The Internet of Things (IoT) is an emerging key technology for future industries and everyday lives of people, where a myriad of battery operated sensors, actuators, and smart objects are connected to the Internet to provide services such as mobile healthcare, intelligent transport system, environmental monitoring, etc. Since energy efficiency is of utmost importance to these battery constrained IoT devices, IoT-related standards and research works have focused on the device energy conserving issues. This paper presents a comprehensive survey on energy conserving issues and solutions in using diverse wireless radio access technologies for IoT connectivity, e.g., the 3rd Generation Partnership Project (3GPP) machine type communications, IEEE 802.11ah, Bluetooth Low Energy (BLE), and Z-Wave. We look into the literature in broad areas of standardization, academic research, and industry development, and structurally summarize the energy conserving solutions based on several technical criteria. We also propose future research directions regarding energy conserving issues in wireless networking-based IoT.

Multicasting is an efficient mechanism to disseminate popular multimedia content to multiple interested third generation partnership project (3GPP) cellular users. To further enhance the multicast cellular capacity, non-3GPP WLAN networks can be leveraged to relieve the load of the 3GPP cellular networks. In this paper, we propose the distributed procedure of de-touring the multicast traffic to WLAN in the current LTE and WLAN heterogeneous network architecture. We also propose promising software-defined networking (SDN)-based centralized approach that facilitates multicast content dissemination, bringing efficiency and flexibility to the network. We analyze both the distributed and centralized approaches based on the multicast content popularity. Our analysis reveals that the SDN-based approach in heterogeneous cellular communication and multicasting brings significant radio resource savings. We also conduct packet-level simulation with a real SDN controller and smartphones to confirm the feasibility of the proposed SDN-based approach.

In this paper, we analyze the performance of a dual-hop cooperative decode-and-forward (DF) relaying system with beamforming under different adaptive transmission techniques over $\kappa -\mu$ shadowed fading channels. We consider multiple antennas at the source and destination, and communication takes place via a single antenna relay. The published work in the literature emphasized the performance analysis of dual-hop DF relaying systems, in conjunction with different adaptive transmission techniques for classical fading channels. However, in a real scenario, shadowing of the line-of-sight (LoS) signal is caused by complete or partially blockage of the LoS by environmental factors such as trees, buildings, mountains, etc., therefore, transmission links may suffer from fading as well as shadowing, either concurrently or separately. Hence, the $\kappa -\mu$ shadowed fading model was introduced to emulate such general channel conditions. The $\kappa -\mu$ shadowed fading model is a general fading model that can perfectly model the fading and shadowing effects of the wireless channel in a LoS propagation environment, and it includes some classical fading models as special cases, such as $\kappa -\mu$ , Rician, Rician-shadowed, Nakagami- $\widehat{m}$ , One-sided Gaussian, and Rayleigh fading. In this work, we derive the outage probability and average capacity expressions in an analytical form for different adaptive transmission techniques: (1) optimal power and rate adaptation (OPRA); (2) optimal rate adaptation and constant transmit power (ORA); (3) channel inversion with a fixed rate (CIFR); and (4) truncated channel inversion with a fixed rate (TIFR). We evaluate the system performance for different arrangements of antennas and for different fading and shadowing parameters. The obtained analytical expressions are verified through extensive Monte Carlo simulations.