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).
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.
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.
26216894
Equal resource sharing scheduling for PCS data services
For high speed mobile communication applications, the data rate can be increased by using multiple channels (or time slots) instead of one channel. To reduce the high blocking rate of multiple channels assignment, flexible resource allocation strategies have been proposed. This paper proposes the Equal Resource Sharing Allocation scheme (ERSA scheme) for flexible resource allocation. The ERSA scheme dynamically averages the allocated resource to the call requests based on the number of calls in a base station. The scheme accommodates the maximum number of requests while providing acceptable quality to the admitted requests. We developed an analytic model to investigate the performance of ERSA, and conducted simulation experiments to validate the analytic model. We define satisfaction indication SI as the performance measurement of the resource allocation algorithm. The experiment results indicate that the ERSA scheme outperforms other resource allocation algorithms proposed in our previous study.
618071
iMail: a WAP mail retrieving system
This paper proposes iMail, a WAP mail retrieving system designed for wireless handheld devices to access Internet email service. In mobile data networks, the communication bandwidth is limited and the wireless handsets are constrained by small display, powerless CPU, limited memory, and unhandy input/output interface. To support mail retrieving in a mobile environment, we implement several features for iMail: mail filtering, two-phase fetch and pre-defined list reordering. Based on the user's filter options, mail filtering eliminates non-necessary mails sent to a wireless handheld device. Two-phase fetch is used to reduce transmission overhead of message delivery. We use pre-defined list reordering to speed up text typing in the wireless handheld devices. We also propose three mail notification mechanisms for iMail. When a new mail arrives, the mail notification mechanism informs iMail users immediately. Through the descriptions of the iMail features, this paper provides design and implementation guidelines for WAP applications.
28041902
Guest Editorial: Special Section on Wireless Internet
WIRELESS communications have made spectacular progress in recent years. In particular, the merge of various wireless communication systems and the Internet has become more critical so that users can enjoy all kinds of services in the Internet while owning mobility. For example, modern wireless networks can support Internet applications for web accessing and multimedia services. Many issues need to be addressed for such combinations. Host mobility adds a new dimension to many research issues, such as network protocols, resource managements, Web access, and multimedia transmission. For different applications, diverse traffic types should be supported. Lightweight mobile computing devices, such as PDAs and Bluetooth, will be attached to the Internet. Various wireless communication devices, such as Bluetooth and wireless LANs, will be hooked up to the Internet. All these issues bring new challenges. This special section is targeted at the related issues in wireless Internet. More than 50 submissions were received, and 10 papers were accepted in this special issue. The first five papers cover the service issues in wireless Internet. The paper by B. Emako, R. Glitho, and S. Pierre discusses the design, implementation, and evaluation issues of wireless Internet telephony. Y. Lee and I.F. Akyildiz present a new scheme to reduce the link and signaling costs in Mobile IP. The paper by P. McKinley, U.I. Padmanabhan, N. Ancha, and S.M. Sadjadi describes a composable proxy infrastructure that enables mobile Internet users to collaborate via heterogeneous devices and network connections. V.A. Chitre and J.N. Daigle present an analytical model to assess GPRS’s capability of supporting IP-based Internet services. Performance optimization of VoIP calls over wireless links using H.323 protocol is proposed by S.K. Das, E. Lee, K. Basu, and S.K. Sen. Thenextsetof threepaperscovers issuesrelatedtowireless LANs and sensor networks. The important coverage issue concerning the deployment of sensors in a wireless ad hoc sensor network is addressed in the first paper by X.-Y. Li, P.-J. Wan, and O. Frieder. A polling mechanism to support QoS in IEEE 802.11 wireless LANs is proposed by S.-C. Lo, G. Lee, and W.-T. Chen. Formation of scatternets for Bluetooth-based wireless networks is discussed in the paper by C. Petrioli, S. Basagni, and I. Chlamtac. The last set of two papers covers management issues in mobile networks. An analysis for movement-based mobility management in mobile networks is discussed in the first paper by Y. Fang, who makes a thorough numerical analysis for finding the optimal mobility management under various network operation scenarios possible. Admission control for schedulingbursty traffic inCDMAsystems isdiscussed in the paper by Y.-K. Kwok and V.K.N. Lau, where six efficient rate allocation schemes are proposed. Finally, wewould like to take the opportunity to thank the contributingauthors, reviewers, theAreaEditor,Dr. S.L.Min, and the Editor-in-Chief, Professor J.-L. Gaudiot. Without their support, this special section would not be possible.
5689495
A hardware accelerator IP for EBCOT tier-1 coding in JPEG2000 standard
We propose a hardware accelerator IP for the Tier-1 portion of Embedded Block Coding with Optimal Truncation (EBCOT) used in the JPEG2000 next generation image compression standard. EBCOT Tier-1 accounts for more than 70% of encoding time due to extensive bit-level processing. Our architecture consists of a 16-way parallel context formation module and a 3-stage pipelined arithmetic encoder. We reduce power consumption by properly shutting down parts of the circuit. Compared with the known best design, we reduce 17% of the cycle count and reach a level within 5% of the theoretical lower bound. We have implemented the design in synthesizable Verilog RTL with an AMBA-AHB interface for SOC design. FPGA prototyping has been successfully demonstrated and substantial speedup achieved.
6671545
LES: A Layout Expert System
In this paper we describe an expert system for layout generation in a hierarchical VLSI design system. It applies a combination of rule- and algorithmic-based techniques on a new layout style. Experimental results have demonstrated the superiority of this expert system against various standard-cell systems and its competitiveness with human designers.
53235726
Integrating logic retiming and register placement
32261160
Channel assignment for GSM half-rate and full-rate traffic
Global System for Mobile Communications (GSM) supports full-rate and half-rate calls. In this paper, we propose analytical and simulation models to study the performance of four channel assignment schemes for GSM half-rate and full-rate traffic. Our study indicates that among the four schemes, the repacking scheme has the best performance for mixing half-rate and full-rate traffic. We also observe that good performance is expected if the standard derivation of the cell residence time for a mobile station is large.
10713306
Register Minimization beyond Sharing among Variables
Traditionally, it is assumed that every variable in the input HDL (Hardware Description Language) behavioral description needs to be held in a register; A register can be shared by multiple variables if they have mutually disjoint lifetime intervals. This approach is effective for signal-flow-like computations such as various DSP algorithms. However, it is not the best for the synthesis of control-dominated circuits, which usually have variables/signals of different bit-width as well as very long lifetime. To go beyond register minimization by lifetime-analysis-based sharing, we propose holding some variables in the state registers, some signal nets, or some unclocked sequential networks. We have implemented the proposed method in a software program called VReg. Experimental results have demonstrated that Vreg minimizes the number of registers more effectively than the lifetime-analysis-based approach does. Better register minimization also leads to both smaller area and faster designs.