definition is added as “…ACPR or ACLR is a measure that shows a ratio between the powers of adjacent channel to the main channel’s power….” In 4th paragraph of Section 3.4, page 14.
Point 2. I also suggest that those items in Keywords should be found in Abstract as well. The manuscript is an extended version of the authors’ previous work. Please review the contributions in [1], describe the differences between these two, and highlight the new contribution of this paper.
Response 2: The abstract is improved according to the suggestions. All keywords are mentioned in abstract.
The main contribution of [1] is mentioned as:
“The main idea behind the PSI technique is to extract high peaks, scale them, and introduce them back into the signal. It is shown that PSI technique is a possible candidate for reducing PAPR without adding on computational complexity, compatible for existing and also future telecommunication systems such as 4G, 5G and beyond”.
The difference between this paper and [1] is explained as:
“In this paper, the PSI technique is tested with …. Additional work has been carried out to compare the …. This paper further validates the PSI technique ….Results show improvement in … furthermore the ….”. Last paragraph of abstract.
Point 3. It considers many forms of signals in the title and subsection 3.5, such as LTE and 5G. Please describe the connections between these wireless communication systems and the OFDM signals used in the simulations and the experiments in this paper.
Response 3: The connection between LTE, 5G, and OFDM is indicated to the reader in the abstract and the introduction section.
Point 4. Is there any possible factor that could influence the degree of performance improvement? It seems that a stable 4dB reduction on PAPR is supported under various conditions, based on the results in this paper.
Response 4: As explained in Section …., 4dB reduction in PAPR is the minimum reduction that makes a technique practical according to IEEE standard, however it is shown that besides the type of signal, and length of IFFT, two parameter of Number of slices (NS), Surrounding/Skirt dimension (SUR), Shrinking Ratio (SR), and iteration number of the PSI algorithm (RP) have influence on this performance, and they are investigated and results for their relative influence on the performance are shown in Table 2, Figure 9, and Figure 10.
Reviewer 3 Report
In this paper, authors has presented PAPR reduction technique for different Wireless standard which is using OFDM. Following are the major concern:
Introduction is too lengthy. It is not required to explain the techniques which is already available in the literature. (Please focus on your work)
Comparison of your technique with other bench mark techniques for PAPR reduction is not given.
There is an information lost in the process of clipping and filtering. To measure this information lost, BER or SER is an important tool. Please provide BER or SER with your proposed technique and compare it with other bench mark methods available in literature.
Compare computational complexity with other bench mark methods available in literature.
In which standard of 5G, OFDM is using?
Author Response
Response to Reviewer 3 Comments
Point 1: Introduction is too lengthy. It is not required to explain the techniques which is already available in the literature. (Please focus on your work)
Response 1: Thank you, we have aimed to improve the introduction terms of making it more informative, and more related to today’s needs and today’s technology as per the request from reviewer 1. We have added a description of this work to the abstract.
Point 2: Comparison of your technique with other bench mark techniques for PAPR reduction is not given.
Response 2: In order to provide a fair comparison and assessment of this technique the PSI technique is compared with other techniques and results are shown in Table 1, and Table 4.
Point 3: There is an information lost in the process of clipping and filtering. To measure this information lost, BER or SER is an important tool. Please provide BER or SER with your proposed technique and compare it with other bench mark methods available in literature.
Response 3: The Error Vector Magnitude (EVM) is analysed in order to compare the modified signal with un-modified signal. For PAPR reduction, the EVM is possibly the most commonly used figure of merit to quantify the performance of a transmitter. When this error is minimized as shown in Section 3.1, and table 2, the chance that the channel affects the bits differently compared to un-modified signal is very low, however we would agree that this can be further analysed in future works and have added in the Conclusion “…Moreover Bit Error Rate (BER) and Symbol Error Rate (SER) can be investigated in future works.”
Point 4: Compare computational complexity with other bench mark methods available in literature.
Response 4: Computational Complexity of the PSI technique is analysed in Section 3.3.
Point 5: In which standard of 5G, OFDM is using?
Response 5: OFDM is indeed in use in all 5G NR protocols. The explanations and citations are added in introduction.
Round 2
Reviewer 1 Report
The authors did not address most of the issues I raised in my reviews. Moreover, they were very much careless to do their jobs while revision. So, the paper must go for another round of major revision.
Regarding point 1 you wrote:
"Response 1: The PSI algorithm is indeed for OFDM based signals. The relationship between 5G, LTE, and OFDM, and associated PAPR effects are explained in the abstract and introduction sections. The title is also amendedas recommended, and “Extended” is replaced with “Performance Investigation”."
You did not change the title of the paper. Remove the LTE/5G from the title. You didn’t work on LTE signal. You worked on OFDM signals. There exists a relationship between LTE/5G signal and OFDM. But, it doesn’t indicate that the work is on LTE signal. I didn’t find any LTE signal construction in your paper. Even, I don’t find what you have done according to your responses; totally inconsistent.
Regarding point 2:
I don’t find what is your new addition?
Regarding point 3 you wrote:
"Response 3: Non Orthogonal Multiple Access technology associated with 5G networks is studied, and related discussions are added in the Introduction. References for OFDM-NOMA technology from two journals, including IEEE Wireless Communications journal, are studied and cited as recommended."
I didn’t find the recommended paper (IEEE Wireless Communications) in your new references. You need to check it carefully and confirm the responses are true.
