  In wireless sensor networks (WSNs), the opportunistic routing has better
performances on packet delivery probability than the deterministic routing. For
reducing the transmission delay and duplicate transmission in opportunistic
routing, the candidate forwarding set optimization technology is proposed. This
technology is crucial to opportunistic routing. The prior arts have limitations
on improving the routing performances. Therefore, in this paper, we propose the
concept of the network-based approach to address the disadvantages of prior
arts. In the network-based approach, the nodes in the candidate forwarding set
are divided into different fully connected relay networks. For the forwarding
nodes in CFS, more than one relay network can be constructed and only one relay
network can be chosen as the final relay network. So, first, we propose the
fully connected relay network judgment algorithm to judge whether the chosen
network is fully connected or not. Next, the properties of these networks are
investigated. In this algorithm, the relay network selection takes the packet
delivery probability between the sender and the relay networks, the
transmission delay, and the forwarding priorities of nodes in relay networks
into account to choose the most effective relay network. The nodes in this
relay network will be chosen as final forwarding nodes. By these, the
transmission delay and duplicate transmission are reduced while the efficiency
of opportunistic routing is kept. Based on these innovations, the proposed
algorithm can improve network performances greater than that of ExOR and SOAR.
