Jamming


#1

Hi,

I’ve been doing some testing with GSM jammer recently. I’ve observed that my Q2687RD with fw 7.44 reboots when the jammer is turned off. I was hoping that 7.45 would fix that issue (they even mention it in the changelog) but what I see is that the modem gets stuck searching for network.

Has anyone noticed done any tests in this area?


#2

Please explain more clearly; eg,

  • what, exactly, do you mean by “stuck” ?

  • Where, exactly, does it get “stuck”?

Not with jamming, but I have seen SiWi devices get “stuck” in the WIND: 7 and/or CREG: 0/2 state after losing registration due to poor signal - even when a good signal returns.

AT+COPS=0 was needed to force the module to re-scan for available networks.

https://forum.sierrawireless.com/t/undocumented-side-effect-of-at-cops-0/4871/1


#3

For example, when the jammer is turned on before the modem starts up, the modem starts to search for network (+CREG: 2), I get some reports from the Jamming Detection API that there is some probability of being jammed. Then I turn the jammer off and I start to periodically receive WM_JAMMING_NULL_STATUS with WM_JAMMING_INTERMEDIATE_EVENT type and then WM_JAMMING_FINAL_EVENT from Jamming Detection API - this is actually the only evidence of network search. They repeat regularly (every 15-30 seconds or so) but no other activity (CREG, WIND) is seen.

Only AT+CFUN=1 helps - the modem registers on the network immediately then.

Yep, I’ve seen that. I’ve also looked at the 7.45 Release Notes that seem to indicate that this kind of problems should be fixed now.

Anyway, just to be safe, I’ve been doing AT+CFUN=4;+CFUN=1,0 regularly if not registered (either “Searching” or “Not searching” state as returned by +CREG) on the network for some defined time (e.g. 15 minutes), then I also tried AT+COPS=0 because I thought that this maybe less energy consuming. I’m not sure now which method, but at least one of them failed for me on 7.44, i.e. I started to receive some errors when executing them.

Eventually, I changed it to a simple AT+CFUN=1 which seems to be more effective but more energy consuming.