Showing papers by "Kenneth Steiglitz published in 1995"

Optimization of wireless resources for personal communications mobility tracking

Abstract: In personal communications applications, users communicate via wireless with a wireline network. The wireline network tracks the current location of the user, and can therefore route messages to a user regardless of the user's location. In addition to its impact on signaling within the wireline network, mobility tracking requires the expenditure of wireless resources as well, including the power consumption of the portable units carried by the users and the radio bandwidth used for registration and paging. Ideally, the mobility tracking scheme used for each user should depend on the user's call and mobility pattern, so the standard approach, in which all cells in a registration area are paged when a call arrives, may be wasteful of wireless resources. In order to conserve these resources, the network must have the capability to page selectively within a registration area, and the user must announce his or her location more frequently. We propose and analyze a simple model that captures this additional flexibility. Dynamic programming is used to determine an optimal announcing strategy for each user. Numerical results for a simple one-dimensional mobility model show that the optimal scheme may provide significant savings when compared to the standard approach even when the latter is optimized by suitably choosing the registration area size on a per-user basis. Ongoing research includes computing numerical results for more complicated mobility models and determining how existing system designs might be modified to incorporate our approach.

Usage-based pricing of packet data generated by a heterogeneous user population

Abstract: Usage-based pricing of offered traffic to a data network can be an effective technique for congestion control. To gain insight into the benefits usage-based pricing offers, the authors propose and study a simple model in which many users wish to transmit packets to a single-server queue. Based on the announced price per packet and the available quality of service (QoS) (e.g., mean delay), each user independently decides whether or not to transmit. Given statistical assumptions about the incoming traffic streams and the QoS as a function of offered load, the equilibrium relationship between price and QoS is determined by a fixed-point equation. The relationships among price, QoS, revenue, and server capacity are illustrated numerically, assuming a particular type of random user population. These examples indicate that adjusting the price to maximize revenue results in an efficient use of service capacity with an associated small mean delay.

Implementation of parallel arithmetic in a cellular automaton

Abstract: We describe an approach to parallel computation using particle propagation and collisions in a one-dimensional cellular automaton using a Particle model-a Particle Machine (PM). Such a machine has the parallelism, structural regularity, and local connectivity of systolic arrays, but is general and programmable. It contains no explicit multipliers, adders, or other fixed arithmetic operations; these are implemented using fine-grain interactions of logical particles which are injected into the medium of the cellular automaton, and which represent both data and processors. We give parallel, linear-time implementations of addition, subtraction, multiplication and division.

Discrete-time signal design for maximizing separation in amplitude

Abstract: Given a discrete-time, linear, shift-invariant channel with finite impulse response, the problem of designing finite-length input signals with bounded amplitude (l/sub /spl infin// norm) such that the corresponding output signals are maximally separated in amplitude (l/sub /spl infin// sense) is considered. In general, this is a nonconvex optimization problem, and appears to be computationally difficult. An optimization algorithm that seems to perform well is described. Optimized signal sets and associated minimum distances (minimum l/sub /spl infin// separation between two distinct channel outputs) are presented for some example impulse responses. A conjectured upper bound on the minimum distance is given that is easily computed given the impulse response of the channel, the number of inputs, and the input length. This upper bound is shown to be valid for a limited class of impulse response functions. >

A comparison study of heuristics for mapping parallel algorithms to message-passing multiprocessors

Abstract: This paper presents a comparison study of popular clustering and mapping heuristics which are used to map task-flow graphs to message-passing multiprocessors. Tb this end, we use task-graphs which arc representative of important scientific algorithms running on data-sets of practical interest. The annotation which assigns weights to nodes and edges of the task-graphs is realistic It reflects current trends in processor, communication channel, and message-passing interface technology and takes into consideration hardware characteristics of state-of-the-art multiprocessors. Our experiments show that applying realistic models for task-graph annotation affects the effectiveness and functionality of clustering and mapping techniques. Therefore, new heuristics are necessary that will take into account more practical models of communication costs. We present modifications to existing clustering and mapping algorithms which improve their efficiency and running-time for the practical models adopted.

EIN: A Signal Processing Scratchpad

Abstract: Computer systems designed for music synthesis usually encapsulate signal-processing algorithms as macros or functions, and thus provide a modular interface which facilitates the development of complex structures. This is the thinking behind Mathews’ original concept of the ‘‘unit generator’’ (Mathews 1969) and most subsequent software synthesis languages use this approach. While it has proven to be an effective method it has not generally provided a means by which the users of these systems, often more musically prepared than wise in the ways of digital signal processing, can gain an intuitive understanding of the mechanisms used to modify and create digital signals. Indeed, there is little conceptual difference between patching a signal through a bank of two-pole resonating filters/unit generators and tweaking the sliders on a graphic equalizer. EIN is an attempt to provide an interface in which the user has direct control over every add, multiply and store applied to each sample, and can gain a more direct understanding of the machinery of digital signal processing. While its main use has been instructional, it also provides a way to experiment with digital filters and design more complex instruments and algorithms. It is, in effect, a kind of low-level circuit design kit for signal processing. EIN Syntax EIN provides the routine machinery for calling the user’s code, executing it, writing the resulting output sound samples to a file, playing the file, and displaying and analyzing it in the time and frequency domains. The user provides a script in a language that is a superset of C. The EIN system then compiles it and provides a wrapper that calls the script for each time sample from t = 0 up to the specifiednumber of samples, nsamps; computes the next output sample y (for the mono case), or the variables left and right (for the stereo case); and writes the output samples to an output sound file,formated for the sampling rate of sr samples/sec. The int variables t and nsamps, and the float variables y, left, right, and sr, are reserved by EIN, and should not be used for other purposes. The mono/stereo option, and the values of sr and nsamps are selected with radio buttons on the interface. The remaining reserved names are described in Appendix 3. As an example, here is a one-line EIN script that produces a sine wave at 440 Hz: