Research on Resource Allocation Strategy of Indoor Visible Light Communication and Radio Frequency Systems Integrating Orthogonal Frequency-Division Multiple Access Technology

Round 1

Reviewer 1 Report

This paper focuses on the resource allocation strategy in indoor VLC/RF systems based on OFDMA. The joint subcarrier and power/resource allocation problem is solved by the Lyapunov optimization method without iteration. In the simulation results, compared to other algorithms, the proposed strategy can effectively balance the system queue length and transmission rate and improve the system stability and the average transmission rate. Several aspects of the paper require further improvement/clarification.

 

1.     For the practical VLC system, the diffuse path usually exists, although it is weaker than the LOS path. The diffuse path will cause different channel frequency responses at different frequencies. In other words, the fading of different VLC subcarriers will be different. Please provide more discussion about LOS+diffuse cases.

2.     In Page 6, Line 221, the definition of the channel gain H may be unclear. Is it the channel gain of each subcarrier, or the overall channel gain? What is the relationship between the channel gain H and the LOS gain in Eq.(2)?

3.     In Page 3, Line 114, some variable symbols are confused. “L” is reused for the set of APs and the number of VLC AP. “U” is reused for the user set and user numbers. The set of RF AP is written with “LRF.”

4.     There are some typos that need to be checked:

(1)     In Page 5, Line 200, a math symbol is missing in the definition of the complex Gaussian distribution. The same typo is in Eq.(30).

(2)     In Page 7, Line 264, there may be a typo in the formula [x,0]+.

(3)     In Page 12, Line 397, the text space is too large.

(4)     In Table 2, the unit of PD area is written as “cm2”, which maybe a typo.

(5)     In the top-right corner of Fig. 4, 6, 7, 8, and 9, there may be redundant tags (a) and (b). And the unit in the vertical axis of Fig. 6(b) may be missing.

(6)     The numbering of some equations is not aligned.

(7)     The layout of the optimization problem should be improved. For example, problem Eq.(27) should align each line as similar to problems Eq.(38) and Eq.(39).

 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

1.     Considering the inherent non-linearity of the VLC transmitters, how does the proposed resource allocation strategy mitigate issues related to non-linear distortions and signal degradation? What mechanisms are in place to ensure a high-quality transmission in the presence of such distortions?

2.     Could you elaborate on the potential crosstalk effects between the VLC and RF systems? How does the OFDMA strategy account for these effects and optimize resource allocation to minimize cross-system interference?

3.     To what extent does the OFDMA-based resource allocation strategy take into account cross-layer optimization? How are higher-layer parameters, such as quality of service (QoS) requirements, linked to the subcarrier allocation decisions?

4.     In a dynamically changing indoor environment, how does the strategy adapt to variations in user mobility, device density, and user behavior, and subsequently optimize resource allocation accordingly?

5.     Can you discuss the energy-efficient aspects of the proposed resource allocation strategy? How does it minimize the overall energy consumption of the hybrid system, considering the energy requirements of both VLC and RF transceivers?

6.     Could you extend the resource allocation strategy to scenarios involving multiple users and multiple cells, where interference management becomes significantly more complex? How does the strategy scale to accommodate such scenarios while maintaining high throughput and fairness?

7.     In a multi-user, multi-cell environment, how does the proposed OFDMA integration approach ensure that users in different cells, utilizing both VLC and RF systems, do not experience unfair treatment or excessive interference?

8.     Given the convergence of VLC and RF systems, what security challenges and vulnerabilities arise in this integrated communication paradigm? How does the proposed resource allocation strategy address security and privacy concerns?

9.     Author should briefly emphasize the novelty of the paper. 

N/A

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

 

This paper presents the work named Research on resource allocation strategy of indoor VLC/RF system integrating OFDMA technology where the authors propose a new resource allocation method and Orthogonal Frequency Division Multiple Access (OFDMA) technology is introduced. The obtained results are supported by simulation in order to achieve achieve the maximum transfer rate while the system remains stable.

In section I – Introduction, the authors present a brief framed scenario of 6G an the limitations radio spectrum resources. The VLC, RF and NLOS communications are framed with the presented work. The work is supported by the performance of VLC/RF systems based on Orthogonal Frequency Division Multiple Access (OFDMA) technology. The system consists of multiple VLC APs and one RF AP working together to serve multiple users. Using the OFDMA scheme, resources can be divided in the time domain and frequency domain at the same time,

In section II – System Model, the authors present the system model based., where in the downlink it is used VLC and RF. The uplink it provided by an RF link. It is presented the VLC and RF channel models. This last one it is based on OFDM scheme.

 

In section III – Optimize the problem description, the authors present the stochastic optimization formulas in order to achieve system stability. The final remark of this section is based on the maximization subcarriers allocation.

 

In section IV – Algorithm simulation results analysis. In this section the authors analyze the imulation results of the Lyapunov optimization algorithm and verify the performance of the proposed indoor VLC / RF system resource allocation scheme with OFDMA technology. The simulation parameters are described in Table 2 for indoor conditions. Several graphics are presented relating the number of user and Average Q for Lyapunov, MD-RA and BCSI-Ra methods.

 

In sectionV – Conclusions the authors draw their conclusions, however should consider propose future work.

 

Overall, the work is interesting with scientific soundness, namely by exploring the integration of VLC/RF with OFDMA technology. The authors should consider present a SoA secttion( or subsection) and compared the obtained results with other papers.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The author has cleared out the questions and answers well.

N/A