On the computation of the joint source-channel error exponent for memoryless system

We study the analytical computation of Csiszar's [1980] random-coding lower bound and sphere-packing upper bound for the lossless joint source-channel (JSC) error exponent, E/sub J/(Q, W), for a discrete memoryless source (DMS) Q and a discrete memoryless channel (DMC) W. We provide equivalent expressions for these bounds, which can be readily calculated for arbitrary (Q,W) pairs. We also establish explicit conditions under which the bounds coincide, thereby exactly determining E/sub J/(Q,W).