Contention resolution represents a performance critical task in dense wireless networks since many Medium Access Control (MAC) protocols solely rely on the carrier-sense capabilities of the transceivers. Typical transceivers require a large amount of time to detect a busy radio channel. Especially, in the case that the transceiver has been switched off or has to be switched from receive to transmit mode. It is thus not able to sense the media during the switching phase, which leads to a large number of collisions in dense networks with correlated event-driven traffic load. In this paper the Backoff Preamble Sequential (BPS) MAC protocol is introduced which uses a sequential contention resolution to reduce the number of competing nodes step by step.