In order to support massive Machine Type Communication(mMTC) applications in future Fifth Generation(5G) systems,a key technical challenge is to design a highly effective multiple access protocol for massive connectio...In order to support massive Machine Type Communication(mMTC) applications in future Fifth Generation(5G) systems,a key technical challenge is to design a highly effective multiple access protocol for massive connection requests and huge traffic load from all kinds of smart devices,e.g.bike,watch,phone,ring,glasses,shoes,etc..To solve this hard problem in distributed scenarios with massive competing devices,this paper proposes and evaluates a Neighbor-Aware Multiple Access(NAMA) protocol,which is scalable and adaptive to different connectivity size and traffic load.By exploiting acknowledgement signals broadcasted from the neighboring devices with successful packet transmissions,NAMA is able to turn itself from a contention-based random access protocol to become a contention-free deterministic access protocol with particular transmission schedules for all neighboring devices after a short transition period.The performance of NAMA is fully evaluated from random state to deterministic state through extensive computer simulations under different network sizes and Contention Window(CW)settings.Compared with traditional IEEE802.11 Distributed Coordination Function(DCF),for a crowded network with 50 devices,NAMA can greatly improve system throughput and energy efficiency by more than 110%and210%,respectively,while reducing average access delay by 53%in the deterministic state.展开更多
In this paper, the bipolar resistive switching characteristic is reported in Ti/ZrO2/Pt resistive switching memory de- vices. The dominant mechanism of resistive switching is the formation and rupture of the conductiv...In this paper, the bipolar resistive switching characteristic is reported in Ti/ZrO2/Pt resistive switching memory de- vices. The dominant mechanism of resistive switching is the formation and rupture of the conductive filament composed of oxygen vacancies. The conduction mechanisms for low and high resistance states are dominated by the ohmic conduc- tion and the trap-controlled space charge limited current （SCLC） mechanism, respectively. The effect of a set compliance current on the switching parameters is also studied： the low resistance and reset current are linearly dependent on the set compliance current in the log-log scale coordinate; and the set and reset voltage increase slightly with the increase of the set compliance current. A series circuit model is proposed to explain the effect of the set compliance current on the resistive switching behaviors.展开更多
Resistive random access memory (RRAM) has received significant research interest because of its promising potential in terms of down-scaling,high density,high speed and low power. However,its endurance,retention and u...Resistive random access memory (RRAM) has received significant research interest because of its promising potential in terms of down-scaling,high density,high speed and low power. However,its endurance,retention and uniformity are still imperfect. In this article,the physical mechanisms of filament-type RRAM and the approaches for improving the switching performance,including doping,process optimization and interface engineering,are introduced.展开更多
基金funded by the National Natural Science Foundation of China (Grant No.61231009)the National HighTech R&D Program of China(863)(Grant No.2014AA01A701)+5 种基金the National Science and Technology Major Project(Grant No. 2015ZX03001033-003)Ministry of Science and Technology International Cooperation Project(Grant No.2014DFE10160)the Science and Technology Commission of Shanghai Municipality(Grant No.14ZR1439600)the EU H2020 5G Wireless project(Grant No.641985)the EU FP7 QUICK project(Grant No. PIRSES-GA-2013-612652)the EPSRC TOUCAN project(Grant No.EP/L020009/1)
文摘In order to support massive Machine Type Communication(mMTC) applications in future Fifth Generation(5G) systems,a key technical challenge is to design a highly effective multiple access protocol for massive connection requests and huge traffic load from all kinds of smart devices,e.g.bike,watch,phone,ring,glasses,shoes,etc..To solve this hard problem in distributed scenarios with massive competing devices,this paper proposes and evaluates a Neighbor-Aware Multiple Access(NAMA) protocol,which is scalable and adaptive to different connectivity size and traffic load.By exploiting acknowledgement signals broadcasted from the neighboring devices with successful packet transmissions,NAMA is able to turn itself from a contention-based random access protocol to become a contention-free deterministic access protocol with particular transmission schedules for all neighboring devices after a short transition period.The performance of NAMA is fully evaluated from random state to deterministic state through extensive computer simulations under different network sizes and Contention Window(CW)settings.Compared with traditional IEEE802.11 Distributed Coordination Function(DCF),for a crowded network with 50 devices,NAMA can greatly improve system throughput and energy efficiency by more than 110%and210%,respectively,while reducing average access delay by 53%in the deterministic state.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00606)the National Natural Science Foundation of China(Grant Nos.61106106,11304237,61376099,and 11235008)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant Nos.20130203130002 and 20110203110012)
文摘In this paper, the bipolar resistive switching characteristic is reported in Ti/ZrO2/Pt resistive switching memory de- vices. The dominant mechanism of resistive switching is the formation and rupture of the conductive filament composed of oxygen vacancies. The conduction mechanisms for low and high resistance states are dominated by the ohmic conduc- tion and the trap-controlled space charge limited current （SCLC） mechanism, respectively. The effect of a set compliance current on the switching parameters is also studied： the low resistance and reset current are linearly dependent on the set compliance current in the log-log scale coordinate; and the set and reset voltage increase slightly with the increase of the set compliance current. A series circuit model is proposed to explain the effect of the set compliance current on the resistive switching behaviors.
基金supported by the National Basic Research Program of China (2010CB934200 and 2008CB925002)the National Natural Science Foundation of China (60825403 and 50972160)the National High-Tech Research & Development Program of China (2008AA031403 and 2009AA03Z306)
文摘Resistive random access memory (RRAM) has received significant research interest because of its promising potential in terms of down-scaling,high density,high speed and low power. However,its endurance,retention and uniformity are still imperfect. In this article,the physical mechanisms of filament-type RRAM and the approaches for improving the switching performance,including doping,process optimization and interface engineering,are introduced.
