[Paper Review] Performance Analysis of Integrated Power-Line/Visible-Light Communication Systems with AF Relaying

Waled Gheth, Khaled M. Rabie+3 more|arXiv (Cornell University)|Jul 26, 2018

Power Line Communications and Noise27 references4 citations

TL;DR

This paper proposes an amplify-and-forward (AF) relaying scheme in a hybrid power-line communication (PLC)/visible light communication (VLC) system to enhance indoor data transmission reliability and user mobility. By leveraging existing power lines as a PLC backbone and using an AF relay to forward signals from PLC to VLC links, the system achieves improved average capacity, especially with higher relay gain and shorter end-to-end distances, though the hybrid/PLC system offers superior performance at the cost of reduced mobility.

ABSTRACT

Reliable data transmissions and offering better mobility to the end user can be achieved by integrating different communication systems. In this paper, we investigate the performance of a cascaded indoor power line communication (PLC)/visible light communication (VLC) system with the presence of an amplify-and-forward (AF) relay. Using the pre-installed infrastructure of electricity wiring networks gives the advantage to use PLC as a backbone for VLCs. The performance of the proposed hybrid system is discussed in terms of the average capacity. A mathematical method is developed for this network to formulate the capacity by exploiting the statistical properties of both the PLC and VLC channels. The derived analytical expressions are validated by Monte Carlo simulations. The results showed that there is a considerable improvement in the performance of the hybrid system as the relay gain increases whereas it deteriorates with increasing the end-to-end distance. A comparison between the performance of a parallel hybrid/PLC and hybrid systems is also provided. It is found that the hybrid/PLC system outperforms the hybrid one. However, the user mobility offered by the latter system remains the main advantage over the former approach.

Motivation & Objective

• To investigate the performance of a cascaded PLC/VLC system with AF relaying for indoor communication.
• To develop an analytical framework for calculating the average capacity of the hybrid system using statistical channel models.
• To evaluate the impact of key system parameters such as relay gain, source-to-relay distance, and relay-to-user vertical distance on system performance.
• To compare the proposed hybrid system with a parallel hybrid/PLC system in terms of capacity and mobility trade-offs.

Proposed method

• Derives an analytical expression for the average capacity of the PLC/VLC system using statistical properties of PLC and VLC channels.
• Models the PLC link with frequency-selective fading and impulsive noise, and the VLC link with line-of-sight transmission and intensity modulation.
• Applies the amplify-and-forward (AF) relaying protocol where the relay amplifies and forwards the PLC signal to the VLC destination.
• Uses moment generating function (MGF) techniques and statistical approximations to derive closed-form capacity expressions.
• Validates analytical results through Monte Carlo simulations under realistic indoor system parameters.
• Compares the proposed hybrid system with a parallel hybrid/PLC system where the destination receives signals from both PLC and the hybrid path.

Experimental results

Research questions

• RQ1 How does relay gain affect the average capacity of the PLC/VLC AF relaying system?
• RQ2 What is the impact of increasing the source-to-relay distance on system performance?
• RQ3 How does the vertical distance between the relay and user plane influence the achievable capacity?
• RQ4 How does the performance of the proposed hybrid system compare with a parallel hybrid/PLC system in terms of capacity and reliability?
• RQ5 What trade-offs exist between system capacity and user mobility in the proposed hybrid system versus the hybrid/PLC system?

Key findings

• The average capacity increases significantly with higher relay gain, showing a 30% improvement when gain increases from 0 dB to 20 dB under the same conditions.
• Performance degrades with increasing vertical distance between the relay and user plane; capacity drops from 0.12 bits/s/Hz at 1.15 m to 0.04 bits/s/Hz at 3.15 m for a 7 W input power.
• Increasing the source-to-relay distance from 15 m to 45 m results in a noticeable capacity degradation, especially at low input power levels.
• The hybrid/PLC system outperforms the hybrid system in terms of average capacity, achieving up to 3.5 times higher capacity under identical relay gain and input power.
• Despite lower capacity, the hybrid system offers superior user mobility due to the use of optical wireless transmission, making it more suitable for mobile indoor applications.