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Armin Dammann, Stephan Sand Barcelona, March 9-10, 2005

NEWCOM DLR Research Topics and Activities. Armin Dammann, Stephan Sand Barcelona, March 9-10, 2005. German Aerospace Center (DLR) The national aerospace research center and space agency. DLR Research Center Oberpfaffenhofen Institute of Radio Frequency Technology and Radar Systems

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Armin Dammann, Stephan Sand Barcelona, March 9-10, 2005

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  1. NEWCOM DLR Research Topics and Activities Armin Dammann, Stephan Sand Barcelona, March 9-10, 2005

  2. German Aerospace Center (DLR)The national aerospace research center and space agency • DLR Research Center Oberpfaffenhofen • Institute of Radio Frequency Technology and Radar Systems • Institute of Communications and Navigation • Institute of Methods of Remote Sensing • Institute of Optoelectronics • Institute of Physics of the Atmosphere • Institute of Robotics and Mechatronics • German Space Operation Center • German Remote Sensing Data Center • Total Staff in Oberpfaffenhofen:  1000 31 Research Institutes and Scientific/Technical Facilities at 8 Sites 4 Branches German-DutchWind Tunnels (DNW) European Transonic Wind Tunnel (ETW) Total Staff:  5000 Institute of Communications and Navigation Activities and Research in Communications • Research Activities in Terrestrial Communications • DoCoMo Euro-Labs research collaboration • Combination of communications and navigation • EU projects: • 4MORE (4G MC-CDMA Multiple Antenna Systemon Chip for Radio Enhancements) • WINNER (Wireless World Initiative New Radio) • NEWCOM (Network of Excellence in Wireless Communications) • Research Activities in Satellite Communications • Signal design of the satellite navigation system Galileo • Optical free space communications(inter satellite links) • Broadband satellite services to aircraft for wireless access technologies

  3. Institute of Communications and NavigationDepartment of Communications Systems Topics of the Mobile Radio Transmission Group • Multicarrier Transmission Systems • Multiple access (MC-CDMA) • Detection for MC-CDMA and related schemes • Channel estimation • Multicellular environments • Multiple Antenna Techniques (Cyclic Delay Diversity, Doppler Diversity, …) • Combination of Communications and Navigation • Performance improvements of 4G mobile radio systems using GALILEO • Navigation by means of 4G systems • Involvement in EU-projects NEWCOM, WINNER and 4MORE

  4. Institute of Communications and NavigationDepartment of Communications Systems Possibilities of Cooperation • Joint publications • Meetings, Seminars, Colloquia, Talks • Exchange of researchers • Undergraduate • Diploma/Master theses at DLR • Internships at DLR • Graduate, Postgraduate, … • Visit as guest scientists at DLR • Visit of DLR research staff at NEWCOM partner institutions

  5. Coding Design for OFDM and MIMO SystemsPerformance of Differential Modulation in OFDM Systems with CDD and DoD • Cyclic Delay Diversity (CDD) and Doppler Diversity (DoD) schemes offer additional diversity in frequency resp. time direction • This means contemporarily a decorrelation of the subcarriers in frequency and/or time.  TX antenna diversity techniques above can be viewed as “channel transformation” • Differential modulation schemes, however, suffer from a decorrelation of the channel fading CDD Transmitter DoD Transmitter Spectral shift of time domain signal by complex valued exponential functions. Cyclic shift of time domain OFDM symbol CDD shifts TX signals (cyclically) in time. This decreases fading correlation in frequency direction DoD shifts TX signals in frequency. This decreases fading correlation in frequency direction

  6. Coding Design for OFDM and MIMO SystemsPerformance of Differential Modulation in OFDM Systems with CDD and DoD Influence of CDD on a 12-tap Rayleigh fading channel (snapshots of the channel transfer function) 2 TX antenna CDD 1 TX antenna Frequency selectivity increases increased frequency diversity  diff. mod. suffers, when done in frequency direction • Key questions: • The modulation and diversity strategye.g. increase frequency domain diversity only while differential modulation is done in time direction or vice versa. • Find optimum tradeoff between additional diversity and differential modulation performance

  7. Turbo Processing in MC-CDMAand Related Systems The Topic • Detection of users in MC-CDMA or related systems with a-priori information • Exploit soft-out decoding results of outer channel coding schemes • View MC-CDMA as (serial) concatenation of a Walsh-Hadamard code and an outer channel code. • Investigate the convergence behavior Key Questions: • The shape of extrinsic information transfer (EXIT) charts with respect to • Symbol mapping • User load • Rotation of spreading sequences • Different multipath fading channels • Proper channel codes for turbo processing • Detection/Decoding procedure for outer turbo codes • Include WH-Decoding in turbo decoding iterations or … • … doing turbo decoding as an inner iteration process, while an outer iteration process includes WH-Decoding Activities in that topic are currently running at DLR

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