RE: stds-802-16: OFDM vs. Other Waveforms
The "Issue" is not just Multipath, but also predictable / reliable
performance in non- and near-LOS deployments, especially where CPE
installation cost / process is an issue (e.g. residential and SME) or for
customer self-installability or portability.
We need to answer all these questions for ALL waveforms - and people
currently seem to be avoiding this issue. Restricting modulation rates to
16-QAM or less for NLOS (which is probably the only viable approach at
present) will severely limit payload throughput / capacity and fail to
sustain a viable business case. We should be concentrating far more on
solutions which are optimized for NLOS performance (i.e. lower modulation
rates) and superior payload capacity ( e.g. through very high inter-cell and
intra-cell frequency reuse). Unfortunately, more people seem to be
interested in just pushing the technology that they happen to have (almost)
available, rather than addressing the real world issues.
> David Trinkwon
> Email : Trinkwon@compuserve.com
> USA Tel : 650 245 5650 Fax : 650 649 2728
> UK Tel : +44 (0)7802 538315 Fax : +44 (0)20 7681 1695
-----Original Message-----
From: owner-stds-802-16@majordomo.ieee.org
[mailto:owner-stds-802-16@majordomo.ieee.org]On Behalf Of Mark McHenry
Sent: 03 July 2001 03:16
To: stds-802-16@ieee.org
Subject: stds-802-16: OFDM vs. Other Waveforms
1) Does anyone have any measured data or know of published papers that
proves that the OFDM waveform performs better than other waveforms (with a
good equalizer) in heavy multipath situations in either fixed and mobile,
broadband, 500 m to 15 km long, terrestrial links? Several people have told
us that with a good equalizer, "conventional" waveforms such as QPSK obtain
nearly the same performance level but at a lower hardware cost.
2) Is there a "generally excepted" simulated propagation test case that we
could use for a side-by-side comparison of OFDM waveforms compared to
conventional waveforms? I have heard that service providers have test cases
that they use to rate modem performance.
Thanks,
--Mark
Mark McHenry
Shared Spectrum Company
8012 Birnam Wood Drive
McLean, Virginia 22102
mmchenry@sharedspectrum.com
Voice: 703-761-2818
FAX: 703-761-2818