Browsing by Author "Liao, CY"

Now showing 1 - 8 of 8

A novel dynamic cell configuration scheme in next-generation situation-aware CDMA networks
(2006-01-01)
Liao, CY
;
Yu, F
;
Leung, VCM
;
Chang, CJ
;
電信工程研究所
To balance the time-varying traffic load between cells, caused by user mobility and diverse applications, it is crucial for next-generation code-division multiple-access (CDMA) cellular networks to configure cell coverage and capacity dynamically. In this paper, we show that pilot power allocation is highly coupled to other facets of radio resource management. We propose a novel dynamic cell configuration scheme for multimedia CDMA cellular networks, based on 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.
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.
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.
Downlink soft handover and power allocation for CDMA heterogeneous cellular networks
(2002)
Wang, LC
;
Liao, CY
;
Chang, CJ
;
電信工程研究所
;
Institute of Communications Engineering
Handover in heterogeneous cellular networks is one of the hottest topics for the wireless networks beyond the third generation. This paper presents a new downlink soft handover algorithm to solve the serious "power exhausting" problem during the traditional handover process in heterogeneous cellular systems. The power exhausting problem occurs when in the traditional handover process, the serving base stations usually adopt the equal power allocation (EPA) strategy for different sizes of cells. Thus we propose a constrained unequal power allocation (CUPA) technique to serve handover users by taking account of the effects of different cell sizes and shadowing. Compared to the EPA method, our simulation results show that the proposed soft handover algorithm combining with the CUPA technique can improve total system capacity by 5% in a homogeneous cellular system, and 73% in a heterogeneous cellular system.
Performance study of soft handover with CDMA heterogeneous cellular architectures
(2002)
Wang, LC
;
Liao, CY
;
Chang, CJ
;
電信工程研究所
;
Institute of Communications Engineering
This paper investigates the downlink user capacity of a heterogeneous cellular CDMA system with soft handover. We consider the scenario that a hotspot microcell is adjacent to a larger macrocell instead of a microcell embedded within a macrocell. Since traditional soft hand-off algorithms are developed for homogeneous cell structures, the two serving base stations allocate equal power in the downlink to the soft handover users [1]. We observe that this kind of equal power allocation will cause a serious "power exhausting problem" in the microcell when soft handover is occurred between two cells with different cell radius. To quantize the impact of this problem, we present an analytic approximation method for computing the downlink user capacity with soft handover in heterogeneous cellular structures. We further propose an improved quality balancing power allocation method with maximum power constraint to enhance the downlink soft handover performance when two involving handover base stations have different cell sizes. The simulation results show that the improved power allocation for soft handover can support a larger range of the ratios of the cell radius between microcell to macrocell, thus increasing the total system capacity in the sense that more microcells can be installed adjacent to a macrocells. Our numerical results demonstrate that in a heterogeneous CDMA network with the cell radius ratio between microcell and macrocell equal to 0.3, the proposed constrained unequal power allocation (UPA) technique with soft handover can enhance the total system capacity eight times higher than the conventional equal power allocation (EPA) method.
Purification of human plasma haptoglobin using hemoglobin-affinity column chromatography
(2003-03-17)
Mao, SJT
;
Liao, CY
;
生物科技學系
;
Department of Biological Science and Technology
Reinforcement-learning-based self-organisation for cell configuration in multimedia mobile networks
(2005-09-01)
Liao, CY
;
Yu, F
;
Leung, VCM
;
Chang, CJ
;
電信工程研究所
In future wireless code division multiple access (WCDMA) cellular networks, random user mobility and time-varying multimedia traffic activity make the system design of coverage and capacity become a challenging issue. To utilise radio resource efficiently, it is crucial for cellular networks to have the capability of self organisation for cell configuration, which can configure service coverage and system capacity dynamically to balance traffic loads among cells by being aware of the system situation. This paper proposes a reinforcement-learning-based self-organisation scheme for cell configuration in multimedia mobile networks, which takes into account both pilot power allocation and call admission control mechanisms. Simulation results show that the proposed scheme improves system performance significantly compared to the conventional fixed pilot power allocation scheme and the scheme in which only pilot power is adjusted dynamically but the criterion of the call admission control is not coupled to it. Copyright (c) 2005 AEIT.
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.