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Access Interference (access + interference)

Distribution by Scientific Domains
Engineering100%

Kinds of Access Interference

  • multiple access interference
    		•

    Selected Abstracts

    Parallel interference cancellation in DS-CDMA optical networks using bias compensation

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2009
    A. Okassa-M'foubat
    A receiver based on the parallel cancellation of multiple access interference by bias compensation is considered here for a direct sequence unipolar optical code division multiple access (DS-OCDMA) system. It relies on the estimation of interferences from undesired users, the regeneration of interfering signals at the output of first canceller stage and their substraction from the received signal after amplification by a bias compensation factor in the second stage. The performance of such a technique is analysed in a synchronous network using orthogonal optical codes and the results are compared with those for different types of conventional receivers. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Frequency domain equalisation in CDMA detection

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 2 2008
    Ihan Martoyo
    The present paper introduces frequency domain equalisation (FDE) as an efficient means for single-user detection (SUD) in universal mobile telecommunication systems (UMTS) handhelds. Such an SUD is, at least partially, able to remove multiple access interference (MAI) like a multi-user detector (MUD), however with several important advantages the operation principle of an FDE-SUD is simple and easy to understand, the FDE-SUD shows low numerical complexity and therefore, it is not power hungry like an MUD. The problem of applying FDE without zero-padding or cyclic-prefix insertion is solved by using the overlap-cut method. In this paper we also prove that the performance of the FDE-SUD is practically identical to that of linear MUD for a fully loaded UMTS cell. Furthermore, armed with the idea of FDE for code division multiple access (CDMA), we can construct a common receiver structure for CDMA, time division multiple access (TDMA), orthogonal frequency division multiplexing (OFDM) and multi-carrier CDMA (MC-CDMA) systems. This is an extremely useful idea in enabling a software-defined radio (SDR) which can operate seamlessly in several environments such as UMTS, the IEEE 802.11a and WiMaX. FDE based receivers could be one important building-block for the next generation mobile communications. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Fuzzy-based multiuser detector for impulsive CDMA channel

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 7 2007
    Adel M. Hmidat
    A new fuzzy multiuser detector for non-Gaussian synchronous direct sequence code division multiple access (DS-CDMA) is proposed for jointly mitigating the effects of impulsive noise and multiple access interference (MAI). The proposed scheme combines a linear decorrelator and antenna array with a nonlinear preprocessor based on fuzzy logic and rank ordering. The fuzzy rule is incorporated to combat impulsive noise by eliminating outliers from the received signal. The performance of the proposed scheme is assessed by Monte Carlo simulations and the obtained results demonstrate that the proposed fuzzy detector outperforms other reported schemes in terms of bit error rate (BER) and channel capacity. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Asynchronous orthogonal decision-feedback multiuser detector (AODFD) and its alternative decoding strategies

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2001
    Hsiao-Hwa Chen
    Abstract This paper proposes a new CDMA multiuser detector, asynchronous orthogonal decision-feedback detector (AODFD), and its alternative decoding schemes. The proposed AODFD does not require an infinitely long whiten filter in its feed-forward stage, however, which is necessary in the traditional ADDFD detector reported in the literature. The updating algorithm of the AODFD detector is also much simplified if compared with that of ADDFD that requires computational intensive z -transformed matrix inversion and spectral factorization. Results show that, despite its low complexity, the AODFD performs very well under multiple access interference. The proposed two new decoding strategies can also be chosen to cater for different operating scenarios. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Design, implementation and verification through a real-time test-bed of a multi-rate CDMA adaptive interference mitigation receiver for satellite communication

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2003
    Luca Fanucci
    Abstract This paper presents the design, the implementation, and the main performance results of a multi-rate code division multiple access (CDMA) interference mitigation receiver for satellite communication. Such activity was performed within a research project supported by the European Space Agency (ESA), whose aim was to demonstrate the suitability of the linear adaptive interference mitigation detector (IMD) named extended complex-valued blind anchored interference-mitigating detector (EC-BAID) for single-user detection of a CDMA signal in third-generation (3G) satellite networks. Such a detector, which exhibits a remarkable robustness to multiple access interference, operates in a blind mode, i.e. it only requires knowledge of the timing of the wanted user's signature code, and is therefore very well suited for integration into handheld user terminals. Experimental results in terms of bit error rate with respect to the theoretical behaviour were derived through a specifically developed test bed. Signal plus multiple access interference generation is performed via a computer-controlled arbitrary waveform generator, followed by frequency up-conversion to the standard intermediate frequency of 70 MHz. Additive white Gaussian noise is then injected with the aid of a precision noise generator. The core of the test bed is a flexible digital receiver prototype featuring the EC-BAID detector plus all functions ancillary to IMD (multi-rate front-end, automatic gain control, code acquisition and tracking, carrier synchronization, etc.). Those functions were implemented through careful mixing of different technologies: field programmable gate arrays (FPGAs) for computing-intensive signal processing functions, digital signal processor (DSP) for housekeeping and monitoring, and application specific integrated circuit (ASIC) for adaptive IMD. The adopted design flow also allows an easy re-use of the prototype architecture to come to an overall integration of the receiver into a single ASIC with modest complexity and power consumption increase with respect to a conventional detector. Copyright © 2003 John Wiley & Sons, Ltd. [source]