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The developments of Narrow Band Internet of Things have attracted much attention from both academia and industry nowadays. While Narrow Band Internet of Things is gradually designed for commercial applications, it also confronts with several security concerns such as identification and privacy. Blockchain technique is equipped with authentication, auditing, and accountability, and thus it can serve as a promising tool for providing secure data communication on the network. To enhance the security level and achieve reliable data authentication and accountability for Narrow Band Internet of Things system, in this article, we combine the merits of blockchain technique and propose a blockchain-based architecture for Narrow Band Internet of Things. The presented architecture consists of three layers which are sensing layer, transport layer, and transaction layer. We describe the interaction processes between each layer in detail and construct the algorithms which are used to conduct data authentication and blockchain generation. By evaluation, our scheme is demonstrated to obtain favorable performances in terms of privacy, authentication, accountability, and efficiency, which makes it an appropriate method to be applied for secure data communication in Narrow Band Internet of Things systems.

Power control technology is widely used in wireless sensor networks to improve network performance. The asymmetric transmission power strategy used in power control technology causes the re-emergence of hidden-node problems and more serious exposed-node problems. This article analyzes the reasons of these problems and proposes the concept of the pan-hidden node and pan-exposed node. To avoid pan-hidden-node problems and mitigate pan-exposed-node problems, a concurrent transmission mechanism is presented. The concurrent transmission mechanism contains a strict time schedule for different categories of frames and an interference degree criterion to ensure concurrent transmission. The rigorous time schedule can guarantee that different classes of frames do not interfere with one another. The interference among the frames of the same type is constrained by the interference degree criterion. Finally, the performance of the concurrent transmission mechanism is evaluated using simulation experiments.

In wireless sensor networks, cooperative communication can combat the effects of channel fading by exploiting diversity gain achieved via cooperation communication among the relay nodes. A cooperative automatic retransmission request (ARQ) protocol based on two-relay node selection was proposed in this paper. A novel discrete time Markov chain model in order to analyze the throughput and energy efficiency was built, and system throughput and energy efficiency performance of proposed protocol and traditional ARQ protocol were studied based on such model. The numerical results reveal that the throughput and energy efficiency of the proposed protocol could perform better when compared with the traditional ARQ protocol.