Radio Channel Propagation Characterization and Link Reliability Estimation in Shadowed Suburban Macrocells

The amount of mobile video streaming traffic is rapidly growing and a potential candidate to reduce the load on the content delivery infrastructure is given by the peer-to-peer (P2P) paradigm. One might argue about the adequacy of P2P in this mobile context, yet, it has already become reality. Popular P2P streaming networks like SopCast or TVU networks have recently deployed their apps for mobile devices. In this paper the current state of a location-aware measurement framework is presented, which was mainly developed to evaluate P2P systems in cellular networks. We use our generic framework to present the first measurement study that investigates the behavior of the popular P2P video streaming application SopCast when it is operating in a UMTS High Speed Packet Access (HSPA) network and compare the results with reference Ethernet measurements. The aim of this study is to discover the impact of cellular networks and user mobility on the performance of such P2P applications. In particular we could observe that as consequence some of the drawbacks are characterized by poor connectivity among peers and negligible upload contributions.

Due to the fast evolution of mobile devices, a high penetration of notebooks and smart-phones, and the growing demand for high rate services, e.g. mobile video and P2P services, modern radio access networks require efficient means for call admission control and radio resource management. In particular, network operators, managing co-deployed, heterogeneous access technologies, are interested in an optimized utilization of their infrastructure while maximizing their revenue. For ensuring maximum operator gain and optimized system performance, we propose to handle diverse user service requests, ranging from voice only to bandwidth-consuming streaming services, collaboratively by a combined, heuristic Joint Call Admission Control (JCAC) and Dynamic Bandwidth Adaptation (DBA) approach. This approach aims at maximizing overall system utilization and, hence, the mobile network operator's revenues, while keeping the blocking and dropping rates at acceptably low levels, and ensuring that Quality of Service (QoS) demands of the diverse services are met. Therefore, we introduce a novel utility definition of services which is used in the proposed algorithms. It represents a generic measurement of the profit that is gained by the mobile network operator. The JCAC and DBA algorithms are realized tightly coupled and ensure that a maximum number of requested services can be supported by the cooperatively managed, wireless systems in the considered service area. Further, system utilization is optimized by improving the QoS characteristics of the already granted elastic services. In order to evaluate the algorithms for a given scenario of co-deployed Long Term Evolution (LTE) and High Speed Packet Access (HSPA) network nodes, an event-driven simulation platform based on OMNeT++ has been developed, including all relevant entities of 3GPP's SAE. The results show an improvement in the overall gained utility of the mobile network operator compared to standard approaches, and optimized system performance w.r.t. utilization as well as acceptable low blocking and dropping rates.

In a cellular network, connections between the Base Station (BS) and Mobile Stations (MS) may fail when the channel is in a deep fade. Shadow fading is large-scale fading which can cause significant received power loss for a wide area. This will lead to lost connections and/or packet loss which is harmful to mobile users, especially to those who are using real-time applications such as video conferencing. Cooperative communication is an efficient way to reduce outage and provide better Quality of Service (QoS) support for delay sensitive applications. A third station, which is often referred as a relay, can be used to forward signals between the BS and the MS. This paper focuses on a study of the performance of relay deployments under correlated shadow fading. We consider the downlink direction in a single cell deployment, for which the shadowing effect is modeled as an angle and distance based correlated shadowing. The received signal-to- noise ratio (SNR) is then calculated by assuming jointly Gaussian shadow fading at the MS. Simulation results show channel variations over time with fixed user speed under different relay deployments. These results demonstrate that a modest number of relays can improve the performance of real-time applications significantly.

The demand for faster internet connections to access wireless multimedia applications, Aeronautical Communication Networks (ACNs) and internet services has resulted into rise of developing broadband wireless technologies in recent years. The demand for higher data rates was the backbone for developing wireless communication technologies such as Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE) and High-Speed Packet Access (HSPA). The big challenge with wireless communications lies with providing Quality of Service (QoS) under various environmental challenges and maximizing resource utilization at the same time. In wireless communication, the support for QoS is difficult due to the unpredictable nature of wireless channels. Opportunistic Scheduling plays a big role towards meeting QoS requirements and managing resources in aeronautical communication networks. Various opportunistic schedulers focus on increasing the system capacity of a wireless communication network, while some aim on improving the system’s fairness and throughput. With such interest in opportunistic scheduling, the paper focuses on reviewing recently proposed opportunistic scheduling algorithms, the objectives they were designed for, and their shortcomings. An effective opportunistic scheduling algorithm with hierarchical modulation technique is presented in this paper. The algorithm focuses on the ability to allocate resources between two users with different channel conditions; that is a user with good channel conditions and a user with bad channel conditions, to maximize the system’s throughput and maintain fairness.

The probabilistic reliability estimation of complex system is complicated due to uncertainty of failure data, modeling or human failure. In this paper, reliability of components of complex network system is considered as fuzzy in nature to reduce the uncertainty. Trapezoidal fuzzy number is used to represent component's reliability of network system. Then the reliability of the network system is assembled with fuzzy reliability of components and evaluated by Zadeh's extension principle. Fuzzy reliability of the network system becomes an interval by α-cuts operation. Interval nonlinear programming is used to evaluate the optimum network's system reliability with interval valued cost constraint. The above approach is explained in details through a numerical example of very useful power system network of electrical engineering.

Satellite communication networks with onboard processing (OBP) satellites can provide high-speed data transmission rates and global service coverage with reduced propagation delays. This article proposes a means of analyzing the quantitative reliability of the satellite communication network systems. First, we identify the four major factors that affect the quality of network services: the OBP states, uplink channels, downlink channels, and uplink packet collision losses. Based on these four factors, a Markov model is derived to analyze the probability distributions of various network states. Analytic results show the network reliability with respect to the OBP structures and space radiation environments. The relationship between network reliability and throughput according to the packet traffic load is also quantitatively analyzed. Finally, based on the developed model, a method is suggested for iteratively updating the reliability distribution of network systems affected by changes in the four factors as well as network access time changes. The numerical results show an indication of the satellite network reliability to provide references whether adjusted elements of the four factors are eligible to sustain reliable end-to-end services.

Wave propagation characteristics in curved tunnels are of importance for designing reliable communications in subway systems. This paper presents the extensive propagation measurements conducted in two typical types of subway tunnels—traditional arched “Type I” tunnel and modern arched “Type II” tunnel—with 300- and 500-m radii of curvature with different configurations—horizontal and vertical polarizations at 920, 2400, and 5705 MHz, respectively. Based on the measurements, statistical metrics of propagation loss and shadow fading (path-loss exponent, shadow fading distribution, autocorrelation, and crosscorrelation) in all the measurement cases are extracted. Then, the large-scale fading characteristics in the curved subway tunnels are compared with the cases of road and railway tunnels, the other main rail traffic scenarios, and some “typical” scenarios to give a comprehensive insight into the propagation in various scenarios where the intelligent transportation systems are deployed. Moreover, for each of the large-scale fading parameters, extensive analysis and discussions are made to reflect the physical laws behind the observations. The quantitative results and findings are useful to realize intelligent transportation systems in the subway system.

In this paper an innovative Radio Resource Management (RRM) algorithm is proposed with the purpose of increasing High Speed Packet Access (HSPA) performances, in terms of system capacity and service quality, when the Multimedia Broadcast Multicast Services (MBMS) is supplied. The proposed RRM algorithm exploits channel quality indications to set up point-to-multipoint connections to subgroups of multicast users and to select the proper modulation and coding schemes on the downlink. The number of subgroups is determined through an optimization technique that also takes into account the user satisfaction. An exhaustive simulation campaign is conducted to compare the proposed algorithm with the most promising approaches in the literature. Comparisons aim to assess the capability of the proposed RRM algorithm to efficiently manage group oriented services by providing an increment in terms of user satisfaction.

In this paper, we present analytical models for the probability density function (PDF) of link life time and link reliability probability in vehicular ad hoc networks (VANETs), formed on single lane highways in free flow traffic state. Assuming the vehicle velocity to have Gaussian probability distribution we investigate the impact of vehicle mobility, path loss exponent and shadow fading on the link life time PDF and the mean link life time in VANETs. Our analytical and simulation results suggest that, in the free flow uncongested traffic state in which vehicle speed has Gaussian probability distribution, the link duration PDF can be approximated as lognormal with appropriate parametrization. We present the Kolmogorov-Smirnov goodness-of-fit test results to justify this claim. Further, we present a probabilistic model for link reliability in VANETs.

Received signal power in mobile wireless communications is typically modeled as a product of three factors: distance-dependent average path loss law, variation in the local mean power (shadow fading), and small-scale fading. Of these three factors, the least investigated is the shadow fading, which is usually explained as a result of multiplication of large number of random attenuating factors in the radio channel. In this paper, the authors propose an additive model as an alternative physical basis for shadow fading within an extended local area where path loss is constant. Starting from a sum-of-sinusoids signal model, they show that under mild statistical assumptions on the powers of the sinusoids, the resulting signal power will have approximately Gaussian distribution in logarithmic scale. A cluster-based model for shadow fading emerges as a special instance of the general result. They present simulation and measurement results that support their theoretical findings. The new physical basis for shadow fading also provides insights into simulation and modeling of radio channels

Recently, computation, communication and control are deeply and pervasively embedded into physical and engineered components of network System, to advance entire networked system performance and dependability. In such systems, the growing complexity of network structure result in need of increasing system reliability. Network reliability modeling and analysis need not only capture the complex dynamic process of network systems, but also need the facilities for applying, understanding and computing. The objective of this paper is to develop a suitable modeling and analysis framework to study the ad-hoc network reliability. Using the mutual transformations of reliability functions between the time-domain and the frequency-domain, we adopt frequency-domain analysis approach to model network reliability. The advantages of the proposed approach over the traditional time-domain approaches include capability to capture higher order moments of system characteristics, scalability to analyze reliability of complex network systems, efficiency in calculation and practicability in computer simulation, etc. Finally, numerical experiment results show the feasibility and efficacy of this approach.

The reliability of network systems of various structures has been studied by many researchers. However, most of the works just consider the reliability of a single network system. In practice, different networks may be interdependent such that the failure in one network may result in the failure in another network. The cascading failures have been shown to be catastrophic by some researchers. However, the quantitative evaluation for the reliability of interdependent networks has not been proposed. In this paper, a multi-valued decision diagram based approach is presented to evaluate the reliability of interdependent networks. Illustrative examples are proposed to demonstrate the application of the framework.

The exact calculation of all-terminal network reliability is an NP-hard problem, with computational effort growing exponentially with the number of nodes and links in a network. Because of the impracticality of calculating all terminal network reliability for networks of moderate to large size, Monte Carlo simulation methods to estimate network reliability and upper and lower bounds to bound reliability have been used as alternatives. In this study, an artificial neural network (ANN) is used to estimate all-terminal network reliability for networks with both homogeneous link reliability. Two forms of design methods for generating training data sets for networks with homogeneous and heterogeneous link reliability are compared. These experimental design and randomized design.

In view of the effect of DGs uncertainty on the reliability of the distribution network system, an integrated Markov model is put forward to evaluate the reliability of distribution network, considering the randomness of DG, DG mechanical failure rate and starting/switching refuse rate and other factors; In view of the randomness of the output of photovoltaic power, using the Cornish Fisher expansion method to generate the standard normal distribution of sample space in order to further analysis the effects of illumination intensity correlation coefficient of distribution system reliability. Through the simulation analysis of BUS6 IEEE-RBTS system, the simulation results show that the reliability of distribution network system is closely related to the distributed power access point, the DG capacity and the DG output correlation coefficient.

A highly reliable traffic network was very important after a disaster, and the network reliability could be improved and maintained by many methods. However, it was difficult to improve more reliable links than less reliable links which has not been considered in most of current methods. Therefore, this paper proposed a method for improving link reliability which was combined the cost-benefit function with the criticality importance. A model to identify the relationship between the cost and reliability from the point of view of the efficiency of local government was proposed. The result that the strategy to improve the link reliability should be changed according to the different investment strategies and the different government efficiency has been got based on our models and discussion.