Just to add to Stephen's post, RRM works fine in certain environments depending on how the site was surveyed and AP placements. When you have AP's placed in hallways for example, RRM does work, but RRM doesn't know of your outer walls and this is where peolpe run into issues. WLC's will lower the TX of that AP's because they have line of site. So coverage to the outer walls in room start to suffer. I understand a lot of people out there are sold on RRM, but if it doesn't work for you, then its time to set the TX. If you had a site survey done and the required rssi -72dbm and the AP was set at a TX of 50mW, well to ensure that you have 100% coverage (site survey done right), then you need to make sure that your AP's are set at 50mW. Now the TX level depends on your radio band and maybe on certain AP's and country codes, but you can set your TX globally on the WLC. You can also set your Maximum Power Level Assignment, Minimum Power Level Assignment and your Power Threshold if you still want to use RRM. This way you can specify the maximum TX level and minimum TX level and tweak the Power Threshold if you wish. Now you can also set your coverage hole threshold instead of leaving that default.
I see RF issues in warehouse environments when my customer use RRM and complain about signal on the floor area. Well the AP's can see each other when hung on the beams on the top, so the AP's adjust their TX because of the algorithm. Well now the coverage is smaller due to the TX change. This is the same in office and in hospital environments when there are no AP's in the room and all the AP's are located in the hallway.
I don't use WCS heatmap to tell me if I have coverage or not. Your best bet is to do a post survey or use a site survey tool or any other wifi tool to tell you your rssi while walking these trouble areas.
-Scott
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