宽带OFDM系统的干扰协调技术

在基于OFDM的蜂窝移动通信网络中,影响系统性能的主要干扰来自小区间干扰。小区间的干扰协调技术是提高系统性能的有效手段之一。首先,给出了干扰协调的软频率复用原理。然后,按照资源在时域上调度粒度的不同将干扰协调技术分为三类,即静态干扰协调、动态干扰协调和半静态干扰协调,并分析了各自的优缺点。最后,通过两个干扰协调方案实例说明干扰协调在3G长期演进系统中的应用。     

最大化SLNR及软频率复用的比例公平调度算法

针对 LTE-Advanced 系统中小区间干扰及用户公平性问题,提出了最大化信漏噪比(SLNR)及软频率复用的比例公平调度算法(SLNR–SFR–PF)。该算法通过基于最大化 SLNR的分布式预编码和软频率复用的方法抑制小区间干扰,并结合比例公平调度算法,提高用户的公平性。仿真结果表明,与 SLNR–PF 算法相比,SLNR–SFR–PF 算法使系统容量提高了约7.9%,同时,小区边缘的平均用户数据速率提高了11.5%。     

一种抑制小区间干扰的比例公平调度算法

针对LTE-Advanced系统中小区间干扰及用户公平性问题,提出了基于多小区联合预编码和静态功率控制的比例公平(MCPPC-PF)调度算法。通过干扰空间迫零和静态控制发射功率的方法抑制小区间干扰,并结合比例公平(PF)调度算法,提高用户的公平性。仿真结果表明,与传统算法相比,MCPPC-PF算法提升系统容量的同时还提高了用户的公平性;与基于多小区联合预编码和静态功率控制的最大化吞吐量调度算法相比,MCPPC-PF算法在系统容量损失了4.6%的情况下,边缘用户容量提高了约45%。     

软分数频率复用在4G通信系统中应用

针对4G移动通信系统提出的提高频谱利用率、同频组网的需求，文章从频率复用问题入手，提出了一种软分数频率复用方案。软分数频率复用方案包括3种表现形式，在实际应用中，可以根据物理层链路增益选择适当的表现形式。文章以第2种表现形式为例介绍了采用该方案的频率复用方法。研究表明，使用软分数频率复用方案，系统的频率复用系数可以达到1／3～1。软分数频率复用方案解决了同频组网问题，并已经在上海4G实验网中得到了良好的应用。     

LTE系统频率复用方式的探讨

为了提高LTE系统容量而必须要采取有效的频率复用技术,所以LTE系统中干扰协调的手段之一就是频率复用技术,本文对多种频率复用方式进行了讨论,并进行了总结。     

软分数频率复用

针对4G移动通信系统提出的提高频谱利用率、同频组网的需求,文章从频率复用问题入手,提出了一种软分数频率复用方案。软分数频率复用方案包括3种表现形式,在实际应用中,可以根据物理层链路增益选择适当的表现形式。文章以第2种表现形式为例介绍了采用该方案的频率复用方法。研究表明,使用软分数频率复用方案,系统的频率复用系数可以达到1/3～1。软分数频率复用方案解决了同频组网问题,并已经在上海4G实验网中得到了良好的应用。     

移动WiMAX系统的增强无线技术

本文从多天线和干扰协调调度两个方面介绍移动WiMAX系统的增强无线技术,特别介绍了多天线技术中的协作空分复用和干扰协调技术中的软频率复用。     

密集室内LTE Femtocell部署的干扰抑制技术

介绍静态频率复用及其干扰抑制技术,提出一种半静态干扰抑制技术方案,即软FFRn分数频率复用方案,并基于业界领先的室内无线网络规划优化工具iBuildNet对所提方案进行系统级仿真,评估方案性能。结果表明,与广泛应用于宏蜂窝的FFR-3传统方法相比,采用文中提出的干扰抑制技术更有利于小区边缘用户,提高系统整体的吞吐量。     

3G及其演进系统的无线资源管理技术分析

文章从动态资源调度、呼叫接纳控制等方面,就3G和B3G/4G系统的无线资源管理策略进行了对比分析,并提出了后续研究的重点,以及结合干扰协调和干扰消除技术抑制小区间干扰的频率复用方案等新的思路。     

LTE系统的小区间干扰协调分析

OFDM较好地解决了小区内信道之间的自我干扰,但仍然存在蜂窝移动通信系统小区间干扰的问题。文章着重从资源调度的角度,对小区间干扰协调的技术进行分析研究,按资源约束条件的不同,分析对比了两类小区间干扰协调的软频率复用技术方法。     

Radio resource allocation for interference management in mobile broadband OFDMA based networks

This paper focuses on the inter‐cell interference (ICI) management problem in the downlink channel for mobile broadband wireless OFDMA‐based systems. This subject is addressed from the standpoint of different interrelated resource allocation mechanisms operating in multi‐cell scenarios in order to exploit frequency and multi‐user diversity: ICI coordination/avoidance and adaptive subcarrier and power allocation. Even though these methods can be applied in a stand‐alone way, a significant performance improvement is achieved if they are jointly designed and operate in a combined basis. Several alternatives for mixed frequency and power ICI coordination schemes are proposed in this paper. Connected with a proper power mask‐based design, the potential gain of a flexible frequency sectorization solution, halfway between fractional/soft frequency reuse and pure frequency sectorization, is explored. The main objective is to outperform fractional/soft frequency reuse offering an attractive trade‐off between cell‐edge user data rates and average cell throughput. Proposals concerning ICI coordination/avoidance have been evaluated in combination with several heuristic adaptive subcarrier and power allocation algorithms. Copyright © 2009 John Wiley & Sons, Ltd.     

Frequency Reuse Techniques with a Distributed Antenna System

The performance of cellular networks is strongly limited by inter-cell interference. In order to reduce this interference, several techniques have been proposed, e.g., the frequency reuse techniques and distributed antenna system (DAS). This paper investigates the combinations of hard frequency reuse (HFR) and soft frequency reuse (SFR) techniques with DAS in a unique cell architecture, which are called DAS–HFR and DAS–SFR, respectively. This paper analytically quantifies the performance of the downlink multi-cell for DAS–HFR and DAS–SFR in terms of the average spectral efficiency. This also shows, the most appropriate frequency reuse technique depends not only on the average achievable data rate inside the cell, but also on the guaranteed achievable data rate (the minimum achievable data rate which is necessary to be obtained regardless of geographic location). The results show that DAS–SFR improves the achievable data rate of cell edges in a multi-cell environment as compared to a DAS–HFR when frequency reuse factor 1 is utilized. The results also show that DAS–SFR significantly increases the system capacity as compared to the DAS–HFR when frequency reuse factor 3 is utilized.     

多小区OFDMA系统中分数频率复用方法的优化分析

在以OFDMA为基本多址方式的第四代移动通信系统中,频率复用作为提高系统性能的有效方法受到了广泛的关注,特别是分数频率复用和软频率复用。然而,如何进一步优化基于这些频率复用方法的OFDMA系统还有待研究。本文分析了多小区OFDMA系统负载和频率集合分配比例对小区总吞吐量和小区边缘用户数据速率的影响。同时,给出了在保证小区边缘用户服务质量的条件下,使小区总吞吐量最优的小区中心频率分配比例,并用仿真进行验证。仿真结果还表明了,随着分配比例的增大,小区总吞吐量先增大后减小。     

LTE系统软频率复用改进方案性能评估

软频率复用(SFR)被认为是一种有效的频率复用方案,可以协调小区间干扰,同时也可保持频谱效率.通过考虑各种业务负载及不同功率比的配置,研究在LTE下行传输时SFR的性能,除了小区边缘用户的性能,还评估了整个小区性能和小区中心用户性能,通过仿真对SFR的优势和局限性进行了较全面的验证,并与经典频率复用方案进行了比较.     

Reduction of Outage Probability due to Handover by Mitigating Inter‐cell Interference in Long‐Term Evolution Networks

The burgeoning growth of real‐time applications, such as interactive video and VoIP, places a heavy demand for a high data rate and guarantee of QoS from a network. This is being addressed by fourth generation networks such as Long‐Term Evolution (LTE). But, the mobility of user equipment that needs to be handed over to a new evolved node base‐station (eNB) while maintaining connectivity with high data rates poses a significant challenge that needs to be addressed. Handover (HO) normally takes place at cell borders, which normally suffers high interference. This inter‐cell interference (ICI) can affect HO procedures, as well as reduce throughput. In this paper, soft frequency reuse (SFR) and multiple preparations (MP), so‐called SFRAMP, are proposed to provide a seamless and fast handover with high throughput by keeping the ICI low. Simulation results using LTE‐Sim show that the outage probability and delay are reduced by 24.4% and 11.9%, respectively, over the hard handover method — quite a significant result.     

Performance of power control in inter-cell interference coordination for frequency reuse

To mitigate inter-cell interference in 3G evolution systems,a novel inter-cell interference coordination scheme called soft fractional frequency reuse is proposed in this article,which enables to improve the data rate in cell-edge.On this basis,an inter-cell power control is presented for the inter-cell interference coordination,and the inter-cell balanced signal to interference plus noise ratio(SINR) among users is established for power allocation,which enables mitigation of inter-cell interference.Especia...     

Distributed proportional fair frequency allocation across multiple base stations

The problem of distributed proportional fair inter-cell frequency allocation for flat-structured cellular systems is studied in this paper. We firstly propose a framework of the frequency allocation in which the whole frequency allocation process is decomposed into many consecutive stages, then identify that for each stage the key is to find the Maximum Weight Independent Set (MWIS) in a given weighted conflict graph in the distributed manner. A new distributed algorithm for MWIS is described in which each node iteratively exchanges messages with neighbors. With this distributed MWIS algorithm, a new distributed proportional fair frequency allocation scheme is presented. The performance of the proposed algorithm is tested in computer experiments simulating the Long Term Evolution (LTE) cellular systems. Simulation results show the performance of the proposed distributed proportional fair frequency allocation scheme is comparable with the centralized ones.     

Joint interference coordination approach in femtocell networks for QoS performance optimization

Future heterogeneous networks with dense cell deployment may cause high intercell interference. A number of interference coordination (IC) approaches have been proposed to reduce intercell interference. For dense small‐cell deployment with high intercell interference between cells, traditional forward link IC approaches intended to improve edge user throughput for best effort traffic (ie, file transfer protocol download), may not necessarily improve quality of service performance for delay‐sensitive traffic such as voice over long‐term evolution traffic. This study proposes a dynamic, centralized joint IC approach to improve forward link performance for delay‐sensitive traffic on densely deployed enterprise‐wide long‐term evolution femtocell networks. This approach uses a 2‐level scheme: central and femtocell. At the central level, the algorithm aims to maximize network utility (the utility‐based approach) and minimize network outage (the graphic‐based approach) by partitioning the network into clusters and conducting an exhaustive search for optimized resource allocation solutions among femtocells (femto access points) within each cluster. At the femtocell level, in contrast, the algorithm uses existing static approaches, such as conventional frequency reuse (ReUse3) or soft frequency reuse (SFR) to further improve user equipment quality of service performance. This combined approach uses utility‐ and graphic‐based SFR and ReUse3 (USFR/GSFR and UReUse3/GReUse3, respectively). The cell and edge user throughput of best effort traffic and the packet loss rate of voice over long‐term evolution traffic have been characterized and compared using both the proposed and traditional IC approaches.     

一种适用于快衰落信道的ICI抑制方案

针对高速移动环境下多普勒频偏造成信道的快衰落和正交频分复用(OFDM)系统中子载波间干扰(ICI)的问题,提出了一种适合快衰落环境的OFDM系统子载波间干扰抑制算法。此算法用线性变化模型来近似一个OFDM符号周期内的信道冲激响应,并以此为基础采用迭代MMSE均衡方法抑制载波间干扰。分析和仿真结果表明,此方法能有效地保证载波间的正交性,从而改善了OFDM系统的误码率(BER)性能。