Browsing by Author "Chiu, Hsin-Li"

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Cooperative ARQ for Distributed Space-Time Coding: the Diversity-Multiplexing-Delay Tradeoff
(2008)
Chiu, Hsin-Li
;
Wu, Sau-Hsuan
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電信工程研究所
;
Institute of Communications Engineering
The throughput and the tradeoff between the diversity, multiplexing and the delay constraint of cooperative automatic retransmission request (ARQ) are investigated for distributed space-time coding (DSTC). According to the analysis, the maximum operational throughput turns out to be a piecewise linear curve with respect to the signal to noise ratio in decibel. In addition. the multiplexing gain divided by the average transmission times, referred to as the effective multiplexing gain, appears to be a better performance measure for delay-limited cooperative ARQ schemes. The tradeoff between the diversity and effective multiplexing gains is characterized for cooperative ARQ using DSTC in slow and fast fading channels, respectively.
Cooperative ARQs with Opportunistic Distributed Space-Time Coding: Effective Protocols and Performance Analysis
(2010)
Chiu, Hsin-Li
;
Wu, Sau-Hsuan
;
Li, Jin-Hao
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傳播研究所
;
Institute of Communication Studies
The paper studies effective protocols and corresponding performance of automatic retransmission request (ARQ) via decode-and-forward (DF) opportunistic distributed space-time coding (ODSTC). Analysis shows that the diversity via ARQ can be drastically increased by allowing non-active relays to overhear the DSTC signal sent by the active relays. Nevertheless, simple schemes without overhearing may also achieve the same diversity when the link quality between the source-relay or the relay-destination is good, hence greatly alleviating the need for a complex protocol with overhearing. Moreover, using more relays opportunistically does provide a higher coding gain if the source-relay channel quality is extremely good, otherwise using two or three relays gives almost the same performance as if using all of them.
Cross-Layer Performance Analysis of Cooperative ARQ With Opportunistic Multi-Point Relaying in Mobile Networks
(2018-06-01)
Chiu, Hsin-Li
;
Wu, Sau-Hsuan
;
電信工程研究所
;
Institute of Communications Engineering
A cross-layer analysis framework is developed for the design and performance evaluations of cooperative automatic repeat request (ARQ) with opportunistic multi-point relaying (OMPR) in mobile networks. In particular, three exemplar OMPR functions and their combinations are studied for opportunistic distributed space-time coded (ODSTC) retransmissions in time-division duplex long-term evolution advanced systems. According to the complexities and coordination delays of the OMPR functions, the influences of channel fading on the spatial and temporal diversities offered by ODSTC-based ARQ and their impacts on the system throughput, transmission energy consumption, and relays' queuing delays can be evaluated effectively under this framework. Based on the analytical results, a rate adaptation strategy is also proposed to maximize the system throughput subject to constraints on queuing delays at relay stations (RSs) and packet error rates at mobile stations (MSs). Analysis and simulation results show that in typical vehicular speeds, using maximally two active RSs for ODSTC is a very robust and effective choice to provide near best system throughput with less energy consumptions and lower protocol complexities. The throughput gains over a system without using RS retransmissions range from 16 similar to 80% for cell-edge MSs, with only 25 similar to 45% of the transmission energy consumption.
Effectiveness and Relay Efficiency of Opportunistic Multipoint Relaying on Cooperative ARQ
(2017-06-01)
Wu, Sau-Hsuan
;
Chiu, Hsin-Li
;
Li, Jin-Hao
;
電信工程研究所
;
Institute of Communications Engineering
This paper studies the effectiveness and relay efficiency of using opportunistic multipoint relaying and distributed space-time coding (ODSTC) for cooperative Automatic Repeat reQuest (ARQ). According to the complexities for diversity exploration in retransmissions, three types of ARQ protocols are studied herein, allowing us to examine the effectiveness of the protocols and the efficiencies of using ODSTC relaying for ARQ. The efficiency is studied from the viewpoint of the signal quality enhancement per active relay, while the effectiveness is investigated from the perspectives of diversity and throughput improvements with the different protocols. The results show that both are closely related to the link qualities of the forwarding channels. When the link quality between the source and relays is considerably higher than the quality between the relays and the destination, a simple protocol that opportunistically chooses two active relays for ODSTC (ODSTC2) at the beginning of retransmissions is good enough to yield a significant throughput improvement. Otherwise, when the performance is limited by the number of successfully decoding relays, then having relays of unsuccessful decoding to overhear the signals sent by active relays plays a crucial role in resolving the limitation. By having the new successfully decoding relays to participate in the subsequent retransmissions, both diversity and throughput can be significantly improved. According to our analysis and simulation studies, an appropriate protocol with ODSTC2 in general can provide effective throughput improvements in two times retransmissions.
Joint Switched-Beam Training and Rate Adaptation Schemes for MIMO WLANs
(2017-01-01)
Wang, Ju-Chia
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Chiu, Hsin-Li
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Sun, Chia-Shan
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Chao, Hsi-Lu
;
Wu, Sau-Hsuan
A joint beam training and rate adaptation mechanism for downlink transmissions is presented for multiple input multiple output systems with switched beam antennas. The proposed method only depends on the beam patterns and the acknowledgement (ACK) replied by the receiver, and is compatible with the legacy WiFi standards. This feature makes not only the complexity of the beam training scheme extremely low, but also the feasibility relatively high. Due to the practical limitations of antenna designs and manufacturing, beam patterns may not have distinctive directivity for certain directions. Therefore, beam pattern scaling is utilized to make the resultant beam patterns match well with the ideal user directions and channel conditions. Simulation results with real switched beam patterns show that the precision of the training scheme is very high.
Throughput Analysis of LTE and WiFi Heterogeneous Dense Small Cell Networks
(2019-01-01)
Kao, Yi-Hung
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Chiu, Hsin-Li
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Wu, Sau-Hsuan
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Chao, Hsi-Lu
;
Gan, Chai-Hien
The throughput performance of a heterogeneous dense small cell network (HetNet) with collocated WiFi and LTE interfaces is studied herein. From a geometrical statistical viewpoint, the average throughput for LTE with the function of further enhanced inter-cell interference coordination (FeICIC) is investigated in an attempt to find a proper operation setting for FeICIC to benefit users on cell edges. Furthermore, the optimal setting for WiFi offloading is also studied to maximize the worse user experience in such a HetNet. The proposed analysis method allows us to further study a proper strategy that provides fair services to users under the severe interferences in HetNet.
Throughput Performance Study of Smart Antenna System in WiFi Networks
(2020-01-01)
Chiu, Hsin-Li
;
Wu, Sau-Hsuan
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Chao, Hsi-Lu
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網路工程研究所
;
電信工程研究所
The throughput performance of smart antenna systems (SASs) in WiFi networks is studied in this work. Considering a WiFi network whose access points (APs) support the switched-beam SAS, a beam switching strategy which is compatible with the legacy WiFi protocol is proposed to enhance more concurrent links by allowing APs directionally sensing and accessing the wireless channel. The throughput advantage is verified by the simulation results in random deployment scenarios. More importantly, the proposed beam switching strategy provides extra design factors to adjust or balance the downlink and uplink throughput per WiFi user to meet the requirements of various applications and scenarios.