Round 1

Reviewer 1 Report

The article entitled "Effects of interference and mitigation using notch
3 filter for the DVB-S2 standard" discuss the effect
of the continuous wave interference (CWI) on a radio communication receiver, specifically with the Digital Video Broadcasting for Satellite Second Generation (DVB-S2) communication standard. Also, the notch filter is utilized as a solution to mitigate the interference.

The introduction of the paper presents a reasonably thorough review of the literature, emphasizing a great deal of recent work that has been published. Overall, the topic addressed in this work is an important area. The authors present very good theoretical background.  However, I have some remarks. The problem described in the paper is interesting, but I do not see specific novelties. I suggest to the Authors to add a section related to the state of the art of notch filters. Furthermore, the novelty of the proposed method compared with the state of the art must be clearly highlighted. I suggest adding a section after the introduction titled "Related works", where a deep description of the literature is reported. In this section, the disadvantages of the filters already proposed in the literature should be highlighted.

Why  just IIR is selected, is not explained. At least to be marked/mentioned, why IIR filters only are under investigation? By nature, differently from FIR filters, IIR filters have "non-linear-phase" (from frequency) relationship. In other words delay of the signal depends on the frequency, so the signal waveforms are distorted (by the delay variation of various signal parts and components). This "non-linear phase" or actually variable delay and the signal shape distortion are not mentioned in the paper.

Line 127 - unnecessary indentation.

Line 131 - What it is DVB-S2 10?

Line 132 - What it is "21" on the beginning of the line, and "the frame synchronization process 21" ?, also some Reference error occur in this line.

Line 136 - what it is major components 10?

Line 139 - what it is the Gardner algorithm 22?

Line - 142 what it is optimal communication 15?

Line 144 - what it is correct detection 23?

Line 149 - Reference error

Equation 1. the equation contains a lot of dots, it should be

???????? ?????? = ?????? + ??? = ? +?∙???(2??∙??∙?) ?

Line 162 - unnecessary indentation. 

Figure 2. Figure 3. The legend lies on the graph. I propose to change location of the legend. 

Figure 3 - in my opinion the dB should be in square brackets [dB]

Line 166 -unnecessary indentation. 

Line 178 - what it is channel 24?

Figure 4 - in my opinion the dB should be in square brackets [dB] and the legend cannot lies on the line of graph

Line 196 what it is Gardner (GA) algorithms 22? 

Line 201 - what it is Gardner symbol timing recovery 22?

Line 240 - what it is the frame 6?

Line 240 - " SOF" is not explained, why m is equal to 1 to 25? this is not explained.  That it is ???? and ???*?+1? 

Equation 14 ?^SOF is not explained

Line 249 "received frames have a delay equal to the 300th symbol time" why the delay is equal exactly to 300?, please explain this.

Equation 16 is not shown in proper manner well. Some of symbols like DC aren't presented in text.

Line 262 - How the 20% is calculated, at what frequencies?

Line 273- Why the CSOF is limited to 23?

Equation 17 is not mentioned in text.

Line 284 - what is the carrier frequency offset 21?

Line 286 - what it is the Luise & Reggiannini (L&R) algorithm 25?

Line 288 - why Llp is equal to 36?

Equation 24 - there is ?.??? or ?∙????

Lines 330-331 What it is the least mean square 26,  FFT 9 and,  Welch’s method 27?

Line 344 "The transfer function of an IIR M-order notch filter can be expressed as 18" In with way the Authors can express transfer function as a single number? And why the number is 18?

Line 348 - it is ?₀ or w0 like in line 328?

Figure 17. The legend should be moved to the bottom of the figure 

Line 356 - what it is the narrow range of frequencies 28?

Line 452 - what it is the filtering 11?

Line 453 - what it is the performance 30?

Line 456 - what it is the interference 26, 30?

In summary, it is this reviewer's opinion that the current version of this manuscript addresses an important topic. However, prior to final acceptance of this manuscript the authors should address the issues described above

Author Response

Hi Dear Reviewer,
Please kindly find the point-by-point response your comments in attachment.
Kind Regards,
Mohmmad 

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments

The paper deeply analyses the behaviour of the selected signal processing algorithms used for the reception of the DVB-S2 signal effected by CW interference. In the second part the authors use a notch filter for CW interference suppression and analyses reception improvementst.

The novelty (scientific contribution) can be seen in the analysis of the complete reception chain, unfortunately its scientific impact is not large.

Concerning the practical impact of the results. The CW interference is typical interference of the electronic devices (computer clock, local oscillator signals, and other harmonic signals that are radiated outside the device) not interference from other radio communication, navigation, radar, broadcasting ... systems as these radio systems uses modulated signals. The signals created by a non-linear or intermodulation distortions from modulates signals remain wideband.

The paper is too long because it analyses CW interference to each block of the receiver chain. The main problem of the paper is, that the authors selected one standard algorithm for instance for symbol timing. The analyses of the other algorithms based on different method and their mutual comparison are missing.

On the other hand, some explanation in the paper is too detailed and consequently too long. For instance, some formulas in (6) are redundant.

Comments to concrete parts

Line 36: The sentence "communication bands are getting narrower and busier" is questionable and confusing. The current trend is different. The bandwidth of the radios signals are getting wider and wider and terrestrial systems uses modulations with higher and higher spectral efficiency.

Line 132, 149: Problem with reference.

Figure 10: The DVB-S receivers widely use direct conversion architecture for conversion of the intermediate frequency signal from the satellite antenna downconverter to the baseband signal. This block is the main source of CW interference as the local oscillator oscillates on the middle frequency of the processed signal! The oscillator frequency causes a DC offset of the signal, that is a big problem. Simply speaking, this DC offset is suppressed by a feedbacks and by a AC coupling. So the receiver itself contains the notch filter tuned at the 0 Hz. This filter is very similar as the notch filter introduced in the second part of the paper for CW interference suppression.

In paragraph 3.3 authors presents probability of successful frame synchronization. This characteristic is not defined in the text. The authors should operate with frame synchronization error and probability of the frame detection.

It is not clear why the authors analyses probability for CW frequency offset 0.1 pi rad/samp. The sampling frequency was not specified. Some information can be deduced from Figure 3. It is not clear, how authors obtained this probability, whether by analytic formula, or computer simulation. In addition, the explanation of the results, why this characteristic is frequency selective (narrow peaks) are missing.

In this paragraph (paragraph 3.3) authors should analyse alternate methods the are not so frequency selective. The investigation of only one method is not sufficient.

The same remarks are to the paragraph 3.4. There are other carrier recovery algorithms, for instance blind algorithms, that do not require knowledge of the transmitted symbols. Some of them are based on Costas loop. These algorithms were not investigated.

The paragraph 4. contains expected results.

Author Response

Hi Dear Reviewer,
Please kindly find point-by-point response in the attachment.
Kind regards,
Mohammad 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The Authors take into account all of my comments. I propose to publish this article in Journal Telecom in the form it is presented. It will be quite interesting paper for the readers.

Reviewer 2 Report

The authors revised the manuscript and clarified key problems. The paper can be published in its current form as the results of the first preliminary step in the research of DVB-S systems interference.