Cell Edge Spectrum Efficiency Research Articles

A Practical Semidynamic Clustering Scheme Using Affinity Propagation in Cooperative Picocells

Coordinated multipoint (CoMP) is corroborated to be an effective technology in mitigating cochannel interference (CCI) and enhancing system performance in picocell systems, which consist of a large number of pico base stations (BSs). In picocell systems, effective CoMP clustering schemes could provide significant gains of system performance such as throughput and cell-edge spectrum efficiency (SE). Moreover, an intrinsic problem of densely deployed networks is the cost of signaling overhead and data exchange between BSs in clusters. In this paper, a novel semidynamic clustering scheme based on affinity propagation for CoMP-Pico is presented to maximize user SE and throughput under the constraint of backhaul cost. Our proposed scheme consists of online and offline stages that can achieve good performance and low complexity. Simulation results show that the proposed scheme yields significant gains of SE and throughput and low running time compared with the existing clustering schemes.

Performance Analysis and Evaluation of Deployment in Small Cell Networks

Small cells are deployed in Heterogeneous Networks (HetNet) to improve overall performance. These access points can provide high-rate mobile services at hotspots to users. In a Small Cell Network (SCN), the good deployment of small cells can guarantee the performance of users on the basis of average and cell edge spectrum efficiency. In this paper, the performance of small cell deployment is analyzed by using system-level simulations. The positions of small cells can be adjusted according to the deployment radius and angle. Moreover, different Inter-Cell Interference Coordination (ICIC) techniques are also studied, which can be implemented either in time domain or in frequency domain. The network performances are evaluated under different ICIC techniques when the locations of Small evolved Nodes (SeNBs) vary. Simulation results show that the average throughput and cell edge throughput can be greatly improved when small cells are properly deployed with the certain deployment radius and angle. Meanwhile, how to optimally configure the parameters to achieve the potential of the deployment is discussed when applying different ICIC techniques.

A Multilevel Soft Frequency Reuse Technique for Wireless Communication Systems

A multilevel soft frequency reuse (ML-SFR) scheme and a resource allocation methodology are proposed for wireless communication systems. In the proposed ML-SFR scheme, there are $2\hbox{N}$ power density limit levels, achieving a better interference pattern and further improving the cell edge and the overall data rate compared with the traditional two-level SFR scheme. The detailed design of an eight-level SFR scheme is demonstrated. Numerical results show that the cell-edge spectrum efficiency is increased to five times of that of reuse 1, and the overall spectrum efficiency is improved by 31%. The ML-SFR can be utilized in the current 4G system and would be a candidate key technology for future 5G systems.

A Utility-Based Joint Resource Allocation Approach for Multi-Service in CoMP Networks

Coordinated multi-point (CoMP) joint transmission is considered as a key technique to mitigate inter-cell interference and improve the cell-edge performance in 3GPP LTE-Advanced. In this paper, a utility-based joint resource allocation approach is proposed to support CoMP joint transmission in orthogonal frequency division multiple access systems. Two different utility functions are considered with diverse quality of service provisioning. The objective is to maximize the sum utility of a clustered CoMP network, considering mixed real-time voice over IP (VoIP) and best-effort (BE) traffic patterns. A centralized joint resource allocation algorithm is proposed by decoupling the optimization problem into per-subchannel subproblems. Further more, a greedy user selection based low-complexity algorithm is proposed for practical implementation. For the sake of performance comparison, the proportional-fair based joint scheduling, as well as two non-coordinated scheduling schemes are also evaluated. Via system-level simulation we show that the proposed algorithms not only substantially improve the cell-edge spectrum efficiency of BE users, but also significantly decrease the packet drop ratio and call outage ratio of VoIP users.

On frequency reuse in cooperative distributed antenna systems

The cooperative distributed antenna system (DAS) is one of the promising systems for future high-data-rate mobile communications, since the DAS can reduce the radio transmission distance between the transmitter and the receiver by distributing multiple remote antenna units in the traditional cellular network. In order to achieve high spectrum efficiency in the DAS, frequency reuse is considered. In this article, two values of frequency reuse factor are considered in conjunction with cooperative spatial diversity. In order to show the advantage of introducing frequency reuse, the performance of the DAS with frequency reuse is compared with that without frequency reuse. Results show that the DAS with frequency reuse outperforms the DAS without frequency reuse in the average spectrum efficiency per sector and the cell edge spectrum efficiency. The DAS with larger frequency reuse factor outperforms the DAS with smaller frequency reuse factor for a large range of signal-to- noise ratio.

Performance Comparison Between Distributed Antenna and Microcellular Systems

The microcellular system and distributed antenna system (DAS) are two promising systems for future high data rate wireless communications, since both systems can reduce the radio transmission distance between the transmitter and the receiver. This paper aims to compare the average spectrum efficiency and the cell edge spectrum efficiency between the two cellular systems in the downlink transmission. In order to achieve high spectrum efficiency, frequency reuse and/or spatial diversity are exploited in these two systems. The performances between the two cellular systems are theoretically compared in a network topology with seven macrocells, each of which has seven hexagonal sectors (or microcells). Moreover, the approach of antenna unit selection in the DAS for spatial diversity is presented. Numerical results show that the average spectrum efficiency per sector and the cell edge spectrum efficiency in the microcellular system are better than those in the DAS without frequency reuse. However, when the frequency reuse is considered in the DAS, the DAS outperforms the microcellular system in both of the average and cell edge spectrum efficiencies.

Layered OFDMA and Its Radio Access Techniques for LTE-Advanced

This paper proposes applying the Layered Orthogonal Frequency Division Multiple Access (OFDMA) radio access scheme and its radio access techniques to LTE (Long-Term Evolution)-Advanced to satisfy its system requirements, which are much stricter than those of the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN). Layered OFDMA comprises layered transmission bandwidth assignment (bandwidth is assigned to match the required data rate), a layered control signaling structure, and support for layered environments for both the downlink and uplink. Especially in the uplink, an adaptive multi-access scheme with hybrid single-carrier and multicarrier based radio access is applied. Layered OFDMA radio access will support all the functionalities specified in Release 8 LTE and later enhancements. Key radio access techniques such as fast inter-cell radio resource management that takes advantage of remote radio equipment (RRE) so as to realize inter-cell orthogonality, multi-antenna transmission with more antennas, and coverage enhancing techniques are used to achieve a high level of capacity and cell-edge spectrum efficiency.