[Paper Review] Geometric projection-based switching policy for multiple energy harvesting transmitters

Hongbin Chen, Fangfang Zhou+3 more|arXiv (Cornell University)|May 19, 2014

Energy Harvesting in Wireless Networks18 references3 citations

TL;DR

This paper proposes a geometric projection-based switching policy for multiple energy harvesting transmitters to minimize transmission completion time while reducing the number of transmitter switches. By projecting the transmission trajectory onto a time-data plane and selecting transmitters that align with the optimal path, the method achieves fewer switches than heuristic policies, with simulations showing 82 switches versus over 100 under alternatives.

ABSTRACT

Transmitter switching can provide resiliency and robustness to a communication system with multiple energy harvesting transmitters. However, excessive transmitter switching will bring heavy control overhead. In this paper, a geometric projection-based transmitter switching policy is proposed for a communication system with multiple energy harvesting transmitters and one receiver, which can reduce the number of switches. The results show that the proposed transmitter switching policy outperforms several heuristic ones.

Motivation & Objective

• To reduce control overhead and transmission interruption caused by excessive transmitter switching in multi-transmitter energy harvesting systems.
• To design a switching policy that minimizes the number of switches while ensuring timely data delivery.
• To leverage geometric projection in the time-data plane to determine optimal transmitter transitions.
• To outperform heuristic policies such as energy-max, rate-max, bits-max, and time-max switching strategies.
• To provide a centralized, deterministic switching strategy for multiple energy harvesting transmitters with known channel path losses.

Proposed method

• The system models multiple energy harvesting transmitters and one receiver, with stochastic energy arrivals and fixed channel path losses.
• Transmission completion time is computed deterministically based on total bits and optimal power allocation across transmitters.
• A time-data plane is constructed with transmission start and end points, and the optimal switching path is modeled as a straight line between them.
• Geometric projection is used to identify the transmitter whose current energy and rate profile best aligns with the ideal path, minimizing deviation.
• The switching decision at each epoch is based on the projection of the current state onto the optimal line, ensuring minimal switching while maintaining performance.
• The method assumes known channel state information and fixed path loss, enabling centralized decision-making.

Experimental results

Research questions

• RQ1 How can transmitter switching be minimized in a multi-energy-harvesting transmitter system without compromising transmission completion time?
• RQ2 What geometric criterion can be used to determine the optimal transmitter at each switching instant?
• RQ3 How does a geometric projection-based policy compare to heuristic policies like energy-max, rate-max, bits-max, and time-max in terms of switch count?
• RQ4 Can a deterministic, centralized switching policy achieve lower switching overhead than heuristic alternatives?
• RQ5 What is the impact of channel path loss and energy arrival statistics on the effectiveness of the proposed switching policy?

Key findings

• The proposed geometric projection-based switching policy reduces the number of switches to 82 for a 6000-bit transmission, outperforming all heuristic policies.
• The heuristic policies—energy-max, rate-max, bits-max, and time-max—result in over 100 switches, indicating suboptimal performance.
• The average number of switches across 500 and 1000 independent simulations confirms that the proposed method consistently achieves the lowest switch count.
• The method achieves optimal transmission completion time with minimal switching by aligning transmitter transitions with the straight-line path in the time-data plane.
• The geometric projection criterion effectively balances energy availability, transmission rate, and switch minimization.
• The policy is effective under known channel path losses and deterministic transmission time, suggesting strong potential for practical deployment.