13339216
A mobile service platform using proxy technology
This paper proposes iMobile, a proxy-based platform for developing mobile services for various mobile devices and wireless access technologies. iMobile acts as a message gateway that allows mobile devices to relay messages to each other through various protocols on different access networks. It allows mobile devices to access internet services, corporate databases and to control various network devices. iMobile implements three key abstractions: dev-let, info-let and app-let. An info-let provides abstract view of information space. An app-let implements service or application logic by processing information from various info-lets. A dev-let receives and sends messages through any particular protocols for mobile devices. The let engine supports user and device profiles for personalization and transcoding, and invokes proper app-lets and info-lets to answer requests from a dev-let. The iMobile modular architecture allows developers to write device drivers, information access methods and application logic independently from each other. Copyright © 2005 John Wiley & Sons, Ltd.
15619003
A Graphical User Interface Design for Network Simulation
Abstract This article describes a prototyping effort of a flexible graphical user interface (GUI) for a simulation tool called COPS. The GUI is designed to allow parameter setup for all modules in simulation model, and can be easily replaced by new GUIs implemented in different languages/graphical tools. This article provides design guidelines and implementation details of the flexible GUI.
2805042
A new random walk model for PCS networks
This paper proposes a new approach to simplify the two-dimensional random walk models capturing the movement of mobile users in personal communications services (PCS) networks. Analytical models are proposed for the new random walks. For a PCS network with hexagonal configuration, our approach reduces the states of the two-dimensional random walk from (3n/sup 2/+3n-5) to n(n+1)/2, where n is the layers of a cluster. For a mesh configuration, our approach reduces the states from (2n2-2n+1) to (n/sup 2/+2n+4)/4 if n is even and to (n/sup 2/+2n+5)/4 if n is odd. Simulation experiments are conducted to validate the analytical models. The results indicate that the errors between the analytical and simulation models are within 1%. Three applications (i.e., microcell/macrocell configuration, distance-based location update, and GPRS mobility management for data routing) are used to show how our new model can be used to investigate the performance of PCS networks.
16848330
A flexible graphical user interface for performance modeling
We identify three goals for the graphical user interface (GUI) of a network simulation environment: user friendliness, model re-usability, and application extensibility. We address the user friendliness issue by proposing a simple yet efficient approach to setup parameters for the simulation models. We address the application extensibility issue by a two-layer GUI architecture. The two layers are loosely-coupled, and the first layer can be easily replaced (without affecting the other components of the simulation environment). We address the model re-usability issue by subnetworks. Unlike most existing simulation packages where subnetwork is simply a method to group the nodes, the subnetwork construct in our approach is an integral part of the simulation environment (i.e., all operations for a basic node also apply to a subnetwork). The port concept is used to explicitly define the I/O relationship between a subnetwork and the outside world. Parameter dialog boxes are used to set up the parameters for a subnetwork conveniently. Finally, a simple stack mechanism is proposed to measure subnetwork-wide output statistics.<<ETX>>
5110930
A comparison study of the two-tier and the single-tier personal communications services systems
A two-tier PCS system integrates the high tier PCS system and the low tier PCS systems into a single system to provide the advantages of both tiers. Such a system is expected to provide better service (more available and more cost effective to the users) at the expense of the extra tier switching management. We compare the performance of the two-tier PCS system and the single low tier system in two aspects: the registration traffic and the service availability. Because of the tier management, the two-tier system generates more registration traffic than the single low tier system. Under the range of the input parameters in our study, we show that the two-tier system generates less than 10% extra registration traffic than the single low tier system in most cases and generates less than 20% registration traffic in the worst cases. It is clear that for the service availability, the two-tier system is better than the single one tier system. We also study the probability that a call is forced terminated in the single low tier system because the low tier becomes unavailable during the call (such a call can be continued in the two-tier system).
16744149
Performance Analysis for Dual Band PCS Networks
In a dual band personal communications services (PCS) network, heavy traffic areas are covered by microcells which overlay macrocells. In such a network, microcells and macrocells utilize different frequency bands. We propose an analytic model to study the performance of a dual band PCS architecture. Our model assumes that a PCS subscriber has a general residence time distribution in a microcell and the macrocell residence time distribution is derived from the microcell residence time distribution. An iterative algorithm is used to compute the overflow traffic from a microcell to its overlaid macrocell. Then, the call incompletion probability is computed by a macrocell model based on the overflow traffic. Our study indicates that the variance of the microcell residence time distribution and the number of microcells covered by a macrocell have significant effects on the call incompletion probability.
14394566
Integration, verification and layout of a complex multimedia SOC
We present our experience of designing a single-chip controller for an advanced digital still camera from specification all the way to mass production. The process involves collaboration with camera system designer, IP vendors, EDA vendors, silicon wafer foundry, package and testing houses, and camera maker. We also co-work with academic research groups to develop a JPEG codec IP and memory BIST and SOC testing methodology. We cover the problems encountered, our solutions, and lessons learned.
43480564
PLS: a scheduler for pipeline synthesis
The authors point out that pipelining is an effective method for optimizing the execution of a loop, especially for digital signal processing (DSP) applications where data enter a circuit regularly. Although throughput and turnaround time are two important optimization criteria, previous work emphasized mainly the throughput. It is shown that the delay time for executing an iteration of a loop has a strong relationship to the cost of the registers and the controller. By minimizing the delay, there is more silicon area to allocate to additional resources, which in turn increases throughput. Forward scheduling and a backward scheduling are iteratively used to achieve this purpose. The algorithm, called PipeLining Scheduler or PLS, can be used to pipeline a loop with or without loop-carried dependencies. Real examples are used to illustrate the method. Experiments on benchmark examples show that considerable improvement over previous approaches is attained. >
13768633
Software Defined Radio - A High Performance Embedded Challenge
Wireless communication is one of the most computationally demanding workloads. It is performed by mobile terminals (“cell phones”) and must be accomplished by a small battery powered system. An important goal of the wireless industry is to develop hardware platforms that can support multiple protocols implemented in software (software defined radio) to support seamless end-user service over a variety of wireless networks. An equally important goal is to provide higher and higher data rates. This paper focuses on a study of the wideband code division multiple access protocol, which is one of the dominant third generation wireless standards. We have chosen it as a representative protocol. We provide a detailed analysis of computation and processing requirements of the core algorithms along with the interactions between the components. The goal of this paper is to describe the computational characteristics of this protocol to the computer architecture community, and to provide a high-level analysis of the architectural implications to illustrate one of the protocols that would need to be accommodated in a programmable platform for software defined radio. The computation demands and power limitations of approximately 60 Gops and 100~300 mW, place extremely challenging goals on such a system. Several of the key features of wideband code division multiple access protocol that can be exploited in the architecture include high degrees of vector and task parallelism, small memory footprints for both data and instructions, limited need for complex arithmetic functions such as multiplication, and a highly variable processing load that provides the opportunity to dynamically scale voltage and frequency.
18540245
Array allocation taking into account SDRAM characteristics
Multimedia, image processing and other signal processing applications often involve data stored in large arrays. Due to chip area limitation, arrays are typically assigned to off-chip memories, such as DRAM. This being the case, we try to optimize off-chip memory accesses to improve performance. We take the characteristics of the current mainstream SDRAM memory into account. We propose an algorithm to allocate arrays to different banks to increase the probability of utilizing SDRAM's multi-bank characteristic. Experimental results show significant improvement over traditional approaches.
13450793
On IEEE 802.14 medium access control protocol
In this article we present a comprehensive survey on the architecture, protocol issues, and standard of the hybrid fiber coaxial (HFC) networks which are evolving from the existing residential CATV networks. We first describe the HFC architecture and discuss the problems in providing two-way communication. Then, we identify three important medium access control (MAC) issues in designing the IEEE 802.14 standard; namely, synchronization, upstream channel access modes, and collision resolution. Resolutions adopted by the IEEE 802.14 Committee are illustrated after giving a protocol overview. Key resolutions include compensating round trip correction (RTC), interleaving minislots of data and request concurrently, and resolving collisions by multiple collision resolution engines, using the n-ary tree plus p-persistence algorithm with a first transmission rule. A comparative summary of some draft proposals that lead to the standard is given. Finally, we pinpoint two headend algorithms, minislot allocation and request scheduling, which are left open in the standard. They do not affect interoperability but may have a critical impact on performance.