Browsing by Author "Ho, Chieh Yuan"

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Analysis of Delay-Energy Tradeoff and Energy Minimization Schemes for Group-based Machine-to-Machine Communications in OFMDA Cellular Networks
(2012-01-01)
Ho, Chieh Yuan
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Huang, Ching-Yao
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Machine-to-Machine (M2M) communication has recently become a hot topic in 4G Standardization Committee, such as IEEE 802.16p and LTE-A. In an OFDMA cellular network embedded with a M2M system, we characterize system energy consumption (EC) and average delay for the M2M system and propose energy-efficient Machine Node (MN) access control schemes, jointly implementing MN grouping and coordinator selection, under a 2-hop transmission framework to minimize system EC with limited resource amount assigned by BS while satisfying the system delay requirement. In the simulation results, the tradeoff between EC and delay is investigated with respect to given resource amount, and the relationship between number of coordinators and total energy consumption is studied. Furthermore, the proposed schemes need relatively less coordinators to achieve very low EC, and can achieve near-optimal EC with any delay requirement.
Capacity-based compressed mode control method for inter-system handover in universal mobile telecommunication system
(2007-11-08)
Huang, Ching Yao
;
Chang, Cheng Ta
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Ho, Chieh Yuan
The Inter-System handover is one of the key features in the third generation cellular systems. The compressed mode, with variable transmission gaps and power levels, is standardized to support the inter-frequency system handover. To minimize the use of system resources while maintaining the border-cell handover quality, a capacity-based compressed mode control method of the present invention is proposed. Considering the tradeoff between the capacity and the communication quality, the control method can adaptively manage the compressed mode operation based on the potential impacts on the capacity and the effectiveness of the compressed mode measurement. The present invention will improve the effectiveness and performance of the compressed mode operation.
Energy Efficient Subcarrier-Power Allocation and Relay Selection Scheme for OFDMA-based Cooperative Relay Networks
(2011)
Ho, Chieh Yuan
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Huang, Ching-Yao
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電機工程學系
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Department of Electrical and Computer Engineering
uplink energy-efficient communication is an important issue due to the limited battery power for Mobile Stations (MSs). In this paper, the average 'Bits-per-Joule' is defined as the energy efficiency metric, and the optimal joint power allocation for both MS and RS is derived for maximizing MS' energy efficiency. Based on that, we developed a low-complexity subcarrier-power allocation and relay selection scheme for maximizing energy efficiency per user in an OFDMA cooperative relay network, assuming full channel state information (CSI) is available at both relay and BS nodes. The numerical result demonstrates that the energy efficiency performance of cooperative relay networks can be better in the range of 15% to 30% as compared to that of single BS networks. It also shows our proposed scheme has significant improvement on the energy efficiency performance as compared with conventional max-throughput and fairness-based Equal-Power Allocation (EPA) schemes which allocate equal transmit power to the assigned subcarriers. Furthermore, the proposed scheme can achieve similar performance in much lower computational complexity as compared with the exhaustive search scheme.
Energy-Efficient 2-D Resource Allocation with Fairness Constraints for OFDMA Networks
(2011)
Ho, Chieh Yuan
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Huang, Ching-Yao
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, a 2-Dimension (2-D) resource allocation problem for energy efficiency maximization in the uplink of an OFDMA network is studied. Firstly, with the metric of energy efficiency, measured as bits-per-joule, we convert the complex problem of optimizing the system energy efficiency, defined as sum of users' bits-per-joule, into an optimal achievable rate comparison problem, and devise a low-complexity sub-optimal resource allocation scheme for maximizing it while satisfying each user's resource requirement. The proposed scheme implements both power allocation and Resource Unit (RU) assignment devised by exploiting the optimal achievable rate maximizing user's energy efficiency. The numerical result shows that the proposed scheme outperforms widely-used schemes with Equal Power Allocation (EPA), such as maximum SNR and Proportional Fair, in terms of performance of bits-per-joule with different resource requirement and can achieve similar results as the exhaustive search scheme in much lower complexity.
Energy-Saving Massive Access Control and Resource Allocation Schemes for M2M Communications in OFDMA Cellular Networks
(2012-06)
Ho, Chieh Yuan
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Huang, Ching-Yao
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Machine-to-Machine communication recently becomes a popular issue in 4G Standardization Committee, such as IEEE 802.16p and LTE-A. In an OFDMA cellular network embedded with a M2M system, the energy consumption (EC) minimization problem is formulated with the consideration of transmission and circuit energy consumed. We propose joint massive access control and resource allocation (RA) schemes, which perform machine node grouping, coordinator selection, and coordinator RA, and also determine the proper number of groups under a 2-hop transmission protocol, to minimize total EC in both flat- and frequency-selective fading channel. Numerical results show that proposed schemes can achieve sub-optimal EC.
Non-Cooperative Multi-Cell Resource Allocation and Modulation Adaptation for Maximizing Energy Efficiency in Uplink OFDMA Cellular Networks
(2012-10)
Ho, Chieh Yuan
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Huang, Ching-Yao
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電機學院
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College of Electrical and Computer Engineering
We address the optimization problem of maximizing uplink energy efficiency, defined as sum of users bits-per-joule (bpj), in a multi-cell multi-user OFDMA network. Firstly, we propose a non-cooperative distributed scheme, in which mobile stations (MS) in different cells with given subcarrier assignment (SA) adjust the modulation and transmit power non-cooperatively, to optimize its own bpj. An advanced noncooperative BS-controlled resource allocation scheme, in which the base station in each cell jointly performs SA, modulation adaptation, and power control for MSs in a non-cooperative manner, is proposed. Numerical results illustrate the tradeoff between energy and spectral efficiency, and show the proposed scheme makes great improvement on bpj with marginal loss of throughput as compared to other conventional scheme.
Single- and multi- user uplink energy-efficient resource allocation algorithms with users' power and minimum rate constraint in OFDMA cellular networks
(2013-07-01)
Ho, Chieh Yuan
;
Huang, Ching-Yao
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, single- and multi- user Resource Allocation (RA) optimization problems considering transmit power and minimum rate constraint of Mobile Station (MS) for maximizing MS' energy efficiency, measured as bits-per-joule (bpj), are addressed. Assume channel state information of all MSs is known by base station. We propose uplink RA algorithms, performing subcarrier assignment and power allocation, for optimizing bpj of MS in a single-cell OFDMA-based cellular network for both single- and multi- user scenarios. In the single-user case, we propose RA algorithms, which utilize the closed-form solution derived by applying Lambert-W function and an iterative approach based on Karush-Kuhn-Tucker conditions respectively to achieve optimal bpj of MS. In the multi-user case, centralized iterative multi-user RA algorithms for maximizing sum of MS' bpj, performing joint subcarrier assignment and power allocation iteratively, are proposed by utilizing the proposed single-user RA schemes. In particular, tradeoffs between energy efficiency and spectral efficiency are fully investigated, and the influence of MS' power and minimum rate constraints on bpj performance is also studied. The effectiveness of proposed algorithms is presented by numerical experiments. Numerical results demonstrate the proposed algorithms can enhance bpj significantly with limited loss of total throughput compared to the sum-rate maximization algorithm (in Moretti et al., IEEE Trans Veh Technol 60(4):1788-1798, 2011).