Bulletin Spring‧Summer 1997

highlights of RGC-funded Projects Limitations of the Existing Paging Networks System The paging system has recorded phenomenal growth since its introduction and few telecommunication systems can claim to have a similar market penetration rate. It however has one serious drawback in its current f o rm — i t is not an independent system. To send a message, a user has to telephone a paging system operator to broadcast it. This system may also pose a serious bottleneck i n areas where telephone services are not readily available. It is these considerations that motivated Prof. W. S. Wong of the Department of Information Engineering to plan a prototype mobile cellula r messaging system with his colleague Prof . Yum Tak Shing. In this project they are aided by Prof. Jiandong Li (Xidian University, Xi'an), Prof. Shihua Zhu (Xi'an Jiaotong University), Dr. On-Ching Yue (Lucent Technology, USA), and Dr. Hong Shen Wang (Mediatech Incorporated, Taiwan). The investigators have come up w i t h a mobile, two-way, store-and-forward, packet-switching system called the Voice Interactive Paging Network (VIP Net) to provide text and voice messaging services. By restricting its application to only messaging services, the researchers hope to not only simplify its design but also reduce the development and production cost of the entire system. Salient Features of VIP Net System Architecture The VIP Net consists of a central switching and processing unit (CSPU) and a number of base station units (BSUs) connected by a backbone network (Figure A) that has access to other wire-based data networks such as the Internet via gateway nodes. The CSPU is responsible for routing and storing all messages, and provides a computation platform for a variety of information processing services. Each BSU serves as a micro-cell, and covers a geographic area of interest. Users communcate with the BSUs by specially designed mobile units. The fact that all inter-BSU messages are delivered through the CSPU simplifies the control algorithm as well as administration and maintenance problems. Figure A: VIP Net Architecture The VIP Net 33