With up to 600 Mbps, the emerging 802.11n standard is the next generation of wireless networking technology that delivers the speed, range and reliability needed to support the most bandwidth-sensitive applications. 802.11n combines multiple technologies, including SpaTIal MulTIplexing MIMO (MulTI-In, MulTI-Out) (Spatial Multiplex Multiple Input), 20 and 40MHz channels, and dual bands (2.4 GHz and 5 GHz) for Forms a high rate while communicating with previous IEEE 802.11b/g devices.
Multiple Input Multiple Output (MIMO) or Multiple Receive Multiple Antenna (MTMRA) technology is a major breakthrough in smart antenna technology in the field of wireless mobile communications. This technology can double the capacity and spectrum utilization of communication systems without increasing bandwidth, and is a key technology that must be adopted in a new generation of mobile communication systems.
Introduction to 802.11n technology MIMO and OFDM802.11n focuses on high-throughput research and plans to increase the transmission rate of WLANs from 54 Mbps for 802.11a and 802.11g to more than 108 Mbps, with a maximum rate of 320 Mbps or even 500 Mbps. Such a high rate of course has technical support, and OFDM technology, MIMO (multiple input and multiple output) technology is the key.
OFDM technology is a type of Multi-Carrier Modulation (MCM) that was once adopted in the 802.11g standard. The core is to divide the channel into a number of narrowband modulation and transmit orthogonal subchannels, and make the signal bandwidth on each subchannel smaller than the relevant bandwidth of the channel, to reduce the mutual interference between the carriers, and improve the spectrum. Utilization technology.
OFDM also enables uplink and downlink asymmetric transmissions by using different numbers of subchannels. However, OFDM technology is susceptible to frequency deviation and has a high peak-to-average power ratio (PAR). However, space-time coding, diversity, interference suppression, and smart antenna technology can be used to maximize the reliability of the physical layer. 802.11g Although similar techniques are used, the combination with MIMO technology in 802.11n is naturally inferior.
802.11n technology camp cooperation developmentThere are two major technology camps on the 802.11n standard, the WWiSE (World Wide Spectrum Efficiency) Alliance and the TGn Sync Alliance. Currently, the 802.11n working group has moved forward and adopted a combined solution that is integrated by the Extended Wireless Alliance (EWC). The Extended Wireless Alliance (EWC) is an industry organization led by Broadcom, Intel and other Wi-Fi providers. The 802.11n 1.0 draft is a powerful combination of two approaches that have been adopted by the IEEE and are now being carefully examined by the working group for final adoption.
Among them, WWiSE has received support from Texas Instruments, Broadcom, Conexant, STMicro, Airgo and Bermai, and Motorola, which has previously submitted its own standards, has joined the camp; TGn Sync's supporters include Intel, Atheros, Agere, and Infineon. Ling, Cisco, Qualcomm, Nortel Networks, Mitsubishi, Sony, Panasonic, Philips, Samsung, Sanyo and Toshiba. WWiSE is based on the current 20 MHz channel format adopted worldwide, and is used by more than tens of millions of Wi-Fi devices around the world. This approach not only ensures support for existing Wi-Fi products, but also improves Wi-Fi. -Fi network performance within the specified frequency band. In addition, alliance vendors represent an important intersection in the semiconductor supply and consumer sectors that make up the Wi-Fi market, which will create strong partnerships between developers and end product manufacturers.
On a technical level, the WWiSE proposal marks a significant advancement in 802.11 implementation capabilities, with key features including:
Enforce the use of an approved, existing and globally applicable 20MHz Wi-Fi channel width to ensure it is immediately available and deployed under any telecommunications regulations.
Stronger MIMO-OFDM technology, which is the key to achieving a maximum data rate of 135 Mbps in a 2×2 configuration and a minimum requirement of 20 MHz channels, thereby reducing implementation costs. This technology can also greatly improve simple antenna extension or channel integration techniques.
With a 4×4 MIMO architecture and 40 MHz channel width (as long as the supervisor is allowed), the 540 Mbps maximum data rate provides a sustainable blueprint for future devices and applications.
Mandatory mode provides backward compatibility and interoperability with existing Wi-Fi devices in the 5 GHz and 2.4 GHz bands, ensuring that installed devices are still supported.
Advanced FEC encoding helps maximize coverage and online distance, and it is suitable for all MIMO configurations and channel bandwidths.
The TGn Sync Alliance uses two MIMO antennas in conjunction with a 40MHz channel to create a device that provides 250Mbps bandwidth and a usable throughput of 175Mbps. WWiSE members have suggested that this will reduce the number of available non-overlapping 802.11 channels, which is illegal in some countries, such as Japan. Instead, the organization's proposed technology uses four MIMO antennas while maintaining the current 20MHz channel defined by 802.11. This approach is said to be more spectrally efficient and subject to fewer regulatory barriers.
802.11n's technical advantages802.11n focuses on high-throughput research and plans to increase the transmission rate of WLAN from 54Mbps at 802.11a and 802.11g to above 108Mbps, with a maximum rate of 320Mbps or even 500Mbps. Such a high rate of course has technical support, and OFDM technology, MIMO (multiple input and multiple output) technology is the key.
OFDM technology is a type of MCM (Multi-Carrier Modulation) that was once adopted in the 802.11g standard. The core is to divide the channel into a number of narrowband modulation and transmission orthogonal subchannels, and make the signal bandwidth on each subchannel smaller than the relevant bandwidth of the channel, to reduce the mutual interference between the carriers, and improve the spectrum utilization. technology. OFDM also enables uplink and downlink asymmetric transmissions by using different numbers of subchannels. However, OFDM technology is susceptible to frequency deviation and has a high peak-to-average power ratio (PAR). However, space-time coding, diversity, interference suppression, and smart antenna technology can be used to maximize the reliability of the physical layer. 802.11g Although similar techniques are used, the combination with MIMO technology in 802.11n is naturally inferior.
MIMO (Multiple Input Multiple Output) technology is a major breakthrough in smart antenna technology in the field of wireless communications, which can double the capacity and spectrum utilization of communication systems without increasing bandwidth. A MIMO system employs multiple antennas (or array antennas) and multiple channels at both the transmitting end and the receiving end. The transport stream S(k) is space-time coded to form N information substreams Ci(k), i=1, . . . , N. The N substreams are transmitted by the N antennas and received by the M receiving antennas after the spatial channel. Multi-antenna receivers can separate and decode these data substreams using advanced space-time coding processing, so that MIMO systems can create multiple parallel spatial channels and solve the problem of bandwidth sharing. The number of 802.11n antennas can be up to 3*3, which is three times greater than the 802.11g3.
Combining MIMO with OFDM technology, MIMO OFDM technology is generated, which achieves spatial diversity by using array antennas in OFDM transmission systems, improves signal quality, and increases multipath tolerance, enabling efficient transmission rates of wireless networks. There is a qualitative improvement.
In order to improve the throughput of the entire network, 802.11n also optimizes the single MAC layer protocol of the 802.11 standard, changes the data frame structure, increases the proportion of the net load, and reduces the number of bytes occupied by the management error detection. Increased network throughput. On the antenna, the application of smart antenna technology also solves the transmission coverage problem of 802.11n. The antenna array system consisting of multiple sets of independent antennas dynamically adjusts the direction of the beam. 802.11n ensures that users receive stable signals and reduce interference from other noise signals, so that the transmission distance of the wireless network can be increased to several kilometers. Sexually enhanced.
In terms of compatibility, 802.11n uses software radio technology to solve different standards using different working frequency bands and different modulation modes, resulting in difficulties in interoperability between systems and poor mobility. Software radio is a fully programmable hardware platform. All applications are implemented by software programming on the platform. In other words, base stations and mobile terminals of different systems can be implemented by different software based on the same hardware. . Software radio technology will fundamentally change the network structure, realize the fusion of wireless LAN and wireless WAN and can accommodate various standards and protocols, and provide a more open interface, which will greatly increase the flexibility of the network. In addition, the 802.11n working mode includes two working frequency bands of 2.4 GHz and 5.8 GHz, which ensures compatibility with the previous 802.11a/b/g standard and greatly protects the user's investment.
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