A Method for the Analysis of Interference from DME to ATCRBS in the Time Domain

Round 1

Reviewer 1 Report

This paper derives an analytical model to evaluate the DME interference to ATCRBS. The proposed model was verified against Monte Carlo Method. The advantage of the proposed model is that it is an analytical model and it provides accuracy under a low number of interference condition where Poison Distribution Method shows discrepancy. 

EMC is a big concern of the aviation community, and this work enhances understanding of the interference mechanism in the frequency band. Therefore, I recommend "Accept after minor revision". I have few comments for a better manuscript as follows.

1. I would recommend to add few more references to emphasize the importance of EMC study in this band. For example:

[1] T.Otsuyama, et al, ``A study of evaluation method for aeronautical L-band signal environment during flight experiments,'' 2014 International Symposium on Electromagnetic Compatibility, 2014.

[2] Khodr A. S., ``Cancelation of Distance Measuring Equipment Interference for Aeronautical Communications,''  IEEE Transactions on Aerospace and Electronic Systems, Vol. 53, No.6, Dec. 2017.

2. Please explicitly summarize the assumptions of the model in the body text (anywhere is OK). As you mentioned in the conclusion, the proposed model ignores signal processing time. In addition, mobility of aircraft (this changes the timing of ATCRBS replies and DME interrogations), inteference from other aircraft (ATCRBS, DME, and Mode S), rotation of interrogating antenna are not considered. 

3. Please add k, delta t_12kr to Figure 4.

4. In 3.2.3, the reference number is missing ([?] appears).

5. In 3.2.3, can you add explaination on what m or (k - 1)T_1 + mg = 0 mean?

6. In page 6, the equations are hard to read. One suggestion is to denote a frequently appearing factor "T_2 / g" by a new variable.

7. Can you add explaination on how equation (20) is derived? It is said the mean value, so I guess numbers of overlap are multiplied by probabilities. 

8. Please explicitly show the equation you calculated for Table 1, although there are some text. For example, in "1 - 24.3 f_2", which equation number corresponds to "24.3" or "24.4 f_2" ?

9. In 4.1.3, I would recommend to add N_all_ov_av and P_all_ov_av for PPOM and MCM as a verifiction of your equations.

Author Response

Response to Reviewer 1 Comments

This paper derives an analytical model to evaluate the DME interference to ATCRBS. The proposed model was verified against Monte Carlo Method. The advantage of the proposed model is that it is an analytical model and it provides accuracy under a low number of interference condition where Poison Distribution Method shows discrepancy.

EMC is a big concern of the aviation community, and this work enhances understanding of the interference mechanism in the frequency band. Therefore, I recommend "Accept after minor revision". I have few comments for a better manuscript as follows.

1. I would recommend to add few more references to emphasize the importance of EMC study in this band. For example:

[1] T.Otsuyama, et al, ``A study of evaluation method for aeronautical L-band signal environment during flight experiments,'' 2014 International Symposium on Electromagnetic Compatibility, 2014.

[2] Khodr A. S., ``Cancelation of Distance Measuring Equipment Interference for Aeronautical Communications,''  IEEE Transactions on Aerospace and Electronic Systems, Vol. 53, No.6, Dec. 2017.

Response 1: We read references that you recommended, then revised introduction and added the references. 

2. Please explicitly summarize the assumptions of the model in the body text (anywhere is OK). As you mentioned in the conclusion, the proposed model ignores signal processing time. In addition, mobility of aircraft (this changes the timing of ATCRBS replies and DME interrogations), inteference from other aircraft (ATCRBS, DME, and Mode S), rotation of interrogating antenna are not considered.

Response 2: We summarized the assumptions of the model at the beginning of section 4. 

3. Please add k, delta t_12kr to Figure 4.

Response 3: We added k, delta t_12kr to Figure 4. 

4. In 3.2.3, the reference number is missing ([?] appears).

Response 4: We added the number of reference. 

5. In 3.2.3, can you add explaination on what m or (k - 1)T_1 + mg = 0 mean?

Response 5: We explanation the equation and its parameters in 3.2.3.

6. In page 6, the equations are hard to read. One suggestion is to denote a frequently appearing factor "T_2 / g" by a new variable.

Response 6: T_2 / g is defined as Equation (6), so we replace it with (N_T1).

7. Can you add explaination on how equation (20) is derived? It is said the mean value, so I guess numbers of overlap are multiplied by probabilities.

Response 7: According to equation (22) (equation (19) in the old version), N_{all_ov}  changes with ε₀, the mean value of N_{all_over} can be calculated as equation (23) (20 in old version) in a period of ε₀.

8. Please explicitly show the equation you calculated for Table 1, although there are some text. For example, in "1 - 24.3 f_2", which equation number corresponds to "24.3" or "24.4 f_2" ?

Response 8: We added the derivation for calculating mean recognition probability for Table 1.

9. In 4.1.3, I would recommend to add N_all_ov_av and P_all_ov_av for PPOM and MCM as a verifiction of your equations.

Response 9: We are sorry for our mistakes, in fact, as mentioned in the paper, P_all_ov_av is defined as mean recognition probability and depicted in Figure 6. However ,we made a mistake for labelling “recognition probability” as “mean recognition probability” in the old version. In the new version, we plot MRP and the mean recognition number  VS PRF of DME in Figure 6, MRP is ploted on the left Y axis, the mean recognition number is plotted on right Y axis, and X axis represented PRF of DME.

Thank you for your comments and suggestions.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,

first - I am an expert on EMC area, especially for measurement and simulation of EMC phenomena. I am professor at university and I am working in an accredited EMC laboratory.

I am a little confused from the content of your paper. I have a little different view to EMC than you – in my point of view, EMC represents a robustness of the electrical system against to the other types of interferences and with low rate of their own emissions.

Of course, the frequency domain is important in DUT analyzing – most of the standards are based on dependencies of limit lines to the frequency; or – for the immunity testing – the normalized pulses waveforms could be transform to the frequency domain.

If I speak about time domain (simulation), the result is given by the time response of the system to some type of the input signal. And the result is almost always transform to the frequency domain.

Your view of EMC is based on the time slotting of the useful signals (there are useful signals of the services – in your case DME and ATCRBS). Yes, the signal from the second source could represent an interference for the first one, but it is a problem of the signal distribution of the service (for example in the frequency or in evaluation on board).

It is not EMC problem, but it is a problem with evaluation of the received signals - in my point of view.

I hope that your calculation are correct – I see some type of cross-correlation of the signals (it is my simplified view to the issue).

In my point of view – the terms "EMC" in your paper should be replaced by some different term, for example "correct evaluation of signals" or something like this – maybe I am wrong in this issue and I need your response, please.

Thank you.

Best regards

Zdeněk Kubík

Author Response

Response to Reviewer 2 Comments

first - I am an expert on EMC area, especially for measurement and simulation of EMC phenomena. I am professor at university and I am working in an accredited EMC laboratory.

I am a little confused from the content of your paper. I have a little different view to EMC than you – in my point of view, EMC represents a robustness of the electrical system against to the other types of interferences and with low rate of their own emissions.

EMC is defined as “ability of equipment or a system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment” under International Electrotechnical Commission (IEC), which corresponds with your point. I think that if the victim equipment cannot function satisfactorily owning to the electromagnetic interference, the victim equipment and interfering equipment are not regarded to be compatible. Correspondingly, analysis of interfering signal impact on wanted signal can be considered to be EMC research.

Of course, the frequency domain is important in DUT analyzing – most of the standards are based on dependencies of limit lines to the frequency; or – for the immunity testing – the normalized pulses waveforms could be transform to the frequency domain.

If I speak about time domain (simulation), the result is given by the time response of the system to some type of the input signal. And the result is almost always transform to the frequency domain.

According to Wikipedia, time domain is the analysis of mathematical functions, physical signals or time series of economic or environmental data, with respect to time. So I consider that the signal collision changing with time should be in the time domain. The main purpose of transformation of time domain to frequency domain is to make it easier for analyzing problem. Since both signal durations of ATCRBS and DME have small duty cycle, i.e., they don’t overlap with each other most of the time, then, it is possible for them to share spectrum, the paper attempts to analyze the coexistence between DME and ATCRBS on system-level by calculating probability of signal collision VS time. In this paper, there are three assumptions, one is that interfering equipment (DME) and victim equipment (ATCRBS) operate at the same frequency, the second is that the power of interfering signal from DME is strong enough to make ATCRBS work incorrectly, finally, if interfering signal duration overlaps with wanted signal duration in the time domain, ATCRBS is thought to be interfered by DME and they are not regarded to be compatible.

Your view of EMC is based on the time slotting of the useful signals (there are useful signals of the services – in your case DME and ATCRBS). Yes, the signal from the second source could represent an interference for the first one, but it is a problem of the signal distribution of the service (for example in the frequency or in evaluation on board).

ATCRBS and DME had been used for many years and their signal distributions are definitive. In order to avoid potential interference, they operate in time division multiple address when they are fitted in the same aircraft, however, with the increase of number of aircraft, the distance between two aircraft becomes nearer than before, then it is possible for DME fitted in a aircraft to interfere ATCRBS fitted in another aircraft when the two aircraft are near enough. Analyzing signal collision in the time domain is a way to analyze their coexistences.

It is not EMC problem, but it is a problem with evaluation of the received signals - in my point of view.

In my point of view, it is a problem with evaluation of the received signals, and it is also an EMC problem. If the received signals of ATCRBS overlap with DME signals, ATCRBS can be thought to be interfered by DME, moreover, if the probability of collision is larger than specified value, ATCRBS and DME are not thought to be compatible; otherwise, the received signals of ATCRBS is correct.

I hope that your calculation are correct – I see some type of cross-correlation of the signals (it is my simplified view to the issue).

We reviewed the calculations again, and we are sure that they are correct. They are based on mathematical derivations and consistent with simulations.

In my point of view – the terms "EMC" in your paper should be replaced by some different term, for example "correct evaluation of signals" or something like this – maybe I am wrong in this issue and I need your response, please.

As mentioned above, in my point of view, research on electromagnetic interference between two or more equipment can be thought to be in EMC area. Maybe I extend the conventional view of EMC and I am wrong in the view of EMC. To avoid ambiguity and misperception, we replace “EMC” in the paper with “coexistence” or similar expression.

Thank you for your suggestions

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear authors,

I would like to thank you for your answers; I really appreciate changes in your manuscript. As I wrote before, your paper is based on slightly different perspective than mine - I am not sure, if I can make some relevant decision about content of the article, but I think that the manuscript could be published at a current form.

Thank you.

Best regards

Zdeněk Kubík