• Hi

    forgive me for my lack knowledge on this but if someone else out there knows the answer then please let me know.

    does cisco support RRM for 1262 patch antennas?


  • Hi Alan

    On some forums, if you ask a question, there?s often someone living in his mother?s basement who?ll reply ?Don?t you know that ??, in a snidy way. I?ve PM?d some of them in the past with a piece of my mind when they?ve replied to me like that. You won?t find any of those types here. We all have areas that we need to ask questions in.

    Maybe the following will help:

    RRM is usually about setting parameters for the APs ( via the WLC ) that allow the controller to alter power levels for such things as coverage holes, ?co-channel interference? etc. It can take a fair while for some systems to stabilize initially.
    Depending upon device/age etc, some people leave the system on for a day or so to let the algorithm ?build up a picture of the RF environment?. It?s a detailed business, but can be very useful. There are some pitfalls though !! Usually, one of the main things that the system is trying to prevent, is that you transmit power levels that are too high for the particular regulatory domain that you are in.

    In other words, for the US for example, we have rules set by the FCC regarding power levels. If you were to transmit at too high a level ( EIRP ), you could cause interference not only to other Wi-Fi systems, but also to other others ( The ISM band for example, was designed originally for Industrial users, Scientific users and Medical users?.although nowadays, all sorts are using it ).

    A Cisco note says ?The 2.4 GHz and 5 GHz bands used for wireless are not regulated by communications commissions such as the FCC or European Regulators Group?.

    That?s not strictly speaking correct, and gives the wrong impression of what you are allowed to do in a network.

    Although the ISM bands and UNII bands are licence free ( unlike, say a cellular network band ), that does not mean they are unregulated. They are regulated, where the term ?regulated? means that rules apply. There are strict rules put in place so that we do not have a free for all as far as transmit EIRP is concerned .

    We know that EIRP is made up of two components: Firstly the actual physical power which the device can transmit, second, the antenna gain ( cable losses and connector losses to be taken into consideration ). When we connect an AP to a controller, the controller is set up to know the amount of power that a particular model of AP can deliver. Usually, we input a country code at the beginning of our configurations. The controller will then know the regulatory values of the country you are in, from built - in tables. But what about the antenna ? That requires user input to tell the system what the antenna gain is. The controller is more interested in what the actual maximum possible EIRP that can be transmitted with a particular AP/Antenna combo rather than the actual type of antenna used ( although knowledge of the type is very important for other things, such as coverage etc ). What Cisco is most concerned about is that you don't slap on an antenna that in combination with the max possible physical TX power will give an EIRP greater than that allowed for that particular regulatory domain. Despite what is often written in popular literature, the FCC will step in under certain circumstances. For example, if you suspect that someone is using an amp/very high gain antenna and going way beyond FCC limits, and causing severe interference.
    Depending on the controller, you can have some weird and wonderful ways of inputting the antenna gain information:

    From page 29 of the following document ( you can find the appropriate doc for whatever version of software is running on the Cisco website, under ?Wireless?), some info is given:

    c. In the Antenna Gain field, enter a number to specify an external antenna?s ability to direct or focus
    radio energy over a region of space. High-gain antennas have a more focused radiation pattern in a
    specific direction. The antenna gain is measured in 0.5 dBi units, and the default value is 7 times 0.5
    dBi, or 3.5 dBi.
    If you have a high-gain antenna, enter a value that is twice the actual dBi value (refer to the Cisco
    Aironet Antenna Reference Guide for antenna dBi values). Otherwise, enter 0. For example, if your
    antenna has a 4.4-dBi gain, multiply the 4.4 dBi by 2 to get 8.8 and then round down to enter only
    the whole number (8). The controller reduces the actual equivalent isotropic radiated power (EIRP)
    to make sure that the antenna does not violate your country?s regulations.

    Hope that is the sort of thing you are looking for, to get you started.


  • Hi Alan,

    RRM works with patch antennas. Basically RMM consists of three components: Dynamic Channel Assignment, Transmit Power Control and coverage Hole Detection. TPC algorithms' function is to achieve coverage by adapting AP TxPower in such a way, that they surround themselves with 3 other APs at a certain threshold. This also works with semidirectional antennas. Keep in mind in your design that a patch can generate a strong signal in a certain direction.

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