دانلود رایگان مقاله انگلیسی تکنولوژی های بی سیم نسل آینده برای اینترنت اشیا - MDPI 2018

1. Introduction

In the fast-growing Internet of Things (IoT), applications from personal devices to industrial instruments and sensors connect wirelessly to the Internet. Considering that a broad diversity of use cases in different environments with specific requirements can be developed, it is clear that no single wireless standard can abundantly predominate. With many standards available on the market, spread over various frequency bands and employing diverse communication protocols, the choice of the best wireless connectivity technology for an IoT application can be quite challenging. The first issues to be evaluated are the frequency bands and global regulations. In fact, in most regions, the available spectrum assignment is subdued to a licensing scheme, which implies that users have to obtain a license from the local regulator to transmit signals in a selected frequency channel. On the contrary, several frequency bands have been designated for Industrial, Scientific, and Medical (ISM) applications. These bands are unlicensed and differ slightly from country to country. In recent years, the popular ISM bands have involved 433 MHz, 868 MHz, 915 MHz, 2.4 GHz, and 5 GHz. Nevertheless, as a standard rule, it is well-known that higher-frequency bands offer a broader bandwidth and hence make broader bandwidth and more channels available. As a consequence, they can serve more extended networks and handle a higher data throughput. Contrariwise, lower-frequency radio waves propagate better than higher-frequency ones and can thus achieve a longer range, especially inside buildings.

3. Conclusions

This Special Issue has pointed out that the application of wireless technologies for the Internet of Things charm much attention in several research fields. In fact, nowadays, there are many wireless technologies available in the world. It is clear that each one has advantages, and, at the same time, none is flawless. The question on which technology is the best for most applications remains open. In fact, every application scenario involves specific requirements concerning the range, power consumption, throughput, and network topology. Besides, further considerations include the cost, ease of integration, and security. Several papers have been submitted in this Special Issue to cope with many of these problems, presenting new solutions and innovative methods. The accepted papers have proposed smart solutions, intelligent algorithms and original network models that produce a substantial augmentation to the literature that deals with the application of wireless technologies for the Internet of Things.