Active User and Data Detection for Uplink Grant-free NOMA Systems

This paper proposes some low complexity algorithms for active user detection(AUD),channel estimation(CE)and multi-user detection(MUD)in uplink non-orthogonal multiple access(NOMA)systems,including single-carrier and multi-carrier cases.In particular,we first propose a novel algorithm to estimate the active users and the channels for single-carrier based on complex alternating direction method of multipliers(ADMM),where fast decaying feature of non-zero components in sparse signal is considered.More importantly,the reliable estimated information is used for AUD,and the unreliable information will be further handled based on estimated symbol energy and total accurate or approximate number of active users.Then,the proposed algorithm for AUD in single-carrier model can be extended to multi-carrier case by exploiting the block sparse structure.Besides,we propose a low complexity MUD detection algorithm based on alternating minimization to estimate the active users’data,which avoids the Hessian matrix inverse.The convergence and the complexity of proposed algorithms are analyzed and discussed finally.Simulation results show that the proposed algorithms have better performance in terms of AUD,CE and MUD.Moreover,we can detect active users perfectly for multi-carrier NOMA system.

Novel Spectrum Allocation Algorithm Based on the Activities of Primary Users for Cognitive Radio Networks

In traditional cognitive radio (CR) network, most existing graph-based spectrum allocation schemes don't take on-off behavior of primary users (PUs) into consideration. In this paper, a novel spectrum allocation algorithm based on the activities of the PUs is proposed. The proposed algorithm mainly focuses on the vacant probability of licensed spectrums. And it allocates the vacant spectrums considering the interference to the neighbor cognitive nodes and the probability fairness of different cognitive nodes during the allocation. Based on the definition of the obtained benefit of cognitive node, new utility functions are formulated to characterize the system total spectrum utilization and fairness performance from the perspective of available probability. The simulation results validate that the proposed algorithm with low system communication cost is more effective than the traditional schemes when the available licensed spectrums are not sufficient, which is effective and meaningful to a real CR system with bad network condition.

An index model for measuring microblog users' influence

Purpose: The paper aims to build an index model for measuring microblog users' influence by taking microbloggers of Sina Weibo as a research sample.Design/methodology/approach: Our user influence index model emphasizes link analysis and user activities in the microblogging network. We conduct experiments to investigate the performance of our model by using data crawled from Sina Weibo.Findings: User influence is correlated to the attention that a user has received from his/her audience,the user's activities and his/her tweets' influence. Experimental results show that our model can reflect microbloggers' influence in a more reasonable way.Research limitations: More factors need to be considered to identify different influential users at different time periods.Practical implications: The results of the study provide us with insights both into the way to measure microblog users' influence and to rank users based on their influence.Originality/value: By combining link analysis and user activities,this index model can reduce the impact of dummy follower accounts on user influence,reflecting a user's real influence in the microblog system.

Multi-Panel Extra-Large Scale MIMO Based Joint Activity Detection and Channel Estimation for Near-Field Massive IoT Access

The extra-large scale multiple-input multiple-output(XL-MIMO)for the beyond fifth/sixth generation mobile communications is a promising technology to provide Tbps data transmission and stable access service.However,the extremely large antenna array aperture arouses the channel near-field effect,resulting in the deteriorated data rate and other challenges in the practice communication systems.Meanwhile,multi-panel MIMO technology has attracted extensive attention due to its flexible configuration,low hardware cost,and wider coverage.By combining the XL-MIMO and multi-panel array structure,we construct multi-panel XL-MIMO and apply it to massive Internet of Things(IoT)access.First,we model the multi-panel XL-MIMO-based near-field channels for massive IoT access scenarios,where the electromagnetic waves corresponding to different panels have different angles of arrival/departure(AoAs/AoDs).Then,by exploiting the sparsity of the near-field massive IoT access channels,we formulate a compressed sensing based joint active user detection(AUD)and channel estimation(CE)problem which is solved by AMP-EM-MMV algorithm.The simulation results exhibit the superiority of the AMP-EM-MMV based joint AUD and CE scheme over the baseline algorithms.

Energy-Efficient Low-Complexity Algorithm in 5G Massive MIMO Systems

Energy efficiency(EE)is a critical design when taking into account circuit power consumption(CPC)in fifth-generation cellular networks.These problems arise because of the increasing number of antennas in massive multiple-input multiple-output(MIMO)systems,attributable to inter-cell interference for channel state information.Apart from that,a higher number of radio frequency(RF)chains at the base station and active users consume more power due to the processing activities in digital-to-analogue converters and power amplifiers.Therefore,antenna selection,user selection,optimal transmission power,and pilot reuse power are important aspects in improving energy efficiency in massive MIMO systems.This work aims to investigate joint antenna selection,optimal transmit power and joint user selection based on deriving the closed-form of the maximal EE,with complete knowledge of large-scale fading with maximum ratio transmission.It also accounts for channel estimation and eliminating pilot contamination as antennas M→∞.This formulates the optimization problem of joint optimal antenna selection,transmits power allocation and joint user selection to mitigate inter-cellinterference in downlink multi-cell massive MIMO systems under minimized reuse of pilot sequences based on a novel iterative low-complexity algorithm(LCA)for Newton’s methods and Lagrange multipliers.To analyze the precise power consumption,a novel power consumption scheme is proposed for each individual antenna,based on the transmit power amplifier and CPC.Simulation results demonstrate that the maximal EE was achieved using the iterative LCA based on reasonable maximum transmit power,in the case the noise power is less than the received power pilot.The maximum EE was achieved with the desired maximum transmit power threshold by minimizing pilot reuse,in the case the transmit power allocationρd=40 dBm,and the optimal EE=71.232 Mb/j.

User activities and the heteroseneity of urban space:The case of Dahiyat Al Hussein park

Urban researchers have maintained a constant interest in the complexity and continuity of urban space usage.Some have applied actor-network theory(ANT)to investigate the heterogeneity of spaces and present them through the networks of their users'activities.However,these accounts are predominantly limited in examining the extent to which these spaces may be heterogeneous when exploring such networks.This paper draws on recent ANT scholarship,which employs an ethnographic research conducted in a main park in a housing project at Dahiyat Al Hussein in Amman,Jordan.The findings describe the complex and unpredictable negotiations that occur with in spaces by documenting the varieties and in terrelations among user activity networks within this common and shared urban space.This research reveals the extent to which spaces,parks in this case,may be heterogeneous by unpacking their usage.The conclusions and in sights assert then ecessity of paying attention to design detail and creating designs that are responsive to evolving user activities.

Joint model of user check-in activities for point-of-interest recommendation

With the rapid development of location-based networks, point-of-interest（POI） recommendation has become an important means to help people discover interesting and attractive locations, especially when users travel out of town. However, because users only check-in interaction is highly sparse, which creates a big challenge for POI recommendation. To tackle this challenge, we propose a joint probabilistic generative model called geographical temporal social content popularity（GTSCP） to imitate user check-in activities in a process of decision making, which effectively integrates the geographical influence, temporal effect, social correlation, content information and popularity impact factors to overcome the data sparsity, especially for out-of-town users. Our proposed the GTSCP supports two recommendation scenarios in a joint model, i.e., home-town recommendation and out-of-town recommendation. Experimental results show that GTSCP achieves significantly superior recommendation quality compared to other state-of-the-art POI recommendation techniques.

Big Data Modeling and Analysis of Microblog Ecosystem

Recent progress of Web 2.0 applications has witnessed the rapid development of microblog in China, which has already been one of the most important ways for online communications, especially on sharing information. This paper tries to make an in-depth investigation on the big data modeling and analysis of microblog ecosystem in China by using a real dataset containing over17 million records of SinaWeibo users. First, we present the detailed geography, gender, authentication, education and age analysis of microblog users in this dataset. Then we conduct the numerical features distribution analysis, propose the user influence formula and calculate the influences for different kinds of microblog users. Finally, user content intention analysis is performed to reveal users most concerns in their daily life.