Getting traffic received from clients out to the rest of the network is an important aspect when designing any Wi-Fi network. There are multiple backhaul options, each with its own set of Pros and Cons.
Wired connection to each AP: The simplest option when available, the wired connection provides both data backhaul as well as Power (PoE) to the Access Point. Typical in most indoor deployments where a PoE switch (such as the cnMatrix line of switches from Cambium) in the wiring closet provides this to the various APs. Also popular in hospitality where hotel rooms might have in-wall wiring already where wall-plate access points can be plugged in.
Wi-Fi mesh from an AP to another: A quick and easy way to extend coverage where cable run may not be possible. One advantage is the backhaul can fail over easily (if one upstream AP is down, the mesh node can find another one and restore the connection). Downside is a throughput drop as the mesh radios have to be on the same channel. Each additional mesh hop results in capacity falling by ~40%.
Dedicated Fixed Wireless Access: Using a ePMP or a PMP subscriber module connected to the ethernet port of the AP can provide a wireless backhaul connection that is more reliable than a Wi-Fi mesh connection. Advanced traffic control is now possible and there is greater flexibility in the available frequencies to be used for the backhaul. Also, this frees up the Wi-Fi AP radios to focus on client service instead of sharing time/bandwidth for mesh at the same time. To ease the cable management in such deployments cnPilot outdoor Enterprise APs support PoE-out on the auxillary ethernet port. This way the SM can be connected to the Eth2 port of the AP, and be powered off that port, without needing a separate PoE-injector and power connection for it.
While these are the typical backhaul connections at a physical level, there are also a possibility of encapsulating user traffic in higher level protocols if required. By default the APs bridge out Ethernet frames corresponding to the 802.11 data frames, however in some cases the VLAN may not be available at the APs ethernets port and there may be a need to transport these frames encapsulated to a central concentrator device. For this the cnPilot APs support three traffic tunnel options that can be configured: L2GRE, L2TP, PPPoE.