Bluetooth Low Energy (BLE) is an emerging low-power wireless technology developed for short-range control and monitoring applications that is expected to be incorporated into billions of devices in the next few years. This paper describes the main features of BLE, explores its potential applications, and investigates the impact of various critical parameters on its performance. BLE represents a trade-off between energy consumption, latency, piconet size, and throughput that mainly depends on parameters such as connInterval and connSlaveLatency. According to theoretical results, the lifetime of a BLE device powered by a coin cell battery ranges between 2.0 days and 14.1 years. The number of simultaneous slaves per master ranges between 2 and 5,917. The minimum latency for a master to obtain a sensor reading is 676 μs, although simulation results show that, under high bit error rate, average latency increases by up to three orders of magnitude. The paper provides experimental results that complement the theoretical and simulation findings, and indicates implementation constraints that may reduce BLE performance.

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LoRaWAN is a flagship Low-Power Wide Area Network (LPWAN) technology that has highly attracted much attention from the community in recent years. Many LoRaWAN end-devices, such as sensors or actuators, are expected not to be powered by the electricity grid; therefore, it is crucial to investigate the energy consumption of LoRaWAN. However, published works have only focused on this topic to a limited extent. In this paper, we present analytical models that allow the characterization of LoRaWAN end-device current consumption, lifetime and energy cost of data delivery. The models, which have been derived based on measurements on a currently prevalent LoRaWAN hardware platform, allow us to quantify the impact of relevant physical and Medium Access Control (MAC) layer LoRaWAN parameters and mechanisms, as well as Bit Error Rate (BER) and collisions, on energy performance. Among others, evaluation results show that an appropriately configured LoRaWAN end-device platform powered by a battery of 2400 mAh can achieve a 1-year lifetime while sending one message every 5 min, and an asymptotic theoretical lifetime of 6 years for infrequent communication.

Abstract-The Constrained Application Protocol (CoAP) is a lightweight RESTful application layer protocol devised for the Internet of Things (IoT). Operating on top of UDP, CoAP must handle congestion control by itself. The core CoAP specification defines a basic congestion control mechanism, which is however not capable of adapting to network conditions. Yet, IoT scenarios exhibit significant resource constraints which pose new challenges on the design of congestion control mechanisms. In this paper we present the CoAP Simple Congestion Control/Advanced (CoCoA), an advanced congestion control mechanism for CoAP being standardized by the Internet Engineering Task Force (IETF) CoRE working group. CoCoA introduces novel Round Trip Time (RTT) estimation techniques, together with a Variable Backoff Factor (VBF) and aging mechanisms in order to provide dynamic and controlled Retransmission Timeout (RTO) adaptation suitable for the peculiarities of IoT communications. We conduct a comparative performance analysis of CoCoA and a variety of alternative algorithms including state-of-the-art mechanisms developed for TCP. The study is based on experiments carried out in real testbeds. Results show that, in contrast with the alternative methods considered, CoCoA consistently outperforms default CoAP congestion control mechanism in all evaluated scenarios.

The Constrained Application Protocol (CoAP) has been designed by the Internet Engineering Task Force (IETF) for Internet of Things (IoT) devices. Due to the limited radio channel capacities and hardware resources of such devices, congestion can be a serious problem. CoAP addresses this important issue with a basic congestion control mechanism. CoCoA, an Internet-Draft proposal, introduced alternative congestion control mechanisms for CoAP. Yet, there has been limited evaluation of these congestion control mechanisms in the literature. In this paper, we assess the methods applied in CoCoA in detail and propose improvements to address the shortcomings observed in the congestion control mechanisms. We carry out simulations to compare the congestion control performance for default CoAP, CoCoA, and our new proposal, CoCoA+, in a variety of network topologies and use cases. The results show that CoCoA+ outperforms default CoAP and achieves better results than CoCoA in the majority of considered cases.