1. 2-Channel Option for 11g (proposal)
Rishi Mohindra
MAXIM Integrated Products
Rishi Mohindra, MAXIM

2. Motivation for 2-channel option
Adjacent channel interference
Reduce ACI to 11b level
Not have to additionally backoff Transmit level by 1.5 dB relative to 11a
FCC Forbidden Band Compliance.
Not have to backoff transmit level by 3 to 6 dB over 66% of channel capacity, to be FCC compliant (see appendix)
No range or network throughput penalty
Rishi Mohindra, MAXIM

3. Existing 3-channels in 11g
22 MHz
25 MHz
25 MHz
21.5 MHz
3 to 6 dB
FCC forbidden
band
FCC forbidden
band
2412 MHz (#1)
2437 MHz (#6)
2462 MHz (#11)
Drawbacks for 11g:
Adjacent channel interference:
above 11b levels for OFDM (25 MHz channel spacing)
Transmit Power Reduction:
up to 6 dB less OFDM transmit power at outer channels in order to be FCC compliant
Rishi Mohindra, MAXIM

4. 2-channel Scenario Improvements for 11g:
32 MHz
30 MHz
31.5 MHz
FCC forbidden
band
FCC forbidden
band
2422 MHz (#3)
2452 MHz (#9)
Improvements for 11g:
Adjacent channel interference at 11b levels (30 MHz channel spacing)
No Transmit Power Reduction in order to be FCC compliant (11a spectral mask sufficient)
Rishi Mohindra, MAXIM

5. Tighter Spectral Mask Issue
Proposed in r1-G-Spectral_Control_Issues_for_TGg
1.5 dB penalty in Transmit Power for middle channel (BPSK, QPSK, 16QAM)
Not relevant over 66% of channel capacity (two “Outer Channels”) as they already require 3 to 6 dB additional Transmit power backoff to be FCC compliant.
Rishi Mohindra, MAXIM

6. Tighter Spectral Mask ? Drawbacks for tighter spectral mask:
2412 MHz (#1)
2437 MHz (#6)
2462 MHz (#11)
FCC forbidden
band
22 MHz
25 MHz
21.5 MHz
-3 to -6 dB
-1.5 dB
Drawbacks for tighter spectral mask:
All channels with reduced power:
1.5 dB for center channel
3 to 6 dB for outer channels
Rishi Mohindra, MAXIM

7. Channel Occupancy Issue
Currently “Center” channel is occupied by the first installed network
2nd network (11g based) forced to “Outer” channel, and must operate at lower power (FCC compliant) with reduced network capacity
Very Low probability of 3 channels operating in same area
Why penalise the 2nd network?
Adopt 2-channel as an option: both networks can operate at full power (dictated by 11a EVM and spectral mask)
Rishi Mohindra, MAXIM

8. Proposal to instruct editor
Add the following text (shown underlined):
Operating Channel Frequencies
Operating channel frequencies of 2422 MHz and 2452 MHz (channels 3 and 9) are preferred in order to a) maximize transmit power while being FCC compliant, and b) to reduce adjacent channel interference.
Rishi Mohindra, MAXIM

9. APPENDIX
Rishi Mohindra, MAXIM

10. Simulation Model Used Rapps model 2400 MHz 2400 MHz OFDM source Power
Time domain
Power measurement
Rapps model
2400 MHz
Power
2400 MHz
OFDM source
BW=20 MHz
2422 MHz
No spectrum analyzer used
avoids frequency leakage
avoids errors due to Windowing
Power
Noise BW=1 MHz
Elliptic (N=6, 0.5dB ripple
BW of 1 MHz, 85 dB rejection)
Rishi Mohindra, MAXIM

11. Results Rapps model for Transmitter: Reference Case for BPSK OFDM:
P = 2.3, Psaturation = 24.2 dBm
Reference Case for BPSK OFDM:
Backoff = 4.29 dB
Output power = 19 dBm
Power at 22 MHz = dBm/MHz (fails FCC)
Reference Case for 64QAM OFDM:
Backoff = 7 dB
EVM = -25 dB
Output power = 16.8 dBm
Power at 22 MHz = -37 dBm/MHz (fails FCC)
Rishi Mohindra, MAXIM

12. Effect of Increased Backoff
From Psat (dB)
Output Power
(dBm)
Power at 22MHz
(dBm/MHz)
Increase in backoff (dB)
BPSK
4.29 19
-30.3
0 (reference)
8.3
15.7
-42.3 4
9.3
14.7
-46 5 64
QAM 7
16.8
-37
2.7 9 15
-43.4
4.7 10 14
-47.8
5.7
Rishi Mohindra, MAXIM

13. Real RF Power Amplifier
Why is measured power at 22 MHz offset more than simulation results ?
Rapps model is only AM/AM distortion
It does not model AM/PM distortion
It does not model MEMORY effects
Rishi Mohindra, MAXIM

14. Real PA Modulated Gain In Cartesian Plane Shows: AM/AM AM/PM
Memory Effects
Area enclosed
= memory effects
Rishi Mohindra, MAXIM

15. 2-channel impact on FCC forbidden band
Distance from forbidden band increases from 22 to 32 MHz
Emission level decreases by 14 dB (see spectrum next page)
Effective reduction in backoff up to 7 dB (for 2:1 slope of ACPR:Backoff)
Rishi Mohindra, MAXIM

16. Simulated Spectrum 22 MHz (fails FCC) 14 dB 31.5 MHz (passes FCC)
Rishi Mohindra, MAXIM