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Motivation

High Spectral Efficient and Flexible Next Generation Mobile Communications Simon Plass, Stephan Sand, Mikael Sternad, and Arne Svensson. Motivation. What are the requirements and challenges for next generation communications systems?

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Motivation

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  1. High Spectral Efficient and Flexible Next Generation Mobile CommunicationsSimon Plass, Stephan Sand, Mikael Sternad, andArne Svensson

  2. Motivation • What are the requirements and challenges for next generation communications systems? • How can these technical challenges be solved?Remark: The focus is on the physical layer (PHY) in this presentation

  3. Analog systems1G UMTS3G ???4G GSM2G Evolution of Mobile Communications Digital systems

  4. 4G GMC Scenarios mobility high speed/ wide area medium speed/ within a city 2G TDMA FDMA 3G CDMA walking speed/ within a limited areas WLAN (IEEE 802.11) OFDM portable/ indoor data rate 0,1 1 10 100 Mbit/s

  5. Main Requirements for 4G • Efficient use of the valuable spectrum • Flat IP architecture for low operational expenditure and less capital expenditure • Flexible spectrum allocation and sharing has to be included • New services based on real time applications, e.g., gaming or new trends of Web 2.0

  6. IFFT IFFT Basic Transmission Technique:Generalized Multi Carrier (GMC) • Robust to multi-path environments • Efficient use of the available spectrum • Flexible allocation of user data to sub-carriers • Includes all OFDM based transmission techniques such as OFDMA, MC-CDMA, SS-MC-MA, IFDMA, etc. Cyclicprefix Space-Time-FrequencyPrecoding Data symbols Cyclicprefix

  7. Predicted CSI Coding p Mod Predicted MIMO-CSI IFFT IFFT Adaptive BICM Cyclicprefix adaptiveSpace-Time-FrequencyPrecoding Data symbols Cyclicprefix Advanced Techniques for the PHY • Adaptive functionalities at the transmitter and receiver exploiting channel state information and user demands • Transmitter: • Adaptive bit-interleaved coded modulation (BICM) • Adaptive Space-time-frequency (STF) precoding

  8. Advanced Techniques for the PHY • Receiver: • Iterative channel estimation, demodulation, and decoding • Improve bit estimates by toggle until regeneration brings optimality (TURBO) principle SISO CSI Inverse OFDMconverted signals STFDecod sink Decod p-1 Demod CSIPrediction ChannelEstimation MIMO CSI

  9. Technical Highlights for 4G Systems • Spectrum Flexibility • Inter-cell Interference Handling • Relaying Concepts

  10. Narrowband 4G I Cand.band Cand.band Candidateband Candidateband 2G & 3Gbands Shared by 4G Shared by 4G 900 MHz 2.6 GHz 3.4 GHz 5 GHz Cand.band Cand.band Candidateband 2G & 3Gbands Shared by 4G II 4G 900 MHz 2.6 GHz 3.4 GHz 5 GHz Cand.band 2G & 3Gbands Candidate band 4G III 900 MHz 2.6 GHz 3.4 GHz 5 GHz Spectrum Flexibility – Spectrum Assignment Concepts • Definition of new spectrum assignment at the World Radiocommunications Conference (WRC) in Oct/Nov 2007

  11. Spectrum Flexibility – Spectrum Sharing Mechanisms • Sharing and Co-existence (spectrum sharing with fixed satellite systems (FSS)) • Use of geographical ‚exclusion zones‘ • Use of directional antennas and beamforming to avoid LOS transmissions towards FSS ground stations • Flexible Spectrum Usage • Long-term spectrum assignment • Short-term spectrum assignment • Resource partitioning

  12. Inter-cell Interference Problem • Goal: High overall spectral efficiency in combination with high flexibility for packet data traffic • Method: Frequency reuse of one and generalized multi-carrier system • Result: Inter-cell interference problem at the cell borders

  13. Inter-cell Interference Handling • Difficulties: • Fast and tight inter-cell coordination is required for maximal gains in interference avoidance • Complication with packet-switched channel-aware scheduled transmission • Possible approaches: • For high loads, allocate low SINR user to a separated frequency pool with frequency reuse of three, the others with reuse of one • For low loads, dynamic frequency assignment and/or coordinated beamforming can be used of the lower fraction of low SINR users • Inter-cell interference cancellation schemes at the receiver, if resources at receiver available

  14. Conclusions We have shown: • The needs of next generation communications systems • The underlying transmission technique GMC • The adaptive components of the PHY • The need of spectrum flexibility and its mechanisms • The need of inter-cell interference handling and possible approaches

  15. Thank you!

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