Performance bounds for uniformly interleaved serial concatenations with a general inner system

Average performance bounds based on uniform interleaving are considered for a serial concatenation consisting of an outer code, an interleaver and an inner coded modulation system. The exact input-output weight spectrum is derived for the case when only the outer code has the uniform error property. Thereby, an upper bound to the bit error probability under maximum likelihood detection is obtained. However, numerous examples for serially concatenated continuous phase modulation show that neglecting the non-uniform error property of the inner system gives an accurate and less complex approximation. Other inner coded modulations may behave differently.