New Algorithm for a Fixed Right Shift Code to Support Different Quality of Services in Smart and Sustainable Optical Networks

Round 1

Reviewer 1 Report

 

This paper proposed a new algorithm for FRS code that is used for SAC-OCDMA.  Two detection techniques that are DD and SPD detection schemes, are used at the receiver, and a comparison is made between them. The system, when used SPD shows an improvement in the number of users, about 2.5% at 622 Mbps and 1.4 % at 1.25 Gbps and 2.5 Gbps. 

 

However, the language needs polishing and can be accepted after revision.

 

Author Response

Reviewer # 1

This paper proposed a new algorithm for FRS code that is used for SAC-OCDMA.  Two detection techniques that are DD and SPD detection schemes, are used at the receiver, and a comparison is made between them. The system, when used SPD shows an improvement in the number of users, about 2.5% at 622 Mbps and 1.4 % at 1.25 Gbps and 2.5 Gbps.

Reviewer#1, Concern:  However, the language needs polishing and can be accepted after revision.

Author response: We are very grateful for the Reviewer’s comment and we have made the necessary changes in the manuscript.  We have revised the text of the manuscript and have checked it thoroughly. We have fixed this and reviewed the article to fix all typo errors. Furthermore, the mistakes have been incorporated into the revised manuscript with English proofreading.

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript presented the a new algorithm for the right shift code to be used in optical fiber communication (OFC). The algorithm was designed to support different quality of services (audio, video, and data) for smart cities. This algorithm is based on varying the code weight for a certain number of users and transmitting a service to them. The manuscript required major modifications.

1. Abstract, summarize the numerical results of proposed work, and discuss how it outperforms existing works.

2. Related work should be mentioned in a separate section by highlighting the comparative analysis in tabular manner. What are the unique features of this study compared to the existing works?

3. Contributions should be highlighted in bullet points and justified literature

4. A ‘Research Gap’ section should incorporate which will states the purpose of the study

5. A detailed flow chart , related to the various steps proposed in this research paper must be incorporated for better under standing of the research. 

6. Different abbreviations must be discussed first before they used within the text. 

7. Authors mentioned that the proposed technique is less expensive, but it should be discussed based on the detailed economic analysis of all the components those will be utilized in the proposed system. 

8. Authors presented a comparative analysis with Ref [22] but more detailed comparative analysis with at least one more recent references must be incorporate. Authors can take a real case from existing smart cities and compare their work. 

9. In figures 16 and 17, authors must clearly discussed that what different colors represented in the graphs. 

10 . Authors mentioned that the proposed Algorithm for Fixed Right Shift Code can be utilized in smarty cities but noting is mentioned that how this technique can replace the existing system in the smart cities. further how the proposed technique out performs other techniques presently using in smart cities.  

Author Response

Response to Reviewers Comments

 

Dear Reviewers,

Thank you for taking the time to read this manuscript and for providing thoughtful comments and constructive suggestions. Your feedback has helped to improve the quality of this work. Please see below, in blue, our detailed response to comments.

 

Dear Editor,

We appreciate the reviewers' constructive feedback and suggestions, which helped improve our manuscript. We have carefully considered all the inputs and comments and revised the manuscript accordingly.

Also, we would like to thank you for the opportunity to resubmit our manuscript. Finally, we have addressed the reviewers' comments as detailed below.

We are uploading:

(a) our point-by-point response to the comments (below) (reply to reviewers),

(b) an updated manuscript with green highlighting indicating changes,

 

All corrections in the final submitted version of the paper (Modified Manuscript: word file) are highlighted in yellow.

 

 

 

 

 

 

 

 

 

 

 

 

Reviewer # 2

This manuscript presented a new algorithm for the right shift code to be used in optical fiber communication (OFC). The algorithm was designed to support different quality of services (audio, video, and data) for smart cities. This algorithm is based on varying the code weight for a certain number of users and transmitting a service to them. The manuscript required major modifications.

Reviewer#2, Concern #1:  Abstract, summarize the numerical results of proposed work, and discuss how it outperforms existing works.

Author response: The obtained results, when our system used SPD, shows an improvement in the number of users, about 2.5% at 622 Mbps and 1.4 % at 1.25 Gbps and 2.5 Gbps. It can support number of users up to 151 for video service at BER = , 300 for audio service with BER =  and 162 for data services at BER =  at data rate 1.25 Gbps. Furthermore, the system is simulated and shows transmission distances of 30 km at 1.25 Gbps and 6 km at 2.5 Gbps for video service, 80 km at 1.25 Gbps and 30 km at 2.5 Gbps for audio service, and 44 km at 1.25 Gbps and 13 km at 2.5 Gbps for data services. Our proposed system is suggested to be implemented in next generation passive optical net-work (NG-PON).

 

Reviewer#2, Concern #2:  Related work should be mentioned in a separate section by highlighting the comparative analysis in tabular manner. What are the unique features of this study compared to the existing works?

Author response#2: related work are done in separate section that is section 2 as

2. Related work

The demanding of varying the code weight is necessary to support different services at different bit rates [21]. Variable code weights have studied recently by researchers for supporting various data services.

In [22], variable ZCC (VZCC) code is studied with direct detection (DD) technique. This code requires larger code length to support different quality of services.

 In [23], VW Khazani-Syed (KS) code is studied. This code is found for even number of weights and for higher number of simultaneous users, it needs mapping technique for the same code weight and VW.

In [24], VW RD code is used for triple service which require to change the structure of encoder and decoder according to the variation of code weight.

 In [25], multi service (MS) code is proposed for providing variable quality of service through changing the number of codes on basic matrix without changing the code weight.

Table 1 Related published works.

Parameters	Ref. [22]	Ref. [23]	Ref. [24]	Ref. [25]
Code	VZCC	VW KS	VWRD	MS
Detection technique	DD	Complementary	DD	AND
Cross correlation	0	1	1	1
Code weights	Video: 4 Audio: 3 Data: 2	Video: 2 Audio: 4 Data: 6	Video: 3 Audio: 4 Data: 5	Video: 5 Audio: 2 Data: 4
Number of users	Video: 4 Audio: 3 Data: 5	Video: 3 Audio: 4 Data: 6	Video: 3 Audio: 3 Data: 3	Video: 5 Audio: 4 Data: 4
Total code length	35	41	24	31
Drawbacks	Variable weight lead to larger code length	Valid for even number of code weights	Fixed number of users with variable weight	Need code weight optimization if number of users are not equal for the different quality of services.

The unique features of this study compared to existing work is that we use simple structure of VWFRS code based on SPD detection technique and has flexibility in choosing any number of code weights either even or odd and can support large number of users at higher bit rates with longer transmission distance and that was given in Table 12 that shows a comparison between previous work and this work.

Reviewer#2, Concern # 3:  Contributions should be highlighted in bullet points and justified literature

Author response#3: Done in revised manuscript as

The main contribution of this paper are:

• Propose new algorithm for fixed right shift code (FRS) that can support different quality of services like (video, audio and data) to be used in optical fiber communication systems.
• Mitigate the interference that exist in the code through using different detection techniques like direct detection DD and SPD.
• Solving problem of using VW codes that require complicated structure of encoder and decode for transmitting different services.
• Study the performance of our proposed model analytically.
• Making simulation of small optical fiber communication network that used our proposed model.

 

Reviewer#2, Concern #4:  A ‘Research Gap’ section should incorporate which will states the purpose of the study

Author response#4: The unique features of this study compared to existing work is that we use simple structure of VWFRS code based on SPD detection technique and has flexibility in choosing any number of code weights either even or odd and can support large number of users at higher bit rates with longer transmission distance and that was given in Table 12 that shows a comparison between previous work and this work.

Author compliance:

Table 12. Comparison between our work and previous work.
		Ref. [22]	Ref. [23]	Ref. [25]	Present work
Code		VZCC	VWKS	VWMS	VFRS
Code weight	Video	6	6	5	5
	Audio	4	4	4	4
	Data	2	2	2	3
Number of users at 1.25 Gbps	Video	90	-	24	151
	Audio	81	-	24	300
	Data	100	-	24	162
Detection technique		DD	CD	AND	SPD
Transmission distance at 1.25 Gbps	Video	-	-	-	30
	Audio	-	-	-	80
	Data	-	-	-	44
Transmission distance at 2.5 Gbps	Video	-	-	-	6
	Audio	-	-	-	30
	Data	-	-	-	13
Complexity		High as it requires number of FBGs equals to number of bit “1”	High as its receiver consists of two branches, upper branch has FBGs equivalent to number of bit“1” and PD, while lower branch has FBGs equivalent to number of bit“0” and PD	High as its receiver consists of two branches, upper branch has FBGs equivalent to number of bit“1” and PD, while lower branch has FBGs equivalent to number of interferences bits with other code words and PD	Low as its receiver has only one branch has decoder, subtractive decoder, and one PD
Cost		Expensive	Expensive	Expensive	Less expensive

 

Reviewer#2, Concern#5: A detailed flow chart, related to the various steps proposed in this research paper must be incorporated for better understanding of the research.

Author response#5: Done in revised manuscript as

The flow chart that represents the steps of construction of FRS code is given in Fig. 2.

Fig. 2 Flow chart of FRS code construction.

 

 

 

 

Reviewer#2, Concern #6: Different abbreviations must be discussed first before they used within the text. Author response#6: We are very grateful for the Reviewer’s comment and we have made the necessary changes in the manuscript.  

Reviewer#2, Concern #7: Authors mentioned that the proposed technique is less expensive, but it should be discussed based on the detailed economic analysis of all the components those will be utilized in the proposed system.

Author response#7: Here we referred to less expensive as less components are used. Also, reference: H. Y. Ahmed, M. Zeghid, W. A. Imtiaz, and A. Sghaier.: Design an efficient SAC-OCDMA system based on coherent and incoherent optical sources to reduce capital expenditure. Opt. Quant. Electron. 50:435 (2018) doi:10.1007/s11082-0.18-1688-5, contain the following table of prices for each component.

Reviewer#2, Concern#8: Authors presented a comparative analysis with Ref [22] but more detailed comparative analysis with at least one more recent references must be incorporate. Authors can take a real case from existing smart cities and compare their work.

Reviewer#2, response#8: As analytical and simulation results are done first before applying in real life so most of works done for SAC-OCDMA are suggested to be implemented so we compare our work with other previous works used variable weight codes with different detection techniques that support triple quality of services. Table 12 are modified as

Table 12. Comparison between our work and previous work.
		Ref. [22]	Ref. [23]	Ref. [25]	Present work
Code		VZCC	VWKS	VWMS	VFRS
Code weight	Video	6	6	5	5
	Audio	4	4	4	4
	Data	2	2	2	3
Number of users at 1.25 Gbps	Video	90	-	24	151
	Audio	81	-	24	300
	Data	100	-	24	162
Detection technique		DD	CD	AND	SPD
Transmission distance at 1.25 Gbps	Video	-	-	-	30
	Audio	-	-	-	80
	Data	-	-	-	44
Transmission distance at 2.5 Gbps	Video	-	-	-	6
	Audio	-	-	-	30
	Data	-	-	-	13
Complexity		High as it requires number of FBGs equals to number of bit “1”	High as its receiver consists of two branches, upper branch has FBGs equivalent to number of bit“1” and PD, while lower branch has FBGs equivalent to number of bit“0” and PD	High as its receiver consists of two branches, upper branch has FBGs equivalent to number of bit“1” and PD, while lower branch has FBGs equivalent to number of interferences bits with other code words and PD	Low as its receiver has only one branch has decoder, subtractive decoder, and one PD
Cost		Expensive	Expensive	Expensive	Less expensive

 

Reviewer#2, Concern # 9: In figures 16 and 17, authors must clearly discussed that what different colors represented in the graphs.

Author response#9: These figures show the shape of eye diagram, while at large eye opening, it is the best time to sample so one can take the reading of Q-factor and BER from it as an example the reading of Q-factor can be taken from Fig. 18 (a)

Q-factor

Bit “1”

Bit “0”

Symbol duration

Best time to sample at large eye opening

 

Here Q-factor is equal to 6.64 and by using Eq. (22), the BER value is 9.2 10^-12.

Reviewer#2, Concern #10: Authors mentioned that the proposed Algorithm for Fixed Right Shift Code can be utilized in smarty cities but noting is mentioned that how this technique can replace the existing system in the smart cities. further how the proposed technique out performs other techniques presently using in smart cities. 

Author response#10:  Passive optical networks are already in place to provide high data rate services to end users in smart cities. However, the objective of an optimal system is to support more users in a smart city with high data rate transmission at lower cost. The existing codes in the literature are summarized in Table 1 with drawbacks. Compared to the available codes, the proposed code has the flexibility in choosing any code width. Thus, it can support large number of users at higher data rate and longer transmission range. Simulation results show that the implementation of our proposed code in the next generation passive optical networks (NG-PONs) can attain transmission range of 30 km with 1.25 Gbps data rate and 6 km with 2.5 Gbps for video communication services. Therefore, it can be utilized for real time video services including security monitoring and surveillance cameras in smart cities.  Similarly, it has been simulated to provide data rate audio services at a rate of 2.5 Gbps at a range of 30 km which can be increased to a distance of 80 km at 1.25 Gbps data rate. Therefore, it can be used for audio services broadcasting in smart cities. Moreover, it achieves 44 km at 1.25 Gbps for data services and can be utilized for IoT data applications in smart cities. Finally, the proposed solution achieves the second part of the primary objective for smart cities which is to increase the number of users when single photodiode (SPD) detection is adopted. Numerically, it increases the number of users up to 1.4% to keep data rate at 2.5 Gbps as well as 1.25 Gbps. It further increases the number of users to 2.5% at 622 Mbps. Technically, it can support 151 users for video services, 300 users for audio services, and 162 users for data services at 1.25 Gbps to maintain the desirable threshold values of bit-error-rate (BER) for each service.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Authors tried to incorporate most of the comments, raised by the reviewer. but still the comparative analysis can be presented in the form of some graphs for better understanding. 

Author Response

Dear Editor,

Thank you very much for your positive and valuable comments. It is highly appreciated. In the following sections, we address the reviewer 2 comment and our corresponding response.

Reviewer # 2

Reviewer#2, Concern:  Authors tried to incorporate most of the comments, raised by the reviewer. but still the comparative analysis can be presented in the form of some graphs for better understanding.

Author response: Figures 6, 7, and 8 in the manuscript show the comparison between recent previous works used variable weight codes as random diagonal (RD) and sigma shift matrix (SSM) and our work that used new algorithm for fixed right shift (FRS) code with two different detection techniques (direct detection and single photodiode detection technique)

Author Compliance: Figure 6 shows a comparison between our proposed VWFRS/SAC-OCDMA based OFC model and other SAC-OCDMA systems that use sigma shift code (SSM) code and random diagonal (RD) code at 622 Mbps and P = 4. It is noticed that our suggested model can support up to 100 users when used DD technique and 250 users when SPD technique at BER . While at the same BER value, the number of users is decreased to 56 and 43, respectively when SSM and RD code are assigned, respectively. 

The larger number of users is achieved by VWFRS/SAC-OCDMA OFC system when used SPD detection technique as this technique provides beating probability suppression between any two code sequences so that leads to MAI cancellation [29]- [30].

Author Response File: Author Response.docx