48 research outputs found
Crawling and Analyzing Repository in GitHub
GitHub has become one of the most popular online software developing website. I have crawled the most popular software repositories (own over 500 star number) in GitHub, along with their contributors and stargazers. In total, we have crawled 10,665 repositories, 176,256 contributors, and 1,170,449 stargazers. One of the most important missions of analyzing is detecting communities from the network. While the heterogeneous Github network includes three objects, user, repository and pro- gramming languages and two kinds of relation between user and repository, i.e., star and contribute. Mining heterogeneous information network is a fresh and promising research field in data mining. A lot of algorithms has been proposed for heteroge- neous network clustering. However, most of these methods directly cluster the het- erogeneous networks. This thesis aims to transform the heterogeneous network to the homogeneous network using different schemes and then cluster the new network. We studied three weighting schemes, including dot product, Jaccard similarity and cosine similarity between the vector representations of objects. Then I cluster the homoge- neous network by using modularity maximization optimization algorithms, in particu- lar, greedy modularity maximization optimization algorithm and spectral modularity maximization optimization algorithm. The performance of clustering is evaluated using F-measure and rand index based on the programming language the software repository used. To compare the interaction between the weighting schemes and clus- tering algorithms, we applied out methods on GitHub dataset. Then we transformed the whole network to repository-repository and furthermore transformed it to the language-repository network. Based on this network, we discovered the relation be- tween languages. Among 94 programming languages used by the top 10,000 projects, we studied their relations using several clustering methods. Overall, we find that lan- guages fall into five communities, i.e., web and scripting languages (JavaScrip, HTML, etc.), system programming languages (C, C++, etc.), OS X and IOS programming languages (Objective-C, Swift, etc.), numerical and statistical languages (Matlab, FORTRAN, Julia and R), and functional programming (Lisp, Scheme, etc.)
Optimizing the Age of Information in RIS-aided SWIPT Networks
In this letter, a reconfigurable intelligent surface (RIS)-assisted
simultaneous wireless information and power transfer (SWIPT) network is
investigated. To quantify the freshness of the data packets at the information
receiver, the age of information (AoI) is considered. To minimize the sum AoI
of the information users while ensuring that the power transferred to energy
harvesting users is greater than the demanded value, we formulate a scheduling
scheme, and a joint transmit beamforming and phase shift optimization at the
base station (BS) and RIS, respectively. The alternating optimization (AO)
algorithm is proposed to handle the coupling between active beamforming and
passive RIS phase shifts, and the successive convex approximation (SCA)
algorithm is utilized to tackle the non-convexity of the formulated problems.
The improvement in terms of AoI provided by the proposed algorithm and the
trade-off between the age of information and energy harvesting is quantified by
the numerical simulation results
Enhancing Near-Field Sensing and Communications with Sparse Arrays: Potentials, Challenges, and Emerging Trends
As a promising technique, extremely large-scale (XL)-arrays offer potential
solutions for overcoming the severe path loss in millimeter-wave (mmWave) and
TeraHertz (THz) channels, crucial for enabling 6G. Nevertheless, XL-arrays
introduce deviations in electromagnetic propagation compared to traditional
arrays, fundamentally challenging the assumption with the planar-wave model.
Instead, it ushers in the spherical-wave (SW) model to accurately represent the
near-field propagation characteristics, significantly increasing signal
processing complexity. Fortunately, the SW model shows remarkable benefits on
sensing and communications (S\&C), e.g., improving communication multiplexing
capability, spatial resolution, and degrees of freedom. In this context, this
article first overviews hardware/algorithm challenges, fundamental potentials,
promising applications of near-field S\&C enabled by XL-arrays. To overcome the
limitations of existing XL-arrays with dense uniform array layouts and improve
S\&C applications, we introduce sparse arrays (SAs). Exploring their potential,
we propose XL-SAs for mmWave/THz systems using multi-subarray designs. Finally,
several applications, challenges and resarch directions are identified
Energy-Efficient Cell-Free Network Assisted by Hybrid RISs
In this letter, we investigate a cell-free network aided by hybrid
reconfigurable intelligent surfaces (RISs), which consists of a mixture of
passive and active elements that are capable of amplifying and reflecting the
incident signal. To maximize the energy efficiency (EE) of the system, we
formulate a joint transmit beamforming and RIS coefficients optimization
problem. To deal with the fractional objective function, Dinkelbach transform,
Lagrangian dual reformulation, and quadratic transform are utilized, with a
block coordinate descent (BCD) based algorithm proposed to decouple the
variables. In addition, successive convex approximation (SCA) method is applied
to iteratively to tackle the non-convexity of the sub-problems. Simulation
results illustrate the effectiveness and convergence of the proposed algorithm
through analyzing the EE and sum rate performance with varying parameter
settings. The proposed hybrid RISs schemes can achieve 92% of the sum rate but
188% of EE of active RISs schemes. As compared with passive RISs, 11% gain in
sum rate can be achieved with comparable EE
Mutual Information-Based Integrated Sensing and Communications: A WMMSE Framework
In this letter, a weighted minimum mean square error (WMMSE) empowered
integrated sensing and communication (ISAC) system is investigated. One
transmitting base station and one receiving wireless access point are
considered to serve multiple users a sensing target. Based on the theory of
mutual-information (MI), communication MI and sensing MI rate are utilized as
the performance metrics under the presence of clutters. In particular, we
propose an novel MI-based WMMSE-ISAC method by developing a unique transceiver
design mechanism to maximize the weighted sensing and communication sum-rate of
this system. Such a maximization process is achieved by utilizing the classical
method -- WMMSE, aiming to better manage the effect of sensing clutters and the
interference among users. Numerical results show the effectiveness of our
proposed method, and the performance trade-off between sensing and
communication is also validated
Reconfigurable Intelligent Surfaces Aided mmWave NOMA: Joint Power Allocation,Phase Shifts, and Hybrid Beamforming Optimization
In this paper, an reconfigurable intelligent surface (RIS)-aided millimeter
wave (mmWave) non-orthogonal multiple access (NOMA) system is considered. In
particular, we consider an RIS-aided mmWave-NOMA downlink system with a hybrid
beamforming structure. To maximize the achievable sum-rate under a minimum rate
constraint for the users and a minimum transmit power constraint, a joint RIS
phase shifts, hybrid beamforming, and power allocation problem is formulated.
To solve this non-convex optimization problem, we develop an alternating
optimization algorithm. Specifically, first, the non-convex problem is
transformed into three subproblems, i.e., power allocation, joint phase shifts
and analog beamforming optimization, and digital beamforming design. Then, we
solve the power allocation problem under fixed phase shifts of the RIS and
hybrid beamforming. Finally, given the power allocation matrix, an alternating
manifold optimization (AMO)-based method and a successive convex approximation
(SCA)-based method are utilized to design the phase shifts, analog beamforming,
and transmit beamforming, respectively. Numerical results reveal that the
proposed alternating optimization algorithm outperforms state-of-the-art
schemes in terms of sum-rate. Moreover, compared to a conventional mmWave-NOMA
system without RIS, the proposed RIS-aided mmWave-NOMA system is capable of
improving the achievable sum-rate of the system