Wireless Mesh

I get a lot of questions asking if someone should use range extenders, repeaters, or mesh to add coverage to an area that is not being covered by an existing wireless network. The question can come from two very different places, enterprise or home network admins.

The answer is usually different for either case. In this blog, we will give a quick explanation of wireless mesh technology to help you decide what would work best for your situation.

Wireless Mesh is a technology that allows wireless access points to pass backhaul traffic using wireless radios instead of a physical cable. This is useful when an access point needs to be placed in a location where connecting it to the wired LAN is impractical.

In a mesh network, access points connect to the LAN using only the radios. As always, there are pros and cons to using mesh. When you need an AP in a location that you can't cable, mesh is excellent. But because of the overhead involved, mesh should be used only where and when necessary.

Usually, an access point would connect to the LAN via an Ethernet cable for both power and data. The AP would use its radios (2.4 and 5 GHz) to broadcast a wireless network, and client devices would connect to whichever band the client device preferred. There is no wired path from the AP to the network in a mesh network, so the path is built using one of the wireless radios.

There are almost as many ways to implement mesh as there are AP manufacturers. Some will operate the mesh on the 5 GHz radio while still allowing client access through the same radio. Some will dedicate one radio for the mesh link. The ideal mesh radio will have a separate radio devoted to the mesh while allowing other radios to serve clients, usually called a tri-band or tri-radio AP.

Let's talk about why this all matters. Wi-Fi is a half-duplex technology, which means that only a single device can be transmitting at any one time, including the mesh backhaul.


Imagine this; you are out hiking with two friends Alice and Bob. Each is in a canyon while you are on a ridge between them. You can hear each of them, but they cannot hear each other. You would need to relay a message from Alice to Bob. When you do this, you need to first listen to Alice, then speak to Bob. Alice and Bob's conversation takes twice as long since you have to 'queue' the data and retransmit it. This is how mesh works. Now add in a few more hikers that are only speaking with you up on the ridge, and you cut the amount of time you can dedicate to Alice and Bob even further. These are clients being served by the 5 GHz radio that is also the mesh radio.


The point is each hop has a cost associated with it. Today's smart mesh systems can build and heal themselves based in part on these costs. Thus, it is essential to design a mesh network with as few hops to a root AP as possible.


A typical mesh requirement is parking lot coverage. It may be cost-prohibitive to run copper of fiber to a few points in a parking lot for AP's. A mesh network could be built to accommodate access points installed on light poles. Power could be tapped from the light sensors, and the AP's could mesh to AP's hung on the exterior of the building. In this case, it would be essential to limit the access points participating in the mesh to only those required.

On some enterprise wireless LAN controllers, turning on mesh enables it on ALL access points. As you might imagine using mesh on every AP when all but a handful need it is not a good idea.


There are a whole host of things that are introduced when mesh is enabled on a WLAN. Hidden SSID's, encryption, All AP's in a mesh group need to be on the same channel. In other words, if you have 100 AP's and you enable mesh, your system could put every AP on the same channel.



That covers enterprise mesh; let's touch on Repeaters, Boosters, and Range Extenders.

Each of these are descriptions of the same type of device. Depending on the manufacturer, they will operate in slightly different ways. Some will use a single radio to connect to an existing wireless network in the same way a client device would then rebroadcast the same (or a different) SSID. Some will use two radios to separate the 'client' connection and the 'backhaul' connection.

These types of devices can be inexpensive relative to mesh solutions. But in this case, you get what you pay for.

In operation, an extended or repeated network might require your client device to be reconnected to the network each time you travel from one area to the next; this is not true roaming. Mesh networks allow a client device to roam between access points seamlessly (usually).

Repeaters, boosters, and extenders are considered consumer-level products. Not to be used anywhere but in a home setting, and even then, I would think twice about it.

Recently a few manufacturers have put out some decent home mesh products. Again, since these devices don't have to adhere to any wireless specifications, they operate differently. Look for descriptors like tri-band or three radio, or separate backhaul. Anything that would indicate that the mesh link is dedicated to backhaul and not client service.

I hope this adds some clarity to a sometimes confusing tech subject.


-WirelessKahuna



Links to consumer mesh solutions:


Eero Mesh - Google Nest Wi-Fi - Orbi RBK852 - Linksys Velop - Xfinity xFi Pod


Terms:


Access Point - a single piece of hardware that communicates with client devices to connect them wirelessly to a network (operates as both AP and STA)

Backhaul - Data path between nodes. Nodes may be single radios or groups of radios. Sometimes used to refer to the connection to the internet.

BSSID - Basic Service Set Identifier - Identifies an SSID on a specific radio when the wireless network spans multiple AP’s

Client Device - any device that connects to a wireless network - smart phone - laptop - IoT (operates as STA)

Half Duplex - Data transmission that can occur in both directions but only in one direction at a time

Hop - a single mesh link. Limit the number of hops a mesh radio is away from the root AP

LAN - Local Area Network - the wired network, generally limited to a single building or small geographic area. Everything ‘inside’ of the gateway

Non Root - A meshed AP that is not connected via Ethernet to the LAN (also MAP)

Radio - Access Points use radios on different bands 2.4 or 5 GHz to provide the wireless part of the connection

Repeater/Booster/Range Extender - Devices used to connect to and repeat an existing wireless network - NOT mesh technology

Root - An AP that is part of the mesh network that is wired to the LAN (also RAP)

SSID - Service Set Identifier - this relates to the name of a wireless network

WLAN - Wireless Local Area Network