1. Discussion of Explicit vs. Implicit PC-A-MAP IE Assignment (15.2.3)
IEEE Presentation Submission Template (Rev. 9)
Document Number: IEEE S802.16m-09/2584
Date Submitted:
Source:
Yi Hsuan, Rongzhen Yang, Hujun Yin
Intel Corporation
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IEEE m: “802.16m/D2 letter ballot”
Target topic: P802.16M/D
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2. Background
In current P802.16M/D2, the text of PC-A-MAP IE assignment for CLPC is not ready;
In previous meetings, the implicit assignment methods were proposed (C80216m-09/1054 and C80216m-09/1903):
It claims the benefit for signaling overhead saving
But it limits the flexibility of PC-A-MAP IE assignment for period, power adjust step and CLPC enable/disable;
Here we share our study of 16m CLPC usages, to identify the suitable solution for PC-A-MAP IE assignment.

3. Evaluation Setting Key Assumption: Evaluation Parameters Setting:
CLPC should at least support power tracking at for different speed:
Three moving speeds are selected for analysis: 3km/h, 30km/h and 120km/h with 16m e-ITU channel;
It is considered as “following” of CLPC when error is less than deltastep/2; (deltastep = 0.5 dB);
Evaluation Parameters Setting:
Set different periods for CLPC control rate for different moving speeds, to identify the minimum period of each scenarios;
Set different CLPC power adjust step (deltastep) for different moving speeds, to identify the best step size of each scenarios;

4. Moving Speed: 3km/h
Example of Power Tracking
Absolute Error CDF
CLPC Power Control Step Size (0.5dB) of 2 bits: -0.5, 0, +0.5, 1 dB
Period of 20 frames with 0.5dB adjust step can effectively tracking channel fading (following probability with 90%)

5. Moving Speed: 30km/h 2 choices can meet 90% following requirement:
Absolute Error CDF of
Step Size (0.5dB) of 2 bits: -0.5, 0, +0.5, 1 dB
Absolute Error CDF of
Step Size (1dB) of 2 bits: -1, 0, +1, 2 dB
2 choices can meet 90% following requirement:
Period of 2 frames with 0.5dB adjust step
Period of 5 frame with 1dB adjust step

6. Moving Speed: 120km/h CLPC Power change in every frame is needed
Absolute Error CDF of
Update Period 1 Frame
Absolute Error CDF of
Update Period 2 Frame
CLPC Power change in every frame is needed
Adjust step 1dB (-1, 0, +1, 2) is better than 0.5dB & 2dB

7. Summary of CLPC Power Tracking Evaluation
The CLPC power control rate should be configurable for the different MS.
The CLPC power control change step can be configurable for the different MS, 2 options are enough: minimum step = 0.5 or 1 dB.
Current implicit assignment cannot support upper 2 requirements.

8. Supporting of Open Loop and Closed Loop Coupling
Coupling of Open Loop and Closed Loop Power Control is defined at SDD :
Open Loop Power Control coarsely adjust uplink transmit power with low signaling overhead
When there is high traffic, Closed loop will be the main power control scheme
Explicit vs. Implicit Assignment:
Explicit Assignment can implement it easily by a field of Assignment Duration (frames)
Currently, there is no implicit assignment method that can support it.

9. Recommendation
PC-A-MAP IE Assignment should be explicit to include at least 3 fields:
Control Rate (assignment period)
Power Change Step: 1 bit field to indicate 0.5 or 1 dB
Assignment Duration: the begin and the end of assignment
The proposed text in contribution xxxx and its latest version is recommended.