Iterative receiver architectures for MIMO HSDPA Date 03/11/04 R. Visoz, A.O. Berthet The present document contains information that remains the property of France Telecom. The recipient’s acceptance of this document implies his or her acknowledgement of the confidential nature of its contents and his or her obligation not to reproduce, transmit to a third party, disclose or use for commercial purposes any of its contents whatsoever without France Telecom’s prior written agreement. France Telecom D1 - 08/11/2004 Research & Development
Iterative receiver architectures for MIMO HSDPA s Why? Q Disappointing results for MIMO HSDPA performance under a non iterative receiver assumption, at least for 2x2 configuration Q From an information theory point of view, only spatial multiplexing can offer a significant gain in spectral efficiency (code re-use) Q Spatial multiplexing adds, on top of Multi-User Interference (MUI) and Inter-Chip Interference (ICI), Multiple Antenna Interference (MAI) Q As a result, the spectral efficiency of MIMO HSDPA relies on efficient receiver architectures that can deal with MAI+ICI+MUI Q The most efficient receivers combine MIMO and Turbo principle = Turbo- MUD France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D2 - 08/11/2004
Spatial MCS design s Our spatial Modulation and Coding Schemes (MCSs) are built from a well-known potentially capacity achieving transmission scheme : ST-BICM with Linear Precoding s Overloaded linear precoding may introduce further flexibility in spatial-MCS design France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D3 - 08/11/2004
Spatial MCS design s ST-BICM-LP [ ] [ ] [ ] x n d 1,1 n s n 1,1 1,1 Mapper N × K [ ] x l Spreading 1 [ ] [ ] [ ] d 1 n s 1 n x 1 n Matrix W (1) Mapper [ ] [ ] [ ] s n x n d 1,K n 1,K 1,N NT × KT Π Spreading [ ] Outer code x l Matrix W [ ] [ ] [ ] x n d T,1 n s n T,1 T,1 Mapper N × K [ ] Spreading [ ] [ ] x T n d T n s T n [ ] Matrix x l T W (T) Mapper [ ] [ ] [ ] d T,K n s n x n T,K T,N France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D4 - 08/11/2004
Receiver architecture (example) MMSE criterion is spread in the receiver architecture from the decoder to the decoder SISO ˆ � ˆ ˆ � S Y MAI+ISI MUI Y X Z Z demapping treatment treatment − − (log-domain) MAI+ISI MUI regeneration regeneration from the decoder S SISO S S X Z mapper spreading (log-domain) France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D5 - 08/11/2004
Simulation results s All simulations are based on Q rate-1/2 PCCC, 4608 uncoded block size Q Gray labeling Q SF =16 Q 2x2 MIMO channel Q Veh A channel profile Q perfect channel estimation Q MMSE chip-equalizer with sliding window length 21 Q No iteration within the turbo-code (AdHoc scheduling) s For all simulations 2 benchmarks: Q MFB => Genie Aided receiver 5 turbo-code iteration Q Outage Capacity => probability that the channel capacity is below the transmission rate France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D6 - 08/11/2004
simulations results s QPSK, 100% load per antenna, 2bpcu 1 ,0E+00 outage 1 ,0E-01 MFB (5 iter) 1.3 dB MMSE it0 BLER 1 ,0E-02 MMSE it1 MMSE it5 MMSE it14 1 ,0E-03 1 ,0E-04 -2 0 2 4 6 Eb/No (dB) France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D7 - 08/11/2004
simulations results s 16-QAM, 100% load, 4bpcu 1 ,0E+00 outage 1 ,0E-01 MFB (5 iter) BLER MMSE it0 MMSE it1 4 dB MMSE it5 1 ,0E-02 MMSE it14 1 ,0E-03 0 2 4 6 8 1 0 Eb/No (dB) France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D8 - 08/11/2004
simulation results s 64-QAM, 100% load, 6pbcu 1 ,0E+00 outage 1 ,0E-01 MFB (5 iter) MMSE it0 BLER MMSE it1 6dB MMSE it5 1 ,0E-02 MMSE it14 1 ,0E-03 2 4 6 8 1 0 1 2 1 4 Eb/No (dB) France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D9 - 08/11/2004
Conclusion s Iterative receiver architectures are needed to extract the spatial multiplexing gain brought by MIMO = Key feature for the UMTS evolution s Iterative receiver architectures enable the use of power and spectrally efficient spatial-MCS = ST- BICM-LP s Iterative receiver architectures should be investigated within the standardization process since they condition the choice of the transmission schemes (SI?) France Telecom Distribution of this document is subject to France Telecom’s authorization Research & Development D10 - 08/11/2004
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