Performance Evaluation of MIMO midamble design for IEEE 802.16m IEEE 802.16 Presentation Submission...

Performance Evaluation of MIMO midamble design for IEEE 802.16m

IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number:

IEEE C802.16m-09/1237Date Submitted:

2009-01-07Source:

Jerry Pi, Jiann-An Tsai, Bruno Clerkx, David Mazzarese [email protected] Samsung Electronics

Venue:Re : 802.16m amendment working document

Base Contribution:IEEE C802.16m-09/1237

Purpose:To discuss and adopt the proposed text in the revision of the 802.16m SDD

Notice:This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein.

Release:The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor

also acknowledges and accepts that this contribution may be made public by IEEE 802.16.

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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.

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Background

• AWD, section 15.3.5.4.2– “MIMO midamble is used for PMI selection in closed loop

MIMO. For OL MIMO, midamble can be used to calculate CQI. The midamble signal occupies the one OFDMA symbol in a DL sub-frame. For the type-1 subframe case, the remaining 5 consecutive symbols form a type-3 subframe. For the type-2 subframe case, the remaining 6 consecutive symbols form a type-1 subframe.”

• AWD text proposal for detailed MIMO midamble design is provided in C80216m-09_1236

• This contribution provides performance evaluation of the MIMO midamble design as in C80216m-09_1236

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Time domain interlacing• Time domain interlacing enables collision avoidance

of midamble among neighboring cells– Allow power boosting of midamble to improve channel

estimation performance• The subframe index for MIMO midamble is explicitly

signaled• The OFDM symbol index within the subframe is

derived from the Cell_ID– MIMO midamble is transmitted on the first OFDM

symbol of a subframe if the Cell_ID is even– MIMO midamble is transmitted on the last OFDM

symbol of a subframe if the Cell_ID is odd

3

Frequency domain placement• Cell-specific frequency domain shift applied

– To further minimize collision of midamble among neighboring cells• Terminology

– i : antenna index, i = 1, …, NT

– j: subcarrier index, j = 0, 1, …, 17– k: Cell_ID– n: Frame index

• In frame n, midamble for antenna i is transmitted on subcarrier j in cell k – if and only if the following two conditions are met

• mod(j + k/2, 9) 0• mod(mod(j + k/2, 9) + 4 mod(n, 2) – 1, 8) = BRO(i – 1 , 3)

– BRO(x, 3) is the 3-bit bit-reversal value of x• Subcarriers not used for midamble transmission are reserved as null

subcarriers– The unused power can be allocated to midamble for power boosting– Null subcarriers can be used for interference estimation

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Properties of the midamble• Up to 16 time-domain interlaces to reduce midamble collision• Midamble is transmitted once every frame in the same OFDM symbol• Midamble for each antenna is regularly spaced in frequency (1 in every 9

subcarriers) A single midamble channel estimator for all antennas in 2, 4, or 8 Tx cases

• Midamble in adjacent frames are staggered – Increase the frequency sampling rate to 16 frequency samples per subband

per antenna– Improve channel estimation performance by 2-D MMSE channel estimation

across frames• Midamble among neighboring cells are shifted in frequency

– Further minimize midamble collision– Particularly beneficial in TDD system with limited DL subframes for midamble

transmission• Enable channel estimation to benefit from power boosting

– 2Tx : 6.5dB, 4Tx : 3.5dB, 8Tx : 0.5dB– Further midamble boosting possible if low PAPR sequences are designed

5

MIMO midamble for 2Tx systems

6

X

2

1

X

2

1X

X

X

X

X

X

X

X

X

X

X

X

X

2

1

X

2

1X

X

X

X

X

X

X

XX

X

X

X

18 c

ontig

uous

sub

carr

iers

6 OFDM symbols 6 OFDM symbols

X Null sub-carriers

1

2

Midamble Pilot for Antenna 1


Data or control sub-carriers

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

SF0 SF1 SF2 SF3 SF4 SF5 SF6 SF7

Frame 0 Frame 1

1 subframe



7

X

2

1

X

2

1X

X

X

X

X

X

X

X

3

3

4

4

X

2

1

X

2

1X

X

X

X

X

X

X

X

3

4

3

4

18 c

ontig

uous

sub

carr

iers


X Null sub-carriers

1

2

3

4






0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17


Frame 0 Frame 1

1 subframe



8

2

1

2

1

X

X

3

3

4

4

5

7

7

5

6

8

6

8

X

2

1

3

48

7

5

6

X

2

1

3

48

7

5

6

18 c

ontig

uous

sub

carr

iers


X Null sub-carriers

1

2

3

4

5

6

7

8










0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17


Frame 0 Frame 1

1 subframe


Performance Evaluation• Comparison

– Fixed subframe transmission vs. non-fixed subframe transmission– Symbol interlacing vs. Non Symbol interlacing

• Simulation configuration– System topology: 19 cells / 57 sectors wrap-around– MIMO configuration: (2, 4, or 8) Tx, 2Rx– System bandwidth: 10MHz– Subband size: 4 PRUs– CQI feedback: once per 5ms (all sub-bands)– Rank adaptation: ON– Receiver: LMMSE– Scheduling: Proportional Fair

• Metric:– System throughput– 5-percentile user throughput

9

10

SLS Results 8TX MidambleRelative Cell Edge Throughput (%)

Relative Sector Throughput (%)

Full loaded(Non Fixed subframe TX Only)

100 100

50% loaded(Non Fixed subframe TX Only)

112 107


115 110

50% load(Symbol Interlacing Only)

107 103

50% loaded(Non Fixed subframe TX+Symbol Interlacing)

118 108

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SLS Results 4TX Midamble

Relative Cell Edge Throughput (%)



100 100


111 106

50% loaded(Symbol Interlacing Only)

107 103

12

SLS Results 2TX Midamble

Relative Cell Edge Throughput (%)



100 100


107 104

50% loaded(Symbol Interlacing Only)

103 102

Summary

• Both schemes of non-fixed subframe transmission and symbol interlacing provide significant system gain over fixed subframe/fixed symbol transmission

• As shown, gain is particularly significant for light-loaded system

• As observed, the improvement on cell edge throughput is substantial as compared to sector throughput

• Recommendation– TGm adopt the text proposal in C80216m-09_1236 into

AWD

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Performance Evaluation of MIMO midamble design for IEEE 802.16m IEEE 802.16 Presentation Submission...

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