Browsing by Author "Lin, Yuan-Bin"

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An iterative resource allocation algorithm for cooperative multimedia communications
(2007)
Lin, Yuan-Bin
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Chiu, Tai-Hsiang
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Su, Yu T.
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Kao, M. S.
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電信工程研究所
Transmit diversity through user cooperation is an attractive proposal for performance enhancement in a mobile communication network. Given the availability of multiple transmission channels from multiple users, we are concerned with the channel, power and rate assignment scheme that offers the maximum capacity while satisfying the multimedia multi-rate requirements. Earlier cooperative schemes often assume that a central processing device is available to find the optimal or suboptimal solution. The corresponding high computing complexity, however, makes the implementation of an energy-efficient cooperative transmission not very practical. In this paper, we present a simple resource allocation scheme that enables each participant user to easily and independently find a near-optimal channel assignment matrix and power allocation vector. under certain constraints. Our solution can be used for both mono-rate and multi-rate applications. It is optimal for the former case and gives near-optimal performance for the latter case.
Dynamic Resource Allocation for Relay-based OFDMA Systems With Fairness Considerations
(2010)
Lu, Yen-Shuo
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Lin, Yuan-Bin
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Su, Yu T.
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電信工程研究所
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Institute of Communications Engineering
Capacity and coverage of a Frequency Division Multiple Access (OFDMA) network can be greatly enhanced by dynamically allocate the radio transmission resources. By including the radio resources of cooperative nodes and taking into account the fairness issue, we present a simple suboptimal solution to the problem of radio resource allocation in relay-based OFDMA cellular systems. We restrict our investigation to a single-cell system with several cooperative relay stations and mobile stations (MSs). An IEEE 802.16e-like TDD scenario is assumed and only the uplink transmission with the base station (BS) handling the resource allocation is of concern. We propose two suboptimal algorithms that assign power, subcarriers and cooperative relay stations to a group of MS's to meet their QoS and minimum rate requirements. Our low-complexity solutions maximize the sum rate and a fairness index while satisfies the QoS and total transmit power constraint. Numerical results show that the proposed algorithms provide robust fairness and achieve near optimal sum rate performance.
Optimal and Near-Optimal Resource Allocation Algorithms for OFDMA Networks
(2009-08-01)
Lin, Yuan-Bin
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Chiu, Tai-Hsiang
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Su, Yu T.
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電信工程研究所
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Institute of Communications Engineering
Given the availability of multiple orthogonal channels and multimedia transmission rate requirements from multiple wireless OFDMA users, we are interested in a joint channel, power and rate assignment scheme that satisfies the given requirements with the minimum total transmit power. Algorithms for finding suboptimal and optimal solutions to sum power minimization resource allocation problems in OFDMA-based networks haven been proposed. But the complexity of finding the optimal solution is prohibitively high. We present two efficient algorithms with which each channel (sub-carrier) is assigned to at most one user. The first approach, which gives near-optimal solutions, employs a dynamic programming (DP) based tree search and adopts a fair initial condition that offers every user all available channels and removes a channel from all but one user at each stage. Each removal is based on the criterion of the least total power increase. Using the DP-based solution as the initial upper bound and the partial path cost used in the DP approach as the lower bound for each visited node, we develop an efficient branch-and-bound based algorithm that guaranteed to lead to the optimal solution. The average complexities of both algorithms are evaluated and effective schemes to further reduce the required complexity are proposed. We also provide performance and complexity comparisons with other suboptimal algorithms that are modified from the existing ones.
Optimal and Suboptimal Power Allocations for MIMO based Multi-Hop OFDM Systems
(2012)
Lin, Yuan-Bin
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Wu, Wu-Hsiu
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Su, Yu T.
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傳播研究所
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Institute of Communication Studies
We consider the problem of power allocation for capacity maximization in a decode-and-forward (DF) based multi-Hop MIMO-OFDM systems. We derive the necessary conditions for the optimal solution and propose an optimal power allocation algorithm for a 3-hop system, which can be easily extended to arbitrary number of relays. A suboptimal power allocation algorithm for a 3-hop system is also proposed. The suboptimal solution assumes equal power allocation over frequency domain and uses closed-form expressions for optimal power distribution over all hops for each subcarrier. Simulation results verify that, given the same transmit power, edge users are better served by a multi-hop relay scheme than by direct-link based scheme. Moreover, the proposed suboptimal power allocation yields an excellent sum rate performance which is close to the optimal performance.
Optimal and Suboptimal Resource Allocations for Multi-Hop MIMO-OFDMA Networks
(2012)
Lin, Yuan-Bin
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Wu, Wu-Hsiu
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Su, Yu T.
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傳播研究所
;
Institute of Communication Studies
This paper considers the problem of resource allocation for weighted sum rate maximization in a decode-and-forward (DF) based multi-hop MIMO-OFDMA systems. The optimal solution of joint subcarrier assignment (user and relay selections) and power allocation is obtained by solving a dual problem. We derive the necessary conditions for the optimal power allocation and propose a suboptimal algorithm with a closed-form based general power allocation solution. This suboptimal algorithm, as numerical results verify that, suffers from minor performance loss against that achievable by the optimal solution when SNR is high. It is observed that the corresponding closed-form power allocation yields 8% performance gain when compared with the equal power allocation.
Performance Analysis of a Complex Multicode Tracking Loop in Bandlimited Rayleigh Fading Channels
(2011-08-01)
Hsu, Nicolas Y. -H.
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Su, Yu T.
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Lin, Yuan-Bin
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電子工程學系及電子研究所
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電信工程研究所
This paper presents the root-mean-squared tracking error performance analysis of a class of coherent digital delay-locked loops for multicode direct sequence spread spectrum signals in bandlimited correlated Rayleigh fading channels. In the transmit side, multiple independent PSK-modulated data streams in the in-phase and qudrature phase branches are spread by short mutually orthogonal codes before being further complex spread by a long complex PN code. We assume that the system employs a pilot code channel to assist the receiver's synchronization and channel estimation. The proposed code tracking loop incorporates the pilot-aided channel estimator and derives the timing error from all short-code-spread subchannels. Our analysis takes into account the effects of imperfect channel estimate, correlated frequency selective Rayleigh fading and band-limiting. Numerical results are presented to quantify the impact of the resulting multipath interference within the same code channel and amongst different code channels.
Resource Allocation and Relay Selection for Cooperative OFDMA Networks With Imperfect Channel Information
(2011)
Wang, Jiun-Hung
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Lin, Yuan-Bin
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Su, Yu T.
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傳播研究所
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Institute of Communication Studies
We consider the problem of resource allocation and relay selection in an Orthogonal Frequency Division Multiple Access (OFDMA) based downlink network. We assume the availability of multiple cooperative relay stations but not the perfect channel state information (CSI). Instead, the base station knows only the estimated channel gain and the associated error distribution. Using a tight capacity lower bound (CLB) as the performance metric, we derive the optimal source and relay power allocation ratio that maximizes the CLB of a cascaded source-relay-destination link. Based on this power ratio, we propose a simple suboptimal algorithm that assigns power, subcarriers and cooperative relays to each mobile station. Simulation results show that our algorithm not only meets the users' rate constraints with very high probabilities but yields an excellent sum rate (CLB) performance.
Resource Allocation for MIMO-OFDMA Based Wireless Networks
(2010)
Weng, Chih-Lun
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Lin, Yuan-Bin
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Su, Yu T.
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電信工程研究所
;
Institute of Communications Engineering
The Multiple-Input Multiple-Output based Orthogonal Frequency-Division Multiple Access (MIMO-OFDMA) is a promising high rate air interface technology. It is well known that the capacity and coverage of such a system can be significantly enhanced by employing a proper resource allocation (RA) scheme. In this paper, a SVD based precoder and two corresponding adaptive RA algorithms for MIMO-OFDMA networks are proposed. The proposed centralized algorithms are designed to minimize the total required power while meeting each user's transmission rate and bit error rate requirements. Numerical results show that, for modest rate requirements, the proposed algorithms offer performance gain much larger than that of the existing RA algorithms.
Resource Allocations for MISO Based Cognitive Radio OFDMA Systems
(2012)
Lin, Yuan-Bin
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Su, Yu T.
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電機工程學系
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Department of Electrical and Computer Engineering
We propose an optimal and a suboptimal resource allocation algorithms for sum rate maximization in an MISO-OFDMA based cognitive radio network subject to a primary user outage constraint. By converting the outage constraint into user and subcarrier dependent peak power constraints, we obtain the optimal joint subcarrier assignment and power allocation solution by applying Lagrange dual-decomposition method. We also propose a low-complexity, fast-convergent suboptimal algorithm which uses an opportunistic channel gain-to-noise ratio based subcarrier assignment and an efficient constrained power allocation scheme. The optimality of the latter power allocation scheme is verified as well. Numerical results demonstrate that, compared with the optimal solution, the suboptimal scheme suffers only minor performance loss. We also shown that the use of more transmit antennas by a cognitive base station not only yields better spectrum efficiency but also lessens the outage-induced peak power constraint.