Sharif Digital Repository

Due to the increasing development of digital systems based on limited energy sources (i.e. battery), energy efficiency has become one of the most important concerns in the design of these systems. The use of multi-core architecture is an effective solution for the problem of reducing energy consumption. Hence using it in digital systems has become more common. In addition, enabling methods for reducing energy consumption on processor, helps in making energy more efficient. DVFS and DPM are the two major methods used for reducing dynamic and static energy consumption of processors. The using of multi-core architecture due to the higher chip density, results the static and dynamic energy... 

Most of current the MAC protocols for Wireless Sensor Networks (WSNs) concern about energy efficiency rather than low latency. The main source of energy consumption in the MAC layer is idle listening, and most of these protocols use duty cycling for reducing energy consumption. But duty cycling method increases packet delivery latency. This problem is very critical in real time applications where packets should meet their deadline. There are some solutions for this problem. For example a node forwards data packets multi hop away instead of one hop in a single cycle. In this research, an efficient cross layer MAC protocol for real time applications is proposed. In this protocol multi hop... 

Hard real-time embedded systems often operate in harsh environmental conditions that necessitate fault tolerant computing techniques. These embedded systems are also energy-constrained, since energy consumption is one of the key objectives. Examples include satellites, surveillance systems, autonomous seaborne and airborne systems. Generally, fault tolerance is obtained by hardware or time redundancy in these systems. Checkpointing with rollback recovery which employs time redundancy is one of the common techniques for tolerating transient faults in real-time embedded systems. Using checkpointing in energy constrained hard real-time systems should be carefully employed. In this thesis, we... 

Recently, the tradeoff between low energy consumption and high fault-tolerance has attracted a lot of attention as a key issue in the design of real-time embedded systems. Dynamic Voltage Scaling (DVS) is known as one of the most effective low energy techniques for real-time systems. Control-theoretic DVS techniques, which have been exploited recently for DVS-enabled systems, are able to adapt well to dynamic workload. In this thesis, we have combined the above two important issues i.e., the control-theoretic DVS and fault-tolerance, and investigated reducing the energy consumption of fault-tolerant hard real-time systems using feedback control theory. Our proposed feedback-based DVS method... 

Over the Recent Decade, the embedded systems have expanded to include a wide variety of products, ranging from digital cameras, to medical systems, to Radar and telecommunication systems, to sensor networks. Engineers strive to create ever smaller and faster products, many of which, such as battery operated systems, have stringent power requirements. Coupled with increasing pressure to decrease costs and time-to-market, the design constraints of embedded systems pose a serious challenge to embedded systems designers. Dynamic reconfigurable hardware can provide a flexible and efficient platform for satisfying the area, performance, cost, and power requirements of many embedded systems.... 

Many embedded systems must be highly reliable and have hard real-time constraints. Technology scaling has enabled integration of multiple fast cores in a single chip. This provides higher computation speed that can achieve low response time in real-time systems. However, shrinking transistor dimensions aggravates reliability threats. Furthermore, hard real-time embedded systems are usually subjected to severe power and energy consumption limitations imposed by battery and cooling units. Therefore, designing hard real-time embedded systems requires careful considerations of reliability and power/energy consumption issues. High reliability can be achieved through exploiting fault tolerance... 

This research uses the Comovement between electronic payment data with GDP growth rate and private consumption growth rate to nowcast these two important macroeconomics variables. We use point of sale data set from the beginning of 1392 to the end of autumn of 1395 in monthly frequency in mixed data sampling model to use the Comovement for Nowcasting. Besides, we use two other data set, sale of industrial electricity and sale of agricultural electricity. All of this data set gives a real time sense of macroeconomics. They are also free of mistake. We show that using of this data set in the frame of MIDAS can decrease the root mean square forecast error (RMSFE) relative to auto regressive... 

Under conventional seismic design strategies, civil engineering structures are designed to undergo inelastic deformation to dissipate earthquake energy, leading to residual displacements and nonlinear deformations in the structure. As a result, there is an essential need for structural health monitoring methods to detect and process these nonlinear behaviors. In this dissertation, a model-free Hysteresis Loop Analysis (HLA) method is developed to identify damage and monitor the structure's performance online, under the earthquake excitations in both severe linear and nonlinear scenarios. The structural models used to validate this method includes three types of one-story, five-story, and... 

In recent years, we have seen the proliferation of real-time and time-dependent systems. They have increased both in number and in complexity. Due to their increasing complexity, we need to model them and become assured of their correctness. Several formalisms have been devised for time-dependent systems. They include timed automaton and timed extensions of Petri nets. Our focus is on timed extension of activity networks and its model checking. Activity networksare powerful formalisms which allow designers to model the system in a natural, small and conceivable manner. This way, timed extension of activity networks can greatly help modelers. In this thesis, we propose a method to specify the... 

The main goal of this thesis is to verify real-time properties of timed coordinated systems specified by timed-Reo circuits using the model checking techniqe. We use Timed Buchi Automata of Records (TBAR) as the semantics of timed-Reo. The model checking is done by converting Timed Buchi Automata of Records to an extension of Timed Automata that are usingas input of UPPAAL tool. We introduce a writer-automaton, which is synchronous with the desired Timed Automata, for initializing input ports. A tool that transforms Timed Buchi Automata of Records to UPPAAL Timed Automata has been implemented. Finally, two model checking case studies are examined by usingof our implemented tool over UPPAAL  

Nowadays, due to the rapid growth of electric energy consumption at the distribution network level and the environmental problems caused by conventional generation units, it has become necessary to provide appropriate solutions to increase the penetration of renewable energy sources and optimally manage the consumers/prosumers at the demand side of power systems. In recent years, various methods have been proposed for demand-side energy management models and distributed energy resources (DERs) integration into the distribution network. Amongst them, the transactive coordination approach that employs the economic and control mechanisms for the management of DERs and responsive loads has been... 

Nowdays, embedded systems need high dependability and performance and low cost. Use of multicore processors cause increase performance, and can lead to increase dependability with its inherent redundancy. Also mixed critical leads to decrease cost and increase dependability, because designer just considers dependability techniques for high critical tasks. A lot of work to increase dependability of real-time multicore systems with mixed-criticality has been done. In this study, a comprehensive classification of the approaches that has been done in this area is provided. One of the issues that is expressed in muticore, is shared resources. In multicore platforms some resources like memory and... 

Compile-time optimizations play an important role in the efficient design of real-time embedded systems. Usually, compile-time optimizations are designed to reduce average-case execution time (ACET). While ACET is a main concern in high-performance computing systems, in realtime embedded systems concerns are different and worst-case execution time (WCET) is much more important than ACET. Therefore, WCET reduction is more desirable than ACET reduction in many real-time embedded systems. In this thesis, we propose a compile-time optimization method aimed at reducing WCET in real-time embedded systems. In the proposed method, based on the predicated execution capability of embedded processors,... 

Wireless Body Area Network (WBAN) is a set of various physiological sensors for remote monitoring and controlling of the patient’s health status. Detection of anomalies, containing faults and physiological stresses, and distinguishing between them can eliminate the need for constant presence of specialists and decrease the occurrence of False Alarm Rate (FAR).A supervisory hardware platform for WBAN architecture is introduced and implemented in this thesis. The proposed architecture contains three sensors for recording of biomedical signals, heart rate, SpO2 and body temperature simultaneously and transmitting them to central node wirelessly through Wi-Fi standard. This proposed architecture... 

Embedded real-time systems have limitations on power consumption, mainly due to battery usage and temperature constraints. In addition, a large part of these systems has timing constraints. These constraints should be considered when we use power management techniques. Nowadays, due to the use of fault-tolerance techniques, power consumption and especially peak power consumption are increased so it can miss Thermal Design Power constraint. Recently, due to the conservative design of TDP for chips, it is not considered, and hence, a new power constraint as Thermal Safe Power is defined for thermal and power characteristic of the system. The purpose of this study is to define an optimization... 

With the increase of renewable energy generation in power systems, the flexibility of power systems has been challenged and the high potential of resources in active distribution systems for providing flexibility has been noticed by system operators and planners to help system flexibility. In this regard, these resources can participate in the Flexible Ramp Product market which is a new product that is defined for this purpose. In this work, the management of these resources has been modeled in an active distribution system for participating in this market by considering the network constraints, the uncertainty of renewable generation and forecasted prices of products in DA and RT markets,... 

Mixed-criticality systems are introduced due to industrial interest to integrate different types of functionalities with varying importance into a common and shared computing platform. Low-energy consumption is vital in mixed-criticality systems due to their ever-increasing computation requirements and the fact that they are mostly supplied with batteries. In this thesis, we propose a novel reliability-aware energy management approach and three methods, Fair-DVFS, Stretch, and Combined Fair-DVFS/Stretch in which energy management targets non-safety-critical functionalities. The Fair-DVFS method lowers energy consumption by evenly distributing slack times between low-criticality tasks while... 

Real-time embedded systems play an important role in many areas of human life and energy consumption is an important constraint in their design. In these systems, SRAM-based on-chip scratchpad memories are used for holding code or data which suffer from high leakage power and low capacity per transistor. This has persuaded researchers to find alternative solutions and in recent years non-volatile memories have attracted a lot of attention. Compared to conventional memories like SRAM, non-volatile memories consume less leakage power and provide more capacity given the same number of transistors. In this dissertation, we propose new solutions for reducing the energy consumption of real-time... 

Embedded systems usually have limited energy budget, therefore energy management for these systems is important. On the other hand, many embedded systems have real-time and reliability constraints and such constraints are usually serious obstacles to effective energy management. Considering these tradeoffs between energy consumption and system reliability and timeliness, in this thesis, we consider system-level energy management techniques for embedded systems with both hard real-time and soft real-time tasks. Due to large search space of the problem, we use Genetic Algorithm in our proposed technique. Our proposed energy management technique guarantees the deadlines of hard real-time tasks... 

Providing low-power fault tolerance is usually an important requirement in real-time embedded systems. A faulty result in safety-critical systems and a failure to meet a deadline in hard real-time systems can cause catastrophic consequences for the system or environment. Therefore, these systems must be highly reliable and meet real-time constraints. Slack time in time redundancy techniques (e.g. roll-back recovery) can be used to increase system reliability and to save energy. Time redundancy techniques are suitable from an energy consumption point of view but may not be sufficiently reliable for tight real-time constraints. In the condition of tight timing constraints, the hardware...