A Study On Energy Efficient Multi-Tier Multi-Hop Wireless Sensor Networks For Freight-Train Monitoring

The North American freight railroad industry is trying to leverage wireless sensor networks (WSN) onboard railcars for advanced monitoring and alerting. In railroad environments, freight train WSNs exhibit a linear chain-like topology of significant length. Thus, existing wireless technologies such as the IEEE 802.15.4 communication protocol, based on a star topology, are unable to provide reliable service. The end-to-end communication between nodes generally relies on individual nodes communicating with their respective neighbors to carry the information over multiple hops and deliver it to the preferred destination. The routing performance and reliability significantly degrades with increasing number of hops. We proposed a multitier multi-hop network which is designed to overcome these issues in large-scale multi-hop WSNs in railroad environments. This approach has significant advantages, such as more data bandwidth, higher reliability, and lower energy consumption. Our analytical results show that the proposed multi-tier communication approach spends energy more efficiently and utilizes less resource than the traditional chain topology on board freight trains

Performance Analysis for Direction of Arrival Estimating Algorithms

Smart antennas have emerged as one of the most promising directions in supporting maximum communication link throughput. In this paper, we have investigated the impact of smart antennas on a complex mobile network such as a railroad wireless communications system. The objective is to analyze the selection of a Direction-Of-Arrival (DOA) estimation algorithm which provides the maximum efficiency when deployed in our railroad testbeds for wireless vehicular communication. Our findings are discussed to provide an indepth understanding of how different algorithms should be selected to support efficient network operations

Priority Preemption for Real-time Application QoS Guarantees in Cooperative Vehicular Networks

Inter-vehicle and roadside-to-vehicle communications can contribute to a safer and more efficient driving experience by providing time-sensitive and location-aware information. However, its performance suffers from vehicle mobility, intermittent user connectivity, and wireless channel unreliability. In this paper, we propose a novel cross-layer optimization approach based on our Adaptive Distributed Cooperative Medium Access Control (ADC-MAC) protocol to guarantee the quality-of-service (QoS) of real-time applications. Markov chain based theoretical analysis show that our proposed priority preemption approach can improve the quality of a real-time application by guaranteeing its bandwidth and reducing its transmission latency

Study of a novel peak restoration technique to optimize OFDM receiver performance in the presence of peak -to -average power ratio signal distortion

Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation scheme utilized as a modulation method in high speed wireless and mobile communications systems such as digital subscriber lines, wireless LANs, digital video broadcasting, WiMAX and other emerging wireless broadband systems, including LTE. However, one major drawback of OFDM is its inherently high peak-to-average power ratio (PAPR), which can cause severe nonlinear distortion when a nonlinear high power amplifier (HPA) is used. High PAPR is one of the most important implementation challenges in OFDM schemes, because it reduces the efficiency and hence increases the cost of the radio frequency (RF) power amplifier, which is one of the most expensive components in a radio. This dissertation proposes a novel approach to minimize the impact of PAPR. Most current PAPR reduction techniques aim to minimize PAPR in the transmitter; the work presented here studies PAPR reduction techniques in the receiver and their effects on the performance of OFDM systems. Extensive analysis was performed to compare the performance gain of each reduction technique. The results obtained in different channels such as SISO and MIMO show that the new peak restoration technique achieves a four-fold performance improvement on average in the SISO channel, and it can support other previously published approaches as well

Le chiuse: realtà e rappresentazioni mentali del confine alpino nel medioevo

Throughput vs. distance analysis and coverage requirements are critical issues in planning wireless network deployments. With the recent availability of IEEE 802.16e and its promise of larger coverage areas for high-speed data communication, evaluating it in a real-world environment is very important to us in our ongoing study of standards based wireless technologies for the Federal Railroad Administration (FRA). In this paper, we present results obtained with our IEEE 802.16e module for NS-2, particularly throughput vs. distance performance, and its consideration for designing a real-world multi-hop IEEE 802.16e testbed. Firstly, a quantitative analysis of throughput vs. distance performance is conducted via extensive simulation, and the optimal modulation and coding scheme as well as channel bandwidth profiles are identified for specific distances. Secondly, we present a real-world multi-hop IEEE 802.16e testbed design intended for installation along BNSF Railway track in Nebraska. We apply our findings towards selecting various base station deployment locations and their appropriate communications parameters in order achieve best possible multi-hop throughput performance. We also provide a client access coverage analysis for the various locations

Quantitative Performance Analysis of 3.65 GHz Mobile WiMAX

3.65 GHz Mobile WiMAX spectrum is often a better commercial solution due to its attractive licensing requirements, in spite of the slightly lower coverage area. However, no significant performance data has been reported for 3.65 GHz equipment behavior. In this paper, we have presented an in depth analysis of a 3.65 GHz Mobile WiMAX solution. Our reported data can also contribute in performing link budget analyses and benchmarking similar equipment

A Performance Comparison of Mobile WiMAX Spectrums: 2.5 GHz vs. 3.65 GHz

Mobile WiMAX is a popular broadband solution with diverse applications. In the United States, the Federal Communications Commission (FCC) currently issues licenses for Mobile WiMAX in several frequency bands, of which 2.5 GHz and 3.65 GHz are the most prevalent. A significant amount of research has been conducted in the domain of 2.5 GHz due to its widespread commercial use. However, no such work – academic or industrial – has been reported for 3.65 GHz, in spite of it being a more favorable option for many applications, particularly because of its licensing requirements. In this paper, we present a comprehensive comparison of these two frequency bands in order to provide benchmark results for use by network planners, engineers and researchers. Our analysis indicates that, while 2.5 GHz Mobile WiMAX generally offers a larger coverage area, the attractive licensing options for 3.65 GHz may present an interesting alternative for many deployment scenarios and applications

Quantitative Analysis of Propagation Characteristics for Mobile WiMAX

In wireless networks, careful planning and link budget analysis is required for delivering maximum throughput reliably with minimum overhead. The efficiency of planning and eventual network performance is totally dependent upon the accuracy and quality of data used for analysis. In most studies, computer simulations and analytical models are used for generating such data. However these simulations are limited to many assumptions which are different from the actual implemented hardware, therefore, the data generated are not accurate. In this paper, we analyze the performance of Mobile WiMAX utilizing the empirical data measured from leading WiMAX equipment. We believe this data can be used to predict an accurate and reliable throughput and link budget in WiMAX networks

Mobile WiMAX Throughput and Delay Measurements in Railroad Environment

The railroad industry in North America is heavily involved in improving the broadband wireless connectivity of their railroad operations. We propose our approach of establishing a Mobile WiMAX test bed as a part of our collaborations with the Federal Railroad Administration (FRA) for investigating the performance of current and upcoming broadband wireless technologies in a railroad environment. The focus is on studying the impact of mobility on the wireless system throughput for moving trains at high velocities. Our goal is to provide a comprehensive measurement that will assist others in understanding Mobile WiMAX performance and guiding future network deployment. In this paper, we describe details of our test bed and discuss test results obtained from our laboratory and test bed. Based on our measurements, we can achieve a throughput of approximately 2.8 Mbps downlink and 2 Mbps uplink with the most robust modulation scheme, a maximum distance of 7.5 kilometers, and a speed of 60 mph, making Mobile WiMAX a promising candidate for large-scale deployments in environments such as the railroad industry

A Cross-Layer Parallel Handover Optimization Scheme for WiMAX Networks

The handover performance plays a crucial role in guaranteeing the quality of real-time applications in WiMAX networks. In general, a handover process can be divided into four stages: i) cell reselection, ii) handover preparation, iii) link layer handover, and iv) IP layer handover. A cross-layer parallel handover optimization (CPHO) scheme is proposed in this paper to reduce the handover signaling overhead and latency in each stage. The key idea of our proposed scheme is that uses the knowledge achieved from the backhaul inter-BS communications to reduce the HO control message load in wireless links and overlaps the executions of the link layer and the network layer handover process. Therefore the mean of the handover interruption time can be significantly reduced. The numerical analysis and simulation results show that the proposed approach significantly enhances the handover performance