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When designing architectures and protocols for data traffic requiring real-time services, one of the major design goals is to guarantee that traffic deadlines can be met. However, many real-time applications also have additional requirements such as high throughput, high reliability, or energy efficiency. High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions, while wireless industrial applications, communicating control data, require support of reliability and guarantees of real-time predictability at the same time. To meet the requirements of high-performance embedded systems, this thesis work proposes two multi-wavelength high-speed passive optical networks. To enable reliable wireless industrial communications, a framework in­corporating carefully scheduled retransmissions is developed. All solutions are based on a single-hop star topology, predictable Medium Access Control algorithms and Earliest Deadline First scheduling, centrally controlled by a master node. Further, real-time schedulability analysis is used as admission control policy to provide delay guarantees for hard real-time traffic. For high-performance embedded systems an optical star network with an Arrayed Waveguide Grating placed in the centre is suggested. The design combines spatial wavelength re­use with fixed-tuned and tuneable transceivers in the end nodes, enabling simultaneous transmis­sion of both control and data traffic. This, in turn, permits efficient support of heterogeneous traf­fic with both hard and soft real-time constraints. By analyzing traffic dependencies in this mul­tichannel network, and adapting the real-time schedulability analysis to incorporate these traffic dependencies, a considerable increase of the possible guaranteed throughput for hard real-time traffic can be obtained. Most industrial applications require using existing standards such as IEEE 80

In modern factory automation systems, data communication plays a vital role. Different nodes like control systems, sensors and actuators can communicate over a wireless or wired industrial network. The data traffic generated is often scheduled for periodic transmission, where each single message or packet must arrive in time. For this real-time communication, methods have been developed to support communication services with a guaranteed throughput and delay bound for such periodic traffic, but merely under the assumption of error-free communication. However, the possibility for errors in the transmission still exists due to, e.g. noise or interference. A node receiving sensor values from a sensor in the system might then be forced to rely upon an older sensor value from the latest period, possibly leading to inaccuracies in control loops which can compromise the functioning of the system. In safety-critical systems, redundant networks or communication channels are frequently added to cope with errors, leading to more expensive systems. In this chapter, we will describe an alternative approach where erroneous data packets are retransmitted in a way that does not jeopardise any earlier stated real-time guarantees for ordinary transmissions. Using our framework, the reliability of real-time communication can be increased in a more cost-efficient way. We describe in this chapter an overview of our framework for reliable real-time communication, while details of our approach can be found in our earlier publications. In the light of the emerging use of wireless communication, the framework proves to be especially useful due to the high bit error rate inherent to the wireless medium. However, the framework is naturally also attractive for wired communication systems.

In modern factory automation systems, data communication plays a vital role. Different nodes like control systems, sensors and actuators can communicate over a wireless or wired industrial network. The data traffic generated is often scheduled for periodic transmission, where each single message or packet must arrive in time. For this real-time communication, methods have been developed to support communication services with a guaranteed throughput and delay bound for such periodic traffic, but merely under the assumption of error-free communication. However, the possibility for errors in the transmission still exists due to, e.g. noise or interference. A node receiving sensor values from a sensor in the system might then be forced to rely upon an older sensor value from the latest period, possibly leading to inaccuracies in control loops which can compromise the functioning of the system. In safety-critical systems, redundant networks or communication channels are frequently added to cope with errors, leading to more expensive systems. In this chapter, we will describe an alternative approach where erroneous data packets are retransmitted in a way that does not jeopardise any earlier stated real-time guarantees for ordinary transmissions. Using our framework, the reliability of real-time communication can be increased in a more cost-efficient way. We describe in this chapter an overview of our framework for reliable real-time communication, while details of our approach can be found in our earlier publications. In the light of the emerging use of wireless communication, the framework proves to be especially useful due to the high bit error rate inherent to the wireless medium. However, the framework is naturally also attractive for wired communication systems.

In modern factory automation systems, data communication plays a vital role. Different nodes like control systems, sensors and actuators can communicate over a wireless or wired industrial network. The data traffic generated is often scheduled for periodic transmission, where each single message or packet must arrive in time. For this real-time communication, methods have been developed to support communication services with a guaranteed throughput and delay bound for such periodic traffic, but merely under the assumption of error-free communication. However, the possibility for errors in the transmission still exists due to, e.g. noise or interference. A node receiving sensor values from a sensor in the system might then be forced to rely upon an older sensor value from the latest period, possibly leading to inaccuracies in control loops which can compromise the functioning of the system. In safety-critical systems, redundant networks or communication channels are frequently added to cope with errors, leading to more expensive systems. In this chapter, we will describe an alternative approach where erroneous data packets are retransmitted in a way that does not jeopardise any earlier stated real-time guarantees for ordinary transmissions. Using our framework, the reliability of real-time communication can be increased in a more cost-efficient way. We describe in this chapter an overview of our framework for reliable real-time communication, while details of our approach can be found in our earlier publications. In the light of the emerging use of wireless communication, the framework proves to be especially useful due to the high bit error rate inherent to the wireless medium. However, the framework is naturally also attractive for wired communication systems.

When designing architectures and protocols for data traffic requiring real-time services, one of the major design goals is to guarantee that traffic deadlines can be met. However, many real-time applications also have additional requirements such as high throughput, high reliability, or energy efficiency. High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions, while wireless industrial applications, communicating control data, require support of reliability and guarantees of real-time predictability at the same time. To meet the requirements of high-performance embedded systems, this thesis work proposes two multi-wavelength high-speed passive optical networks. To enable reliable wireless industrial communications, a framework in­corporating carefully scheduled retransmissions is developed. All solutions are based on a single-hop star topology, predictable Medium Access Control algorithms and Earliest Deadline First scheduling, centrally controlled by a master node. Further, real-time schedulability analysis is used as admission control policy to provide delay guarantees for hard real-time traffic. For high-performance embedded systems an optical star network with an Arrayed Waveguide Grating placed in the centre is suggested. The design combines spatial wavelength re­use with fixed-tuned and tuneable transceivers in the end nodes, enabling simultaneous transmis­sion of both control and data traffic. This, in turn, permits efficient support of heterogeneous traf­fic with both hard and soft real-time constraints. By analyzing traffic dependencies in this mul­tichannel network, and adapting the real-time schedulability analysis to incorporate these traffic dependencies, a considerable increase of the possible guaranteed throughput for hard real-time traffic can be obtained. Most industrial applications require using existing standards such as IEEE 80

In modern factory automation systems, data communication plays a vital role. Different nodes like control systems, sensors and actuators can communicate over a wireless or wired industrial network. The data traffic generated is often scheduled for periodic transmission, where each single message or packet must arrive in time. For this real-time communication, methods have been developed to support communication services with a guaranteed throughput and delay bound for such periodic traffic, but merely under the assumption of error-free communication. However, the possibility for errors in the transmission still exists due to, e.g. noise or interference. A node receiving sensor values from a sensor in the system might then be forced to rely upon an older sensor value from the latest period, possibly leading to inaccuracies in control loops which can compromise the functioning of the system. In safety-critical systems, redundant networks or communication channels are frequently added to cope with errors, leading to more expensive systems. In this chapter, we will describe an alternative approach where erroneous data packets are retransmitted in a way that does not jeopardise any earlier stated real-time guarantees for ordinary transmissions. Using our framework, the reliability of real-time communication can be increased in a more cost-efficient way. We describe in this chapter an overview of our framework for reliable real-time communication, while details of our approach can be found in our earlier publications. In the light of the emerging use of wireless communication, the framework proves to be especially useful due to the high bit error rate inherent to the wireless medium. However, the framework is naturally also attractive for wired communication systems.

When designing architectures and protocols for data traffic requiring real-time services, one of the major design goals is to guarantee that traffic deadlines can be met. However, many real-time applications also have additional requirements such as high throughput, high reliability, or energy efficiency. High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions, while wireless industrial applications, communicating control data, require support of reliability and guarantees of real-time predictability at the same time. To meet the requirements of high-performance embedded systems, this thesis work proposes two multi-wavelength high-speed passive optical networks. To enable reliable wireless industrial communications, a framework in­corporating carefully scheduled retransmissions is developed. All solutions are based on a single-hop star topology, predictable Medium Access Control algorithms and Earliest Deadline First scheduling, centrally controlled by a master node. Further, real-time schedulability analysis is used as admission control policy to provide delay guarantees for hard real-time traffic. For high-performance embedded systems an optical star network with an Arrayed Waveguide Grating placed in the centre is suggested. The design combines spatial wavelength re­use with fixed-tuned and tuneable transceivers in the end nodes, enabling simultaneous transmis­sion of both control and data traffic. This, in turn, permits efficient support of heterogeneous traf­fic with both hard and soft real-time constraints. By analyzing traffic dependencies in this mul­tichannel network, and adapting the real-time schedulability analysis to incorporate these traffic dependencies, a considerable increase of the possible guaranteed throughput for hard real-time traffic can be obtained. Most industrial applications require using existing standards such as IEEE 80

In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using first come first served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for real-time analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.

In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using first come first served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for real-time analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.

In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using first come first served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for real-time analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.

In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using first come first served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for real-time analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.

In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using first come first served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for real-time analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.

Wireless sensor nodes are made up of small electronic devices which are capable of sensing, computing and transmitting data from harsh physical environments. These sensor nodes depend on batteries for energy, which get depleted at a fast rate because of the computation and communication operations these nodes have to perform. A well designed MAC (Medium Access Control) protocol can prolong the network life. Aset of previously reported MAC layer protocols has abilities to achieve some energy efficiency. In this paper, we first describe some assumptions made for the specific application area of surveillance applications. Then, we compare a set of MAC protocols in terms of their suitability to be used in wireless sensor networks for this type of applications. In addition to energy efficiency, keeping the delays reasonably low is a crucial factor when sensing and reporting an event. © 2008 IEEE., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

This paper presents a framework for how to use ARQ (automatic repeat request) in combination with real-time worst-case scheduling analysis to be able to support reliable hard real-time communication. We show how to handle retransmissions of erroneous data packets, while still not jeopardizing stated delay guarantees of other packets. We demonstrate this by taking a point-to-point link as an example. Through our simulation studies we have shown that a reduction of the message error rate by several orders of magnitude is possible with a reasonable utilization penalty., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Wireless sensor nodes are made up of small electronic devices which are capable of sensing, computing and transmitting data from harsh physical environments. These sensor nodes depend on batteries for energy, which get depleted at a fast rate because of the computation and communication operations these nodes have to perform. A well designed MAC (Medium Access Control) protocol can prolong the network life. Aset of previously reported MAC layer protocols has abilities to achieve some energy efficiency. In this paper, we first describe some assumptions made for the specific application area of surveillance applications. Then, we compare a set of MAC protocols in terms of their suitability to be used in wireless sensor networks for this type of applications. In addition to energy efficiency, keeping the delays reasonably low is a crucial factor when sensing and reporting an event. © 2008 IEEE., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

This paper presents a framework for how to use ARQ (automatic repeat request) in combination with real-time worst-case scheduling analysis to be able to support reliable hard real-time communication. We show how to handle retransmissions of erroneous data packets, while still not jeopardizing stated delay guarantees of other packets. We demonstrate this by taking a point-to-point link as an example. Through our simulation studies we have shown that a reduction of the message error rate by several orders of magnitude is possible with a reasonable utilization penalty., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Wireless sensor nodes are made up of small electronic devices which are capable of sensing, computing and transmitting data from harsh physical environments. These sensor nodes depend on batteries for energy, which get depleted at a fast rate because of the computation and communication operations these nodes have to perform. A well designed MAC (Medium Access Control) protocol can prolong the network life. Aset of previously reported MAC layer protocols has abilities to achieve some energy efficiency. In this paper, we first describe some assumptions made for the specific application area of surveillance applications. Then, we compare a set of MAC protocols in terms of their suitability to be used in wireless sensor networks for this type of applications. In addition to energy efficiency, keeping the delays reasonably low is a crucial factor when sensing and reporting an event. © 2008 IEEE., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

This paper presents a framework for how to use ARQ (automatic repeat request) in combination with real-time worst-case scheduling analysis to be able to support reliable hard real-time communication. We show how to handle retransmissions of erroneous data packets, while still not jeopardizing stated delay guarantees of other packets. We demonstrate this by taking a point-to-point link as an example. Through our simulation studies we have shown that a reduction of the message error rate by several orders of magnitude is possible with a reasonable utilization penalty., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions. This thesis proposes two multi-wavelength passive optical networks able to meet these demands. The networks are based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) placed in the centre. The intended application areas for the two networks are short range embedded communication systems like System Area Networks (SANs) and router architectures with electronic queuing. The AWG’s attractive property of spatial wavelength reuse, as well as the combination of fixed-tuned and tuneable transceivers in the end nodes, enables simultaneous control and data traffic transmission. This, in turn, makes it possible to support heterogeneous traffic with both hard and soft real-time constraints. Additionally, two Medium Access Control (MAC) protocols, one for each network solution, are developed. Traffic scheduling is centrally controlled by a node, the protocol processor, residing together with the AWG in a hub. All nodes use Earliest Deadline First (EDF) scheduling and communicate with the protocol processor through physical control channels. A case study, including simulations, in the field of Radar Signal Processing (RSP) and simulations using periodic real-time traffic are conducted for the two application areas respectively, showing very good results. Further, a deterministic real-time analysis is conducted to provide throughput and delay guarantees for hard real-time traffic and an increase in guaranteed traffic is achieved through an analysis of existing traffic dependencies in a multichannel network. Simulation results incorporating the traffic dependency analysis indicate a considerable increase in the possible guaranteed throughput of hard real-time traffic.

Wireless sensor nodes are made up of small electronic devices which are capable of sensing, computing and transmitting data from harsh physical environments. These sensor nodes depend on batteries for energy, which get depleted at a fast rate because of the computation and communication operations these nodes have to perform. A well designed MAC (Medium Access Control) protocol can prolong the network life. Aset of previously reported MAC layer protocols has abilities to achieve some energy efficiency. In this paper, we first describe some assumptions made for the specific application area of surveillance applications. Then, we compare a set of MAC protocols in terms of their suitability to be used in wireless sensor networks for this type of applications. In addition to energy efficiency, keeping the delays reasonably low is a crucial factor when sensing and reporting an event. © 2008 IEEE., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

This paper presents a framework for how to use ARQ (automatic repeat request) in combination with real-time worst-case scheduling analysis to be able to support reliable hard real-time communication. We show how to handle retransmissions of erroneous data packets, while still not jeopardizing stated delay guarantees of other packets. We demonstrate this by taking a point-to-point link as an example. Through our simulation studies we have shown that a reduction of the message error rate by several orders of magnitude is possible with a reasonable utilization penalty., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions. This thesis proposes two multi-wavelength passive optical networks able to meet these demands. The networks are based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) placed in the centre. The intended application areas for the two networks are short range embedded communication systems like System Area Networks (SANs) and router architectures with electronic queuing. The AWG’s attractive property of spatial wavelength reuse, as well as the combination of fixed-tuned and tuneable transceivers in the end nodes, enables simultaneous control and data traffic transmission. This, in turn, makes it possible to support heterogeneous traffic with both hard and soft real-time constraints. Additionally, two Medium Access Control (MAC) protocols, one for each network solution, are developed. Traffic scheduling is centrally controlled by a node, the protocol processor, residing together with the AWG in a hub. All nodes use Earliest Deadline First (EDF) scheduling and communicate with the protocol processor through physical control channels. A case study, including simulations, in the field of Radar Signal Processing (RSP) and simulations using periodic real-time traffic are conducted for the two application areas respectively, showing very good results. Further, a deterministic real-time analysis is conducted to provide throughput and delay guarantees for hard real-time traffic and an increase in guaranteed traffic is achieved through an analysis of existing traffic dependencies in a multichannel network. Simulation results incorporating the traffic dependency analysis indicate a considerable increase in the possible guaranteed throughput of hard real-time traffic.

This paper presents a framework for how to use ARQ (automatic repeat request) in combination with real-time worst-case scheduling analysis to be able to support reliable hard real-time communication. We show how to handle retransmissions of erroneous data packets, while still not jeopardizing stated delay guarantees of other packets. We demonstrate this by taking a point-to-point link as an example. Through our simulation studies we have shown that a reduction of the message error rate by several orders of magnitude is possible with a reasonable utilization penalty., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions. This thesis proposes two multi-wavelength passive optical networks able to meet these demands. The networks are based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) placed in the centre. The intended application areas for the two networks are short range embedded communication systems like System Area Networks (SANs) and router architectures with electronic queuing. The AWG’s attractive property of spatial wavelength reuse, as well as the combination of fixed-tuned and tuneable transceivers in the end nodes, enables simultaneous control and data traffic transmission. This, in turn, makes it possible to support heterogeneous traffic with both hard and soft real-time constraints. Additionally, two Medium Access Control (MAC) protocols, one for each network solution, are developed. Traffic scheduling is centrally controlled by a node, the protocol processor, residing together with the AWG in a hub. All nodes use Earliest Deadline First (EDF) scheduling and communicate with the protocol processor through physical control channels. A case study, including simulations, in the field of Radar Signal Processing (RSP) and simulations using periodic real-time traffic are conducted for the two application areas respectively, showing very good results. Further, a deterministic real-time analysis is conducted to provide throughput and delay guarantees for hard real-time traffic and an increase in guaranteed traffic is achieved through an analysis of existing traffic dependencies in a multichannel network. Simulation results incorporating the traffic dependency analysis indicate a considerable increase in the possible guaranteed throughput of hard real-time traffic.

Wireless sensor nodes are made up of small electronic devices which are capable of sensing, computing and transmitting data from harsh physical environments. These sensor nodes depend on batteries for energy, which get depleted at a fast rate because of the computation and communication operations these nodes have to perform. A well designed MAC (Medium Access Control) protocol can prolong the network life. Aset of previously reported MAC layer protocols has abilities to achieve some energy efficiency. In this paper, we first describe some assumptions made for the specific application area of surveillance applications. Then, we compare a set of MAC protocols in terms of their suitability to be used in wireless sensor networks for this type of applications. In addition to energy efficiency, keeping the delays reasonably low is a crucial factor when sensing and reporting an event. © 2008 IEEE., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

This paper presents a framework for how to use ARQ (automatic repeat request) in combination with real-time worst-case scheduling analysis to be able to support reliable hard real-time communication. We show how to handle retransmissions of erroneous data packets, while still not jeopardizing stated delay guarantees of other packets. We demonstrate this by taking a point-to-point link as an example. Through our simulation studies we have shown that a reduction of the message error rate by several orders of magnitude is possible with a reasonable utilization penalty., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Wireless sensor nodes are made up of small electronic devices which are capable of sensing, computing and transmitting data from harsh physical environments. These sensor nodes depend on batteries for energy, which get depleted at a fast rate because of the computation and communication operations these nodes have to perform. A well designed MAC (Medium Access Control) protocol can prolong the network life. Aset of previously reported MAC layer protocols has abilities to achieve some energy efficiency. In this paper, we first describe some assumptions made for the specific application area of surveillance applications. Then, we compare a set of MAC protocols in terms of their suitability to be used in wireless sensor networks for this type of applications. In addition to energy efficiency, keeping the delays reasonably low is a crucial factor when sensing and reporting an event. © 2008 IEEE., ©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions. This thesis proposes two multi-wavelength passive optical networks able to meet these demands. The networks are based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) placed in the centre. The intended application areas for the two networks are short range embedded communication systems like System Area Networks (SANs) and router architectures with electronic queuing. The AWG’s attractive property of spatial wavelength reuse, as well as the combination of fixed-tuned and tuneable transceivers in the end nodes, enables simultaneous control and data traffic transmission. This, in turn, makes it possible to support heterogeneous traffic with both hard and soft real-time constraints. Additionally, two Medium Access Control (MAC) protocols, one for each network solution, are developed. Traffic scheduling is centrally controlled by a node, the protocol processor, residing together with the AWG in a hub. All nodes use Earliest Deadline First (EDF) scheduling and communicate with the protocol processor through physical control channels. A case study, including simulations, in the field of Radar Signal Processing (RSP) and simulations using periodic real-time traffic are conducted for the two application areas respectively, showing very good results. Further, a deterministic real-time analysis is conducted to provide throughput and delay guarantees for hard real-time traffic and an increase in guaranteed traffic is achieved through an analysis of existing traffic dependencies in a multichannel network. Simulation results incorporating the traffic dependency analysis indicate a considerable increase in the possible guaranteed throughput of hard real-time traffic.

Many future embedded systems are likely to contain System-on-Chip solutions with on-chip networks, and to achieve high aggregated throughputs in these networks, a switched topology can be used. For further performance improvements, the topology can be adapted to application demands, either when designing the chip or by run-time reconfiguration between different predefined application modes. In this report, we describe an algorithm for the choice of topology in, e.g., packet-switched on-chip networks, considering the real-time demands in terms of throughput and delay often put on such systems. To further address possible real-time demands, we include a feasibility analysis to check that the application, when mapped onto the system, will behave in line with its real-time demands. With input information about the traffic characteristics, our algorithm creates a topology and generates routing information for all logical traffic channels. In a case study, we show that our algorithm results in a topology that can outperform the use of state of the art topologies for high-performance computer architectures. Although we have targeted for reconfigurable Network-on-Chip architectures, the algorithm can also be used for other systems. Our algorithm gives the opportunity for topology choice at design stage, both for static network topologies and for reconfigurable network topologies that can be reconfigured during run-time.

In this report, we present a real-time analytical framework and the performance evaluation on our analysis. We propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using First Come First Served (FCFS) queuing but no traffic shapers. We choose switched Ethernet as an example to present the idea of our analysis and our experimental evaluations in this report.The remainder of the report is organized as follows. In Chapter 2, we define the network models, important concepts and terminology for real-time analysis. Chapter 3 presents our real-time analysis for isolated network elements. Chapter 4 gives end-to-end real-time analysis. Chapter 5 presents the performance evaluation of our results by simulation and comparison study and summarizes this report.

In this report, we present a real-time analytical framework and the performance evaluation on our analysis. We propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using First Come First Served (FCFS) queuing but no traffic shapers. We choose switched Ethernet as an example to present the idea of our analysis and our experimental evaluations in this report.The remainder of the report is organized as follows. In Chapter 2, we define the network models, important concepts and terminology for real-time analysis. Chapter 3 presents our real-time analysis for isolated network elements. Chapter 4 gives end-to-end real-time analysis. Chapter 5 presents the performance evaluation of our results by simulation and comparison study and summarizes this report.

Many future embedded systems are likely to contain System-on-Chip solutions with on-chip networks, and to achieve high aggregated throughputs in these networks, a switched topology can be used. For further performance improvements, the topology can be adapted to application demands, either when designing the chip or by run-time reconfiguration between different predefined application modes. In this report, we describe an algorithm for the choice of topology in, e.g., packet-switched on-chip networks, considering the real-time demands in terms of throughput and delay often put on such systems. To further address possible real-time demands, we include a feasibility analysis to check that the application, when mapped onto the system, will behave in line with its real-time demands. With input information about the traffic characteristics, our algorithm creates a topology and generates routing information for all logical traffic channels. In a case study, we show that our algorithm results in a topology that can outperform the use of state of the art topologies for high-performance computer architectures. Although we have targeted for reconfigurable Network-on-Chip architectures, the algorithm can also be used for other systems. Our algorithm gives the opportunity for topology choice at design stage, both for static network topologies and for reconfigurable network topologies that can be reconfigured during run-time.

Many future embedded systems are likely to contain System-on-Chip solutions with on-chip networks, and to achieve high aggregated throughputs in these networks, a switched topology can be used. For further performance improvements, the topology can be adapted to application demands, either when designing the chip or by run-time reconfiguration between different predefined application modes. In this report, we describe an algorithm for the choice of topology in, e.g., packet-switched on-chip networks, considering the real-time demands in terms of throughput and delay often put on such systems. To further address possible real-time demands, we include a feasibility analysis to check that the application, when mapped onto the system, will behave in line with its real-time demands. With input information about the traffic characteristics, our algorithm creates a topology and generates routing information for all logical traffic channels. In a case study, we show that our algorithm results in a topology that can outperform the use of state of the art topologies for high-performance computer architectures. Although we have targeted for reconfigurable Network-on-Chip architectures, the algorithm can also be used for other systems. Our algorithm gives the opportunity for topology choice at design stage, both for static network topologies and for reconfigurable network topologies that can be reconfigured during run-time.

In this report, we present a real-time analytical framework and the performance evaluation on our analysis. We propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using First Come First Served (FCFS) queuing but no traffic shapers. We choose switched Ethernet as an example to present the idea of our analysis and our experimental evaluations in this report.The remainder of the report is organized as follows. In Chapter 2, we define the network models, important concepts and terminology for real-time analysis. Chapter 3 presents our real-time analysis for isolated network elements. Chapter 4 gives end-to-end real-time analysis. Chapter 5 presents the performance evaluation of our results by simulation and comparison study and summarizes this report.

Many future embedded systems are likely to contain System-on-Chip solutions with on-chip networks, and to achieve high aggregated throughputs in these networks, a switched topology can be used. For further performance improvements, the topology can be adapted to application demands, either when designing the chip or by run-time reconfiguration between different predefined application modes. In this report, we describe an algorithm for the choice of topology in, e.g., packet-switched on-chip networks, considering the real-time demands in terms of throughput and delay often put on such systems. To further address possible real-time demands, we include a feasibility analysis to check that the application, when mapped onto the system, will behave in line with its real-time demands. With input information about the traffic characteristics, our algorithm creates a topology and generates routing information for all logical traffic channels. In a case study, we show that our algorithm results in a topology that can outperform the use of state of the art topologies for high-performance computer architectures. Although we have targeted for reconfigurable Network-on-Chip architectures, the algorithm can also be used for other systems. Our algorithm gives the opportunity for topology choice at design stage, both for static network topologies and for reconfigurable network topologies that can be reconfigured during run-time.

In this report, we present a real-time analytical framework and the performance evaluation on our analysis. We propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using First Come First Served (FCFS) queuing but no traffic shapers. We choose switched Ethernet as an example to present the idea of our analysis and our experimental evaluations in this report.The remainder of the report is organized as follows. In Chapter 2, we define the network models, important concepts and terminology for real-time analysis. Chapter 3 presents our real-time analysis for isolated network elements. Chapter 4 gives end-to-end real-time analysis. Chapter 5 presents the performance evaluation of our results by simulation and comparison study and summarizes this report.

More and more real-time systems are complex and distributed systems consisting of many sub-systems that must cooperate. In other words, those sub-systems must communicate with each other and to do this, still fullling the overall system specfication, real-time communication must be supported. Moreover, real-time communication is also becoming widely needed in networks like the Internet, spanning over large distances. In for example Internet, the support for different traffic classes is often described as supporting different QoS (Quality of Service) levels and does normally include some kind of specifcation to meet real-time demands. Real-time communication often relies on some kind of scheduling like EDF (Earliest Deadline First), but there are some important differences compared to standard single-processor scheduling. First, the transmission of a packet is, in most cases, non-preemptive. The ongoing transmission, and possibly also some of the already queued messages, can then not be interrupted when a more important message (e.g., with a shorter relative deadline) arrives or is generated. Moreover, a network, instead of a single link, makes the situation much more complex and one must consider things like medium access method, topology, multiple users on multiple nodes, non-deterministic access delay etc.

More and more real-time systems are complex and distributed systems consisting of many sub-systems that must cooperate. In other words, those sub-systems must communicate with each other and to do this, still fullling the overall system specfication, real-time communication must be supported. Moreover, real-time communication is also becoming widely needed in networks like the Internet, spanning over large distances. In for example Internet, the support for different traffic classes is often described as supporting different QoS (Quality of Service) levels and does normally include some kind of specifcation to meet real-time demands. Real-time communication often relies on some kind of scheduling like EDF (Earliest Deadline First), but there are some important differences compared to standard single-processor scheduling. First, the transmission of a packet is, in most cases, non-preemptive. The ongoing transmission, and possibly also some of the already queued messages, can then not be interrupted when a more important message (e.g., with a shorter relative deadline) arrives or is generated. Moreover, a network, instead of a single link, makes the situation much more complex and one must consider things like medium access method, topology, multiple users on multiple nodes, non-deterministic access delay etc.

More and more real-time systems are complex and distributed systems consisting of many sub-systems that must cooperate. In other words, those sub-systems must communicate with each other and to do this, still fullling the overall system specfication, real-time communication must be supported. Moreover, real-time communication is also becoming widely needed in networks like the Internet, spanning over large distances. In for example Internet, the support for different traffic classes is often described as supporting different QoS (Quality of Service) levels and does normally include some kind of specifcation to meet real-time demands. Real-time communication often relies on some kind of scheduling like EDF (Earliest Deadline First), but there are some important differences compared to standard single-processor scheduling. First, the transmission of a packet is, in most cases, non-preemptive. The ongoing transmission, and possibly also some of the already queued messages, can then not be interrupted when a more important message (e.g., with a shorter relative deadline) arrives or is generated. Moreover, a network, instead of a single link, makes the situation much more complex and one must consider things like medium access method, topology, multiple users on multiple nodes, non-deterministic access delay etc.

More and more real-time systems are complex and distributed systems consisting of many sub-systems that must cooperate. In other words, those sub-systems must communicate with each other and to do this, still fullling the overall system specfication, real-time communication must be supported. Moreover, real-time communication is also becoming widely needed in networks like the Internet, spanning over large distances. In for example Internet, the support for different traffic classes is often described as supporting different QoS (Quality of Service) levels and does normally include some kind of specifcation to meet real-time demands. Real-time communication often relies on some kind of scheduling like EDF (Earliest Deadline First), but there are some important differences compared to standard single-processor scheduling. First, the transmission of a packet is, in most cases, non-preemptive. The ongoing transmission, and possibly also some of the already queued messages, can then not be interrupted when a more important message (e.g., with a shorter relative deadline) arrives or is generated. Moreover, a network, instead of a single link, makes the situation much more complex and one must consider things like medium access method, topology, multiple users on multiple nodes, non-deterministic access delay etc.

More and more real-time systems are complex and distributed systems consisting of many sub-systems that must cooperate. In other words, those sub-systems must communicate with each other and to do this, still fullling the overall system specfication, real-time communication must be supported. Moreover, real-time communication is also becoming widely needed in networks like the Internet, spanning over large distances. In for example Internet, the support for different traffic classes is often described as supporting different QoS (Quality of Service) levels and does normally include some kind of specifcation to meet real-time demands. Real-time communication often relies on some kind of scheduling like EDF (Earliest Deadline First), but there are some important differences compared to standard single-processor scheduling. First, the transmission of a packet is, in most cases, non-preemptive. The ongoing transmission, and possibly also some of the already queued messages, can then not be interrupted when a more important message (e.g., with a shorter relative deadline) arrives or is generated. Moreover, a network, instead of a single link, makes the situation much more complex and one must consider things like medium access method, topology, multiple users on multiple nodes, non-deterministic access delay etc.

More and more real-time systems are complex and distributed systems consisting of many sub-systems that must cooperate. In other words, those sub-systems must communicate with each other and to do this, still fullling the overall system specfication, real-time communication must be supported. Moreover, real-time communication is also becoming widely needed in networks like the Internet, spanning over large distances. In for example Internet, the support for different traffic classes is often described as supporting different QoS (Quality of Service) levels and does normally include some kind of specifcation to meet real-time demands. Real-time communication often relies on some kind of scheduling like EDF (Earliest Deadline First), but there are some important differences compared to standard single-processor scheduling. First, the transmission of a packet is, in most cases, non-preemptive. The ongoing transmission, and possibly also some of the already queued messages, can then not be interrupted when a more important message (e.g., with a shorter relative deadline) arrives or is generated. Moreover, a network, instead of a single link, makes the situation much more complex and one must consider things like medium access method, topology, multiple users on multiple nodes, non-deterministic access delay etc.

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.

Parallel and distributed computing systems become more and more powerful and hence place increasingly higher demands on the networks that interconnect their processors or processing nodes. Many of the applications running on such systems, especially embedded systems applications, have real-time requirements and, with increasing application demands, high-performance networks are the hearts of these systems. Fiber-optic networks are good candidates for use in such systems in the future. This thesis contributes to the relatively unexplored area of fiber-optic networks for parallel and distributed real-time computer systems and suggests and evaluates several fiber-optic networks and protocols. Two different technologies are used in the networks, WDM (Wavelength Division Multiplexing) and fiber-ribbon point-to-point links. WDM offers multiple channels, each with a capacity of several Gbit/s. A WDM star network in which protocols and services are efficiently integrated to support different kinds of real-time demands, especially hard ones, has been developed. The star-of-stars topology can be chosen to offer better network scalability. The WDM star architecture is attractive but its future success depends on components becoming more commercially mature. Fiber-ribbon links, offering instead an aggregated bandwidth of several Gbit/s, have already reached the market with a promising price/performance ratio. This has motivated the development and investigation of two new ring networks based on fiber-ribbon links. The networks take advantage of spatial bandwidth reuse, which can greatly enhance performance in applications with a significant amount of nearest downstream neighbor communication. One of the ring networks is control channel based and not only has support for real-time services like the WDM star network but also low level support for, e.g., group communication. The approach has been to develop network protocols with support for dynamic real-time services, out of tim, Technical report / School of Electrical and Computer Engineering, Chalmers University of Technology, Göteborg, Sweden, 0282-5406 ; 379

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.

In this paper, we present how real-time services are implemented in a control-channel based ring network built up of fiber-ribbon point-to-point links. Services for best effort messages, guarantee seeking messages and real-time virtual channels are supported for single destination, multicast and broadcast transmission by the network. Slot-reservation is used for the implementation of real-time virtual channels. High aggregated throughput can be achieved due to pipelining, i.e., data can be transmitted simultaneously in different segments of the ring. An analysis of worst-case latency and deterministic throughput, which are important measures for real-time service implementation, is provided. The network is analyzed for two variants of time-slot organization, one that offers higher throughput and one that offers lower latency in some situations. We also show how the network offers low-level support for parallel computing, i.e., barrier-synchronization and global reduction. The control channel is used when realizing these functions, which implies no modification of the original network architecture. Low-level support for reliable transmission is also offered in a similar manner. This includes acknowledge / negative acknowledge and flow-control.