Evaluation of Union bounds for Space-Time codes based on a common function

Error-rate evaluation of space-time codes using union bounds sometimes requires very heavy computational loads and so is impractical to use. In this paper, a common function shared by different union bounds is derived and used to develop a modified union bound (MUB) for error-rate evaluation. Results of numerical evaluations and Monte-Carlo simulation on two 2times2 rotation-based S-T codes show that the MUB provides a good compromise between the required computational load and the accuracy for error-rate evaluation.