On Multi-Path Streaming Codes

Streaming codes are a class of packet-level erasure-recovery codes, designed to recover from dropped packets within a strict decoding-delay constraint. These codes are well-studied for the case when a single path or link connects source and destination and this path is modeled using a sliding-window channel model that permits a restricted class of random and burst erasures. However, the occurrence of events such as deep fades, can cause long erasure bursts which cannot be handled within a single-path setting, under a decoding-delay constraint. In 5G settings such as integrated-access-backhaul and dual connectivity, multiple paths exist from source to destination and this path diversity can be put to use to provide improved reliability while meeting the decoding-delay constraint. We explore multipath streaming codes in this paper, where each path is modeled using a sliding-window erasure channel model which, within any window of a fixed time duration, permits either a single erasure burst or else a set of random erasures. We study these codes under two settings, (a) the case when a fixed number of paths can have inadmissible erasure patterns at any time, including the case of long bursts, and (b) the case when a fixed number of paths can simultaneously be in burst mode at any time. For (a), we derive a rate upper-bound and provide matching code constructions. For (b), we show that it is possible for certain parameter sets, to achieve a higher rate than the maximum possible in (a).