• We recently moved to 40Mhz channel width on our 5Ghz radios for our Cisco APs (which associate to 4 WiSM controller blades in our 6509 routers.) Since then, some users are not able to connect to the 5Ghz, due to their long distance from the nearest AP. I manually raised power levels on the 5Ghz radios and this helped. It seems that Cisco RRM should have done this for me, but I am finding manual adjustment necessary. Have not heard back from Cisco TAC on my case about RRM not adjusting the power levels.

    After attending the "CWNP - Understanding Wireless LAN Coverage Issues" webinar, I am wanting to explore what other factors can be affecting 5Ghz performance (after changing to 40 Mhz channel width. ?

  • By Howard - edited: July 22, 2016

    There has been quite a lot of talk about various RRM's not working optimally.

    Take a look at the following CWNP post and Devin's Webinar on the subject.  The link is included towards the bottom of the responses.

    I am betting that you need to manually set some upper and lower power limits - overriding the Cisco defaults.

    40 MHz wide channels also require a better SNR, and wider channel separation. 

  • I just read the abridged Troubles Shooting and Design section of the CWNA-106 book, available free from Aerohive, and found it to be very valuable for a project I just started.   However, one section might be a little misleading.

    Although MIMO  AP's might be useful in NEW warehouses, by themselves they won't help much in old ones.

    The reason is that devices that are heavily used in warehouses, like bar-code scanners, and label printers, have extremely low  throughput requirements.   No matter what rate is used with them, they scan or print at exactly the same speed from 2 Mbps on up.   They run just fine at the low /b rates.

    Consequently, most users don't want to replace these devices, which can with care, last for a decade.   Some locations have hundreds of these, and so we are talking about tens or hundreds  of thousands of dollars to replace them (with a MIMO capable version).

    In these cases, using the original in-place directional antenna design will continue to work just fine for many years.

    I enjoy streaming video as much as anyone, but printers and scanners don't use, or need, streaming.

    If you're building from scratch, I'd say go for it (i.e. MIMO clients and AP's ).  Otherwise review your needs very carefully. 

    I recognize that it is getting harder to buy, or even find, /b radios -  but don't think that higher rates will necessarily make your shop run any faster or smoother. 

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