The interacting generalized Ricci dark energy model in non-flat universe

We extend our previous analysis and consider the interacting holographic Ricci dark energy (IRDE) model in non-flat universe. We study astrophysical constraints on this model using the recent observations including the type Ia supernovae (SNIa), the baryon acoustic oscillation (BAO), the cosmic microwave background (CMB) anisotropy, and the Hubble parameter. It is shown that the allowed parameter range for the fractional energy density of the curvature is $-0.005$ $\lesssim$ $\Omega_{k0}$ $\lesssim$ $0.015$ in the presence of the interactions between dark energy and matter. Without the interaction, the flat universe is observationally disfavored in this model.Comment: 9 pages, 3 figure

Impulse Radio Systems with Multiple Types of Ultra-Wideband Pulses

Spectral properties and performance of multi-pulse impulse radio ultra-wideband systems with pulse-based polarity randomization are analyzed. Instead of a single type of pulse transmitted in each frame, multiple types of pulses are considered, which is shown to reduce the effects of multiple-access interference. First, the spectral properties of a multi-pulse impulse radio system is investigated. It is shown that the power spectral density is the average of spectral contents of different pulse shapes. Then, approximate closed-form expressions for bit error probability of a multi-pulse impulse radio system are derived for RAKE receivers in asynchronous multiuser environments. The theoretical and simulation results indicate that impulse radio systems that are more robust against multiple-access interference than a "classical" impulse radio system can be designed with multiple types of ultra-wideband pulses.Comment: To be presented at the 2005 Conference on Information Sciences and System

A Genetic Algorithm Based Finger Selection Scheme for UWB MMSE Rake Receivers

Due to a large number of multipath components in a typical ultra wideband (UWB) system, selective Rake (SRake) receivers, which combine energy from a subset of multipath components, are commonly employed. In order to optimize system performance, an optimal selection of multipath components to be employed at fingers of an SRake receiver needs to be considered. In this paper, this finger selection problem is investigated for a minimum mean square error (MMSE) UWB SRake receiver. Since the optimal solution is NP hard, a genetic algorithm (GA) based iterative scheme is proposed, which can achieve near-optimal performance after a reasonable number of iterations. Simulation results are presented to compare the performance of the proposed finger selection algorithm with those of the conventional and optimal schemes.Comment: To appear in the Proc. IEEE International Conference on Ultrawideband (ICU-2005

Optimal and Suboptimal Finger Selection Algorithms for MMSE Rake Receivers in Impulse Radio Ultra-Wideband Systems

Convex relaxations of the optimal finger selection algorithm are proposed for a minimum mean square error (MMSE) Rake receiver in an impulse radio ultra-wideband system. First, the optimal finger selection problem is formulated as an integer programming problem with a non-convex objective function. Then, the objective function is approximated by a convex function and the integer programming problem is solved by means of constraint relaxation techniques. The proposed algorithms are suboptimal due to the approximate objective function and the constraint relaxation steps. However, they can be used in conjunction with the conventional finger selection algorithm, which is suboptimal on its own since it ignores the correlation between multipath components, to obtain performances reasonably close to that of the optimal scheme that cannot be implemented in practice due to its complexity. The proposed algorithms leverage convexity of the optimization problem formulations, which is the watershed between `easy' and `difficult' optimization problems.Comment: To appear in IEEE Wireless Communications and Networking Conference (WCNC 2005), New Orleans, LA, March 13-17, 200

Estimation on Possibility and Capacity of Residential Peak Electricity Demand Reduction by Demand Response Scenario in Rural Areas of Japan

AbstractThis study analyzes the potential peak demand reduction based on actual measurement result and outage scenarios acceptable to rural residential customers in Japan. To obtain the actual demand, load measurement was carried out on 18 households in Tsuru and 8 households in Izu during a week in winter, spring, and summer. The measurement result shows that the maximum demand in both areas occurred in winter. Daily aggregate peak demands extracted from the measurement were then modelled using Lognormal and Weibull distribution to obtain the probability of outage in any system's peak capacity value. On the other hand, to gauge the outage scenario that is acceptable to electricity consumers, an outage scenario representing an extremely rare case was selected from a nationwide survey. The survey result shows that six 2-hour outages per year with annual bill reduction of JPY30,000 is a feasible scenario. The modelling demonstrates that this scenario can result in 10.2% peak demand reduction in Tsuru and 5.2% peak demand reduction in Izu. The result of this study may be beneficial for distributed power system designers to determine optimum power system capacity as well as demand response programs acceptable to rural residential customers