Reliability Capacity of Half-Duplex Channels with Strict Deadlines

A fundamental characterization of a half-duplex wireless system with packet losses under traffic with hard deadlines is instrumental to understanding and developing efficient, coding aware policies for real-time applications. We set forth the concept of reliability capacity with a limited number of transmissions and provide closed-form upper and lower bounds for this capacity. We show that the reliability capacity converges to the capacity of a classical erasure channel as the deadline constraint is relaxed. In our framework, the effect of feedback is analyzed both in terms of the reliability capacity and in terms of its advantages towards the mean number of packets that can be transmitted reliably. Optimal schemes for leveraging feedback are presented and the results show that a judicious use of even a single feedback packet can have a significant impact on the mean performance.