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Online shopping has been prevalent in our daily life. Profiling users and understanding their browsing behaviors are critical for enhancing shopping experience and maximizing sales revenue. In this paper, based on a one-month dataset recording 2 million users’ 67 million online shopping and browsing logs, we seek to understand how users browse and shop products, and how distinct these behaviors are. We find that there exist dedicate groups of users that prefer certain product categories corresponding to similar demands. Moreover, distinct differences of behaviors exist in categories, where repetitive and targeted browsing are two major prevalent patterns. [ABSTRACT FROM AUTHOR]

With the explosive growth of mobile data demand, the fifth generation (5G) mobile network would exploit the enormous amount of spectrum in the millimeter wave (mmWave) bands to greatly increase communication capacity. There are fundamental differences between mmWave communications and existing other communication systems, in terms of high propagation loss, directivity, and sensitivity to blockage. These characteristics of mmWave communications pose several challenges to fully exploit the potential of mmWave communications, including integrated circuits and system design, interference management, spatial reuse, anti-blockage, and dynamics control. To address these challenges, we carry out a survey of existing solutions and standards, and propose design guidelines in architectures and protocols for mmWave communications. We also discuss the potential applications of mmWave communications in the 5G network, including the small cell access, the cellular access, and the wireless backhaul. Finally, we discuss relevant open research issues including the new physical layer technology, software-defined network architecture, measurements of network state information, efficient control mechanisms, and heterogeneous networking, which should be further investigated to facilitate the deployment of mmWave communication systems in the future 5G networks. [ABSTRACT FROM AUTHOR]

For direct-conversion transceiver, IQ imbalance is significant at both transmitter (TX) and receiver (RX), which brings in image interference and degrades the transmission quality. In order to handle this problem, the maximum-likelihood algorithm is employed to jointly estimate TX and RX IQ imbalance, and the corresponding Cramer-Rao lower bounds (CRLBs) are calculated. Furthermore, a compensation mechanism is proposed to combat IQ imbalance, which is derived from the criterion of maximum signal-to-interference-plus-noise ratio (MSINR). In addition, comprehensive simulations indicate that the mean square errors of the proposed estimation coincide with the CRLBs. Also, the proposed MSINR compensation achieves competitive performance, in terms of both SINR and bit error rate. [ABSTRACT FROM AUTHOR]

In the past few decades, the world has witnessed a rapid growth in mobile communication and reaped great benefits from it. Even though the fourth generation (4G) mobile communication system is just being deployed worldwide, proliferating mobile demands call for newer wireless communication technologies with even better performance. Consequently, the fifth generation (5G) system is already emerging in the research field. However, simply evolving the current mobile networks can hardly meet such great expectations, because over the years the infrastructures have generally become ossified, closed, and vertically constructed. Aiming to establish a new paradigm for 5G mobile networks, in this article, we propose a cross-layer software-defined 5G network architecture. By jointly considering both the network layer and the physical layer together, we establish the two software-defined programmable components, the control plane and the cloud computing pool, which enable an effective control of the mobile network from the global perspective and benefit technological innovations. Specifically, by the cross-layer design for software-defining, the logically centralized and programmable control plane abstracts the control functions from the network layer down to the physical layer, through which we achieve the fine-grained controlling of mobile network, while the cloud computing pool provides powerful computing capability to implement the baseband data processing of multiple heterogeneous networks. The flexible programmability feature of our architecture makes it convenient to deploy cross-layer technological innovations and benefits the network evolution. We discuss the main challenges of our architecture, including the fine-grained control strategies, network virtualization, and programmability. The architecture significantly benefits the convergence towards heterogeneous networks and enables much more controllable, programmable and evolvable mobile networks. Simulations validate these performance advantages. [ABSTRACT FROM AUTHOR]

By moving Virtual Machines(VMs) to the sites closest to their users, cross-site VM migration is promising to improve users' experience. However, when multiple VMs are required to be migrated, an arbitrary migration sequence will possibly congest the inter-site links. To avoid such congestion and also maximize the number of successful migrations, in this paper, we formulate VM migration sequence planning problem as a Mixed Integer Linear Programming(MILP) problem, which considers both inter-VM communication traffic and migration traffic. Due to the high computational complexity to get the optimal results, we further propose a heuristic algorithm referred as MinUti-O to approximate the optimal results with low complexity. The extensive simulation results show that the success ratio achieved by MinUti-O is close to the optimal results with less than 5 % gap under different topology with variation of migration requests and network conditions. [ABSTRACT FROM AUTHOR]

With the proliferation of mobile demands and increasingly multifarious services and applications, mobile Internet has been an irreversible trend. Unfortunately, the current mobile and wireless network (MWN) faces a series of pressing challenges caused by the inherent design. In this paper, we extend two latest and promising innovations of Internet, software-defined networking and network virtualization, to mobile and wireless scenarios. We first describe the challenges and expectations of MWN, and analyze the opportunities provided by the software-defined wireless network (SDWN) and wireless network virtualization (WNV). Then, this paper focuses on SDWN and WNV by presenting the main ideas, advantages, ongoing researches and key technologies, and open issues respectively. Moreover, we interpret that these two technologies highly complement each other, and further investigate efficient joint design between them. This paper confirms that SDWN and WNV may efficiently address the crucial challenges of MWN and significantly benefit the future mobile and wireless network. [ABSTRACT FROM AUTHOR]

The past few decades have witnessed an increasing growth in mobile and wireless network, leading to a corresponding fast growth in mobile demands. However, the proliferating mobile demands compel wireless network to face several challenges, such as the conflict between spectrum crisis and low resource utilization ratio, and the poor quality of service and quality of experience. Wireless virtualization, enabling multiple concurrent virtual networks running on shared wireless substrate resource, has been proposed as a promising way to overcome the plights of the current mobile and wireless network. How to efficiently allocate the resource, especially the spectrum resource, of physical network to multiple virtual networks is one fundamental and important challenge in wireless virtualization. This paper rethinks the characteristics of virtual networks' requirements, and then divides the requirement into a baseline part and a fluctuant part. Based on it, this paper introduces an opportunistic spectrum sharing approach, through which we formulate the spectrum resource allocation problem as an NP-Hard problem. Then, we propose our opportunistic spectrum resource allocation scheme for the wireless virtualization. Simulations validate the performance advantages of our approach and show that opportunistic spectrum sharing significantly improves the revenue, resource utilization and acceptance ratio of physical wireless network while decreasing the payments of virtual networks. [ABSTRACT FROM AUTHOR]

This paper proposes to estimate receiver (RX) IQ imbalance via pure noise for 60 GHz millimeter-wave systems. We study the impact of RX IQ imbalance on noise, and derive the maximum-likelihood algorithm to acquire the imbalance parameters, which is decoupled from transmitter IQ imbalance, channel response, and carrier offset. Also, the proposed method has low computational complexity and meets the low-power and low-cost requirements of 60 GHz systems. Moreover, the jitter performance of the estimation reaches the corresponding Cramer-Rao lower bound under a wide range of imbalance parameters. [ABSTRACT FROM AUTHOR]

For code-aided burst packet acquisition, the extensively used square-law cross-correlation noncoherent (CCN) detector is generally studied under a fixed-gain (FG) amplifier model. However, in practical communication systems an automatic-gain-control (AGC) amplifier is usually employed. In such a case CCN will significantly deteriorate, because the amplification of noise in hypothesis $${\mathcal{H }_0}$$ is larger than that of noisy signals in hypothesis $${\mathcal{H }_1}$$ . To improve detection performance, the generalized likelihood ratio test (GLRT) approach is adopted. Closed-form expressions of false alarm probability (FAP) and detection probability (DP) are derived for CCN and GLRT in both FG and AGC cases. Based on these expressions, GLRT is compared with CCN in terms of both performance and implementation complexity. Results show that although GLRT reveals a slightly poorer performance than CCN in an ideal case that an FG amplifier is used, it achieves a significant and increasing performance superiority over CCN in a practical case that AGC is exploited with an affordable extra hardware cost. [ABSTRACT FROM AUTHOR]

Automatic gain control (AGC) is extensively used in practical packet communication systems, but the effect is generally not taken into account in code acquisition research. A dedicated investigation in this paper highlights the effect of non-ideal AGC on the performance of the extensively used envelope-detector (ED) serial search acquisition (SSA) scheme, for the performance loss due to non-ideal AGC is significant. To improve the acquisition performance and eliminate the effect of AGC, a normalized-energy-detector (NED) SSA scheme is proposed. Theoretical analysis and numerical results on the performance of the proposed scheme are given. Simulations are also performed to further justify the analysis and numerical results. Performance comparisons show that the proposed scheme outperforms the ED SSA scheme with ideal and non-ideal AGC. Moreover, the proposed scheme is free from influence of AGC, and no performance loss can be found even when using non-ideal AGC for the proposed method. [ABSTRACT FROM AUTHOR]

A highly integrated monolithic Multi-Service Transport Platform (MSTP) Application Specified Integrated Circuit (ASIC) MSEOSX8-6 has been fabricated with 0.18μm CMOS technology incorporating 26×106 transistors. The chip is designed to provide standard framing and mapping of 10/100/1000Mbit/s Ethernet, Resilient Packet Ring (RPR) and E1 traffics into protected Synchronous Digital Hierarchy (SDH) STM-1 transport payloads using hitless rate adaptation for optimum bandwidth utilization. It consumes 4W of power on average and utilizes 756 pin enhanced BGA package. [ABSTRACT FROM AUTHOR]

Effective spatial planning of urban communities plays a critical role in the sustainable development of cities. Despite the convenience brought by geographic information systems and computer-aided design, determining the layout of land use and roads still heavily relies on human experts. Here we propose an artificial intelligence urban-planning model to generate spatial plans for urban communities. To overcome the difficulty of diverse and irregular urban geography, we construct a graph to describe the topology of cities in arbitrary forms and formulate urban planning as a sequential decision-making problem on the graph. To tackle the challenge of the vast solution space, we develop a reinforcement learning model based on graph neural networks. Experiments on both synthetic and real-world communities demonstrate that our computational model outperforms plans designed by human experts in objective metrics and that it can generate spatial plans responding to different circumstances and needs. We also propose a human-artificial intelligence collaborative workflow of urban planning, in which human designers can substantially benefit from our model to be more productive, generating more efficient spatial plans with much less time. Our method demonstrates the great potential of computational urban planning and paves the way for more explorations in leveraging computational methodologies to solve challenging real-world problems in urban science., (© 2023. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Cities grow in a bottom-up manner, leading to fractal-like urban morphologies characterized by scaling laws. The correlated percolation model has succeeded in modeling urban geometries by imposing strong spatial correlations; however, the origin of the underlying mechanisms behind spatially correlated urban growth remains largely unknown. Our understanding of human movements has recently been revolutionized thanks to the increasing availability of large-scale human mobility data. This paper introduces a computational urban growth model that captures spatially correlated urban growth with a micro-foundation in human mobility behavior. We compare the proposed model with three empirical datasets, discovering that strong social interactions and long-term memory effects in human movements are two fundamental principles responsible for fractal-like urban morphology, along with the three important laws of urban growth. Our model connects the empirical findings in urban growth patterns and human mobility behavior., (© 2021. The Author(s), under exclusive licence to Springer Nature America, Inc.)