On Thu, Jun 18, 2009 at 11:58:48PM +0200, Harald Welte wrote:
On Thu, Jun 18, 2009 at 11:32:55PM +0200, Harald Welte wrote:
If we use the knowledge of the behavior as described above, we can also deduct:
the BS-11 is configured to a NM_ATT_RF_MAXPOWR_R of 0, i.e. it will transmit with the power level that is configured by LMT / ipaccess_config. By default this is set to 30mW
the nanoBTS 900 has 20dBm (1800 is 23dBm) TRX output power. bsc_hack is configured to a NM_ATT_RF_MAXPOWR_R of 12, i.e. 24dB. This means we are transmitting with a mere -4dBm (398uW) or -1dBm (794uW) which would be _really_ low. So either the nanoBTS are not following specs, or we're really transmitting something that would barely be possible to receive. Or my calculations are wrong ;)
I've now also realised that every CHANNEL ACTIVATE message contains a BS power and MS power IE with 0x0f as value, i.e. another 30dB decrease in initial power levels. This really makes me suspicious... at levels that low, everything should never be working. Probably the MS and BTS cannot operate below a certain level, and thus they choose whatever is the minimum level they support.
For the BTS I'm still puzzled. For the MS, a power level of 0xf (15) means: 13dBm (19mW) output power in GSM900 and 0dBm (1mW) in GSM1800 - which would probably work well unless there's actual uplink interference on the respective channel.