RE: stds-802-16-tg4: coexistence with 802.11/802.15
All,
Since it is very unlikely to have the interfering station synchronized
to the interfered station, the OFDM modulation from the first will be
perceived as white noise at the second. So the answer to Ken's question
is the pure SNR.
In order to preserve communication in the interfered system, the
interfering signal level at the receiver should be at least x dB below
the useful signal, where x dB are given by the SNR corresponding to the
"rate": i.e. approx. 7dB for 6Mb/s and 27dB for 54Mb/s. This is valid if
the received signal is well above the noise floor. Otherwise the
condition becomes stricter and stricter.
There is some reciprocity in the system. If side-lobes from a .16
antenna cause bad interference into a .11a/15 antenna, the reciprocal is
also true. However, we are in a worse situation than .11a/15 systems
are. It is very likely that LAN applications will have larger link
reserve than WAN applications where manufacturers and providers will try
to push coverage as far as possible. E.g. .16 systems will likely use
the best LNA's available while .11a/15 system will likely use the
cheapest, trading a bit of sensitivity for price. In other words the
received signal in a .16 system will be much lower than in a .11a/15
system. Also, .11a/15 system can always switch to the lower UNII band
where we don't have access. And, by the way, they are mobile so
interference caused by .11a/15 devices is not predictable, while
interference caused by .16 devices is somehow stable.
In addition to these, we should also consider that both LAN and MAN
applications use TDD/TDMA. Unless it is close to a BS, an .11a/15 device
will interfere only with SS's, which transmit and receive for short
periods of time. The worst case of interference in both directions is
when .11a/15 are placed close to the BS.
Octavian
-----Original Message-----
From: Ken Peirce [mailto:ken@Malibunetworks.com]
Sent: Tuesday, April 10, 2001 2:13 PM
To: stds-802-16-tg4@ieee.org
Subject: RE: stds-802-16-tg4: coexistence with 802.11/802.15
All,
Is there a known/agreed to level of signal power that will
disrupt
an 802.11/802.15 system? Can we say that the method used is up to the
manufacturer, but that it is a requirement that the installed system
will
not emit more than this signal level in the direction of the host
building?
There are apparently many different means for achieving the target
effect.
Would the standard benefit if these approaches were categorized and
presented in a generalized manner?
Given the responses to this point, I do not feel that the MAC has any
coexistence requirement other than that of coexisting with other 802.16
systems. However, before this can proceed we will need input from the
PHY
group to understand what common "other 802.16 cell" detection method
could
be used by all manufacturers.
Thank you to those who've responded on this issue. Remember that
meetings
are best for decision making, voting, and/or final approvals. The
mailing
lists are the place to debate the merits of different approaches to
problems.
Cheers,
Ken