Quota-based routing and buffer management with heuristic strategies in opportunistic ad hoc networks

Opportunistic ad hoc networks (OppNets) are characterized by intermittent and infrastructure-less connectivity among mobile nodes with limited internode communication and buffer space. Without persistent end-to-end routing information, replication-based routing techniques are often used to distribute duplicate messages in OppNets, which unfortunately leads to enormous costs of transmission, storage, and energy resources. Prior replication-based routing schemes were mainly based on several premises, for example, the availability of global network knowledge, unlimited bandwidth capacity, and homogeneous contact patterns. In this paper, we propose a quota-based routing scheme with finite buffer management, named QRBP, regardless of these weak premises. The QRBP scheme comprises two essential functions. First, only a portion of nodes with higher mobility are delegated to carry a certain quota of message replicas and disseminate those messages to nodes with lower mobility. The message traffic can be evenly diverted to relay nodes, which reduces the transmission overhead in the network. Second, nodes can manipulate message scheduling and dropping to improve the successful delivery rate according to heuristic strategies based on several measures of the quota value, remaining time-to-live, and contact rate with the destination. Furthermore, our study conducts extensive simulations under both synthetic and real mobility scenarios. In terms of transmission overhead ratio and successful delivery rate, the QRBP scheme performs better than Epidemic, Spray and Wait, and Temporal Closeness and Centrality-Based (TCCB) routing schemes, as well as common buffer management policies like Drop Oldest, Drop Newest, Drop Random, and Space-Time Drop.