Outage Performance of Two-Hop OFDM Systems with Spatially Random Decode-and-Forward Relays

In this paper, we analyze the outage performance of different multicarrier relay selection schemes for two-hop orthogonal frequency-division multiplexing (OFDM) systems in a Poisson field of relays. In particular, special emphasis is placed on decode-and-forward (DF) relay systems, equipped with bulk and per-subcarrier selection schemes, respectively. The exact expressions for outage probability are derived in integrals for general cases. In addition, asymptotic expressions for outage probability in the high signal-to-noise ratio (SNR) region in the finite circle relay distribution region are determined in closed forms for both relay selection schemes. Also, the outage probabilities for free space in the infinite relay distribution region are derived in closed forms. Meanwhile, a series of important properties related to cooperative systems in random networks are investigated, including diversity, outage probability ratio of two selection schemes and optimization of the number of subcarriers in terms of system throughput. All analysis is numerically verified by simulations. Finally, a framework for analyzing the outage performance of OFDM systems with spatially random relays is constructed, which can be easily modified to analyze other similar cases with different forwarding protocols, location distributions and/or channel conditions

Adaptive OFDM Index Modulation for Two-Hop Relay-Assisted Networks

In this paper, we propose an adaptive orthogonal frequency-division multiplexing (OFDM) index modulation (IM) scheme for two-hop relay networks. In contrast to the traditional OFDM IM scheme with a deterministic and fixed mapping scheme, in this proposed adaptive OFDM IM scheme, the mapping schemes between a bit stream and indices of active subcarriers for the first and second hops are adaptively selected by a certain criterion. As a result, the active subcarriers for the same bit stream in the first and second hops can be varied in order to combat slow frequency-selective fading. In this way, the system reliability can be enhanced. Additionally, considering the fact that a relay device is normally a simple node, which may not always be able to perform mapping scheme selection due to limited processing capability, we also propose an alternative adaptive methodology in which the mapping scheme selection is only performed at the source and the relay will simply utilize the selected mapping scheme without changing it. The analyses of average outage probability, network capacity and symbol error rate (SER) are given in closed form for decode-and-forward (DF) relaying networks and are substantiated by numerical results generated by Monte Carlo simulations.Comment: 30 page

Outage Performance Analysis of Multicarrier Relay Selection for Cooperative Networks

In this paper, we analyze the outage performance of two multicarrier relay selection schemes, i.e. bulk and per-subcarrier selections, for two-hop orthogonal frequency-division multiplexing (OFDM) systems. To provide a comprehensive analysis, three forwarding protocols: decode-and-forward (DF), fixed-gain (FG) amplify-and-forward (AF) and variable-gain (VG) AF relay systems are considered. We obtain closed-form approximations for the outage probability and closed-form expressions for the asymptotic outage probability in the high signal-to-noise ratio (SNR) region for all cases. Our analysis is verified by Monte Carlo simulations, and provides an analytical framework for multicarrier systems with relay selection

Film Cooling Enhancement with Surface Restructure

Discrete-hole film cooling is used extensively in turbine components. In past decades, many research works concerning this technique have been published. Recently, efforts have been directed at seeking technologies that would increase film cooling effectiveness. Particularly, surface reshaping through protective coatings, such as a thermal barrier coating (TBC), is very attractive to turbine designers because extra machining work is not needed for its application. In the present work, film cooling enhancement with surface restructure is experimentally studied using an infrared (IR) imaging technique. The first surface structure studied is the surface with flow-aligned blockers. The studied configurations include single-hole and three-hole-row structures. The single-hole case is used for studying the effects of blocker design parameters, which include blocker height (0.2D, 0.4D, and 0.6D), distance between two neighboring blockers (0.8D, D, and 1.2D), blocker length (2", 4", and 6"), and blowing ratio M (0.43 and 0.93). The design with the best performance is chosen for the three-hole-row cases. The second surface shape studied, is the so-called upstream ramp, which is placed in front of a row of film cooling holes. Investigated geometrical parameters include upstream ramp angles (8.5o, 15o, and 24o) and blowing ratio M (0.29, 0.43, 0.57, 0.93, and 1.36). Detailed local film cooling effectiveness and heat transfer coefficient are measured using an IR imaging technique. The third film cooling concept is the so-called trenched film cooling holes, i.e., film cooling holes sitting in a transverse groove. The film cooling structure for this experimental test consists of a three-hole row embedded in a trench 0.5D in depth and 2D in width, where D is the diameter of the holes. Five blowing ratios (0.29, 0.43, 0.57, 0.93, and 1.36) are tested. Based on the tested results, the three film cooling schemes are also compared. To implement the experimental work, a test system, which employs a FLIR infrared system to obtain local heat transfer characteristics of both two- and three-temperature problems, is developed. Detailed theoretical issues of data reduction and experimental procedures are presented

Common Bubble Detection in Large Dimensional Financial Systems

Price bubbles in multiple assets are sometimes nearly coincident in occurrence. Such near-coincidence is strongly suggestive of co-movement in the associated asset prices and likely driven by certain factors that are latent in the financial or economic system with common effects across several markets. Can we detect the presence of such common factors at the early stages of their emergence? To answer this question, we build a factor model that includes I(1), mildly explosive, and stationary factors to capture normal, exuberant, and collapsing phases in such phenomena. The I(1) factor models the primary driving force of market fundamentals. The explosive and stationary factors model latent forces that underlie the formation and destruction of asset price bubbles, which typically exist only for subperiods of the sample. The paper provides an algorithm for testing the presence of and date-stamping the origination and termination of price bubbles determined by latent factors in a large-dimensional system embodying many markets. Asymptotics of the bubble test statistic are given under the null of no common bubbles and the alternative of a common bubble across these markets. We prove consistency of a factor bubble detection process for the origination and termination dates of the common bubble. Simulations show good finite sample performance of the testing algorithm in terms of its successful detection rates. Our methods are applied to real estate markets covering 89 major cities in China over the period January 2003 to March 2013. Results suggest the presence of three common bubble episodes in what are known as China’s Tier 1 and Tier 2 cities over the sample period. There appears to be little evidence of a common bubble in Tier 3 cities

Process communication through Proxy Pipe

Proxy Pipe is designed to be a bus in the transport layer of the communication between the two different processes. Its major function is to transfer bytes. When the client process tries to send a command to the server process, it will talk to a proxy as if it were talking to a remote object. The proxy then translates the command into bytes and then asks the server Proxy Pipe to write the bytes l the client Proxy Pipe. The client Proxy Pipe the reads the bytes and translates them into the command. Proxy Pipe: defines a user-­friendly interface and it encapsulates all the related NT system calls. Proxy Pipe will be implemented in Microsoft Visual C , We will present the requirement analysis and design part by using UML (Unified Modeling Language). Design patterns like proxy, state and observer will also be applied