Home  About us  Contact
 

Diversity Gain (diversity + gain)

Distribution by Scientific Domains
Engineering100%

Kinds of Diversity Gain

  • effective diversity gain
    		•

    Selected Abstracts

    Exploiting the short,term and long,term channel properties in space and time: Eigenbeamforming concepts for the BS in WCDMA

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2001
    Christopher Brunner
    The deployment of adaptive antennas at base stations considerably increases the spectral efficiency of wireless communication systems. To reduce the computational complexity and increase performance of space,time (ST) processing, processing may take place in reduced dimension, i. e., pre,filtering takes place which is related to linear estimation theory based on second order statistics. To this end, long,term and short,term channel estimates are integrated into specific Tx/Rx systems. In this article, we present a new ST rake structure for uplink reception in WCDMA which operates in reduced dimension. Accordingly, our approach combines short,term and long,term spatial and temporal channel properties using an eigenanalysis. By choosing dominant eigenbeams in time and space, the algorithm enhances interference suppression as well as spatial and temporal receive diversity. In contrast to previously introduced well,known receiver structures, the ST eigenrake inherently adapts to different propagation environments and achieves higher spectral efficiency than other receivers. This is illustrated by Monte,Carlo simulations. Then we extend the proposed concept to the downlink. The downlink eigenbeamformer improves closed,loop downlink diversity compared to other proposals in standardization (3GPP) which only exploit short,term channel properties. Even though the short,term feedback rate remains unchanged, additional antenna elements can be included to increase antenna and diversity gain. We also present a tracking solution to the downlink eigenbeamforming in WCDMA. To this end, we propose a distributed implementation of the eigenspace/,beam tracking at the mobile terminal and base station (BS), respectively. Moreover, the specific nature of the deployed tracking scheme offers an advantageous feedback signalling. [source]

    A utility-based capacity optimization framework for achieving cooperative diversity in the hierarchical converged heterogeneous wireless networks

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 12 2008
    Mugen Peng
    Abstract A hierarchical convergence mechanism for the heterogeneous wireless communication system via the heterogeneous cooperative relay node is presented in this paper, in which the techniques of cooperative communication and wireless relay are utilized to improve performances of the individual user and the overall converged networks. In order to evaluate the benefits of the proposal, a utility-based capacity optimization framework for achieving the heterogeneous cooperative diversity gain is proposed. The heterogeneous cooperative capacity, relay selection and power allocation theoretical models are derived individually. The joint optimization model for relay selection and power allocation is presented as well. Owing to the computation complexity, the sub-optimal cooperative relay selection algorithm, the sub-optimal power allocation algorithm and the sub-optimal joint algorithm are determined to approach the maximum overall networks' spectrum efficiency. These proposed algorithms are designed in conformance to guarantee the equivalent transmission rates of the different wireless access networks. The simulation results demonstrate that the utility-based capacity model is available for the heterogeneous cooperative wireless communication system, and the proposed algorithms can improve performances by achieving the cooperative gain and taking full advantage of the cross-layer design. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Active measurements of antenna diversity performances using a specific test-bed, in several environments

    INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2010
    Moctar Mouhamadou
    Abstract The diversity performances of the wireless devices operating in a multipath propagation environment are usually presented in terms of correlation coefficient, diversity gain and effective diversity gain. These parameters can be measured in reverberation chamber. This paper presents some active measurements of antenna diversity performances on a small wireless terminal in several realistic environments. The measurements were performed in the WiMax band, i.e. at 3.5 GHz, in a reverberation chamber where the channel is statistically uniform, in a real indoor propagation channel, and in an outdoor-to-indoor environment. The diversity performances are evaluated by using a specific test-bed constituted by an arbitrary signal generator and two radio-frequency digitizers. The effectiveness of diversity is presented in terms of effective diversity gain, signal to noise ratio, bit error rate and frame error rate. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source]

    Fade correlation and diversity effects in satellite broadcasting to mobile users in S-band

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2008
    Albert Heuberger
    Abstract In this paper, we present measurement results for fade correlation in time and space of signals from two satellites in geostationary orbit with 30° separation. Fade data for urban, residential and rural environments are analyzed. In addition to fade cumulative distribution function, rice factor and coherence length of individual fade signals, also the joint probability density function and the cross-correlation for the fade from the two satellites are presented. The coherence length of single satellite fades extends to about 18,m in the urban area and is around 2,m in the rural area. The correlation coefficient of dual satellite fades is below 0.3 in the residential and rural area. In the urban area larger correlations around 0.7 occur. Based on the measured fade data the diversity gain for various network configurations are determined by simulation for a forward error correction scheme using concatenated codes in combination with random interleavers. Network configurations of interest are single-satellite space diversity, two-satellite space diversity, one-satellite time diversity and two-satellite space and time diversity. For short interleavers of 5,m the diversity gain is in the residential area of 2.3,dB for the two-satellite space diversity, 0.3,dB for one-satellite time diversity and 4.1,dB for two-satellite space and time diversity. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Short-scale diversity in a dynamic rain fade environment

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2005
    Cristina Enjamio
    Abstract This article is concerned with using time-varying uniformly spaced rainfall data to investigate the concept and values of instantaneous diversity gain. This has been obtained on a minute-by-minute basis in order to illustrate the behaviour of a VSAT communication system which switches to the most reliable link every minute. The simulations have been carried out using a whole year of rain data obtained from the recordings of a dense rain gauge network located in Barcelona. After illustrating the concept of instantaneous diversity gain, this paper shows the results obtained for various site separations and 20 GHz. These results have been plotted together with the values given by some long-term-based models. The comparison shows that such models are not appropriate for dynamic site diversity. This was found to increase the reliability of a VSAT system, especially under severe rain conditions in which the rainfall rates are spatially arranged in rain cells and the attenuation experienced by the two sites is strongly decorrelated. The correlation coefficient between the attenuation series calculated for several separation distances has also been obtained to illustrate this concept. Finally, the paper gives the attenuation distributions calculated for a VSAT system with and without site diversity and for several site separations. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Analyzing GPS signals to investigate path diversity effects of non-geostationary orbit satellite communication systems

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2002
    Hsin-Piao Lin
    Abstract The concept behind path diversity is that a user who can access several satellites simultaneously will be able to communicate more effectively than a user who could only access one. The success of this method depends on the environment, the satellite constellation, and diversity combining technology. This paper explores the path diversity effects of non-geostationary orbit (NGO) satellite personal communication services, for different degrees of user mobility, under various scenarios, using the constellation of the global positioning system (GPS). Measurements are taken near downtown Taipei. Three types of mobilities (fixed-point, pedestrian, and vehicular) are examined, and the switch diversity and maximum ratio combining method are applied to determine the path diversity gain and calculate bit error probability. The error probability performance of applying diversity schemes in coherent binary phase shift keying (BPSK) and non-coherent differential phase shift keying (DPSK) modulations over Rician fading channels are also analysed and evaluated by using the characteristic function method. The results show that fading can be significantly reduced and diversity greatly increased. A significant diversity gain and improvement in bit error rate (BER) can be expected in all cases by simply applying switch diversity scheme. Besides, for the maximum ratio combining method, the results imply that summing two satellite signals suffices to increase diversity and improve the bit error rate performance. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Shadowing correlation assessment and modeling for satellite diversity in urban environments

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2002
    M. Vazquez-Castro
    Abstract Non-geostationary orbit satellite networks have dynamic, yet deterministic topologies. This paper deals with the consequences of relying on the use of multiple visible satellites to improve availability with time/locations through satellite diversity techniques. The assumption of independent blockage events in two different satellite-to-mobile links is generally not accurate and information on shadowing correlation should be taken into account in the assessment of availability. In this paper a shadowing correlation study for urban environments is presented and a model for the real environments, as well as for a generic urban environment is inferred. The model proposed here is simple and can be run on a computer. It also relates urban and constellation geometries thus allowing the identification of those cases for which satellite diversity gain should be expected. As a result of this analysis and modelling, we present empirical analytical expressions describing positive correlation coefficient as a function of satellite angular separation (azimuth and elevation). We also show that an angle exists above which correlation can be negative and satellite diversity can sensibly improve link availability. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Active measurements of a mimo WiMAX-OFDM based system in reverberation chambers

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010
    Adil Belhouji
    Abstract Electromagnetic reverberation chambers can be used for multiple-input multiple-output (MIMO) systems testing.Currently, the tests focus on parameters such as correlation, diversity gain, efficiency, etc., by using a vector network analyzer. In contrast with these passive tests, a novel way of MIMO systems characterization is described in this article. It consists on evaluating bit error rate (BER) levels of a MIMO WiMAX-OFDM system according to the Signal-to-Noise Ratio (SNR) by establishing an active link between the transmitter and the receiver. The measurement process is set up in a reverberation chamber, where multipath frequency selective channels are emulated. The obtained results are compared to a reference case with single-input single-output (SISO) to evaluate the real improvements made by the studied system. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2347,2352, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25465 [source]

    Definition of effective diversity gain and how to measure it in a reverberation chamber

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2002
    Per-Simon Kildal
    Abstract The performance of cellular phones and other mobile or wireless terminals operating in multipath propagation environment can be greatly improved by introducing different diversity schemes. The improvement is characterized in terms of a diversity gain. An effective diversity gain is defined here. This is an absolute measure of diversity gain and can therefore be used to compare different diversity antennas. The Letter also shows how the effective diversity gain can be measured in a reverberation chamber. Measured effective diversity gains agree much better with theoretical diversity gains than measured values published previously. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 56,59, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10372 [source]