Sharif Digital Repository

Delivering multimedia over wireless Networks is a very challenging task. Multimedia delivery inherently has strict quality-of-service (QoS) requirement on bandwidth, delay, and delay jitter.. The advent of wireless networks further exacerbates the variance of network conditions and brings greater challenges for multimedia delivery. Network coding is realized to have great potential for improving throughput limitation of current multi-hop wireless networks. The most significant characteristic of network coding is to send more information in each transmission by combining information from different sources leading to increased bandwidth and network throughput, decreased energy consumption and... 

Appearance of CUDA architecture results in GPU introduction as a suitable platform for parallel processing. Massive usage of GPGPUs in various applications forces the manufacturers to produce this processor with different configurations based on their application demands. But always the design approach observes a ratio between processing capability and bandwidth of GPGPUs. In this way mostly in all GPGPU series the bandwidth increases with growth of GPGPU processing power. At first glance this ratio seems reasonable because more process needs more data. However this approach does not pay attention to the behavior of a wide range of workloads which do not need such a bandwidth. Mentioned... 

In recent years applying solid state drives in data centers, cloud computing infrastructures and commercial servers have had a considerable growth. Low power consumption, high throughput and resistance to physical damages are some of the advantages of SSDs over HDDs. In recent works the necessity of using an interconnection network as a communication subcomponent between memory flash chips and disk controller is described. Disk mechanisms (mapping, wear-leveling and garbage collection) influence on throughput of the network. Based on this fact in this research an analytical model is provided considering disk mechanisms, flash chip structure and traffic characteristics. The error of the model... 

Frequency synthesizers are one of the most critical building blocks of RF systems. Their task is to produce high-frequency precise and stable clock signals from a low-frequency source. The signal used in mixers to up-convert and down-convert desired signals in transceivers and the precise clock of analog to digital converters are made by frequency synthesizers. Designing frequency synthesizer, because of its lots of parameter and dependency of these parameters to each other, is a hard task which forces designers to propose new structures. In this thesis, an integer-N frequency synthesizer for Bluetooth application, with the goals of decreasing spurious tones power and settling time, is... 

Efficient radio frequency (RF) power amplifiers (PAs) are critical in portable battery-operated wireless communication systems because they can dominate the power consumption. Linear amplifiers are enough linear but suffer from poor efficiency. On the other hand, switching power amplifier are efficient but are nonlinear and just amplify constant envelope signals. Two conventional methods for increasing transmitter efficiency and linearity are envelope elimination and restoration (EER) and envelope tracking (ET). In both methods, supply modulator controls RF power amplifier supply based on the signal envelope. Efficiency and bandwidth are critical factors in supply modulator. Thus hybrid... 

In this research, an electromagnetic wave absorber based on metamaterial structures is designed and built that is able to absorb a significant part of the wave power (up to 90%) in the millimeter wave band. The characteristics of this absorber are very low thickness (about a quarter of the wavelength compared to the central frequency) and high absorption bandwidth (up to 50% compared to the central frequency). Among the various structures studied, the structure of mesh arrays or conductive loops was selected for design. Using the Babinet principle, a transmission line model was proposed to analyze the behavior of this structure and became the basis for the design of the electromagnetic... 

With the increasing volume of digital data, the design of high-performance storage systems has become one of the major concerns of storage architects. Redundant Array of Independent Disks (RAID) based on either software or hardware implementation is commonly used in storage systems. Our thorough survey of previous work shows that there has been no study comparing and characterizing the efficiency of these two implementations on an array of solid state drives. In this thesis, we examine and compare the performance of software RAID compared to hardware RAID controller. In our study, we investigate major performance metrics including bandwidth, latency, and the number of inputs and outputs per...