Packet Scheduling in Optical Switches and Interconnects
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Optical interconnects and switches are widely considered as a promising candidate to provide high and ultra-high speed interconnection. This thesis addresses several important issues and proposes solutions in packet scheduling and performance evaluation for various optical switching architectures, including: (1) optimal packet scheduling for output-buffered optical switches with limited-range wavelength conversion capability; (2) admissible traffic and maximum throughput for input-buffered optical switches; (3) packet scheduling in single-wavelength and wavelength-division-multiplexed (WDM) OpCut switches, a low-latency optical/electronic hybrid switch architecture; (4) energy-aware routing in hybrid optical networks-on-chip (NoC). In recent years, switches and interconnects draw increasingly more attention due to the fact that they tend to become a bottleneck at all levels: intra-chip, chip-to-chip, board level, and computer networks. There are many requirements posed on an interconnect network, such as low latency, high throughput, low error rate, low power consumption, as well as scalability. Finding a solution that can satisfy all these needs is a non-trivial task. Due to the huge bandwidth and low error rate, optical interconnects and switches are widely considered as a promising candidate for future high and ultra-high speed interconnect networks. As key topics in the development of optical switching networks, scheduling and performance evaluation have been attracting considerable research interest. While there has been extensive research in these fields for electronic networks, most of them cannot be directly leveraged for optical networks - on one hand, some components are still missing in optical domain, for example optical random access memory (RAM); on the other hand, the solutions for electronic networks do not take into consideration unique characteristics of optics, such as the capability of wavelength conversion. This dissertation addresses several important issues and proposes solutions in packet scheduling and performance evaluation for various optical switching architectures, including (1) the Augment to Full packet scheduling algorithm that maximizes throughput and minimizes average queuing delay simultaneously for output-buffered optical switches, making use of limited-range wavelength conversion; (2) a new fiber-delay-line (FDL) based input buffering fabric that is able to provide flexible buffering delay, and a weight-based scheduling algorithm, named Most Packet Wavelength-Fiber Pair First (MPWFPF), that delivers 100% throughput for input-buffered optical switches at speedup 1; (3) a basic three-stage scheduling procedure for the OpCut switch, furthermore, a pipeline mechanism for single-wavelength OpCut switches to relax time constraint and improve system throughput, and NP-hardness and inapproximability proof for the optimal scheduling problem in WDM OpCut switches, as well as bounded approximation algorithms; (4) an energy-aware routing mechanism for hybrid optical NoCs.