UTRA/FDD RF Transceiver Requirements

Unified RF requirements are derived for an UMTS Terrestrial RadioAccess/Frequency Division Duplex (UTRA/FDD) compliant mobile transceiver. Aset of transceiver requirements are proposed with consideration to systemissues including duplex aspects. From these design-compatible requirements areproposed for each functional block in the transceiver.     

Improving secret key generation for wireless communications in FDD mode

Most recent research on channel‐based key generation oriented to time division duplex system because the channel reciprocity feature is applied directly for secret key generation. Most of commercial cellular systems depend on frequency division duplex (FDD) systems. In this paper, we investigate the impact of uplink and downlink of FDD systems for the generation of shared secret keys between two parties in the presents of passive eavesdropper. In addition, we are considering improving the rate of the secret key for wireless communication in FDD mode. The main idea is to use the fading coefficient of the channels between the relay and other parties as an additional random common source for the secret key generation. Also, explore the using of channel estimation techniques to reduce the channel training sequence and study its effect on the generation of shared key for wireless communications in FDD mode. We derive the upper bound of the generated shared key rate for four scenarios and give numerical examples to reveal the performance of our suggested improvement approaches.     

The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels

In centralized massive multiple-input multiple-output (MIMO) systems, the channel hardening phenomenon can occur, in which the channel behaves as almost fully deterministic as the number of antennas increases. Nevertheless, in a cell-free massive MIMO system, the channel is less deterministic. In this paper, we propose using instantaneous channel state information (CSI) instead of statistical CSI to obtain the power control coefficient in cell-free massive MIMO. Access points (APs) and user equipment (UE) have sufficient time to obtain instantaneous CSI in a slowly time-varying channel environment. We derive the achievable downlink rate under instantaneous CSI for frequency division duplex (FDD) cell-free massive MIMO systems and apply the results to the power control coefficients. For FDD systems, quantized channel coefficients are proposed to reduce feedback overhead. The simulation results show that the spectral efficiency performance when using instantaneous CSI is approximately three times higher than that achieved using statistical CSI.     

Interference analysis and capacity for forward link 3G CDMA network with adaptive antennas

In code division multiple access (CDMA) systems, the capacity of forward link (FL) communication to mobile receivers is limited primarily by co‐channel interference (CCI). Adaptive antenna arrays (AAAs) that use antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this limitation. For a 3G CDMA cellular network, where each BS equipped with an AAA serves mixture of voice and data users within its coverage, we study FL capacity and investigate the effects of different factors (array topology, multipath angle spread, data rate, and beamforming algorithm) on this capacity under Rayleigh fading channel. By modeling the instantaneous signal‐to‐interference power ratio received at the mobile, we derive the system outage equation that considers blocking of either desired voice or data user. Simulation results show that for the same element spacing and number of antenna elements per cell, the uniform circular array (UCA) topology results in larger capacity than the sectorized uniform linear array (ULA) topology does, and that a larger angle spread or data user rate reduces FL capacity. Copyright © 2007 John Wiley & Sons, Ltd.     

ATM‐based wireless broadband access in the local loop

Broadband networks using wireless transmission techniques are a quick and flexible means of implementing subscriber access. Unoccupied frequency bands with sufficient bandwidth to allow the transmission of digital signals at very high bit rates are found only in the microwave bands. Because the path loss is fairly high at these frequencies, the diameter of radio cells is limited to a maximum of a few kilometres. This results in a microcellular system, which is best implemented in the form of a point‐to‐multipoint system, where one radio‐base station serves all subscribers registered in that radio cell. An interactive, broadband, ATM‐based radio local loop has undergone successful trials in Munich. Copyright © 2001 John Wiley & Sons, Ltd.     

NB-IoT联合组网及优化策略浅析

随着物联网业务的高速发展,以广覆盖、大连接、低功耗和低成本为特点的窄带物联网(NB-IoT)技术成为运营商关注的焦点。本文从物联网业务类型、NB-IoT发展现状和关键技术为出发点,着重分析了NB-IoT技术的演进趋势和部署方案,最后针对其面临的发展挑战为运营商提供了参考建议。     

一种FDD1800 4T4R扇区劈裂方法的研究及应用

随着4G流量的迅猛增长以及目前TDD频段满扩,FDD1800扩频至20M后仍无法满足用户良好感知的现状,本文研究通过FDD1800 4T4R扇区劈裂的新方法解决区域容量问题。现网验证结果表明扇区劈裂技术不仅具有对现网改动小、施工难度低、部署开通快的优点,而且在5G分流效果有限的部署初期阶段,该方案能用较低的成本有效解决热点区域的高负荷问题,达到降本增效的目的。     

第三代移动通信的小区规划（上）

对第三代移动通信中的WCDMA系统小区规划时基站数目的确定作了全面的阐述。首先从满足话务量角度出发计算最小基站数目，然后从覆盖角度出发计算出最小基站数目，最后综合两种计算方法的结果。     

第三代移动通信的小区规划（下）

对第三代移动通信中的WCDMA系统小区规划中基站数目的确定作了全面的阐述。首先从满足话务量角度出发计算最小基站数目，然后从覆盖角度计算出最小基站数目，最后综合两种计算方法的结果。     

VDSL数字用户环路的调制方法分析

首先介绍了超高速数字用户环路（VDSL）的基本构造和线路编码，然后分析了VDSL的主要两种调制方法，即时分复用（TDD）方式和频分复用（FDD）方式。