Specifications

Summit WM20 Technical Reference Guide, Software Version 4.2 87
11 DRM - Dynamic Radio Management
Introduction
WLANs are becoming more common. Usage has grown to require higher user capacities and higher
radio frequency (RF) density. As 802.11 becomes standard for larger networks, network performance
becomes a critical factor in managing the network.
A Site Survey is necessary for installing and configuring large WLAN networks. However Site Surveys
are not sufficient in addressing how the WLAN network will perform over time.
The performance of an 802.11 network depends on how many clients are sharing the network. Larger
numbers of clients require a denser deployment of AP’s. However as AP’s are packed into a smaller
area, they interfere with each other and reduce the overall performance of the network.
Performance also depends on propagation of RF signals. RF signal propagation is affected by other
Access Points, people, and other objects in the coverage area. The RF propagation changes as people
and objects move through the coverage area. Wireless Access Points and Stations have to constantly
adapt to the changing RF environment – generally dropping the connection rate in noisier
environments.
The purpose of RF Management is to dynamically adapt the AP configuration (in most cases, the
transmit power) to changing environmental conditions.
When deploying dense WLAN networks, network administrators face two main challenges:
● dense deployment causing RF interference with neighboring access points residing on the same or
neighboring channels, and;
● RF interference and impedance from changing environments such as the movement of people, the
position of objects in the office, as well as other RF technologies such as Bluetooth, microwave, or
other cordless technologies.
Co-Channel Interference in Dense Deployments
As WLAN installations become more critical to the business infrastructure, they need to be engineered
to address larger numbers of users and better coverage. In these cases, WLAN installations require more
Access Points installed in closer proximity. A dense deployment requires coordinated channel selection
and power management amongst the AP’s.
As APs are deployed in dense environments with overlapping RF coverage, it is impossible to avoid co-
channel interference between APs on the same channel. Co-channel interference causes collisions
between RF data transmissions, which reduces effective throughput. In Voice over WLAN applications,
co-channel interference increases jitter and latency, which can result in audible static during
conversations. For example, co-channel interference is more common in the 2.4 GHz band (802.11b and
802.11g) where there are only 3 non-overlapping channels (1, 6, and 11) in North America.