CWNA Chapter 5 – IEEE 802.11 Standards

My Notes from chapter 5 of the CWNA study guide

Original IEEE 802.11 standard

  • The first WLAN standard published.
  • Defined by IEEE at the Physical and MAC layers of the OSI model.
  • The PHY task group worked in conjunction with the MAC task group to define the original 802.11 standard.
  • The PHY task group defined three original Physical layer specifications:
    • Infrared (IR)
      • Uses light-based medium
      • Defined in the original 802.11 standard but is now obsolete
    • Frequency Hopping Spread Spectrum (FHSS)
      • RF signal is considered spread spectrum when the bandwidth is wider than what is required to carry the data.
      • 802.11 radios are also called Clause 14 devices because of the clause that references them
    • Direct Sequence Spread Spectrum (DSSS)
      • Another spread spectrum technology
      • DSSS 802.11 radios are known as Clause 16 devices
  • Either FHSS or DSSS radios can transmit in the 2.4GHz ISM band
  • DSSS 802.11 radios can transmit in channels subdivided from the entire 2.4 GHz to 2.4835 GHz ISM band
  • FHSS radios, which are permitted to transmit on 1 MHz subcarriers in the 2.402 GHz to 2.480 GHz range of the 2.4 GHz ISM band
  • Data rates defined by the original 802.11 standard were 1 Mbps and 2 Mbps regardless of which spread spectrum technology was used
  • A data rate is the number of bits per second the Physical layer carries during a single-frame transmission, normally stated as a number of millions of bits per second (Mbps)
  • Data rate is the speed and not actual throughput

IEEE 802.11-2007 ratified amendments

  • In 2007, the IEEE consolidated 8 ratified amendments along with the original standard, creating a single document that was published as the IEEE Std 802.11-2007
  • 802.11b-1999
    • Now known as 802.11b
    • Physical layer medium that was defined by 802.11b is High-Rate DSSS (HR-DSSS)
    • Operates in the ISM 2.4GHz range
    • Not backwards compatible with legacy 802.11 FHSS devices, but backwards compatible with legacy 802.11 DSSS devices
    • Main Goal to achieve higher data rates in the ISM 2.4 GHz range
    • Complementary Code Keying (CCK) and modulation methods using the phase properties of the RF signal
    • Data rates of 1, 2, 5.5, and 11 Mbps. (1,2 Mbps are the backwards compatible ranges, 5.5 and 11 are known as HR-DSSS)
    • Optional technology called Packet Binary Convolutional Code (PBCC)
  • 802.11a-1999
    • Now known as 802.11a
    • Published the same year as 802.11b
    • Uses the 5GHz spectrum using RF technology called Orthogonal Frequency Division Multiplexing (OFDM)
    • Uses 3 different 100 MHz unlicensed frequency bands in the 5 GHz range, called the Unlicensed National Information Infrastructure (U-NII)
    • 12 channels are available in the original three U-NII bands
    • Operates in the less crowded 5GHz range
    • Supported data rates of 6, 12, and 24 Mbps with a maximum of 54 Mbps
    • With the use of a technology called Orthogonal Frequency Division Multiplexing (OFDM), data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps
    • Can not communicate with legacy 802.11, 802.11b or 802.11g clients, but can co-exist with them as they are both in different frequencies
  • 802.11g-2003
    • Now known as 802.11g
    • new technology called Extended Rate Physical (ERP)
    • Transmits in the 2.4GHz ISM frequency
    • Backwards compatible with 802.11b and 802.11 (DSSS)
    • Two mandatory and two optional ERP physical layers (PHYs) were defined
      • Two mandatory PHYs are ERP-OFDM and ERP-DSSS/CCK
      • Two optional PHYs called ERP-PBCC and DSSS-OFDM
    • Data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps using a PHY technology called Extended Rate Physical DSSS (ERP-DSSS/CCK)
    • No difference between OFDM and ERP-OFDM. The only difference is the transmit frequency
    • When 802.11g was ratified it trigger huge sales in SOHO and enterprise markets because of the higher data rates and the backwards compatibility with older equipment
    • ERP-OFDM and ERP-DSSS/CCK technologies can coexist, yet they cannot speak to each other.
    • protection mechanism that allows the two technologies to coexist, its goal was to prevent the different technologies transmitting at the same time
  • 802.11d-2001
    • added requirements and definitions necessary to allow 802.11 WLAN equipment to operate in areas not served by the original standard
    • Country code information is delivered in beacons and probe responses, this information is used by 802.11d compliant devices to ensure they are abiding by the countries rules and regulations for frequency and power
  • 802.11h-2003
    • Defines mechanisms for dynamic frequency selection (DFS) and transmit power control (TPC).
    • Main reason was to detect and avoid interference with 5 GHz satellite and radar systems
    • Introduced new frequency band called U-NII-2 Extended with 11 more channels
Band frequency range Amendment Channels
U-NII-1 (lower) 5.150 GHz–5.250 GHz 802.11a 4
U-NII-2 (middle) 5.250 GHz–5.350 GHz 802.11a 4
U-NII-2 Extended 5.47 GHz–5.725 GHz 802.11h 11
U-NII-3 (upper) 5.725 GHz–5.825 GHz 802.11a 4
  • DFS is used for spectrum management of 5 GHz channels by OFDM radio devices , used for radar avoidance
  • TPC is used to regulate the power levels used by OFDM radio cards in the 5 GHz frequency bands, the TPC service is used to meet the regulatory transmission power requirements
  • The information used by both DFS and TPC is exchanged between client stations and APs inside of management frames.
  • 802.11i-2004
    • Major security enhancements under 802.11i:
      • Data Privacy
        • Confidentially is addressed by Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) which uses the Advanced Encryption Standard (AES) algorithm
        • 802.11ialso defines an optional encryption method known as Temporal Key Integrity Protocol (TKIP), which uses the RC-4 stream cipher
      • Data Integrity
        • Integrity methods to ensure that the encryption method has not been tamped with
          • WEP uses a data integrity method called the Initialization Check Value (ICV).
          • TKIIP uses a method known as the Message Integrity Check (MIC).
          • CCMP uses a much stronger MIC and other mechanisms
        • The 802.11 frames uses a 32-bit CRC known as the frame check sequence (FCS) to protect the entire frame
      • Authentication
        • Two methods:
          • Pre-shared keys (PSKs)
          • 802.1X authorization framework
            • Extensible Authentication Protocol (EAP), although the 802.11i amendment does not specify what EAP method to use
      • Robust Security Network (RSN)
        • Defines the entire method for authentication, generating encryption keys for clients and APs
    • Wi-Fi Alliance also has a certification known as Wi-Fi Protected Access 2 (WPA2)
      • WPS2 if fully compliant with 802.11i
  • 802.11j-2004
    • Obtain Japanese regulatory approval by enhancing the 802.11 MAC and 802.11a PHY to additionally operate in Japanese 4.9 GHz and 5 GHz bands
    • OFDM channel spacing of 10 MHz, which results in available bandwidth data rates of 3, 4.5, 6, 9, 12, 18, 24, and 27 Mbps
  • 802.11e-2005
    • Layer 2 MAC methods needed to meet the QoS requirements for time-sensitive applications over IEEE 802.11 WLANs
    • The original 802.11 defined two methods to gain control of the half duplex medium:
      • Distributed Coordination Function (DCF)
        • Contention-based method determining who gets to transmit on the wireless medium next
      • Point Coordination Function (PCF)
        • Access point briefly takes control of the medium and polls the clients
        • Never adopted by WLAN vendors
    • 802.11e amendment defines enhanced medium access methods to support QoS requirements:
      • Hybrid Coordination Function (HCF)
        • Has 2 access mechanisms to provide QOS:
          • Enhanced Distributed Channel Access (EDCA)
            • extension to DCF
            • provide for the “prioritization of frames” based on upper-layer protocols
  • Hybrid Coordination Function Controlled Channel Access (HCCA)
    • extension of PCF
    • Gives the access point the ability to provide for “prioritization of stations.”
    • Like PCF never adopted by WLAN vendors
  • Wi-Fi Alliance also has a certification known as Wi-Fi Multimedia (WMM).

IEEE 802.11-2012 ratified amendments

  • 802.11r-2008
    •  Fast basic service set transition (FT)
    •  Fast secure roaming because it defines faster handoffs when roaming occurs between cells in a WLAN using the strong security defined by a robust secure network (RSN)
    • Multiple types of fast secure roaming are implemented by different vendors: CCKM, PKC, OKC, and fast session resumption
  • 802.11k-2008
    • radio resource measurement (RRM)
    • The following are some of the key radio resource measurements defined under 802.11k
      • Transmit Power Control (TPC)
        • 802.11h defined this for 5GHz frequency, 802.11k brings it in for other bands
      • Client Statistics
        • Physical layer information – signal-to-noise, signal strength, data rates can be reported back to the access point
      • Channel Statistics
        • Noise floor information and Channel load information can be reported back to the access point
      • Neighbour Reports
        • Ability to learn details about other access points that the client might want to roam to from the access point or the WLAN Controller
  • 802.11y-2008
    • allow high-powered, shared 802.11 operations with other non-802.11 devices in the 3650 MHz–3700 MHz licensed band in the United States
    • requires content-based protocol (CBP) mechanisms to avoid interference between devices
    • defines dynamic STA enablement (DSE) procedures
  • 802.11w-2009
    • Robust management frames
    • Designed to prevent DOS attacks against management frames
    • When unicast management frames are protected, frame protection is achieved by using CCMP
    • Broadcast and multicast frames are protected using the Broadcast/Multicast Integrity Protocol (BIP)
  • 802.11n-2009
    • Increase the throughput in both the 2.4 GHz and 5 GHz frequency bands
    • New operation known as High Throughput (HT)
    • Provides PHY and MAC enhancements to support data rates of up to 600 Mbps
    • Multiple-input, multiple-output (MIMO) technology in unison with OFDM technology
    • 802.11n radios are also backward compatible with legacy 802.11a/b/g radios
    • 40 MHz channel width available
  • 802.11p-2010
    • Support Intelligent Transportation Systems (ITS) applications
    • Data exchanges between high-speed vehicles is possible in the licensed ITS band of 5.9 GHz
    • Known as Wireless Access in Vehicular Environments (WAVE)
    • 802.11p will also be applicable to marine and rail communications
  • 802.11z-2010
    • Direct Link Setup (DLS) mechanism
    • DLS allows client stations to bypass the access point and communicate with direct frame exchanges
    • DLS communications have yet to be used by enterprise WLAN vendors
  • 802.11u-2011
    • Wireless Interworking with External Networks (WIEN)
    • Is the basis for the Wi-Fi Alliance’s Hotspot 2.0 specification and its Passpoint certification
    • This standard and certification is designed to provide seamless roaming for wireless devices between your Wi-Fi network and other partner networks, similar to how cellular telephone networks provide roaming
  • 802.11v-2011
    • Provides for an exchange of information that can potentially ease the configuration of client stations wirelessly from a central point of management
    • Defines Wireless Network Management (WNM)
  • 802.11s-2011
    • Standardizing mesh networking using the IEEE 802.11 MAC/PHY layers
    • defines the use of mesh points, which are 802.11 QoS stations that support mesh services
    • Mesh access point (MAP) is a device that provides both mesh functionalities and AP functionalities simultaneously
    • Mesh point portal (MPP) is a device that acts as a gateway to one or more external networks such as an 802.3 wired backbone

Post-2012 ratified amendments

  • 802.11ae-2012
    • Enhancements to QoS management
    • Quality-of-service management frame (QMF) service can be enabled
  • 802.11aa-2012
    • QoS enhancements to the 802.11 Media Access Control (MAC) for robust audio and video streaming for both consumer and enterprise applications
  • 802.11ad-2012
    • defines Very High Throughput (VHT) enhancements using the much higher unlicensed frequency band of 60 GHz
    • higher frequency range is big enough to support data rates of up to 7 Gbps, downside  is its limited to line of sight
    • Galois/Counter Mode Protocol (GCMP), which also uses AES cryptography
  • 802.11ac-2013
    • Defines Very High Throughput (VHT) enhancements below 6 GHz
    • 5GHz frequency only
    • 802.11ac promises Gigabit speeds using four major enhancements:
      • Wider Channels
        • Ability to use 80 and 160 MHz channels
      • New Modulation
        • 256-QAM modulation – potential to improve increase speed by 30%, although requires very high SNR
      • More Spatial Streams
        • Up to 8 spatial streams, although first gen 802.11ac will use 1 -4 spatial streams
      • Improved MIMO and Beamforming
        • multi-user MIMO (MU-MIMO) technology
        • utilize a simplified beamforming method called null data packet (NDP) beamforming
  • 802.11af-2014
    • use of wireless in the newly opened TV white space (TVWS) frequencies between 54 MHz and 790 MHz

IEEE 802.11 draft amendments

  • 802.11ah
    • Wi-Fi in frequencies below 1 GHz
    • lower frequencies will mean lower data rates but longer distances
    • Likely use is IoT sensors and a Wi-Fi back hall
  • 802.11ai
    • fast initial link setup (FILS)
    • STA to establish a secure link setup in less than 100 ms
  • 802.11aj
    • modifications to the IEEE 802.11ad-2012 amendment’s PHY and MAC layer to provide support for operating in the Chinese Milli-Meter Wave (CMMW) frequency bands
    • Chinese 45 GHz frequency band
  • 802.11ak
    • referred to as General Link (GLK).
    • enhancement to 802.11 links for use in bridged networks
  • 802.11aq
    • enables delivery of network service information prior to the association of stations on an 802.11 network

Defunct amendments

  • Amendments considered dead in the water:
    • 802.11F
      • standard mandated that vendor access points support roaming
      • 802.11F was intended to address roaming interoperability between autonomous access points from different vendors
    • 802.11T
    • called Wireless Performance Prediction (WPP)

802.11m Task group

  • This task group also is responsible for “rolling up” ratified amendments into a published document
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s