802.11ac technology essence question and answer collection
For "post 11n technology"-802.11ac, everyone may be relatively unfamiliar. As a preliminary exploration of this new technology, this article will lead you through the question and answer form to get a preliminary understanding of the technology. Starting from the 802.11b protocol in 1999, WiFi has experienced two “speed-upsâ€: the first was from 11Mbps in 802.11b to 54Mbps in 802.11g in 2003, and the second was from 54Mbps to 802.11n. 300Mbps of the protocol. The current mainstream WiFi standard, 802.11n, already supports 3 streams at up to 450Mbps physical layer rate. In the future, 450 Mbps 11n will become the mainstream of WiFi, and will inevitably become an unstoppable trend. In theory, 802.11n can support up to 4 streams and 600Mbps, but from the perspective of the development of the industry chain, mainstream WiFi chip manufacturers have not continued the development and production of 4 streams of 11n, and instead put their energy into a kind of The technology called "post 11n technology" is what will be introduced in this issue-IEEE 802.11ac. 1. Has the 802.11ac standard been determined? A: The official standard has not been determined yet, and it is currently in Draft 2.0 draft stage. It is expected that standardization will be achieved in 2013. 2. Which frequency does 802.11ac use? Answer: 802.11ac uses the 5GHz frequency and does not support 2.4GHz. It can be considered that 802.11ac is an evolved version of 802.11n at 5 GHz. 3. What is the maximum speed of 802.11ac? Answer: Up to 6.9Gbps ​​at 8 streams, 256QAM (Quadrature Amplitude ModulaTIon, phase quadrature amplitude modulation), 160MHz. The chip design of 8-stream MIMO obviously needs to be very complicated, and the bandwidth resources of 160MHz are also out of reach in China. What can be expected at present is: up to 1.3Gbps under 3 streams, 256QAM, 80MHz. Even so, the 1.3Gpbs speed can be increased by 200% compared to the current fastest 450Mbps! 4. How much bandwidth does 802.11ac require? Answer: Mandatory support for 40MHz, 80MHz bandwidth, optional support for 160MHz and 80MHz + 80MHz bandwidth. as the picture shows. Figure 802.11ac bandwidth and 5GHz spectrum resources 5. What new technologies does 802.11ac use? Answer: The physical layer includes 256QAM encoding, up to 8 streams, and MU-MIMO. The MAC layer includes enhanced MPDU / MSDU aggregation technology (that is, packets can be aggregated larger than 11n), and others include VHT link adaptation (negotiation of link capabilities). MU-MIMO is actually multi-user (mulTI-user) MIMO. The MIMO supported by 802.11n technology can only be single-user MIMO, that is, no matter whether it is 3 streams or 2 streams, only 3 streams or 2 streams can be used for communication between the AP and all STAs. If MU-MIMO is supported, it means that one 3-stream AP can communicate with 3 STAs in one stream at the same time, and there will be no interference with each other. This will greatly improve the throughput performance when multiple users access the AP at the same time, and it is also an important reason for 802.11ac to look forward to. 6. How mature is the 802.11ac terminal? Answer: At present, there are still few terminals, and it is expected to be popularized after standardization in 2013. 7. Is China's 5.8GHz bandwidth resource sufficient for 802.11ac? Answer: At present, China ’s 5.8GHz open frequency is only available from 5.725-5.850GHz, and the total bandwidth is only about 100MHz. It certainly cannot provide the highest 160MHz bandwidth of 802.11ac. Even if it is 80MHz, it can only accommodate one The bandwidth of APs will become a big obstacle for the batch deployment of APs. As we all know, the 5GHz open frequency band in the United States is far more than that in China. In the development stage of 802.11ac, more resources mean more rapid development of the industrial chain. At present, there is a high demand to open the 5GHz frequency in China. Operators and various manufacturers are eager to see the new 5GHz open frequency band. Whether we can finally release it in the next few years remains to be seen. Portable Electric Burner,Electric Cookers,Counter Top Cooking Tools,Electric Iron Burner Shaoxing Haoda Electrical Appliance Co.,Ltd , https://www.hotplates.nl