1. Investigation of PA Model Sample Rate for TGac
April 2007
doc.: IEEE /0570r0
July 2009
Investigation of PA Model Sample Rate for TGac
Date:
Authors:
Eldad Perahia, Intel Corporation
Eldad Perahia, Intel Corporation

2. January 2009
Introduction
The PA model utilized in the IEEE TGn comparison criteria document [1] was a RAPP model [2]
It is proposed that this same model be reused for TGac
In [1], it was stated the oversampling rate for the PA model should be at least 4x.
With the larger bandwidth of TGac it is desirable to relax the 4x oversampling if possible
Reduce computer resource requirements
Potentially reduce the number of rate conversion stages and thus filtering stages
An evaluation of the TGn PA model at both 2x and 4x oversampling rates was conducted
Goal is to assess whether a PA oversampling rate of 2x is sufficient for .11n and TGac
Eldad Perahia, Intel Corporation

3. RAPP model and Parameters
January 2009
RAPP model and Parameters
The RAPP model in [2] is a AM/AM model specified as
Where in that same document it was suggested that
Additionally, [2] suggests an oversampling range of 2x to 4x.
The comparison document [1], specified that p be set to a value of 3.
The document also recommended a Psat = 25 dBm
Finally, the comparison document also stated the PA model should be run at an oversampling rate of at least 4x.
Eldad Perahia, Intel Corporation

4. January 2009
Simulation Setup
The PA model parameters for this simulation were set as outlined in the comparison criteria, p = 3, Psat = 25dBm.
Two PA oversampling rates were simulated, 2x and 4x.
In the simulator the oversampling rate was maintained from transmitter to the front end of the receiver
A total of 3 configurations were investigated:
64-QAM, 5/6 code rate, 40MHz bandwidth
256-QAM 3/4 code rate, 80MHz bandwidth
1024-QAM 3/4 code rate, 80MHz bandwidth
All were simulated with 1000 byte packets
The simulator was configured with NO impairments other than the PA model and utilized a Fourier Channel model
Eldad Perahia, Intel Corporation

5. January 2009
PA Model Oversampling with 64-QAM, 5/6 code rate, 4x4 4-streams (MCS 31)
Oversampling rates of 2x and 4x
have the same performance at a PA
backoff of 8dB
There is a difference in performance
as the PA backoff is decreased, but
is small for reasonable backoff values
Eldad Perahia, Intel Corporation

6. January 2009
PA Model Oversampling with 256-QAM, 3/4 code rate, 4x4 4-streams, 80MHz bandwidth
Oversampling rates of 2x and 4x
have the same performance at a PA
backoff of 8 or 9dB
There is a difference in performance
as the PA backoff is decreased, but
is small for reasonable backoff values
Eldad Perahia, Intel Corporation

7. January 2009
PA Model Oversampling with 1024-QAM, 3/4 code rate, 4x4 4-streams, 80MHz bandwidth
Oversampling rates of 2x and 4x
have the same performance at a PA
backoff of 10 and 11dB
There is a difference in performance
as the PA backoff is decreased, but
is small for reasonable backoff values
Eldad Perahia, Intel Corporation

8. January 2009
Oversampling of 2x and 4x for all configurations at a Nominal PA backoff level
Eldad Perahia, Intel Corporation

9. January 2009
Summary
An investigation of the PA model described in [2] and specified in [1] was done with both 2x and 4x oversampling
Results show that there is some slight differences when the signal is being severely compressed.
In those cases the 2x sampling rate is slightly worse from a performance perspective.
In normal operating regions, within a few dB of the Lossless level, the difference is negligible.
It is recommended that the PA model oversampling rate requirement be lowered to 2x.
Eldad Perahia, Intel Corporation

10. January 2009
References
[1]Stephens, A.,et al., IEEE TGn Comparison Criteria, IEEE /814r31, July 12, 2004
[2]Webster, M., Suggested PA model for HRb, IEEE /294, Sept, 2000
Eldad Perahia, Intel Corporation