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transmission rate of 11 Mbps and IEEE 802.11a provided a transmission rate of 54 Mbps. In the 2000s, the IEEE 802.11 g was developed; it provides a transmission rate of 54 Mbps by applying OFDM at 2.4 GHz. To overcome the limits of WLAN communication speed, recent WLAN standards have introduced new schemes for increasing the speed and reliability of a network and extending a management distance of a wireless network. For example, IEEE 802.11n has introduced the standard of MIMO, using multiple antennas for both transmitter and receiver to support high throughput (HT), as depicted graphically in Figure 2.1. IEEE 802.11n provides a transmission rate of 300 Mbps with four spatial streams by applying MIMO‐OFDM; the standard also supports a channel bandwidth of up to 40 MHz and thus, provides a theoretical transmission rate of 600 Mbps with four spatial streams. These earlier standards have evolved into IEEE 802.11ac that can utilize a bandwidth of up to 160 MHz and supports a transmission rate of up to about 1 Gbps; it can make use of up to 8 spatial streams. The IEEE 802.11ax standard was under finalization at press time; the standard defines a high‐efficiency WLAN for enhancing the system throughput in high‐density environments; 802.11ax contemplates dynamically adjusting the energy level when a channel is clear, depending on whether the energy corresponds to its BSS signals or signals from another BSS [5, 6]. Such a scheme helps to promote spatial reuse between neighboring networks.

More broadly, a series of standards have been adopted as the WLAN evolved, including IEEE Std 802.11‐2012 (March 2012). This standard was subsequently amended by IEEE Std 802.11ae‐2012, IEEE Std 802.11aa‐2012, IEEE Std 802.11ad‐2012, IEEE Std 802.11ac‐2013, IEEE Std 802.11af‐2013, IEEE Std 802.11aj‐2018, IEEE Std 802.11ak‐2018, and IEEE Std 802.11aq‐2018 [2, 7, 8, 9]. Table 2.2 provides a list of IEEE 802.11 active projects at press time [10].

2.3 WLAN BASIC CONCEPTS

      The transmission processes operate at the PHY layer and the Data Link layer. A WLAN device typically includes a baseband processor, a RF transceiver, an antenna unit, a storage device (e.g. memory), an input interface unit, and an output interface unit. The baseband processor performs baseband signal processing and includes a MAC processor and a PHY processor.

       The MAC processor includes a MAC software processing unit and a MAC hardware processing unit. The PHY processor includes a transmitting signal processing unit and a receiving signal processing unit. The PHY processor implements a plurality of functions of the PHY layer. These functions may be performed in software, hardware, or a combination thereof according to implementation.

       The PHY processor may be configured to generate Channel State Information (CSI), according to information received from the RF transceiver. The CSI may include one or more of an RSSI; a Signal to Interference and Noise Ratio (SINR); a Modulation and Coding Scheme (MCS); and the Number of Spatial Streams (NSS). CSI may be generated for one or more frequency blocks, a sub‐band within the frequency block, a subcarrier within a frequency block, a receiving antenna, a transmitting antenna, and combinations of a plurality thereof.

TABLE 2.2 IEEE 802.11 Active Projects at Press Time

802.11 Amendment	Description
P802.11ay – IEEE Draft Standard for Information Technology – Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks – Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications – Amendment: Enhanced Throughput for Operation in License‐Exempt Bands Above 45 GHz	This amendment defines standardized modifications to both the IEEE 802.11 Physical Layers (PHY) and the IEEE 802.11 Medium Access Control layer (MAC) that enables at least one mode of operation capable of supporting a maximum throughput of at least 20 gigabits per second (measured at the MAC data service access point), while maintaining or improving the power efficiency per station.
P802.11ba – IEEE Draft Standard for Information Technology – Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks – Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment: Wake‐up radio operation	This amendment defines modifications to both the IEEE 802.11 Physical Layer (PHY) and the Medium Access Control (MAC) sublayer for wake‐up radio operation.
P802.11 – IEEE Draft Standard for Information Technology – Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks – Specific Requirements – Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications	Technical corrections and clarifications to IEEE Std 802.11 for Wireless Local Area Networks (WLANs), as well as enhancements to the existing Medium Access Control (MAC) and Physical Layer (PHY) functions, are specified in this revision.
P802.11ax – IEEE Draft Standard for Information Technology – Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks – Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment Enhancements for High‐Efficiency WLAN	This amendment defines modifications to both the IEEE 802.11 Physical Layer (PHY) and the Medium Access Control (MAC) sublayer for high‐efficiency operation in frequency bands between 1 and 7.125 GHz.
P802.11az – IEEE Draft Standard for Information Technology – Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks – Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications – Enhancements for Positioning	This amendment defines modifications to both the IEEE 802.11 Physical Layer (PHY) and Medium Access Control (MAC) sublayer that enable determination of absolute and relative position with better accuracy with respect to the Fine Timing Measurement (FTM) protocol executing on the same PHY‐type, while reducing existing wireless medium use and power consumption and is scalable to dense deployments. This amendment requires backward compatibility and coexistence with legacy devices. Backward compatibility with legacy 802.11 devices implies that devices implementing this amendment shall (a) maintain data communication compatibility and (b) support the FTM protocol.
P802.11bb – Standard for Information Technology – Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks – Specific Requirements – Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment: Light Communications	The scope of this standard is to define one Medium Access Control (MAC) and several Physical Layer (PHY) specifications for wireless connectivity for fixed, portable, and moving stations (STAs) within a local area.
P802.11bc – Standard for Information technology – Telecommunications and information exchange between systems Local and metropolitan area networks – Specific requirements – Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment: Enhanced Broadcast Service	The scope of this standard is to define one Medium Access Control (MAC) and several Physical Layer (PHY) specifications for wireless connectivity for fixed, portable, and moving stations (STAs) within a local area.
P802.11bd – Standard for Information technology – Telecommunications and information exchange between systems Local and metropolitan area networks – Specific requirements – Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment: Enhancements for Next‐Generation V2X	The scope of this standard is to define one Medium Access Control (MAC) and several Physical Layer (PHY) specifications Скачать книгу В начало < 17 18 19 20 21 22 23 24 25 26 > В конец