1. Transmit Spectral Mask Changes
Month Year
doc.: IEEE yy/xxxxr0
Nov 2010
Transmit Spectral Mask Changes
Date:
Authors:
Allan Thomson, Cisco Systems
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
Nov 2010
Comment
comment #10028
"TX mask limit should be softened. The strictness currently specified is not needed and imposes excessive constraints on designs. Existing a systems are built with a softer specification of -40 dBr and have not been shown to suffer from excessive interference issues in the field."
Allan Thomson, Cisco Systems
John Doe, Some Company

3. Nov 2010
Issues with comment
11n Transmit spectral mask was made after substantial discussion (one reason provided on slide 5)
Relaxing the spectral mask leads to lower transmit power in the band edge channels.
FCC CFR47 part 15 Section.205: Restricted bands of operation, lists the channels part of the restricted band where OOB emission should not exceed -41.3dBm/MHz.
Unequal transmit power capacity may lead to un equal sharing of unlicensed band
Allan Thomson, Cisco Systems

4. Comparison of Transmit spectral mask
Nov 2010
Comparison of Transmit spectral mask
Proposed Change according to comment
-40dBr
5dB
Allan Thomson, Cisco Systems

5. Effect of proposed spectral mask change on maximum Transmit Power
Month Year
doc.: IEEE yy/xxxxr0
Nov 2010
Effect of proposed spectral mask change on maximum Transmit Power
-0.3 dBm/MHz
-40dBr
30 MHz
-41.3 dBm/MHz
2483.5
2390
fc = 2422
Channel 3
“Regulatory + Mask change” Limits Band edge 20 MHz operation to < 13dBm
Current transmit spectral mask allows 18dBm operation
Allan Thomson, Cisco Systems
John Doe, Some Company

6. Effect of proposed spectral mask change on Capacity
Month Year
doc.: IEEE yy/xxxxr0
Nov 2010
Effect of proposed spectral mask change on Capacity
OOB Emission based on relaxed
spectral mask
OBSS
-40dBr
20 dB
5 dB
30 MHz
2390
fc = 2422
Channel 1
The relaxed spectral mask leads to 5dB loss in performance
Loss in Capacity – 20MHz OBSS, 20 dB SINR using previous mask, 15dB SINR using new mask
C = BW x log2 ( 1 + SNR)
Loss in capacity = 32.6 Mbps
Allan Thomson, Cisco Systems
John Doe, Some Company

7. Nov 2010
Conclusion
The 11n transmit spectral mask was designed to allow operation at high transmit power and at the same time meeting the regulatory requirements.
Technology has improved to allow lower power and cost PA designs which meets the current 11n Transmit spectral mask
Relaxing transmit spectral mask requirement may lead to lower transmit power capability of future 11n devices operating at band edge channels
Relaxing transmit power reduces performance of non adjacent channel BSS.
No need to change the 11n transmit mask requirement
Allan Thomson, Cisco Systems

8. Nov 2010
Questions ?
Allan Thomson, Cisco Systems

9. Appendix – A (Restricted bands according to 15.205)
Nov 2010
Appendix – A (Restricted bands according to )
Allan Thomson, Cisco Systems