Investigation of PA Model Sample Rate for TGac April 2007 doc.: IEEE 802.11-07/0570r0 July 2009 Investigation of PA Model Sample Rate for TGac Date: 2009-07-13 Authors: Eldad Perahia, Intel Corporation Eldad Perahia, Intel Corporation

January 2009 Introduction The PA model utilized in the IEEE 802.11 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 802.11 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

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

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

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

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

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

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

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

January 2009 References [1]Stephens, A.,et al., IEEE 802.11 TGn Comparison Criteria, IEEE 802.11-03/814r31, July 12, 2004 [2]Webster, M., Suggested PA model for 802.11 HRb, IEEE 802.11-00/294, Sept, 2000 Eldad Perahia, Intel Corporation