Meteor burst communication is an important communication mode for a number of possible civilian and military applications. This paper proposes a channel modeling and simulation based on OPNET for meteor burst communications. Analyzing the characteristics of underdense meteor burst channel, the multi-layer node models of master station and slave station are presented to create practical simulation scenario of meteor burst communications. The simulation processes of half-duplex communication as well as full-duplex communication are designed to execute simulation. The results demonstrated that the channel model based on OPNET is consisted with meteor burst communication very well, and full-duplex communication is better than full-duplex communication in effectiveness.

Modern complex circuits are described in very high speed integrated circuit hardware description language (VHDL) and difficult to verify. This paper proposes a systematic and visual dependency analysis method based on VHDL. The dependency relationships including control dependency, data dependency, signal control dependency and signal data dependency are defined. The entity dependency graph is presented and its generation algorithm, which searches the dependency relationships in hardware processes and between hardware processes, are developed. The experiment of a typical keyboard demonstrates that it is a visual and efficient method to analyze dependency relationships of VHDL for formal verification.