Wi-Fi is a popular wireless networking technology that allows devices to communicate without the need for physical wired connections. It uses radio waves to provide wireless high-speed internet and network connections. Wi-Fi has seen multiple standard evolutions over the years, each bringing improvements in speed, range, and reliability. Here’s a brief overview of the Wi-Fi standards you mentioned:

IEEE 802.11a:

  • Frequency Band: 5 GHz
  • Maximum Data Rate: 54 Mbps
  • Modulation: Orthogonal Frequency Division Multiplexing (OFDM)
  • It didn’t gain widespread adoption due to its higher cost and the popularity of 802.11b, which operated in the more universal 2.4 GHz band.

IEEE 802.11g:

  • Frequency Band: 2.4 GHz
  • Maximum Data Rate: 54 Mbps
  • Modulation: OFDM
  • It was backward compatible with the earlier 802.11b standard, making it popular. It combined the best of both 802.11a and 802.11b.

IEEE 802.11n (Wi-Fi 4):

  • Frequency Bands: 2.4 GHz and 5 GHz
  • Maximum Data Rate: 600 Mbps (with four spatial streams)
  • Modulation: OFDM
  • Key Features: Introduced Multiple Input, Multiple Output (MIMO) technology, which uses several antennas at both the transmitter and receiver to improve communication performance.

IEEE 802.11ac (Wi-Fi 5):

  • Frequency Band: 5 GHz
  • Maximum Data Rate: Over 1 Gbps (theoretical maximum of 3.46 Gbps with eight spatial streams)
  • Modulation: 256-QAM
  • Key Features: Improved MIMO (up to eight spatial streams), wider channels (up to 160 MHz), and Multi-User MIMO (MU-MIMO) that allows multiple devices to be served simultaneously.

IEEE 802.11ax (Wi-Fi 6):

  • Frequency Bands: 2.4 GHz and 5 GHz (with prospects to move into 6 GHz with Wi-Fi 6E)
  • Maximum Data Rate: 9.6 Gbps (theoretical maximum across multiple channels and devices)
  • Modulation: 1024-QAM
  • Key Features:
    • Orthogonal Frequency Division Multiple Access (OFDMA) for better efficiency in congested environments.
    • Target Wake Time (TWT) for improved device battery life by scheduling when devices wake and sleep.
    • BSS Coloring to help distinguish between overlapping networks.
    • Improved MU-MIMO for both uplink and downlink.

Each subsequent version of the Wi-Fi standard brought technological advancements, aiming to improve the speed, range, and efficiency of wireless networks, as well as to accommodate the increasing number of devices in modern environments.