Showing papers by "Yi-Bing Lin published in 2000"

Wireless and Mobile Network Architectures

Abstract: From the Publisher: This book gives network engineers and managers a window on the world of wireless and mobile networks, from the enabling technologies and protocols to creating and managing mobile services." "Lin and Chlamtac use a unique sustained example approach to teach you how PCS concepts apply to real network operation. For example, they use location update to illustrate concepts in chapters on network signaling, mobility, security/handoff, and mobile prepaid services.

A new random walk model for PCS networks

Abstract: 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.

Portable movement modeling for PCS networks

Abstract: In this paper, we propose a new model for the portable movement in personal communications services (PCSs) networks. Based on this model with general interservice time and registration area residence time distributions, an analytic expression for the probability that a portable moves across K registration areas (RAs) is obtained. The busy-line effect on this quantity is also studied and an analytic expression is presented. The result given in this paper is very useful for cost analysis for location updating and paging.

Performance analysis for voice/data integration on a finite-buffer mobile system

Abstract: Personal communication service (PCS) networks offer mobile users diverse telecommunication applications, such as voice, data, and image, with different bandwidth and quality-of-service (QoS) requirements. This paper proposes an analytical model to investigate the performance of an integrated voice/data mobile network with finite data buffer in terms of voice-call blocking probability, data loss probability, and mean data delay. The model is based on the movable-boundary scheme that dynamically adjusts the number of channels for voice and data traffic. With the movable-boundary scheme, the bandwidth can be utilized efficiently while satisfying the QoS requirements for voice and data traffic. Using our model, the impact of hot-spot traffic in the heterogeneous PCS networks, in which the parameters (e.g., number of channels, voice, and data arrival rates) of cells can be varied, can be effectively analyzed. In addition, an iterative algorithm based on our model is proposed to determine the handoff traffic, which computes the system performance in polynomial-bounded time. The analytical model is validated by simulation.

Mobile prepaid phone services

Abstract: During the past few years, the mobile prepaid service has been growing exponentially all over the world. Four approaches have been proposed to provide mobile prepaid service. We describe these approaches and compare their strengths and weaknesses. Our analysis indicates that the handset based approach is a low-cost, high-risk solution. The wireless intelligent network approach is a high-cost, low-risk solution. The service node approach is a quick solution, which allows fast deployment with limited capacity. The hot billing approach is an average solution that cannot provide real-time rating.

Performance analysis for dual band PCS networks

Abstract: 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.

Comparing soft and hard handoffs

Abstract: This paper studies the soft-handoff mechanism and compares its performance with hard handoff. Our study indicates that although a handset may potentially consume extra radio links in soft handoff, the mechanism provides better opportunity to transfer the link successfully in the handoff procedure. Thus, by carefully planning the overlay areas of cells, soft handoff can outperform hard handoff.

iGSM: VoIP service for mobile networks

Abstract: This article proposes iGSM: a voice-over-IP value-added service for the mobile network. The iGSM service provides user mobility to subscribers, which allows them to use either GSM handsets or H.323 terminals (IP phones or PCs) to access telecommunications services. We describe how the iGSM registration, deregistration, and call delivery procedures can be implemented without modifying the GSM network. We study how the tromboning effect in the standard GSM system can be avoided when accessing the IP network. Then we investigate the misrouting problem caused by user mobility.

Computer telephony integration and its applications

Abstract: Computer telephony integration (CTI) enhances the capability and flexibility of the switches or the network end equipment by computer technology. This article introduces the components of CTI such as switch-to-host interfaces, application programming interfaces, and resource architectures. Then we describe two CTI configurations: first-party call control and third-party call control. CTI-based telecommunication services such as unified messaging and call center are described. We also illustrate the Integrated Office Telephony System (IOTS), a CTI system developed at Computer Communication Research Laboratories, which integrates the switch and CTI server on a personal computer platform.

Overflow control for cellular mobility database

Abstract: In a cellular phone system, the service area is partitioned into several location areas (LAs). Every LA is associated with a mobility database called visitor location register (VLR). When a mobile user enters an LA, the user must register to the VLR before receiving any cellular service. If the VLR is full, the registration procedure fails and the system cannot deliver services to the user under the existing cellular technology. To resolve this problem, we propose a VLR overflow control scheme to accommodate the incoming mobile users during VLR overflow. Our scheme only requires minor modifications to the existing cellular mobility management protocols. Particularly, no modification is made to the mobile phones. An analytic model is proposed to investigate the performance of the overflow control scheme. When exercising the scheme, the call setup procedure for an "overflow" user is more expensive than that for a "normal" user. Under the range of input parameters considered in our study, we show that even if the VLR overflow situation is serious, the overhead for exercising the overflow control scheme is very low.

Demand re-registration for PCS database restoration

Abstract: In a Personal Communications Services (PCS) network, mobility databases such as Home Location Register (HLR) and Visitor Location Register (VLR) are utilized to support mobility management for Mobile Stations (MSs). If the location databases fail, the location information loss or corruption will seriously degrade the service offered to the subscribers. In this paper, we propose a new VLR failure recovery scheme called demand re‐registration. In this scheme, the VLR broadcasts a re‐registration request to all MSs after the VLR failure. When an MS receives the re‐registration request, it sends a registration message to the VLR to recover the location record. Since all MSs will re‐register after receiving the broadcasting request, traffic jam (and thus collisions) may occur. If a collision occurs, then the involved MSs must re‐send the registration messages. This paper studies the performance of demand re‐registration by investigating how effectively the re‐registration can recover the location record for an MS before the first MS call termination occurs. Our results indicate that demand re‐registration can effectively recover VLR failure.

Design issues for optimistic distributed discrete event simulation

Abstract: Simulation is a powerful tool for studying the dynamics of a system. However, simulation is time-consuming. Thus, it is natural to attempt to use multiple processors to speed up the simulation process. Many protocols have been proposed to perform discrete event simulation in multi-processor environments. Most of these distributed discrete event simulation protocols are either conservative or optimistic. The most common optimistic distributed simulation protocol is called Time Warp. Several issues must be considered when designing a Time Warp simulation; examples are reducing the state saving overhead and designing the global control mechanism (i. e., global virtual time computation, memory management, distributed termination, and fault tolerance). This paper addresses these issues. We propose a heuristic to select the checkpoint interval to reduce the state saving overhead, generalize a previously proposed global virtual time computation algorithm, and present new algorithms for memory management, distributed termination, and fault tolerance. The main contribution of this paper is to provide guidelines for designing an efficient Time Warp simulation.

Modeling mis-routing calls due to user mobility in wireless VoIP

Abstract: This letter proposes an analytic model to study the mis-routing problem caused by user mobility in a wireless VoIP system. We derive the probability that there are n mis-routed calls when a subscriber moves from IP network to the GSM network. Our study indicates that if the user residence times in GSM location areas, inter-call origination times and the inter-call delivery times are of the same order, then the mis-routing effect can not be ignored.

Performance of a weakly consistent wireless web access mechanism

Abstract: In wireless web information access, long response may be experienced. To reduce the response times of wireless data access in a mobile network, caches are utilized in the wireless handheld devices or wireless proxy server. This paper proposes a wireless web data access algorithm for WAP (wireless application protocol) caching proxy to speed up data access. Our algorithm utilizes the access frequency to tune the data expiration time. The performance of the algorithm is investigated and is compared with existing TTL-based algorithms. Our study indicates that good performance is expected for the new algorithm.

Design and implementation of an OA&M system for WLL network

Abstract: This paper describes the design and implementation of an OA&M system for DECT-based WLL network. This system follows the client-server architecture that enables remote management through the Internet. Object-oriented design is used to yield quality software, where the entire WLL network is treated as a hierarchical collection of objects. The “plug-in” mechanism provides the capabilities of replacing and extending OA&M functionalities in run-time. Design patterns are applied to improve the reusability of software components. Two types of user interfaces are implemented in different platforms to provide access to the OA&M system. Although our design is tailored for the WLL network, it is also appropriate to serve as the OA&M system for other small-scale telecommunication systems.

PBX based mobility manager for wireless local loop

Abstract: SUMMARY In a typical wireless local loop (WLL) system, a user can only access the wireless services at "xed locations. This paper proposes a private branch exchange (PBX) based mobility manager for WLL, which allows users to receive wireless service at any locations within the WLL service area. We show how the mobility manager can be implemented in a PBX environment where the base stations are connected to the PBX using standard line or trunk interfaces. The proposed mobility manager can be tailored to connect wireless system such as DECT or PACS. Copyright ( 2000 John Wiley & Sons, Ltd.