Internet of Things (IoT) consists of smart objects that communicate together, collect and exchange data. IoT has now a wide range of domain applications such as industry, logistics, healthcare, smart environment, as well as personal, social gaming robot, and smart city. The characteristics required by applications, such as coverage area, transmission data rate, and applicability, refer to the link layer designs of protocols. This paper presents a study of proposed link layer protocols that are used in IoT grouped by short and long distance coverage. For short range protocols, this article study the following: Radio Frequency Identification (RFID), Near Field Communication (NFC), Bluetooth Low Energy (BLE), Low-Rate Wireless Personal Area Networks (LR-WPANs), Z-Wave and IEEE 802.11 a/b/g/n/ah. For the long range protocols, Narrow Band IoT (NB-IoT), Long Term Evolution (LTE), Long Range Protocol (LoRa), and SigFox protocols are considered. A comparative study is performed for each group of protocols, considering their characteristics in order to provide a guideline for researchers and application developers to select the right communication protocol for different applications.

Abstract-We study in this paper the performance of TCP over a wireless link implementing hybrid FEC/ARQ-SR at the link layer. The study is done by simulating a large number of TCP transfers over a wireless link showing Bernoulli errors. We are motivated by how to tune link-level error recovery, e.g. amount of FEC, persistency of ARQ, so as to minimize the latency of TCP. We provide results for different physical characteristics of the wireless link (delay, error rate), different traffic loads and different file sizes. Our main finding is that the latency of TCP always improves with the persistency of ARQ, except for some extreme cases where the delay is large, files are small, and the loss rate is low. When adding FEC, the latency of TCP improves then deteriorates, and the deterioration is more pronounced in the case of large files, high loss rate and small delay. Another finding of our study is that with the hybrid mechanism, the wireless link is able to carry more traffic than when FEC and ARQ-SR are separately used.