1. Document Number: IEEE C80216m-09_2238r2 Date Submitted: 2009-11-17
CoFIP Pilot Structure
Document Number: IEEE C80216m-09_2238r2
Date Submitted:
Source:
Padmanabhan M S, Kiran Kuchi, J. Klutto Milleth, Sivakishore Voice:
CEWiT, India
Venue: Comments on P802.16m/D2 ( )
Base Contribution: None
Purpose: To discuss and adopt the proposed text in D3
To discuss in TGm for appropriate action. Notice:
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2. Collision Free Interlaced Pilots (CoFIP)

3. Outline
In Jeju it was agreed that CoFIP will be used for CDR. Details of CoFIP are TBD.
In this contribution details of CoFIP pilot structure are given
In 2253, 2-stream pilot-on-data is proposed.
Performance of both methods compared
CoFIP is shown to be more than dB better than 2-stream pilot-on-data using a low-complexity MMSE receiver
Proposed text

4. Proposed CoFIP P denotes pilot tone and 0 denotes null toneP P
Pilot pattern Set 0
Pilot pattern Set 1
Pilot pattern Set 2
P denotes pilot tone and 0 denotes null tone

5. Pilot structure proposed in S80216m-09_2253

6. Simulation setup 1
2Tx antenna – 2Rx antenna, one stream CDR transmission
Channel: Modified Ped B, 30 km/h
Thermal noise level is 30 dB below the power of the desired signal
QPSK ½ CTC , eight 18x6 PRUs forms a channel coding block.
2D-MMSE channel estimation. All estimation done within a PRU
Short PRBS pilot sequences (sequences with low cross-correlation) are used.
Interference profile: [ ]
Direct MMSE is used for demodulation
Interference covariance is estimated from 1) pilot tones and null tones for CoFIP 2) pilot tones for Interlaced pilot structure
Interference pilot knowledge is NOT used in the 2D-MMSE channel estimation. Additional channel est improvement feasible with using pilot knowledge in CE (approx 1.0 dB gains shown previously) 6

7. CoFIP outperforms pilot-on-data by over 2.0 dB

8. Goodput = (1 – bler)*(1- pilot overhead)
CoFIP outperforms Pilot-on-Data in goodput

9. Simulation setup 2
Interference profile at 0 dB SIR [ dB].
Direct and indirect MMSE are used for demodulation.
Thermal noise level is 10 dB below the power of one interferer.

10. CoFIP outperforms pilot-on-data by over 2.5 dB

11. Goodput = (1 – bler)*(1- pilot overhead)
CoFIP outperforms Pilot-on-Data in goodput

12. Conclusion
CoFIP outperforms pilot-on-data by over dB
Knowledge of interference pilot sequence is NOT used in CoFIP receiver
With interference pilot knowledge CoFIP which uses pilot-on-pilot collisions benefits
Pilot-on-data does not benefit from interferer pilot knowledge
The good put of CoFIP is much higher than pilot-on-data
CoFIP is suitable for CQI estimation in OL region using always ON pilot in select sub frames
Pilot-on-Data does not ensure proper CQI estimation
It fails to provide proper CQI if data tones are not transmitted in interfering cells
Adopt CoFIP in type-1 OL region

13. Proposed text
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 Section page 305 line 39
Type-1 OL MIMO region shall use Collision Free Interlaced Pilot (CoFIP) pattern.
Figure xxx shows the CoFIP pattern for AAI sub-frames consisting of 6 OFDM symbols. The index of the CoFIP PRU type used by a particular BS with Cell_ID=k is denoted by pk. The index of the pilot pattern set used by a particular BS with the Cell_ID=k is denoted by pk. The index of the pilot pattern set is determined by the Cell_ID according to the following equation: pk = mod(k,3).
For AAI sub-frames consisting of 7 OFDM symbols, the first OFDM symbol which contains pilot tones and null tones in each pilot pattern set shown in Figure xxx is added as the 7th symbol
Figure yyy shows the pilot pattern set for AAI sub-frames consisting of 5 OFDM symbols

14. 18 contiguous subcarriers
6 symbols 1 X X 1 X 1
18 contiguous subcarriers
Pilot pattern set 0
Pilot pattern set 1
Pilot pattern set 2
Figure xxx - The CoFIP Pattern for AAI sub frames with 6 OFDM symbols

15. 18 contiguous subcarriers
5 symbols 1 X X 1 X 1
18 contiguous subcarriers
Pilot pattern set 0
Pilot pattern set 1
Pilot pattern set 2
Figure yyy - The CoFIP Pattern for AAI sub frames with 5 OFDM symbols
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