Roaming is increasingly becoming an important factor in WiFi network deployment, and we're not talking about cellular roaming. Any WiFi access point has a limited range, and if your employees are moving around a lot in their job while using WiFi devices, roaming becomes an issue.
Strictly speaking, "roaming" occurs whenever a client device switches from one WiFi access point to another. Ideally, this happens seamlessly - although, of course, that's easier said then done.
So let's look at some of the issues surrounding wireless roaming in Cisco Meraki systems and network topographies that enable it.
How Wireless Roaming Works
In practice, WiFi roaming works pretty much like cell phone roaming. You need overlapping access points so that anyone approaching the edge of one AP's broadcast area is already within range of another AP. Imagine the Olympic Rings, with an AP in the center of each, and you've got the basic idea of what it would look like from a top-down view.
One crucial element is that all of the WiFi APs in the network need to be using the same SSID (network name) with the same login process/credentials. In this situation, the client device should automatically switch from one AP to another with little or no disruption in service.
Much of this has to do with how roaming is initiated on Cisco systems.
Factors That Determine When A Device Roams
In a larger network deploying roaming, the connection to one AP will become steadily weaker as the client moves around. There are several factors -all happening on the client device- that determine when it starts searching for a new AP.
- Lost packets: The system can be programmed with a set number of dropped\retried packets, so that the client automatically searches for a new AP once too many packets drop.
- Missed beacons: APs will broadcast a "beacon" -basically a self-identifier- at set intervals, usually 100ms. If eight beacons are missed in a row, the client initiates roaming.
- Periodic client check: If signal strength is below 50% (default), the client will automatically search for stronger signals and switch to them when found.
- Reinitialization: If the client device is rebooted or has its network toggled on/off, this registers as a "roam" within the network.
Most other brands have similar systems in place for their own network OSes. Additionally, many of these features, like automatic client checks, are becoming standard on most "smart" devices anyway.
Helping Facilitate Roaming In Your Facility
Beyond ensuring a standardized setup for all the APs, the biggest factor in successful roaming is having the proper antennas and signal shapes. While there are many options in antennas, they boil down to two basic types: Directional and Omni-directional.
These are exactly what they sound like. Omni-directional antennas create a roughly spherical "bubble" of coverage radiating outwards with the AP in the center. Directional antennas have a focused beam that's aimed in one particular direction. The beam can be widened or narrowed as needed, usually an arc between 25-80 degrees wide.
The right mixture of directional and omni-directional antennas is vital for proper roaming. Generally speaking, you want omni's in the center of your facilities, with directionals on the outside edges, aimed inwards towards any gaps in the omnis' coverage.
Having a professional assess your facilities and create a Predictive WiFi heatmap can be highly beneficial. While it's possible to do this yourself, a pro will have better tools and more experience. This heatmap will show optimal placements for WiFi APs, based on how employees will actually be moving around and using the system.
Hummingbird Networks has more than a decade of experience building networks large and small, with a particular emphasis on large facilities such as hotels and schools. For a free consultation on your WiFi needs and best options in AP, just contact us with your questions!