1 research outputs found
Delay Asymptotics with Retransmissions and Incremental Redundancy Codes over Erasure Channels
Recent studies have shown that retransmissions can cause heavy-tailed
transmission delays even when packet sizes are light-tailed. Moreover, the
impact of heavy-tailed delays persists even when packets size are upper
bounded. The key question we study in this paper is how the use of coding
techniques to transmit information, together with different system
configurations, would affect the distribution of delay. To investigate this
problem, we model the underlying channel as a Markov modulated binary erasure
channel, where transmitted bits are either received successfully or erased.
Erasure codes are used to encode information prior to transmission, which
ensures that a fixed fraction of the bits in the codeword can lead to
successful decoding. We use incremental redundancy codes, where the codeword is
divided into codeword trunks and these trunks are transmitted one at a time to
provide incremental redundancies to the receiver until the information is
recovered. We characterize the distribution of delay under two different
scenarios: (I) Decoder uses memory to cache all previously successfully
received bits. (II) Decoder does not use memory, where received bits are
discarded if the corresponding information cannot be decoded. In both cases, we
consider codeword length with infinite and finite support. From a theoretical
perspective, our results provide a benchmark to quantify the tradeoff between
system complexity and the distribution of delay.Comment: 12 pages, 4 figure