Doc.: IEEE 802.11-04/0929r0 Submission August 2004 Patrik Eriksson et. al., WaveBreaker ABSlide 1 A...

August 2004

Patrik Eriksson et. al., WaveBreaker AB

Slide 1

doc.: IEEE 802.11-04/0929r0

Submission

A “High Throughput” Partial Proposal

Patrik Eriksson, Anders Edman, Christian KarkWavebreaker AB, Norrkoping, Sweden

[email protected]

Scott Leyonhjelm (Editor), Mike Faulkner, Melvyn Pereira,Jason Gao,Aaron Reid,Tan Ying,Vasantha Crabb.

Australian Telecommunication Co-operative Research Centre, Melbourne, Australia.

[email protected]

August 2004


Slide 2

doc.: IEEE 802.11-04/0929r0

Submission

Presentation Outline

• Proposal Executive Summary• Proposed PHY Design • Proposed Frame Format • Comparison Criteria• Conclusion

August 2004


Slide 3

doc.: IEEE 802.11-04/0929r0

Submission

Proposal Executive Summary• Fully backward compatible with 802.11a/g

– 20MHz with 802.11a/g mask– All enhancements are simple extensions to 11a/g OFDM structure.– STS and LTS sequences are used in conjunction with progressive cyclic

delay per antenna• Higher Data Throughput due to combination of PHY technologies

– MIMO-OFDM - Spatial Multiplexing, up to 3 transmit antennas (mandatory), 4 antennas (optional)

– Fast Adaptive Loading - Rate adaptation on a per layer (mandatory) or per a subgroup (optional) level

– Higher order modulation - 256QAM• Higher Data Throughput due to combination of MAC enhancements

– Shorter SIFS, down to 8 us.– Frames with NO short and long training sequences– Frame aggregation

• Minimising Hardware Complexity– Frame format designed to increase available time for inverting channel

estimate.

August 2004


Slide 4

doc.: IEEE 802.11-04/0929r0

Submission


• Proposal Executive Summary• Proposed PHY Design• Proposed Frame Format • Comparison Criteria• Conclusion

August 2004


Slide 5

doc.: IEEE 802.11-04/0929r0

Submission

Proposed PHY Design

Parallel Spatial Multiplexing Architecture• Scalable architecture - supports up to 3 (mandatory) or 4 (optional) antennas • The mapping function expanded to include 256QAM• Cyclic Delay is implemented with a progressive 1 sample delay /per antenna• Adaptive Loading (Rate Adaptation)

Demux

Data Bits

Scramble

Encode

Encode

Encode

Encode Punct

Punct

Punct

Punct

Inter. Map

Inter.

Inter.

Inter.

FFT CP Cyclic Delay

To DACs

Map FFT CP Cyclic Delay



Adaptive Loading Info from Sig3 Symbol ‘CSI’ field

Mux

STS and LTS Preambles

Mux

Pilots

August 2004


Slide 6

doc.: IEEE 802.11-04/0929r0

Submission

Proposed PHY Design

• Adaptive Loading (Rate Adaptation)– The STA determines the maximum rate per layer (mandatory) or subgroup of

carriers (optional) and this is communicated back to the AP, and vice-versa. – Adapts the Puncturing and Constellation Mapping on a layer basis.– Adaptive rate can vary from 0Mbit/s through to 72Mbits/s on a per layer basis.– Fast Adaptation handled at PHY layer

Punct/ MapData

Bits

Tx

Channel Estimation

Rx

Data Bits

Forward Link

SNR (Link Margin/layer)

Calculate Maximum Rate Possible on a per layer basis

Decode Sig3 Symbol ‘Rev

CSI’ field

Reverse Link Encode Sig3

Symbol ‘Rev CSI’ field

August 2004


Slide 7

doc.: IEEE 802.11-04/0929r0

Submission

Proposed Frame FormatPHY Digital complexity – N layers vs 1 layer (11a)• ~N times complexity for most baseband processing blocks (e.g. filter, FFT, frequency correction,

mapping, demapping, decoding) – energy per bit for these parts remain constant compared to 11a.

• >N times complexity for Channel Estimation & Equalisation: – approx the same as for FFT b;lock for up to 3*3 MIMO system.– The increased length of payload, and transmission of frames without preambles keep the power

cost for this operation at a reasonable level. – Sig3 symbol placement between last preamble and data increases available time for

computation with one symbol period. This reduces the required complexity of the logic for this function.

Analog Area and Power – N layers vs 1 layer (11a)• <N times Area and Power consumption as some units are reused for all channels

Summary for N=3;• ~4 times 11a for Digital baseband computational complexity • ~2.5 times 11a for Analog area and power consumption.

August 2004


Slide 8

doc.: IEEE 802.11-04/0929r0

Submission


• Proposal Executive Summary• Proposed PHY Design • Proposed Frame Format • Comparison Criteria• Conclusion

August 2004


Slide 9

doc.: IEEE 802.11-04/0929r0

Submission

Proposed Frame Format3 new MIMO frame types are proposed:• MIMO - Type 1 frames with Training. Note that the STS, LTS and Sig2 sequence can be

received by legacy equipment. • MIMO - Type 2 frames without Training. Note that time, frequency & channel tracking

algorithms will be required.• MIMO – Type 3 frames with Training used only in 5GHz band.

802.11n MIMO - Type 1


STS1 LTS1 Sig2 LTS1a LTS1b LTS1c




Sig3

Sig3

Sig3

Sig3

D1

D1

D1

D1

D2

D2

D2

D2

Dn

Dn

Dn

Dn

Sig3

Sig3

Sig3

Sig3

D1

D1

D1

D1

D2

D2

D2

D2

Dn

Dn

Dn

Dn


Sig2 LTS1a LTS1b LTS1c




Sig3

Sig3

Sig3

Sig3

D1

D1

D1

D1

D2

D2

D2

D2

STS1 LTS1 Sig

STS2 LTS2 Sig

STS3 LTS3 Sig

STS4 LTS4 Sig

D1

D1

D1

D1

D2

D2

D2

D2

Dn

Dn

Dn

Dn

802.11a OFDM Frame format

802.11g DSSS Frame format

802.11g OFDM Frame format

STS LTS Sig D1 D2

Preamble Head

STS LTS Sig D1 D2

D1 D2

Ext

Note: Sig3 and Data Symbols can be turned off.

August 2004


Slide 10

doc.: IEEE 802.11-04/0929r0

Submission

Proposed Frame Format• Type 3 only – Single MIMO frame transmission

– MIMO frames appended to a 11a/g frame => backward compatible with 11a/g frames– contains MIMO training and Data – Sig2 symbol – Indicates MIMO setup– Sig3 symbol – indicates MIMO rates being used and length of MIMO transmission.

• Type 3,2 & 1 –RTS/CTS frame transfer– Type 3

• Training required for initially establishing Adaptive Loading• Sig3 symbol – indicates Adaptive Loading rates & Data Length• <Training><Sig3><Data> - increases available time for inverting channel estimate.

– Type 2 - Data carrying with no Training Sequence– Type 1 - backward compatible with 11a/g frames, used for

• Used on a retransmission• Re-synchronising during a RTS/CTS transmission, and• Extending the duration of the transmission (CTS to self)

• SIFS an take a value between 8 to 16us– receiver must be ready to receive after 8us but a transmitter is allowed to wait up to 16us

before starting

August 2004


Slide 11

doc.: IEEE 802.11-04/0929r0

Submission

Proposed Frame FormatTo Achieve Goodput of >100Mbps for PER 10%, PHY average rate =144Mbps• Single Frame Transmission Mode

– Packet Size = 5.5kbyte packet • RTS/CTS Transmission Mode

– Packet Size > 2kbyte– Tranmission Length = 10kbyte

• Frame Aggregation– Increases MAC efficiency– Proposed max. 16kbyte packet

August 2004


Slide 12

doc.: IEEE 802.11-04/0929r0

Submission

Proposed Frame FormatImplementation Details of the Frame Format proposal• Channel Models in 802.11n are slowly moving (low Doppler)

– Channel sufficiently stable for at least 50 symbols (MSE <-35dB)– Channel F with 40kph Doppler Component

• Type 2 packets have NO training sequences– Initial ST/LTS sets up Timing grid – Transmissions start at 4us intervals – Receiver uses fast power detection

algorithms to determine if packet (sig3 symbol) is present or not

– Frequency offset and sampling time offsets must flywheel over non-transmission periods

• Implementation Requirements– Time, frequency offsets tracked via 4

pilots– Channel Tracking

August 2004


Slide 13

doc.: IEEE 802.11-04/0929r0

Submission



August 2004


Slide 14

doc.: IEEE 802.11-04/0929r0

Submission

Comparison Criteria• CC51- mandatory

– BPSK thru to 256QAM – Rates 0 thru to 72Mbps per layer– 1,2 or 3 transmit antennas

• CC42- The short and long training sequences are the same as the 802.11a/g defined training sequences with the following modifications:– Both the STS and LTS sequences have a progressive cyclic delay

of 1 sample per antenna applied, see also Appendix A, Section 7.1– The LTS sequences are also phase loaded on a per antenna basis

August 2004


Slide 15

doc.: IEEE 802.11-04/0929r0

Submission

Comparison Criteria• CC58

– RTS/CTS frame transmission mode achieves a goodput of more than 100Mbps, – The single frame transmission mode achieves a maximum goodput of 80Mbps

when the average PHY data rate is 288Mbps !. To get >100Mbps• With frame aggregation a 5.5kbyte packet size transmitted at a average PHY data rate of

144Mbps • With channel bonding (optional) the average PHY data rate is increased by a factor 1.8

Configuration Average PHY Data rate to achieve

Goodput >100Mbps

bps/Hz

Single Frame Mode N.A. N.A. 2*2 MIMO, Channel B RTS/CTS Mode 144Mbps 7.2 Single Frame Mode N.A. N.A. 3*3 MIMO, Channel B RTS/CTS Mode 144-216Mbps 7.2-10.8 Single Frame Mode N.A. N.A. 4*4 MIMO, Channel B

(Optional) RTS/CTS Mode 144-288Mbps 7.2-14.4 Single Frame Mode N.A. N.A. 3*3 MIMO, Channel D RTS/CTS Mode 144-216Mbps 7.2-10.8 Single Frame Mode N.A. N.A. 4*4 MIMO, Channel D

(Optional) RTS/CTS Mode 144-288Mbps 7.2-14.4

August 2004


Slide 16

doc.: IEEE 802.11-04/0929r0

Submission

Comparison Criteria• CC59 –AWGN Channel

– Observation : the capacity is a linear function of the number of transmit antennas.

– Each layer had the same rate, even if the adaptive loading algorithm was switched on.

August 2004


Slide 17

doc.: IEEE 802.11-04/0929r0

Submission

Comparison criteria• CC80- The modifications required for a legacy

802.11 PHY are;– The scalable architecture supports up to 3 (mandatory)

or 4 (optional) antennas – The adaptive loading modifies the puncturing and

Constellation Mapping on a layer basis, – Include 256 QAM– Cyclic Delay implemented with a progressive 1 sample

delay /per antenna– The LTS preambles are modified versions of the

802.11a/g defined sequences

August 2004


Slide 18

doc.: IEEE 802.11-04/0929r0

Submission



August 2004


Slide 19

doc.: IEEE 802.11-04/0929r0

Submission

Conclusion – Key Features

• Higher Data Throughput due to combination of PHY technologies– MIMO-OFDM – 1 to 3 antennas using Spatial

Multiplexing – Rate Adaptation– Higher order modulation – 256QAM

• Higher Data Throughput due to combination of MAC enhancements– Shorter SIFS - down to 8 us.– Frames with NO short and long training sequences– Frame aggregation – up to 16kbytes/packet

August 2004


Slide 20

doc.: IEEE 802.11-04/0929r0

Submission

Conclusion• Backward Compatibility is ensured by

– Operation within a 20MHz bandwidth with the same 802.11a/g spectral mask.

– Single and RTS/CTS frame transmission modes are fully compatible with legacy 802.11a/g devices.

• All Functional Requirements are met• Low Overhead Frame formats• 100Mbps Goodput Achieved when

– 20MHz and 2 transmit antennas– > 144Mbps Average PHY data rate – Rate Adaptation

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