Timely Status Updating Through Intermittent Sensing and Transmission

Abstract

Consider an energy harvesting node where generation of a status update message takes non-negligible time due to sensing, computing and analytics operations performed before making update transmissions. The node has to harmonize its (re)transmission strategy with the sensing/computing. We call this general set of problems intermittent status updating. In this paper, we consider intermittent status updating through non-preemptive sensing/computing (S/C) and transmission (Tx) operations, each costing a single energy recharge of the node, through an erasure channel with (a) perfect channel feedback and (b) no channel feedback. The S/C time for each update is independent with a general distribution. The Tx queue has a single data buffer to save the latest packet generated after the S/C operation and a single transmitter where transmission time is deterministic. Once energy is harvested, the node has to decide whether to activate S/C to generate a new update or to (re)send the existing update (if any) to the receiver. We prove that when feedback is available average peak age of information (AoI) at the receiver is minimized by a thresholdbased policy that allows only young packets to be (re)sent or else generates a new update. We additionally propose window based and probabilistic retransmission schemes for both cases (a) and (b) and obtain closed form average peak AoI expressions. Our numerical results show average peak AoI performance comparisons and improvements.

Timely Updating with Intermittent Energy and Data for Multiple Sources over Erasure Channels

“…For the second moment, the computations lead to a more involved expression, shown at the top of the next page in (18). Finally, using ( 16), (17), and ( 18), together with ( 7) and ( 8), one can substitute in (10) and evaluate the long-term average AoI achieved with a γ-threshold policy. We define this as AoI q (γ) to emphasize the dependency on q and γ.…”

Data Freshness in Mixed-Memory Intermittently-Powered Systems

“…Packet Generation/Sensing. Packets containing data from an on-board sensor are produced as required in a generate-atwill type policy-where sensing only occurs when processing of the preceding packet is complete-as considered in [17]. We assume that sensing is instantaneous and that this data is then immediately processed, from which a packet is created.…”

“…Our work builds on [17] by accounting for the mixedmemory nature of many battery-free devices and the checkpointing schemes used to move data between memory types. To the best of our knowledge, this is the first evaluation and comparison of AoI in IPDs with mixed-memory architecture.…”

Decode-and-Forward Short-Packet Relaying in the Internet of Things: Timely Status Updates

“…The average AoI and average peak AoI of edge computing systems were analysed in [13], where sensor nodes firstly process the acquired information and then transmit the processed results to an edge receiver. The average AoI in energy harvesting wireless sensor networks was investigated in [14]- [16]. Under the constraints of average AoI and power consumption, the long-term average throughput was analysed and maximised in [17] given both perfect channel state information at the transmitter (CSIT) and statistical CSIT.…”