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Träfflista för sökning "WFRF:(Ibars Christian) "

Sökning: WFRF:(Ibars Christian)

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1.
  • Nasiri Khormuji, Majid, 1981- (författare)
  • Relaying Protocols for Wireless Networks
  • 2008
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Motivated by current applications in multihop transmission and ad hoc networks, the classical three-node relay channel consisting of a source-destination pair and a relay has received significant attention. One of the crucial aspects of the relay channel is the design of proper relaying protocols, i.e., how the relay should take part into transmission. The thesis addresses this problem and provides a partial answer to that. In this thesis, we propose and study two novel relaying protocols. The first one is based on constellation rearrangement (CR) and is suitable for higher-order modulation schemes. With CR, the relay uses a bit-symbol mapping that is different from the one used by the source. We find the optimal bit-symbol mappings for both the source and the relay and the associated optimal detectors, and show that the improvement over conventional relaying with Gray mapping at the source and the relay can amount to a power gain of several dB. This performance improvement comes at no additional power or bandwidth expense, and at virtually no increase in complexity. The second one is a half-duplex decode-and-forward (DF) relaying scheme based on partial repetition (PR) coding at the relay. With PR, if the relay decodes the received message successfully, it re-encodes the message using the same channel code as the one used at the source, but retransmits only a fraction of the codeword. We analyze the proposed scheme and optimize the cooperation level (i.e., the fraction of the message that the relay should transmit). We compare our scheme with conventional repetition in which the relay retransmits the entire decoded message, and with parallel coding, and additionally with dynamic DF. The finite SNR analysis reveals that the proposed partial repetition can provide a gain of several dB over conventional repetition. Surprisingly, the proposed scheme is able to achieve the same performance as that of parallel coding for some relay network configurations, but at a much lower complexity. Additionally, the thesis treats the problem of resource allocation for collaborative transmit diversity using DF protocols with different type of CSI feedback at the source. One interesting observation that emerges is that the joint powerbandwidth allocation only provides marginal gain over the relaying protocols with optimal bandwidth allocation.
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2.
  • Pasanen, Pirjo, et al. (författare)
  • EU FP6 IST-2003-507581 WINNER, D2.6 Assessment of Multiple Access Technologies, Oct 2004.
  • 2004
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The objective of this deliverable is to perform a first assessment of wireless access/multipleaccess technologies for the WINNER system concept. The study of multiple access schemes is theresponsibility of Task 4 within the WINNER workpackage 2. The work requires the collection andassessment of the numerous ideas and proposals available. The technologies and combinations oftechnologies are also assessed and compared, to identify the most promising strategies and combinations.The latter work is primarily performed by multi-link simulation and system-level simulation
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