This article addresses the problem of performance degradation of wireless sensor networks for scenarios involving data gathering to a small number of node sinks; as the data travel toward a sink, its neighbor nodes experience high loads and congestion. Using CSMA/CA as the basic access protocol, we implemented CoSenS, a collecting and sending burst scheme, on the top of it to address these issues. The idea of CoSenS is that a router does not retransmit packets as they arrive. Instead, it collects data from its children and other neighbor routers and then sends them into a burst during a period of time that we call transmission period. The performance analysis shows that, as the load increases, our scheme maximizes the throughput and successful transmission rates while minimizing the end-to-end delay compared to CSMA/CA.