Recursive identification algorithms

Mechanisms for adapting models, filters, decisions, regulators, and so on to changing properties of a system or a signal are of fundamental importance in many modern signal processing and control algorithms. This contribution describes a basic foundation for developing and analyzing such algorithms. Special attention is paid to the rationale behind the different algorithms, thus distinguishing between optimal algorithms and ad hoc algorithms. We also outline the basic approaches to performance analysis of adaptive algorithms.     

Mobility Management for Hierarchical Wireless Networks

In this paper, we consider the mobility management in large, hierarchically organized multihop wireless networks. The examples of such networks range from battlefield networks, emergency disaster relief and law enforcement etc. We present a novel network addressing architecture to accommodate mobility using a Home Agent concept akin to mobile IP. We distinguish between the physical routing hierarchy (dictated by geographical relationships between nodes) and logical hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). The performance of the mobility management scheme is investigated through simulation.     

The discrete Einstein relation

In this paper the connection between massM, resistance and commute time for random walks on graphs is further explored, and the relation=2M · is proved. An extension of the result is made to multigraphs, which are an extension of the graph concept where a black box is treated like an edge.     

A necessary and sufficient condition for right coprime factorization of nonlinear feedback systems

In this short note, we establish a simple, yet precise, necessary and sufficient condition for the right coprime factorization of a nonlinear feedback control system. As a consequence, we also obtain similar conditions for the stable right coprime factorizations of the nonlinear feedback control system.     

Perspectives on Analytical Modeling of Small Geometry MOSFETs in SPICE for Low Voltage/Low Power CMOS Circuit Design

The present state of the art in analytical MOSFET modeling for SPICE circuit simulation is reviewed, with emphasis on the circuit design usage of these models. It is noted that the model formulation represents an upper limit of what is possible from any type of model, but that good parameter extraction is required to most closely approach that limit. The individual model types presently in common use are examined, with discussion of the behavior of each model, its strengths and weaknesses, its applicability to certain types of circuits, and criteria that a circuit design consumer can employ to judge a model before using it for circuit design. Some related issues, such as node charge and gate capacitance modeling, charge conservation, and statistical simulation of process variations, are also evaluated. Finally, new trends, directions, and requirements of MOSFET modeling for circuit simulation are considered.     

Systems which possessg- andh- Representations

Examples are given concerning the range of applicability of recent representation results that provide a means of studying the input-output properties of nonlinear systems in terms of the familiar impulse-response concept, and which extend the concept of integral transformation to nonlinear maps. We show that such representations, which we call g- and h-representations, exist for important classes of systems governed by nonlinear integral equations. In particular, it is proved that a large class of maps that have Volterra series representations also have these representations.     

Fault diagnosis in reconfigurable VLSI and WSI processor arrays

A systematic efficient fault diagnosis method for reconfigurable VLSI/WSI array architectures is presented. The basic idea is to utilize the output data path independence among a subset of processing elements (PEs) based on the topology of the array under test. The divide and conquer technique is applied to reduce the complexity of test application and enhance the controllability and observability of a processor array. The array under test is divided into nonoverlapping diagnosis blocks. Those PEs in the same diagnosis block can be diagnosed concurrently. The problem of finding diagnosis blocks is shown equivalent to a generalizedEight Queens problem. Three types of PEs and one type of switches, which are designed to be easily testable and reconfigurable, are used to show how to apply this approach. The main contribution of this paper is an efficient switch and link testing procedure, and a novel PE fault diagnosis approach which can speed up the testing by at leastO(V^1/2) for the processor arrays considered in this paper, where V is the number of PEs. The significance of our approach is the ability to detect as well as to locate multiple PE, switch, and link faults with little or no hardware overhead.     

Mobile ATM buffer capacity analysis

This paper extends a stochastic theory for buffer fill distribution for multiple on and off sources to a mobile environment. Queue fill distribution is described by a set of differential equations assuming sources alternate asynchronously between exponentially distributed periods in on and off states. This paper includes the probabilities that mobile sources have links to a given queue. The sources represent mobile user nodes, and the queue represents the capacity of a switch. This paper presents a method of analysis which uses mobile parameters such as speed, call rates per unit area, cell area, and call duration and determines queue fill distribution at the ATM cell level. The analytic results are compared with simulation results.This paper is partially funded by ARPA contract number J-FBI-94-223.The Mathematica code for this paper can be found on http://www.tisl.ukans.edu/sbush.     

Adaptive multicast routing in multirate loss networks

In this paper, we study two versions of the multicast routing problem in multirate loss networks: complete and partial. In the complete version of the multicast routing problem, the identities of all destination nodes are available to the multicast routing algorithm at once. Conversely, in the partial version of the multicast problem, the identities of the destination nodes are revealed to the routing algorithm one by one. Although the complete version of the multicast routing problem, also known as the Steiner tree problem, has been well studied in the literature, less attention has been paid for the definition of link costs and evaluating the performance of multicast routing algorithm from the network revenue point of view. Therefore, in this paper, we first propose two approaches, namely, the Markov Decision Processbased (MDPbased) and Least Loaded Routingbased (LLRbased) approaches, for defining link costs. Several heuristic multicast routing algorithms are then proposed for both fully connected networks and sparsely connected networks. We have also proposed a new performance metric, referred to as fractional reward loss, for evaluating the performance of multicast routing algorithms. Our simulation results indicate that algorithms based on partial destination information yield worse performance than those based on complete information. We also found that, for fully connected networks, algorithms that use LLRbased link costs yield very competitive performance as compared to those that use MDP approach. However, for sparsely connected networks, LLRbased algorithms yield significantly worse performance as compared to the MDPbased algorithms.     

Economics of “design for test” to remain competitive in the 90s

This article emphasizes the criticality of maximizing value adders and minimizing the costs of design for test (DFT) in order to remain competitive in ASIC manufacturing in the 90s.     

Floor acquisition multiple access (FAMA) in single‐channel wireless networks

The FAMANCS protocol is introduced for wireless LANs and adhoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMANCS (for floor acquisition multiple access with nonpersistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMANCS is based on a threeway handshake between sender and receiver in which the sender uses nonpersistent carrier sensing to transmit a requesttosend (RTS) and the receiver sends a cleartosend (CTS) that lasts much longer than the RTS to serve as a busy tone that forces all hidden nodes to back off long enough to allow a collisionfree data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collisionfree transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMANCS is analyzed for singlechannel networks with and without hidden terminals; the analysis shows that FAMANCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results.     

Building video‐on‐demand servers

We have designed and implemented a controllable software architecture for a VideoonDemand (VOD) server. With the proposed software architecture, many system design issues can be investigated. For example, we studied several disk striping schemes in the storage subsystem and examined the impact of the disk striping schemes on the utilization of system resources. In the processing component, we observed that additional concurrent video streams can be supported by using efficient memory interleaving. Buffering with a large memory space in the processing subsystem is a common technique to alleviate the latency variance of accessing different system components. By employing userlevel control and scheduling, the variance can be decreased thereby reducing the resulting buffer space needed for each video stream. In the network subsystem, we adopted a serverdriven approach for investigating MPEG2 video delivery over Asynchronous Transfer Mode (ATM) networks. The VOD server controls the pace of video transmission and reduces the complexity of the client. Since the client has limited buffer space (due to cost considerations), we have reduced the buffer requirement by regulating the transmission based on timing information embedded in the MPEG2 streams. Our research and experimental results are based on a VOD server which is currently under construction. The prototype server is based on an SGI sharedmemory multiprocessor with a mass storage system consisting of RAID3 disk arrays. Using 30 RAID3 disk arrays, preliminary experimental results show that the prototype server can potentially support more than 360 highquality video streams with careful design and coordination of the different system components.     

Some results on the invertibility of nonlinear operators

The objective of this paper is to present certain conditions guaranteeing invertibility of a nonlinear operator between normed linear spaces. The idea is to approximate the given operator by an invertible, possibly linear operator, and reduce the problem to the contraction mapping principle. Several theorems of this kind are given, which appear as generalizations of some early results by I.W. Sandberg, and estimates for an approximate inverse are established. Finally, introducing certain invertibility indices, further sufficient and necessary conditions for invertibility are given.     

Simulation‐based performance evaluation of routing protocols for mobile ad hoc networks

In this paper we evaluate several routing protocols for mobile, wireless, ad hoc networks via packetlevel simulations. The ad hoc networks are multihop wireless networks with dynamically changing network connectivity owing to mobility. The protocol suite includes several routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, endtoend delay, and routing load for a given traffic and mobility model. Both small (30 nodes) and medium sized (60 nodes) networks are used. It is observed that the new generation of ondemand routing protocols use much lower routing load, especially with small number of peertopeer conversations. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and endtoend delay performance.     

Microsystems Engineering: A Great Stride Forward in Microelectronics Technology

The development of new-generation technological and engineering concepts by the example of microsystems technology and microsystems engineering approaches is considered.     

Input-output systems whose transmission operators furnish nearly best approximations to a given map

Let {S(A):A A}, whereA is a subset of an infinite-dimensional normed linear spaceL, be a class of general nonlinear input-output systems that are governed by operator equations relating the input, state, and output, all of which are in extended spaces. IfQ is a given operator from a specified set ¯D _i, of inputs into the space of outputs ¯H ₀, the problem we consider is to find, for a given >0, a parameterA A such that the transmission operatorR(A ) ofS(A ) furnishes a nearly best (or -best) approximation toQ from allR(A),A A. Here the distance betweenQ andR(A) is defined as the supremum of distances betweenQz andR(A)z taken over allz ¯D _i. In Theorems 2 through 5 we show that ifS(A) is normal (Definition 2),A satisfies some mild requirement andL contains a fundamental sequence, then establishingA A reduces to minimizing a certain continuous functional on a compact subset ofR ⁿ, and thus can be carried out by conventional methods. The applications of results are illustrated by the example of a model-matching problem for a nonlinear system, and of optimal tracking.     

Routing with multiple QoS requirements for supporting multimedia applications

Distributed multimedia applications usually require multiple QoS performance guarantees. However, in general, searching such a route in the network, to support multimedia applications, is known to be NPcomplete. In this paper, we propose a new heuristic QoS routing algorithm, called QoSR_DKS, for supporting multimedia applications in highspeed networks. QoSR_DKS is a modification of rulebased Fallback routing and Dijkstra algorithms. It can search a unicast route that would have enough network resources so that multiple QoS requirements (bandwidth, delay, and delay jitter) of the requested flow could be guaranteed. Its worst case computation time complexity is the same as that of the Dijkstra algorithm, i.e., O(V²), where V is the number of nodes in the network. Extensive simulations were done with various network sizes, upto 500 nodes networks, where each node uses Weighted Fair Queueing (WFQ) service discipline. Results show that QoSR_DKS is very efficient. It could always find the QoS satisfying route, whenever there exists one (success rate is optimal), and its average computation time is near to simple shortest path Dijkstra algorithm.     

A scalable wireless virtual LAN

This paper presents a Wireless Virtual Local Area Network (WVLAN) to support mobility in IPoverATM local area networks. Mobility is handled by a joint ATMlayer handoff for connection rerouting and MAClayer handoff for location tracking, such that the effects of mobility are localized and transparent to the higherlayer protocols. Different functions, such as Address Resolution Protocol (ARP), mobile location, and ATM connection admission are combined to reduce protocol overhead and frontend delay for connectionless packet transmission in connectionoriented ATM networks. The proposed WVLAN, through the use of ATM technology, provides a scalable wireless virtual LAN solution for IP mobile hosts.     

NETMAN: The design of a collaborative wearable computer system

This paper presents a wearable groupware system designed to enhance the communication and cooperation of highly mobile network technicians. It provides technicians in the field with the capabilities for realtime audioconferencing, transmission of video images back to the office, and contextsensitive access to a shared notebook. An infrared locationtracking device allows for the automatic retrieval of notebook entries depending on the user's current location.