Removing the Mystery of Radio Frequency

By  Chris Kozup, Senior Manager, Mobility Solutions, Cisco — April 25, 2010

As business reliance on wireless networks increases so, too, does the need for effective and simple tools to manage the wireless spectrum. A mastery of the radio frequency has traditionally fallen beyond the grasp of the typical IT skill set.
Yet, without an awareness of the importance of a clean and optimized RF spectrum, the business reliance on mobile applications is sure to suffer. With advancements in spectrum intelligence and spectrum management, including interference detection and mitigation, dynamic radio provisioning and improved wireless antennas and silicon, IT organizations now have the tools needed to build and operate high performance wireless networks without extensive RF engineering skills.
Understanding the tools available and how to use them is paramount to preparing for the growth of mobile devices and applications. This article will explore the available tools that can help IT prepare for this increase in mobile devices and applications, and ensure that wireless network performance is optimized for seamless application delivery.
Removing the Mystery of Radio Frequency
As wireless LANs become more critical to delivering core business applications, IT requires that these wireless networks be reliable, yet simple to maintain. The good news is that wireless LANs have evolved significantly over the years. Predicting radio frequency performance was once an art, but has now become a science.
Wireless systems automate much of the management and provisioning of the wireless network. This automation combines enhancements in automated spectrum management, interference capabilities and device optimization to remove much of the complexity and guesswork from wireless operations and frees resources for other activities.
Automated Spectrum management Controller-based wireless LANs offer a system-level approach to wireless management, improve operations, offer robust wireless security, and enable enterprises to support wireless applications that are critical to their daily business functions.
Spectrum management creates an environment that is completely self-configuring, self-optimizing, and self-healing and simplifies wireless operation through the following capabilities:
  • Dynamic channel assignment
  • Interference detection and avoidance
  • Dynamic transmit power control
  • Coverage hole detection and correction
  • Client and network load balancing
An important part of spectrum management is the system's ability to dynamically adjust access point settings based on the environment. Network managers should look for solutions that can dynamically change the access point channel based on the following parameters:
  1. Noise -- limits signal quality at the client and access point and reduces the effective cell size. By choosing a system that can avoid noise sources, enterprises can optimize coverage while maintaining system capacity. If a channel is unusable due to excessive noise, that channel can be avoided.
  2. Utilization -- Choose a system that can assign channels to the access points that require the most bandwidth (for example, a lobby versus an engineering area).
  3. Client load -- Choose a system that changes channels to improve the performance of the network or correct the performance of a poorly performing access point. An effective load balancing system should constantly monitor channel assignments in search of the "best" access point.
  4. Interference -- A system that monitors for interference is critical to maintaining network performance. "Interference" is defined as any 802.11 or non-802.11 traffic that is not part of the Wireless LAN system, including a rogue access point, a Bluetooth device, cordless phone, microwave oven, or a neighboring Wireless LAN.
Choose a system that will constantly scan all channels looking for major sources of interference and can rearrange channel assignments to increase system performance in the presence of the interference.
This increases the capacity of the network by limiting the sharing of frequencies and is especially useful in high-rise buildings.
RF Interference Solutions
RF interference causes performance problems in up to 54% wireless networks1 and can lead to slow performance or dropped service. Because Wi-Fi operates in a shared, unlicensed spectrum, integrated RF interference solutions are a "must have" to enable a high level of performance, security, and reliability in a Wi-Fi network.
Integrated interference solutions provide 24/7 proactive responses to interference, as well as remote management and automated mitigation. Interference solutions make it possible to visualize where interference is occurring in a network and which access points and clients are most likely to be affected by the interference.
Visual mapping displays can enable network managers to see interference devices on the map (as well as their zone of impact), allowing them to determine which access points, clients, and areas of their floor space are impacted.
Network managers can then identify native devices and foreign interferers and determine whether to manually remove the device or configure the Wireless LAN to automatically change the channel away from the interference.
Network managers should look for an RF interference solution that provides:
  • The source of interference
  • The location of the interference
  • Real-time and historical views of interference as well as the impact to the Wi-Fi network
  • Remote access to monitor and configure the network
  • The actions required to mitigate interference and enforce policies
Interference detection helps at every stage of a Wi-Fi deployment, including planning, operations and troubleshooting.
Client Performance
Over the next few years Wi-Fi networks will transition to 802.11n technology. During this time many networks will support a mix of 802.11a/g and 802.11n clients. Because they operate at lower data rates, the older clients can reduce the capacity of the entire network. When evaluating 802.11n solutions, it is important to evaluate how 802.11a/g clients will operate in mixed-client networks.
Enterprises should look for a solution that guarantees improved bandwidth and throughput for all clients on the network -- including newer 802.11n devices as well as existing 802.11a/g devices.
More Efficient Problem Resolution and Reduced Travel
Rather than managing interference on one access point at a time, look for a system that aggregates the impact of interference across the entire network. It should be able to provide both real-time and historical views of interference across controllers, with reports on performance and the flexibility to remotely reconfigure access points to act as sensors that analyze RF.
Ideally look for a system that can detect interference while simultaneously serving network traffic, and especially important is a system that can identify and classify a variety of different types of interference types, including non-Wi-Fi wireless transmissions. Historical reports are key for tracking long-term organizational trends, including the location and use of non-Wi-Fi devices that may impact your network.
By using historical reports you can proactively monitor and prevent problems before they occur. There will always be cases where it is desirable to look at real-time, raw spectrum data to help with a difficult-to-diagnose interference problem. Especially if the type of interference is a rare RF source that is not included in standard classification lists.
Network administrators should look for a system that allows remote access points to be configured as a sensor to collect raw spectrum data for further analysis. Also ensure the system can be monitored and managed from a remote location, this will reduce travel and help resolve interference problems more quickly.
Effective Policy Enforcement
Enforcing policies to prohibit devices that interfere with the Wi-Fi network has been a challenge. 2.4-GHz cordless phones can disable handheld scanners that are used for inventory tracking in retail environments. College campus networks become unusable when Xbox games are active.
Look for a system that provides the ability to track network performance, locate and see the impact of interference and allows you to effectively enforce policies that prevent known interference sources from jeopardizing network security or taking down the network.
Choose a system where you can view security-impacting devices on a map and configure customized alerts based on device or location. This is a very important since certain devices may be considered a threat in some areas of your building (for example, in trading wing), but not in other areas, such as the building lobby.
As wireless continues to grow as a strategic resource for business operations, it is critical that network administrators take into consideration real-time spectrum management, interference detection and mitigation, and client performance when planning an enterprise Wireless LAN design and maintenance strategy.
Network administrators should look to a centralized and dynamic Wireless LAN system to addresses the security, deployment, management, and control issues that enterprises face, informed by rich spectrum intelligence data. With these tools network administrators can prepare for the growth of mobile devices and applications, and ensure that their wireless network performance is optimized for seamless application delivery.
1 Survey of 600 Cisco customers 
Chris Kozup is Senior Manager, Mobility Solutions at Cisco.


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