10-27-2011 6:55 PM
I have owned a AT&T/Cisco uCell for over 6 month and have now decided to find a solution for drop calls issue. After reaching the limits of ATT support I begun to seek information about that sick box.
As an introduction this device is shrouded with mysteries because there are hardly any available ways to troubleshoot it. Cisco has it locked down tight even to ATT technicians. What little mean of remote management available to ATT has been used by them already to solve common device registration issues (DSL networking, E911 geolocalization). It appears impossible for ATT support techs to address issues related to call disconnects beyond stating: "the uCell won't work at your location"
1- NETWORKING SIDE:
The uCell is connected at all time to the ATT network over a VPN connection on UDP port 4500. It updates its network time with ATT NTP servers on UDP123 couple times per hour and uses TCP port 443 for Https: another secured connection. The good thing here is that there is NO need to unblock incoming Firewall ports because the uCell initiates all connections from within our private network. Incoming data can always be assigned to existing opened connections.
All in all the networking design is rather solid and simple for users. The router MTU settings (1492/1500) may be worth exploring to prevent fragmentation of the uCell UDP.4500 packets if it is hardset at 1492 for aDSL networking...
The bandwidth requirements of the uCell have been kept small to work well within ATT aDSL limits. The up/down streams are below 500Kbps ie. connection bandwidth does NOT cause problem on cable Internet (Dwn: 30,000Kbps /Up: 6,000Kbps) especially if you run a QOS router to prioritize VOIP packet class ahead of any background traffic.
2- CELLULAR SIDE:
The firmware aspect that's half-baked is the cellular radio logic. There is a lot of patented material needed to emulate a cellular radio where Qualcomm is a key player with boat loads of patent attorneys so Cisco may not be playing with a deck of necessary licenses in that field.
Most of the uCell usability issues in my world fall within the cellular category: SMS, Apple 4S, dropped calls, lag time, noisy audio. There is a must-read 13 pages article on Anandtech ("A Comprehensive Exploration" by Brian Klug) about the uCell where one can learn how calls hand-offs should work.
3- TEST SOLUTION:
Armed with the above knowledge I began testing a few original ideas. Living on the outskirt of town ATT reception is a mixed blessing:
- my uCell is picking up to six 3G towers + five 2G towers
- my phone receiption has 1 bar indoors(-103dBm) , 3 bars outside with line of site.
At initialization the uCell does:
- builds a list of adjacent cellular towers
- sets its cellular frequency: 900MHz or 2.1GHz
- adjust its power output to match the reception level in its environment
- geolocalize either by 1/ cellular triangulation or 2/ by GPs signal
When the uCell is initialized without receiving 3G/2G macro-tower signals:
- has a clean/lean list of adjacent towers to process call hand-offs
- has to use GPS signal to geolocalize E911 address instead of triangulating 3G towers.
- it outputs a stronger signal inside the house for solid calls
Reset button while powered followed by GPS-only initialization with limited macrocell reception.
1- Made a shield with aluminum foil to cover everything but the GPS receptor antenna and LED's
2- Stuck the Reset button with a toothpick for 30 seconds without powering down the unit
3- Removed the antenna shield after all green lights (~10 minutes)
On "3G data" I now get 2,300 Kbps download and 300 Kbps uploads, stronger in-house coverage and so far no dropped calls but keeping my fingers crossed for more off peak testing.
11-03-2011 3:14 PM
GeorGiacc: for you that means you need to keep your uCell with sky view for its nightly locale validation.
Use PowerLine modules with your uCell - They work great to bypass wifi coverage issues as well.
From the spaghetti logic in this support document I kind of understood that on the 2nd night the uCell will geolocate with towers even if it was GPS activated.
The document does not say if that tower list is used or not by the uCell to hand-off calls afterwards. I would think Yes but it seems to me like No.
Credit where du: AT&T does publish nice internal support documents for CSR to dive into!
11-03-2011 9:20 PM
11-04-2011 1:11 PM
[I read the support document as saying it checks it's location nightly based on local cell towers. Since I likely had 0 neighbors the night before, and now have probably a dozen or more, it probably kept the list of neighbors.]
> yes I think so too. What the support document does not say is if the neighboring towers list refreshed nightly is used only for validating the unit location every night or for the cellular operation as well. We could use more info from ATT... but again if everything was cristal-clear on the ATT side they would have a working design and we would not be here trying to paste broken pieces together.
[So do I keep it covered with my metal mesh every night to prevent it building a list of neighbors? ]
> NO-NO - I don't think more shielding is better!! Whatever you are testing this unit needs cooling to dissipate internal heat. If you build a good signal shield it will likely be somewhat air tight.
I use my shield only during warm-boot initializations lasting about 10 minutes or less.
Everyone being responsible for his own actions: you risk damaging the uCell unit if it is operated with restricted air flow. Whatever power this unit is drawing on its AC cube needs to get vented out!
If you blow an internal fuse protection, don't even think about cracking the uCell open because this unit has a temper switch that will disable itself dead upon intrusion. Not a wise path to travel.
[2 things I noticed today: the signal from the MC seems to be stronger than before the reset, though it still prematurely hands-away to the macro network. Several times today I noticed that our iPhones were not connected to the MC, while my BlackBerry was.]
> So it looks like you got a more effective Reset this time because getting higher transmit power is the desired side effect of shielded init test.
- Can you describe the reset button timing and LED behavior during your reset??
Regarding the premature handing to a Tower pls read bellow. In essence as long as your cell phones are happy with the street signal level (bars), they are going to hug a tower and not get on the uCell. It is only when the uCell offers a stronger signal that the phone switches over while idle.
[Without the MC I get 1-5 bars reception from macro cells throughout the house depending on what room and level I am on. It's just not reliable because the line-of-sight cells are 5-15 miles away.]
> You can not expect the uCell to compete with a 5 bars tower!
Inside your house, you need to learn where you have good tower reception vs. bad reception then place the uCell in the center of that bad zone.
Getting a clean list of neighboring towers is to make sure the uCell does not hand you out to ghost towers your phone can not reach thus dropping your calls (This is the firmware bug that need to be walked around).
They are always going to be issues with handing calls over because it is a one way process. Once your cell phone call is transferred to a tower, you can't transfer back on the uCell until you hang-up the call. What that means is: don't go walking around the house on a cellular call between the tower coverage area back towards the uCell only coverage zone because by design the call is 99% guaranteed to drop. Once we are aware of that limitation, it should be easy to leave with it.
Users who have zero towers available do not have this "transfer back" limitation because their calls should always remain on the uCell provided the firmware bug let them have good indoor coverage. Their cell phone has the ability to range far but not the uCell due to its very limited transmit power (~5mW?) and building echoes (S/N ratio). That we have to leave with as well because it is expected by design.
11-05-2011 6:11 AM
11-05-2011 11:38 PM
Having line of sight, your phone should not switch from 5 bars on uCell to 2 bars macroCell. This is what this thread should help you fix. The shield + reset should bring you joy or perhaps there is something special on the networking side that makes my setup special. How is your uCell connected to your network?
I used a 30sec Reset timing from the standard "30-30-30" reset for router firmwares.
For your case I would make sure to sit on that reset button for at least 30 sec or more - This should give you a warm boot! Perhaps longer than 30 sec but I don't think anything extra happens after that - Who knows if you keep poking that box you may learn something new.