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.     

Capacity of Generalized UTRA FDD Closed-Loop Transmit Diversity Modes

Transmit diversity techniques have received a lot of attention recently, and open-loop and closed-loop downlink transmit diversity modes for two transmit antennae have been included into universal terrestrial radio access (UTRA) frequency division duplex (FDD) specification. Closed-loop modes provide larger system capacity than open-loop modes, but they need additional side information of the downlink channel in the transmitter. In FDD systems this requires a separate feedback channel. Quantization of channel state information (CSI) in closed-loop transmit diversity schemes decreases the performance when compared to a closed-loop system where the transmitter has access to complete CSI. In this paper, we analyze the effect of quantization of CSI and deduce approximate capacity formulae for closed-loop transmit diversity schemes that are generalizations of the closed-loop schemes included in UTRA FDD specification. Moreover, we calculate approximation error and show by simulations that our approximation is tight for flat Rayleigh fading environments with and without fast transmit power control.     

Sustainable simultaneous communications in ad-hoc networks using smart antenna systems

This article proposes an analytical model for evaluating the number of simultaneous communications that can be sustained by an ad-hoc network in which the nodes are equipped with fully adaptive smart antennas. The presented mathematical framework adopts realistic models for the antenna radiation pattern and the channel behavior, and is able to take into account the network topology and the characteristics of the medium access control (MAC) protocol in the spatial domain. The model is employed to investigate the impact of the spatial channel model and of the angular spread on network performance. Additionally, this article examines the influence of the transmission policy of the control and data packets of the MAC layer on the number of simultaneous communications.     

Simulation and analysis of node throughput using smart antenna in wireless mesh networks

Smart antenna technology is introduced to wireless mesh networks. Smart antennas based wider-range access medium access control (MAC) protocol (SWAMP) is used as MAC protocol for IEEE 802.11 mesh networks in this study. The calculation method of node throughput in chain and arbitrary topology is proposed under nodes fairness guarantee. Network scale and interference among nodes are key factors that influence node throughput. Node distribution pattern near the gateway also affects the node throughput. Experiment based on network simulator-2 (NS-2) simulation platform compares node throughput between smart antenna scenario and omni-antenna scenario. As smart antenna technology reduces the bottle collision domain, node throughput increases observably.     

Generalized diversity combining of energy harvesting multiple antenna relay networks: outage and throughput performance analysis

In this paper, the generalized diversity combining of an energy constrained multiple antenna decode-and-forward relay network is considered. Using power splitting and time switching architectures in consort with diversity combining at the relay, six protocols are proposed, i.e., power splitting with selection combining (PSSC), power splitting with maximum ratio combining (PSMRC), power splitting with generalized selection combining (PSGSC), time switching with selection combining (TSSC), time switching with maximum ratio combining (TSMRC), and time switching with generalized selection combining (TSGSC). The outage probability and throughput performance of each protocol is analyzed by first developing the closed form analytical expressions and then verifying these through the Monte Carlo simulation method. Simulation results show that system performance improves both with increasing the number of antennas and decreasing the distance between the source and relay. The TSSC/TSMRC/TSGSC protocols yield better outage performance whereas the PSSC/PSMRC/PSGSC protocols achieve relatively higher throughput performance. Finally, the effects of power splitting ratio, energy harvesting time ratio, energy conversion efficiency, sample down conversion noise, and the target signal-to-noise ratio on system performance are analyzed and presented.     

Model based antenna array calibration for smart antenna systems

Model based antenna array calibration is used to remove the antenna array errors or predict the element patterns from the array manifold measured at a small number of directions. The experimental results show that this works very well for one sector angle region even in the presence of modelling errors     

智能天线中导频符号辅助的载波频偏估计

首先定量分析了智能天线的阵元和导频符号数目增减对频偏估计性能的影响;然后借助于自适应阵加权结构,提出了一种存在共信道干扰(CCI)时,导频辅助估计频偏的新算法,该方法的自适应权只是中间变量,所以并不需要系统真正采用自适应结构,也不需要已知天线阵列流形.计算机仿真表明,该算法可以充分地利用多阵元和导频符号,有效抑制了CCI,使频偏估计性能接近于克莱美-罗界.     

智能天线在TD-SCDMA系统中的应用研究

分析了TD-SCDMA系统中引入智能天线后空分信道的分配问题,根据空间角度相近且与基站之间的距离相差悬殊的用户使用不同的传统信道的准则,讨论了一种高效的基于信干比的空分信道分配搜索算法,用于解决传统信道复用中的组合寻优问题。最后针对该搜索算法进行仿真,分析结论并说明系统性能的改善。     

A real-time DOA-based smart antenna processor

We designed, built, and tested a real-time processor for a direction-of-arrival-based smart antenna GSM 1800 base station with eight half-wavelength spaced antenna elements. Its processing steps include direction-of-arrival (DOA) estimation, user identification, tracking, beamforming, and signal reconstruction. We demonstrate that the accuracy of DOA estimation is not of primary concern, but the robustness is. This can be assessed by a new parameter, the estimation range. Tracking of reliable user DOAs only, increases the robustness against interference. Our tracking concept is compatible with frequency hopping. We quantify the benefits of smart antennas by the statistics of the gain in carrier-to-interference ratio (C/I) and in signal-to-noise ratio (SNR), both measured at the 90 or 99% levels with actual transmitted data. In an urban environment with large angular spread and overlap of user and interferer signals, the C/I gain is as high as 18 dB. Interferer ing increases the C/I gain only slightly, but enhances robustness against angular spread, particularly if broad s are applied. Separating SNR gain in its contributions due to beamforming and diversity gives valuable insight into the way of operation. In uplink, the processor can exploit angular diversity. The entire suite of processing steps is done within less than 1 ms, demonstrating that sophisticated DOA-based smart antenna processing is feasible in real time. Our solution does not require any change in the GSM standard.     

一种新的智能天线波束形成算法

在DS/CDMA系统中采用智能天线技术可以增加系统的容量,提高抗干扰性能.智能天线技术的核心是波束形成算法,基于遗传算法提出了一种新的智能天线波束形成算法,算法采用了内插和外推两种交叉算子,克服了遗传算法的早熟收敛问题,提高了全局收敛能力.研究结果表明,提出的智能天线波束形成算法具有良好的收敛性和稳定性,可用于DS/CDMA系统抵抗干扰的影响.     

智能天线技术系列讲座(Ⅰ)原理及优秀解决方案

在无线通信系统中,天线是一种重要的组成部分.它负责接收空间的射频能量,并有效地分配这些能量,将它们用于信号发射.现在,随着个人通信系统技术的迅猛发展,人们对作为基础设施的天线开始有所忽略.     

Experimental validation of fully-adaptive smart antenna prototype

The architecture of a fully-adaptive smart antenna working in the 2.4 GHz band is described and its functionalities preliminarily assessed. The radiating unity consists of an eight-element linear array of dipoles with a finite reflecting plane. The adaptive behaviour is achieved by means of a set of electronically-driven vector modulators that realise the array weights. The capability to react in real-time to complex interference scenarios is provided by an SW control module based on the particle swarm optimiser (PSO) algorithm. To assess the effectiveness of such an implementation, a selected set of results is reported and discussed.     

On the optimum number of beams for fixed beam smart antennas in UMTS FDD

Fixed-beam smart antennas are a simple but effective method to boost the downlink capacity of UMTS FDD. In this paper we compare the two possible strategies. Using a four element uniform linear antenna array, we find the optimum number of fixed beams per 120/spl deg/ sector dependent on the direction of departure (DoD) spread at the base station. For the first method we find the optimum number of beams to be four for low DoD spreads and two or three for large DoD spreads. For the second method the optimum number of beams per sector is seven for small DoD spreads and goes down to four or five beams per sector for large DoD spreads depending on base station spacing. By extensive system level simulations, we show, for 1 km inter base station distance, a capacity gain of more than 160% over a conventional 3-sectored reference system by both fixed beam methods.     

Time-triggered smart transducer networks

The time-triggered approach is a well-suited approach for building distributed hard real-time systems. Since many applications of transducer networks have real-time requirements, a time-triggered communication interface for smart transducers is desirable; however, such a time-triggered interface must still support features for monitoring, maintenance, plug-and-play, etc. The approach of the Object Management Group (OMG) Smart Transducer Interface consists of clusters of time-triggered smart transducer nodes that contain special interfaces supporting configuration, diagnostics, and maintenance, without affecting the deterministic real-time communication. This paper discusses the applicability of the time-triggered approach for smart transducer networks and presents a case study application of a time-triggered smart transducer network.     

Ergodic capacity and outage probability optimization for secondary user in cognitive radio networks under interference outage constraint

This paper considers a cognitive radio network where a secondary user (SU) coexists with a primary user (PU). The interference outage constraint is applied to protect the primary transmission. The power allocation problem to jointly maximize the ergodic capacity and minimize the outage probability of the SU, subject to the average transmit power constraint and the interference outage constraint, is studied. Suppose that the perfect knowledge of the instantaneous channel state information (CSI) of the interference link between the SU transmitter and the PU receiver is available at the SU, the optimal power allocation strategy is then proposed. Additionally, to manage more practical situations, we further assume only the interference link channel distribution is known and derive the corresponding optimal power allocation strategy. Extensive simulation results are given to verify the effectiveness of the proposed strategies. It is shown that the proposed strategies achieve high ergodic capacity and low outage probability simultaneously, whereas optimizing the ergodic capacity (or outage probability) only leads to much higher outage probability (or lower ergodic capacity). It is also shown that the SU performance is not degraded due to partial knowledge of the interference link CSI if tight transmit power constraint is applied.     

浅析智能天线在电磁环境监测中的应用

1 引言 随着信息技术的迅速发展,无线通信设备的种类和数量迅速增加,呈现出大功率、高频率、宽频段、智能化的用频特点,电磁环境变得日益复杂,频谱资源管理面临新的挑战。电磁环境监测是频谱资源管理的有效手段和必要基础。目前,我国已经形成了以固定监测站为主,可搬移监测站（含车载）、便携式监测设备为辅的无线电监测网体系。     

智能天线对TD-SCDMA系统中小区干扰分布的影响

本文通过对TD-SCDMA系统上行链路进行系统级仿真,输出了不同场景下相邻小区和本小区干扰比均值,以此对比分析了智能天线和定向天线对小区间和小区内干扰的抑制情况,并给出有关工程措施建议,为TD-SCDMA系统组网提供指导性意见.     

On the outage probability in single frequency networks for digitalbroadcasting

The new digital modulation schemes (OFDM) proposed for broadcasting of sound and television allow for the use of simulcasting, i.e., letting all transmitters in a radio network transmit on the same frequency. Such single-frequency networks (SFNs) have the potential of providing good coverage and very good frequency economy in wide-area (nationwide) applications. An OFDM-based SFN is analyzed with respect to its coverage properties. The network performance is measured by the outage probability and frequency economy. Both wide and local area systems are considered. Results show that in wide-area networks, very low outage probabilities may be achieved with very modest transmitter powers. The main reason for this is the inherent diversity, the efficiency is of which is primarily dependent on the transmitter density. However, in local area systems with only a few transmitters in each region, the performance is shown to drop drastically, mainly due to the low degree of diversity. This work implies that good network planning results in low-power, closely spaced transmitters     

基于EIRP最优的智能天线阵赋型算法研究

在实际天线阵列中,由于互耦的影响会使得单天线阵元辐射方向图畸变,导致传统的波束赋形算法性能恶化甚至失效。针对这个问题,文中提出了基于等效全向功率约束条件的粒子群算法,避免了传统的波束赋形算法的失效,提升了系统的等效全向功率。同时,为了减弱干扰方向的影响,文中进一步提出了零陷生成方案。仿真结果显示本文提出的算法不仅能够提升波束的等效全向功率,而且可以有效地生成干扰方向的零陷。     

UTRA TDD系统配置中的干扰分析

由于频谱资源的有限和非对称数字业务的增多,UTRA TDD网络受到了许多国家通信运营商的青睐。在无线网络规划和设计中,UTRA TDD系统要考虑各种现实情况,特别是干扰问题。文章主要分析了UTRA TDD在系统配置中不同情况下可能产生的TDD—TDD干扰和TDD—FDD串扰．并说明干扰产生的原因以及如何采取措施消除或减少干扰,以利于UTILA TDDN络的规划和优化。