Oct
08

Once I catch my breath and look back at one of our popular INE courses like the CCNA Wireless course, I can delve a bit deeper into certain subjects that we did not have time for in the course. This is one of those moments. Let us get more detailed about Cisco’s implementation of Radio Resource Management (RRM) in the Cisco Unified Wireless Network architecture.

Radio Resource Mangement

Radio Resource Mangement

In today’s wireless LAN infrastructures, of course users want more and more bandwidth in a greater and greater coverage area. This is tricky to implement, however, since adding more and more powerful access points can actually do more harm than good for throughput. The goal of Cisco’s Radio Resource Management is to act like a Radio Frequency engineer built-in to the equipment. RRM allows the Cisco Unified Wireless equipment to continuously monitor the Radio Frequency environment and adjust things like channel assignments and and power levels to ensure optimal coverage and throughput. The exciting goal here is to make the wireless infrastructure “self-healing”.

Here is how Cisco RRM works from a high level:

  • Wireless LAN Controllers (WLCs) are provisioned with a consistent RF Group Name. This is an an ASCII name to identify those WLCs and APs that are all part of the same wireless system.
  • APs periodically send out RRM Neighbor Messages to each other that are passed up to the Wireless LAN controllers as well. These messages are authenticated for security purposes and provide the controllers with a complete picture of all of the devices in the RF Group. From these devices an RF Group Leader is elected.
  • Note that these RRM Neighbor Messages play a critical role in other Cisco Unified Wireless Network capabilities such as Over-the- Air Provisioning (OTAP) and Rogue AP Classification.
  • Once the RF Group is understood, a series of algorithms are run to optimize AP configurations in the RF Group. It is the RF Group Leader that is responsible for these periodic math assignments. (This sounds like a great job for our own Petr Lapukhov!)
  • You should also note that RRM with its RF Grouping is seperate and disctinct from Mobility Grouping.

What are the algorithms that the RF Group Leader will be busy with?

  • Dynamic Channel Assignment Algorithm – using metrics of load measurements, noise, interference, signal strength
  • Transmit Power Control Algorithm
  • Coverage Hole Detection and Correction Algorithm

These are facts we should know about RRM at the CCNA Wireless level. Be sure to use the CCNA Wireless category drop down list here on the blog for more great articles on this exciting field of Cisco networking.


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