1. doc.: IEEE 802.11-04/0658r0 Assaf Kasher assaf.kasher@intel.com
July 2004
doc.: IEEE /0658r0
March 2006
Modulation Accuracy Requirements (EVM) For TGn Devices March /456 r0
Assaf Kasher
Assaf Kasher, Intel
Bruce Kraemer, Conexant

2. Modulation Accuracy What has changes since 11a –
March 2006
Modulation Accuracy
What has changes since 11a –
New code rate – rate 5/6
MIMO modulations
Longer Packets due to A-MSDU aggregation
Lower Packet Error Rate (PER) may be required for some application.
We need to specify modulation accuracy requirements for the new rate and MIMO modulations
Requirement – Modulation inaccuracy EVM shall be at a level that will cause at most 1dB degradation in the receiver rate per range curve.
Test should be simple
Assaf Kasher, Intel

3. Modulation Inaccuracy causes:
March 2006
Modulation Inaccuracy causes:
PA non-linearity
Transmitter phase-noise
I/Q modulator imbalance
Assaf Kasher, Intel

4. Is the channel important
March 2006
Is the channel important
The EVM noise covariance at the output of a ZF receiver is independent of the channel. It is spatialy white if the spreading matrix is unitary.
There is no need to specify channel for the EVM – an Identity matrix channel would suffice.
Assaf Kasher, Intel

5. March 2006
PER working-point
Some applications require packet error rate (PER) to be at most 1%
A-MSDU aggregation create an option for longer packets with a single FCS.
The requirements for Modulation Accuracy (EVM) and for were set for 1% PER and 4096 byte packets.
Simulations show this has very little effect on EVM requirements
Assaf Kasher, Intel

6. EVM simulations March 2006 Conclusion:
PN noise behave the same as white noise at the transmitter
Channel does not impact EVM requirements
Assaf Kasher, Intel

7. Why not require lower EVM
March 2006
Why not require lower EVM
Lower EVM (Higher modulation accuracy) means:
Higher power
Larger circuits
Higher costs
All of these will be a burden for lower power small form factor devices.
Assaf Kasher, Intel