Ok, this would be a definite house rule. Instead of just cutting off the signal for a device when they go outside their signal range you degrade the signal for each step down the ladder with a -1 Dice Pool for each rating they cross since a signal just doesn’t stop.

For example.

Hacker has a rating 5 signal and can broadcast 4KM. After being stranded on a raft he tries to contact any passing ship within extreme range of his commlink, which would add the previous signal range on top of the maximum range of the signal on the device he is using.

Signal 5: 0-4KM: +/- 0
Signal 4: 4+1KM -1D6
Signal 3: 5-? -2D6
Signal 2: etc -3D6
Signal 1: etc -4D6
Signal 0: etc -5D6

So, If the hacker wants to try contacting someone at extreme signal range (+signal 0) he would suffer -5D6 to his pool due to lag and signal disruption.

There are ramifications with this rule since someone suppressing their signal and keeping it at a low setting would still be able to hack, albeit with slightly limited effectiveness.

Still, the character could also be subjected to signal interception by someone by simply managing in picking up the signal at extreme range even with hefty modifiers.

"Degression"? Do you mean "Degredation" or "Decreasing"?

I've always read signal rating as being the max range you can get a signal across and still communicate any intelligible data at all. Error checking and the like means that you're useful at those ranges, not that you're 100% connected with zero packet loss.

Think cell phones. You get some static, you get some odd blips from cars and things, but you're still communicating without serious issue. When you're at the range where you can barely converse with someone but you're still able to get information across, one of you is getting out towards where I define the max range from "Signal" to be. Beyond that point, you can't get anything meaningful across.

Now, if a player wanted to come up with something like using bursts of static to send morse code, I might dig it giving longer ranges...