An Efficient and Low Density Crossbar Switch Design for NoC

Code Division Multiple Access (CDMA) is a sort of multiplexing that facilitates various signals to occupy a single transmission channel. In this medium, sharing is enabled in the code space by assigning a limited number of N-chip length orthogonal spreading codes to the processing elements sharing interconnect. Serial and parallel overloaded CDMA interconnect (OCI) architecture variants are presented to adhere to different area, delay, and power requirements. Compared with the conventional CDMA crossbar, on a  Xilinx  Artix-7  AC701  FPGA  kit,  the  serial  OCI crossbar achieves 100% higher bandwidth, 31% less resource utilization, and 45% power saving, while the parallel OCI crossbar achieves N times higher  bandwidth  compared with the serial OCI crossbar at the expense of increased area  and power consumption. A 65-node OCI-based star NoC is implemented, evaluated, and compared with an equivalent space division multiple access based torus NoC for various synthetic traffic patterns. The evaluation results in terms of the resource utilization and throughput highlight the OCI as a promising technology to implement the physical layer of NoC routers

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

The implementation of an LDPC decoder in a Network on Chip environment

The proposed project takes origin from a cooperation initiative named NEWCOM++ among research groups to develop 3G wireless mobile system. This work, in particular, tries to focuse on the communication errors arising on a message signal characterized by working under WiMAX 802.16e standard. It will be shown how this last wireless generation protocol needs a specific flexible instrumentation and why an LDPC error correction code suitable in order to respect the quality restrictions. A chapter will be dedicated to describe, not from a mathematical point of view, the LDPC algorithm theory and how it can be graphically represented to better organize the decodification process. The main objective of this work is to validate the PHAL-concept when addressing a complex and computationally intensive design like the LDPC encoder/decoder. The expected results should be both conceptual; identifying the lacks on the PHAL concept when addressing a real problem; and second to determine the overhead introduced by PHAL in the implementation of a LDPC decoder. The mission is to build a NoC (Network on Chip) able to perform the same task of a general purpose processor, but in less time and with better efficiency, in terms of component flexibility and throughput. The single element of the network is a basic processor element (PE) formed by the union of two separated components: a special purpose processor ASIP, the responsible of the input data LDPC decoding, and the router component PHAL, checking incoming data packets and scanning the temporization of tasks execution. Supported by a specific programming tool, the ASIP has been completely designed, from the architecture resources to the instruction set, through a language like C. Realized in this SystemC code and converted in VHDL language, it's been synthesized as to fit onto an FPGA of the Xilinx Virtex-5 family. Although the main purpose regards the making of an application as flexible as possible, a WiMAX-orientated LDPC implemented on a FPGA saves space and resources, choosing the one that best suits the project synthesis. This is because encoders and decoders will have to find room in the communication tools (e.g. modems) as best as possible. The whole network scenary has been mounted through a Linux application, acting as a master element. The entire environment will require the use of VPI libraries and components able to manage the communication protocols and interfacing mechanisms

A Resilient 2-D Waveguide Communication Fabric for Hybrid Wired-Wireless NoC Design

Hybrid wired-wireless Network-on-Chip (WiNoC) has emerged as an alternative solution to the poor scalability and performance issues of conventional wireline NoC design for future System-on-Chip (SoC). Existing feasible wireless solution for WiNoCs in the form of millimeter wave (mm-Wave) relies on free space signal radiation which has high power dissipation with high degradation rate in the signal strength per transmission distance. Moreover, over the lossy wireless medium, combining wireless and wireline channels drastically reduces the total reliability of the communication fabric. Surface wave has been proposed as an alternative wireless technology for low power on-chip communication. With the right design considerations, the reliability and performance benefits of the surface wave channel could be extended. In this paper, we propose a surface wave communication fabric for emerging WiNoCs that is able to match the reliability of traditional wireline NoCs. First, we propose a realistic channel model which demonstrates that existing mm-Wave WiNoCs suffers from not only free-space spreading loss (FSSL) but also molecular absorption attenuation (MAA), especially at high frequency band, which reduces the reliability of the system. Consequently, we employ a carefully designed transducer and commercially available thin metal conductor coated with a low cost dielectric material to generate surface wave signals with improved transmission gain. Our experimental results demonstrate that the proposed communication fabric can achieve a 5dB operational bandwidth of about 60GHz around the center frequency (60GHz). By improving the transmission reliability of wireless layer, the proposed communication fabric can improve maximum sustainable load of NoCs by an average of 20:9% and 133:3% compared to existing WiNoCs and wireline NoCs, respectively

A resilient 2-D waveguide communication fabric for hybrid wired-wireless NoC design

Hybrid wired-wireless Network-on-Chip (WiNoC) has emerged as an alternative solution to the poor scalability and performance issues of conventional wireline NoC design for future System-on-Chip (SoC). Existing feasible wireless solution for WiNoCs in the form of millimeter wave (mm-Wave) relies on free space signal radiation which has high power dissipation with high degradation rate in the signal strength per transmission distance. Moreover, over the lossy wireless medium, combining wireless and wireline channels drastically reduces the total reliability of the communication fabric. Surface wave has been proposed as an alternative wireless technology for low power on-chip communication. With the right design considerations, the reliability and performance benefits of the surface wave channel could be extended. In this paper, we propose a surface wave communication fabric for emerging WiNoCs that is able to match the reliability of traditional wireline NoCs. First, we propose a realistic channel model which demonstrates that existing mm-Wave WiNoCs suffers from not only free-space spreading loss (FSSL) but also molecular absorption attenuation (MAA), especially at high frequency band, which reduces the reliability of the system. Consequently, we employ a carefully designed transducer and commercially available thin metal conductor coated with a low cost dielectric material to generate surface wave signals with improved transmission gain. Our experimental results demonstrate that the proposed communication fabric can achieve a 5dB operational bandwidth of about 60GHz around the center frequency (60GHz). By improving the transmission reliability of wireless layer, the proposed communication fabric can improve maximum sustainable load of NoCs by an average of 20:9% and 133:3% compared to existing WiNoCs and wireline NoCs, respectively

Weighted Round Robin Configuration for Worst-Case Delay Optimization in Network-on-Chip

We propose an approach for computing the end-to-end delay bound of individual variable bit-rate flows in a FIFO multiplexer with aggregate scheduling under Weighted Round Robin (WRR) policy. To this end, we use network calculus to derive per-flow end-to-end equivalent service curves employed for computing Least Upper Delay Bounds (LUDBs) of individual flows. Since real time applications are going to meet guaranteed services with lower delay bounds, we optimize weights in WRR policy to minimize LUDBs while satisfying performance constraints. We formulate two constrained delay optimization problems, namely, Minimize-Delay and Multiobjective optimization. Multi-objective optimization has both total delay bounds and their variance as minimization objectives. The proposed optimizations are solved using a genetic algorithm. A Video Object Plane Decoder (VOPD) case study exhibits 15.4% reduction of total worst-case delays and 40.3% reduction on the variance of delays when compared with round robin policy. The optimization algorithm has low run-time complexity, enabling quick exploration of large design spaces. We conclude that an appropriate weight allocation can be a valuable instrument for delay optimization in on-chip network designs

Thermal-Aware Networked Many-Core Systems

Advancements in IC processing technology has led to the innovation and growth happening in the consumer electronics sector and the evolution of the IT infrastructure supporting this exponential growth. One of the most difficult obstacles to this growth is the removal of large amount of heatgenerated by the processing and communicating nodes on the system. The scaling down of technology and the increase in power density is posing a direct and consequential effect on the rise in temperature. This has resulted in the increase in cooling budgets, and affects both the life-time reliability and performance of the system. Hence, reducing on-chip temperatures has become a major design concern for modern microprocessors. This dissertation addresses the thermal challenges at different levels for both 2D planer and 3D stacked systems. It proposes a self-timed thermal monitoring strategy based on the liberal use of on-chip thermal sensors. This makes use of noise variation tolerant and leakage current based thermal sensing for monitoring purposes. In order to study thermal management issues from early design stages, accurate thermal modeling and analysis at design time is essential. In this regard, spatial temperature profile of the global Cu nanowire for on-chip interconnects has been analyzed. It presents a 3D thermal model of a multicore system in order to investigate the effects of hotspots and the placement of silicon die layers, on the thermal performance of a modern ip-chip package. For a 3D stacked system, the primary design goal is to maximise the performance within the given power and thermal envelopes. Hence, a thermally efficient routing strategy for 3D NoC-Bus hybrid architectures has been proposed to mitigate on-chip temperatures by herding most of the switching activity to the die which is closer to heat sink. Finally, an exploration of various thermal-aware placement approaches for both the 2D and 3D stacked systems has been presented. Various thermal models have been developed and thermal control metrics have been extracted. An efficient thermal-aware application mapping algorithm for a 2D NoC has been presented. It has been shown that the proposed mapping algorithm reduces the effective area reeling under high temperatures when compared to the state of the art.Siirretty Doriast

Energy Efficient Cooperative Communication

This dissertation studies several problems centered around developing a better understanding of the energy efficiency of cooperative wireless communication systems. Cooperative communication is a technique where two or more nodes in a wireless network pool their antenna resources to form a virtual antenna array . Over the last decade, researchers have shown that many of the benefits of real antenna arrays, e.g. spatial diversity, increased range, and/or decreased transmission energy, can be achieved by nodes using cooperative transmission. This dissertation extends the current body of knowledge by providing a comprehensive study of the energy efficiency of two-source cooperative transmission under differing assumptions about channel state knowledge, cooperative protocol, and node selfishness. The first part of this dissertation analyzes the effect of channel state information on the optimum energy allocation and energy efficiency of a simple cooperative transmission protocol called orthogonal amplify-and-forward (OAF). The source nodes are required to achieve a quality-of service (QoS) constraint, e.g. signal to noise ratio or outage probability, at the destination. Since a QoS constraint does not specify a unique transmit energy allocation when the nodes use OAF cooperative transmission, minimum total energy strategies are provided for both short-term and long-term QoS constraints. For independent Rayleigh fading channels, full knowledge of the channel state at both of the sources and at the destination is shown to significantly improve the energy efficiency of OAF cooperative transmission as well as direct (non-cooperative) transmission. The results also demonstrate how channel state knowledge affects the minimum total energy allocation strategy. Under identical channel state knowledge assumptions, the results demonstrate that OAF cooperative transmission tends to have better energy efficiency than direct transmission over a wide range of channel conditions. The second part of this dissertation focuses on the development of an opportunistic hybrid cooperative transmission protocol that achieves increased energy efficiency by not only optimizing the resource allocation but also by selecting the most energy efficient cooperative transmission protocol from a set of available protocols according to the current channel state. The protocols considered in the development of the hybrid cooperative transmission protocol include compress-and-forward (CF), estimate-and-forward (EF), non-orthogonal amplify-and-forward (NAF), and decode-and-forward (DF). Instantaneous capacity results are analyzed under the assumption of full channel state knowledge at both of the sources and the destination node. Numerical results are presented showing that the delay limited capacity and outage probability of the hybrid cooperative transmission protocol are superior to that of any single protocol and are also close to the cut-set bound over a wide range of channel conditions. The final part of this dissertation focuses on the issue of node selfishness in cooperative transmission. It is common to assume in networks with a central authority, e.g. military networks, that nodes will always be willing to offer help to other nodes when requested to do so. This assumption may not be valid in ad hoc networks operating without a central authority. This section of the dissertation considers the effect selfish behavior on the energy efficiency of cooperative communication systems. Using tools from non-cooperative game theory, a two-player relaying game is formulated and analyzed in non-fading and fading channel scenarios. In non-fading channels, it is shown that a cooperative equilibrium can exist between two self-interested sources given that the end of the cooperative interaction is uncertain, that the sources can achieve mutual benefit through cooperation, and that the sources are sufficiently patient in the sense that they value future payoffs. In fading channels, a cooperative conditional trigger strategy is proposed and shown to be an equilibrium of the two-player game. Sources following this strategy are shown to achieve an energy efficiency very close to that of a centrally-controlled system when they are sufficiently patient. The results in this section show that cooperation can often be established between two purely self-interested sources without the development of extrinsic incentive mechanisms like virtual currency

On Energy Efficient Computing Platforms

In accordance with the Moore's law, the increasing number of on-chip integrated transistors has enabled modern computing platforms with not only higher processing power but also more affordable prices. As a result, these platforms, including portable devices, work stations and data centres, are becoming an inevitable part of the human society. However, with the demand for portability and raising cost of power, energy efficiency has emerged to be a major concern for modern computing platforms. As the complexity of on-chip systems increases, Network-on-Chip (NoC) has been proved as an efficient communication architecture which can further improve system performances and scalability while reducing the design cost. Therefore, in this thesis, we study and propose energy optimization approaches based on NoC architecture, with special focuses on the following aspects. As the architectural trend of future computing platforms, 3D systems have many bene ts including higher integration density, smaller footprint, heterogeneous integration, etc. Moreover, 3D technology can signi cantly improve the network communication and effectively avoid long wirings, and therefore, provide higher system performance and energy efficiency. With the dynamic nature of on-chip communication in large scale NoC based systems, run-time system optimization is of crucial importance in order to achieve higher system reliability and essentially energy efficiency. In this thesis, we propose an agent based system design approach where agents are on-chip components which monitor and control system parameters such as supply voltage, operating frequency, etc. With this approach, we have analysed the implementation alternatives for dynamic voltage and frequency scaling and power gating techniques at different granularity, which reduce both dynamic and leakage energy consumption. Topologies, being one of the key factors for NoCs, are also explored for energy saving purpose. A Honeycomb NoC architecture is proposed in this thesis with turn-model based deadlock-free routing algorithms. Our analysis and simulation based evaluation show that Honeycomb NoCs outperform their Mesh based counterparts in terms of network cost, system performance as well as energy efficiency.Siirretty Doriast