Browsing by Author "Wu, Wu-Hsiu"

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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
;
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
;
Wu, Wu-Hsiu
;
Su, Yu T.
;
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.
Resource Allocation and Node Placement in Multi-Hop Heterogeneous Integrated-Access-and-Backhaul Networks
(2020-01-01)
Lai, Jiun Y.
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Wu, Wu-Hsiu
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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
We consider a heterogeneous MIMO-OFDMA based dense small cell (SC) system in which each macro cell base station (MBS) serves its coverage area with the help of small cell base stations (SBSs) through multi-hop wireless connections. The SBSs act as integrated access and backhaul (IAB) nodes that handle both access and backhaul traffics with wireless links. We first develop an optimal (sum-rate maximization) resource allocation (RA) algorithm which considers subcarriers/spatial subchannels assignment and the associated power allocations. We also present two low-complexity suboptimal RA schemes which, as verified by simulations, incur only minor performance loss in the high SNR region. Our RA algorithms can be applied to other multi-hop networks with general UE association rule and node location distributions. We study the channel aging effect caused by the time lag between the time channel state information (CSI) is measured and that when data transmission occurs. We show the benefit of channel prediction and the limit of a centralized RA approach. The advantages of frequency (channel) reuse and the multi-hop architecture are demonstrated as well. A related but perhaps more important system design issue for an IAB cellular network is the IAB node placement problem. With the given UE association rule and UE location distribution, we present systematic approaches to find the optimal node locations. For two special propagation models, we derive closed-form expressions for the node locations that maximizes a spectral efficiency lower bound. Numerical results validate the accuracy of our estimates based on either numerical evaluations or closed-form solutions.