1 / 78

A 3-Dimensional Joint Interleaver for 802.11n MIMO Systems

A 3-Dimensional Joint Interleaver for 802.11n MIMO Systems. Jeng-Hong Chen (jhchen2@winbond.com) Pansop Kim (pkim@winbond.com) Winbond Wireless Design Center Torrance, CA, USA September 2004. Simulation Parameters (based on 11a). 2X2, 2X3, 2X4, 3X2, 3X3, 3X4, 4X2, 4X3, 4X4 antennas

malo
Télécharger la présentation

A 3-Dimensional Joint Interleaver for 802.11n MIMO Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A 3-Dimensional Joint Interleaver for 802.11n MIMO Systems Jeng-Hong Chen (jhchen2@winbond.com) Pansop Kim (pkim@winbond.com) Winbond Wireless Design Center Torrance, CA, USA September 2004 Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  2. Simulation Parameters (based on 11a) • 2X2, 2X3, 2X4, 3X2, 3X3, 3X4, 4X2, 4X3, 4X4 antennas • 11n Channel B, D, E and 11g uncorrelated exponential channel • OFDM based on 11a: 64-pt FFT (only 48 data sub-carriers) • 10% PER over 1000 simulated packets • 1000 un-coded bytes per packet • Perfect CSI, Perfect AFC, AGC, ACQ • No pulse shaping filter, no ADC/DAC • CC rates=1/3,1/2, 2/3,3/4,7/8 from ½ CC code (K=7) with puncturing/repetition • BPSK, QPSK, 16QAM, 64QAM • Interleaver defined in 11a and joint interleaver • 6, 8, 12, 18, 24, 36, 48, 63 Mbps per transmit antenna • MMSE Receiver Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  3. System Models PART-III: Coding Rates & MIMO Tables PART-I: Joint 3D Space-Frequency-Time Interleaver PART-II: Circulation Transmittion (1) OFDM Symbol Based Circulation (2) Sub-carrier Based Circulation Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  4. Challenges of MIMO Interleaver Design • L=Number of OFDM symbols from FEC outputs • NI=Number of OFDM symbols per 3D Joint Interleaver • NOFDM= Number of OFDM symbols are transmitting at the same time • M=Number of transmitter antennas (M NOFDM) • NCBPS=Number of coded bits per OFDM symbol • Nsub=Number of data sub-carriers per OFDM symbol • NBPSC=Number of coded bits per sub-carrier • Example: L=18, NI =6, NOFDM =2, M=3, and Nsub=48 (see next page) • How to choose an appropriate interleaver size, NI, for a MIMO system? • How to transmit NOFDM (M) OFDM symbols at the same time from M TX Ant.? • How to interleave total NI*NCBPS coded bits from FEC outputs and map into • NI*Nsub sub-carriers (frequency domain) and various NBPSC for different QAM • M TX antennas (spatial domain) and • NI total OFDM symbols and NOFDM at the same time? Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  5. Example: L=18, NI =6, NOFDM =2, M=3, and Nsub =48 18 OFDM 6 OFDM 6 OFDM 6 OFDM ? Uncoded bits 1 OFDM Time=t9 t8 t7 t6 t5 t4 t3 t2 t1 ? Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  6. PART-I: 3D Joint Interleaver Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  7. Transmitting Total L OFDM Symbols from M TX Antennas Coded bits has L OFDM symbols NI OFDM symbols NI OFDM symbols MIMO Circulation To M TX Antennas • Properties of a MIMO OFDM System: • Diversities include space (antennas),frequency (sub-carrier),and transmission in times • Adjacent coded bits from FEC are highly correlated within dfree bits • Same sub-carrier (frequency domain) from different antennas are correlated • The correlation between adjacent sub-carriers are strongly correlated especially if rms of delay spreading is small. • Purpose of 3D Joint interleaver (Part-II) and Circulation Transmission (Part-III) • Adjacent FEC coded bits are transmitted from nonadjacent sub-carriers and different TX antennas A(k) B(j) 1D output bit stream 1D input bit stream 1-to-1 mapping Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  8. 11a Interleaver 11a Interleaver A(K) B(j) • Two-step permutation • First permutation • To ensure that adjacent coded bits are mapped onto nonadjacent subcarriers • Three subcarrier separations between consecutive coded bits • Example: NBPSC=1, NCBPSC=48 Reading order (index of j) Writing order (index of k) • Second permutation (Only applied to 16QAM and 64QAM) • To ensure that adjacent coded bits are mapped alternately onto less and more significant subcarriers Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  9. Parallel 11a Interleavers (A1) • Example: NI=4 ,NBPSC=1, NCBPS=48 • Adjacent bits (ex, A(0), A(1), A(2) and A(3)) are assigned to the same TX antenna. • Performance is worse if low correlations between Tx antennas and small delay spread. Coded bits from FEC outputs Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  10. Parallel 11a Interleavers (A2) • Example: NI=4 ,NBPSC=1, NCBPS=48 • Adjacent bits (ex, A(0), A(1), A(2) and A(3)) are assigned to the same subcarrier. • Performance is worse if high correlations between Tx antennas and large delay spread. Coded bits from FEC outputs Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  11. 2D Joint 11a interleaver • Example: NI=4 ,NBPSC=1, NCBPS=48 • First Permutation (the number of rows is NI times.) Writing order (index of k) Reading Order (index of j) • Second Permutation • The same as the 11 a interleaver • Only apply to 16QAM and 64QAM Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  12. 2D Joint 11a Interleaver (B1) • Example: NI=4 ,NBPSC=1, NCBPS=48 • Adjacent bits (ex, A(0), A(4),A(8), and A(12).) are assigned to the same subcarrier, • Performance is worse if high correlations between Tx antennas and large delay spread. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  13. 2D Joint 11a Interleaver (B2) • Example: NI=4, NBPSC=1, NCBPS=48 • Adjacent bits (ex, A(0), A(1), A(2),.. and A(15)) are assigned to the same TX ant. • Performance is worse if low correlations between Tx antennas and small delay spread. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  14. Proposed 3D Joint Interleaver • Purposes • Backward compatible with 11a interleaver and preserve all good properties • To separate consecutive bits by 3*NBPSC or 3 sub-carriers. • To assign consecutive bits to different OFDM symbols • Example: NI=4, NBPSC=1, NCBPS=48 • Rotating the output bits of 2D 11a Joint Interleaver (B2) to different OFDM symbol Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  15. Indexing of Proposed 3D Joint Interleaver k: the index of coded bit before the first permutation i: the index after the first and before the second permutation j: the index after the second permutation, just prior to modulation mapping • First permutation rule where • Second permutation rule where • This interleaver can be easily implemented with 3D block memory Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  16. Input/Output Indexing (BPSK, NI=4, NCBPS=48) Input Index A(k) adjacent FEC coded bits Output Index B(j) different OFDM symbols adjacent 3 sub-carrriers different OFDM symbols Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  17. Generalized 3D Joint Interleaver NI =width of 3D interleaver=number of OFDM symbols Ncolumn=length of 3D interleaver=number of columns Nrow=NCBPS/Ncolumn=height of 3D interleaver=number of rows NSCPC=NCBPS/Nrow=number of subcarriers in one column NCBPS= Nrow Ncolumn=number of bits per OFDM symbol NSC = NSCPR Ncolumn=number of subcarriers per OFDM symbol Guaranteed separation of consecutive coded bits is NSCPC subcarriers. Guaranteed separation of coded bits in consecutive subcarriers is (NINcolumn) bits • First permutation rule where • Second permutation rule where Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  18. Generalized 3D Joint Interleaver NI bits Input Index A(k) Nrow bits NSC (subcarriers)= NSCPR Ncolumn NCBPS (bits)= Nrow Ncolumn Ncolumn bits NSCPC=Nrow/NBPSC Sub-carriers Output Index B(j) • Applicable to all numbers of TX antennas, e.g., NI=1,2,3,4,5,… • Applicable to all QAM modulations, e.g., NBPSC=1(BPSK),2(QPSK),4(16QAM), 6(64QAM),8,… • Applicable to both 20MHz and 40 MHz bandwidth • EX: NSC=48 (11a),54,96,108,114, or other numbers of subcarriers • EX: Ncolumn=6, 16 (11a),18 or other numbers of bits per column • Choose Ncolumnconsecutive coded bits has NSCPR=NSC/Noolumn subcarriers separation • EX: BW=40MHz, NSC=108, Ncolumn=18, NSCPR=6 subcarriers separation Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  19. 3D Joint Interleaver vs. Parallel 11a Interleaver (A2) • Channel D, half lambda, 2X2 SMX • 3D Joint interleaver performs better as expected. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  20. 3D Joint interleaver vs. 2D Joint 11a Interleaver (B1) • Channel B, half lambda, 2(4)X2 CSMX • 3D Joint Interleaver performs better. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  21. Input/Output Indexing (QPSK, NI=4, NCBPS=96) Input Index A(k) Output Index B(j) Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  22. Input/Output Indexing (16QAM, NI=4, NCBPS=192) Input Index A(k) Output Index B(j) 2nd Permutation Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  23. Input/Output Indexing (64 QAM, NI=4, NCBPS=288) Input Index A(k) Output Index B(j) 2nd Permutation Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  24. TGn Sync Interleaver (IEEE 802.11-04/889r0) • Ex. 20 MHz, NBPSC=1, NI=4, NCBPS=48, Ncolumn=16 • Note: NSS=4in the definition of above document. • Adjacent bits (ex. A(0), A(1), …, A(11)) are not evenly distributed over all subcarriers • Adjacent bits (ex. A(3),A(6),A(9),A(12)) are assigned to the same subcarrier. • Winbond proposed 3D Joint Interleaver, NBPSC=1, NI=4, NCBPS=48, Ncolumn=16 Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  25. WWiSE Interleaver (IEEE 11-04-0886-00-000n) • Ex. 20 MHz, NBPSC=1, NI=4, NCBPS=54 • Note: NCBPS=216, NSS=NI,IDEPTH=Ncolumn in the definition of above document. • Adjacent bits (ex. A(0), A(1), …, A(11)) are not evenly distributed over subcarriers. • Some adjacent bits (ex. A(21), A(27)) are on the same subcarrier. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  26. WWiSE Interleaver (IEEE 11-04-0886-00-000n) • Note: Equation (14) in the above doc. has been changed from to to shift Dn subcarriers for NBPSC=1,2,4 and 6. • Winbond proposed 3D Joint Interleaver, NBPSC=1, NI=4, NCBPS=54, Ncolumn=18 Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  27. PART-II: Circulation Transmission Transmission Options: Circular Spatial Multiplexing (CSMX) Circular Space-Time Alamouti (CALA) Circulation Options: (C) OFDM Symbol Based Circulation (S_BC) (D) Sub-carrier Based Circulation (Sub_BC) NOTE: The same proposed 3D Joint Interleaver is applied for all above options. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  28. Why Circulation? • Circulation is one simple way to achieve all available diversities including space, frequency, and time. When Circulation? • Always. Especially when transmitting NOFDM (M) at the same time from M TX antennas. How Circulation? • Together with proposed 3D Joint Interleaver to explore all available diversities Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  29. Transmission Options (A) Circular Spatial Multiplexing (CSMX) Transmitting NOFDM (M) OFDM Symbols from M TX Antennas High throughputs if high SNR (B) Circular of Space-Time Alamouti Code (CALA) Simple to encode and decode Can be easily modified to be compatible with 11a/g Circular Alamouti is applied if more than two transmit antennas Circulation bases on two OFDM symbols to preserve orthogonality Definition:NOFDM (M)denotes a MIMO system transmits NOFDM OFDM symbols at the same time from M TX antennas Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  30. Circulation Options for CSMX Systems • (C) OFDM symbol-based circulation (S_BC) • Only NOFDM IFFTs are required • Only NOFDM TX Ant. are transmitting at the same time • (D) Subcarrier-based circulation (Sub_BC) • M IFFTs are required • All M TX Ant. are transmitting at the same time • Smaller size of interleaver than S_BC • Smaller processing delay than S_BC Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  31. Circulation Options for CALA Systems (NOFDM=2) • (C) OFDM symbol-based circulation (S_BC) • Only 2 IFFTs are required • Only 2 TX Ant. are transmitting at the same time • (D) Subcarrier-based circulation (Sub_BC) • M IFFTs are required • All M TX Ant. are transmitting at the same time • Smaller size of interleaver than S_BC • Smaller processing delay than S_BC Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  32. Example of a 2 (3) CSMX System Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  33. Example of a 2 (3) CALA System Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  34. Interleaver Outputs Before Circulation Transmission • S-BC (Ex. NI=6, NOFDM=2, M=3) (C) S_BC • Sub-BC (Ex. NI=2, NOFDM=2, M=3) (D) Sub_BC Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  35. Circulation Patterns for CSMX NPattern= =Number of circulation patterns for both S_BC and Sub_BC NI=NOFDMX NPattern for CSMX systems with S_BC NI=NOFDM for CSMX systems with Sub_BC NOTE: Bigger NI implies bigger HW size and longer decoding delay Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  36. Circulation Patterns for CALA NPattern= = Number of circulation patterns for both S_BC and Sub_BC NI=NOFDM x NPattern for CALA systems with S_BC NI=NOFDM for CALA systems with Sub_BC NOTE: Bigger NI implies bigger HW size and longer decoding delay Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  37. Sub-carrier mapping for Sub-BC Example: 2(3) MIMO System CSMX with Sub_BC Coded bits from FEC outputs 11a/g sub-carrier intrerleaving with 3-sub-carrier separation Circulation subcarriers Into all TX antennas Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  38. Example: 2(3) MIMO System CSMX with Sub_BC Coded bits from FEC outputs Adjacent bits have 3-subcarrier separations and circulate into M TX antennas. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  39. Example: 2(3) MIMO CSMX System with S_BC Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  40. Sub-BC and S-BC in 11n Channel B • Two schemes have similar performances. The interleaver size and decoding delay for Sub_BC is much smaller than S_BC. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  41. Sub-BC and S-BC in 11n Channel D • Two schemes have similar performances. The interleaver size and decoding delay for Sub_BC is much smaller than S_BC. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  42. RF and BB Related Issues • RF Total TX Power for 2(3) MIMO Systems • Assuming max power of each subcarrier is p, • Total power of OFDM symbol based circulation = 48 * p * 2 = P • Total power of modulated symbol based circulation= 32 * p * 3 = P • Power per antenna is P/2 for S_BC and P/3 for (Sub_BC) • Baseband (BB) hardware requires • Two IFFT/FFT for S_BC and Three for Sub_BC • NOTE: Bigger NI implies bigger HW size and longer decoding delay • Example: 2(4) CSMX requires NI=12 for S_BC and NI=2 for Sub_BC • If the power consumption of more active TX antennas at RF and more active IFFT/FFT at BB are acceptable, Sub_BC is recommended with minimal decoding delay and interleaver size. Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  43. Backward Compatibility with 11a/g • The proposed 3D Joint Intereleaver is backward compatible to the standardized 11g/11a 2D interleaver • If NI=1, the 3D joint interleaver becomes a 2D 11a/g interleaver • The 3D joint based on 3-subcarrier separation is backward compatible to 11a/g interleaver for all 8 11a data rates • Same 2nd permutation as 11a • Both proposed circulation options (C) S_BC and (D) Sub_BC are backward compatible with 11a interleaver • No circulation (Npattern=1) for option (C) S_B Circulation • The 3-subcarrier separation of consecutive mapped data of option (D) Sub_BC is the same as the 11a interleaver Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  44. High Throughput Requirement for 11n • The proposed 3D Joint Intereleaver can be implemented into a general MIMO systems with M TX antenna • The proposed 3D Joint interleaver supports all 8 data rates in 11a • Tables up to 4x4 MIMO systems are shown in this proposal. For a NOFDM (M) MIMO system with MNOFDM=1,2,…,6,… Size of proposed 3D Joint Interleaver=NI= NOFDM x Example: M=4, data rate of a 4(4) CSMX system is Mx54=216 Mbps The proposed interleaver is a 4x16x18 3D interleaver (NI=4) • For a general NOFDM (M) MIMO system, the proposed 3D Joint interleaver can support data rates up to Mx54 Mbps in 20MHz bandwidth, M is any integer Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  45. Conclusions • Proposed 3D Joint Interleaver which intereleaves adjacent FEC coded bits into all available diversities in space, frequency, and time is recommended. • Proposed 3D Joint Interleaver is backward compatible with 11a/g standard interleaver. • Proposed OFDM symbol based circulation and sub-carrier based circulation can be applied in all MIMO mode with arbitrary TX antennas, and transmission schemes (CSMX,CALA). • Proposed S_BC and Sub_BC is backward compatible to 11a/g. • Proposed Sub_BC with minimal decoding delay is recommended Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  46. PART-III: Coding Rates Selection and MIMO Tables Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  47. Code rate selection • 11a selection • 6, 9, 12, 18, 24, 36, 48, 54 Mbps • Two problems • 9 Mbps (BPSK, 3/4) performs bad. • 48 and 54 Mbps is only 6 Mbps difference. • Suggestion • Introducing new low code rate • Rate 1/3 is generated by repetition of the rate 1/2 coded bits (next page) • 9 Mbps (BPSK, 3/4)  8Mbps (QPSK, 1/3) • Introducing new puncturing to increase the max. rate. • 7/8 by puncturing pattern (1111010, 1000101) • 54 Mbps  63 Mbps Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  48. Generate Rate 1/3 from Rate 1/2 64 coded bits • To decrease the coding rate from 1/2 to 1/3 • Two possible ways • New optimal code: (133, 145, 175) dfree=15 • New Viterbi decoder is required  Not recommended • By repetition every other coded bit: dfree=15 • Same Viterbi decoder (mother code rate=½) can be used • Repetition method is used for simulations Rate=1/2 Rate=1/3 Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  49. Code rate selection • Consistent decrease the rates (24% - 33%) by introducing 7/8 rate • 9 Mbps is replaced by 8 Mbps. 15 12 12 6 6 4 2 Jeng-Hong Chen, Pansop Kim, Winbond Electronics

  50. Code rate selection • Channel D, half lambda • New selection of rates provides more smooth curves, higher data rate Jeng-Hong Chen, Pansop Kim, Winbond Electronics

More Related