stds-802-16-tg2: Regarding my binding comment (from Barry Lewis)
[The message below bounced due to an attachment and some formatting problems. I have tried to restore it to its original intent. -Roger]
From: "Barry Lewis" <bplewis@btopenworld.com>
To: "Tg2_Reflector" <stds-802-16-tg2@ieee.org>
Subject: Regarding my binding comment.
Date: Wed, 18 Sep 2002 22:13:05 +0100
Dear tg2 colleagues,
Following submission of my binding comment on the mitigation section in the new tg2 draft I've had some discussion with Reza regarding my concerns.
It appears that whilst my cut down text proposed is a fine summary Reza feels that important issues are missing particularly with regard to "spatial processing" and "out of band coherency".
The one contribution on AA (24) deals only with the statistical element introduced by beamforming in the uplink direction / adjacent area scenario. I have no argument with this aspect which seems intuitive to me anyway even if we have generalised it in the text to all scenarios.
My concern is that since neither of the other characteristics mentioned above has been evaluated from the tg2 point of view, I feel we should be more circumspect in our choice of words. For example on spatial processing, the current text seems to suggest that this is effective only when wanted and interferer can be spatially separated and accepts that main beam coupling is dominant so how much of an impact does this signal processing give in this situation? It may be wrong to suggest it adds anything - it could be "swings and roundabouts" - we have no input.
The same argument goes for "the loss of coherency in out-of-band operation". Does the gain reduce below the increased level implied in the section 22.1? So what is the overall effect - it might be evens. Again we have no input.
So I think that perhaps all we can say is that these "features" exist and that their impact could warrant further analysis.
See my new proposal attached which I would find acceptable so long as the first sentence in 22.1.1 is retained. (i.e.mention of further analysis).
Best Regards
Barry Lewis
22 Mitigation
A number of mitigation techniques are described in Part 1. These are also generally of relevance to the types
of system analyzed in this Part 3. In addition, adaptive antenna (AA) techniques may also be useful in some
circumstances.
22.1 Adaptive Antenna Techniques
The direct effect of AA on coexistence is due to the fact that the RF energy radiated by transmitters is
focused in specific areas of the cell and is not radiated in all directions. Moreover, beam-forming with the
goal of maximizing the link margin for any given user inside the cell coverage area at any given time makes the AA beams' azimuth and elevation vary from time to time.
This characteristic would play a major role in determining the likelihood of interference in both the adjacent area and adjacent frequency block coexistence scenarios. Whilst the worst case alignment scenario may look prohibitive, since beamforming may produce a higher gain in the wanted direction, the statistical factor introduced by the use of AA may allow an otherwise unacceptable coexistence environment to become tolerable. [As proposed in my ballot comments except for changes highlighted]
22.1.1 Other Characteristics off Adaptive Antennas
Other characteristics could supplement the improvement brought about by the statistical nature of AA operation and warrant further analysis.
Signal processing and the development of spatial signatures associated with the wanted stations may also help provide some discrimination against interferers in certain directions further reducing the total impact of cumulative interference from neighbouring systems in adjacent areas.
For systems operating in adjacent frequencies, the loss of coherency in out-of-band operations reduces the AA gain towards the interferers/victims, which could reduce the amount of interference power.