Homoleptic group 12 metal bis(mercaptoimidazolyl)borate complexes M(Bm(R))2 (M = Zn,Cd, Hg)

The sodium salt of the bis(2-mercapto-1-methylimidazolyl)borate anion [Bm(Me)](-) and those of the new bis(2-mercapto-1-alkylimidazolyl)borates [Bm(R)](-) (R = Bz, Bu(t), p-Tol) have been readily obtained from NaBH(4) and the appropriate 2-mercapto-1-alkylimidazoles. To contrast the binding preferences of the group 12 metals in a sulfur-rich environment, the four complete series of homoleptic complexes M[Bm(R)](2) (M = Zn, Cd, Hg), including the first bis(mercaptoimidazolyl)borate derivatives of cadmium and mercury, have been prepared. X-ray diffraction studies of Cd[Bm(Me)](2) and M[Bm(tBu)](2) (M = Zn, Cd, Hg) show the presence of distorted tetrahedral [MS(4)] central cores supplemented by two weak vicinal M.H-B bonds, interactions which appear to be a common feature in the coordination chemistry of Bm(R) ligands. In the case of zinc, it has been found that only in the presence of bulky ligands, as in Zn[Bm(tBu)](2), may an unexpected expansion in the coordination number from four to six be induced. This observation suggests the viability of octahedral intermediates in the processes whereby certain zinc enzymes transfer or exchange metal ions.     

Performance analysis and optimization of a space-time selective PIC for CDMA systems

This paper deals with an efficient receiver for applications in direct sequence-code-division multiple access wireless communication systems. This receiver combines a modified scheme of a parallel interference cancellation detector with antenna arrays with optimum beamforming and is used at the base station for the detection of asynchronous user signals. Each user's transmission channel is assumed to be a multipath frequency-selective independent Rayleigh fading channel. The receiver operates by dividing the signals into reliable and unreliable sets following space-time combining. The reliable signals are detected and canceled from the whole signal received at each sensor. Unreliable signals are then detected to improve the decision reliability. The receiver performance in terms of bit-error probability is analytically derived and optimized. According to the analytical and simulation results, this receiver outperforms previously proposed schemes and, thanks to its low implementation complexity, real-time operation is achieved.     

Downlink cross‐layer scheduling strategies for long‐term evolution and long‐term evolution‐advanced systems

The most recent trend in the Information and Communication Technology world is toward an ever growing demand of mobile heterogeneous services that imply the management of different quality of service requirements and priorities among different type of users. The long‐term evolution (LTE)/LTE‐advanced standards have been introduced aiming to cope with this challenge. In particular, the resource allocation problem in downlink needs to be carefully considered. Herein, a solution is proposed by resorting to a modified multidimensional multiple‐choice knapsack problem modeling, leading to an efficient solution. The proposed algorithm is able to manage different traffic flows taking into account users priority, queues delay, and channel conditions achieving quasi‐optimal performance results with a lower complexity. The numerical results show the effectiveness of the proposed solution with respect to other alternatives. Copyright © 2013 John Wiley & Sons, Ltd.     

AI Based Network and Radio Resource Management in 5G HetNets

The demand for pervasive wireless access and high data rate services are expected to grow significantly in the near future. In this context, the deployment of Heterogeneous Networks (HetNets) will enable important capabilities, such as high data rates and traffic offloading, providing dedicated capacity to homes, enterprises, and urban hotspots. Despite HetNet technology will be beneficial for future wireless systems in many ways, the massive cells diffusion has as a consequence an exponential increase of the backhaul traffic that can create congestion and collapse the backhaul network. Virtualization of networks and radio access allows the implementation of complex and efficient decisional processes for radio and network resource optimization, but the interaction between lower and upper layers during resource allocation decisions is still mostly unexplored. In this paper we propose an artificial intelligence based approach, with two interdependent decisional cores exchanging information, one aware of physical layer aspects and the other controlling pure network resources. The two iterative procedures aim at jointly optimizing the distribution of the traffic in the backhaul network and the users cell association, with the goals of minimizing the unsatisfied users data rate requests and minimizing the energy consumption reducing the number of activated cells, respectively.     

Detection and Mitigation of Impulsive Interference on OFDM Signals Based on Spectrum Sensing,Blanking and Symbol Retransmission

The increasing number of wireless devices and systems operating on the same area leads to significant interference problems that need to be solved. This paper deals with detection and mitigation of the interference generated by an impulsive noise source on an orthogonal frequency division multiplexing system. The idea proposed here is to overcome the interference problem by exploiting the transmission of two replicas of the symbol affected by interference, that are suitably combined at the receiver after a blanking operation of the corrupted samples. An energy detection based sensing scheme is used to reveal the presence of interference. The proposed method allows to efficiently remove the interference without affecting the useful information and exploiting profitably the diversity gain against noise through the soft combining approach. Performance in terms of bit error rate and throughput is compared with the case without mitigation and with the classical blanking method showing a significant improvement. The reduction of the transmission rate, due to the retransmissions, is well compensated by the improvement of the data reliability that leads to an increase of useful data correctly received.