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Partial Proposal for TGn

Partial Proposal for TGn. Takashi Fukagawa, et al fukagawa.takashi@jp.panasonic.com Panasonic. Overview. Panasonic Requirements for TGn MAC Proposal MAC Aggregation Reduced Inter-frame Spaces (IFSs) PHY Proposal Scattered & Staggered Pilot Subcarriers

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Partial Proposal for TGn

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  1. Partial Proposal for TGn Takashi Fukagawa, et al fukagawa.takashi@jp.panasonic.com Panasonic Panasonic

  2. Overview • Panasonic Requirements for TGn • MAC Proposal • MAC Aggregation • Reduced Inter-frame Spaces (IFSs) • PHY Proposal • Scattered & Staggered Pilot Subcarriers • Varying Interleave Patterns (VIP) MIMO Panasonic

  3. Panasonic Requirements • Panasonic’s main area of focus for TGn is for home use • AV data streams • VoIP, remote control Panasonic

  4. Panasonic Requirements contd. • Required MAC throughputs of 80Mbps for AV streaming applications • Home environments • Varying channel conditions (LOS/NLOS included) • Lower throughputs required for handheld eqpt in hotspot environments • TGn proposals should provide QoS support for • Long packets (eg: AV streaming) • Short packets (eg: VoIP) Panasonic

  5. Candidate Solutions for TGn • MAC • Reuse of .11e QoS mechanisms • Improved medium utilization • Aggregated data frames • Reduced access overheads • MIMO OFDM PHY • Reuse of .11a modulation schemes • 2x2 and 3x3 antenna configurations • Good performance in different conditions • New pilot structure for improved channel estimation • New interleaving scheme for improved performance Panasonic

  6. MAC Panasonic

  7. MAC Medium Utilization • Effective medium utilization may be improved by: • Increasing proportion of time used for data transmission • Decreasing Backoffs, Deferrals and Overhead transmissions Panasonic

  8. Frame Aggregation - Features • Proposed aggregation is purely MAC based • No change of interface to upper-layers • Supports both pt. to pt. and pt. to multi-pt. transmission • Uses .11e Block ACK for efficient acknowledgement of compartment MSDUs • New Frame format consisting of: • Enhanced MAC Header • Frame body consisting of aggregated component MSDUs • Aggregated frame: • Frame Type: Extended • Subtype: Aggregated Data Panasonic

  9. MAC Aggregation – Frame Format (1/2) • New “Aggregated Data” frame • MAC Header consists of: • Aggregation Control – defines the number of MSDU compartments and their lengths • Header FCS – for added protection • Frame Body consists of: • Individual Compartment MSDUs, each having legacy header & FCS Panasonic

  10. MAC Aggregation – Frame Format (2/2) • Component MSDUs placed in MSDU Compartments of the Frame body of the Aggregated Data frame • Header of the component MSDUs preserved • facilitates point to multi-point transmission • allows for re-routing in multihop (L2) scenarios • Each Compartment MSDU retains its FCS • allows for error detection of individual compartments Panasonic

  11. MAC Aggregation – Technique • On obtaining a TXOP, Tx may construct an aggregated data frame from MSDUs in its queue, • .11e Block ACK is used to facilitate acknowledgement and selective retransmission in the case of aggregated compartment MSDUs • STAs receiving an aggregated frame sequentially decode the MAC header and compartment MSDUs and pass to the MAC layer • MAC performs accept/reject and further processing after address matching of the compartment MSDUs Panasonic

  12. MAC Aggregation – Performance • Assumptions: • Scenario 16, Error Free Channel • TXOP: 4ms, # of MSDUs in Burst/Aggregate: 5, Max MPDU size: 8KByte • Observations: • MAC aggregation scales well with increasing PHY rates • Legacy (11e) performance reaches a saturation • 110 Mbps MAC throughput @ PHY rate:126Mbps & 1500Byte MSDUs Panasonic

  13. Reduced Inter-frame Spaces – Motivation (1/2) • Idle-time (backoffs & IFS) constitute a large overhead to frame transmission • Idle-time overheads are particularly dominant for small packets (eg: VoIP) • Based on measurements of today’s WLAN traffic, majority of WLAN packets < 64B Ref: 11-03/567r1/Samsung et al Panasonic

  14. Reduced Inter-frame Spaces – Motivation (2/2) • While proposed aggregation technique is one way of improving effective medium utilization, not all frames can be aggregated • Upper-layer protocol control packets • Inelastically bounded traffic (realtime/interactive – e.g.: VoIP, Video) • Proposed IFS Reduction technique reduces the physical length of the IFS, realizing a higher medium utilization efficiency and consequently throughput Panasonic

  15. Reduced Inter-frame Spaces – Technique (1/2) • PHY signalling (and/or MAC Processing) may be used to determine whether a STA: • expects a response to its current frame • expects to retain hold of the medium for a continuation frame • TGn is expected to have STAs with incompatible/ optional modes (eg: 3x3) in the same network, • PHY signalling is done using a single-bit field in the PLCP header • RCE field – Response/Continuation Expected Panasonic

  16. Reduced Inter-frame Spaces – Technique (2/2) • New IFSs may be defined: • short PIFS (sPIFS) – IFS used by the AP to preempt access to the medium when a frame is transmitted to which there is no response/continuation expected • short DIFS (sDIFS) – IFS used by stations attempting to access the medium when a frame is transmitted to which there is no response/continuation expected Panasonic

  17. Examples of Frame Transfer sDIFS chosen by other stations based on RCE = 0 in ACK sDIFS/sPIFS chosen by STAs based on expiring NAV (implying no continuation) and ACKtimeout Panasonic

  18. Reduced Inter-frame Spaces – Performance Assumptions – Scenario 16, Error Free Channel • No ACK (1500Byte): 6.2% improvement • ACK (1500Byte): 4.8% improvement • No ACK (150Byte): 10.7% improvement • ACK (150Byte): 7.2% improvement Panasonic

  19. PHY Panasonic

  20. Scattered & Staggered Pilot Subcarriers - Motivation • Legacy continuous pilot subcarriers are not suitable for TGn: • In a selective fading environment, received power of particular subcarriers may be very low. • In MIMO transmission, when residual frequency offset between each branch or phase noise exists, receiver performance will deteriorate. Panasonic

  21. Scattered & Staggered Pilot Subcarriers – Features • Proposed pilot scheme improves receiver performance • Four pilot subcarriers in each OFDM symbol • Pilot positions are scattered in every OFDM symbol • Robustness in a frequency selective fading environment • Pilot insertion is staggered in OFDM symbols from different transmit branches • Enables phase offset estimation on each path • Results show that proposed pilot scheme is effective in canceling out the residual frequency offsets and compensating for phase noise Panasonic

  22. Proposed Pilot Subcarrier Allocation (1/3) Scattered Pilot subcarrier position, PCpos(n), is defined as follows: where PCoffset = -26, -13, 1, 14 n = 1 ... Nsym_per_stream (DATA symbol # of a transmit stream) Ntx is transmit antenna number Staggered Pilot signal insertion pattern, PCpat(n,m), is defined as follows: where n = 1... Nsym_per_stream (DATA symbol # of a transmit stream) m = 1...Ntx (transmit antenna number) Panasonic

  23. Proposed Pilot Subcarrier Allocation (2/3) 2x2 MIMO transmission case (periodicity of 26 DATA symbols) Blue: Pilot signal Gray: Null signal TX1 data symbols TX2 data symbols symbol subcarrier Panasonic

  24. Proposed Pilot Subcarrier Allocation (3/3) 3x3 MIMO transmission case (periodicity of 39 DATA symbols) Blue: Pilot signal Gray: Null signal TX1 data symbols TX3 data symbols TX2 data symbols symbol subcarrier Panasonic

  25. freq freq TX2 TX1 sym sym PC Extract RX1 CFE FFE FFT Demod Channel Separation Ch. Est. RX2 CFE FFE FFT Demod Pilot carrier PC Extract Null carrier Update h21 with these pilot carriers freq RX1 Update h11 with these pilot carriers sym Null carrier Pilot carrier h11 Update h22 with these pilot carriers TX1 RX1 h12 freq h21 Update h12 with these pilot carriers TX2 RX2 RX2 h22 Proposed Pilot Subcarrier - Usage • Before separating the MIMO streams, pilot signals are extracted in order to update channel information of each transmission path Panasonic

  26. Proposed Pilot Subcarrier – Simulation Conditions Frame Format • Tx Scheme: 2x2 MIMO – 16 & 64QAM (Conv Code r = ¾) • Antenna Spacing: 0.5λ • Frequency Offset: 0, +40, -40ppm • Phase Noise: -100dbc at 250kHz (IM4) • Channel Equalization: MMSE STS LTS LTS SIG HTSIG LTS LTS D1 TX1 STS LTS LTS SIG HTSIG LTS -LTS D2 TX2 Coarse Frequency Estimation; Coarse Timing estimation Fine Frequency Estimation; Fine Timing Estimation; Legacy Channel Estimation MIMO Channel Estimation Phase compensation of estimated channel coefficients w/ proposed pilot subcarrier scheme Panasonic

  27. Proposed Pilot Subcarrier – Performance (1/3) • Channel B - NLOS 2x2 MIMO, 3/4 16QAM 2x2 MIMO, 3/4 64QAM Panasonic

  28. Proposed Pilot Subcarrier – Performance (2/3) • Channel D - NLOS 2x2 MIMO, 3/4 16QAM 2x2 MIMO, 3/4 64QAM Panasonic

  29. Proposed Pilot Subcarrier – Performance (3/3) • Channel E - NLOS 2x2 MIMO, 3/4 16QAM 2x2 MIMO, 3/4 64QAM Panasonic

  30. Varying Interleave Patterns – Motivation • Spatial MUX may be used for high rate transmissions • Assumption for best performance – uncorrelated channels • However in real deployments, there may be channel correlation, detracting from the benefits of spatial MUX • Viterbi decoding introduces burst errors • Iterative decoding helps improve BER performance Panasonic

  31. Convolutional Encoder Interleaver-A Mapping (BPSK, QPSK, 16QAM, 64QAM) RF Processor RF Processor Convolutional Encoder Interleaver-B Varying Interleave Patterns – Approach • Proposed enhancement • Reduce correlation between different spatial streams through the use of different interleavers on different streams • Use of different interleavers, when combined with iterative decoding also reduces the burst error effects that are introduced during Viterbi decoding VIP(Varying Interleave Pattern) Panasonic

  32. Iterative Decoding with Signal Point Reduction Decoding process of various channels are mutually dependent An example of how decision of Channel B constrains the decision on Channel A Panasonic

  33. Varying Interleave Patterns – An Example Panasonic

  34. Iterative Decoding with Signal Point Reduction VIP – Example of Iterative Decoder Panasonic

  35. VIP – Performance (1/4) Simulation Conditions • Channel: B-NLOS • 2x2 MIMO OFDM w/ VIP • Packet Size: 1000Byte • # of Packets: 10000 • Channel Equalization: MMSE • Interleaver: 6 OFDM-symbols Panasonic

  36. VIP – Performance (2/4) Simulation Conditions • Channel: D-NLOS • 2x2 MIMO OFDM w/ VIP • Packet Size: 1000Byte • # of Packets: 10000 • Channel Equalization: MMSE • Interleaver: 6 OFDM-symbols Panasonic

  37. VIP – Performance (3/4) Simulation Conditions • Channel: E-NLOS • 2x2 MIMO OFDM w/ VIP • Packet Size: 1000Byte • # of Packets: 10000 • Channel Equalization: MMSE • Interleaver: 6 OFDM-symbols Panasonic

  38. VIP – Performance (4/4) Simulation Conditions • Channel: D-LOS • 2x2 MIMO OFDM w/ VIP • Packet Size: 1000Byte • # of Packets: 10000 • Channel Equalization: MMSE • Interleaver: 6 OFDM-symbols Panasonic

  39. Varying Interleave Patterns – Summary • Results show an improvement with VIP in both LOS and NLOS environments • It is possible to implement VIP in several ways • Single encoder/interleaver implementation also possible (see Annex A1) • VIP receiver implementation is vendor dependent • enhanced architectures can realize higher gains Panasonic

  40. Annex Panasonic

  41. A1 – VIP – Single Interleaver Architecture Mapping RF Processor Convolutional Encoder Interleaver RF Processor Varying Interleave Patterns Panasonic

  42. A2 – Proposed Pilot Subcarrier - Performance Residual frequency offset cancellation - D-NLOS, 2x2 MIMO ¾ 64QAM TX1-TX2 phase noise : common RX1-RX2 phase noise : common TX1-TX2 phase noise : independent RX1-RX2 phase noise : independent Panasonic

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