Browsing by Author "Li, Jin-Hao"

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Cooperative ARQs with Opportunistic Distributed Space-Time Coding: Effective Protocols and Performance Analysis
(2010)
Chiu, Hsin-Li
;
Wu, Sau-Hsuan
;
Li, Jin-Hao
;
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.
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.