By: Ahmer Bhatty, Network Engineer and Chris Saso, SVP of Technology

A couple of years ago Dasher began offering products and services to support the growing demands of the mobile workforce.  Our engineering team has learned a few things during that time so we thought it would be a good idea to have one of them share some lessons learned.  So, Ahmer Bhatty – take it away…

wireless network considerations DasherWireless – Most wireless networks and devices today use radio frequency (RF) technology to transmit data and certain types of devices use different RF sections or “bands” for transmission. Wi-Fi equipment has been allocated by international governing bodies to use certain unlicensed sections of the RF spectrum – specifically at 2.4 and at 5 GHz – for its operation. Being unlicensed, these bands are shared between a variety of different types of devices and are the only section of the spectrum where they are legally allowed to transmit RF signals. In environments like offices, warehouses or high-tech residences, where several wireless devices vie for the same spectrum space to communicate; interference is a common occurrence causing networks to become slow, drop connections or crash.

 Wireless Trends- Dasher has seen our clients move from all wired networks to a hybrid of wired and wireless networks and in some cases we have deployed all wireless offices for our clients – no LAN ports in offices!  The biggest issue with wireless is to find out what you don’t know first before you decide on a strategy.

 Key considerations and Lesson learned from wireless assessments:

  • Common sources of interference: In the common corporate environment, interference is typically found on the 2.4GHz spectrum.   Channels 1, 6 and 11 are the only non-overlapping channels in this spectrum. Typical sources of interference and thus service disruptions are:
    • Microwaves
    • ZigBee (2.4 GHz radio frequency)
    • Soundcast Audio
    • Bluetooth
    • Other wireless networks in your building
  •  Know your signal bandwidth: Because 802.11n signals are 40 MHz wide, there is not enough spectrum width for two co-located APs to operate freely in the 2.4 GHz band. The best option for this scenario is to limit the width to 20 MHz each on channels 1, 6 and 11 or upgrade all the equipment to 5 GHz 802.11n, where more spectrum width-and more channels-are available.  The 5 GHz band contains 24 non-overlapping channels which gives it a significant advantage over the 2.4 GHz band’s three. With more channels to choose from, interference avoidance is as simple as choosing an unused channel. Additionally, fewer electronic devices use 5 GHz, meaning Wi-Fi access points operating in this frequency range have less RF signals to battle against.
  • You need Spectrum graphs to see what is going on: These graphs can provide a real-time analysis of the 2.4GHz and 5GHz channels. Any interference that is caused on any of the channels from different sources can easily be seen on the spectrum graphs. Here are some Spectrum graphs to give you an idea of what we are talking about:

Graph1The graph above shows the interference of radio devices across different channels and its utilization.  Bluetooth can be seen causing a 64% interface throughout all the channels in the 2.4 GHz spectrum, while Soundcast Audio is seen occupying Channel 11 and utilizing 45%.

Graph2In the second graph, ZigBee and Soundcast can be seen occupying Channels 10, 11, and 12 at different points in time.

  •  Noisy neighbors: We literally mean, your next door neighbors whom you share a physical wall with!  When companies are located in dense areas, then there are bound to be conflicting channels considering that there are only a limited number of channels available to use.  During the wireless assessment, one should be aware and  understand what channels should be utilized so that performance is not compromised.
  • Band steering between 5GHz and 2.4GHz: Band Steering allows clients that are capable of operating in 5GHz mode to be shifted from the 2.4GHz to 5GHz radio by the access points, which can help increase performance of the wireless network.
  • User Density and sizing devices per user and users per AP: It is critical to analyze the density of the users so that the proper quantity of access points can be placed throughout the office. Depending on the user density, some specific types of access points might be better suited for the environment.
  • Load Balancing: This feature is beneficial to prevent one access point from being overloaded while the other access point is idle. It is not necessary to have this feature enabled in all cases, but in some situations it can provide a performance boost where both access points are in close proximity to one another.
  • Cloud-based controllers vs. Physical controllers: Cloud-based controllers and physical controllers are two different ways of managing the wireless network. Cloud-based controllers are accessed from anywhere; whereas physical controllers might be more restricted, depending on the security policies enforced.  In some cases if security is a huge concern, a physical controller might be a better solution than a cloud-based controller. A physical controller can become a bottleneck if it crashes because it can take down the wireless network, unless a redundant controller is configured as well.  Cloud-based controllers allow for remote wireless networks without creating dedicated WAN or VPN links to every remote location.  Ultimately, the decision as to which type of controller is best depends on the user preference and the specific needs of the company.

All of our wireless projects start with an end-to-end assessment and produce a detailed report.  Please contact Dasher for a sample report.

Further Reading:
Going Wireless in the Data Center