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On The Study Of Reliable Transmission Techniques For Multi-Antenna Relay System

Posted on:2015-01-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:R H CaoFull Text:PDF
GTID:1228330467963653Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
The rise of relay technology has greatly improved the coverage and con-nectivity of communication networks. And the integration of multiple-input-multiple-output (MIMO) technique with relay network is expected to further optimize the performance of communication system. This dissertation mainly focuses on the techniques which intends to guarantee the reliability of trans-mission in multi-antenna relay system. Towarding this goal, the dissertation puts effort into the following two aspects. Firstly, the diversity technique cop-ing with noise and channel fading is developed in the dissertation. Second-ly, the study on attack detection technique against malicious interference from unreliable relays is also given by the dissertation. To be more specific, the dissertation proposes low-complexity detection, signal combination and relay selection schemes achieving full diversity gain. Meanwhile, the dissertation al-so consider to handle the substitution attack by only using the signals observed from physical-layer. Finally, all the results obtained by the dissertation provide the insight that the path-diversity of relay system can be utilized to protect in-formation from interference regardless of who imposes the interference. The major contributions are summarized as follows.To begin with, the dissertation proposes a specific physical layer net-work coding (PNC) detection scheme for the two-way relay channel (TWR-C). Unlike the traditional binary PNC that focuses mainly on BPSK modula-tion, the proposed PNC scheme is tailored for the general M-ary phase-shift keying (MPSK) modulation. The proposed PNC-specific detector obtains the network-coded symbol (NCS) straightforwardly without having to detect in-dividual symbols separately. Comparing with the optimal multi-user detector (MUD) which searches over the combinations of all users’modulation constel-lations, the proposed detector searches over only one modulation constellation, thus simplifies the NCS detection. In particular, the product of the two modu-lated signals is considered as a network-coded symbol. The proposed network coding operation occurs naturally in the inner or outer product of the received signal. A novel PNC-specific detection principle is then developed to estimate the network-coded symbol from the inner or outer product according to the maximum likelihood (ML) principle. Simulations show that the detector based on outer product achieves near optimal performance in terms of end-to-end bit error rate (BER), where the relay node is equipped with multiple antennas.Second, the dissertation proposes a symbol-based PNC (SPNC) technique with MPSK modulation in TWRC. SPNC employs the PNC-specific detector for obtaining NCS. It hence inherits the low-complexity advantage from PNC-specific detector. Furthermore, SPNC developed some advanced transmission techniques in order to help PNC-specific detector achieve full diversity gain in more general scenario and with more efficiency. Despite the reduced complex-ity, SPNC achieves full diversity in multi-antenna relay as the optimal MUD does. Specifically, antenna selection based SPNC (AS-SPNC) scheme and sig-nal combining based SPNC (SC-SPNC) scheme are proposed. Our analysis of these two schemes not only confirms their full diversity performance, but also implies when SPNC is applied in multi-antenna relay, TWRC can be viewed as an effective single-input multiple-output (SIMO) system, in which AS-PNC and SC-PNC are equivalent to the general AS scheme and the maximal-ratio combining (MRC) scheme. Moreover, an asymptotic analysis of symbol error rate (SER) is provided for SC-PNC considering the case that the number of relay antennas is sufficiently large. In addition, the dissertation extends SPNC technique into MQAM modulation, which further enhance the application of SPNC technique.Third, the dissertation proposes a phase rotation (PR) aided relay selection (RS) scheme that aims to improve end-to-end SER performance for a two-way relay network (TWRN) performing decode-and-forward (DF) protocol. The proposed PR technique makes MaxMin method achieve full diversity gain in DF-based uncoded TWRN. The PR is proposed to enlarge the minimum de-cision distance so as to improve the SER performance, which allows MaxMin RS technique to achieve full diversity gain. This performance is confirmed by theoretical analysis. The theoretical result also indicates the proposed PR aided MaxMin-RS approach obtains an improved array gain. Furthermore, compar-ing to the existing DF-based schemes, the proposed scheme allows more flex-ible relay antenna configurations. In addition, the dissertation also proposes a PR aided time extension scheme, which do not need channel state information (CSI) feedback in practical. And simulation shows this scheme still achieves full diversity gain combining with MaxMin-RS approach.Finally, the dissertation proposes the techniques of attack detection from physical-layer. The dissertation obtains the channel conditions under which substitution attacks performed by relay node(s) in a relay network can be de-tected. It is demonstrated that maliciousness of the relays can be asymptotically detected with sufficient channel observations if and only if these relays do not collude and the network satisfies a non-manipulability condition. The disser-tation further discusses the practical meaning of non-colluding network. By analysis, the dissertation indicates non-colluding network in practical means all relays independently alter their signal, and all relays do not cooperate in de-signing altering method. Moreover, the dissertation gives the method to check whether the relay networks satisfy the non-manipulability condition, and how to locate the malicious relay. Note that the proposed detection methods do not need the help of secure side information such as secret key and clean reference. Hence, comparing to the existing key-based schemes, the proposed methods takes advantage of transmission efficiency.
Keywords/Search Tags:Cooperative Communications, Two-way Relay, Multiple-Input-Multiple-Output, Spatial Diversity, Relay Selection, Physical-layerSecurity
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