With the increase of mobile terminals, the demand for wireless networks is also increasing. Can 802.11n as the current mainstream protocol meet our latest needs? Let us first analyze the technology of 802.11n!
With its inherent characteristics, wireless technology continues to develop and add value. From the initial 802.11 to 802.11 a / b, to 802.11 g and the current 802.11n standard. It took more than seven years from the beginning to the final approval to officially release the protocol standard with multiple enhanced functions.
802.11n technology
For the past seven years, the IEEE Standardization Organization has been working on a new set of standards. While the new standard provides new functions, it also standardizes the improvement of 802.11 radio frequency functions. The new standard significantly improves the reliability of 802.11 communications, the predictability of wireless signal coverage, and enhances the overall throughput of 802.11 devices. At the same time, it is backward compatible with the traditional 802.11 environment.
The original 802.11n standard is largely based on the draft of the 802.11n Wi-Fi Alliance version 2.0, and includes the following key equipment requirements. These key equipment requirements are now included in the final version:
MIMO—Describes the use of multiple-input multiple-output (MIMO) technology;
RF enhancement-increased channel capacity, higher modulation rate and lower system overhead;
MAC enhancements—based on the existing 802.11 device data frames, the frame format that can be used for 802.11n has been modified;
MIMO
Multi-input multi-output (MIMO) technology is the core of the 802.11n standard. This discussion of MIMO technology provides a basis for understanding how 802.11n achieves 600 Mbps.
The essence of wireless communication is that it is easily affected by various kinds of interference, distortion or noise. Similar to wireline technology, the benefits of signal-to-noise ratio (SNR) are critical to the ability to efficiently transmit data. The larger the value of the signal-to-noise ratio, the more information the signal can carry, and the more information it can recover at the receiving end.
802.11n uses two interesting techniques to improve the signal-to-noise ratio and the environment with multipath effects: beamforming and multipath spatial diversity. The following sections describe their functions and benefits.
Transmission beamforming technology
Beamforming is a technique used when there are multiple transmit antennas and a single receive antenna in an open or less obstructed environment. When there are multiple transmitting antennas, each transmitted RF signal will have a different phase due to the different transmission paths during transmission. These differences will affect the overall signal-to-noise ratio. By adjusting the phase of the transmitted signal so that they can be well matched at the receiving end, the signal-to-noise ratio will be greatly improved. Therefore, the transmitter can carry more information and the receiver can restore more information.
So far, we have noticed that this particular method closely depends on the feedback mechanism between the transmitter and the receiver. The information on the wireless signal received by the receiving end will be returned to the transmitting end, so that the transmitting end adjusts its radio frequency signal.
When implementing beamforming technology, the following points need to be noted:
1. This special technology is only valid for the 802.11n transmitter and receiver;
2. Only apply when only sending a signal to a single receiver;
3. The feedback mechanism between the receiver and the transmitter is not direct and instantaneous. If the transmitter or receiver position changes, you need to rebuild the relationship;
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