1. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 1 Adaptive Modulation for MIMO-OFDM Systems Taehyun Jeon, Heejung Yu, and Sok-kyu Lee Next Generation Wireless LAN Research Team, ETRI Young-Doo Kim and Yong H. Lee KAIST

2. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 2 Contents Adaptive Modulation for MIMO-OFDM –SVD based –Layered detection based Simulation results Conclusion

3. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 3 Adaptive Modulation for MIMO-OFDM Spatial-frequency bit allocation and power assignment for antennas and sub-carriers Slow channel variation and channel information is assumed at transmit side for optimal modulation type and power allocation Significant performance advantage over non adaptive systems SVD based scheme [Raleigh & Cioffi, 1998] Layered decision based scheme [K.-W. Ng, 2002]

4. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 4 SVD based scheme (1) Signal Model for MIMO System Singular Value Decomposition of H : is M x M MIMO channel matrix is the channel between Tx and Rx antenna : and are unitary and are singular values of

5. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 5 SVD based scheme (2) Transformation of H into M parallel channels Bits and Power Allocation for each antenna(M) and sub-carriers(N) based on equivalent channel gains –e.g. Water Pouring Algorithm based on MxN channel gains

6. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 6 Layered Detection based scheme (1) Review of detection process (V-BLAST case) –Start i th iteration –Step 1: Compute the nulling matrix W For ZF criteria : –Step 2: Find the layer with max. SNR, SNR ~ –Step 3: Detection for chosen layer (k i th layer) –Step 4: Cancellation of effect by chosen layer –Step 4: Repeat above steps for next layer

7. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 7 Layered Detection based scheme (2) Determination of channel gain for each layer –Layer selection order affects the performance e.g. choose the layer following the descending or ascending order of SNR –Equivalent channel gain can be obtained based on the chosen nulling vector Bits and Power Allocation for MxN flat fading channels

8. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 8 Layered Detection based scheme (3)

9. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 9 Simulation Parameters IEEE 802.11a PHY Based Frame Number of Subcarriers (data subcarriers): 64 (48) Number of Cyclic Prefix: 16 Sampling Rate: 20MHz Modulation: QPSK, 16QAM –Greedy algorithm applied for bit and power allocation –QPSK for non-adaptive scheme Number of Tx and Rx Antennas: 4x4 Channel Coding: None Target Data Rate: 96Mbps Channel Model: Independent MIMO Channel –ETSI/BRAN Channel Model B (RMS Delay Spread = 100ns) –Quasi Static Channel (no change within one frame) –Perfect Channel Estimations

10. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 10 Simulation Results

11. doc.: IEEE 802.11-04/314r0 Submission March 2004 Taehyun Jeon, ETRISlide 11 Conclusions Adaptive MIMO-OFDM Systems are reviewed: SVD and Layered detection based Simulation results show significant performance improvement over non-adaptive scheme Further consideration needed for feedback mechanism of channel information when the channel is asymmetric