The Major IEEE 802.11-2020 Ratified Amendments

Robert J. Ditzig
IEEE802.11

802.11 - Legacy - DSSS

  • Channel Width: 22 MHz
  • Spatial Streams: Single Stream
  • Data Rates: 1 and 2 Mbps

The first standard for wireless local area networking, utilizing DSSS modulation to transmit data at relatively low speeds.

802.11b - “Wireless LAN” (1999)

  • Spread Spectrum Technology: HR-DSSS (High-Rate DSSS)
  • Channel Width: 22 MHz.
  • Spatial Streams: Single stream.
  • Data Rates: 1*, 2*, 5.5, and 11 Mbps. * = mandatory

802.11a - “WLAN for 5 GHz band” (1999)

  • Spread Spectrum Technology: OFDM (Orthogonal Frequency Division Multiplexing).
  • Channel Width: Typically, 20 MHz.
  • Spatial Streams: Single stream.
  • Data Rates: 6*, 9, 12*, 18, 24*, 36, 48, and 54 Mbps.

802.11g - “Higher data rates in the 2.4 GHz band” (2003)

  • Spread Spectrum Technology: ERP-OFDM and DSSS (mandatory)
  • Spatial Streams: Single stream.
  • Data Rates:
    • DSSS: 1, 2, 5.5, and 11 Mbps
    • OFDM: 6, 12 and 24 Mbps are mandatory
    • Also supported: 9, 18, 36, 48, and 54 Mbps.
  • The 802.11g amendment mandates support for both DSSS and ERP-OFDM. ERP-OFDM and DSSS technologies can coexist within the same network but use different modulation techniques, requiring a protection mechanism (such as RTS/CTS) to prevent interference and ensure proper communication.

802.11n -  Wi-Fi 4 | "High throughput (HT)" (2009)

  • Frequency Bands: 2.4 GHz and 5 GHz.
  • Data Rates: Up to 600 Mbps.
  • Technologies: MIMO and OFDM for enhanced performance via multipath effects.
  • Throughput: Supports aggregate throughput above 100 Mbps through PHY and MAC enhancements.

802.11ac - Wi-Fi 5 | "Higher throughput using Very High Throughput (VHT) technology" (2013)

  • Frequency Band: 5 GHz.
  • Channel Widths: 20 MHz, 40 MHz, 80 MHz, and 160 MHz.
  • Modulation: 256-QAM, offering up to a 30% speed increase over previous methods.
  • Spatial Streams: Up to eight (early implementations typically support up to four).
  • Maximum Data Rate: 6933.3 Mbps.
  • Beamforming: Supported for improved signal strength and reliability.
  • Backward Compatibility: Compatible with 802.11a/n in the 5 GHz band.

802.11ax - Wi-Fi 6 | "Highest speed ever achieved by Wi-Fi" (2021) - (HE) High Efficiency

  • Frequency Bands: 2.4 GHz and 5 GHz (with optional support for 6 GHz in Wi-Fi 6E).
  • Channel Widths: 20 MHz, 40 MHz, 80 MHz, 160 MHz.
  • Modulation: 1024-QAM, offering higher data rates than previous standards.
  • Spatial Streams: Up to eight.
  • Maximum Data Rate: 9.6 Gbps.
  • Technologies: OFDMA and MU-MIMO for improved efficiency and capacity.
  • Backward Compatibility: Compatible with previous 802.11 standards.

 

802.11af - “TV White Space (TVWS)” (2014)

  • TV White Spaces (TVWS) Operation," is an amendment to the IEEE 802.11 family of wireless networking standards. It focuses on utilizing unused TV spectrum, also known as TV White Spaces (TVWS), for wireless communication.
  • Utilization of TV White Spaces (TVWS): The primary objective of 802.11af is to leverage the unused spectrum in the TV bands (typically between 54 MHz and 698 MHz in the United States) for wireless communication. This allows Wi-Fi devices to operate in frequencies previously reserved for television broadcasting, thereby increasing available spectrum resources for wireless networks.
  • Dynamic Frequency Selection (DFS): To prevent interference with existing TV broadcasts and other licensed users of the spectrum, 802.11af devices employ Dynamic Frequency Selection (DFS) mechanisms. DFS enables Wi-Fi devices to detect and avoid active TV transmissions and radar signals in the vicinity, ensuring coexistence with incumbent users and compliance with regulatory requirements.
  • Transmit Power Control (TPC): The standard includes Transmit Power Control (TPC) mechanisms to adjust the transmit power of Wi-Fi devices dynamically. TPC helps ensure that Wi-Fi transmissions remain within permissible power levels, minimizing interference with other users of the spectrum and improving spectral efficiency.
  • Channel Bonding and Channelization: 802.11af supports channel bonding and channelization techniques to maximize spectrum utilization and increase data rates. By combining multiple TV channels or dividing them into smaller subchannels, Wi-Fi networks can adapt to varying channel availability and network requirements, optimizing performance in diverse environments.
  • Geolocation Database Access: In some regulatory domains, 802.11af devices may be required to access geolocation databases to determine available TVWS channels and ensure compliance with local regulations. These databases provide information about TV broadcasts, wireless microphone usage, and other licensed services in the area, enabling dynamic spectrum access and coordination among different users.
  • Coexistence Mechanisms: The standard specifies coexistence mechanisms to mitigate interference between 802.11af devices and other users of the TVWS spectrum, such as TV broadcasters, wireless microphones, and radar systems. These mechanisms include spectrum sensing, contention-based access, and coordination protocols to ensure fair and efficient spectrum sharing.

802.11ah - “Sub-1 GHz operation” (2016)

  • Focuses on providing connectivity for the Internet of Things (IoT) and other low-power, wide-area (LPWA) applications in the sub-1 GHz frequency band.
  • Sub-1 GHz Frequency Band: One of the distinguishing features of 802.11ah is its operation in the sub-1 GHz frequency band, typically between 900 MHz and 950 MHz. This lower frequency band offers extended coverage compared to higher frequency bands used by other Wi-Fi standards, making it suitable for IoT applications that require long-range communication and penetration through obstacles.
  • Extended Range and Coverage: 802.11ah is optimized for extended range communication, allowing devices to communicate over distances of several kilometers, depending on environmental conditions and transmit power levels. This enables connectivity in rural areas, outdoor environments, and indoor settings with challenging RF conditions.
  • Low Power Consumption: The standard incorporates power-saving mechanisms to minimize energy consumption in both the access points (APs) and client devices. By optimizing sleep modes, wake-up schedules, and data transmission intervals, 802.11ah supports battery-operated devices with long operational lifetimes, making it suitable for IoT deployments and other low-power applications.
  • Support for Dense Deployments: 802.11ah is designed to support a large number of devices within a single network infrastructure, making it suitable for deployments with high device density. The standard includes mechanisms for efficient channel access, network coordination, and scalability, ensuring reliable communication in environments with thousands of interconnected devices.
  • Improved Indoor Penetration: Due to its lower frequency operation, 802.11ah signals exhibit better penetration through walls and other obstacles compared to higher frequency Wi-Fi standards. This enables reliable communication in indoor environments with complex layouts and obstructions, enhancing coverage and connectivity for IoT applications.
  • Backward Compatibility: While 802.11ah introduces new features and optimizations, it is designed to ensure backward compatibility with existing Wi-Fi standards. This allows for seamless integration of 802.11ah devices into heterogeneous wireless networks, enabling interoperability and coexistence with legacy Wi-Fi devices.
  • Security Enhancements: The standard includes provisions for enhanced security mechanisms, such as improved encryption algorithms and authentication protocols. By addressing security concerns, 802.11ah helps protect IoT networks and sensitive data transmitted over wireless connections.

802.11ad - “Gigabit-class wireless local area network 60 GHz Band” (2012)

  • Enhancements for Very High Throughput in the 60 GHz Band
  • Very High Throughput: Supports data rates of up to 7 Gbps making it suitable for applications such as uncompressed HD video streaming, fast file transfers, and high-performance computing tasks.
  • Short Range Communication: Range is limited to within a room or between adjacent rooms. However, this short range is offset by the high data rates achievable over this distance.
  • Directional Communication: 802.11ad devices often use directional antennas to focus signals, improving communication reliability and reducing interference. This is particularly useful in environments with multiple devices or in scenarios where line-of-sight communication is required.
  • Backward Compatibility: While 802.11ad operates in a different frequency band, it is designed to be backward compatible with existing Wi-Fi standards like 802.11a/b/g/n/ac. This enables seamless integration with existing Wi-Fi networks, allowing devices to switch between frequency bands as needed for optimal performance.