4G中的新技术及其与3G的比较

第四代移动通信系统(4G)是多种无线技术的综合系统，它融合了现有第三代移动系统(3G)的增强型技术，集3G网络技术和无线LAN系统为一体。首先简述了4G的特点，然后将4G与3G系统进行了比较，并详细讨论了4G中采用的新技术，最后介绍了国内外对4G的研究现状。     

QoS-Based Admission and Load Control Algorithm for Integrated Voice/Data Services over Wideband CDMA

In order to maximize the system capacity in third generation wireless system, efficient call admission and load control algorithms are required to handle the different services having diverse traffic patterns and Quality of Service (QoS) requirements. We propose an admission and load control algorithm that considers the network loading information, propagation conditions, and the interference level. The algorithm takes advantage of the new features of third-generation (3G) wireless system such as the reported pilot measurements, auxiliary pilot for smart antennas, and variable spreading gain. Dynamic resource allocation is employed to scale the amount of the assigned radio resources taking the network loading conditions and channel characteristics into consideration. The results show that integrating the voice service and the data service with high transmission rate (>144 Kbps) can be realized using efficient resource management.     

Joint packet scheduling and dynamic base station assignment for CDMA data networks

In current code division multiple access (CDMA) based wireless systems, a base station (BS) schedules packets independently of its neighbours, which may lead to resource wastage and the degradation of the system's performance. In wireless networks, in order to achieve an efficient packet scheduling, there are two conflicting performance metrics that have to be optimized: throughput and fairness. Their maximization is a key goal, particularly in next-generation wireless networks. This paper proposes joint packet scheduling and BS assignment schemes for a cluster of interdependent neighbouring BSs in CDMA-based wireless networks, in order to enhance the system performance through dynamic load balancing. The proposed schemes are based on sector subdivision in terms of average required resource per mobile station and utility function approach. The fairness is achieved by minimizing the variance of the delay for the remaining head-of-queue packets. Inter-cell and intra-cell interferences from scheduled packets are also minimized in order to increase the system capacity and performance. The simulation results show that our proposed schemes perform better than existing schemes available in the open literature. Copyright © 2007 John Wiley & Sons, Ltd.     

W-CDMA收发器的功率管理解决方案

3G的普及使手机功能日益增多，对手机电池能量的要求也不断提升。本文在此背景下提出了针对W—CDMA收发器的功率管理方案，即采用由电压控制的DC／DC转换器来动态调节射频功放的电源电压，从而获得更高的功率附加效率。     

基于WCDMA上行链路的多信标辅助定位

本文提出了在蜂窝小区中加入辅助定位信标实现W-CDMA环境下的移动定位,并提出了一种实用性强的定位实现算法。该方案另一优点是实现代价小,一改传统需要多个基站参与定位的做法,从而避免了WCDMA中相邻小区之间的同信道干扰。本文还给出了利用该实现方案和算法在W-CDMA环境下的仿真结果和性能分析。     

射频功率放大器前馈宽频带线性化技术的研究

针对第三代移动通信中的功率放大器线性化技术,提出了改善线性化带宽的解决方案。该方案通过减少前馈环路中的时延波动来提高互调失真分量的宽带对消特性,同时采用相关复解调来检测残留导频。研制了射频功率放大器,前馈对消环路和信号检测电路,用数字信号处理芯片实现了相关的自适应算法。仿真和实验结果表明,该技术能够在宽频带内对LDMOS高功率放大器的三阶互调(IMD3)改善25dB,对四载波的W-CDMA信号的邻近信道功率泄漏比(ACLR)改善17dB。     

W-CDMA手机用功率放大器的ACPR不对称性研究

分析了偶次交调产生的低频因素对临近通道泄漏功率比(ACPR)不对称性的影响;根据实际功率放大器结构提出了一种等效低通滤波器模型;仿真验证了该低通滤波器的带宽和阶数对ACPR不对称性的影响;测试中通过改变该低通滤波器的带宽和阶数,使得ACPR不对称性改善了3.72dB,同时ACPR降低了2.95dB,提高了功放的线性度.     

W-CDMA Uplink Capacity and Interference Statistics of Rural Highways Cross-Shaped Microcells

The capacity and the interference statistics of the sectors of the cross-shaped W-CDMA cell are studied using an analytical approach. A model of 49 cells is used to analyse the uplink, which limits the capacity. The cells are assumed to exist in rural zones. The capacity and the interference statistics of the microcell are studied for different sector ranges and different antenna sidelobe levels.     

基于ADS环境下的W-CDMA信号仿真

主要介绍了一种新的基于ADS(AdvancedDesignSystem)环境下的W-CDMA信号产生方法,对其中所运用的多信道传输,码分多址以及脉冲成型技术做了重点分析,并在安捷伦公司提供的ADS仿真工具上对信号的产生过程进行了仿真,特别研究了内插系数对通信系统邻道功率比的影响。结果表明系统产生的信号各项性能指标均很好地模拟了实际信号,这将有助于信号的进一步分析和测试以及对通信系统的性能进行深入研究。     

一种改善W-CDMA手机用功率放大器线性度的新方法

分析了偶次交调产生的低频因素对临近信道泄漏功率比(ACPR)不对称性的影响;根据实际功率放大器结构提出了一种等效低通滤波器模型;仿真验证了该低通滤波器的带宽和阶数对ACPR不对称性的影响;测试中通过改变该低通滤波器的带宽和阶数,使得ACPR不对称性改善了3.72dB,同时ACPR降低了2.95dB,有效地改善了功率放大器的线性度。