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10th International Conference on Intelligent Computation Technology and Automation (ICICTA)

作者： Rong, Rong Fu, Yuli Xiang, Youjun Xu, Junwei South China Univ Technol Sch Elect & Informat Engn Guangzhou 510640 Guangdong Peoples R China

ISBN: (纸本)9781538612309

The problem of constructing matrix with low-coherence is arised in many applications, such as CDMA, compressive sensing (CS), beamforming, etc. Usually the design of low-coherence codebook can be modeled as vector quantization (VQ) problem, and generalized lloyd algorithm is designed to solve it. Since lloyd algorithm is a method of local optimization, its performance is influenced by initial value. In this paper, candidate of initial value of lloyd algorithm is studied. A construction based on finite abelian group which can be used as candidate of initial value will be analyzed. Experimental results prove that using this construction as initial value in lloyd algorithm can improve the performance significantly.

关键词： Beamforming Compressive sensing lloyd algorithm Abelian group Welch Bound

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Vector Quantization Methods for Access Point Placement in Cell-Free Massive MIMO Systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2024年第6期23卷 5425-5440页

作者： Gopal, Govind R. Rao, Bhaskar D. Univ Calif San Diego Dept Elect & Comp Engn La Jolla CA 92093 USA

We examine the problem of uplink cell-free access point (AP) placement in the context of optimal throughput. In this regard, we formulate two main placement problems, namely the sum rate and minimum rate maximization problems, and discuss the challenges associated with solving the underlying optimization problems with the help of some simple scenarios. As a practical solution to the AP placement problem, we suggest a vector quantization (VQ) approach. The suitability of the VQ approach to cell-free AP placement is investigated by examining three VQ-based solutions. First, the standard VQ approach, that is the lloyd algorithm (using the squared error distortion function) is described. Second, the tree-structured VQ (TSVQ), which performs successive partitioning of the distribution space is applied. Third, a probability density function optimized VQ (PDFVQ) procedure is outlined, enabling efficient, low complexity, and scalable placement, and is aimed at a massive distributed multiple-input-multiple-output scenario. While the VQ-based solutions do not explicitly solve the cell-free AP placement problems, numerical experiments show that their sum and minimum rate performances are good enough, and offer a good starting point for gradient-based optimization methods. Among the VQ solutions, PDFVQ, with its distinct advantages, offers a good trade-off between sum and minimum rates.

关键词： Base station placement beyond 5G lloyd algorithm scalability throughput optimization

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Modified Vector Quantization for Small-Cell Access Point Placement With Inter-Cell Interference

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2022年第8期21卷 6387-6401页

作者： Gopal, Govind R. Nayebi, Elina Villardi, Gabriel Porto Rao, Bhaskar D. Univ Calif San Diego Dept Elect & Comp Engn La Jolla CA 92093 USA Apple Inc Cupertino CA 95014 USA Univ Calif San Diego Qualcomm Inst Calit2 La Jolla CA 92093 USA Natl Inst Informat & Commun Technol NICT Wireless Network Res Ctr Yokosuka Kanagawa 2390847 Japan

In this paper, we explore the small-cell uplink access point (AP) placement problem in the context of throughput optimality and provide solutions while taking into consideration inter-cell interference (ICI). First, we briefly review the vector quantization (VQ) approach and related single user throughput-optimal formulations for AP placement. Then, we investigate the small-cell case with multiple users and expose the limitations of mean squared error based VQ for solving this problem. While the lloyd algorithm from the VQ approach is found not to strictly solve the small-cell case, based on the tractability and quality of the resulting AP placement, we deem it suitable as a simple and appropriate framework to solve more complicated problems. Accordingly, to minimize ICI and consequently enhance achievable throughput, we design two lloyd-type algorithms, namely the Interference lloyd algorithm and the Inter-AP lloyd algorithm, both of which incorporate ICI in their distortion functions. Simulation results show that both of the proposed algorithms provide superior 95%-likely rate over the traditional lloyd algorithm and the Inter-AP lloyd algorithm yields a significant increase of up to 36.34% in achievable rate over the lloyd algorithm.

关键词： Throughput Signal to noise ratio Interference Antennas Antenna arrays Massive MIMO Fading channels Base station placement beyond 5G lloyd algorithm SINR minimization throughput optimization user cell association

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Load Balancing in Small-Cell Access Point Placement 97

Load Balancing in Small-Cell Access Point Placement

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97th IEEE Vehicular Technology Conference (VTC-Spring)

作者： Gopal, Govind R. Rao, Bhaskar D. Villardi, Gabriel Porto Univ Calif San Diego Dept Elect & Comp Engn La Jolla CA 92093 USA Natl Inst Informat & Commun Technol Wireless Network Res Ctr Yokosuka Japan

ISBN: (纸本)9798350311143

We address the uplink small-cell access point (AP) placement problem for optimal throughput, while considering load balancing (LB) among the APs. To consider LB and consequently incorporate fairness in user spectral access, i.e., the frequency of user-to-AP communications, we modify the lloyd algorithm from vector quantization so that delays incurred by the existence of a large number of users in a cell are accounted for in the AP placement process. Accordingly, we present two methods, the first of which involves the incorporation of weights proportional to the cell occupancy, hence called the Occupancy Weighted lloyd algorithm (OWLA). The second method adds a new step to the lloyd algorithm, which involves re-assigning users from higher to lower occupancy cells, and the adoption of a distance threshold to cap the throughput lost in the assignment process. This formulated lloyd-type algorithm is called the Cell Equalized lloyd algorithm-alpha (CELA-alpha) where alpha is a factor that allows for throughput and spectrum access delay trade-off. Extensive simulations show that both CELA-alpha and OWLA algorithms provide significant gains, in comparison to the standard lloyd algorithm, in 95%-likely user spectral access. For the alpha values considered in this paper, CELA-alpha achieves gains up to 20.83%, while OWLA yields a gain of 12.5%. Both algorithms incur minimal throughput losses of different degrees, and the choice of using one algorithm over the other for AP placement depends on system LB as well as throughput requirements.

关键词： Base station placement Beyond 5G fairness lloyd algorithm throughput optimization user cell association

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A Constructive Density Function Path Leading to Global Coverage Strategy for A Gaussian Random Field 12

A Constructive Density Function Path Leading to Global Cover...

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IEEE 12th Data Driven Control and Learning Systems Conference (DDCLS)

作者： Yang, Yuxing Sue, Mao Fan, Huijin Liu, Lei Wang, Bo Huazhong Univ Sci & Technol Sch Artificial Intelligence & Automat Wuhan 430074 Peoples R China Designing Inst Hubei Space Technol Acad Wuhan 430074 Peoples R China

ISBN: (纸本)9798350321050

The coverage of a given environment is an important issue in detection and rescue problems. This article presents a novel lloyd algorithm for multi-agent coverage of a Gaussian random field characterized by a density function. The core issue is to construct a density function path (DFP) which ensures the distribution function of agents to converge to the one of targets iteratively. By proposing a triggering condition and a series of Gaussian distributionn functions, local optimum of traditional lloyd algorithm can be avoided. The proposed algorithm make the coverage function reach a global solution with a small enough iteration interval. Simulation result is provided to illustrate the effectiveness of the proposed approach.

关键词： coverage control distributed optimization Gaussian random fields lloyd algorithm

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Access Point Placement for Hybrid UAV-Terrestrial Small-Cell Networks

IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY

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IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY 2021年 2卷 1826-1841页

We address the problem of access point (AP) placement in small-cell networks with partial infrastructure flexibility, i.e., a novel class of problem in Beyond 5G, resultant from the utilization of unmanned aerial vehicles (UAVs) with AP functionalities (UAV-APs), to aid fixed wireless networks in coping with momentary peak-capacity requirements. We use the signal-to-generated-interference-plus-noise ratio (SGINR) metric as an alternative to the traditional signal-to-interference-plus-noise ratio (SINR) to quantify the effects of inter-cell interference (ICI) on the per-user capacity. From average SGINR, we derive the ICI-aware distortion measure leading to the Inter-AP lloyd algorithm to obtain throughput-optimal AP placement for a fully flexible infrastructure. We then impose a hybridity constraint to the AP placement problem which turns a fraction of the network into a fixed infrastructure composed of terrestrial APs (T-APs) while the remainder is constituted by UAV-APs with flexibility in position. This newly formulated AP placement problem is solved by the proposed lloyd-type algorithm called Hybrid AP Placement algorithm (HAPPA). Furthermore, we present an initialization method for the lloyd and lloyd-type algorithms for Gaussian mixture models (GMMs) that offers an AP allocation leading to a higher rate compared to the k-means++ initialization. Finally, computer simulations show that the Inter-AP lloyd algorithm can improve the performance of the worst users by up to 42.75% in achievable rate, assuming a fully flexible network. By using HAPPA on hybrid networks, we achieve improvements of up to 71.92% in sum rate over the fixed network and close the performance gap with fully flexible networks down to 2.02%, when an equal number of UAV-APs and T-APs is used. Further, our proposed initialization scheme always results in a balanced AP allocation, which means a more even distribution of users per AP, whereas the k-means++ scheme results in unbalanced allocations

关键词： Interference Throughput Signal to noise ratio Resource management Unmanned aerial vehicles Distortion MIMO communication Beyond 5G hybrid network inter-cell interference (ICI) lloyd algorithm unmanned aerial vehicle (UAV)

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A modification of the lloyd algorithm for k-anonymous quantization

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INFORMATION SCIENCES 2013年 222卷 185-202页

作者： Rebollo-Monedero, David Forne, Jordi Pallares, Esteve Parra-Arnau, Javier Univ Politecn Cataluna Dept Telemat Engn E-08034 Barcelona Spain

We address the problem of designing quantizers that cluster data while satisfying a k-anonymity requirement. A general data compression perspective is adopted, which considers both discrete and continuous probability distributions, and corresponding constraints on both cell sizes and quantizer index probabilities. Potential applications of this problem extend well beyond the important case of microdata anonymization, to include also optimized task allocation under workload constraints. Our contribution is twofold. First and most importantly, we present a theoretical analysis showing the optimality conditions which probability-constrained quantizers must satisfy, thereby theoretically characterizing optimal k-anonymous aggregation as a special case. As a second contribution, inspired by our theoretical analysis, we propose an alternating optimization algorithm for the design of this type of quantizers. Our algorithm is conceptually motivated by the popular lloyd-Max algorithm for quantization design, originally intended for data compression, also known as the k-means method. Experimental results for synthetic and real data, with mean squared error as a distortion measure, confirm that our method outperforms MDAV, a popular fixed-size microaggregation algorithm for statistical disclosure control. This performance improvement is in terms of data utility, for the exact same k-anonymity constraint, but does come at the expense of higher computational sophistication. (C) 2012 Elsevier Inc. All rights reserved.

关键词： Microdata anonymization k-Anonymity lloyd algorithm k-Means method k-Anonymous quantization

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Energy-Efficient Node Deployment in Wireless Ad-hoc Sensor Networks

Energy-Efficient Node Deployment in Wireless Ad-hoc Sensor N...

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IEEE International Conference on Communications (IEEE ICC) / Workshop on NOMA for 5G and Beyond

作者： Guo, Jun Karimi-Bidhendi, Saeed Jafarkhani, Hamid Univ Calif Irvine Ctr Pervas Commun & Comp Irvine CA 92697 USA

ISBN: (纸本)9781728150895

We study a wireless ad-hoc sensor network (WASN) where N sensors gather data from the surrounding environment and transmit their sensed information to M fusion centers (FCs) via multi-hop wireless communications. This node deployment problem is formulated as an optimization problem to make a trade-off between the sensing uncertainty and energy consumption of the network. Our primary goal is to find an optimal deployment of sensors and FCs that minimizes a Lagrangian combination of sensing uncertainty and energy consumption. To support arbitrary routing protocols in WASNs, the routing-dependent necessary conditions for the optimal deployment are explored. Based on these necessary conditions, we propose a routing-aware lloyd-like algorithm to optimize node deployment. Simulation results show that our proposed algorithm outperforms the existing deployment algorithms, on average.

关键词： node deployment wireless ad-hoc sensor networks lloyd algorithm optimization

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Throughput and Delay Driven Access Point Placement 53

Throughput and Delay Driven Access Point Placement

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53rd Asilomar Conference on Signals, Systems, and Computers (ACSSC)

作者： Gopal, Govind R. Rao, Bhaskar D. Univ Calif San Diego Dept Elect & Comp Engn San Diego CA 92103 USA

ISBN: (数字)9781728143002

ISBN: (纸本)9781728143002

With higher rates and increased diversity, distributed massive MIMO systems show promise. In this work, we look at such a system with no collaboration between Access Points (APs). We address the AP placement problem with two criteria in mind: throughput and delay. While the former deals with optimal AP locations given a user distribution, the latter adds a constraint of equal user access to the APs. In this regard, we propose the Cell Equalized lloyd algorithm (CELA), which in addition to the steps of the lloyd algorithm, moves users from cells with more users to cells with fewer users in order to equalize the number of users in each cell without significantly affecting user throughput. Normalized user rate and user access count metrics are employed to evaluate the system characteristics. The performance of CELA is compared with that of the traditional lloyd algorithm, and while a slight reduction in throughput is observed, the increase in user access outweighs this reduction.

关键词： Distributed massive MIMO Access Point placement lloyd algorithm Throughput Delay

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ON A FUNDAMENTAL PREDICTABILITY-DISTORTION TRADE-OFF IN DECENTRALIZED DECISIONAL NETWORKS 53

ON A FUNDAMENTAL PREDICTABILITY-DISTORTION TRADE-OFF IN DECE...

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53rd Asilomar Conference on Signals, Systems, and Computers (ACSSC)

作者： Miretti, Lorenzo de Kerret, Paul Gesbert, David EURECOM Sophia Antipolis France

ISBN: (纸本)9781728143002

Decentralized decisional networks are composed of agents that take coordinated decisions on the basis of individual noisy information about the system state, i.e. under a so called distributed state information configuration. In such scenarios, the application of algorithms directly derived from classical centralized optimization often incurs severe performance degradation. This is because the agents fail to predict each other's decision due to local state information noise, hence they do not coordinate properly. On the other hand coordination can be easily enhanced by letting one agent reduce its dependency with respect to its state information, thus making its decision more predictable but less adapted to the system state. This observation naturally leads to formulating a fundamental trade-off, coined here predictability-distortion trade off. The goal of this paper is to formulate this trade-off and propose a framework to explore it, based on a concept of quantization under predictability constraint.

关键词： quantization coordination multi-agent systems team decision problems lloyd algorithm

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