1. Support for Deferral Management in 802.11v
January 2003
IEEE /100r1
May 2004
doc: V2-IEEE /xxxr1
Support for Deferral Management in v
Joe Kwak, Marian Rudolf
InterDigital Communcations
Submission
Kwak, Rudolf

2. Motivation
CSMA is meant to prevent two nodes in the same vicinity from transmitting simultaneously by having one defer to the other
This limits the level of interference perceived by receivers but it also limits the level of simultaneous channel reuse in the system thus limiting the capacity
The two key parameters involved in carrier-sensing and deferral are:
The transmission power used by the transmitter
The energy detection threshold (EDT) used by the receiver
Both parameters can be controlled to allow for higher channel reuse and higher system capacity
We refer to this as deferral management
Kwak, Rudolf
Submission

3. Example C/2 C/2 EDT control or C C Power control C C Kwak, Rudolf
January 2003
IEEE /100r1
Example
Noise floor at Rx = -94 dBm
107 dB
104 dB
104 dB
101 dB
70 dB
70 dB
STA 1
STA 2
AP 1
AP 2
BSS 1
Capacity
BSS 2
Capacity
Tx = 20 dBm
EDT= -90 dBm
S=-50dBm
Imax=-84 dBm
SNR=44 dB
SIR= 
Tx = 20 dBm
EDT= -90 dBm
S=-50dBm
Imax=-81 dBm
SNR=44 dB
SIR= 
Tx = 20 dBm
EDT= -90 dBm
S=-50dBm
Imax=-81 dBm
SNR=44 dB
SIR= 
Tx = 20 dBm
EDT= -90 dBm
S=-50dBm
Imax=-84 dBm
SNR=44 dB
SIR= 
C/2
C/2
EDT control
Tx = 20 dBm
EDT= -80 dBm
S=-50dBm
Imax=-84 dBm
SNR=44 dB
SIR= 34 dB
Tx = 20 dBm
EDT= -80 dBm
S=-50dBm
Imax=-81 dBm
SNR=44 dB
SIR= 31 dB
Tx = 20 dBm
EDT= -80 dBm
S=-50dBm
Imax=-81 dBm
SNR=44 dB
SIR= 31 dB
Tx = 20 dBm
EDT= -80 dBm
S=-50dBm
Imax=-84 dBm
SNR=44 dB
SIR= 34 dB or C C
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Power control
Tx = 10 dBm
EDT= -90 dBm
S=-60dBm
Imax=-94 dBm
SNR=34 dB
SIR=34 dB
Tx = 10 dBm
EDT= -90 dBm
S=-60dBm
Imax=-91 dBm
SNR=34 dB
SIR= 31 dB
Tx = 10 dBm
EDT= -90 dBm
S=-60dBm
Imax=-91 dBm
SNR=34 dB
SIR= 31 dB
Tx = 10 dBm
EDT= -90 dBm
S=-60dBm
Imax=-94 dBm
SNR=34 dB
SIR= 34 dB C C
Kwak, Rudolf
Submission

4. Need for standardization?
January 2003
IEEE /100r1
Need for standardization?
Without standardization, the AP can only control its own deferral management settings
Restricting deferral management to the APs leads to the following issues:
In the case of EDT control
The STA will not capitalize on the potential increase in channel reuse
In the case of Power Control
The increase in channel reuse not be achieved when STA transmit
STA ACKs can collide with packets in other BSSs.
For Deferral Management to reach its full potential, it has do be done in a coherent and a cohesive manner across all the APs and STAs.
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Kwak, Rudolf
Submission

5. Challenges of Deferral Management
January 2003
IEEE /100r1
Challenges of Deferral Management
Potential impact on transmission rates
Elevating the EDT of WLAN nodes tends to elevate the level of co-channel interference in the system => decrease of SIR
Lowering the power of WLAN nodes tends to decrease the SNR
In general, a decrease of SIR and/or SNR can translate into transmission rate reductions
Power and/or EDT have to be controlled such that capacity gains due to increase of channel reuse are not offset by the decrease of SNR/SIR
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Kwak, Rudolf
Submission

6. Power control vs. EDT/DT control
January 2003
IEEE /100r1
Power control vs. EDT/DT control
EDT control
Less interactions with rate control
Offers battery savings from the Rx side
Less dynamic range than Power Control
Most direct consequence of elevating the EDT within a BSS is more Tx opportunity in that BSS
Only useful for DSSS PHYs (may be other equivalent CCA parameters for other PHYs)
Power Control
More interactions with rate control
More dynamic range
Offers battery savings from Tx side AND on Rx side
Most direct consequence of reducing the power within a BSS is more Tx opportunity in other BSSs
Applies to all PHYs
802.11v should support both
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Kwak, Rudolf
Submission

7. Why TPC from 802.11h is not enough
January 2003
IEEE /100r1
Why TPC from h is not enough
The TPC feature of h is a good start but geared towards regulatory requirements; not Radio Resource Management
Does not provide the means to control EDT of STA
Does not provide the means to control the transmission power on a STA by STA basis
Currently only works in 5GHz band, TGk did not work on power control.
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Kwak, Rudolf
Submission

8. Possible control mechanisms
January 2003
IEEE /100r1
Possible control mechanisms
Direct control from AP
Centralized approach where the AP determines the STA deferral management parameters
AP sends management/action frame to associated STAs that dictates a certain:
Tx power to use and/or
EDT value to use and/or
CCA mode to use
This control could done on a per-STA basis
This implies some mechanisms to measure/report inter-STA RPI/pathlosses
Indirect control from AP
Distributed approach where the determination of the settings is done at the STA
AP sends rules/guidelines that STAs need to follow to determine the power/EDT settings
Examples of rule:
STA have to set their EDT/DT at the highest value that still makes them defer to a list of nodes provided by the AP
STA that have the required link margin have to set their power at the smallest value possible that ensures that they are heard by a list of nodes. MAC address and EDT of the nodes would be provided by the AP
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Kwak, Rudolf
Submission

9. Action Frame Signaling
New Deferral management IE’s
Deferral management capability
Supported CCA modes, Max/Min Tx power, Max/Min EDT
Deferral management reports and requests
CCA mode, EDT, Tx Power operational settings (or range)
Deferral management set command
Single IE could be used for both direct and indirect control modes
Similar to h TPC or DFS, Deferral management can use Beacon/Probe Response frames and/or new dedicated action frames
New Deferral management action frames
Deferral management request + reports
Element ID
Length
Control Mode
Controlled parameter
Parameter Value
Rule
Node list
Category
Action
Deferral Management set command
Kwak, Rudolf
Submission

10. Support features Request/Reporting of Power/EDT control capabilities
January 2003
IEEE /100r1
Support features
Request/Reporting of Power/EDT control capabilities
e.g. Max/Min Power, Max/Min EDT, supported CCA mode
STA reporting to AP inter-STA path losses
Periodic loud packets would enhance this
EDT/CCA parameters to be used during measurement periods
SMI – Structure of Management Information
ASN.1 – Abstract Syntax Notation 1
Kwak, Rudolf
Submission