Wi-Fi devices use antennas to exchange wireless signals with other Wi-Fi devices. Wi-Fi devices with multiple antennas are often able to maintain a stable wireless signal, resulting in faster and more reliable communication within a wireless network. Some Wi-Fi devices with multiple antennas can also send and receive multiple signals at the same time, resulting in significantly faster speeds than single antenna Wi-Fi devices.
Wi-Fi devices communicate with each other through radio signals. These signals are subject to interference that can cause the signal to split into multiple paths. Environmental obstacles, such as walls and ceilings, as well as other wireless devices, including cordless phones and microwave ovens, are all sources of interference. As a Wi-Fi signal encounters interference and splits into multiple paths, the quality of its signal decreases and becomes more difficult for the receiving device to interpret. The signal on the shortest path will arrive at the receiving device before the other signals, and will typically have the least signal distortion. In some cases, the best signal will not reach the receiving device's antenna due to local interference. Single-antenna Wi-Fi devices must settle for the weaker or more distorted single that manages to reach the device's antenna.
Wi-Fi devices with two antennas have an increased chance of receiving a signal with minimal distortion. Wi-Fi devices that use two or more antennas are said to have antenna diversity. On simple devices, only one antenna is used at a time for transmitting or receiving signals. The router automatically determines what antenna is receiving the strongest signal and uses that antenna to receive the current signal and broadcast a response signal.
Multiple Input/Multiple Output
Multiple Input/Multiple Output (MIMO) Wi-Fi devices feature multiple antennas that can be used at the same time for increased transmission speed. For example, a computer with a MIMO Wi-Fi networking card with two antennas can receive two transmissions from a MIMO router with at least two antennas. A wireless network in which only one device features two antennas can still benefit due to antenna diversity. If the network only has one MIMO device, the network's signal quality will increase due to antenna diversity, but it will not receive the speed benefits of MIMO.
A network's environment is the main determining factor behind the difference in speed between a Wi-Fi network with antenna diversity and a Wi-Fi network without it. If two Wi-Fi devices are in use in an open space with little to no interference, neither device needs to have antenna diversity, because both devices are likely to receive a strong signal. A Wi-Fi device with two antennas will show a greater improvement over a device with a single antenna in environments with larger levels of interference. MIMO devices will always show a speed improvement when used with other MIMO devices, even in areas with low interference. For example, a MIMO Wi-Fi device that can send data over a single antenna at speeds up to 300 megabits per second could send data at up to 600 Mbps if it is transmitting to another MIMO device.
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