Asymptotically Optimal Power Allocation for Energy Harvesting Communication Networks

TL;DR

This paper derives a simple, asymptotically optimal online power allocation strategy for energy harvesting communication networks, which aligns with the optimal solution of an equivalent non-EH network as the number of slots and battery capacity grow large.

Contribution

It introduces a novel asymptotic power allocation method for EH networks that simplifies implementation and matches the performance of an idealized non-EH network under large-scale conditions.

Findings

Optimal power allocation converges to that of a non-EH network with average power constraints.

Maximum average performance of EH networks approaches that of the equivalent non-EH network.

The solution is effective for large but finite time slots and battery capacities.

Abstract

For a general energy harvesting (EH) communication network, i.e., a network where the nodes generate their transmit power through EH, we derive the asymptotically optimal online power allocation solution which optimizes a general utility function when the number of transmit time slots, $N$, and the battery capacities of the EH nodes, $B_{\rm max}$, satisfy $N\to\infty$ and $B_{\rm max}\to\infty$. The considered family of utility functions is general enough to include the most important performance measures in communication theory such as the average data rate, outage probability, average bit error probability, and average signal-to-noise ratio. The proposed power allocation solution is very simple. Namely, the asymptotically optimal power allocation for the EH network is identical to the optimal power allocation for an equivalent non-EH network whose nodes have infinite energy available but their average transmit power is constrained to be equal to the average harvested power and/or the maximum average transmit power of the corresponding nodes in the EH network. Moreover, the maximum average performance of a general EH network converges to the maximum average performance of the corresponding equivalent non-EH network, when $N\to\infty$ and $B_{\rm max}\to\infty$. Although the proposed solution is asymptotic in nature, it is applicable to EH systems transmitting in a large but finite number of time slots and having a battery capacity much larger than the average harvested power and/or the maximum average transmit power.