指導教授：蘇炫榮臺灣大學：電信工程學研究所李崇丕Lee, Chung-PiChung-PiLee2014-11-302018-07-052014-11-302018-07-052014http://ntur.lib.ntu.edu.tw//handle/246246/264272For the uplink relay-aided transmission in a cellular system, the spectral efficiency of mobile radio networks can be improved by introducing relays to assist the transmissions of mobile stations. Further performance improvement can be expected if each relay aids not just a single mobile station, but many simultaneously. In this dissertation, we study the multiple-access relay channel (MARC), in which multiple users transmit messages to a common destination with the assistance of a relay. There are two protocols to be considered: 1) dynamic decode-and-forward (DDF) protocol and 2) compute-and-forward (CMF)protocol. In a variety of MARC settings, DDF protocol is very useful due to its outstanding rate performance. However, the lack of good structured codebooks so far hinders practical applications of DDF for the MARC. For the DDF protocol, two classes of structured codes for theMARC are proposed: 1) one-to-one relay-mapper aided multiuser lattice coding (OMLC), and 2) modulo-sum relay-mapper aided multiuser lattice coding (MS-MLC). The former enjoys better rate performance, while the latter provides more flexibility to tradeoff between the complexity of the relay mapper and the rate performance. It is shown that, in order to approach the rate performance achievable by an unstructured codebook with maximum-likelihood decoding, it is crucial to use a new K-stage coset decoder for structured O-MLC instead of the one-stage decoder proposed in previous works. However, if O-MLC is decoded with the one-stage decoder only, it can still achieve the optimal DDF diversity-multiplexing gain tradeoff in the high signal-to-noise ratio regime. As for MSMLC, its rate performance can approach that of the O-MLC by increasing the complexity of the modulo-sum relay-mapper. Finally, for practical implementations of both O-MLC and MS-MLC, practical short length lattice codes with linear mappers are designed, which facilitate efficient lattice decoding. When the channel links from the users to the relay are weak, DF-based protocol may fail to decode all users at the relay. Aiming to solve this problem, we propose a new lattice coding based on the CMF protocol, where the relay only needs to decode an integerweighted-sum of users’ lattice codewords, re-maps it with a modulo-basedmapper and then forwards the corresponding codeword. Although the decoding at the relay is akin to the orthogonal CMF protocol, we relax the restriction imposed by previous works that the users have to be silent when the relay is transmitting to avoid interference. The key ingredient is the joint multiuser lattice decoding performed at the destination. This jointly decoding strategy not only complicates the corresponding code design but also the error analysis. Simulation results show that the proposed coding schemes outperform existing schemes in terms of outage probabilities and the achievable rates in a variety of channel settings.Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Chapters: 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Motivation and Contributions . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Dissertation Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Multiple Access Relay Channel and Preliminaries . . . . . . . . . . . . . . . . 11 2.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2 Review of Lattices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2.1 Lattice Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2.2 Loeliger Lattice Ensemble . . . . . . . . . . . . . . . . . . . . . 17 2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3. DDF-based Multiuser Lattice Coding for the Multiple-access Relay Channel . . 19 3.1 Relay-Mapper Aided Multiuser Lattice Coding Scheme . . . . . . . . . 20 3.1.1 Encoders: Nested Lattice Codebooks and Relay Mappers . . . . 20 3.1.2 Proposed K-stage Coset Decoders . . . . . . . . . . . . . . . . . 24 3.2 Performance Analysis of the Proposed Coding Schemes . . . . . . . . . 32 3.3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4. CMF-based Multiuser Lattice Coding for the Multiple-access Relay Channel . 50 4.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.2 Non-orthogonal Lattice Coding withModulo-sumComputation and Joint Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.2.1 Encoding Process for the Users . . . . . . . . . . . . . . . . . . 54 4.2.2 Decoding and Mapping at the Relay . . . . . . . . . . . . . . . . 55 4.2.3 Two-stage Joint Coset Decoder at the Destination . . . . . . . . 56 4.3 Performance Analysis of the Proposed Coding Scheme . . . . . . . . . . 58 4.4 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Appendices: A. Proof of Lemma 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 B. Proof of the Rate Region of MS-MLC with the K-stage Decoder in Theorem 2 71 C. Proof of (A.1 b) for Lemma 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 D. Proof of (3.13) for Corollary 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 78 E. Proof of Theorem 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832988743 bytesapplication/pdf論文公開時間：2016/08/17論文使用權限：同意有償授權(權利金給回饋學校)多重存取中繼通道解調後傳輸計算後傳輸晶格編碼共 集合解碼器[SDGs]SDG3thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/264272/1/ntu-103-D96942016-1.pdf