Diffusive MIMO Molecular Communications: Channel Estimation, Equalization and Detection

In diffusion-based communication, as for molecular systems, the achievable data rate is low due to the stochastic nature of diffusion which exhibits a severe inter-symbol-interference (ISI). Multiple-Input Multiple-Output (MIMO) multiplexing improves the data rate at the expense of an inter-link interference (ILI). This paper investigates training-based channel estimation schemes for diffusive MIMO (D-MIMO) systems and corresponding equalization methods. Maximum likelihood and least-squares estimators of mean channel are derived, and the training sequence is designed to minimize the mean square error (MSE). Numerical validations in terms of MSE are compared with Cramer-Rao bound derived herein. Equalization is based on decision feedback equalizer (DFE) structure as this is effective in mitigating diffusive ISI/ILI. Zero-forcing, minimum MSE and least-squares criteria have been paired to DFE, and their performances are evaluated in terms of bit error probability. Since D-MIMO systems are severely affected by the ILI because of short transmitters inter-distance, D-MIMO time interleaving is exploited as countermeasure to mitigate the ILI with remarkable performance improvements. The feasibility of a block-type communication including training and data equalization is explored for D-MIMO, and system-level performances are numerically derived.Comment: Accepted paper at IEEE transaction on Communicatio

Motorcycle Potential Problems in Jakarta

After the economic crisis in 1997, motorcycles become a popular transport mode in Indonesian cities.However this condition leads to large number of violation and accident rate. This study tried to discuss howthis problem started and what possible measure can be taken to solve the problems, mainly based on literaturereview. The traffic data used were compiled from the data provided by PT Pamintori Cipta. Interview surveywas conducted to find people perception of motorcycles issues. The conclusion suggests that there is a needof further comprehensive study to find out what condition that makes motorcyclists voluntary return to usepublic transport and social engineering and intensive training program should be implemented for youngergeneration to improve traffic condition in Jakarta

A robust loop-shaping approach to fast and accurate nanopositioning

Peer reviewedPreprin

Complexity Growth Following Multiple Shocks

In this paper by making use of the "Complexity=Action" proposal, we study the complexity growth after shock waves in holographic field theories. We consider both double black hole-Vaidya and AdS-Vaidya with multiple shocks geometries. We find that the Lloyd's bound is respected during the thermalization process in each of these geometries and at the late time, the complexity growth saturates to the value which is proportional to the energy of the final state. We conclude that the saturation value of complexity growth rate is independent of the initial temperature and in the case of thermal initial state, the rate of complexity is always less than the value for the vacuum initial state such that considering multiple shocks it gets more smaller. Our results indicate that by increasing the temperature of the initial state, the corresponding rate of complexity growth starts far from final saturation rate value.Comment: 19 pages, 3 figs, Ref.s adde

Ruderman-Kittel-Kasuya-Yosida interaction in biased bilayer graphene

We study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two contact magnetic impurities placed on bilayer graphene (BLG). We compute the interaction mediated by the carriers of the pristine and biased BLG as well as the conduction electrons of the doped system. The results are obtained from the linear-response expression for the susceptibility written in terms of the integral over lattice Green's functions. For the unbiased system, we obtain some analytical expressions in terms of the Meijer G-functions, which consist of the product of two oscillatory terms, one coming from the interference between the two Dirac points and the second coming from the Fermi momentum. In particular, for the undoped BLG, the system exhibits the RKKY interaction commensurate with its bipartite nature as expected from the particle-hole symmetry of the system. Furthermore, we explore a beating pattern of oscillations of the RKKY interaction in a highly doped BLG system within the four-band continuum model. Besides, we discuss the discrepancy between the short-range RKKY interaction calculated from the two-band model and that obtained from the four-band continuum model. The final results for the applied gate voltage are obtained numerically and are fitted with the functional forms based on the results for the unbiased case. In this case, we show that the long-range behavior is scaled with a momentum that depends on Fermi energy and gate voltage, allowing the possibility of tuning of the RKKY interaction by gate voltage.Comment: 13 pages, 6 figure