We consider an energy-harvesting cognitive radio system where the secondary transmitter harvests energy. This system operates under an energy causality constraint mandating that the average energy ...consumption must not exceed the average harvested energy, and a collision constraint mandating the protection of the primary system. The purpose of this paper is to identify the optimal pairing of the sensing duration and the energy detector's sensing threshold in order to maximize the average throughput of the secondary network. Since the sensing duration and sensing threshold are intertwined with the energy causality constraint, they need to be redesigned with the purpose of conserving energy in mind. Hence, the sensing duration must be shorter while still satisfying the collision constraint. The numerical results show that the optimal sensing duration is determined based on which constraint, collision or energy causality, needs to have priority. In addition, the simulation results show a pairing of the optimal sensing duration and sensing threshold provided by the coordination between the two constraints, which gives insight into how to design them.
Synchronization Sequence Design for FBMC/OQAM Systems Chung, Wonsuk; Kim, Chanhong; Choi, Sooyong ...
IEEE transactions on wireless communications,
2016-Oct., 2016-10-00, 20161001, Letnik:
15, Številka:
10
Journal Article
Recenzirano
In this paper, we propose a new sequence generation methodology to make a constant amplitude zero autocorrelation (CAZAC) preamble available in offset Quadrature Amplitude Modulation-based filter ...bank multicarrier (FBMC) synchronization. The role of the new sequence is to compensate the filtering and symbol overlap of the FBMC structure so as to finally be able to make a CAZAC preamble in time domain. To derive the new sequence, we formulate a symbol overlap model that shows the relation between the new sequence and a CAZAC preamble. On the other hand, the offset modulation format is a constraint that needs to be considered in the design of the new sequence. By using a property of this offset modulation constraint, we derive a closed-form expression of the new sequence from the symbol overlap model. In addition, we extend an advanced model to create a pseudo-CAZAC preamble that is not data-dependent, thus enabling convenience of implementation. Simulation results show the superiority of the proposed model with respect to synchronization accuracy, out-of-band radiation, and peak to average power ratio. Moreover, we verify that the proposed model is well-suited for use in the cellular environment through complexity and resource efficiency comparisons.
In this paper, we consider a new interference problem caused by idle small cells, which have no associated user equipment in ultra-dense small cell long-term evolution (LTE) networks. Specifically, ...we investigate the effect of idle small cells on the signal to interference and noise ratio (SINR) of the cell-specific reference signal (CRS) and the data signals. We confirm that CRS interference from idle small cells produces uneven interference pattern across CRS and data signals and eventually causes an SINR mismatch between CRS and data signals as well as between data signals with and without CRS symbols. In addition, these phenomena become severe with cell densification. In order to solve this mismatch problem, we propose a simple link adaptation framework, which utilizes clustered CRS assignment and hybrid SINR measurement. The numerical results show that the proposed method improves the average sum throughput compared with the conventional approaches. Overall, this paper sheds new light on investigating and coping with the interference problem coming from idle small cells in future ultra-dense small cell LTE networks.
This work analyzes the impacts of deploying a Power-to-Gas technology in the power generation sector in South Korea by 2050. The Power-to-Gas technology of interest is the low-temperature ...co-electrolysis of CO2 and H2O, which is an emerging technology for electrochemically converting them to syngas. Particularly, excess electricity available from intermittent renewable energy resources is intended to be the main energy source for the co-electrolysis. A conceptual design of the co-electrolysis process is carried out to calculate its performance data including mass balances, energy demand, and capital investment. Based on them, a temporal energy system model is developed using the TIMES (The Integrated MARKAL-EFOM System) model generator. The conclusion is that deploying the co-electrolysis process in the Korean power generation sector can reduce greenhouse gas emissions and also save the overall system cost when the syngas production cost is lower than the purchasing cost of liquid natural gas. The beneficial impacts are limited by the amount of available excess electricity and the co-firing ratio limit in the gas-fired power plants. Finally, the overpotential and current density, as uncertain parameters of the co-electrolysis process, are found to affect the syngas production cost most strongly.
In this paper, we propose a uplink (UL) non-orthogonal multiple access (NOMA) systems equipped with multiple antennas to enhance the sum capacity of UL. In the proposed UL NOMA system, a base station ...(BS) with N antennas can support 2N users by sharing the space resource. However, sharing the space resource leads to interference between users. Therefore, to mitigate the interference and improve the sum capacity, we additionally propose a set selection algorithm and power control scheme. The set selection algorithm, which selects 2N users based on orthogonality and gain-difference between their channels, reduces the interference between users. Furthermore, the power control scheme can maximize the sum capacity with ensuring minimum target rate. Numerical results show that the proposed system improves the sum capacity over that of the conventional orthogonal multiple access (OMA) system.
When can you trust an expert to provide honest advice? We develop and test a recommendation game where an expert helps a decision maker choose among two actions that benefit the expert and an outside ...option that does not. For instance, a salesperson recommends one of two products to a customer who may instead purchase nothing. Subject behavior in a laboratory experiment is largely consistent with predictions from the cheap talk literature. For sufficient symmetry in payoffs, recommendations are persuasive in that they raise the chance that the decision maker takes one of the actions rather than the outside option. If the expert is known to have a payoff bias toward an action, such as a salesperson receiving a higher commission on one product, the decision maker partially
discounts a recommendation for it and is more likely to take the outside option. If the bias is uncertain, then biased experts lie even more, whereas unbiased experts follow a
political correctness strategy of pushing the opposite action so as to be more persuasive. Even when the expert is known to be unbiased, if the decision maker already favors an action the expert
panders toward it, and the decision maker partially discounts the recommendation. The comparative static predictions hold with any degree of lying aversion up to pure cheap talk, and most subjects exhibit some limited lying aversion. The results highlight that the transparency of expert incentives can improve communication, but need not ensure unbiased advice.
Carbon capture followed by utilization or storage enables carbon-intensive sectors to abate their CO2 emissions. However, complexity and nonlinearity of the capture processes hinder the incorporation ...of their first-principles models into analyses and optimizations of overall carbon management strategies. Accordingly, it is desirable to have a systematic method to develop a computationally less demanding surrogate model, which can replace the rigorous CO2 capture process model, for use in a high-level decision-making environment. For such purposes, the surrogate model should be able to provide multiple information needed to connect to subsequent processing steps under varying source stream conditions. This research addresses the development of surrogate models for CO2 capture processes that enjoy significantly lowered complexity while preserving the key information. A surrogate model can be constructed by fitting the input–output data generated by process simulation and optimization with the rigorous model. Following the proposed method, surrogate models for the amine-based CO2 capture processes with two representative types of amines, monoethanolamine (MEA) and piperazine (PZ), are constructed and validated. The constructed surrogate models predict the specific steam consumption rate and total equipment purchase cost based on the input information of desired capture rate and CO2 source stream condition. The predicted information is shown to agree well with the simulation result of the rigorous first-principles model. This surrogate modeling approach can be applied to compare different capture technologies in the context of analyzing and synthesizing a larger CCUS processing network.
This paper proposes an optimal transmit power control policy designed to maximize the average throughput of an energy-harvesting secondary network. As the transmit power increases, the ...energy-harvesting secondary network can enhance its throughput during a slot, but the probability of being active decreases due to the energy shortage. The probability of colliding with the primary signal also decreases as the transmit power increases. The optimal transmit power can be obtained by analyzing the effect of the transmit power on performance, especially as a function of statistics of harvested energy.
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