BER of differentially detected π/4 DQPSK in the presence of quadrature gain imbalance

The effect of circuit level distortions on system level performance is becoming an important issue in optimizing the design of low power receivers. Circuit level distortions that can be largely ignored in full power designs, must be accounted for in the link budget of low power systems. In this paper, we present an analysis that demonstrates and quantifies the effect of one such distortion. We present a closed form expression for the BER of differentially detected /spl pi//4 DQPSK in the presence of AWGN and distorted by a quadrature gain imbalance in the receiver

A Component-Based Architecture for Adaptive, Collaborative Web-Based Learning

Abstract. The limitations of current Internet-based learning systems (e.g., their inability to deal with diverse learners and requirements and the high cost of developing a new learning system) have lead to ed-ucational middleware that can handle diverse requirements and vari-ous learning components distributed over the Internet. Following the paradigm of component-oriented development we have designed a learn-ing middleware suite, called the Collaborative and Sharable Learning (CoSL) system. CoSL is both a platform for building e-learning systems and a tool set for making it easier to develop course materials for e-learning. The CoSL system is context-independent so that its adaptation to a specific topic can be achieved with limited effort and time. To meet the challenging requirements of learning systems, the CoSL system has adopted three advanced techniques: (1) XML-based data exchange and integration, (2) agent-based communication and (3) data mining-based intelligent decision making. CoSL allows us to build and manage global learning systems in a distributed and heterogeneous environment.