###### Abstract  
With the development of Internet of Things (IoT) technologies, industries such as healthcare have started using low-powered sensor-based devices. Because IoT devices are typically low-powered, they are susceptible to cyber intrusions. As an emerging information security solution, blockchain technology has considerable potential for protecting low-powered IoT and devices. Blockchain technology provides promising security features such as cryptography, hash functions, time stamps, and a distributed ledger function. Therefore, blockchain technology can be a robust security technology for securing IoT low-powered devices. However, the integration of blockchain and IoT technologies raises a number of research questions. Scalability is one of the most significant. Blockchain' scalability of low-powered sensor networks needs to be evaluated to identify the practical application of both technologies in low-powered sensor networks. In this paper, we analyse the scalability limitations of three commonly used blockchain algorithms running on low-powered single-board computers communicating in a wireless sensor network. We assess the scalability limitations of three blockchain networks as we increase the number of nodes. Our analysis shows considerable scalability variations between three blockchain networks. The results indicate that some blockchain networks can have over 800 ms network latency and some blockchain networks may use a bandwidth over 1600 Kbps. This work will contribute to developing efficient blockchain-based IoT sensor networks. blockchain; low-powered wireless sensor networks; IoT; scalability +
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Although there are promising security features of blockchain technology, scalability is still a key barrier when it comes to their implementation across wireless low-powered sensor networks. Blockchain network throughput, bandwidth, hash rate, latency, and data transaction rate are major aspects of a scalable blockchain network [7]. Understanding how the performance of different blockchains changes as the number of nodes increases is important. We explore this issue using an experimental test bed that runs three of the most popular blockchain algorithms [6]. Although blockchains provide security benefits, as most IoT networks are low-powered, the integration of blockchain technology may decrease network performance efficiency and cause unnecessary scalability issues. An increment in data transmission latency or data loss due to the increment of blockchain network users can create significant consequences, including a reduction in Quality of Service (QoS) [8]. Also, unnecessary latency of sensitive data transactions or data loss in healthcare may put lives at risk. As most IoT networks use wireless technologies for data transmission, bandwidth usage is also another key challenge [8]. Blockchains transmit data as a chain of blocks, and the bandwidth usage of blockchain networks may be higher compared to other peer-to-peer networks. Blockchain networks may require additional bandwidth capacity, and the higher usage of bandwidth may limit the network access for users [8]. Considering the importance of blockchain scalability, we have developed a blockchain network test bed using twenty blockchain nodes, and we have installed three commonly used blockchain algorithms to run on the test bed. We have analysed the network scalability with respect to blockchain network latency, block transaction rate, and bandwidth parameters [8]. The architecture of the research methodology is blended. We used experimental results collected from the test bed and statistical software tools to analyse the collected network latency, bandwidth usage, and block transaction rate data. All the data were generated during the experiments in a lab environment [9]. The remainder of this paper is structured as follows: In Section 2, we discuss blockchain technology. In Section 3, we look at blockchains in the healthcare sector. We provide an overview of related work in Section 4.