Low-Latency Communications over Zero-Battery Energy Harvesting Channels

We study the fundamental performance limits of energy harvesting channels with short-length channel codes that expend less processing energy and facilitate low-latency communications. In particular, we examine the zero-battery case, i.e, energy harvesting transmitters with no energy storage such as passive RFID tags, in which energy must be spent as it arrives or is lost. To analyze practical finite-length channel codes, we develop a second-order approximation to the communication rate for such channels with energy information causally known at the transmitter. We present two binary examples for which we explicitly calculate the channel capacity and channel dispersion and interestingly observe that a slight increase in the energy arrival probability can significantly boost the achievable rate, and further that the rate loss due to energy intermittency is more pronounced for channels with lower noise levels.