1. Some Additional TPC Aspects to Consider
March 2002
March 2002
Some Additional TPC Aspects to Consider
Peter Larsson
Ericsson Research
Peter Larsson, Ericsson Research, Sweden

2. Motivation Three concerns:
March 2002
Motivation
Three concerns:
TPC Request/Report frames in conjunction with Power Management need to be addressed.
TPC Request/Report frames works fine for downlink power control, but would benefit from additional support in the uplink.
AP centric radar detection would benefit from additional TPC support in the uplink.
Peter Larsson, Ericsson Research, Sweden

3. Power Management and TPC (1)
March 2002
Power Management and TPC (1)
N.B CF-Pollable STAs
not considered
Beacon
Beacon
ACK
TPC
Report AP
Time
Pwr Mgt=0
Pwr Mgt=1
Channel busy
STA
TPC
Request
ACK
Awake
Awake
Power is consumed when being awake.
Why bother, one is anyway sending data immediately after the TPC frames?
Not entirely true! Implementation specific. E.g. after long silence, the first frame should be able to determine a sensible power level.
Peter Larsson, Ericsson Research, Sweden

4. Power Management and TPC (2)
March 2002
Power Management and TPC (2)
N.B Ack response
on PS poll not
considered
Beacon
Beacon
TIM
ACK
TPC
Report AP
Time
Pwr Mgt=1
Pwr Mgt=0
STA
TPC
Request PS
Poll
ACK
Awake
Awake
Awake
Peter Larsson, Ericsson Research, Sweden

5. March 2002
The Proposal
Beacon
Beacon AP
Time
Transmit
Power
indication
Transmit
Power
indication
STA
Awake
Awake
Exploit power save philosophy , i.e. wake up at TBTT, wait for beacon, do what is needed, then go back to sleep.
Complement with transmit power indication in Beacon in addition to existing TPC frames
Peter Larsson, Ericsson Research, Sweden

6. TPC UL/DL UL DL TPC Req./ Rep. Not useful TPC Beacon
March 2002
TPC UL/DL
N.B Commonly, not all
STAs do TPC in one
frame time UL DL
Message complexity = O(N)
Active and precise TPC
Message complexity = O(N)
Active and precise TPC
Beacon
ACK
Beacon
Beacon
ACK
Beacon
TPC
Rep
ACK
TPC
Rep
TPC
Req
ACK
TPC
Req
TPC Req./ Rep. AP
Time AP
Time
ACK
ACK
ACK
TPC
Req
TPC
Req
TPC
Rep
ACK
TPC
Rep
STA
STA
STA 1
STA 2
STA N
STA 1
STA 2
STA N
Message complexity = O(1)
Passive TPC. Reduced power consumption.
Not useful
TPC Beacon
Beacon
Beacon AP
Time
STA
STA 1,2,…N
STA 1,2,…N
Peter Larsson, Ericsson Research, Sweden

7. AP Centric Radar Detection
March 2002
AP Centric Radar Detection
2 complementary mechanisms for radar detection.
Medium silencing
TPC in UL
Regular TPC updates, in addition to on demand updates (i.e. TPC Req/Rep) will ease radar detection.
Peter Larsson, Ericsson Research, Sweden

8. Proposed alternatives
March 2002
Proposed alternatives
Alternative 1.
8 bit IE payload containing transmit power indication.
Alternative 2.
16 bit IE payload containing 8 bit transmit power indication and 8 bit estimated interference level
Alternative 1+2=3.
8 bit IE payload containing two fields in alt 2 added together. See 02/069 p.9. N.B. this is compatible with alt 1.
Peter Larsson, Ericsson Research, Sweden

9. March 2002
Conclusion
It was suggested that beacons contain transmit power information.
The beacon TP indication will complement the TPC request/ report method.
The proposal provides:
A power management compatible TPC mechanism for UL.
Improved medium efficiency for UL
Improved means for radar detection.
Peter Larsson, Ericsson Research, Sweden

10. March 2002
Two Ways Forward
Consider the power save, UL complexity & radar detection issues in conjunction with TPC later in the LB process.
Including TP level indication in the beacon may then be a recommended amendment.
Consider this issue this meeting and amend necessary beacon IE format/text in the draft.
Peter Larsson, Ericsson Research, Sweden