using AT-commands, I can obtain the transmission power of the MC7455 module by the !GSTATUS? command.
Unfortunately, the resulting transmission power has no unit assigned. I experienced values in the range of 0 (idle) and approx ~41. How are these values mapped to the actual transmission power of the modem in dBm?
Furthermore, how is this value measured? On a “lte-subframe”-base? Averaged in some way? If so, over which period?
Anyone a clue?
I suspect it is the raw dBm numbers from the power control value supplied to the unit by the network, when I start a session and run a continuous ping off I am seeing a value of 6, how good is your coverage (since you are not seeing one above 0?
thank you for your reply. Unfortunately, this value for tx power cannot be in raw dBm since it has a value range of 0…~41 (or even larger). However, the maximum tx power of LTE UE is 23dBm.
Any other ideas?
As I said below in my comment I am seeing a value of 6, plus I have had it confirmed by one of the RF guys that the figure is in dBm. Trying to get a log file to show this but it is difficult as it is an instantaneous value so just pinging is a bit hit and miss.
Caught the unit transmitting at +11dBm in the attached annotated log file.
GSTATUS power.txt (5.48 KB)
thank you for your detailed investigation.
I also caught the following output from at!gstatus? while performing an outgoing ping in public network under poor radio conditions.
While i see sometimes a tx-power of 23 (which would correspond to the maximum allowed tx power for LTE handsets), I also caught multiple tx-power levels of 47. If this were dBm, this would mean 50W output power, which is in the order of magnitude of a base station
See the attached file for confidence.
tx-power.txt (3.19 KB)
I just verified the tx-power levels using a CMW500 in a wired setup. I can confirm, that in this setup the tx-power value reported by at!gstatus? corresponds to the tx-power of the device in [dBm].
The value range is from -46dBm to 22dBm; requests beyond this range are clipped by the modem to the maximum/minimum supported value.
The value of 0 is ambiguous, since it may correspond to 0 dBm or actually no transmission.
At this point I thank you for your correct information.
But still I have the remaining question of what goes wrong in the given example, where I caught tx-power of 47 in public network? Any suggestions?
Glad you have confirmed it, can’t really comment on the 47 value, no idea what happened there.
I made some further experiments, where I noticed the following reproducable behaviour:
If I unplug the antenna connector during an ongoing transmission via public network (t-mobile, Dortmund, Germany), I notice values above 23 for a short time (approx 1s) before the connection drops. I saw values of 25, 30, 41,…up to 47.
But with CMW500 I could not reproduce this behaviour. The modem raises its tx-power to 22 at maximum and drops the connection. (tested open and closed loop power control).
Anyway, since I now know the value range and the fact, that it is being exceeded only if radio link fails, I can just filter/ignore values beyond 23.
Finally I want to thank you for your great and quick support!
No problems, last point, I would upgrade the unit 2.08 is really old now.