Ten Common Misconceptions About Wifi (2)
5. Uplink rate and downlink rate
The only rate generally accepted in the industry is the transfer rate. However, asymmetric rates are typical, and the send rates seen by our connectable clients are not necessarily indicative of the receive rates. This is also confirmed in terms of access points and infrastructure, which proves that in the WiFi world there are separate uplink rates Tx and downlink rates Rx.
6. Same transmit power for all rates
Setting an access point's radio to "maximum power" does not mean that the power is available for all rates. The default wireless transmit power is set to 20dBm. Typically, the higher the data rate in use, the access point will be forced to power down these frames (as defined by the FCC and ETSI). This concept has become more common with the 802.11ac VHT specification.
7. Always set the radio to max power
Setting the radio to max power might seem like a good thing to do, but it's probably not a good idea. It has been proven that when the radio is emitting sound at maximum power, signal distortion occurs. There are many reasons for this to happen, including cell size planning. Just maxing out the radio power is not a best practice.
8. Signal Strength to Signal-to-Noise Ratio (SNR)
There is often confusion between the measurement of signal strength and the measurement of signal-to-noise ratio. In fact, the performance of a WiFi network depends in part on signal strength. Between a computer and a wireless access point, the signal strength in each direction determines the available data rate for that connection. Therefore, the stronger the signal, the better the connection. The signal-to-noise ratio is preferably a large number, which means that there is a large difference between the strong signal received and the background noise that affects the overall quality.
9. MIMO and Spatial Streaming
MIMO and spatial streams are probably the most confusing issues since the 802.11n protocol. Multiple-input and multiple-output (MIMO) technology is a wireless technology that uses multiple transmitters and receivers to transmit more data simultaneously. All wireless products with 802.11n support MIMO, part of the technology that allows 802.11n to achieve higher speeds than those without 802.11n support. MIMO involves antennas and paths, and the number used indicates how many antennas and paths can be used to transmit and receive signals. For example, 3x3 means 3 antennas and paths transmit and 3 antennas and paths receive.
Spatial streams involve the actual data being sent. For example, a 3-way spatial stream device can send 3 unique data streams to the receiving station and be reconstructed as a data set. Finally, adding MIMO and spatial streams equates to the overall achievable throughput. 3x3:3 means that when 3 spatial streams are transmitted, 3 antennas and paths are used for transmission and 3 antennas and paths for reception.
10. The respective capabilities of the access point and the client
This is a very simple question, but often overlooked, the lowest common denominator always wins. To achieve the highest data rates and real-world throughput, access points and clients must be capable. It is important to understand the capabilities of the client to really understand what kind of WLAN deployment will be possible in the real world.
