Lets take the example of an Wi-Fi access point in the home serving Wi-Fi clients such as mobile phone, notebooks or set top box.

  

Here is a block diagram of Wi-Fi subsystem found in typical access points.

As Wi-Fi packets propagate over the air, signals are detected by the antenna. With 11ac these signals are modulated at the PHY layer using sophisticated techniques ranging from 64QAM to 256QAM.  Higher order modulation means more bits can be packed for a given transmission resulting in increased throughput. Due to the laws of physics there is higher probability of EVM (Error Vector Magnitude) at higher order modulations which is one of the reasons modulation drops as the clients move farther away from the access point. 

Next, MAC framing occurs which packetizes data into IEEE 802.11 format, which can reach up to 2364 bytes.  Since the wired world is based on IEEE 802.3 a protocol conversion occurs from .11 to .3. In 11ac this conversion occurs in the MAC, in 11n this is processed in the host CPU. To make the most efficient of data transfer across the PCI-e bus, frames are aggregated and sent out in large bursts. 

The processor DMA’s frames into DRAM. If the AP is configured in bridged mode, MAC table lookup occurs at the bridge layer and forwards frames to the ethernet interface.   If the access point is configured in router mode a route look up is done and send packets to the destination address.