On the Energy Efficiency of LT Codes in Proactive Wireless Sensor Networks

TL;DR

This paper analyzes the energy efficiency of LT codes combined with NC-MFSK in proactive wireless sensor networks over Rayleigh fading channels, demonstrating LT codes' advantages in energy savings at larger distances.

Contribution

It provides the first detailed analysis of LT codes with green modulation in proactive WSNs, highlighting their energy efficiency and adaptability over traditional coding schemes.

Findings

LT coded NC-MFSK is most energy-efficient beyond a certain distance threshold.

Uncoded NC-MFSK outperforms coded schemes at shorter distances, but with negligible energy difference.

LT codes' flexibility allows adaptation to channel conditions, benefiting low-power sensor networks.

Abstract

This paper presents the first in-depth analysis on the energy efficiency of LT codes with Non Coherent M-ary Frequency Shift Keying (NC-MFSK), known as green modulation [1], in a proactive Wireless Sensor Network (WSN) over Rayleigh flat-fading channels with path-loss. We describe the proactive system model according to a pre-determined time-based process utilized in practical sensor nodes. The present analysis is based on realistic parameters including the effect of channel bandwidth used in the IEEE 802.15.4 standard, and the active mode duration. A comprehensive analysis, supported by some simulation studies on the probability mass function of the LT code rate and coding gain, shows that among uncoded NC-MFSK and various classical channel coding schemes, the optimized LT coded NC-MFSK is the most energy-efficient scheme for distance $d$ greater than the pre-determined threshold level $d_T$, where the optimization is performed over coding and modulation parameters. In addition, although uncoded NC-MFSK outperforms coded schemes for $d < d_T$, the energy gap between LT coded and uncoded NC-MFSK is negligible for $d < d_T$ compared to the other coded schemes. These results come from the flexibility of the LT code to adjust its rate to suit instantaneous channel conditions, and suggest that LT codes are beneficial in practical low-power WSNs with dynamic position sensor nodes.