What is a wireless mesh network architecture

Mesh WiFi / Wireless Mesh Network

A WLAN mesh is a comprehensive WLAN in which several access points are connected to each other via WLAN.
In order to have WLAN available everywhere as possible, several access points are set up. However, not every access point needs a connection to the LAN. Several access points can be connected to one another via WLAN to form a wireless network. Each participating access point serves as a node that forwards data packets to the other nodes. This is then called a mesh WiFi. A function called seamless routing ensures that each client connects to the access point in the mesh whose signal can be received the strongest.

In the WLAN standard IEEE 802.11, base stations are referred to as access points. In the mesh world, the term “node” is common and can be viewed as a synonym. A real mesh requires that there are always at least two paths between two nodes. The smallest mesh network therefore has at least three access points.

The term “mesh” should be seen more as marketing and less as a technical term. A real mesh is rarely found in the private sector. For this you would have to set up a few access points that would also have to be within reach of each other. In the professional environment, efforts will be made to connect every access point to the network by cable so that a defined data rate is available at every access point.

Why do you need mesh WiFi?

  • WLAN should be available everywhere
  • Increase the range of an existing WLAN
  • Increase availability through redundancy
  • larger area through the use of many access points
  • Set up and operate an ad hoc network

Basics: Wireless Mesh Networks (WMN)

In a normal WLAN, the WLAN clients only communicate with one access point. In wireless mesh networks, the WLAN stations are meshed with one another. Mesh networks act as multi-point networks in which the WLAN-capable devices in ad-hoc mode serve as relay stations to the nearest access point. Mesh network-capable end devices improve the range of the access point. All WLAN devices can serve as mesh points. So also typical WLAN clients.

In a mesh WLAN, each mesh point forms its own radio cell. While the radio cells rarely touch each other with normal WLANs, this is intentional with mesh WLAN. Here the mesh WLANs are within mutual range. Otherwise they would not form a network. However, usable performance is not possible without changing the access protocol. The reason: neighboring mesh points share a common radio channel. Only one device can transmit within the common radio channel. Every received packet must be cached before it can be sent on. Here you can also see the real problem of mesh WLANs. Interference from simultaneous transmissions is increasing and the CSMA / CA access method is reaching its limits.

Mesh WiFi solutions

Unfortunately, there is not just one technical solution for a mesh WLAN, but rather a large number of different technologies and standards that can be part of a WLAN mesh solution.

  • WDS - Wireless Distribution System
  • WiFi mesh systems or mesh kits with 3 access points
  • WLAN router cascade as a do-it-yourself solution
  • Layer-2-Mesh with BATMAN-Advanced
  • Standard-compliant roaming support (IEEE 802.11k / v / r)
  • IEEE 802.11s / Mesh Deterministic Access

WDS - Wireless Distribution System

WDS is part of the basic IEEE 802.11 standard and describes the wireless connection between several wireless access points. This is the function of a WLAN repeater within a WLAN network.

WiFi mesh systems / mesh kits

Mesh WiFi systems are mostly tri-band systems. They network with each other via a high channel in the 5 GHz frequency range. The WLAN clients supply them via the 2.4 GHz frequency range and a lower channel in the 5 GHz frequency range. These mesh systems constantly have to make complicated decisions.

  • How long should a WLAN client stay in the faster 5 GHz mode?
  • When should a WLAN client switch back to the slower, but longer-range 2.4 GHz band?

In the absence of a cross-manufacturer standard, most WiFi mesh systems from different manufacturers are not compatible with one another. There is no cross-manufacturer function for connecting the mesh systems to one another. Mesh WiFi usually only works with devices from one manufacturer.
A multi-access point specification of the Wi-Fi Alliance is in the works.

WLAN router cascade

If you don't want to get involved with the expensive WiFi mesh kits, you can also work with a WiFi router cascade. This is usually a base station and additional WLAN repeaters or WLAN routers that are configured in repeater mode. The devices are configured in such a way that they are connected in series.
The crux of the matter is that the location of the devices has to be well balanced and the devices have to be configured uniformly. But you have to do everything manually. But you also get the best possible coverage. In addition, individual requirements can also be taken into account.

Layer-2-Mesh with BATMAN-Advanced

BATMAN-Advanced is a routing protocol for wireless ad hoc networks and works on OSI layer 2 or between layers 2 and 3.
The task of this routing protocol is to continuously determine which nodes can currently be reached via which route. BATMAN-Advanced is mainly developed and used in the environment of the Freifunk community. If you want to build such a Layer-2-Mesh, you usually need OpenWRT-capable access points with the corresponding software extension for BATMAN-Advanced.

WLAN roaming with IEEE 802.11k, 802.11v and 802.11r

If the radio ranges of several access points overlap a little, the client can move between the access points without the network connection being interrupted. This functionality is known as roaming. However, the transition takes 100 milliseconds and, depending on the type of authentication, several seconds. Current connections at TCP / IP and application level are interrupted. For uninterrupted WLAN roaming, there are helper functions that are standardized as IEEE 802.11k, 802.11v and 802.11r.

IEEE 802.11s / Mesh Deterministic Access

IEEE 802.11s is a standard for a Wireless Mesh Network (WMN) in which WLAN-enabled devices serve as relay stations for other devices to the nearest access point. IEEE 802.11s regulates how WLAN stations set up a wireless backbone with one another and how they forward frames for the stations outside the radio cell.

Conclusion

Mesh operation in WLAN is nothing really new. Repeater operation with WDS is already provided for in the basic standard of IEEE 802.11. Unfortunately, the implementations of the different manufacturers do not work well together. As early as 2005, the IEEE was working with 802.11s on a specification for meshed radio networks based on WLAN. But that has not spread.
Other proprietary solutions only work with devices from the same manufacturer.

The question is whether you even need mesh WiFi and whether that makes sense? The fundamental technical problems cannot be dismissed out of hand. And every technical solution can only be a crutch. Because the WLAN technology was developed on the basis of one access point and not on the cooperation of several access points. In addition, the operation of a WLAN network with several access points without a central instance makes little sense. Attempts to implement a decentralized mesh protocol can only fail because no mesh functions are required across the board and support for them will therefore only rarely be available. In most cases, the range of a WLAN can be increased with a simple WLAN repeater. If you need more, there are mesh kits with proprietary technology. And for greater ranges you simply have to lay a few cables and connect the access points to a wired local network.

Other related topics:

Product recommendations

Everything you need to know about networks.

Network technology primer

The network technology primer is a book about the basics of network technology, transmission technology, TCP / IP, services, applications and network security.

I want that!

Everything you need to know about networks.

Network technology primer

The network technology primer is a book about the basics of network technology, transmission technology, TCP / IP, services, applications and network security.

I want that!