  This work analyzes the high-SNR asymptotic error performance of
outage-limited communications with fading, where the number of bits that arrive
at the transmitter during any time slot is random but the delivery of bits at
the receiver must adhere to a strict delay limitation. Specifically, bit errors
are caused by erroneous decoding at the receiver or violation of the strict
delay constraint. Under certain scaling of the statistics of the bit-arrival
process with SNR, this paper shows that the optimal decay behavior of the
asymptotic total probability of bit error depends on how fast the burstiness of
the source scales down with SNR. If the source burstiness scales down too
slowly, the total probability of error is asymptotically dominated by
delay-violation events. On the other hand, if the source burstiness scales down
too quickly, the total probability of error is asymptotically dominated by
channel-error events. However, at the proper scaling, where the burstiness
scales linearly with 1/sqrt(log SNR) and at the optimal coding duration and
transmission rate, the occurrences of channel errors and delay-violation errors
are asymptotically balanced. In this latter case, the optimal exponent of the
total probability of error reveals a tradeoff that addresses the question of
how much of the allowable time and rate should be used for gaining reliability
over the channel and how much for accommodating the burstiness with delay
constraints.
