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GPRS stops working beyond a few meters on master #8

@shaddi

Description

@shaddi

When we try to do a download via GPRS using a Nexus S, things work fine as long as we're roughly in LoS of the BTS. After a point, we start getting this message in the logs when we try to load something:

Apr  2 03:13:40 endaga openbts: NOTICE 16889:17202 2015-04-02T03:13:40.3 TBF.cpp:1125:mtCancel:   03:13:40.3,110222: 03:13:40.3@@@failed tbf cause=108 TBF#256  mtMS= MS#3,TLLI=c0000001,80048002 mtDir=RLCDir::Down#012#011 channels: down=( 0:1 0:2 0:3) up=( 0:2,usf=0 0:3,usf=0)#012#011 mtState==TBFState::DataWaiting1 mtAttached=1 mtTFI=0 mtTlli=0xc0000001 size=0#012#011 mtMsgExpectedBits=0x2 mtMsgAckBits=0x0 mtExpectedAckBSN[1]=111204#012#011 mtUnAckMode=0 OnCCCH=1 mtAssignCounter=7 N3101=22#012#011 msNumDataUSFGrants=0 msAckNackUSFGrant=-1 msOldTlli=0x80048002 Pacch= idle=0#012#011 TimingError=(0.98 min=-1.68 max=2.94 avg=0.88 N=38662) RSSI=(-62 min=-63 max=-24 avg=-47.43 N=38662) CV=(41 min=0 max=63 avg=49.56 N=1120) ILev=(0 min=0 max=8 avg=2.67 N=3) RXQual=(0 min=0 max=4 avg=0.70 N=1075) SigVar=(3 min=0 max=63 avg=7.46 N=1078) ChCoding=(0 min=0 max=3 avg=0.10 N=38315)#012#011 VS=0 VA=0 TxQNum=0 stalled=0 mPrevAckSsn=0 mResendSsn=0#012#011 blocks: total=0 unique=0 grants=0  

This was the channel state immediately before the drop:

OpenBTS> gprs list  
 MS#3,TLLI=c0000001,80048002 rrmode=PacketIdle Bytes:158059up/754546down Utilization=0%  
         GMM Context: imsi=901550000000074 ptmsi=0x1 tlli=0xc0000001 state=GmmRegisteredNormal age=737 idle=1 IPs=192.168.99.1  
         TimingError=(0.98 min=-1.68 max=2.94 avg=0.88 N=38662) RSSI=(-62 min=-63 max=-24 avg=-47.43 N=38662) CV=(41 min=0 max=63 avg=49.56 N=1120) ILev=(0 min=0 max=8 avg=2.67 N=3) RXQual=(0 min=0 max=4 avg=0.70 N=1075) SigVar=(3 min=0 max=63 avg=7.46 N=1078) ChCoding=(0 min=0 max=3 avg=0.10 N=38314)  
         dataER:.3% (66912) recent:0% (0) tbfER:.19% (229)
         rrbpER:.17% (3584) recent:0% (0) ccchER:.0% (151) recent:1.0% (25) low:1.0% (2)  
 TBF#256  mtMS= MS#3,TLLI=c0000001,80048002 mtDir=RLCDir::Down  
         channels: down=( 0:1 0:2 0:3) up=( 0:2,usf=0 0:3,usf=0)  
         mtState==TBFState::DataWaiting1 mtAttached=1 mtTFI=0 mtTlli=0xc0000001 size=0  
 PDCH ARFCN=249 TN=1 FER=0%  
 PDCH ARFCN=249 TN=2 FER=11%
 PDCH ARFCN=249 TN=3 FER=12%  

This was the channel state a moment after:

OpenBTS> gprs list  
 MS#3,TLLI=c0000001,80048002 rrmode=PacketIdle Bytes:158059up/754546down Utilization=0%  
         GMM Context: imsi=901550000000074 ptmsi=0x1 tlli=0xc0000001 state=GmmRegisteredNormal age=739 idle=2 IPs=192.168.99.1  
         TimingError=(0.98 min=-1.68 max=2.94 avg=0.88 N=38662) RSSI=(-62 min=-63 max=-24 avg=-47.43 N=38662) CV=(41 min=0 max=63 avg=49.56 N=1120) ILev=(0 min=0 max=8 avg=2.67 N=3) RXQual=(0 min=0 max=4 avg=0.70 N=1075) SigVar=(3 min=0 max=63 avg=7.46 N=1078) ChCoding=(0 min=0 max=3 avg=0.10 N=38315)  
         dataER:.3% (66912) recent:0% (0) tbfER:.19% (229)  
         rrbpER:.17% (3584) recent:0% (0) ccchER:.0% (154) recent:1.0% (28) low:1.0% (2)  
 TBF#256  mtMS= MS#3,TLLI=c0000001,80048002 mtDir=RLCDir::Down  
         channels: down=( 0:1 0:2 0:3) up=( 0:2,usf=0 0:3,usf=0)  
         mtState==TBFState::Dead mtAttached=1 mtTFI=0 mtTlli=0xc0000001 size=0
 PDCH ARFCN=249 TN=1 FER=0%  
 PDCH ARFCN=249 TN=2 FER=11%  
 PDCH ARFCN=249 TN=3 FER=12%  

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