| Summary: | The technology of software-defined devices has great prospect in updating the programs of the sensing devices to enable the devices to adapt to the new environments and applications. However, to effectively spread the code to each node in the software-defined-based wireless sensor networks (WSNs) is still a challenging task. In this paper, a proportion to duty cycle length-based broadcast (PDLB) scheme is proposed to disseminate code in duty cycle-based WSNs in a fast and energy-efficient style. In PDLB scheme, the sink first initiates a code broadcast. Then, the nodes that have received code start counting and calculate the priority of broadcasting based on an improved counter-based priority broadcasting approach proposed in this paper. Next, the nodes with the highest priority select k slots to broadcast according to the length of duty cycle so that the code can be spread from the sink to the network periphery. Finally, the nodes that have not obtained the code wait for a period of timeout to broadcast to actively send code request; after receiving code request, the node that obtained the code initiates a code broadcast to cause the code requester to obtain the code. The PDLB scheme has been validated by comprehensive experiments that show the following regularities. The smaller the count threshold value C<sub>h</sub>, the larger the number of slots selected for broadcasting that can guarantee a certain coverage ratio, while the code dissemination speed slows down at the same time. The longer the duty cycle is, the more the broadcast time is required, and the larger the transmission delay is. For each slot added in a working cycle, the number of broadcasts is increased by 1.54%-33.33% and the transmission delay is augmented by 2.27%-70.04%. The higher the node density is, the shorter the code spread speed is. As the network density increases, the transmission delay is reduced by 0.83%-65.87%. When the number of broadcasting slots is half of the total number of slots in a work cycle, the energy consumption reaches the lowest value.
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