![5(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved
Pilot patterns for spatial multiplexing
Antenna
port #0
Antenna
port #2
Antenna
port #3
180
[KHz]
0.5 [msec]
Antenna
port #1](https://image.slidesharecdn.com/ltemimoschemes-151023051302-lva1-app6891/85/Lte-mimo-schemes-5-320.jpg)
Lte mimo schemes
- 1. MIMO schemes in 3GPPMIMO schemes in 3GPP--LTELTE (Dec. 2007)(Dec. 2007) Jacob Scheim, Ph.D.Jacob Scheim, Ph.D.
- 2. 2(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved MIMO schemes in 3GPP-LTE Downlink Background Infrastructure for MIMO over LTE SU-MIMO MU-MIMO Transmit diversity Uplink
- 3. 3(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Background Max. code words - 2 Max. Tx. Antennas – 4 Potentially up to four layers Pre-coding 16 elements, unitary, for SU-MIMO
- 4. 4(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Pilot patterns for spatial multiplexing R0 R0 R0 R0 R0 R0 R0 R0 0=l 6=l 0=l 6=l 00000000 00000000 00000000 00000000R0 00000000 00000000 00000000 00000000R0 R0 R0 00000000 00000000 00000000 00000000R0 00000000 00000000 00000000 00000000R0 R0 R0 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 R1 R1 R1 R1 000000000 000000000 00000000 00000000 000000000 000000000 00000000 00000000 R1 R1 R1 R1 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000000000000 000000000 000000000 000000000 000000000 000000000000000000 even-numbered s lots odd-numbered slots 000000000 000000000 000000000 000000000 000000000 000000000 00000000 00000000 00000000 00000000 000000000 000000000 000000000000000000000000000000000000 00000000 00000000 0000000000000000 R3 R3 R3 R3 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000R0 0000000000000000 00000000 00000000 0000000000000000 00000000 00000000R0 R0 R0 even-numbered slots odd-numbere d slots 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000R0 0000000000000000 00000000 00000000 0000000000000000 00000000 00000000R0 R0 R0 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000 000000000000000000 000000000000000000 R1 R1 R1 R1 even-numbered s lots odd-numbered slots 000000000 000000000 000000000 000000000 000000000 000000000 00000000 00000000 000000000 000000000 000000000 000000000 000000000000000000 0000000000000000 R1 R1 R1 R1 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000000000000000000000000000 00000000 00000000 0000000000000000 even-numbe red slots odd-numbered slots 00000000 00000000 00000000 00000000 000000000 000000000 00000000 00000000 00000000 00000000 00000000 00000000 0000000000000000 000000000 000000000 00000000 00000000 0000000000000000 R2 R2 R2 R2 OneantennaportTwoantennaportsFourantennaports Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3 Not used for transmission on this antenna port Referencesymbols on this antenna port
- 5. 5(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Pilot patterns for spatial multiplexing Antenna port #0 Antenna port #2 Antenna port #3 180 [KHz] 0.5 [msec] Antenna port #1
- 6. 6(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Comments on reference signal Is not affected by applying pre-coding Is not affected by applying transmit diversity Reference signals density reduces with number of antennas: Higher layer MIMO for lower mobility
- 7. 7(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Multi layer data transmission (SU-MIMO) Space Rank 2 MIMO Rank 4 MIMO
- 8. 8(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Data/Control partitioning Increased <= rate region Increased diversity => region 1 msec
- 9. 9(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Peak rates for LTE-MIMO “Back of the envelope” calculations: 11x12 – generic tile size (assuming max. control symbols) Peak rate: 64 QAM - 6 bits/symbols Code rate - 1 (no FEC) BW - 20 MHz - 110 RBs Sub-frames per second - 1000 Peak rates calculation: SISO: 11*12*6*110*1000 =87 Mbps MIMO (2x2, 4x2) doubles the rate >150 Mbps MIMO (4x4) quadruples the rare= >300 Mbps High class UEs category 5 (with 4 Rx antenna) may exceed 300 Mbps
- 10. 10(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Infrastructure Pre-coding for what: Increasing SNR (“Beam-forming”) Decreasing intra-cell interference Decreasing inter-cell interference Code book design Unitary matrices (Householder based) 16 matrices for 4x(1:4) scheme Feedback: Wideband Narrowband Channel quality indication Per layer Feedback Wideband Narrowband
- 11. 11(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Comments on MU-MIMO (SDMA) Requires standard adaptation for SDMA: Optimizing the pre-coding codebook Changing the CQI feedback structure User A User B User D User C
- 12. 12(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved DL – transmit diversity modes Transmit diversity 1 stream to 2 antennae port - Alamouti scheme 1 stream to 4 antennae port – Alamouti alike scheme Two ‘parallel’ Alamouti schemes Cyclic delay diversity (CDD) Zero/small delay diversity Large delay diversity
- 13. 13(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Transmit diversity * 0 * 1 10 xx xx − Origin*: Antenna Time * 01 * 10 xx xx − Antenna Freq. LTE: Rate 1 code Diversity order = 2 Two transmit antennas Basic assumptions: Two transmit chains Channel doesn’t change along the ‘retransmission’ * S.M. Alamouti "A simple transmit diversity technique for wireless communications," IEEE JSAC vol. 16 (8), pp. 1451–1458
- 14. 14(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Transmit diversity cont… * 23 * 32 * 01 * 10 00 00 00 00 xx xx xx xx − − Antenna Freq. 0123 * 1 * 0 * 3 * 2 * 2 * 3 * 0 * 1 3210 xxxx xxxx xxxx xxxx −− −− −− Antenna Time Rate 1 code Diversity order = 2 (spatial) Rate 1 code Diversity order < 4 Four transmit antennas LTE: Alternative*: * Hamid Jafarkhani "A quasi-orthogonal space–time block code," IEEE Trans. Comm. Vol. 49 (1): pp. 1–4 Unbiased scheme (Ch. Est.) Biased scheme (Ch. Est.)
- 15. 15(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Transmit diversity Summary: STBC => SFBC For 4 transmit antennas Diversity order equals 2 Unbiased channel estimates
- 16. 16(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Cyclic delay diversity x0 x1 x2 xN-2 xN-1 FFT Modulator 1st Tx. antenna FFT Modulator 2nd Tx. antenna Xd-1 x0 x1 x2 xN-2 xN-1 xd Xd+1 Xd-2
- 17. 17(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Problem The pilots are processed also… Solution Project the processing backwards – prior the FFT CDD requires extra processing for channel estimation Pilots remain orthogonal Cyclic delay diversity
- 18. 18(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved Uplink Requirements Open loop Tx diversity: SxBC, CDD 2x2 MU-MIMO Virtual MIMO 2x2 SU-MIMO Standard Preliminary stages The TS 36.211 doesn’t reflect currently any decision taken Technically The same as DL Reference signals are orthogonal by time division Between antennas orthogonal sequences may be used Two transmit antennas A single RF chain?
- 19. 19(C) 2007 Comsys communication and Signal Processing Ltd. All rights reserved www.comsysmobile.com