Carlos H. Rentel

Modeling of Zinc Bromide Energy Storage for Vehicular Applications

Energy storage devices such as lithium-ion and nickel-metal hydrate batteries and ultracapacitors have been considered for utilization in plug-in hybrid electric vehicles (HEVs) and HEVs to improve efficiency and performance and reduce gas mileage. In this paper, we analyze and model an advanced energy storage device, namely, zinc bromide, for vehicular applications. This system has high energy and power density, high efficiency, and long life. A series of tests has been conducted on the storage to create an electrical model of the system. The modeling results show that the open-circuit voltage of the battery is a direct function of the batterys state of charge (SOC). In addition, the battery internal resistance is also a function of SOC at constant temperature. A Kalman filtering technique is also designed to adjust the estimated SOC according to battery current.

A clock-sampling mutual network time-synchronization algorithm for wireless ad hoc networks

In this paper, we propose the clock-sampling mutual network synchronization (CSMNS) as a non-hierarchical and mutual network synchronization algorithm for wireless ad hoc networks. CSMNS shows superior performance to the IEEE 802.11 timing synchronization function in terms of accuracy, scalability and robustness. An overall view of the differences between the two approaches is presented. CSMNS is compatible with the beacon messages used in the IEEE 802.11 standard, and it is PHY transparent. CSMNS-RMN (rotating master node) is proposed in order to further reduce beacon collisions and overhead. Stability, is a factor that must be considered in CSMNS. However, values of the proportional gain below 0.3 suggest a good stability performance. The use of larger C/sup max/ values in more dense networks and/or the use of techniques that randomly prioritize the transmission of beacons can further reduce the overhead and risks of instability.

Reed-Solomon and hermitian code-based scheduling protocols for wireless ad hoc networks

In this work we investigate bounds on throughput and delay performance of a scheduling protocol that derives its decisions from codes traditionally used to correct or detect errors in the information carried over a noisy channel. In this paper we study the particular cases in which the Reed-Solomon and Hermitian code constructions are used. It is found that Hermitian codes outperform Reed-Solomon codes in minimum throughput guarantee and delay metrics when the number of nodes is in the order of thousands. The relative minimum distance of the code used to schedule the transmissions is identified as an important property that can be used to identify codes that can enable scheduling patterns with better minimum performance guarantees. Furthermore, the terminology of error control coding is used to present a more general and constructive framework for the study of code-based scheduling protocols.

Bounds and parameter optimization of medium access control coding for wireless ad hoc and sensor networks

Abstract The use of codes to schedule transmissions is an attractive technique able to guarantee a non-zero throughput medium access performance for the nodes of a wireless ad hoc or sensor network regardless of network topology variations. Some authors refer to this technique as topology-transparent scheduling. In this paper, we use the term MAC coding in order to emphasize the exclusive use of codes to achieve topology-transparency within the MAC sub-layer. We present a new upper bound expression on the guaranteed throughput achievable by any linear code used in a MAC coding context. This bound proves to be tighter than the one obtained when the minimum distance of the code is equal to its length. Additionally, we derive new and simple closed analytical expressions for the parameters of maximum distance separable codes that maximize the minimum, average, or joint minimum–average throughput of MAC coding. The optimization methods presented here are also applicable to other codes with available analytical expressions for their minimum distance and distance distribution. Finally, we present system-level simulation results of MAC coding on static and dynamic topologies with mobility and including wireless channel errors. Throughput simulation results are compared with their corresponding analytical expressions and to a random scheduling approach. The results show agreement with analysis and confirm the robustness of MAC coding in maintaining minimum levels of performance with good average performance and graceful degradation.

Clock-Sampling Mutual Network Synchronization for Mobile Multi-hop Wireless Ad Hoc Networks

This paper presents new performance results of a mutual network synchronization approach referred to as Clock-Sampling Mutual Network Synchronization (CS-MNS). Different to other mutual synchronization approaches, CS-MNS timing information is exchanged explicitly using periodic packets referred to as beacons, which are used to carry timestamps, and hence compatibility to the widely adopted IEEE 802.11 standard is ensured, even for mobile multi-hop wireless ad hoc networks. Performance results are presented for two mobility models and large networks. Numerical comparisons demonstrate at least one to two orders of magnitude improvement in scalability and accuracy respectively relative to the IEEE 802.11 synchronization mechanism. CS-MNS also shows approximately five times better accuracy than the reported accuracies of the MANET-TSF (MATSF) and ASP under similar mobility and radio transmission range conditions.