With today's fast changing business environment and distributed global organizations, business processes of enterprises need to be able to quickly adapt to the new business requirements. BPI middlewares are thus developed to facilitate the integration of various types of enterprise applications that operate within or across enterprise boundaries. Due to the varying complexity and distributed nature of the business processes and the wide range of enterprise applications' characteristics, capacity planning and performance tuning of BPI middleware has been a challenge for engineers who develop and deploy BPI solutions. This poster presents a layered queueing network-based performance model for a BPI middleware to address this challenge.

Traditional capacity sizing of enterprise systems relies on benchmarking a system using benchmark clients that generate a workload pattern similar to real-world workload. When new functions are added to the system or when the workload pattern changes, benchmarking has to be performed again. This is a costly and time-consuming approach for capacity planning. Layered queueing models have been used to study the performance of software systems. The approach is able to identify major performance parameters of software systems. Given a workload pattern, the models can be solved analytically to predict the system performance quickly. This paper proposes a layered queueing model for predicting the performance of distributed enterprise applications built on Enterprise JavaBeans (EJB) technology. We show how such models can be applied for capacity sizing of distributed enterprise systems. We demonstrate this by using this methodology to predict the performance of a sample application built on an EJB-based business-to-business e-commerce platform. We compare deployment options and study the effect of different workload patterns on system capacity.

Wireless coverage is often problematic. This is especially true for mobile radio networks, e.g., cellular networks. It is a very frustrating experience for a mobile user finding out that he is out of the coverage of his wireless service provider when he needs to send an emergency message. This paper proposes a method and system for delivering electronic messages over a wireless cellular communications network when the sender of a message is out of the coverage area. With this method the message is broadcasted repeatedly until a mobile wireless courier receives the message and stores the message. When the courier is within range of a base station of the cellular communication network, it then transmits the stored message to the base station for delivery.

A new data traffic control scheme is developed for maintaining the packet error rate (PER) of real-time voice traffic while allowing nonreal-time data traffic to utilize the residual channel capacity of the multi-access link in an integrated service wireless CDMA network. Due to the delay constraint of the voice service, voice users transmit their packets without incurring further delay once they are admitted to the system according to the admission control policy. Data traffic, however, is regulated at both the call level (i.e., admission control) and at the burst level (i.e., congestion control). The admission control rejects the data calls that will otherwise experience unduly long delay, whereas the congestion control ensures the PER of voice traffic being lower than a specified quality of service (QoS) requirement (e.g., 10/sup -2/). System performance such as voice PER, voice-blocking probability, data throughput, delay, and blocking probability is evaluated by a Markovian model. Numerical results for a system with a Rician fading channel and DPSK modulation are presented to show the interplay between admission and congestion control, as well as how one can engineer the control parameters. The tradeoff of using multiple CDMA codes to reduce the transmission time of data messages is also investigated.

The design issues and the performance evaluation of packet radio communication systems for automated highway systems (AHS) are presented. The main focus is on the analysis and interaction between the physical and the link-access layers of a packet radio system that can accommodate communication between vehicles and roadside infrastructure as well as between vehicles. We discuss the information flow requirements of AVCS (advanced vehicle control systems) and ATMIS (advanced traffic management and information systems) services and we present preliminary results from the performance evaluation of four multiple access schemes (slotted-ALOHA, reservation-ALOHA, TDMA, and CDMA).