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Doc.: IEEE 802.11-08/1135r0 Submission September, 2008 Carl Kain, NoblisSlide 1 Frequency and Clock Tolerance Comments Date: 2008-09-09 Authors:

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Presentation on theme: "Doc.: IEEE 802.11-08/1135r0 Submission September, 2008 Carl Kain, NoblisSlide 1 Frequency and Clock Tolerance Comments Date: 2008-09-09 Authors:"— Presentation transcript:

1 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 1 Frequency and Clock Tolerance Comments Date: Authors:

2 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 2 Abstract This presentation addresses comments concerning frequency and clock tolerance, CID ; 380,

3 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 3 Frequency and Clock Tolerance Base standard specifies 10 ppm for both frequency and clock tolerance for 5 MHz channels Base standard specifies 20 ppm for both frequency and clock tolerance for 10 MHz channels TGp Draft 4.0 specifies 10 ppm for both frequency and clock tolerance for 10 MHz channels Commenters who oppose tighter values want either rationale or are primarily are concerned with cost

4 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 4 Comments From Master Spreadsheet 375Fischer, Matt hew TRThe tolerance value seems too tight. Previous specifications have always allowed +- /20ppm, which seems to be implementable. Change the tolerance to +/- 20 ppm. 376Hansen, Chris toph er TRThe tolerance value is too tight. This will unnecessarily increase the cost of implementations. Previous specifications have allowed +-/20ppm, which is reasonable. Change the tolerance to +/- 20 ppm. 377Trachewsky, Jaso n TRThe frequency accuracy requirement is too tight.Change the tolerance to +/- 20 ppm. 378Wang, Qi TR"The transmitted center frequency tolerance shall be +/-10ppm maximum for 10 MHz channels used by a STA in the WAVE mode." What is the rational to have such a tight tolerance value? Previous specifications have always allowed +/- 20ppm, which seems to be implementable. Change the tolerance to +/- 20 ppm.

5 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 5 Comments From Master Spreadsheet 380Erceg, Vinko TRIt is not clear to me that the transmit frequency tolerance of +/-10 PPM is required. Crystal at that tolerance level is expensive! Change the tolerance to +/-20 ppm or show simulation results that prove that +/- 10 ppm is required. 382Kolze, Tho mas TRTransmit frequency tolerance of +/-10 PPM is required but not shown to be needed. Relax the tolerance to +/-20 ppm or present case that proves +/- 10 ppm is required. 383Moorti, Raje ndra TR10ppm frequency tolerance is too restrictive and cannot be easily / cheaply implemented. moreover, there is no need for such a tight tolerance since a 20ppm error can be corrected change to 20ppm tolerance 384Roy, Rich ard TRThere does not appear to be any requirement for a tighter tolerance on clock frequency or transmitter center frequency than those already in the standard.. The current implementations seem to work just fine in the harshest environments, both experimentally and theoretically. Without a valid requirement to tighten these specs, they should be left alone. Note that if a manufacturer of an ITS system implementing the WAVE capability decided to require a tighter tolerance on either or both of these parameters, such a requirement could easily be imposed in the procurement procedure. Remove this specification.

6 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 6 Discussion Document ; Bob Sorrano of JHU discussed issue based on testing done on JHU campus Conclusion was: –Results from initial testing using IEEE a devices as substitutes for p devices in a high speed environment indicated some problems could result in synching and maintaining signal lock which could be mitigated by requiring a more stringent frequency tolerance of ±10 ppm vs. the current ±20 ppm requirement that is sufficient for non-mobile and mobile platforms not required to communicate over high speeds. Commenters have proposed an alternative –Make the 10 ppm values optional in the TGp amendment

7 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 7 Alternative Recommendation Recommend to make 10 ppm frequency tolerance and clock tolerance for 10 MHz BW in Clause 17 optional Instruct the editor to make the following changes to p D4.0: Transmit center frequency tolerance –Insert the following statement after the first statement in : –An optional transmitted center frequency tolerance of ±10 ppm maximum for 10 MHz channels is recommended for use by a STA that has the MIB attribute dot11WAVEEnabled set to true Symbol clock frequency tolerance –Insert the following statement after the first statement in : –An optional symbol clock frequency tolerance of ±10 ppm maximum for 10 MHz channels is recommended for use by a STA that has the MIB attribute dot11WAVEEnabled set to true. Remove any PICs associated with previous “shall” statement for 10 ppm tolerance in and found in p D 4.0 Moved Second For Against Abstain

8 doc.: IEEE /1135r0 Submission September, 2008 Carl Kain, NoblisSlide 8 References r0


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