A smart carrier sense multiple access (SCSMA) using control messages is proposed for low power and low bandwidth wireless sensor networks (WSNs). In traditional WSNs, the use of media access control (MAC) messages is not recommended since data are of small size. However, if data size is increased with data aggregation or multimedia data, the control messages can be used for reliable data transmission. Thus, an efficient mechanism is needed to avoid the collision of control messages and data. SCSMA employs a blind learning algorithm with low complexity to prevent collision during channel contention and data transmission, even in the presence of hidden nodes. It is shown by simulation and analysis that SCSMA improves throughput by 29.5% to 71.6%, and reduces energy consumption by 20.5% to 36.2%, compared to the recent best approach using MAC messages. Simulation data are also verified by experimental data.

In industrial zones like an underground tunnel or an enclosed space, the quality of data transmission using wireless sensor networks (WSNs) can be reduced significantly due to multipath fading. Thus, we propose a new receiver that can remove the effect of multipath fading completely in low complexity. The proposed receiver combines a coherent detection scheme, which is good for a slow fading environment and a direct conversion synthesizer that satisfies the requirements of WSNs: low cost, low bit error rate, and low power consumption. Since the coherent detection scheme requires high complexity in phase and frequency recovery, we devised a simple adaptive phase adjustor. We prove by both analysis and simulation that the new approach can achieve a bit error rate of 0.1% at power strength 18 dB, which is less than that of the recent best approach by 8 dB.

The proposed protocol features reliable and fast image transmission while periodically transmitting scalar data without interruption by allowing two networks, a LoRa network and a wireless sensor network, with different transmission characteristics to cooperate. It adopts the RT-LoRa protocol for periodic scalar data transmission and uses a WSN-based pipelined transmission method that leverages single-hop message transmission of a LoRa network for image transmission. Thus, it can not only eliminate the control message overhead for time synchronization, slot scheduling, and path establishment for pipelined image transmission in WSNs but also eliminate interferences within WSNs, such as data collisions and data and message collisions, during pipelined image transmission, thereby enabling high reliability and fast transmission. According to experimental results obtained inside a university building, the proposed protocol achieved an image transfer rate of approximately 96% without packet loss, transmitted one 24 KB image in approximately 0.3 s, and achieved an image transfer rate of 100% under the tolerance of one image packet loss. These results indicate a speedup of about 25% compared to a recent pipelined protocol while ensuring near-perfect image transmission quality.

Wireless sensor networks (WSNs) can be used for monitoring and control applications in which a server collects data from a work field and provides a service based on the analysis of those data. Such applications require a timely service as well as a reliable data transmission. A smart multichannel cross-layer protocol is proposed that can satisfy the requirements of industrial WSNs. When every sensor node should send data to a server periodically, the protocol not only shortens data acquisition cycle time (DACT) by allowing parallel data transmission using multiple channels but also improves the reliability by avoiding the collisions of control messages using a smart CSMA mechanism. This also can resolve the well-known chronic WSN problems, such as the hidden node, exposed node, and false blocking. In addition, the proposed protocol is reinforced by an adaptive routing and channel selection scheme to improve the reliability of data transmission under the presence of multipath fading, external interference, and industrial noises. By simulation and analysis, it was proven that the proposed protocol could improve DACT, packet delivery ratio, and energy consumption considerably, compared to other protocols. Furthermore, the protocol was successfully applied to a process monitoring system of a smart factory with high reliability in data transmission and a small DACT.

The paper considers the joint radar and training-based on-off communication system, where the on-off threshold and training is optimized to maximize the mutual information of radar while ensuring communication quality. The closed-form expressions of communication throughput under finite blocklength and radar’s mutual information are derived. The results show that the training and on-off transmission help improve the radar’s mutual information remarkably. The results also show that the improvement of radar’s mutual information is particularly pronounced at low communication power regimes, where a high on-off threshold can maximize average throughput while allowing ample time for radar transmissions.