Wi-Fi is a wireless network communication technology based on IEEE 802.11 standards. The following describes the milestone 802.11 standards. Show IEEE 802.11 IEEE 802.11 is a series of standards formulated for Wi-Fi. The first version was released in 1997, which defined the access control layer and physical layer for media access. At the physical layer, the standards defined 2 radio frequency modulation modes and 1 infrared transmission mode over the 2.4 GHz Industrial, Scientific, and Medical (ISM) frequency band. The designed total data transmission rate was 2 Mbit/s. IEEE 802.11a and IEEE 802.11b In 1999, these 2 versions were added. 802.11a defined a physical layer with a data transmission rate up to 54 Mbit/s over the 5 GHz ISM frequency band. 802.11b defined a physical layer with a data transmission rate up to 11 Mbit/s over the 2.4 GHz ISM frequency band. IEEE 802.11g 802.11g was passed in July 2003. Its carrier frequency is 2.4 GHz (same as that of 802.11b), and the transmission rate reaches 54 Mbit/s. 802.11g hardware is backward compatible with 802.11b hardware. Some wireless router vendors develop new standards based on 802.11g standard to meet market requirements and increase the theoretical transmission rate to 108 Mbit/s or 125 Mbit/s. IEEE 802.11n IEEE 802.11n was a new 802.11 standard developed by a new unit of the IEEE in January 2004. It was formally approved in September 2009. Its theoretically maximum transmission rate is 600 Mbit/s, and the transmission distance is longer. IEEE 802.11ac The rapid development of mobile services and high-density access poses higher requirements on the bandwidth of Wi-Fi networks. The 802.11ac standard released in 2013 introduces wider radio bandwidth (160 MHz) and higher-order modulation technology (256-QAM), with a transmission rate up to 1.73 Gbit/s, further increasing the Wi-Fi network throughput. In 2015, the 802.11ac Wave 2 standard was released, making beamforming and MU-MIMO mainstream functions and improving the system access capacity. Unfortunately, 802.11ac supports only terminals working on the 5 GHz frequency band, and compromises user experience on the 2.4 GHz frequency band. IEEE 802.11ax The next-generation Wi-Fi needs to solve the problem that the efficiency of a Wi-Fi network decreases when many terminals access the Wi-Fi network. In 2019, the Wi-Fi 6 (802.11ax) standard was officially released to introduce technologies such as uplink MU-MIMO, OFDMA, and 1024-QAM high-order coding. Wi-Fi 6 improves network capacity and transmission efficiency by fully utilizing spectrum resources and enabling multiple terminals to access the network. Compared with Wi-Fi 5, Wi-Fi 6 aims to increase the average throughput of users by at least four times and the number of concurrent users by more than three times in a dense user environment. Therefore, Wi-Fi 6 is also known as high-efficiency WLAN (HEW). 802.11 is a set of wireless standards that regulate the transmission modes within the network. They are commonly used in 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac to provide wireless connectivity to your home office and commercial facilities. IEEE 802.11g has been developed in 2003 as an extension to 802.11b. It increases bandwidth to 54 Mbit/s using the same 2.4 GHz band as 802.11b. It uses CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance - a protocol defining the method of multiple access to the link with carrier status monitoring and collision avoidance). Available bandwidth is distributed between the transmitting stations, including AP (Access Point) for traffic to and from the device. 802.11g devices are backwards compatible with 802.11b devices. The presence of a device operating at 802.11b significantly reduces the capacity of the entire network operating at 802.11g. 802.11g standard uses OFDM (Orthogonal Frequency-Division Multiplexing) modulation originating in 802.11a with bit rates of 6, 9, 12, 18, 24, 36, 48 and 54 Mb/s and returns CCK (Complementary Code Keying - as in 802.11b standard) for 5.5 and 11 Mb/s and DBPSK/DQPSK + DSSS modulation for 1 and 2 Mb/s. Although 802.11g operates at the same frequency band as 802.11b, it may reach higher bit rates due to its origins in 802.11a. Out of 52 OFDM sub-carriers, 48 are reserved for data, 4 are pilot sub-carriers with 0.3125 MHz (20 MHz/64) carrier spacing. Symbol duration is 4 microseconds and includes a 0.6 microsecond interval. The actual orthogonal components are generated and decoded in the baseband using DSP. The components are converted in the transmitter to 2.4 GHz frequencies. The benefits of using OFDM include reduced multi-path signal propagation phenomena and improved spectral efficiency. Despite good reception and quick implementation, 802.11g is characterized by interference levels similar to 802.11b in the overcrowded 2.4 GHz band. The devices operating in this band include microwaves, Bluetooth devices or digital wireless phones, often introducing major interferences. Also, the number of users and their density in urban areas can be a major issue. To prevent interferences, three non-overlapping channels are available in the US and countries with similar regulations (channel 1, 6, 11 with 25 MHz separation) and four in Europe (channel 1, 5, 9, 13 with 20 MHz separation). However, the interferences may still occur, due to the side lobes of the transmitter radiation characteristics, however those are much weaker. Table 1. List of frequencies and corresponding channels
Not all channels are legal in all countries Fig. 1. Graphic representation of 14 channels and corresponding mid-band frequencies  Which of the following is a channel bandwidth used in 802.11 g networks?Often referred to as the 2.4 GHz band, this spectrum is the most widely used of the bands available for Wi-Fi. Used by 802.11b, g, & n.
What is the bandwidth of 802.11 g?Different Wi-Fi Protocols and Data Rates. What is the channel bandwidth specified in the IEEE 802.11 a standard?Networks using 802.11a operate at radio frequency of 5GHz or 3.7GHz and a bandwidth of 20MHz. The specification uses a modulation scheme known as orthogonal frequency-division multiplexing (OFDM) that is especially well suited to use in office settings.
What is the 802.11 g standard?The 802.11g is a standard for Wireless Local Area Networks (WLANs) and an extension to the 802.11 specification. 802.11g was developed by the Institute of Electrical and Electronics Engineers (IEEE) for WLAN as an improvement over its predecessor, 802.11b.
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Which of the following channel bandwidth is specified in the IEEE 802.11 g standard?
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