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In this correspondence, we present a novel soft-output-sparse-aware (SOSA) detector for an uplink multiuser multiple-input-multiple-output system. The proposed detector consists of two steps: First, a transmit vector is detected using a low-complexity detector; second, an improved soft-output is generated by exploiting the sparsity of a residual error vector (i.e., the difference between the transmit vector and the detected one). In contrast, the previous sparse-aware (SA) detectors used the sparsity to refine the hard-decision output of the underlying detector. Therefore, the SOSA detector can significantly outperforms the (hard-output) SA detectors for the coded systems since the former only can be well-incorporated into state-of-the-art soft channel decoders. Via simulation results, we demonstrate that the SOSA detector attains a nontrivial coded gain over the (soft-output) underlying detector with a similar complexity. Furthermore, the performance gap grows as signal-to-noise ratio and a system size grow.

In this letter, we propose a novel detector, called the sparse-aware minimum mean square error (SA-MMSE) detector, to improve detection performance for multiple input multiple output (MIMO) systems. We first convert a conventional MIMO system into a sparse system via the symbol error vector obtained from a linear detector. Then, we develop a new sparse refining method, which has a similar structure as the linear MMSE detector, to improve the detection performance. The proposed SA-MMSE detector can be performed iteratively and has low complexity similar to that of the parallel interference cancellation (PIC). Simulation results show that the SA-MMSE detector outperforms the compressive-sensing-based detector and PIC with a similar complexity, especially when the numbers of users and antennas become large.

We consider the problem of joint power allocation (JPA) in a coordinated multi-point (CoMP) joint diversity transmission (JDT) network with a total coordination point power (TCPP) constraint, aimed at maximizing the ergodic cooperative capacity (ECC) in Rayleigh fading channels. In this paper, we first extend the JPA problem in the coordinated two-point (Co2P) JDT networkto the case of a non-unity TCPP constraint. Furthermore, we introduce more accurate log-quadratic approximated (LQA) expressions to obtain the coordinated transmission point (CTP) powers. Next, we extend our study to a coordinated three-point (Co3P) JDT network. Given the mean branch gain-to-noise ratios, we first obtain a log-linear approximated (LLA) expression for obtaining the optimum power of the third CTP (i.e., the worst quality-providing CTP). After obtaining the third-CTP power, we obtain the CTP powers of two better quality-providing CTPs by invoking the LLA CTP power expressions for Co2P JDT power allocation, under the remaining power given by the TCPP minus the third-CTP power. The numerical results demonstrate that the LQA and LLA CTP power expressions for Co2P JDT and the LLA CTP power expressions for Co3P JDT are very efficient in terms of the simplicity for JPA and CoMP set selection, as well as the resulting ECC.

To meet the growing needs from a variety of stakeholders, the development of modern systems is getting more complex and thus, the systems failure in the actual operations can potentially become more serious. This is why several international or military standards on systems safety have been published. In spite of the importance of meeting those standards such as IEC 61508 and ISO 26262 in the systems development, the associated practical methods seem deficient since those standards do not provide them. The objective of this paper is to present a method to identify potential hazards in fulfilling the requirements of the safety standards. In particular, the approach taken here is based on applying the functional analysis that covers several levels of the system under development. Note, however, that in the most of the conventional methods for hazards identification, the analysis has been focused on the failure at or underneath the component level of the system. The hazards identification method in this paper would cover the level up to the system by utilizing the functions-oriented approach. The case study of the safety enhancement for locomotive cabs is also discussed.

In this paper, an exponential model of Korea is proposed to minimize an altitude-error of high-altitude target due to atmosphere refraction at radar system. The relation between surface refractivity and refractivity gradient, which is extracted using the least square fit from the measured data at 7 weather stations, is applied to the exponential model. And in order to verify the proposed model, the altitude-errors for a standard atmosphere, a CRPL(Central Radio Propagation Lab.) exponential model, the proposed model are extracted and analyzed using a ray tracing. As a result, the proposed model can improve the altitude estimation performance of radar compared to conventional atmosphere refractive index models.