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I've recently bought some wireless access points from Draytek. I understand what most of the settings do but I'm trying to fine-tune the roaming behaviour and there's one setting which my colleagues and I can't make sense of. In the AP-assisted Client Roaming Parameters section, I've got two fields/options enabled:

Minimum RSSI = -66 dBm (60%) (default value)

with Adjacent AP RSSI over = 5 dB (default value)

Here's a screenshot of the settings page:

Screenshot from web UI on VigorAP 903

The gist seems quite simple to me: only 'hand over' a client to a new AP when the current connection is below signal strength X, and there's another AP available with signal strength over Y.

What I don't understand is why the first field uses dBm (with a negative value) and the second one uses dB (with a positive value). I've read this post from Draytek, but I still don't really understand how the signal strength could ever be -5dB let a lone +5dB. In my tests, my laptop never goes over -30dB even when it's right next to an AP on my desk.

Roaming is working when I move around the building, but I want to understand this properly before I start messing with it.

Peregrino69
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Vilāsamuni
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1 Answers1

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"Roaming is working when I move around the building"

Roaming = client changes connection from one AP to another broadcasting the same SSID. So unless you have multiple APs broadcasting the same SSID, you're not roaming.

What this means is simply that when RSSI (Received Signal Strength Indicator) from the client on AP 1 drops below -66dB and AP 2 detects it with 5dB higher RSSI (-59dB) the AP will force the client to roam; i.e. terminate connection with AP 1 so it connects to AP 2.

Strictly Minimum RSSI isn't enabled. If it is, the AP will terminate connection to the client when the RSSI drops below the named value whether or not another AP is available.

The RSSI is measured with negative dB scale. That means the theoretical max is 0dB; you'll never see a positive value.

Peregrino69
  • 5,004