Wireless Network Technology-802.11n

The development of wireless network technology has always been a topic of our attention. Do we really know about 802.11n technology? Here we will give a detailed description of the IEEE 802.11n technology through technical improvements on the physical layer and the MAC layer to greatly improve the wireless transmission rate, so that the bandwidth is increased from 54Mbps to 300 Mbps.

The core of 802.11n-MIMO-OFDM

The OFDM modulation technology is to convert high-speed data streams into multiple low-rate sub-data streams, and then communicate with multiple sub-carrier physical channels to reduce ISI (Inter-code interference) opportunity.

MIMO (multi-input and multi-output) technology is used at both the sending end and the receiving end of the link to convert multi-path transmission into a favorable factor, so that without increasing the channel bandwidth, increase the capacity and spectrum utilization of the communication system exponentially to increase the speed of the WLAN system.

Combining MIMO and OFDM technology produces mimo ofdm technology. It uses array antennas in the OFDM transmission system to achieve spatial diversity and improve signal quality, additionally, the multi-path capacity is increased to improve the effective transmission rate of wireless networks.

Dual-band (20-MHz and 40-MHz bandwidth)

IEEE 802.11n binds two adjacent 20 MHz bandwidths to form a 40 MHz communication bandwidth. In actual work, it can be used as two 20 MHz bandwidths (one as the primary bandwidth and the other as the secondary bandwidth, when sending and receiving data, the bandwidth can work at 40 MHz or at a single 20 MHz), which can double the speed. At the same time, for IEEE 802.11a/B/g, in order to prevent interference from adjacent channels, a small part of the bandwidth boundary is reserved on both sides of the 20 MHz channel. Through band binding technology, these reserved bandwidths can also be used for communication, further improving throughput.

Figure 20/40-MHz bandwidth Throughput

Short Guard Interval

Short GI (Guard Interval) is an improvement made by 802.11n for 802.11a/g. When the RF chip uses OFDM modulation to send data, the entire frame is divided into different data blocks for transmission. For the reliability of data transmission, there will be GI between data blocks, it is used to ensure that the receiving side can correctly parse each data block. Wireless signal transmission in space may cause latency on the receiving side due to factors such as multi-path. If subsequent data blocks are sent too fast, it will interfere with the previous data block, GI is used to avoid this interference. The GI length of 11a/g is 10% us, while that of Short GI is us. In addition, Short GI is independent of bandwidth and supports 20 MHz and 40 MHz bandwidth.