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  • 单片机毕业设计

    对于本科生大专生高职生毕业设计很有帮助,51系列的

    2011-12-18
    1
  • 最新移动通信原理与技术英文版教程

    这是一部权威的英文版移动通信教程,内容讲解翔实全面,适合对英语和移动通信感兴趣的爱好者

    2011-03-05
    10
  • RFID重大工程与国家物联网

    目前最新的物联网信息技术教程,全面权威,适合对此有爱好的朋友,希望大家喜欢

    2011-03-05
    4
  • Potentials of smart antennas in CDMA systems and uplink improvements

    An overview of the application of smart antennas in DS-CDMA systems, including IS-95 and IS-2000, is presented. Since CDMA systems are interference-limited, adaptive antenna arrays have great potential for improving the performance of such systems in terms of capacity, coverage, and quality of service. In this paper, we study the multiple-access interference that affects a CDMA system, and we describe how smart antennas can be implemented in an IS-2000-based mobile communica- tions system. When smart antennas are used at the base station to transmit in narrow beams, the interference on the downlink is reduced, and Cjl is improved. This, in turn, increases the system capacity on the downlink or, alternatively, the quality of service is improved. Such gains will prove very beneficial for asymmetric high-speed data applications. requiring much higher bit rates on the downlink than on the uplink. By reducing the base-station receiver's sensitivity, smart antennas can boost the capacity of the reverse link. Results are presented that outline how this reduction can be employed by the system designer on the uplink to increase capacity, reduce the mobile transmit power, or effect a tradeoff between capacity improvement and coverage or range extension under different system-loading scenarios.

    2010-08-05
    3
  • Performance analysis of smart antenna test-bed operating in a wide-band CDMA channel

    Abstract—In this paper, we present a performance analysis of a smart antenna system operating in a wide-band CDMA wireless- local-loop channel using a beam-forming module (BFM) that has been implemented on a digital signal processor (TMS320C6701) board.We first show the results of computer simulations obtained from the modeled received (RX) signals through a test-bed system consisting solely of baseband signal processing parts, i.e., modeled RX data-generating PC, BFM for computing the optimal weight vector and interfacing module. A test-bed system of the entire base station is then implemented to evaluate the adaptive beam-forming function with the actual wireless signals. This test-bed system in- cludes several subscribers, as well as the array antenna, RF mod- ules, and other receiving parts required at the cell site.

    2010-08-05
    3
  • Adaptive antennas for mobile communications

    Adaptive-antenna techniques offer the possibility of increasing the performance of mobile radio communication systems by maximising directional gain and enhancing the protection towards multipath conditions. The net effect of these techniques is to improve immunity to interference, extend the range of each cell and thus increase the system capacity. This paper presents the results of a two year research programme aimed at the development of practical adaptive-antenna signal-processing structures. Specifically, results obtained from a series of analysis and field trial activities undertaken with an adaptive antenna test bed and based around the DECT cordless standard are presented.

    2010-08-05
    4
  • Vector channels for smart antennas. Measurements, statistical modeling, and directional properties in outdoor environments

    Abstract—In wireless communications, smart antenna systems that employ antenna arrays coupled with adaptive signal-pro- cessing techniques at the basestation improve capacity, coverage, and trunking efficiency.However, design and performance analysis of smart antenna systems strongly depend on channel propaga- tion characteristics of signals present at the antenna array, the so-called vector channels. Here, variation of narrow-band vector channels (spatial signatures) due to a moving terminal is studied in

    2010-08-05
    3
  • Adaptive joint detection of cochannel signals for TDMA handsets

    Abstract—In mobile communication systems, downlink (for- ward link) system capacity is limited by the ability of mobile receivers to recover the desired signal in the presence of cochannel interference (CCI). Joint detection of the desired and cochannel signals is a useful approach to improving receiver performance, thus increasing system capacity. In this paper, we show that a practical single-antenna joint-detection receiver can provide significant gains in system capacity for the time-division mul-

    2010-08-05
    3
  • Parameter Learning for Performance Adaptation

    A parameter learning method is introduced and used to broaden the region of operability of the adaptive control system of a flexible space antenna. The learning system guides the selection of control parameters in a process leading to optimal system performance. The method is applica- ble to any system where performance depends on a number of adjustable para- meters. A mathematical model is not necessary, as the learning system can be used whenever the performance can be measured via simulation or experiment.

    2010-08-05
    1
  • A Comparative Analysis of Spatial Multiplexing Techniques for Outdoor MIMO-OFDM Systems with a Limited Feedback Constraint

    Abstract—In this paper, we analyze spatial multiplexing tech- ques for the downlink of a multiple-input–multiple-output MIMO) orthogonal frequency-divisionmultiplexing (OFDM) sys- m. Our study is focused on outdoor environments characterized y a moderate angular spread. We consider two techniques that e able to separate the downlink data streams associated with fferent users and to guarantee a fixed error probability by ploiting limited feedback from each user. The grid of beams GoBs) and the proposed adaptive GoB (AGoB) differ in the ay the precoders are designed (by adaptive or fixed processing) nd in their scheduling policy. The new AGoB is able to harness artial knowledge of the downlink channel spatial structure to etter select the users and adjust their precoders for downlink ansmission. The performances of GoB and AGoB are compared

    2010-08-05
    1
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