This paper studies interference alignment scheme and minimum mean square error (MMSE) improvement in Internet of Things (IoT)-oriented cognitive systems, where IoT devices share the licensed spectrum by cognitive radio in spectrum underlay. Target to manage the intertier interference caused by cognitive spectrum sharing as well as ensure an MMSE at receivers, the interference alignment algorithms is proposed. In particular, we focus on the problem of designing the optimal linear pre-coding to minimize the total mean square error while satisfying transmit power constraints. Firstly, we introduce a system model of the downlink IoT-oriented cognitive multi-input multi-output (MIMO) system. Secondly, we propose an interference nulling based cognitive interference alignment scheme, and then, the pre-coding and post-coding matrix designs for the primary Transceivers to minimum mean square error (MSE), as well as to eliminate the cochannel interference to the primary receivers. We also apply these interference alignment scheme and matrix designs for the secondary links. Finally, the numerical results are used to evaluate performance of the proposed algorithm.

This study presents modeling and simulation of a stand-alone hybrid energy system for a base Transceiverstation (BTS). The system is consisted of a wind and turbine photovoltaic (PV) panels as renewableresources, and also batteries to store excess energy in order to boost the system reliability. Two differenttypes of batteries are considered for storage purposes; lead-acid and vanadium redox-flow batteries (VRB)batteries. Most stand-alone energy systems for various applications take advantage of at least a singlestorage technology, generally lead-acid batteries. However, with recent advances in different batterytechnologies, vanadium redox-flow batteries could be taken into account as reliable candidate. Thevanadium redox-flow battery has a desirable prospect due to its extended life span and also the potentialfor separating and scaling up involved nominal power and nominal energy. The system is modelled andsimulated hourly (quasi-dynamically) in Matlab for an operational year. The model utilizes insolation,wind speed and air temperature data. The system performance has been assessed with a mobile telephoneBase Transceiver Stations (BTS) as the case study. Simulations results have shown that the suggestedmodel can be used to study the effect of the altering weather conditions on each charge/discharge cyclesand batteries voltage. Finally the proposed model yields the optimal battery network design for a varietyof applications.

This paper addresses a novel Alamouti space-frequency block decoding scheme with discontinuous Doppler diversity (DDoD) and cyclic delay diversity (CDD). We investigate different antenna diversity concepts, which can be applied to orthogonal frequency division multiplexing (OFDM) systems over highly frequency selective channels. The main object of this research is standard compatibility and the effect of simple diversity techniques on the channel fading properties. Therefore, we analyze a receiver in terms of the effective channel transfer function, which leads to the possibility of optimizing diversity. Besides, a novel Transceiver using DDoD is proposed, which increases the Doppler spread of the multipath fading channel without causing additional Intercarrier Interference (ICI). Moreover, an efficient Alamouti encoder and decoder based on CDD is proposed, which allows a high reliability and capacity enhancement. In order to evaluate the capability of that, we have implemented this scheme for the second-generation terrestrial video broadcasting (DVB-T2) system over different channels. Furthermore, mathematical analysis and simulation results show the bit error performance of the modified encoding method with these diversity techniques, performs mostly better than the other forms of encoding Alamouti over highly frequency-selective channels such as single frequency networks (SFN). The other advantages of the proposed method are simplicity, flexibility, and standard compatibility.