The Information Velocity of Packet-Erasure Links

TL;DR

This paper analyzes the maximum reliable transmission rate, called information velocity, over cascaded packet-erasure links with acknowledgment signals, providing bounds and decay rates for failure probabilities in various scenarios.

Contribution

It derives tight bounds on failure probabilities and introduces the concept of information velocity for packet transmission over erasure links, extending results to various arrival processes.

Findings

Derived tight bounds on arrive-failure probability.

Defined and characterized the information velocity.

Extended results to general stationary ergodic arrival processes.

Abstract

We consider the problem of in-order packet transmission over a cascade of packet-erasure links with acknowledgment (ACK) signals, interconnected by relays. We treat first the case of transmitting a single packet, in which ACKs are unnecessary, over links with independent identically distributed erasures. For this case, we derive tight upper and lower bounds on the probability of arrive failure within an allowed end-to-end communication delay over a given number of links. When the number of links is commensurate with the allowed delay, we determine the maximal ratio between the two -- coined information velocity -- for which the arrive-failure probability decays to zero; we further derive bounds on the arrive-failure probability when the ratio is below the information velocity, determine the exponential arrive-failure decay rate, and extend the treatment to links with different erasure probabilities. We then elevate all these results for a stream of packets with independent geometrically distributed interarrival times, and prove that the information velocity and the exponential decay rate remain the same for any stationary ergodic arrival process and for deterministic interarrival times. We demonstrate the significance of the derived fundamental limits -- the information velocity and the arrive-failure exponential decay rate -- by comparing them to simulation results.