Ren, QuanjiaQuanjiaRenChan,Tse-TinChanPan, HaoyuanHaoyuanPanDr. HO Kin-Hon, RoyRoyDr. HO Kin-HonDu, ZhihuaZhihuaDu2023-09-152023-09-152022IEEE Wireless Communications Letters, 2022, Vol. 11(10), pp. 2061-2065.2162-23372162-2345http://hdl.handle.net/20.500.11861/7975This letter investigates both information freshness and energy harvesting (EH) in downlink information update systems. Information freshness is characterized by age of information (AoI). We consider a scenario in which a large update message is packetized into K small packets and encoded by random linear network coding (RLNC). A base station continuously broadcasts the RLNC-encoded packets to multiple users until all the users have received the message. When a user successfully receives the update message while at least one other user has not received it yet, the user harvests energy from the received signals. A key challenge is to decide the value of K in the message packetization in order to achieve low AoI and high EH simultaneously. To this end, we conduct a theoretical analysis of the tradeoff between the AoI and EH performance under different values of K . In particular, the packet error rates of short packets in the message packetization are estimated by the short packet theory, and the closed-form AoI and EH formulas are derived. Our numerical results reveal that there exists a K (neither too small nor too large) that can achieve both low AoI and high EH.enEnergy HarvestingInformation FreshnessTheoretical AnalysisAge of InformationBase StationUpdated InformationRandom NetworksBit Error RateRandom CodeLinear CodeSmall PacketsNetwork CodingDecodingTheoretical ResultsInternet of ThingsAdditive NoiseTime SlotRadio WavesInternet of Things DevicesTransmission CycleFinite FieldPeer Reviewed Journal Article10.1109/LWC.2022.3193186