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Dynamic Power Optimization of Pilot and Data for Downlink OFDMA Systems
Yong Liu,Fei Liu,Guang Zhu,Xiaolei Wang,Yuechao Jiao 한국통신학회 2021 Journal of communications and networks Vol.23 No.4
In this paper, we investigate the power allocation prob lem in downlink orthogonal frequency-division multiple access(OFDMA) networks. Different from previous researches on powerallocation, we take into account various practical factors, such asthe stochastic traffic arrival, the time-varying channel, the queuestability requirements of all users, the channel estimation cost andthe corresponding effect of imperfect channel state information(CSI) on data transmission rate. The power allocation problemis formulated as maximizing the time-averaged data transmissionrate by optimizing pilot and data power allocation subject to thequeue stability and the maximum transmit power constraints. Thedata transmission rate is defined in terms of the pilot transmitpower, the data transmit power and the channel estimation er ror, which is non-concave. To solve the non-concave and stochas tic optimization problem, a dynamic pilot and data power alloca tion (DPDPA) algorithm is proposed with the aids of approximatetransformation, Lyapunov optimization and Lagrange dual formu lation. Moreover, we derive the bounds of performances, in termsof the time-averaged data transmission rate and queue length.
Yanying Hou,Lujie Liu,Xingxing Zhang,Yuechao Zhu,Yongjun Qiu,Liming Zhao 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-
Ion exchange resins are promising materials for separating chitooligosaccharides (COSs) with differentdegrees of polymerization (DP). The adsorbent functional groups significantly determine the interactionswith COSs and affect their adsorption and separation efficiency. This study investigated the adsorptionbehaviors of COSs on macroporous cation exchange resins with different functional groups to clarifythe functional group effect on the adsorption of COSs with different DP, which can also help to providea theoretical basis for the selection of separation medium and optimization of the separation technicsof COSs. The results showed that the adsorption of COSs on sulfonic-acid type resin DX-10 andcarboxylic-acid type resin DC-10 were favorable, and the adsorption isotherms were in accord withthe Sips model. Adsorption thermodynamics showed that temperature had opposite effects on the tworesins’ equilibrium adsorption capacity of COSs. The diffusion coefficient of COSs on DX-10 resin wasgreater, and the affinity gap between COSs on DX-10 resin was larger than that of DC-10 resin, whichis beneficial for improving the separation resolution of COSs. In contrast, the interaction energy betweenCOSs with high DP and DC-10 resin was weaker compared with DX-10, which made the elution of COSswith high DP easier.