What Are Smart Antennas?
A smart antenna is an adaptive antenna array consisting of multiple antennas. It uses intelligent algorithms to calculate the optimal antenna combination so that the signals transmitted by the antennas are superimposed and enhanced at the receive end. Doing so increases the signal coverage distance and improves the transmission rate. Smart antennas make optimal use of beamforming and antenna array technologies, thereby reaping better benefits.
Why Do We Need Smart Antennas?
Problems Facing Common Antennas
Wi-Fi standards have constantly evolved over time and now come to the sixth generation — Wi-Fi 6 (also know as 802.11ax). Wi-Fi 6 offers a theoretical speed of about 10 Gbit/s but hardly provides users with such an ultra-high speed in actual use. This is because in wireless communications, the Wi-Fi speed experienced by users is affected by Wi-Fi standards as well as various environmental factors such as interference and obstacles.
To improve the user-experienced Wi-Fi speed, we need to expand AP coverage ranges to improve signal quality while reducing interference between signals. Antennas — the core component of a wireless communications system — determine the beams of the transmit signals and affect AP coverage ranges. There are two antenna types by directionality: omnidirectional and directional antennas. In real-world Wi-Fi environments, directional antennas are mainly used in high-density and backhaul scenarios, and in other scenarios, omnidirectional antennas are generally adopted. With regard to today's antennas, three major difficulties need to be overcome:
- Coverage at the edge: Common omnidirectional antennas have only limited gains. For this reason, they provide good services for short-distance users, but offer only low-speed services or even no services for medium- and long-distance users.
- Coverage over obstacles: In real-world Wi-Fi environments, obstacles, such as planks, glass, and walls, are often unavoidable. Radio signals — when passing through such obstacles between antennas and users — attenuate to different degrees, resulting in poor user experience.
- Coverage in high-density scenarios: In high-density user environments, multi-user concurrency greatly increases interference. To address this, Wi-Fi 5 and Wi-Fi 6 have introduced multi-user technologies such as multi-user multiple-input multiple-output (MU-MIMO) and orthogonal frequency division multiple access (OFDMA). Despite this, user experience near the coverage edge is not significantly improved as expected.
Advantages of Smart Antennas over Common Antennas
Smart antennas effectively improve user experience by providing better coverage at the edge, over obstacles, and in high-density environments. Compared with common antennas, smart antennas have the following advantages:
- Longer coverage distance: Smart antennas improve the signal strength at the same location as before and increase the user-experienced Wi-Fi speed. As such, fewer APs are required, reducing customers' investments.
- Better user experience with coverage over obstacles: The antenna combinations can be flexibly adjusted to enhance the signal strength in the obstacle direction. This in turn increases the user-experienced Wi-Fi speed despite the same attenuation as before. For obstacles that cannot be penetrated, the directions of antenna combinations can also be adjusted to bypass the obstacles by using multipath methods such as reflection and diffraction of radio signals. In this way, uncompromised services are provided for users.
- Lower interference in high-density environments: The directions of signal beams can be adjusted based on user locations, reducing interference between users in different directions while improving the user-experienced Wi-Fi speed.
How Do Smart Antennas Work?
Smart antennas are implemented using beamforming and antenna array technologies. Both technologies leverage combinations of multiple antennas to improve the beams of the transmit signals, thereby improving wireless user experience. By combining the advantages of the two technologies, smart antennas achieve better benefits.
Beamforming, also called transmit Beamforming (TxBF), is a technology that transmits signals to STAs in an energy-focused and directional fashion. It comprehensively improves the quality of signals received by STAs and increases the throughput. Beamforming has been supported since Wi-Fi 4 (802.11n). It can be implemented using multiple common antennas.
In a multi-antenna system, when signals transmitted by different antennas arrive at a location, zero-energy signals may occur if two beams have equal attenuation but opposite phases. Beamforming technology enables two beams to be superimposed with the best effect by pre-compensating the phases of transmit antennas. This approach improves the strength of signals received by STAs, thereby improving user experience.
How beamforming improves the strength of signals received by users
Antenna Array Technology
An antenna array is a beam switching technology, and it consists of a plurality of small antennas. Each small antenna has several antenna elements. Each antenna element can be independently enabled or disabled. In this way, each small antenna can be used as an omnidirectional antenna or a directional antenna. How small antennas are combined is closely related to their gain, polarization, pattern, and the like. Therefore, the numbers of small antennas and their antenna elements directly determine the number of ultimately formed beams. For example, there are four antennas on the 2.4 GHz frequency band, and each antenna has four elements, meaning 16 antenna elements in total. Given that each antenna element can be enabled or disabled, 216 antenna combinations are available in this instance.
Antenna array and element
Drawing on intelligent algorithms, the antenna array can select different antenna combinations to transmit and receive signals and therefore form different signal radiation directions. It selects optimal antenna combinations for STAs in different locations to transmit and receive signals and ultimately form beams. In this way, the strength of signals received by STAs is enhanced, improving user experience.
Antenna array using intelligent algorithms for beam switching
Beamforming + Antenna Array
The antenna array enables multiple antenna combinations, far more than common antennas that support only a single antenna combination. Huawei's smart antenna algorithm selects the optimal antenna combination based on the location of a STA, and then leverages beamforming technology to optimize beams. This approach gives rise to better beams and better directionality than that when only antenna array technology is used. The end result is the further enhanced strength of signals received by STAs, interference suppression, and improved user experience.
Combination of beamforming and antenna array
Huawei offers an extensive range of AirEngine X760 indoor APs that support smart antennas. For more information, see AirEngine Wi-Fi 6 Products.
Benefits of Smart Antennas in Diverse Scenarios
Enhancing Coverage in Medium- and Long-Distance Coverage Scenarios
In an open office area without obstacles, when a user carrying a terminal moves far away from an AP, the smart antenna algorithm selects the most appropriate directional beam based on the terminal location to replace the omnidirectional beam. The directional beam has a high gain; therefore, coverage for medium- and long-distance users is enhanced, including those users at the network edge.
Enhancing coverage in medium- and long-distance coverage scenarios
Enhancing Coverage in Complex Wireless Environments with Obstacles
In office areas with glass partitions and half height partitions, such as partitioned meeting rooms and half height partitioned tea rooms, smart antennas can improve the coverage of APs. In scenarios where signals need to penetrate through walls, directional beams have obvious penetration advantages because they offer high gains. If there are obstacles that cannot be bypassed, smart antennas can select other directional beams to bypass obstacles in multipath modes such as reflection and diffraction, thereby avoiding obvious signal attenuation.
Enhancing coverage in complex wireless environments with obstacles
Enhancing Coverage in High-Density Scenarios with Many Concurrent Users
In offices with high-density users and small interference, MU-MIMO can be enabled to improve data transmission efficiency. In this context, for users in the same direction, smart antennas use the same directional beam for transmission. This improves the strength of signals received by STAs while reducing mutual interference between STA data in different directions.
Enhancing coverage in high-density scenarios with many concurrent users
- Author： Wang Yibo
- Updated on： 2021-09-02
- Views： 362
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