Utility analysis of simple FEC schemes for VoIP

Abstract

Forward Error Correction (FEC) is an attractive solution for recovering from packet losses in real-time applications. However, in many such applications, due to delay constraints, complex FEC schemes that may enable to approach the Shannon channel capacity cannot be used. In those cases, much simpler FEC schemes are implemented, in which a compressed copy of a packet is concatenated to some subsequent packet. In this paper we analyze the utility gained by such schemes in the case where losses are due to queueing congestion in the network. Loss probabilities in presence of FEC are obtained using sophisticated tools based on Ballot theorems. Our explicit expressions allows us to study numerically several approaches for adding FEC.