On the Trade-Off Between Communication Reliability and Latency in the Absence of Feedback

Reliability and latency are two key performance indicators of communications. This paper investigates the tradeoff between them over a random packet erasure channel in the absence of feedback. In contrast to the instant feedback case where guaranteed reliability with low latency can be achieved by simple automatic repeat query (ARQ), we show that in the absence of feedback, the reliability increases with the coding window size, at the cost of the degraded latency performance. Specifically, we propose a sliding window network coding (SWNC) scheme that works in the absence of feedback and achieves various reliability and latency tradeoff by adjusting the coding window size. The tradeoff between the reliability and latency are investigated by deriving the achievable performance of the proposed SWNC scheme as a function of the coding window size. We further show that the proposed scheme degenerates to the existing benchmark schemes that are superior in either latency or reliability, and it has much higher flexibility.