Hello everyone!
Today, I want to share the basics about Wi-Fi signal strength and output power.
Wi-Fi Signal Strength
The most accurate expression of Wi-Fi signal strength is milliwatts (mW), but because of Wi-Fi's ultra-low transmit power, you end up with a lot of decimal places that are hard to read. For example, -40 dBm is 0.0001 mW.
RSSI (Received Signal Strength Indicator) is a common measurement method, but most Wi-Fi adapter vendors treat it differently because it is not standardized. Some adapters use a scale of 0 - 60, while others use 0 - 255.
Ultimately, the simplest and most consistent way to represent signal strength is to use dBm, which represents decibels relative to milliwatts. Since RSSI is handled differently by most Wi-Fi adapters, it is usually converted to dBm to make it consistent and easy to read.
mW - milliwatts (1 mW = 0 dBm)
RSSI - Received Signal Strength Indicator (usually 0-60 or 0-255)
dBm - Decibels in relation to a milliwatt (usually -30 to -100)
So what kind of signal strength should you be looking for?
-70 dBm is a good signal strength for simple low-throughput tasks, such as sending emails, browsing web pages, or scanning barcodes. For higher throughput applications, such as voice over IP or streaming video, -67 dBm is better, and some engineers recommend -65 dBm if you plan to support mobile devices such as phones and tablets.
The data in the chart below may be used as a reference. (Depending on network requirements, the required signal strength will vary.):
Wi-Fi Output Power
The Wi-Fi output power refers to the power received over the air interface. It consists of the conducted power and antenna gain.
Conducted power is the transmit power of the Wi-Fi chip. Antenna gain refers to signal enhancement by the antenna.
Take the ONT in the domestic market as an example. In China, the maximum output power of the ONT with Wi-Fi is 100 mV, that is, the transmit power plus the antenna gain, and the maximum output power cannot exceed 100 mV.
In addition, the output power of ONTs does not need to be transmitted at the maximum power in all scenarios. In some scenarios, the output power needs to be reduced. For example, in the campus network scenario, the distance between dormitories is too close. If the output power of ONTs is too large, mutual interference will be severe. Therefore, the ONT supports five power levels: 100%, 80%, 60%, 40%, and 20%. When the Wi-Fi output power is adjusted based on different levels, only the conducted power can be changed, but the antenna gain cannot be changed.
Different Wi-Fi chips use different power adjustment algorithms for different levels. The following uses Ralink5392 as an example. Assume that the maximum transmitted power of the chip is 100 mV.
Set the power level on the customer interface | Internal Transmit Power (mv) | Decrease Relative Value (dBm) | Actual Transmit Power (mv/dBm) |
91 ~ 100% | 100%*100 | 0 | 100mv/20dBm |
61 ~ 90% | 75%*100 | 1 | 75mv/19dBm |
31 ~ 60% | 50%*100 | 3 | 50mv/17dBm |
16 ~ 30% | 25%*100 | 6 | 25mv/14dBm |
10 ~ 15% | 12.5%*100 | 9 | 12.5mv/11dBm |
0 ~ 9 % | 6.25%*100 | 12 | 6.25mv/8dBm |
Thanks for your reading!
If you know more about Wi-Fi signal strength and output power, please leave a comment in the comments section.
Some Content Sources: metageek
