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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Chang, CJSubject: search.filters.subject.CDMA

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Now showing 1 - 4 of 4
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    An accurate method for approximating the interference statistics of DS/CDMA cellular systems with power control over frequency-selective fading channels
    (2005-01-01)
    Lee, CH
    ;
    Chang, CJ
    ;
    交大名義發表
    ;
    National Chiao Tung University
    This letter proposes an approximation method by characteristic function (AM-CF) method to approximate the distribution of interference in DS/CDMA cellular systems. This method considers the effects of frequency-selective multipath fading; it also assumes perfect power control and a rectangular/sinc chip waveform. the AM-CF method can yield results that fit the Monte Carlo simulation results more accurately than the conventional standard Gaussian approximation method.
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    Tier-selection algorithms with multi-class traffic in CDMA hierarchical cellular systems
    (2003)
    Wang, LC
    ;
    Liao, CY
    ;
    Lin, YL
    ;
    Chang, CJ
    ;
    電信工程研究所
    In this paper, we investigate. several tier selection strategies in a hierarchical cellular system where a hotspot microcell service data users demanding high capacity, and a macrocell services low capacity voice users. A new "relative pilot based (RPB)" tier selection scheme is proposed to achieve the goals of balancing traffic load between a macrocell and a microcell, and reducing the interference between a macrocell and a microcell. The simulation results show that the RPB scheme improves both the blocking performance and outage performance with both data and voice users compared to traditional service based tier selection scheme.
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    A novel dynamic cell configuration scheme in next-generation situation-aware CDMA networks
    (2005)
    Liao, CY
    ;
    Yu, F
    ;
    Leung, VCM
    ;
    Chang, CJ
    ;
    電信工程研究所
    In next-generation CDMA networks, due to random user mobility and time-varying multimedia traffic activity, the system design of coverage and capacity is a challenging issue. To utilize radio resources efficiently, it is crucial for future cellular networks to be aware of the system situation and configures cell coverage and capacity dynamically to balance traffic loads over all cells. In this paper, we propose a novel dynamic cell configuration scheme in multimedia CDMA networks via reinforcement-learning, which takes into account pilot, soft handoff, and maximum link power allocations as well as call admission control mechanisms. Simulation results demonstrate the effectiveness of the proposed scheme in situation-aware CDMA networks.
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    Comparison of downlink power allocation mechanisms in soft handoff for the WCDMA system with heterogeneous cell structures
    (2005-09-01)
    Liao, CY
    ;
    Wang, LC
    ;
    Chang, CJ
    ;
    電信工程研究所
    ;
    Institute of Communications Engineering
    Handoff in heterogeneous cellular networks is one of the hot topics for wireless networks beyond the third generation. We observe that a power exhausting issue may occur in a code division multiple access (CDMA) system with mixed-sized cells. During soft handoff in the downlink transmission, a number of base stations transmit signals to a user simultaneously. Usually, a microcell has a more stringent limitation on the total available power than a macrocell. Thus, ignoring the impact of various cell sizes, the traditional downlink power allocation techniques for soft handoff may easily consume excessive power to serve soft handoff users, while leaving insufficient power for serving other regular users. To resolve such an power exhausting issue in CDMA systems, we investigate different downlink power allocation techniques used in soft handoff subject to the impact of mixed-sized cells. For the single-site power allocation technique we consider the site selection diversity transmission (SSDT) technique, while for the multi-site power allocation we study the link proportional power allocation (LPPA), the quality balancing power allocation (QBPA), and the equal power allocation (EPA) techniques. We find that the multi-site LPPA technique can more efficiently allocate power to both handoff and non-handoff users than others. In an example with the ratio of the micrcocell radius/macrocell radius equal to 1/3, it is demonstrated that LPPA can improve the capacity over EPA, QBPA, and SSDT by 125, 30, and 5%, respectively. By taking account of measurement errors in the same case, the capacity improvements of LPPA over EPA, QBPA, and SSDT become 180, 41, and 23%, respectively.