β-bit serial/parallel multipliers

A generalized -bit least-significant-digit (LSD) first, serial/parallel multiplier architecture is presented with 1n wheren is the operand size. The multiplier processes both the serial input operand and the double precision product -bits per clock cycle in an LSD first, synchronous fashion. The complete two's complement double precision product requires 2n/ clock cycles. This generalized architecture creates a continuum of multipliers between traditional bit-serial/parallel multipliers (=1) and fully-parallel multipliers (=n). -bit serial/parallel multipliers allow anoptimized integrated circuit arithmetic to be designed based on a particular application's area, power, throughput, latency, and numerical precision constraints.This project was pratically funded by the UCSD-NSF I/UCR Center on Ultra-High Speed Intergrated Circuits and Systems.     

On the design of feedback controllers to achieve prescribed initial value constraints

The problem of designing a stabilizing compensator for a control system to achieve prescribed initial value constraints ⁽ⁱ⁾(0⁺)=y_i is considered. Indeed, modulo certain technical conditions, such a compensator exists if and only if y_i=0;i= 0,1,...,rp +rt –2; whererp is the relative degree of the plant andrt is the relative degree of the system input. This theorem is derived and a complete parameterization of the set of compensators that achieve the prescribed design constraints is formulated.This research was supported in part by NSF Grant No. 921106.     

A general purpose proxy filtering mechanism applied to the mobile environment

Host mobility complicates the standard networking model in unexpected ways. It increases network heterogeneity, causing difficulty within applications that expect a high or constant amount of network bandwidth. Mobility increases cost when a user switches from a relatively inexpensive high bandwidth network to a low bandwidth paybycall or paybybyte network. Mobility may also reduce security when a user moves from a safe network onto a foreign one. This situation can be improved by introducing a proxy between the mobile client and its peer. The purpose of this intermediary is to process data moving between the client and peer. The type of processing performed depends on the desired result: the proxy can hide network heterogeneity via data filtering, reduce cost by using compression, and increase security through the use of secure protocols between the client and proxy. This paper presents a general purpose proxy system and how it has been applied to the mobile environment. The overall architecture is described, examples of its use given, and a study on its feasibility and performance is presented.     

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.     

Personal Imaging and lookpainting as tools for personal documentary and investigative photojournalism

A means and apparatus for covert capture of extremely highresolution photorealistic images is presented. The apparatus embodies a new form of userinterface – instead of the traditional point and click metaphor which was thought to be the simplest photography had to offer, what is proposed is a look metaphor in which images are generated through the natural process of looking around, in a manner that does not require conscious thought or effort. These lookpaintings become photographic/videographic memories that may, at times, exceed the quality attainable with even large and cumbersome professional photographic film cameras, yet they may be captured through a device that resembles ordinary sunglasses. The method is based on longterm psychophysical adaptation using a covert sunglassbased realitymediating apparatus, together with two new results in image processing. The first new result is a means of estimating the true projective coordinate transformation between successive pairs of images, and the second is that of estimating, to within a single unknown scalar constant, the quantity of light arriving at the image plane. Furthermore, what is captured is more than just a picture. The resulting environment map may be explored by one or more remote participants who may also correspond and interact with the wearer during the actual shooting process, giving rise to computer supported collaborative (collective) photography, videography, shared photographic/videographic memory, etc.     

Systematic Width-and-Length Dependent CMOS Transistor Mismatch Characterization and Simulation

This paper presents a methodology for characterizing the random component of transistor mismatch in CMOS technologies. The methodology is based on the design of a special purpose chip which allows automatic characterization of arrays of NMOS and PMOS transistors of different sizes. Up to 30 different transistor sizes were implemented in the same chip, with varying transistors width W and length L. A simple strong inversion large signal transistor model is considered, and a new five parameters MOS mismatch model is introduced. The current mismatch between two identical transistors is characterized by the mismatch in their respective current gain factors /, V _TO threshold voltages , bulk threshold parameters , and two components for the mobility degradation parameter mismatch ₀ and _e. These two components modulate the mismatch contribution differently, depending on whether the transistors are biased in ohmic or in saturation region. Using this five parameter mismatch model, an extraordinary fit between experimental and computed mismatch is obtained, including minimum length (1 m) transistors for both ohmic and saturation regions. Standard deviations for these five parameters are obtained as well as their respective correlation coefficients, and are fitted to two dimensional surfaces f(W, L) so that their values can be predicted as a function of transistor sizes. These functions are used in an electrical circuit simulator (Hspice) to predict transistor mismatch. Measured and simulated data are in excellent agreement.     

A Markov modulated fluid queueing system with strict priority

We investigate a Markov modulated fluid queueing system with strict priority. The input process is composed of two fluid flows which are stored in buffer1 and buffer2, respectively. The rates of these fluid flows depend on the current state of a finite state Markov chain. Buffer1 has full assignment of priority (=strict priority) for service and so buffer2 is served at a residual service rate when buffer1 is empty. We explicitly derive the stationary joint distribution of the two buffer contents in the system by a spectral decomposition method. In the case of a twostate Markov chain, the joint distribution is explicitly expressed in terms of the system parameters. Also the joint moments and tail distributions of the two buffer contents are obtained and some numerical examples are presented.     

The Complex Bootstrap Algorithm for Blind Separation of QAM Multiuser CDMA Signals

The bootstrap separator for multiuser signals is principally composed of cancelers, each one using the output of the other cancelers to facilitate control of its adaptive weight. In fact, such a structure performs as a signal separator rather than an interference canceler. Since for its separation there is no need for a reference signal (as in LMS cancelers), it is sometimes justifiably called a Blind Separator. However, for its operation the bootstrap separator requires a signal distinguisher termed discriminator. The algorithm was used in the past in applications such as dually polarized satellite communications and microwave terrestrial links. It was particularly reported for multiuser CDMA signal separating, with the signum function as discriminator. Especially for QAM signals, complex presentation is important. Therefore, we will concentrate in this report on what we call the Complex Bootstrap Algorithm. It is an extension to the previously reported bootstrap structure of [5]. We will examine its performance and emphasize the hardware saving in its implementation, and the ease of using it in 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.     

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.     

Tree multicast strategies in mobile,multihop wireless networks

Tree multicast is a well established concept in wired networks. Two versions, persource tree multicast (e.g., DVMRP) and shared tree multicast (e.g., Core Based Tree), account for the majority of the wireline implementations. In this paper, we extend the tree multicast concept to wireless, mobile, multihop networks for applications ranging from ad hoc networking to disaster recovery and battlefield. The main challenge in wireless, mobile networks is the rapidly changing environment. We address this issue in our design by: (a) using soft state (b) assigning different roles to nodes depending on their mobility (2level mobility model); (c) proposing an adaptive scheme which combines shared tree and persource tree benefits, and (d) dynamically relocating the shared tree Rendezvous Point (RP). A detailed wireless simulation model is used to evaluate various multicast schemes. The results show that persource trees perform better in heavy loads because of the more efficient traffic distribution; while shared trees are more robust to mobility and are more scalable to large network sizes. The adaptive tree multicast scheme, a hybrid between shared tree and persource tree, combines the advantages of both and performs consistently well across all load and mobility scenarios. The main contributions of this study are: the use of a 2level mobility model to improve the stability of the shared tree, the development of a hybrid, adaptive persource and shared tree scheme, and the dynamic relocation of the RP in the shared tree.     

Predictive Caching Strategy for On-Demand Routing Protocols in Wireless Ad Hoc Networks

Route caching strategy is important in on-demand routing protocols in wireless ad hoc networks. While high routing overhead usually has a significant performance impact in low bandwidth wireless networks, a good route caching strategy can reduce routing overheads by making use of the available route information more efficiently. In this paper, we first study the effects of two cache schemes, link cache and path cache, on the performance of on-demand routing protocols through simulations based on the Dynamic Source Routing (DSR) protocol. Since the path cache DSR has been extensively studied, we focus in this paper on the link cache DSR in combination with timer-based stale link expiry mechanisms. The effects of different link lifetime values on the performance of routing protocol in terms of routing overhead, packet delivery ratio and packet latency are investigated. A caching strategy incorporating adaptive link timeout is then proposed, which aims at tracking the optimal link lifetime under various node mobility levels by adaptively adjusting the link lifetime based on the real link lifetime statistics. The performance of the proposed strategy is then compared with the conventional path cache DSR. The results show that without a timeout mechanism, a link cache scheme may suffer severe performance degradation due to the use of broken routes, while the proposed adaptive link cache strategy achieves significantly improved performance by reducing the routing overhead when the network traffic load is high.     

On the structure of the privacy hierarchy

An N argument function f(x ₁,...,x _N ) is called t-private if a protocol for computing f exists so that no coalition of at most t parties can infer any additional information from the execution, other than the value of the function. The motivation of this work is to understand what levels of privacy are attainable. So far, only two levels of privacy are known for N argument functions which are defined over finite domains: functions that are N-private and functions that are (N – 1)/2-private but not N/2-private.In this work we show that the privacy hierarchy for N-argument functions which are defined over finite domains, has exactly (N + 1)/2 levels. We prove this by constructing, for any N/2 t N – 2, an N-argument function which is t-private but not (t + 1)-private.This research was supported by US-Israel Binational Science Foundation Grant 88-00282.     

Scheduling and bandwidth allocation for the distribution of archived video in VOD systems

Providing costeffective videoondemand (VOD) services necessitates reducing the required bandwidth for transporting video over highspeed networks. In this paper, we investigate efficient schemes for transporting archived MPEGcoded video over a VOD distribution network. A video stream is characterized by a timevarying traffic envelope, which provides an upper bound on the bit rate. Using such envelopes, we show that video streams can be scheduled for transmission over the network such that the perstream allocated bandwidth is significantly less than the source peak rate. In a previous work [13], we investigated stream scheduling and bandwidth allocation using global traffic envelopes and homogeneous streams. In this paper, we generalize the scheduling scheme in [13] to include the heterogeneous case. We then investigate the allocation problem under windowbased traffic envelopes, which provide tight bounds on the bit rate. Using such envelopes, we introduce three streamscheduling schemes for multiplexing video connections at a server. The performance of these schemes is evaluated under static and dynamic scenarios. Our results indicate a significant reduction in the perstream allocated bandwidth when stream scheduling is used. While this reduction is obtained through statistical multiplexing, the transported streams are guaranteed stringent, deterministic quality of service (i.e., zero loss rate and small, bounded delay). In contrast to video smoothing, our approach requires virtually no buffer at the settop box since frames are delivered at their playback rate.     

Why ‘Current Mode’ Does Not Guarantee Good Performance

It is often said that there is a fundamental difference between current-mode and voltage-mode circuits. This conjecture is discussed in technical and philosophical terms, and it is shown that there is no such performance difference to be found, and that it is not possible to make a clear divide between voltage mode and current mode.And yet performance differences appear in the literature. It is shown that they come from the different design practices of the current-mode and the voltage-mode research groups. The conclusion of this paper is that the practical knowledge of the current-mode research groups should be re-integrated into main-stream IC design, and that all propaganda of the type current-mode is better than voltage-mode should be stopped immediately.     

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.     

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.     

The effects of controlling capture on multimedia traffic for shared Ethernet systems

The IEEE 802.3 Ethernet standard is evolving to support much higher data rates and improved quality of service. Even low cost halfduplex CSMA/CD networks can be improved using an enhanced backwardscompatible collision arbitration algorithm known as the Binary Logarithmic Arbitration Method (BLAM) now being proposed as the IEEE 802.3w draft standard. BLAM is designed to coexist fairly with the existing Binary Exponential Backoff (BEB) algorithm, while eliminating its shortterm unfairness problems. In this paper, we focus on how BLAM improves Ethernet performance for multimedia data transport. Analytical, simulation, and prototype hardware experimental results using synthetic, trace, and actual measured traffic are presented. It is shown that BLAM Ethernets can support significantly greater numbers of video streams than existing BEB Ethernets and if the delivery requirements for the video traffic are not too strict, that BLAM Ethernets can even support video if the network is completely saturated with data traffic.     

Symmetry relations in multidimensional Fourier transform pairs

A relation between the types of symmetries that exist in signal and Fourier transform domain representations is derived for continuous as well as discrete domain signals. The symmetry is expressed by a set of parameters, and the relations derived in this paper will help to find the parameters of a symmetry in the signal or transform domain resulting from a given symmetry in the transform or signal domain respectively. A duality among the relations governing the conversion of the parameters of symmetry in the two domains is also brought to light. The application of the relations is illustrated by a number of two-dimensional examples.Notation R the set of real numbers - R ^m R × R × ... × R m-dimensional real vector space - continuous domain real vector - L {¦ – _i , i = 1,2,..., m} - m-dimensional frequency vector - W { – _i ,i=1,2,..., m} - m-dimensional normalized frequency vector - _P {¦ – _i , i=1,2,...,m} - g(ol) g (₁,₂,..., _m ) continuous domain signal - () ( _{1 2},..., _m )=G (j ₁,j ₂,..., j _m ) Fourier transform ofg (ol) - (A,b,,,) parameters ofT- symmetry - N the set of integers - N ^m N × N × ... × N m-dimensional integer vector spacem-dimensional lattice - h(n) h (n ₁,.,n _m ) discrete domain signal - H() Fourier transform ofh (n) - v ₁,v ₂,..., v_m m sample-direction and interval vectors - V (v ₁ v ₂ ...v _m ) sampling basis matrix - [x]^* complex conjugate ofx - detA determinant ofA - X {x¦ – x _i , i=1,2,..., m} - A ^–t [A ^–1] ^t ,t stands for transpose This work was supported in part by the Natural Sciences and Engineering Research Council of Canada under Grant A-7739 to M. N. S. Swamy and in part by Tennessee Technological University under its Faculty Research support program to P. K. Rajan.     

Incorporating QoS into IP Enterprise Network Design

Recent trends in enterprise networks are radically changing the composition of these systems. Instead of having diverse data networks, each of which is dedicated to a single class of applications, corporations are moving to a unified IP (Internet Protocol) Intranet. Traffic demands on these Intranets include delay-sensitive traffic that requires better than the standard best effort service provided by IP networks. As a result, various new technologies and strategies to provide end-to-end Quality of Service (QoS) within IP enterprise networks are being developed and implemented. However, current IP network design methodologies are limited in that they can only design networks providing best effort service or else, a single delay constraint for all traffic. In this paper, we discuss a new design methodology for IP enterprise networks that takes into account the new technologies and techniques that can provide QoS. In particular, we identify and discuss the most crucial design issues that must be addressed when specialized queuing-based QoS strategies are used in the network. We describe the new constraints introduced by the underlying technologies and discuss how these factors affect the formulation of the IP Enterprise Network Design Problem. We then describe some specific features and methodologies that have been incorporated into a network design-planning tool for IP enterprise networks with QoS.