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MIMO-OFDM for High-Speed WLANs

MIMO-OFDM for High-Speed WLANs. Fr ederik Petr é Bart Van Poucke André Bourdoux Liesbet Van der Perre Wireless@IMEC f irstname.lastname@imec.be. What is multi-antenna all about?. Phased Array. MTMR. MIMO. SDMA. Smart antenna. Beamfoming. Null steering. Space-time coding.

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MIMO-OFDM for High-Speed WLANs

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  1. MIMO-OFDM for High-Speed WLANs Frederik Petré Bart Van Poucke André Bourdoux Liesbet Van der Perre Wireless@IMEC firstname.lastname@imec.be

  2. What is multi-antenna all about? Phased Array MTMR MIMO SDMA Smart antenna Beamfoming Null steering Space-time coding Adaptive array

  3. 802.11 1-2 Mbps 802.11a/g 6-54 Mbps 4G WLAN 1G WLAN 2G WLAN 3G WLAN 500 m 802.11b 5.5-11 Mbps 802.11n > 100 Mbps Range 50 m 5 m 100 kbps 1 Mbps 10 Mbps 100 Mbps 1 Gbps Maximum Data rate Need for 4G High-Speed WLANs • Higher data rates • Larger range • More users

  4. The indoor propagation channel is best served by space/frequency processing The MIMO hype: a critical review A smart MIMO solution adapts to scene and user needs A smart MIMO-OFDM system is key for 4G high-speed WLANs

  5. delay dispersion Attenuation (dB) user terminal delay Need for ISI mitigation base station angle dispersion Need for full ST processing DoA beamforming not suited The indoor channel suffers from severe multipath propagation

  6. Indoor channel characterized by spatial and frequency selectivity Angular response Frequency response Time response

  7. 4x4 MIMOorSISOCapacity (bit/s/Hz) 3x3 MIMO 2x2 SISO 1x1 SNR (dB) MIMO-OFDM exploits spatial and frequency selectivity MIMO Capacity: n-fold increase possible! Higher data rates Larger rangeLess TX power More users

  8. AP or UT UT or AP H H Stream 1 MIMOTX Proc. Stream 1 Stream 2 Stream 2 MIMO with TX pre-processing AP or UT UT or AP Stream 1 Stream 1 MIMORX Proc. Stream 2 Stream 2 MIMO with RX post-processing SDM/SDMA enables higher data rates/more users • Simple receiver • TX-CSI needed • Reciprocal transceiver at TX • MIMO-TX  SDMA-DL • No TX-CSI needed • Better for time- varying channels • More complex receiver (SIC,ML) • MIMO-RX  SDMA-UL ( Joint TX-RX processing possible )

  9. H AP or UT UT or AP MIMOSpace-time encoding MIMOSpace-time Decoding 1 Stream 1 Stream MIMO with Space-time (block) coding Space-time coding enableslarger range and/or less Tx power • No TX-CSI needed • ML receiver with simple linear processing • No rate enhancement (rate 1 only for Nant = 2) • Also applies to any number of receive antennas • Space-time or space-frequency

  10. Can we conquer the wireless MIMO channel? Can we get the MIMO solution that meets the actual needs (rate/range, multi-user capacity, power)? Can DSP complexity be mastered? Can front-end cost and power be acceptable? Can it elegantly bring its benefits in current systems and standards? Why be skeptical about MIMO?

  11. User HW profile User QoS requirements Channel conditions A smart MIMO system adapts to scene and actual user needs (1) Optimal Mode Selection SDM, STBC, SDMA

  12. SDMA multiplies cell capacity A smart MIMO system adapts to scene and actual user needs (2) Reference SISO case: Pdc, mobile = 1, Rmax = 54 Mbps, Dist max = 1 SDMbrings higher throughput in DL/UL STBC brings robustness

  13. SDMA multiplies cell capacity for single-antenna terminals Reference SISO case: Pdc, mobile = 1, Rmax = 54 Mbps, D max = 1 • Downlink SDMA: Nant X Rmax • Uplink TDMA:PTx-dc, mobile = 0.1-0.8 • ComplexityMobileTerm = SISO • ComplexityBasestation: • digital = Nant x SISO • analog = 0.9 Nant x SISO

  14. STBC brings increased robustness Reference SISO case: Pdc, mobile = 1, Rmax = 54 Mbps, D max = 1 STBC brings Robustness almost for free

  15. SDM brings higher throughput Reference SISO case: Pdc, mobile = 1, Rmax = 54 Mbps, D max = 1 • NT = NR = Nant • Throughputmax: Nant X Rmax, D = up to 2 • ComplexityMobileTerm = • digital = 0.75 Nant x SISO • analog = 0.9 Nant x SISO • ComplexityBasestation: • digital = Nant x SISO • analog = 0.9 Nant x SISO

  16. Standard SISO reference case for PRF = 40mW: 1 antenna, Rx 1 antenna, Tx digital inner modem digital outer modem PDC=1.1 PDC=1.0 MAC 50% 50% Converters I/Q (de)modulator PDC=2.1 PA Local oscillator Where does the power go? IMEC’s reference designs to Low Power: Optimal use of flexibility in FEC in Rx Doherty PA in Tx PDC=0.7 PDC=0.7

  17. Reference case: 2 parallel standard SISO at PRF = 40mW: MT1 PDC=2.1 MT2 PDC=2.1 PDC=4.2 MIMO processing digital inner modem digital outer modem digital outer modem MAC MAC Converters Converters I/Q (de)modulator I/Q (de)modulator PA PA Local oscillator Local oscillator How does power scale in MIMO? IMEC’s smart MIMO at PRF = 40mW: AP PDC=2.6 MT PDC=2.1 50% 50% PDC=2.3 PDC MT Tx PDC MT Rx

  18. s1 s2 s1 s2 s1 s1 s1 SDM SDMA MRC STBC STBC Downlink STBC stbc s1 s2 s1 s2 s1 s1 s1 TX-SDM TX-SDMA TX-MRC STBC STBC s1 s2 s1 s2 s1 s1 SDM SDMA MRC STBC Uplink STBC s1 s2 s1 s2 s1 s1 RX-SDM RX-SDMA RX-MRC STBC Do MIMO upgrades ask for changes to 802.11a standard? • none • extra PHY mode • PHY+MAC

  19. Can we get the MIMO solution that meets the actual needs (rate/range, multi-user capacity, power)? Can DSP complexity be mastered? Can front-end cost and power be acceptable? Can it elegantly bring its benefits in current systems and standards? Yes! IMEC’s smart MIMO says YES to crucial questions

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