Signal design for Multiple-Antenna Systems and Wireless Networks

This dissertation is concerned with the signal design problems for Multiple Input and Multiple Output (MIMO) antenna systems and wireless networks. Three related but distinct problems are considered.The first problem considered is the design of space time codes for MIMO systems in the case when neither the transmitter nor the receiver knows the channel. We present the theoretical concept of communicating over block fading channel using Layered Unitary Space Time Codes (LUSTC), where the input signal is formed as a product of a series of unitary matrices with corresponding dimensionality. We show the channel capacity using isotropically distributed (i.d.) input signaling and optimal decoding can be achieved by layered i.d. signaling scheme along with a low complexity successive decoding. The closed form layered channel capacity is obtained, which serves as a design guideline for practical LUSTC. In the design of LUSTC, a successive design method is applied to leverage the problem of optimizing over lots of parameters.The feedback of channel state information (CSI) to the transmitter in MIMO systems is known to increase the forward channel capacity. A suboptimal power allocation scheme for MIMO systems is then proposed for limited rate feedback of CSI. We find that the capacity loss of this simple scheme is rather small compared to the optimal water-filling solution. This knowledge is applied for the design of the feedback codebook. In the codebook design, a generalized Lloyd algorithm is employed, in which the computation of the centroid is formulated as an optimization problem and solved optimally. Numerical results show that the proposed codebook design outperforms the existing algorithms in the literature.While it is not feasible to deploy multiple antennas in a wireless node due to the space limitation, user cooperation is an alternative to increase performance of the wireless networks. To this end, a coded user cooperation scheme is considered in the dissertation, which is shown to be equivalent to a coding scheme with the encoding done in a distributive manner. Utilizing the coding theoretic bound and simulation results, we show that the coded user cooperation scheme has great advantage over the non-cooperative scheme

Characterizing ξ

Let ℳ and be von Neumann algebras without central summands of type I1. Assume that ξ∈ℂ with ξ≠1. In this paper, all maps Φ:ℳ→ satisfying ΦAB-ξBA=ΦAΦB-ξΦBΦ(A) are characterized

The predictive value of interim earnings

This study empirically examines the value of interim earnings in predicting annual earnings. I find that analysts’ annual earnings forecast revisions are positively associated with interim earnings forecast error when the interim earnings are relatively persistent. The change in analysts’ annual earnings forecast dispersion is positively (negatively) associated with interim earnings forecast-error (persistence)

A research on family-owned newspaper

This paper conducts a research on the family-owned newspapers by interviewing the managers from the industry and doing a solid content analysis. It answers three research questions: What is the role of organizational ecology in the development or innovation of family-owned newspapers? How can organizational ecology be applied to newspapers? What elements on the newspapers’ websites are possibly profitable for the newspaper

Image Captioning with Context-Aware Auxiliary Guidance

Image captioning is a challenging computer vision task, which aims to generate a natural language description of an image. Most recent researches follow the encoder-decoder framework which depends heavily on the previous generated words for the current prediction. Such methods can not effectively take advantage of the future predicted information to learn complete semantics. In this paper, we propose Context-Aware Auxiliary Guidance (CAAG) mechanism that can guide the captioning model to perceive global contexts. Upon the captioning model, CAAG performs semantic attention that selectively concentrates on useful information of the global predictions to reproduce the current generation. To validate the adaptability of the method, we apply CAAG to three popular captioners and our proposal achieves competitive performance on the challenging Microsoft COCO image captioning benchmark, e.g. 132.2 CIDEr-D score on Karpathy split and 130.7 CIDEr-D (c40) score on official online evaluation server

On Performance Debugging of Unnecessary Lock Contentions on Multicore Processors: A Replay-based Approach

Locks have been widely used as an effective synchronization mechanism among processes and threads. However, we observe that a large number of false inter-thread dependencies (i.e., unnecessary lock contentions) exist during the program execution on multicore processors, thereby incurring significant performance overhead. This paper presents a performance debugging framework, PERFPLAY, to facilitate a comprehensive and in-depth understanding of the performance impact of unnecessary lock contentions. The core technique of our debugging framework is trace replay. Specifically, PERFPLAY records the program execution trace, on the basis of which the unnecessary lock contentions can be identified through trace analysis. We then propose a novel technique of trace transformation to transform these identified unnecessary lock contentions in the original trace into the correct pattern as a new trace free of unnecessary lock contentions. Through replaying both traces, PERFPLAY can quantify the performance impact of unnecessary lock contentions. To demonstrate the effectiveness of our debugging framework, we study five real-world programs and PARSEC benchmarks. Our experimental results demonstrate the significant performance overhead of unnecessary lock contentions, and the effectiveness of PERFPLAY in identifying the performance critical unnecessary lock contentions in real applications.Comment: 18 pages, 19 figures, 3 table

Disentangling the Effect of Shared Experience on Emotional Arousal in Entertainment Live Streaming

Live streaming platforms are promoting a novel format of entertainment called PK event where live streamers compete to solicit virtual gifts from viewers. Although the two live streamers in a PK event come across as rivals, they implicitly collaborate to emotionally arouse viewers and solicit virtual gifts. We advance a curvilinear moderated mediation model to disentangle the effects of streamers’ shared PK experience on revenue growth through enticing viewers’ emotional arousal, which is moderated by streamers’ within-team experience acquisition difference. Estimating a multilevel linear model on a sample of 118,323 PK records, we discovered that shared PK experience has an inverted-U-shape relationship with emotional arousal level, which is positively associated with revenue growth. We further attested to the moderating influence of experience acquisition difference in strengthening this curvilinear relationship. Our findings help platforms to improve team member recommendation systems and streamers to find the “right” teammates for optimizing PK performance