1. Signaling Overhead Reduction Technique for PMI Coordination
Document Number: IEEE C80216m-09xx
Date Submitted:
Source: C80216m-09_1627
Shuangfeng Han, David Mazzarese,
Sangwoo Lee, Heewon Kang, Hokyu Choi
Samsung Electronics
Venue:
IEEE Session #62
Re: AWD comment for multicell MIMO
Base Contribution:
C80216m-09_1625
Purpose:
For TGm discussion and adoption of m AWD text.
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2. Additional information feedback for conflict resolution in PMI coordination
Conflicting PMI coordination requests
Conflicting requests from MSs within one cell
ABS makes decision to choose some requests based on additional feedback and exchange with corresponding adjacent ABSs
Conflicts resolution purely based on ABS scheduling
Conflicting requests from MSs in different cells
Additional information needed to assist decision making
Additional information feedback
Normalized interference power: ratio of the average interference power from each dominant interfering cell to total received interference power.
Frequent feedback not needed due to slow variation
Similar SINR, request with higher NIP has higher priority, vice verse.
Similar NIP, request with higher SINR has lower priority, vice verse.
For overhead reduction, quantization of NIP can be above some threshold, e.g., ¼.

3. Overhead reduction for PMI subset feedback (1)
Why we need PMI subset feedback?
1 PMI coordination (recommendation or restriction)
PMI restriction brings smallest cell edge gain and smallest cell average degradation
More restricted PMIs, more cell edge gain and more cell average degradation
PMI recommendation brings largest cell edge gain and also largest cell average degradation
More recommended PMIs, less cell edge gain and less cell average degradation
PMI subset coordination is needed for tradeoff between cell edge and cell average performance, although optimal set size is not easy to obtain.
How we feed back PMI subset?
Subset determined by AMS based on channel conditions
Subset represented by the worst or best PMI index + 1 additional bit to indicate 1 or 2 correlation levels
How ABS knows PMI subset and downlink indicate?
ABS can figure out which PMI subset is requested based on cross correlation between PMI
ABS makes decision which PMI subset is used for DL tx and may use bitmap for DL indication

4. Overhead reduction for PMI subset feedback (2)
Correlation levels (4 bit 16m base codebook)

5. Overhead reduction for PMI subset feedback (3)
Relationship between channel power and correlation
1 receive antenna at AMS
2 receive antenna2 at AMS
In correlated channels, this relationship is acceptable. Since we apply PMI coordination to rank 1 transmission only, this relationship can allow us to feedback PMI subset with reduced overhead.

6. Overhead reduction for PMI subset feedback (4)
PMI subset representation: MIMO channel feedback header
Example: how to determine n1 and n2?
Table X3 - PMI_coordination_subset
PMI_coordination_subset
Value
0b0 n1
0b1 n2

7. Proposed Text
See C80216m-09_1625

8. Thank you