ST-Drop: A novel buffer management strategy for D2D opportunistic networks

In D2D opportunistic networks, nodes need to cooperate acting as relays for transmitting messages to other nodes according to an opportunistic routing algorithm. To store these messages until they are propagated, each node uses a buffer with limited capacity. However, when multiple messages are forwarded in the network, the number of incoming messages may exceed the nodes' capacity, causing a buffer overflow. In this scenario, message dropping policies are very important to this problem, because when a message is dropped, there is a chance that other copies of this message still exist in the network. In this work, we propose a new buffer management algorithm for opportunistic routing in D2D networks named ST-Drop (Space-Time-Drop). We have evaluated our solution in three different types of opportunistic routing algorithms: epidemic-based, probabilistic, and social-aware. We have conducted simulations using two different publicly available data sources and considered different network traffic loads. Compared to other message drop policies, ST-Drop obtained the highest message delivery ratio in all considered scenarios and the lowest overhead when applied to the state-of-art social-aware and probabilistic routing algorithms, namely, Bubble Rap and Prophet.