Aging in Network Coding

With network coding, received packets are linearly combined together and broadcasted over the network. Several techniques exist in the literature dedicated to the process of combining packets. However, these techniques focus on forwarding and decoding coded packets without taking into consideration the life cycle of each individual packet. By neglecting this issue, a packet might live forever in coded messages introducing an overhead on the coding/decoding process. In this letter, we introduce the concept of aging that limits the existence of a packet within coded messages. Statistics about the effect of aging on the size of coded messages are provided in order to determine the best tradeoff between the number of required transmissions and then the throughput gain on one hand and the buffering size and then the decoding complexity on the other hand.