Traffic characterization algorithms for VBR video in multimedia networks

A network that offers deterministic, i.e., worst case, quality-of-service guarantees to variable-bit-rate (VBR) video must provide a resource reservation mechanism that allocates bandwidth, buffer space, and other resources for each video stream. Such a resource reservation scheme must be carefully designed, otherwise network resources are wasted. A key component for the design of a resource reservation scheme is the traffic characterization method that specifies the traffic arrivals on a video stream. The traffic characterization should accurately describe the actual arrivals, so that a large number of streams can be supported; but it must also map directly into efficient traffic-policing mechanisms that monitor arrivals on each stream. In this study, we present a fast and accurate traffic characterization method for stored VBR video in networks with a deterministic service. We use this approximation to obtain a traffic characterization that can be efficiently policed by a small number of leaky buckets. We present a case study where we apply our characterization method to networks that employ a dynamic resource reservation scheme with renegotiation. We use traces from a set of 25–30-min MPEG sequences to evaluate our method against other characterization schemes from the literature.     

Deterministic delay bounds for VBR video in packet-switchingnetworks: fundamental limits and practical trade-offs

Compressed digital video is one of the most important traffic types in future integrated services networks. However, a network service that supports delay-sensitive video imposes many problems since compressed video sources are variable bit rate (VBR) with a high degree of burstiness. In this paper, we consider a network service that can provide deterministic guarantees on the minimum throughput and the maximum delay of VBR video traffic. A common belief is that due to the burstiness of VBR traffic, such a service will not be efficient and will necessarily result in low network utilization. We investigate the fundamental limits and trade-offs in providing deterministic performance guarantees to video and use a set of 10 to 30 min. long MPEG-compressed video traces for evaluation. Contrary to conventional wisdom, we are able to show that, in many cases, a deterministic service can be provided to video traffic while maintaining a reasonable level of network utilization. We first consider an ideal network environment that employs the most accurate deterministic, time-invariant video traffic characterizations, the optimal earliest-deadline-first packet schedulers, and exact admission control conditions. The utilization achievable in this situation provides the fundamental limits of a deterministic service. We then investigate the utilization limits in a network environment that takes into account practical constraints, such as the need for simple and efficient policing mechanisms, packet scheduling algorithms, and admission control tests     

Priority queue schedulers with approximate sorting inoutput-buffered switches

All recently proposed packet-scheduling algorithms for output-buffered switches that support quality-of-service (QoS) transmit packets in some priority order, e.g., according to deadlines, virtual finishing times, eligibility times, or other time stamps that are associated with a packet. Since maintaining a sorted priority queue introduces significant overhead, much emphasis on QoS scheduler design is put on methods to simplify the task of maintaining a priority queue. In this paper, we consider an approach that attempts to approximate a sorted priority queue at an output-buffered switch. The goal is to trade off less accurate sorting for lower computational overhead. Specifically, this paper presents a scheduler that approximates the sorted queue of an earliest-deadline-first (EDF) scheduler. The approximate scheduler is implemented using a set of prioritized first-in/first-out (FIFO) queues that are periodically relabeled. The scheduler can be efficiently implemented with a fixed number of pointer manipulations, thus enabling an implementation in hardware. Necessary and sufficient conditions for the worst-case delays of the scheduler with approximate sorting are presented. Numerical examples, including traces based on MPEG video, demonstrate that in realistic scenarios, scheduling with approximate sorting is a viable option     

Exact admission control for networks with a bounded delay service

To support the requirements for the transmission of continuous media, such as audio and video, multiservice packet-switching networks must provide service guarantees to connections, including guarantees on throughput, network delays, and network delay variations. For the most demanding applications, the network must offer a service which provides deterministically bounded delay guarantees, referred to as “bounded delay service.” The admission control functions in a network with a bounded delay service require `schedulability conditions' that detect violations of delay guarantees in a network switch. Exact schedulability conditions are presented for three packet scheduling methods: earliest-deadline-first (EDF), static-priority (SP), and a novel scheduling method, referred to as rotating-priority-queues (RPQ). By characterizing the worst-case traffic with general subadditive functions, the presented schedulability conditions can be applied to a large class of traffic models. Examples, which include actual MPEG video traces, are presented to demonstrate the trade-offs involved in selecting a packet scheduling method for a bounded delay service     

Micro Handling Devices Supported by Electrostatic Forces

The handling of micro parts made of dielectric material can be affected by electrostatic forces. This work presents new handling devices taking advantage of electrostatic forces. These forces are generated by simple configurations of electrodes or by charges located on surfaces of insulators. High resolution force measurements show electrostatic effects such as gas discharges and leak currents. Active neutralization was applied by ionizers to discharge the handling devices and the parts to be handled. This method improved the process reliability significantly. Further, the influence of surface charges on the process reliability of pick and place operations of mechanical micro grippers was investigated.     

Micro bonding with non-viscous adhesives

The new subproject B8 “Adhesive processing in batch technology for the manufacturing of microsystems” has the goal to compile bases for batchable joining techniques based on adhesive systems. This paper presents an alternative adhesive bonding system, which is able to join very small parts as well as relatively big parts with high accuracy requirements. The main advantages are the possibility to apply small volumes, to pre-apply the adhesive with a temporarily delayed joining procedure and extremely short set cycles. Therefore, using hot melts can be a technologically and economically interesting alternative for the assembly and packaging of MEMS.