Sensitivity of energy detected multilevel PAM systems to threshold mismatch

In this paper we theoretically evaluate the sensitivity resulted from a decision threshold mismatch with multilevel and energy detected pulse amplitude modulated (ED-PAM) signals. We quantify the relation between the threshold offset and the degradation in the required signal-to-noise ratio to preserve a desired symbol error rate. Based on the analysis we conclude some useful guidelines with respect to various system parameters. One of the main problems in an ED-PAM with arbitrary number of modulation levels, integration time, and bandwidth is to find a simple way to calculate the optimal threshold values. We rise to this challenge by proposing a new multilevel threshold calculation method which is attractive to use from both performance and complexity point of views for a wide range of system parameters. The results can be used, e.g., in an impulse radio for high data rate short-range wireless communications.