3/7/2021 0 Comments Wifi 802.11N Driver
The total bandwidth is 20 MHz with an occupied bandwidth of 17.8 MHz. Total symbol duration is 3.6 or 4 microseconds, which includes a guard interval of 0.4 (also known as short guard interval (SGI)) or 0.8 microseconds.The Wi-Fi Alliance has also retroactively labelled the technology for the standard as Wi-Fi 4.It standardized support for multiple-input multiple-output, frame aggregation, and security improvements, among other features, and can be used in the 2.4 GHz or 5 GHz frequency bands.
They are commonly used today in their 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac and 802.11ax versions to provide wireless connectivity in homes and businesses. Development of 802.11n began in 2002, seven years before publication. The 802.11n protocol is now Clause 20 of the published IEEE 802.11-2012 standard. One way it provides this is through Spatial Division Multiplexing (SDM), which spatially multiplexes multiple independent data streams, transferred simultaneously within one spectral channel of bandwidth. MIMO SDM can significantly increase data throughput as the number of resolved spatial data streams is increased. Each spatial stream requires a discrete antenna at both the transmitter and the receiver. In addition, MIMO technology requires a separate radio-frequency chain and analog-to-digital converter for each MIMO antenna, making it more expensive to implement than non-MIMO systems. It can be enabled in the 5 GHz mode, or within the 2.4 GHz mode if there is knowledge that it will not interfere with any other 802.11 or non-802.11 (such as Bluetooth) system using the same frequencies. The MIMO architecture, together with wider-bandwidth channels, offers increased physical transfer rate over 802.11a (5 GHz) and 802.11g (2.4 GHz). Precoding includes spatial beamforming and spatial coding, where spatial beamforming improves the received signal quality at the decoding stage. ![]() However, the individual radios often further limit the number of spatial streams that may carry unique data. The a x b: c notation helps identify what a given radio is capable of. The first number (a) is the maximum number of transmit antennas or TX RF chains that can be used by the radio. The second number (b) is the maximum number of receive antennas or RX RF chains that can be used by the radio. The third number (c) is the maximum number of data spatial streams the radio can use. ![]() Common configurations of 11n devices are 2x2:2, 2x3:2, and 3x2:2. All three configurations have the same maximum throughputs and features, and differ only in the amount of diversity the antenna systems provide. In addition, a fourth configuration, 3x3:3 is becoming common, which has a higher throughput, due to the additional data stream. If more antennas are used, then 802.11n can go up to 288 megabits per second in 20 MHz mode with four antennas, or 600 megabits per second in 40 MHz mode with four antennas and 400 ns guard interval. Wifi 802.11N Free Radio SpectrumBecause the 2.4 GHz band is seriously congested in most urban areas, 802.11n networks usually have more success in increasing data rate by utilizing more antennas in 20 MHz mode rather than by operating in the 40 MHz mode, as the 40 MHz mode requires a relatively free radio spectrum which is only available in rural areas away from cities. Thus, network engineers installing an 802.11n network should strive to select routers and wireless clients with the most antennas possible (one, two, three or four as specified by the 802.11n standard) and try to make sure that the networks bandwidth will be satisfactory even on the 20 MHz mode. Various modulation schemes and coding rates are defined by the standard and are represented by a Modulation and Coding Scheme (MCS) index value. The table below shows the relationships between the variables that allow for the maximum data rate. The total bandwidth is 20 MHz with an occupied bandwidth of 17.8 MHz. Total symbol duration is 3.6 or 4 microseconds, which includes a guard interval of 0.4 (also known as short guard interval (SGI)) or 0.8 microseconds.
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