This paper presents a message queue telemetry transport (MQTT) broker with priority support for emergency events in the Internet of Things (IoT), which is abbreviated p-MQTT. To support the timely and reliable message delivery of emergency events, the p-MQTT classifies the published messages coming into the broker server and controls their priority according to the classification results. To this end, the p-MQTT consists of three components: virtual queue, classification, and priority control. The virtual queue stores the published messages separately according to their type, for which the p-MQTT broker server maintains three virtual queues: Urgent, Critical, and Normal. The classification component classifies the published messages into the three types mentioned above by checking the message type field in the published message header and stores the messages in the appropriate virtual queue. Finally, the priority control assigns a forwarding priority to each virtual queue and adjusts the quality-of-service (QoS) level of the messages within each virtual queue accordingly. To verify its effectiveness, we conduct an experimental implementation of the p-MQTT. The results show that the p-MQTT achieves better performance in emergency events than the existing MQTT.

This paper presents hybrid medium access control (MAC) for time-switching simultaneous wireless information and power transfer (TS-SWIPT) that improves channel utilization and the timeliness of data and power delivery. To this end, the proposed hybrid MAC uses a superframe structure including a beacon period (BP), a contention access period (CAP), and a channel time allocation period (CTAP), and adaptively adjusts the CAP and CTAP lengths according to the data and power delivery time requested by sensor devices. Furthermore, it adjusts the priority of data and power delivery according to the residual power level of each sensor device. To evaluate the performance of the proposed hybrid MAC, an experimental simulation was conducted. The results show that the proposed hybrid MAC outperforms the existing MAC in terms of resource utilization, aggregate throughput, and charging delay.

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