As many radio chips used in today's sensor mote hardware can work at different frequencies, several multi-channel communication protocols have recently been proposed to improve network throughput and reduce packet loss for wireless sensor networks. However, existing work cannot utilize multiple channels to provide explicit guarantees for application-specified end-to-end communication delays, which are critical to many real-time applications such as surveillance and disaster response. In this paper, we propose MCRT, a multi-channel real-time communication protocol that features a flow-based channel allocation strategy. Because of the small number of orthogonal channels available in current mote hardware, MCRT allocates channels to network partitions formed based on many-to-one data flows. To achieve bounded end-to-end communication delay for every data flow, the channel allocation problem has been formulated as a constrained optimization problem and proved to be NP-complete. We the...