Just to be clear, we don’t have to do these things to make wireless work. It makes it work better. But it is sometimes necessary to make wireless work acceptably in the most challenging environments. That said, left to defaults Aruba’s ARM also adjusts 2.4 GHz Tx power way down. So far down, in fact, that coverage gaps show up. It also tends to keep power higher on busy APs and lower on less busy ones. In some cases the power on the 2.4 radio will be the same as the power on the 5 GHz radio. These characteristics forces us to configure a range of acceptable power levels for ARM to choose from. Once you’re doing that, why not select the optimum power levels?
While I’m no expert on Cisco wireless, I have assisted some departments with problems on their Cisco infrastructure. Based on that limited experience, I have far less confidence in RRM than you seem to. Finally, I agree about stacking in regard to location-based services. I find it frustrating that we have to choose between better network performance and better location services, but given our current business requirements I’m going to choose performance. As for the metal back plate, Aruba has that too. Unfortunately, it’s not that effective at radiating the energy downward. The Aruba AP’s have a ”backlobe” pointing straight up. While it’s -10 dB, it’s only a couple dB less than the off-axis upward radiation. Unless the floors are exceptionally lossy, we experience lower CCI by getting a wall or two as well as the floor between APs. From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]] On Behalf Of Jeffrey D. Sessler Sent: Thursday, August 13, 2015 12:44 PM To: [email protected] Subject: Re: [WIRELESS-LAN] Exclusive 2.4 Ghz and 5 Ghz SSIDs This is just really surprising to me that you have to do this with Aruba (adjust Tx manually). On Cisco, the RRM and TPC are really well implemented, and in general when dealing with dense deployments in residential halls, the 2.4 radios are running at such low Tx power that a dual 2.4/5 client will never pick 2.4 over 5 unless: 1) It’s broken, 2) The client is in a fringe area and there isn’t another 5 Ghz radio to roam to, or 3) The AP placement is outside the client use area e.g. In hallway instead of in-room. Also, I note in your doc you say "Try to avoid locating APs in the same locations on each floor of a multi-story building (aka, stacking).” With Cisco APs where the entire bottom of the AP is a metal plate, you’re actually better off stacking AP’s on adjacent floors, especially in cases where you want to utilize location services. Staggering AP’s across multi-floor can result in a client on say floor 2 being closer to an AP on floor 3, making location services unreliable. If the Ap’s are stacked, unless the floor is made of glass, a client on floor 2 should always associate with AP’s on the same floor. Jeff From: "[email protected] <mailto:[email protected]> " on behalf of Chuck Enfield Reply-To: Chuck Enfield Date: Wednesday, August 12, 2015 at 8:43 PM To: "[email protected] <mailto:[email protected]> " Subject: Re: [WIRELESS-LAN] Exclusive 2.4 Ghz and 5 Ghz SSIDs 2, Turn down power on 2.4 GHz so it is at least 3 dB weaker than 5 GHz throughout the coverage area. This is what makes the devices prefer 5 GHz. (It may go without saying given this recommendation, but we configure the AP with a fixed Tx power. RF management only chooses the channel. The benefits of optimizing the power settings of the two radios on an AP easily outweigh the benefits of the crappy power adjustment algorithms used by the AP manufacturers.) ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
