Abstract

In the classical Zheng-Tse diversity-multiplexing tradeoff (DMT) framework, people focus

on increasing rate and decreasing outage probability. However, in the fixed outage setting,

this framework is too coarse to accurately describe the system performance. Therefore,

we want to carefully study the performance of transmission schemes that have rate that

increases with average SNR while maintaining a fixed outage probability. We mainly focus

on Hybrid-ARQ schemes. Two other systems (i.e., antenna diversity, time/frequency

diversity) are also studied in order to see the limit of DMT framework in the fixed outage

setting. As will be seen in the case of antenna diversity and time/frequency diversity, an

affine approximation to high SNR outage capacity (i.e., multiplexing gain plus a power/rate

offset) accurately describes performance and illustrates the very significant benefits of diversity.

ARQ is also seen to provide a significant performance advantage, but even an affine approximation

to outage capacity is sometimes unable to capture this advantage and outage capacity must be

directly studied in the non-asymptotic regime.