1. Partial Proposal for TGn
2019/5/29
doc.: IEEE /0013r0
September 2004
Partial Proposal for TGn
Takashi Fukagawa, et al
Panasonic
Panasonic
Realtek

2. Overview Panasonic Requirements for TGn MAC Proposal PHY Proposal
September 2004
Overview
Panasonic Requirements for TGn
MAC Proposal
MAC Aggregation
Reduced Inter-frame Spaces (IFSs)
PHY Proposal
Scattered & Staggered Pilot Subcarriers
Varied Interleave Patterns (VIP) MIMO
Panasonic

3. Panasonic Requirements
September 2004
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.
September 2004
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
September 2004
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. September 2004
MAC
Panasonic

7. MAC Medium Utilization
September 2004
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
September 2004
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)
September 2004
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)
September 2004
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
September 2004
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
September 2004
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 PHY rate:126Mbps & 1500Byte MSDUs
Panasonic

13. Reduced Inter-frame Spaces – Motivation (1/2)
September 2004
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)
September 2004
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)
September 2004
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)
September 2004
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
September 2004
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
September 2004
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. September 2004
PHY
Panasonic

20. Scattered & Staggered Pilot Subcarriers - Motivation
September 2004
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
September 2004
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)
September 2004
Proposed Pilot Subcarrier Allocation (1/3)
Scattered Pilot subcarrier position, PCpos(n), is defined as follows:
where PCoffset = -26, -13, 1, 14
n = 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)
September 2004
Proposed Pilot Subcarrier Allocation (2/3)
2x2 MIMO transmission case (periodicity of 26 DATA symbols)
Blue: Pilot signal
Gray: Null signal
TX1 data symbols
symbol
TX2 data symbols
subcarrier
Panasonic

24. Proposed Pilot Subcarrier Allocation (3/3)
September 2004
Proposed Pilot Subcarrier Allocation (3/3)
3x3 MIMO transmission case (periodicity of 39 DATA symbols)
Blue: Pilot signal
Gray: Null signal
TX1 data symbols
symbol
TX2 data symbols
TX3 data symbols
subcarrier
Panasonic

25. Proposed Pilot Subcarrier - Usage
September 2004
Proposed Pilot Subcarrier - Usage
Before separating the MIMO streams, pilot signals are extracted in order to update channel information of each transmission path
h11
h12
h21
h22
TX2
TX1
RX2
RX1
sym
freq
Update h11 with
these pilot carriers
Update h21 with
Update h22 with
Update h12 with
Null carrier
Pilot carrier
CFE
Ch. Est.
FFE
FFT
Channel
Separation
Demod
PC Extract
Panasonic

26. Proposed Pilot Subcarrier – Simulation Conditions
September 2004
Proposed Pilot Subcarrier – Simulation Conditions
Frame Format
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
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
Panasonic

27. Proposed Pilot Subcarrier – Performance (1/3)
September 2004
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)
September 2004
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)
September 2004
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
September 2004
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. Varying Interleave Patterns – Approach
September 2004
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
In LDPC, interleaver is incorporated into the encoder
VIP can be achieved through the use of different LDPC codes on different streams
Convolutional
Encoder
Mapping
(BPSK, QPSK,
16QAM, 64QAM)
Interleaver-A
Interleaver-B RF
Processor
VIP(Varying Interleave Pattern)
Panasonic

32. Iterative Decoding with Signal Point Reduction
September 2004
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
September 2004
Varying Interleave Patterns – An Example
Panasonic

34. VIP – Example of Iterative Decoder
September 2004
VIP – Example of Iterative Decoder
Iterative Decoding with Signal Point Reduction
Panasonic

35. VIP – Performance (1/4) Simulation Conditions Channel: B-NLOS
September 2004
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
September 2004
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
September 2004
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
September 2004
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
September 2004
Varying Interleave Patterns – Summary
Results show an improvement with VIP in both LOS and NLOS environments
VIP can be implemented with both convolutional and LDPC codes
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. September 2004
Annex
Panasonic

41. A1 – VIP – Single Interleaver Architecture
September 2004
A1 – VIP – Single Interleaver Architecture
Convolutional
Encoder
Interleaver RF
Processor
Mapping
Varying Interleave Patterns
Panasonic