Backhaul
Purely speaking, the meaning of Backhaul word in telecommunications environment is concerned with transporting traffic between distributed sites (typically access points) and more centralized points of presence, in other words, can be defined as the part of a telecommunications networks responsible of establish and manage the connections between a main system with other smaller subnetworks or subsystems.
Applying this concept into a WIFI Mesh ecosystem, Backhaul is the communication way between the Main node and the remaining nodes attached in a mesh network. How good or bad is a WiFi Mesh is totally dependent with the Backhaul efficiency and the Backhaul technology choosed for communicating one node with each, so this concept shouldn’t be overlooked when choosing a mesh system.
Backhaul options?
Once we know the concept meaning, it is time to talk about the different backhaul systems. Depending on the backhaul transmission mode used we can classify the backhaul systems as follows:
- Wired: Backhaul connection is based on a cable between each node. The wire uses Gb Ethernet ports in the far ends and it's able to manage up to 1Gbps Bandwidth. This connection transit independent of the WIFI clients resources so clearly provides a good way to communicate the Mesh nodes between each other as the WiFi interfaces are 100% reserved for users/clients.
- Wireless: Backhaul connection is based on a Wi-Fi link between each node. The backhaul can travel in Wi-Fi 2,4Ghz or Wi-Fi 5Ghz radio bands. We can find two potential configurations for Wireless Backhaul:
- 1) Wi-Fi Shared: The backhaul connections share the front-end resources with the clients attached to the mesh network. It allows saving space in the WiFi devices (they do not have a specific radio resources for Backhauling) but the whole WIFI performance is shared between real clients and the nodes, so that, lower final users performance would be expected. This solution was adopted by Google Wi-Fi and this kind of devices are commonly called as “Dual-Band”.
- 2) Dedicated Wi-Fi : The backhaul connection takes place in a specific radio link interface, used exclusively to communicate any node with any other. It requires more hardware resources (i.e. Power amplifiers, Front-ends, radio filters, Wi-Fi antennas) but provides a clear and efficient communication solution, where the clients (real users) are attached in a different network (entirely used for clients) than the Wi-Fi nodes communication link, so better global performance is expected for users and also for Backhaul. Finally, it is important to highlight than in this case, the dedicated backhaul uses Wi-Fi 5Ghz radio band due to the high link speed capacity that this band is able provide. This is the solution used in Asus Lyra, Linksys Velop, Netgear Orbi and it is commonly called “Tri-Band” since there is two radio bands dedicated for Users and other additional band, the third, dedicated for Backhauling.
Now it is time to discuss about the capacity for each solution. Normally speaking, the Wi-Fi solutions come with a capacity code indicator such as AC2200 or AC3000. This code mention the highest protocol supported (in this case Wi-Fi 802.11ac) and the radio links capacity (adding 2,4Ghz and 5Ghz radio bands). To an easy understanding, let's go with a sample:
AC3000
- Best protocol supported is 802.11ac.
- Wi-Fi 2,4 capacity: 200 Mbps per antenna x 2 Antennas: 400 Mbps
- Wi-Fi 5 capacity: 433 Mbps per antenna x 6 Antennas: 2598 Mbps
- Total: 400+2598 = 2998 ~3000 Mbps
So we can now evaluate the numbers and general Wi-Fi device capacity but we also already know than depending on the Backhaul technology used, not 100% of the capacity is used for clients. In general terms, we can find in the market two Wi-Fi mesh solutions as I mentioned:
- Dual Band: Generally comes with a 2x2 Wi-Fi 2,4Ghz + 2x2 Wi-Fi 5Ghz in each node, so the total capacity is AC1200. As we saw above, dual band does not have a dedicated backhaul so that the 1200Mbps of Bandwidth manageable by the system is shared between Clients and Network nodes.
- Tri Band: We can find AC2200 or AC3000 versions depending on the antennas configuration. For AC2200, we have 2x2 Wi-Fi 2,4Ghz + 2x2 Wi-Fi 5Ghz subsystem dedicated for clients (1200Mhz) and 2x2 Wi-Fi 5Ghz dedicated exclusively for backhaul. In AC3000, the most common configuration is 2x2 Wi-Fi 2,4Ghz + 2x2 Wi-Fi 5Ghz subsystem dedicated for clients (1200Mhz) and 4x4 Wi-Fi 5Ghz dedicated exclusively for backhaul.
