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The resource allocation in cognitive radio networks is one of the key issues to improve the spectrum efficiency. In most previous work, only one type of the secondary user (SU) network architecture is considered, i.e., it is always assumed that all SUs are centralized, or all are distributed. However, in heterogeneous cognitive radio networks, which takes both the centralized and distributed architectures...
In cognitive radio (CR) networks, cooperative relaying is emerging as a key technology to improve the performance of secondary users (SUs), while ensuring the quality of service of primary transmissions. Most previous work considers maximizing physical layer throughput as a design criterion. However, the end-to-end Transmission Control Protocol (TCP) performance perceived by SUs is largely ignored...
In this paper, we propose a distributed joint relay selection and power allocation scheme in wireless multi-hop cooperative networks, taking both instantaneous channel state information (CSI) and relay nodes' residual energy into consideration. Specifically, we formulate the cooperative relaying network as a restless bandit system, which has been successfully applied in stochastic control and operations...
This paper identifies post etch killer defects, e.g., core bridging, small particle and tiny bridging, and investigates the possible solutions in a SADP module. Among the killer defect adders, core bridging and small particle are commonly observed after the oxide core removal by BOE. Core bridging adder is a carbon-containing polymeric by-product during nitride spacer open; by introducing additional...
This paper describes the advanced control technology of critical dimension uniformity (CDU) by flash gate stack etch process. We have investigated the effective way of utilizing Tri-layer approach, which not only reduces the influence of topology step-height but also improves the range of ECD within die from 17.6nm to 4.9nm. Moreover, the influence of Etcher design on ECD variation becomes larger...
The mathematical model of temperature field and fluid field in tundish was established through mathematical simulation of computer. The results showed that the two high temperature regions were formed corresponding the two recirculation regions in the tundish; In the normal casting proceeds, the insert position of temperature measurement sensor of tundish was no limitation, the superheat difference...
Layered broadcast/multicast mechanism is a promising method to provide energy efficient and reliable services for users with diverse fading channels in Green 4G wireless networks, however, there is a great challenge to determine the optimal modulation parameters in applications due to the varying wireless environment and the technique characteristics. In this work, an Energy efficient Layered Broadcast/Multicast...
In future wireless communication networks, layered modulation is a promising technique to provide reliable and efficient broadcast service for users with diversified wireless fading channel. However, there is a great challenge to effectively determine the modulation parameters in applications. To solve this problem, a Modulation Solution Selection (LMSS) algorithm is proposed in this work. Firstly,...
In this paper, we propose a distributed best-relay node selection scheme to maximize the achievable data rate for cooperative communications over underlay-paradigm based CR networks, and meanwhile guarantee that the primary link is provided with a minimum-rate for a certain percentage of time. Specifically, we formulate the CR relay network as a restless bandit system, where the finite-state Markov...
This paper considers multi-hop cellular networks in which nodes use accumulation for cooperative broadcasting in order to save total energy with low delay. Our purpose is to build up Green Cellular Networks (GCN) which represent the trend of Next-Generation Networking (NGN) and cater for people's demand for health and energy savings. Therefore, we assume a radiation and harmful region and show that...
Spectrum sensing is one of the key issues for spectrum sharing in cognitive radio networks to deal with the more and more serious problem on exhaustive spectrum resource. In this paper, we study the problem of wideband spectrum sensing in cognitive radio networks with multiple primary networks. By dividing the total wideband spectrum into many groups with relatively small number of narrowbands, a...
Most previous work in CR relay networks concentrates on maximizing physical layer QoS (e.g., capacity, spectral efficiency and achievable data rate) as relay selection criteria. However, the energy state of relay nodes is largely ignored, which has significant effects on the network lifetime. This paper proposes a distributed relay selection scheme for cooperative transmissions over underlay CR networks,...
Large-scale multi-AP WMAPNs with a high density of users and access points (APs) have emerged widely in various hotspots, where inter-cell interference is detrimental to the performance of WLANs. In order to mitigate the interference, channel assignment scheme has been a major research topic in recent years. In this paper, based on Bianchi's throughput performance evaluation, we model a channel assignment...
In cognitive radio (CR) networks, cooperative relaying is a promising technology to improve the performance of secondary users (SUs), while ensuring the quality of service (QoS) of primary transmissions. Most previous work in CR relay networks concentrates on maximizing physical layer QoS, e.g., system capacity, as the design criteria. However, the application layer QoS perceived by SUs, such as multimedia...
In common models of cognitive radio networks (CRNs), priority in spectrum access of primary users (PUs) must be guaranteed, but the quality of service (QoS) for secondary users (SUs) is mostly ignored. Subject to meeting PUs' blocking probability objective, this paper proposes a channel reservation scheme to enhance QoS for SUs. The proposed scheme employs a centralized control manager (CCM) to coordinate...
Emerging 4G standards, such as WiMAX, LTE, and TD-SCDMA, have adopted the proven technique of Adaptive Modulation and Coding (AMC) to dynamically react to channel fluctuations while maintaining bit- error rate targets of the transmission. To mitigate the vicious effects due to stale channel state indication (CSI) problem, this paper introduces a novel framework by incorporating AMC with layered transmission...
Resource allocation problem in cognitive radio networks (CRN) is one of the key issues to improve the efficiency of spectrum utilization. Most of previous work on resource allocation mainly concentrates on the secondary users (SUs) with only one type of service requirement, without considering the scenario with heterogenous services requirement. In this paper, we study the dynamic channel and power...
Dynamic spectrum access is one of the most important premises of spectrum reuse based on cognitive radio technologies, which are considered to be the best way to alleviate the controversy on spectrum scarcity and low efficiency. However, most of previous work focuses on the increasing of system throughput, ignoring the QoS requirement of secondary users. In this paper, dynamic spectrum access with...
In an underlay paradigm based cognitive radio (CR) network, due to the constraint of interference threshold, secondary users always experience low system capacity. In this paper, we propose a distributed scheme to improve the capacity of underlay based CR network where the communication between secondary users is assisted by a relay node. The relay node is characterized by channel states of all related...
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