Tesi sul tema "Random access efficiency"
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Filho, José Carlos Marinello. "Energy and spectral efficiency optimization in multiuser massive MIMO Comunications systems". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-03102018-142636/.
Testo completoSistemas de comunicação de múltiplas antenas (multiple-input multiple-output - MIMO) têm se destacado como a principal tecnologia para a camada física dos padrões de comunicação da próxima geração, como o 5G. Enquanto a comunicação convencional entre a estação base (base station - BS) e seus usuários atendidos é realizada em recursos ortogonais de tempo-frequência, a grande capacidade de redução da interferência interusuários possibilitada pelo grande número de antenas da BS habilita a BS a se comunicar com diversos usuários no mesmo recurso tempo-frequência. Este melhor uso do escasso espectro disponível eleva a eficiência espectral a níveis muito apreciáveis, e tem um efeito similar na eficiência energética, pois a potência de transmissão não é aumentada. Por outro lado, se o objetivo é fornecer um desempenho desejado para os usuários, a potência de transmissão necessária em ambos os enlaces direto e reverso pode ser feita inversamente proporcional ao número de antenas na BS. Nesta Tese de Doutorado, diversos aspectos importantes de sistemas MIMO massivo são sistematicamente investigados com o objetivo de melhorar suas eficiências energética e espectral. Pode-se enumerar as principais contribuições alcançadas como se segue. Considerando uma rede celular MIMO massivo, propõe-se uma política de atribuição de sequências de treinamento aos usuários otimizada, a qual é depois combinada com apropriados algoritmos de controle de potência. Também investiga-se a adoção neste cenário de formas de onda alternativas, tal como a transmissão de portadora única, visando superar as deficiências da convencional multiplexagem por divisão de portadoras ortogonais (orthogonal frequency-division multiplexing - OFDM). As principais contribuições obtidas neste tema são derivar expressões de desempenho analíticas para um equalizador de portadora única no domínio do tempo que aproveita o grande número de antenas na BS, e avaliar e comparar a eficiência energética total de sistemas MIMO massivo OFDM versus portadora única. Finalmente, considerando redes MIMO massivo sobrecarregadas, compostas por usuários humanos bem como dispositivos de comunicação do tipo máquina, propõe-se um protocolo de acesso aleatório melhorado visando diminuir o número médio de tentativas de acesso para os usuários e diminuir a probabilidade de falhas de tentativa de acesso.
Leung, Raymond Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Scalable video compression with optimized visual performance and random accessibility". Awarded by:University of New South Wales. Electrical Engineering and Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/24192.
Testo completoHan, Chong. "Analysis and design of efficient medium access control schemes for vehicular ad-hoc networks". Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576087.
Testo completoRasquinha, Mitchelle. "An energy efficient cache design using spin torque transfer (STT) RAM". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42715.
Testo completoChen, Zhi. "Power-Efficient and Low-Latency Memory Access for CMP Systems with Heterogeneous Scratchpad On-Chip Memory". UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/25.
Testo completoForsberg, Daniel. "An efficient wavelet representation for large medical image stacks". Thesis, Linköping University, Department of Electrical Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8394.
Testo completoLike the rest of the society modern health care has to deal with the ever increasing information flow. Imaging modalities such as CT, MRI, US, SPECT and PET just keep producing more and more data. Especially CT and MRI and their 3D image stacks cause problems in terms of how to effectively handle these data sets. Usually a PACS is used to manage the information flow. Since a PACS often is implemented with a server-client setup, the management of these large data sets requires an efficient representation of medical image stacks that minimizes the amount of data transmitted between server and client and that efficiently supports the workflow of a practitioner.
In this thesis an efficient wavelet representation for large medical image stacks is proposed for the use in a PACS. The representation supports features such as lossless viewing, random access, ROI-viewing, scalable resolution, thick slab viewing and progressive transmission. All of these features are believed to be essential to form an efficient tool for navigation and reconstruction of an image stack.
The proposed wavelet representation has also been implemented and found to be better in terms of memory allocation and amount of data transmitted between server and client when compared to prior solutions. Performance tests of the implementation has also shown the proposed wavelet representation to have a good computational performance.
Liu, Jheng-Sin. "Advanced Energy-Efficient Devices for Ultra-Low Voltage System: Materials-to-Circuits". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/81858.
Testo completoPh. D.
Liang, Weifa, e wliang@cs anu edu au. "Designing Efficient Parallel Algorithms for Graph Problems". The Australian National University. Department of Computer Science, 1997. http://thesis.anu.edu.au./public/adt-ANU20010829.114536.
Testo completoChatterjee, Subho. "A design methodology for robust, energy-efficient, application-aware memory systems". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50146.
Testo completoLeyva, Mayorga Israel. "On reliable and energy efficient massive wireless communications: the road to 5G". Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/115484.
Testo completoLa cinquena generació de xarxes mòbils (5G) es troba molt a la vora. S'espera que proveïsca de beneficis extraordinaris a la població i que resolga la majoria dels problemes de les xarxes 4G actuals. L'èxit de 5G, per a la qual ja ha sigut completada la primera fase del qual d'estandardització, depén de tres pilars: comunicacions tipus-màquina massives, banda ampla mòbil millorada, i comunicacions ultra fiables i de baixa latència (mMTC, eMBB i URLLC, respectivament, per les seues sigles en anglés). En aquesta tesi ens enfoquem en el primer pilar de 5G, mMTC, però també proveïm una solució per a aconseguir eMBB en escenaris de distribució massiva de continguts. Específicament, les principals contribucions són en les àrees de: 1) suport eficient de mMTC en xarxes cel·lulars; 2) accés aleatori per al report d'esdeveniments en xarxes sense fils de sensors (WSNs); i 3) cooperació per a la distribució massiva de continguts en xarxes cel·lulars. En l'apartat de mMTC en xarxes cel·lulars, aquesta tesi realitza una anàlisi profunda de l'acompliment del procediment d'accés aleatori, que és la forma mitjançant la qual els dispositius mòbils accedeixen a la xarxa. Aquestes anàlisis van ser inicialment dutes per mitjà de simulacions i, posteriorment, per mitjà d'un model analític. Els models van ser desenvolupats específicament per a aquest propòsit i inclouen un dels esquemes de control d'accés més prometedors: el access class barring (ACB). El nostre model és un dels més precisos que es poden trobar i l'únic que incorpora l'esquema d'ACB. Els resultats obtinguts per mitjà d'aquest model i per simulació són clars: els accessos altament sincronitzats que ocorren en aplicacions de mMTC poden causar congestió severa en el canal d'accés. D'altra banda, també són clars en què aquesta congestió es pot previndre amb una adequada configuració de l'ACB. No obstant això, els paràmetres de configuració de l'ACB han de ser contínuament adaptats a la intensitat d'accessos per a poder obtindre unes prestacions òptimes. En la tesi es proposa una solució pràctica a aquest problema en la forma d'un esquema de configuració automàtica per a l'ACB; l'anomenem ACBC. Els resultats mostren que el nostre esquema pot aconseguir un acompliment molt proper a l'òptim sense importar la intensitat dels accessos. Així mateix, pot ser directament implementat en xarxes cel·lulars per a suportar el trànsit mMTC, ja que ha sigut dissenyat tenint en compte els estàndards del 3GPP. A més de les anàlisis descrites anteriorment per a xarxes cel·lulars, es realitza una anàlisi general per a aplicacions de comptadors intel·ligents. És a dir, estudiem un escenari de mMTC des de la perspectiva de les WSNs. Específicament, desenvolupem un model híbrid per a l'anàlisi de prestacions i l'optimització de protocols de WSNs d'accés aleatori i basats en clúster. Els resultats mostren la utilitat d'escoltar el mitjà sense fil per a minimitzar el nombre de transmissions i també de modificar les probabilitats de transmissió després d'una col·lisió. Pel que fa a eMBB, ens enfoquem en un escenari de distribució massiva de continguts, en el qual un mateix contingut és enviat de forma simultània a un gran nombre d'usuaris mòbils. Aquest escenari és problemàtic, ja que les estacions base de la xarxa cel·lular no compten amb mecanismes eficients de multicast o broadcast. Per tant, la solució que s'adopta comunament és la de replicar el contingut per a cadascun dels usuaris que ho sol·liciten; és clar que això és altament ineficient. Per a resoldre aquest problema, proposem l'ús d'esquemes de network coding i d'arquitectures cooperatives anomenades núvols mòbils. En concret, desenvolupem un protocol per a realitzar la distribució massiva de continguts de forma eficient, juntament amb un model analític per a la seua optimització. Els resultats demostren que el model proposat és simple i precís
The 5th generation (5G) of mobile networks is just around the corner. It is expected to bring extraordinary benefits to the population and to solve the majority of the problems of current 4th generation (4G) systems. The success of 5G, whose first phase of standardization has concluded, relies in three pillars that correspond to its main use cases: massive machine-type communication (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communication (URLLC). This thesis mainly focuses on the first pillar of 5G: mMTC, but also provides a solution for the eMBB in massive content delivery scenarios. Specifically, its main contributions are in the areas of: 1) efficient support of mMTC in cellular networks; 2) random access (RA) event-reporting in wireless sensor networks (WSNs); and 3) cooperative massive content delivery in cellular networks. Regarding mMTC in cellular networks, this thesis provides a thorough performance analysis of the RA procedure (RAP), used by the mobile devices to switch from idle to connected mode. These analyses were first conducted by simulation and then by an analytical model; both of these were developed with this specific purpose and include one of the most promising access control schemes: the access class barring (ACB). To the best of our knowledge, this is one of the most accurate analytical models reported in the literature and the only one that incorporates the ACB scheme. Our results clearly show that the highly-synchronized accesses that occur in mMTC applications can lead to severe congestion. On the other hand, it is also clear that congestion can be prevented with an adequate configuration of the ACB scheme. However, the configuration parameters of the ACB scheme must be continuously adapted to the intensity of access attempts if an optimal performance is to be obtained. We developed a practical solution to this problem in the form of a scheme to automatically configure the ACB; we call it access class barring configuration (ACBC) scheme. The results show that our ACBC scheme leads to a near-optimal performance regardless of the intensity of access attempts. Furthermore, it can be directly implemented in 3rd Generation Partnership Project (3GPP) cellular systems to efficiently handle mMTC because it has been designed to comply with the 3GPP standards. In addition to the analyses described above for cellular networks, a general analysis for smart metering applications is performed. That is, we study an mMTC scenario from the perspective of event detection and reporting WSNs. Specifically, we provide a hybrid model for the performance analysis and optimization of cluster-based RA WSN protocols. Results showcase the utility of overhearing to minimize the number of packet transmissions, but also of the adaptation of transmission parameters after a collision occurs. Building on this, we are able to provide some guidelines that can drastically increase the performance of a wide range of RA protocols and systems in event reporting applications. Regarding eMBB, we focus on a massive content delivery scenario in which the exact same content is transmitted to a large number of mobile users simultaneously. Such a scenario may arise, for example, with video streaming services that offer a particularly popular content. This is a problematic scenario because cellular base stations have no efficient multicast or broadcast mechanisms. Hence, the traditional solution is to replicate the content for each requesting user, which is highly inefficient. To solve this problem, we propose the use of network coding (NC) schemes in combination with cooperative architectures named mobile clouds (MCs). Specifically, we develop a protocol for efficient massive content delivery, along with the analytical model for its optimization. Results show the proposed model is simple and accurate, and the protocol can lead to energy savings of up to 37 percent when compared to the traditional approach.
Leyva Mayorga, I. (2018). On reliable and energy efficient massive wireless communications: the road to 5G [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/115484
TESIS
D, Rajaveerappa. "Design and Development of a Hybrid TDMA/CDMA MAC Protocol for Multimedia Wireless Networks". Thesis, Indian Institute of Science, 2004. http://hdl.handle.net/2005/89.
Testo completoHuang, Sheng-Huang, e 黃勝煌. "Study of writing efficiency for magnetic random access memory". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/71918821352074875183.
Testo completo國立清華大學
材料科學工程學系
98
A novel memory device based on the magnetoreisitive effect is known as magnetic random access memory (MRAM) and is also called “dream memory”. In this dissertation, we investigate the key issue of the MRAM - writing efficiency. Firstly, in the concept of spin torque transfer MRAM, we can manipulate the damping constant and saturation magnetization of CoFeB by simply adjusting the capping layers. We found that the Ta capping layer caused the intermixing, and increased the damping constant of CoFeB. By inserting various metals, the intermixing can be improved and the lower damping constant with Cu/Ta capping layers was obtained. Moreover, the results of micromagnetic simulation indicate that the optimal switching current density can be achieved by reducing the damping constant with a Cu capping layer. In our simulation results, we demonstrate that by changing the capping layer from Ta to Cu/Ta, we can effectively reduce the critical current density by 27 %. Secondly, in the concept of magnetic domain wall RAM (so called “race-track memory”), we demonstrate that the depinning probability of the transverse-type domain wall strongly depends on the domain wall configuration when the domain wall moves to the notch. We found that when the current density is larger than threshold current density, the domain wall structure periodically changes between transverse-type domain wall and antivortex-type domain wall. Due to this transition behavior, part of the spin torque energy contributes to the transformation of the domain wall structure. Since the antivortex-type domain wall stores more energy, the stored energy can help the domain wall to be depinned from the notch and increases the depinning probability. Finally, we take advantage of the magnetic domain wall and we propose a method which combines either conventional current- or field- driven MRAM with the magnetic domain wall. We demonstrate that the domain wall can be artificially created in patterned antiferromagnetic/ferromagnetic exchange bias system using ion irradiation. The magnetic domain wall was formed by the different switching fields in the irradiated and non-irradiated areas and could assist the magnetization switching. Furthermore, this study proposes a new type of MRAM design. A comparison of the proposed magnetoresistive device with the conventional ellipse one shows that the new design reduces the switching field and the critical current density by about 90.0 % and 68.8 %, respectively, in field- and current- driven cases. In both of these cases, we demonstrated the domain wall assisted magnetization reversal. This study provides an effect way to increase the writing efficiency of MRAM.
Lai, Li-Ya, e 賴俐雅. "A High Efficiency Automatic Write Mechanism for Resistive Random Access Memory". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/y53rsr.
Testo completoLiao, Yan-Yu, e 廖彥宇. "The Efficiency and Delay of Distributed Source Coding in Random Access Sensor Networks". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/64999886201146879760.
Testo completo國立清華大學
通訊工程研究所
95
In this thesis, we analyze the efficiency and delay of distributed source coding (DSC) in sensor networks under the random access setting. Consider a network of N sensors that observes correlated information from the environment and sends the local data to a central processor through direct transmission links. Due to the low message rate in sensor networks, we adopt the slotted ALOHA random access protocol where the time is divided into synchronized time slots and each sensor is allowed to access the time slots with independent probabilities. To eliminate the redundancy in the transmission data, the sensors encode the local messages based on the Slepian-Wolf DSC method. Specifically, the network is divided into K clusters and we assume that the sensors are encoded sequentially in a cluster such that the decoding of a particular message is reliant on the successful decoding of all the messages encoded earlier in the sequence. In this case, the loss of one message may result in the failure of other messages and the delay in the successful decoding of a particular message also varies from sensor to sensor. In this article, we analyze the performance of DSC in random access networks in terms of the rate of successful decoding, the average delay and the average energy consumption of each message. Specifically, we propose and compare different transmission probability assignments for DSC in the ALOHA network and emphasize the importance of the MAC design. Finally, we propose an adaptive MAC protocol such that improve the performance of our system.
Tsai, Ya-Ru, e 蔡雅如. "Design of Random Access Control Schemes for the M2M Communication in LTE Considering Efficiency and Priority". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/wkq6ca.
Testo completo國立臺灣科技大學
資訊工程系
105
As the technology evolves, networking technologies become more and more popular.As an increasing amount of devices are connected to a network, the machine-to-machine (M2M) communication has become pervasive. Because of a better coverage solution provided by the cellular network, it is one of networks which can be chosen for the M2M communication. Although the data size is small, the number of M2M devices is perhaps huge. When a lot of devices are trying to access the network in a short period, collisions are inevitable, leading to communication failure and degradation of service. To address such an issue, how to alleviate collisions in the random access of the long-term evolution (LTE) system is considered when M2M devices are added. We try to propose a random access scheme to enhance efficiency. By splitting the preamble into two sets, it is able to reduce the delay for M2M devices suffering from preamble collisions. The two sets include the one of M2M devices which never tried before and the one of backlogged M2M devices. Additionally, priority is considered for devices which can not tolerate a longer delay and the others. Actually, the coexistence M2M and human-to-human (H2H) devices form an issue to be addressed. This allows us to let H2H devices have a priority higher than M2M devices. Finally, our simulation results demonstrate that our proposed scheme can achieve the goal of delay reduction and access efficiency enhancement regardless of traffic loads within the network.
Chien, Tun-Fei, e 簡惇妃. "Ultra Low Voltage Read and High Efficiency Write Circuits for Resistive Random Access Memory in Low Power System". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/4p6cmh.
Testo completo國立清華大學
電機工程學系
102
The requirements of non-volatile memories for handheld consumer electronics, medical electronics, car electronics, and lots of electronic products become larger and larger, especially for large capacity, low cost, low power and high speed memory. After integrated with micro controller unit (MCU), it can effectively increase the chip performance. Flash memory is the mainstream embedded memory. However, it cannot achieve high speed write operation and be randomly accessed. Furthermore, it is difficult to scale down flash memory into deep nanometer scale. Thus, developing new nonvolatile memories is necessary. Among these emerging nonvolatile memories, Resistive Random Access Memory (ReRAM) is one of the most promising candidates. It has attractive characteristics such as low write power, small area, and logic-process compatibility which can lower the manufacturing cost. Currently, the most common memory cell structure is one transistor and one ReRAM (1T1R), which is suitable for high speed and low supply voltage embedded applications, particularly for devices powered by batteries. As devices shrink, ReRAMs have higher cell resistance (R) and greater variations in write time and R, which reduces the R-ratio (RH/RL) between the high-R state (HRS, RH) and low-R state (LRS, RL). ReRAM also has a high RL, which enables a larger voltage drop across ReRAM to reduce write voltage and cell-switch (CS) size. Thus, ReRAM memory macro designs suffer two major problems: 1. Small sensing margin (SM), limited read-VDDMIN, and slow access time (TAC) due to high-RL and small R-ratio. 2. Increase in energy due to large set DC-current (IDC-SET) resulting from wide set-time (TSET) distribution. Here, we propose swing-sample-and-couple voltage mode sense amplifier (SSC-VSA) and self-boost-write-termination (SBWT) scheme to solve above two major problems, respectively. Proposed SSC-VSA designs the VREF on specific voltage level, after the operation of the circuit, it can increase the usage of ΔVBLS_MIN (by up to 99%) as the SM for lower read VDDMIN and faster TAC. It can achieve 1.7x faster TAC across various VDD compared to conventional differential-input (CD) voltage mode sense amplifier. As for ReRAM write operation, proposed SBWT scheme is a 4T self-detective write-termination circuit. When ReRAM successfully sets (HRS→LRS), large IDC-SET will increase the BL voltage, enabling the positive feedback between BL and SBWT and cutting off the current path, which can save over 99% write power. We fabricated a 28nm 1Mb ReRAM memory macro. Under the 0.85V and 0.27V supply voltage, the measured read access times are 6.8ns and 404.4ns, respectively. Besides, the SBWT scheme has also been demonstrated.
Lu, Hsing-Chen, e 盧星辰. "Efficient Yield and Reliability Enhancement Techniques for Random Access Memories". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/26827284844866902668.
Testo completo國立中央大學
電機工程研究所
97
Yield and reliability are two key challenges for designing nano-scale chips. Embedded memory is one key component in modern system-on-chip (SoC) designs. It typically represents a significant portion of the chip area as well. Moreover, it is designed with the smallest transistors and aggressive design rules. Thus, the yield and reliability of embedded memories dominate that of SoCs. Therefore, efficient yield and reliability enhancement techniques for embedded memories are very important for SoCs. Built-in self-diagnosis (BISD) and built-in self-repair(BISR) are two key techniques for improving the yield of embedded memories. Typically, a BISD design exports diagnostic data serially. In the first part of this thesis, a diagnostic data compression technique is proposed to reduce the diagnostic data of a RAM with error correction code (ECC). By reusing the ECC circuit, the proposed approach can compress the diagnostic data efficiently with very low area cost. In the second part of this thesis, a transparent BISR scheme for RAMs with ECC is proposed to enhance the yield and reliability of RAMs. The transparent BISR scheme can perform off-line test/repair for RAMs in production phase. It also can perform online test/repair for RAMs in operation. In online test/repair mode, the transparent BISR scheme performs transparent march tests for the RAM under test and repairs the RAM cells with hard faults if some spares are unused after the off-line test/repair phase. This can prolong the reliability of the RAM. In comparison with existing transparent test approaches, the proposed transparent test approach has the following advantages: fault-location capability and low test complexity. Experimental results show that the area cost of the proposed transparent BISR scheme for RAMs with ECC is low—only about 4.8% for a 4K×39-bit SRAM. In the third part of this thesis, a shared transparent test and repair scheme for multiple homogeneous RAMs without ECC is proposed to reduce the area cost. In the shared transparent test and repair scheme, a shared code memory is designed to store the signature of a RAM under test. Thus, the RAMs sharing the code memory are tested and repaired one by one in a time-multiplexing method. Since the code memory is shared by multiple homogeneous RAMs, the area cost of the transparent test and repair scheme is reduced. In comparison with typical transparent BIST schemes, the proposed scheme has good fault location capability. The signature prediction phase is only 1N for an N×B-bit RAM.
Hung, Hsiang-tse, e 洪向澤. "An Efficient Scheduling and Random Access Hybrid Medium Access Control Protocol For Underwater Sensor Networks". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/40341108057180549109.
Testo completo世新大學
資訊管理學研究所(含碩專班)
99
Over 70% of our Earth's surface is covered by water, and the Underwater Sensor Networks (UWSN) can collection ocean information, monitor ocean environment. Since the UWSN can only use sound waves to transmit messages, it has the following features as opposed to the wireless sensor network, which uses radio waves to transmit messages: long propagation delay, lower available bandwidth and multi-path problem. The sink node’s broadcasting and collecting data from sensor nodes are routine works in the sensor networks, but many MAC protocols of sensor networks fail to consider the characteristics of these routine works to design an more efficient MAC protocol. In this thesis, we propose a cross-layered MAC protocol for UWSN named as Scheduling and Random Access Hybrid (SRH-MAC) protocol. In SRH-MAC channel is divided into several superframes with fixed length. Each superframe contains three periods, broadcast period, routine report period and event report period. During the broadcast and routine report periods, each sensor node broadcasts and gathers data in a predetermined time slot so as to avoid collisions and reduce idle waiting time. The data is received and transmitted from and to a predetermined neighboring source and destination nodes. The predetermined time slot, source, and destination nodes are set according to the broadcasting and gathering trees. During the event report period, the senor node reports the sensed event through the time slots reserved by exchanging RTS/CTS packets. Simulations have shown that the proposed SRH-MAC protocol performs better than existing protocols in terms of network throughput, broadcasting, and gathering latency.
Huang, Bing-Wei, e 黃秉偉. "Efficient Diagnosis and Repair Techniques for Drowsy Static Random Access Memories". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/38160709914490820240.
Testo completo國立中央大學
電機工程研究所
96
Memory core is one key component in system-on-chip (SOC) designs. Also, memory cores usually represent a significant portion of the chip area. Therefore, the yield of memory cores dominates the yield of the chip. Efficient yield-improvement techniques for memory cores thus are essential for improving the yield of the chip. Diagnosis and repair are two major techniques for improving the yields of memory cores. On the other hand, leakage power issue is another challenge for designing nano-scale SOCs. Drowsy static random access memory (SRAM) is one possible candidate of memory core with low-leakage power consumption. Therefore, we propose efficient diagnosis and repair techniques for drowsy SRAMs in this thesis. First, we propose a March D2 algorithm for distinguishing drowsy faults (DFs) from non-drowsy faults (NDFs). We also propose a March D6 diagnosis algorithm for distinguishing all DFs of drowsy SRAMs. The test complexity of a March D6 algorithm is O((10*log2N+17+9*log2W)*N), where N represents the number of words of the memory under test; W represents the word width of memory. Second, an efficient built-in self-repair (BISR) scheme is proposed to repair defective drowsy SRAMs. A new redundancy analysis (RA) algorithm is proposed to allocate redundancies of the drowsy SRAM with spare rows, spare columns, and drowsy-masking registers (DMRs) [2]. The proposed BISR scheme can repair DFs by disabling the drowsy operation mode of the corresponding rows with DMRs. Simulation results show that the repair rate (the ratio of the number of repaired memories to the number of defective memories) of the proposed RA algorithm is 91%, which is better than that of repair-most algorithm which offers 67% repair rate.
Thonangi, Risi. "Optimizing Database Algorithms for Random-Access Block Devices". Diss., 2015. http://hdl.handle.net/10161/10521.
Testo completoThe past decade has seen wide availability of solid-state drives (SSDs) in settings ranging from personal computing to enterprise storage. Their success over the hard disks is driven by performance considerations and cost savings. Besides SSDs based on flash memory, there have been ongoing efforts in developing other non-volatile memory technologies such as phase-change memory and MRAM. All these technologies enable what we refer to as random-access block devices. Unlike hard disks, these devices have fast random accesses; on the other hand, their writes are more expensive than their reads. In this work, we study how to optimize database and storage algorithms for the I/O characteristics of random-access block devices. Specifically, we tackle the following three problems.
The first one is about permuting data out-of-core. While external merge sort is popular for implementing permutation on hard disks, it carries unnecessary overhead in storing and comparing keys. We propose more efficient algorithms for a useful class of permutations called Address-Digit Permutations on random-access block devices.
The second problem is concurrency control for indexes on SSDs. Various indexes have been proposed for these devices, but to make such indexes practical, we must address the issue of concurrency control. We propose a novel indexing and concurrency control scheme which allows concurrent accesses during ongoing index reorganizations, and does so with minimal memory and block-level locking.
The third problem concerns log-structured merge, a popular indexing technique well-suited to random-access block devices. We show how an intelligent partial merge policy, combined with a block-preserving merge procedure, can significantly lower write traffic while preserving other advantages of log-structured merge.
Dissertation
Huang, Teng-Wei, e 黃騰葳. "A Contention-free Access Scheme and An Efficient Random Access Response Message for mMTC in 5G". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9qk9fn.
Testo completo國立交通大學
網路工程研究所
105
Massive Machine Type Communication (mMTC) has attracted increasing attention due to the explosive growth of IoT devices. Random access (RA) for a large number of mMTC user equipments (UEs) is especially difficult since the severe collisions problem between UEs and an eNB may overwhelm the available spectrum resources. To address this issue, we propose a contention-free access scheme and an efficient RA response (RAR) message for mMTC in 5G. The core idea is to avoid collisions happened between UEs and also the one-to-one mapping mechanism applied by 4G-Long-Tern Evolution (4G-LTE). To do so, we exploit the concept of Chinese Remainder Theorem (CRT) and prime {\em factorization} to encode the {\em hint} such that UEs can extract their required information accordingly. Our simulations show that we can reduce the access delay for mMTC UEs up to 80\%. Besides, we can reduce the RAR message size by 20\%--40\%. Such reduction can be translated to around 50\% improvement of spectrum efficiency in LTE-M.
Wang, Hua-Li, e 王華立. "An Energy Efficient Random Access Control Scheme in LTE-A Systems with Machine-to-Machine Communication". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04559152589682992686.
Testo completo國立交通大學
電信工程研究所
101
Machine-to-machine (M2M) communication is a type of communication. It makes the automatic information exchange between a machine and other machine or a machine and a machine type communication (MTC) server by integrating various wireless communication techniques to satisfy requirements of many applications. Because M2M communication can provide various automatic applications and open a new market, M2M communication is received public attention. But M2M communication needs to deploy a large number of machines everywhere, and bring the current 4G wireless communication system many challenges to be solved. In this thesis, we propose an energy efficient random access control (E2RAC) in which the fine access quality is provided through estimating the number of machines. As we separate access resources for different types of communication, different orders of the service quality can be provided. Simulation results show that the E2RAC scheme provide the better quality of service than the conventional scheme.