Drone-mounted base stations (DBSs) are promising solutions to provide ubiquitous connections to users and support many applications in the fifth generation of mobile networks while full duplex communications has the potential to improve the spectrum efficiency. In this paper, we have investigated the backhaul-aware uplink communications in a full-duplex DBS-aided HetNet (BUD) problem with the objective to maximize the total throughput of the network, and this problem is decomposed into two sub-problems: the DBS Placement problem (including the vertical position and horizontal position) and the joint UE association, power and bandwidth assignment (Joint-UPB) problem. Since the BUD problem is NP- hard, we propose approximation algorithms to solve the sub-problems and another, named the AA-BUD algorithm, to solve the BUD problem with guaranteed performance. The performance of the AA- BUD algorithm has been demonstrated via extensive simulations, and results show that the AA-BUD algorithm is superior to two benchmark algorithms.
more »
« less
Benchmarking the User-Centric Clustering and Pilot Assignment Problems in Cell-Free Networks
This paper addresses the user-centric clustering and pilot assignment problems in cell-free networks, recognizing the need to solve both problems simultaneously. The motivation of this research stems from the absence of benchmarks, general formulations, and the reliance on subjectively designed objective functions and heuristic algorithms prevalent in existing literature. To tackle these challenges, we formulate stochastic non-linear binary integer programs for both the user-centric clustering and pilot assignment problems. We specifically design the pilot assignment formulation to incorporate user-centric clusters when evaluating the desirability of pilot assignments, resulting in improved efficiency. To solve the problems, the proposed methodology employs sample average approximation coupled with surrogate optimization for the user-centric clustering problem and the genetic algorithm for the pilot assignment problem. Numerical experiments demonstrate that the optimized solutions outperform baseline solutions, leading to significant gains in spectral efficiency.
more »
« less
- Award ID(s):
- 2210252
- PAR ID:
- 10516299
- Publisher / Repository:
- IEEE
- Date Published:
- ISBN:
- 979-8-3503-1090-0
- Page Range / eLocation ID:
- 4235 to 4240
- Subject(s) / Keyword(s):
- Spectral efficiency Heuristic algorithms Clustering algorithms Benchmark testing Linear programming Optimization Genetic algorithms Cell-Free Networks Massive MIMO User-Centric Clustering Pilot Assignment Stochastic Optimization
- Format(s):
- Medium: X
- Location:
- Kuala Lumpur, Malaysia
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
One of the main skills of engineers is to be able to solve problems. It is generally recognized that real-world engineering problems are inherently ill-structured in that they are complex, defined by non-engineering constraints, are missing information, and contain conflicting information. Therefore, it is very important to prepare future engineering students to be able to anticipate the occurrence of such problems, and to be prepared to solve them. However, most courses are taught by academic professors and lecturers whose focus is on didactic teaching of fundamental principles and code-based design approaches leading to predetermined “right” answers. Most classroom-taught methods to solve well-structured problems and the methods needed to solve ill-structured problems are strikingly different. The focus of our current effort is to compare and contrast the problem solving approaches employed by students, academics and practicing professionals in an attempt to determine if students are developing the necessary skills to tackle ill-structured problems. To accomplish this, an ill-structured problem is developed, which will later be used to determine, based on analysis of oral and written responses of participants in semi-structured interviews, attributes of the gap between student, faculty, and professional approaches to ill-structured problem solving. Based on the results of this analysis, we will identify what pedagogical approaches may limit and help students’ abilities to develop fully-formed solutions to ill-structured problems. This project is currently ongoing. This work-in-progress paper will present the study and proposed methods. Based on feedback obtained at the conference from the broader research community, the studies will be refined. The current phase includes three parts, (1) problem formulation; (2) protocol development; and (3) pilot study. For (1), two different ill-structured problems were developed in the Civil Engineering domain. The problem difficulty assessment method was used to determine the appropriateness of each problem developed for this study. For (2), a protocol was developed in which participants will be asked to first solve a simple problem to become familiar with the interview format, then are given 30 minutes to solve the provided ill-structured problem, following a semi-structured interview format. Participants will be encouraged to speak out loud and also write down what they are thinking and their thought processes throughout the interview period. Both (1) and (2) will next be used for (3) the pilot study. The pilot study will include interviewing three students, three faculty members and three professional engineers. Each participant will complete both problems following the same protocol developed. Post-interview discussion will be held with the pilot study participants individually to inquire if there were any portions of the tasks that are unclearly worded or could be improved to clarify what was being asked. Based on these results the final problem will be chosen and refined.more » « less
-
This paper deals with the unavailability of full CSI in ultra-dense user-centric TDD C-RAN. To reduce the channel training overhead, we consider the incomplete CSI case, where only large-scale inter-cluster CSI is available. Channel estimation for intra-cluster CSI is also considered, where we formulate a joint pilot allocation and user equipment (UE) selection problem to maximize the number of admitted UEs with fixed number of pilots. A novel pilot allocation algorithm is proposed by considering the multi-UE pilot interference. Then, we consider robust beam-vector optimization problem subject to UEs' data rate requirements and fronthaul capacity constraints, where the channel estimation error and incomplete inter-cluster CSI are considered. Simulation results demonstrate its superiority over the existing algorithms.more » « less
-
In wireless networked control systems, ensuring predictable communication link reliabilities among sensors, controllers, and actuators is critical. In such scenarios, different data gathered at the application layer of each sender require different packet delivery ratios (i.e., reliabilities). The lower layers try to accommodate these requests by first mapping each of them into a service level and then deliver the associated data packets to the receiver at the mapped service level. Due to resource constraints and maintenance overhead, the number of supported service levels is usually limited. An important question is then how to determine the set of service levels to maintain and how to map each request to an appropriate service level, such that the requested reliabilities are guaranteed and the total cost of mapping is minimized? We formally formulate this as an optimal request clustering problem since each service level acts as a cluster and can host multiple requests. In particular, we formulate the Migratory Clustering Problem and the Non-Migratory Clustering Problem, depending on whether a request can migrate from one service level to another after its initial assignment. We propose two optimal algorithms to solve both problems.more » « less
-
Dynamic user equilibrium (DUE) is the most widely studied form of dynamic traffic assignment (DTA), in which road travelers engage in a non-cooperative Nash-like game with departure time and route choices. DUE models describe and predict the time-varying traffic flows on a network consistent with traffic flow theory and travel behavior. This paper documents theoretical and numerical advances in synthesizing traffic flow theory and DUE modeling, by presenting a holistic computational theory of DUE, which is numerically implemented in a MATLAB package. In particular, the dynamic network loading (DNL) sub-problem is formulated as a system of differential algebraic equations based on the Lighthill-Whitham-Richards fluid dynamic model, which captures the formation, propagation and dissipation of physical queues as well as vehicle spillback on networks. Then, the fixed-point algorithm is employed to solve the DUE problems with simultaneous route and departure time choices on several large-scale networks. We make openly available the MATLAB package, which can be used to solve DUE problems on user-defined networks, aiming to not only facilitate benchmarking a wide range of DUE algorithms and solutions, but also offer researchers a platform to further develop their own models and applications. The MATLAB package and computational examples are available online.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/GLOBECOM54140.2023.10437645
