On the analysis of switched-beam antennas for the W-CDMA downlink

Smart antennas are widely recognized as an enabling technology for addressing the demand of future wireless network capacity when employed in place of traditional fixed-coverage sector antennas. Furthermore, switched-beam antenna systems offer a robust implementation against multipath propagation effects and reduced complexity that is inherent with fully adaptive implementations. This paper introduces a simple closed-form expression for evaluating the capacity increase of W-CDMA cellular networks employing switched-beam antennas. The expression incorporates the effect of practical antenna patterns and the impact of multipath scattering on code orthogonality, as well as that of pilot signal power. The results show that a reduction in downlink interference of approximately 6 dB can be achieved by installing an eight-beam antenna system in a 120/spl deg/ sector configuration when representative values of these parameters are taken into account.     

Orthogonal switched beams for downlink diversity transmission

A downlink transmission scheme in a switched-beam antenna system for providing diversity and beamforming simultaneously based on the space-time block coding technique is proposed. The scheme involves selecting multiple beams based on the uplink reception of the switched-beam antenna system, and determining multiple orthogonal beams from the selected beams. With the orthogonal transmit beams, the proposed switched-beam antenna system outperforms conventional switched-beam systems and approaches the optimal performance achievable by a much complex adaptive antenna system.     

智能天线跟踪波束与切换波束的比较

首先从波束形成或控制的角度界定了2类智能天线—跟踪波束智能天线(以下简称跟踪波束系统)和切换波束智能天线(以下简称切换波束系统)。其次分别介绍了其中关键部分:跟踪波束系统的自适应方法和切换波束系统的波束选择方法的设计考虑。跟踪波束系统的自适应方法是利用基于Lagrange公式的自适应算法跟踪最强信号源,而切换波束系统的波束选择方法则是基于正确波束接收的信号必然比任何其他波束接收的信号强这个事实。最后,依据其性能和所需的复杂度对跟踪波束系统和切换波束系统作了比较。     

Performance of switched-beam smart antennas for cellular radiosystems

The performance and feasibility of switched-beam smart antennas for cellular radio systems is investigated. Switched-beam smart antenna systems are shown to either increase the capacity or extend the radio coverage by increasing the carrier-to-interference ratio (CIR). The trunking efficiency degradation caused by narrow-beam sectoring can be recovered or even improved by using a variety of trunkpool techniques. One drawback of switched-beam smart antennas is that the improvement in reverse-channel performance is not uniform over the entire cell area, and this presents a limiting factor on the achievable gains, practical considerations such as power control and the limited deployment of smart antenna cells are also addressed     

Reduced sidelobe four-beam antenna array fed by modified Butler matrix

A novel four-beam antenna array fed by a modified 4/spl times/8 Butler matrix is proposed. Four 180/spl deg/ directional couplers in conjunction with a 4/spl times/4 Butler matrix are applied to provide a tapered excitation of a linear eight-element switched-beam antenna array. Sidelobes as low as -20 dB for all four beams have been both theoretically and experimentally achieved. A proposed technique of antenna element rotation simplifies the design of a feeding network.     

On the design of switched-beam wideband base stations

A switch beam base-station antenna is presented. The antenna is an improvement on the Butler matrix. The input ports of the antenna are excited with equal or unequal amplitudes. The feed network is analyzed and presented in a simple manner. The antenna comprises the main part of a base station, and is useful for broadband communications. The architecture of the base station is described, and the services that can be provided are given. Finally, comments are made about the tradeoffs and benefits of the antenna in comparison to the classical Butler-matrix switched-beam and adaptive arrays.     

Switched-beam antenna based on modified Butler matrix with low sidelobe level

A switched-beam antenna with a low sidelobe level based on a modified n/spl times/n Butler feeding network is proposed. This novel design only requires addition of 180/spl deg/ power dividers in the Butler matrix part. A four-beam prototype is constructed. Measurement indicates that the sidelobe level is significantly reduced.     

Compact Switched-Beam Antenna Employing a Four-Element Slot Antenna Array for Digital Home Applications

In this paper a compact switched-beam antenna is proposed. The antenna is composed of a four-element antenna array based on L-shaped quarter-wavelength slot antenna elements. Such an antenna element is a planar structure and presents a directional radiation pattern in the azimuth plane. Its maximum radiation direction is toward near the direction of the open end of the slot. As a result, the open ends of the four slot antennas are arranged toward $0, pi/2, pi$, and $3pi/2$ , respectively. The statuses of these antennas are controlled by some diodes. Consequently, by carefully controlling the diodes, an antenna with several switchable patterns can be achieved. To prove the concept, a 2.4–2.5 GHz switched-beam antenna for WLAN applications is designed and implemented. Its size is 52 mm in square. The antenna possesses eight directional patterns and many nearly omnidirectional patterns in the azimuth plane. The experiment results fully demonstrate the performance of the proposed design. The envelope correlations and the characteristics of the designed antenna are also discussed. Due to the compact size and low manufacture cost, such a design can be a promising solution for digital home applications to overcome multipath problems and increase the transmission data rate.      

平坦衰落环境中多输入多输出系统衰落相关与信道容量研究

为分析模型物理参数和天线排列方式对多输入多输出系统信道容量的影响,提出了一种平坦衰落环境中信道容量的研究方法。该方法基于接收均匀圆阵和均匀线阵分别构建了蕴含模型物理参数的相关矩阵,并利用Wishart分布的性质推导了信道容量上下限。该方法回避了求取衰落相关矩阵特征值的概率密度函数,降低了运算量;可被推广到多天线-频分复用系统。仿真结果表明,天线间距较小时,采用均匀圆阵比均匀线阵的系统信道容量要高;天线间距增大到一定程度后,系统信道容量达到饱和。散射角越大,信道容量的增长速率越快且采用均匀线阵比均匀圆阵系统的信道容量高。接收信噪比较大时,平均信道容量上下限基本接近其实际值。     

A beam-forming network for a circular switched-beam phased arrayantenna

This paper reports on the design and development of a dividing/phasing network for a compact switched-beam array antenna for land-vehicle mobile satellite communications. The device is formed by a switched radial divider/combiner and 1-bit phase shifters and generates a sufficient number of beams for the proper satellite tracking     

Switched-beam single patch antenna

A simple and compact switched-beam antenna is presented. The radiation patterns of the antenna were predicted using the finite difference time domain method. Measurement was performed, and the results show good agreement with predictions. Low correlation can be expected from this antenna for diversity reception     

Single-anchor indoor localization using a switched-beam antenna

We propose an RF-based localization system that works using a single anchor node. The anchor is equipped with a switched-beam directional antenna that is installed on the ceiling of a room and collects signal strength information sufficient for absolute 2D target positioning. Indoor measurements are used to show satisfactory localization results with range-free (proximity), range-based and fingerprinting schemes.     

Four-sector cross-shaped urban microcellular systems withintelligent switched-beam antennas

A four-sector cross-shaped urban microcellular system with intelligent switched-beam antennas is proposed. Each sector covers a street block with a base station located at an intersection, and an intelligent beam-switching scheme is used to locate mobile users in the most suitable beam coverage. Due to directional narrow-beam patterns and waveguide effects of tall buildings, radio signals along vertical and horizontal streets do not interfere with each other. Therefore, a channel can be reused simultaneously in multiple neighboring cells as long as cochannels do not encounter each other along the line of sight. The proposed scheme has a channel reuse efficiency of 0.95 for a traffic load of 0.02 [new-call arrivals/s/cell]. The system also increases system capacity more than three times with a blocking probability of 1% and considerably reduces handoff traffic when compared with a conventional cross-shaped microcellular system with an omnidirectional beam pattern     

Adaptativité de charges utiles pour satellites multifaisceaux par reconfiguration de couverture

This paper presents a set of algorithms aiming at the reconfiguration of a multibeam satellite coverage by control of the beam forming networks. Two kinds of algorithm are studied : one for the satellite gain management and the other for channels to beam allocation. The reconfigurable system is compared to a fixed coverage one using a switching matrix for the allocation of satellite channels to beams. It is shown that for short time communications (typically 100 ms) the reconfigurable system, offers, with the same antenna size, a dramatic increase in terms of the number of potential customers while maintaining a service quality comparable to that offered by the fixed coverage system using a switching matrix for the allocation of satellite channels to beams. The service quality is described here by two parameters : waiting time and blocking probability. However for communications with longer duration (typically several minutes) the degradation is unbearable.     

几种多天线系统的信道容量比较

分布式天线、智能天线和扇区天线是三种能大大提高无线通信系统容量的技术,本文比较了这三种多天线系统的信道(Shannon)容量.假设每个用户在所有接收天线上的总功率相等,分析表明分布式天线和扇区天线的信道容量远大于智能天线的信道容量,而传统的观点认为智能天线在抑制干扰时要比扇区天线的性能更好,从而获得更大的系统容量.另外我们分析了分布式天线在渐近条件下的信道容量,即用户数K和载波数M都趋近无穷大,而保证α=K/M一定.分析表明在α较大时,分布式天线与比扇区天线的信道容量差趋近常数0.44比特/秒/维,但是如果考虑分布式天线的分集增益,那么分布式天线的信道容量要远大于扇区天线.     

走向智能化的第三代移动通信系统

第三代移动通信系统最重要的技术特征是智能移动通信技术,即系统的各功能模块的智能处理单元来实现,这些单元包括智能天线、智能传输、智能接收、智能业务接入和智能网络管理,智能天线的研究最有物色的是适合于ＣＤＭＡ的智能天线技术,智能传输主要涉及延寿适应调制、综合功率控制等;在智能接民中使用中国科技大学提出的最小均方误差简化方法（Ｓ－ＭＭＳＥ）检测的用户数经常规方法的用户数增加约一半,有很好的应用可能;智能     

A New, Low-Cost, Switched Beam and Fully Adaptive Antenna Array for 2.4 GHz ISM Applications

A new, low-cost, switched-beam and fully adaptive antenna array suitable for 2.4 GHz ISM applications is proposed in this paper. The array comprises of four elements, equal in number receiving RF and IF components, as well as a microcontroller based unit which is responsible for the control of the array. The array is designed with the aid of a custom genetic algorithm, while measurements results are presented indicating consistency between design and implementation. In addition, multipath fading mitigation capability of the array is demonstrated via channel measurements results.     

3×3多天线系统衰落相关与信道容量研究

为分析天线间距和散射角等信道物理参数对多输入多输出系统信道容量的影响,提出了一种相关衰落环境中信道容量的分析方法。该方法基于接收均匀圆阵构建了蕴含信道物理参数的衰落相关矩阵。并由此详细推导了3×3多天线系统信道容量的闭式表达。结果表明,相关矩阵特征值的个数和大小决定了系统信道容量的大小。该方法回避了已有算法需求取相关衰落信道特征值概率密度函数的问题,降低了运算量,可以被推广到任意收发天线数的多输入多输出和多输入多输出-频分复用系统。仿真结果表明,天线间距增大,信道容量随之增大。但是当天线间距增大到衰落相关的第一个过零点时,信道容量达到最大值,再增大天线间距对信道容量影响很小。散射角越大,信道容量收敛到最大值速率越快。     

Joint pre-processing co-channel interference cancellation for single user MIMO

In general, multiplexing and diversity gains of single user MIMO systems are restricted by min(M,N) where M, N denote the number of antenna elements at a transmitter and receiver, respectively. In order to increase the multiplexing/diversity gains and improve the performance of single user MIMO systems, a joint pre-processing co-channel interference cancellation (JPCIC) method is proposed. The JPCIC is analyzed in both the perfect and the imperfect channel state information. The dependence of channel capacity on the number of antenna elements in every subset, the number of subsets, transmit powers and channel estimation errors is discussed. As theoretical calculation result, the channel capacity increases when the multiplexing/diversity gains and/or the transmit power increase in a certain channel model whether the channel estimation error is absent or present. Compared to the conventional zero-forcing method, the channel capacity of JPCIC is considerably higher because of higher multiplexing/diversity gains, however, it is less robust and decreased more rapidly due to incomplete cancellation of interference terms when the channel estimation error increases. There is a trade-off between the channel capacity and the complexity of system, however, according to quick development in circuit techniques and miniaturization of devices, the JPCIC is expected to be an attractive technology for MIMO system.     

Capacity Comparison of CDMA and TDMA in Vector Broadcast Channel

1　Introduction　MultipleInputMultipleOutput (MIMO)havereceivedagreatdealofattentionasamethodtoachievelargecapacityandhighreliabilityoverwire lesslink .Accordingtovectorbroadcastchannel,thebasestationanduserinthissystembothhavemulti pleantennas.Costa[1 ] hadpointedoutthatifthein terferencesignalwasindependentoftransmitsignalanditwasknownatthetransmitterthenthechan nelcapacitywiththeinterferenceisthesameasiftheinterferencewasnotexist.　Thoughthepreconditionofcosta sresultisscalarchannel.The…