Coded Status Updates in an Energy Harvesting Erasure Channel

TL;DR

This paper investigates how energy harvesting and erasure channel coding strategies affect the freshness of information, proposing schemes that optimize age of information using MDS and rateless codes with save-and-transmit policies.

Contribution

It introduces a comprehensive analysis of coding and transmission schemes for energy harvesting erasure channels, comparing best-effort and save-and-transmit policies with MDS and rateless codes.

Findings

Rateless coding with save-and-transmit achieves the lowest average AoI.

MDS coding with save-and-transmit outperforms best-effort schemes at low recharge rates.

Energy-aware coding strategies significantly improve information freshness.

Abstract

We consider an energy harvesting transmitter sending status updates to a receiver over an erasure channel, where each status update is of length $k$ symbols. The energy arrivals and the channel erasures are independent and identically distributed (i.i.d.) and Bernoulli distributed in each slot. In order to combat the effects of the erasures in the channel and the uncertainty in the energy arrivals, we use channel coding to encode the status update symbols. We consider two types of channel coding: maximum distance separable (MDS) codes and rateless erasure codes. For each of these models, we study two achievable schemes: best-effort and save-and-transmit. In the best-effort scheme, the transmitter starts transmission right away, and sends a symbol if it has energy. In the save-and-transmit scheme, the transmitter remains silent in the beginning in order to save some energy to minimize energy outages in future slots. We analyze the average age of information (AoI) under each of these policies. We show through numerical results that as the average recharge rate decreases, MDS coding with save-and-transmit outperforms all best-effort schemes. We show that rateless coding with save-and-transmit outperforms all the other schemes.