Data rate determination for fixed, matched filter channels

In today's world, with ever rising data rate requirements and ever shrinking budgets, the use of existing equipment to perform new tasks is highly desirable. Often the need to increase the data transmission rates through an existing system is clear, yet financial or logistical constraints do not permit complete redesign of the system. Other situations do not allow the designer access to all of the system components, as in satellite systems. Whatever the circumstances, the desirable result is to maximize the data rates through existing channels. This paper presents a method for determination of the allowable data rates in existing channels. In addition, a measure of the expected degradation associated with the use of a pre-existing receive filter and matched transmit filter pair at increased transmit data rates is determined. Examples are given for different filter types and data modulation formats. The method is demonstrated through simulation of Butterworth and elliptical filters for 8PSK and 16QAM modulation.