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stds-802-16-tg3: TG3 draft COMMENT - 802.16.3c-01/59
[Submitter's Last Name]
Goldhammer
[Submitter's First Name]
Marianna
[Starting Page #]
28
[Starting Line #]
3
[(T)echnical for Content-Related Material; (E)ditorial for typos,
grammar, etc.]
T
[Detailed Description of Proposed Insertion, Deletion, Change]
Change
"It is defined for FFT sizes 512, 1K, 2K and 4K of which the
2K mode is mandatory."
to
"It is defined for FFT sizes 512, 1K, 2K and 4K of which the
1K mode is mandatory for channel spacing higher than 5MHz."
[Reason for Edit]
The FRD (doc. IEEE 802.16.3-00/02r4) specifies:
"The MAC and PHY protocols MUST permit the operation with channel
spacing of 1.75, 3.5 and 7MHz when using ETSI masks and 1.5 to
25MHz when using other masks. The typical value for performance
analysis SHOULD be 3.5MHz for the ETSI mask and 3MHz for the
MDS mask."
The 2kFFT symbol length at 3MHz is higher than 500us for both ETSI
and MMDS masks. The phase-noise problem will influence on both cost
and time-to-market.
The carrier spacing is 2KHz, requiring a frequency stability
of 20Hz, which it is a real problem at 3GHz. At 11GHz it is almost
un-feasible.
The 256FFT has, at 3-3.5MHz, a duration higher than 64us. The maximum
guard interval can be 16us, that can accommodate, at 16QAM (maximum
mandatory constellation) all the channel models, including SUI-6, as
defined
in EEE 802.16.3c-01/29. As a remainder, SUI-6 specifies a rms delay of
of 5.2us and a maximum delay of 20us, at an
attenuation of 26dBm for 30deg. antenna, 14dBm for omni antenna.
With 16ms guard interval, only 4ms of the precedent symbol will interfere at
generally at less than 20dB attenuation, only in case of omni antenna at
14dB attenuation. Also in this case, the adaptive modulation and error
correction will resolve the problem.
Same is true for 1kFFT, for channel spacings up to 25MHz (not realistic!).
Conclusions: 1. 1k FFT shall be used as OFDMA mandatory FFT size;
2. Up to 4GHz, 256FFT size is enough. Due to the fact
that there
is no OFDMA defined for 256FFT size, the use of 1kFFT at
less than 4MHz bandwidth shall be optional. We cannot
define mandatory modes that will have a negative influence
on standard adopters.
[Submitter's Last Name]
Goldhammer
[Submitter's First Name]
Marianna
[Starting Page #]
11
[Starting Line #]
32
[(T)echnical for Content-Related Material; (E)ditorial for typos,
grammar, etc.]
T
[Detailed Description of Proposed Insertion, Deletion, Change]
Insert "not" before "to provide error correction"
Change
"A compliant device shall implement either 256 FFT with TDMA,
or alternatively 2048 FFT with OFDMA for any bandwidth."
to
"A compliant device shall implement either 256 FFT with TDMA,
at any bandwidth, or alternatively 1024 FFT with OFDMA for
more than 5MHz bandwidth."
[Reason for Edit]
As before
[Submitter's Last Name]
Goldhammer
[Submitter's First Name]
Marianna
[Starting Page #]
28
[Starting Line #]
17
[(T)echnical for Content-Related Material; (E)ditorial for typos,
grammar, etc.]
E
[Detailed Description of Proposed Insertion, Deletion, Change]
Change "shall"
with "will"
[Reason for Edit]
512FFT can be used also with OFDM
[Submitter's Last Name]
Goldhammer
[Submitter's First Name]
Marianna
[Starting Page #]
31
[Starting Line #]
3
[(T)echnical for Content-Related Material; (E)ditorial for typos,
grammar, etc.]
T
[Detailed Description of Proposed Insertion, Deletion, Change]
Insert:
"The implementation of variable location pilots is optional. Nevertheless,
if this option will not be used, fixed pilots will be inserted in the MAP2
positions allocated for variable location pilots"
[Reason for Edit]
The scattered pilots are useful for mobile applications, but imply
significantly
higher time-to-market and higher memory requirements.
Due to the fact that the PAR specifies only fixed applications, the mobility
support should not influence on system availability and cost.
[Submitter's Last Name]
Goldhammer
[Submitter's First Name]
Marianna
[Starting Page #]
34
[Starting Line #]
7
[(T)echnical for Content-Related Material; (E)ditorial for typos,
grammar, etc.]
T
[Detailed Description of Proposed Insertion, Deletion, Change]
Insert:
"The implementation of variable location pilots is optional. Nevertheless,
if this option will not be used, fixed pilots will be inserted in the MAP2
positions allocated for variable location pilots"
[Reason for Edit]
Same as before.
Marianna Goldhammer
Director - Strategic Technologies
BreezeCOM Ltd.
21 HaBarzel Street
P.O.Box 13139, Tel Aviv 61131, Israel
Tel: (972)- 3 -6456241/6262
Fax: (972) -3 -6456290
Email: mariannag@breezecom.co.il
http://www.breezecom.com