This article is organized as follows. First, we review some previous work on NCSs and offer some improvements. Then, we summarize the fundamental issues in NCSs and examine them with different underlying network-scheduling protocols. We present NCS models with network-induced delay and analyze their stability using stability regions and a hybrid systems technique. Following that, we discuss methods to compensate network-induced delay and present experimental results over a physical network. Then, we model NCSs with packet dropout and multiple-packet transmission as asynchronous dynamical systems (ADSs) [11] and analyze their stability. Finally, we present our conclusions

Wireless network links are characterized by rapidly time varying channel conditions and battery energy limitations at the wireless mobile user nodes. Therefore static link control techniques that make sense in comparatively well behaved wired links do not necessarily apply to wireless links. New adaptive link layer control techniques are needed to provide robust and energy efficient operation even in the presence of orders of magnitude variations in bit error rates and other radio channel conditions. For example, recent research has advocated adaptive link layer techniques such as adaptive error control [Lettieri97], channel state dependent protocols [Bhagwat96, Fragouli97], and variable spreading gain [Chien97]. In this paper we explore one such adaptive technique: dynamic sizing of the MAC layer frame, the atomic unit that is sent through the radio channel. A trade-off exists between the desire to reduce header and physical layer overhead by making frames large, and th...

‡ Please send all correspondence to Paul Lettieri Low power consumption is a key design metric for portable wireless network devices where battery energy is a limited resource. The resultant energy efficient design problem can be addressed at various levels of system design, and indeed much research has been done for hardware power optimization and power management within a wireless device. However, with the increasing trend towards thin client type wireless devices that rely more and more on network based services, a high fraction of power consumption is being accounted for by the transport of packet data over wireless links [Stemm96]. This offers an opportunity to optimize for low power in higher layer network protocols responsible for data communication among multiple wireless devices. Consider the data link protocols that transport bits across the wireless link. While traditionally designed around the conventional metrics of throughput and latency, a proper design offers many opportunities for optimizing the metric most relevant to battery operated devices: the amount of battery energy consumed per useful user level bit transmitted across the wireless link. This includes energy spent in the physical radio transmission process, as well as in computation such as signal processing and error coding. This paper describes how energy efficiency in the wireless data link can be enhanced via adaptive frame length control in concert with adaptive error control based on hybrid FEC (forward error correction) and ARQ (automatic repeat request). Key to this approach is a high degree of

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This paper describes the system, our experiences with its implementation, and its applicability to simulation modeling. We report on performance measurements of different implementations of the simulation scheduler, and of different algorithms for simulating service disciplines

Optical fibers offer high potential for interconnection networks (INs) for multiprocessing and multicomputing due to their ability to carry a large number of wavelengths at high transmission rates but current technology limits their use to only a few dozen wavelengths. One approach to circumvent this limitation is to arrange processing nodes (PNs) on fibers in groups and spatially separating those clusters. Grouping those clusters together in a higher level structure, or hierarchy, allows any node to communicate with any other in a large network while using only a few wavelengths. One potential hierarchy presented previously [1], Hierarchical Optical Ring Interconnection Network (HORN), uses a clustered hierarchical approach in which clusters consist of a set of PEs optically interconnected and these clusters are optically connected by higher level rings. As such, a highly scalable architecture is achieved, overcoming the fixed number of available wavelengths through spatial re...

1991-92: The intent of the system was to accomodate virtual environments for academic and industrial applications. More than just interactive 3D graphics, the engine provided for arbitrary information (think: nested tuples) far beyond just n-Dimensions. Criteria included changing the geometry engine on-the-fly so researchers could get a better understanding of what VR is. For a contemporary perspective (2001), please see: http://www.metarealm.com/moses

Abstract—Previous packet length optimizations for sensor networks often employ a fixed optimal length scheme, while in this study we present DPLC, a Dynamic Packet Length Control scheme. To make DPLC more efficient in terms of channel utilization, we incorporate a lightweight and accurate link estimation method that captures both physical channel conditions and interferences. We further provide two easy-to-use services, i.e., small message aggregation and large message fragmentation, to facilitate upper-layer application programming. The implementation of DPLC based on TinyOS 2.1 is lightweight, with respect to computation, memory, and header overhead. Our experiments using a real indoor testbed running CTP show that DPLC results in a 13 % reduction in transmission overhead and a 41.8 % reduction in energy consumption compared with the original protocol, and a 21 % reduction in transmission overhead and a 15.1 % reduction in energy consumption compared with simple aggregation schemes. I.

Optical fibers offer high potential for interconnection networks (INs) for multiprocessing and multicomputing due to their ability to carry a large number of wavelengths at high transmission rates but current technology limits their use to only a few dozen wavelengths. One approach to circumvent this limitation is to arrange processing nodes (PNs) on fibers in groups and spatially separating those clusters. Grouping those clusters together in a higher level structure, or hierarchy, allows any node to communicate with any other in a large network while using only a few wavelengths. One potential hierarchy presented previously [1], Hierarchical Optical Ring Interconnection Network (HORN), uses a clustered hierarchical approach in which clusters consist of a set of PEs optically interconnected and these clusters are optically connected by higher level rings. As such, a highly scalable architecture is achieved, overcoming the fixed number of available wavelengths through spatial reuse of t...

Narrowband integrated voice/data networks require that congestion control and bandwidth management techniques be implemented in order to provide the desired quality of service. An adaptive voice/data switch has been developed to demonstrate the application of the Sinusoidal Transform Coder (STC), a low bit-rate digital speech coder, to the implementation of integrated networks. In this work, an integrated network management and control protocol is designed and implemented. The protocol exploits the unique capabilities of the STC for congestion control in a narrowband integrated network environment. A software testbed is constructed to evaluate the speech coding technique and to verify the protocol functionality. The results of informal listening tests on several simulated conversations suggest that this coder is well-suited for bandwidth reallocation based on dynamic rate adjustment. The performance of the adaptive voice/data switch congestion control mechanism is studied using simulation. Acknowledgements Iwould like to thank Dr. Joseph Evans, my advisor, for his help and advice