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UMA Questions Answered
Posted on: 2008-12-20 10:08:32
Geez, I just went through my server logs and it is clear that people have lots of questions on UMA. Whenever someone asks a question in Google, and my web page pops up, and they click on it, I can see what they typed into Google. So in a way, all of you people on the Internet are able to tell me what to write about. So here is my page with what you want to know about UMA.

Because I work for RIM, there is a general employee directive to not give any technical support online. So this article relates to all cell phones in general. I certainly don't want to get fired. (Ssssh! They don't know about this blog). Oh yeah, almost forgot:

The postings on this site are my own and don't necessarily represent the position, opinions or strategies of RIM

You might also be interested in my general description of UMA, and whether you can get free long distance over UMA.

"how does UMA connection work"

From your perspective, you get one phone number that will work over your Internet connection when you are at home, and over cell towers when you are outside. If you travel to another country, you could possibly make calls to your home town and not be charged long distance. However, UMA is not skype. Other than that exact situation, you will normally be charged for long distance calls depending on your plan.

Normally your phone sends its signals to a cell tower, which forwards it to a server on the carrier's network. With UMA, your phone logs into the carrier's network through your internet connection and sends its signals directly to that server. That means you can access all of the same services over UMA, like voice, data, and SMS. Unfortunately, it means that all of those same services go through your carrier's network, perhaps unnecessarily. Some phones support something called "Internet Offload", in which UMA is only used for voice calls, but all the data goes directly over the Internet. Got it?

"connecting a uma phone to the network."

Connecting UMA is hard. Normal cell phones are designed so that any idiot with a bank account can use them. But unfortunately, UMA is based on the Wifi network, and Wifi has a lot of lot of things that you can screw up. To connect to UMA, six things have to happen:

  1. Your cell phone has to be specifically designed for UMA. It has to contain a Wifi radio on it, or it just isn't going to work. You can't take your 10 year old Motorola and sign up for UMA service. It has to be fairly new -- probably made in the last two years. Furthermore, it has to contain the UMA software on it. You pretty much have to have the phone and OS designed to accommodate UMA, because the UMA application needs direct access to secure sockets, audio, and SIM card security functions.
  2. You have to sign up for UMA service with your carrier. Their security gateway knows whether you are paying for their service and it won't let you through if you didn't sign up.
  3. You have to have the security certificate installed on your phone. Each carrier (for example, T-Mobile, or Rogers in Canada) has a certificate that has to be loaded onto your phone for you to connect. It is kind of like a password, but it is far too long to type in manually, so it has to be loaded with special software. This probably happened when your phone was manufactured and customized for the carrier. Unfortunately, that means that it is locked to a particular carrier, unless you can figure out a way to load a new certificate. This is what gives people problems when they try to use a phone bought on ebay.
  4. You have to successfully connect to Wifi. This will involve scanning for the Wifi network using your phone, and probably entering a WEP or WPA password of some kind. You should try this on your laptop first, to see if your Internet is set up properly. If your laptop can't connect, then there is some other problem with your Wifi router.
  5. Your phone has to be configured to use the UMA connection. The mobile phone standards dictate that all phones have to have some way of choosing how UMA is used. You have to be able to choose between cellular-only, cellular-preferred, UMA only, and UMA preferred modes of operation. The only option that makes sense is UMA-preferred. (This is sometimes called "Wifi preferred")
  6. Finally, UMA must successfully connect. Turn off your microwave oven. Stop bittorrent. At this point, one missed packet can cause a huge delay. The connection phase retry can take up to 32 minutes, because the mobile standards describe a precise scheme of retries. Specifically, it tries three times, waiting 30 seconds between tries. If those tries fails, it waits 2 minutes, then tries three more times. On failure, it doubles the two minutes to 4 minutes, and so forth, until it eventually waits 32 minutes between retries. Then it stops doubling the timeout. To avoid the 32 minute wait, you can probably make it try again immediately by turning off and on the phone.

"how to use uma phone without sim"

It is not possible to use UMA without signing up for an UMA plan with a carrier. That is because the SIM card actually performs the authentication process to login to UMA. No SIM means no UMA.

"does uma work over different carriers"

If you travel, you can use your UMA phone to connect to your home carrier and make calls without roaming charges. Your main problem will be connecting your phone to wireless hotspots, because often you will have to login to the hotspot and click "I agree" to some usage agreement. If your phone browser isn't able to display the button, then you won't be able to connect to Wifi. But if you pass this hurdle, your phone should work fine. Just make sure it is actually using the UMA network when you make your call. In this case, it might be good to set it to UMA only mode.

"how to make uma server"

So you want to make an UMA server so you can run your own phone service. Okay, well, first you have to remember that UMA is simply a wrapper around the regular cell phone messages so they can be transported over the Internet. So all you have to do is implement the entire rest of that phone network. Feel free to download the 3GPP specifications and implement your own phone network. Don't let me stop you. Out of the 1,000,000 pages of telephony standards, I think you'd only have to read about 50,000.

Or you could just go write a SIP server like a normal person.

"which carriers have uma"

Umm, I don't know. I know T-Mobile US is doing it and Rogers Canada is as well. There is a complete list on wikipedia.

"best uma phone"

The best UMA cell phone is the BlackBerry, which does support Internet Offload. The latest model at this point is the 8900. Go out and buy that one as soon as you can. But be careful if it is used.

"UMA skype"

Skype shouldn't be used over UMA, because as I have said, on most phones, all data goes through the carriers servers, and is chargeable. Your Skype usage would cost thousands of dollars in data charges. If your phone supports Skype and Wifi, and you can turn of UMA, do so to avoid these charges.

"is uma service free"

That depends on your plan and contract. You did read it, didn't you? Usually you have to pay extra for UMA, but then you get unlimited calling while on UMA. But read your plan very carefully.

If you make long distance calls, you will probably be charged extra.

But the number one search topic for UMA is:

"uma nude"

I don't have all the answers about UMA! For that, you'll have to look elsewhere.

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x-UNIX Admin

2009-04-24 23:16:28
I've been using T-mobile w/bBerry handsets for close to two years now. I've tried all kinds of combinations of routers, QOS settings, and on and on...only to run into the same dead ends.

What is the best router to use with T-Mobile's UMA? Please don't say T-Mobile's routers...their routers have the same problems with what appears to be outside interference.

Also, would it be correct to say that UMA is the ideal solution for someone who doesn't have a tower, or neighbor with a Wi-Fi network for....let's say a 10 mile radius?

I've come to the conclusion that a densely packed Wi-Fi urban setting just isn't conducive to excellent UMA service because your neighbors' cordless phones and Wi-Fi networks are constantly interfering with communications between the UMA enabled handset and the handset's wireless router.

Would someone please send me an e-mail with suggestions before I make myself wacko over UMA ;-)


2009-05-09 03:48:22
I've been seeing mostly the same issues. The older Belkin Pre-N with Airgo chipset (F5D8230-4 version 1002) and the T-Mobile WRTU54G-TM seem to be the most reliable. My DD-WRT client bridges won't stay connected to the WRTU54G-TM which is very irritating. I've tried at least 10 different wireless routers and many configurations. From what I can see ISP's alter QOS TOS values from T-Mobile towards UMA phones which forces packets to be thrown into Best Effort 802.11e queues instead of correct AC_VO queues. The packets don't get the transmit+re-transmit priority they're supposed to with Non-Tmobile routers.


2009-05-09 04:05:32
Correction. The Belkin Pre-N version of the F5D8230-4 I've been using is version 2001 not 1002. I only use it as an access point because the routing functions are pathetic and unstable. Belkin doesn't seem to care about fixing bugs in their software. It seems to work great as an access point though. I think the Linksys WRT54GX V2 is almost identical to this wireless router. Download the demo version of OmniPeek if you want to see what's happening with UMA on wireless.


2009-05-11 16:36:40
The one thing that seems to be common throughout my testing is that wireless routers with the Broadcom wireless chipsets do not seem to work well with my Nokia6301 phone. I've tried both DD-WRT and Tomato with all the suggested settings found with google. The only two so far that work well consistently are the Belkin Pre-N with the Airgo Chipset mentioned above and the WRTU54G-TM with the Ralink wireless chipset.


2009-05-16 03:52:59
If you have a Wireless Router with a Broadcom chipset and are having issues with UMA, try re-configuring it to B-only wireless mode. It has made a significant difference with keeping connections with my Nokia 6301 phone.


2009-07-23 01:30:56
I'm in a pretty dense urban area (13-15 other wifi networks showing in regular scans) using a secured "Linksys WRT54GP2 Wireless-G Broadband Router", T-Mobile carrier and a BlackBerry 8900. Haven't had a single issue since setting up UMA.

Jon Strong

2009-08-05 21:12:22
I've been dabbling with UMA since getting my 8900 the week T-Mobile first made them available in the US. Great BB (having had the 8700, 8100, 8800, 8300 before).

First few months experience with UMA was mixed: great for email, SMS, MMS, web browsing, youtube, Pandora, Slacker. But any time I tried a voice call, it would start out great and then drop the call abruptly after a few minutes.

I finally did some pretty extensive searching, and found some info about tweaking router settings. Unfortunately, it's always a challenge separating the legitimate info like this from the urban legends. But I narrowed it all down to what seemed most credible, made the changes in my router settings, and UMA has been spectacular ever since. I can now make 45 minute phone calls - crystal clear, no drops, etc, and all the other data services are still excellent.

First -- my ISP is Verizon -- using FIOS for TV and Internet, and also for a spare phone line, although the 5 primary home phones are handled through T-Mobile@Home service (their UMA/VoIP offering as a landline replacement).

The first router on the incoming line is the Actiontec provided by Verizon. I have the TV set top boxes connected to this (required), as well as the five PC's and various printers, NAS's, etc. Then I also have the T-Mobile Linksys WRTU54G-TM router plugged into the Actiontec as well.

The WRTU54G-TM supports the five house phones (DECT 6 base station plugged into the router), and I also use it to support the WiFi setup in the house. This is what my 8900 connects to.

By default, WMM (wireless QoS) is turned on with this router, at least with the latest firmware release. So I leave this on. What I believe really made the difference was the change in the "Advanced Wireless Settings", as follows:

- Advanced Wireless Settings

..[only listing non-default settings here]..

--- Beacon Interval -- 50 (default is 100)

--- Fragmentation Threshold -- 2304 (default is 2346)

--- RTS Threshold -- 2304 (default is 2307)

Anyway - ever since doing this, UMA has been spectacular with the 8900 at home, and it's now dependable enough so I can use it for business calls in my home office, which was my initial intention.

I just wish that RIM and/or T-Mobile would provide more information supporting UMA, since SO many people continue to have issues with it (stuttering, dropping, etc -- primarily with home routers). Real solid meaty info is very hard to come by!

- Jon


btw: if you care to email me back, my address is jonstrong at the domain name above...


2009-09-10 18:23:32
Hi. Thanks for your info. Here's my situation: I have a new T Mob BB 8900. (it was gifted from a friend in europe and is locked to the t mobile croatia network) I'm working on getting it unlocked so I can put my AT&T card into it. (right now it won't work with it). The first thing I should mention is that when I put my brother's T Mob sim card into it, it works. However, "UMA" doesn't come up as it does on his T Mob Pearl 8120. (??) The next question is: Does BB make the same 8900 for T Mob here in the USA as it does in foreign countries? (Croatia in this case) The third and probably most interesting question is that my as my brother's T Mob Pearl 8120 has UMA capability, he had never signed up to get charged for it by T Mob. (he didn't even know that the phone had the capability until I discovered it myself yesterday) Yet, I made a call to Croatia late last night (while the "UMA" was displayed in the upper right hand corner) from my wi-fi connection in my house. Just to be sure that the call was connected via UMA wifi, I've been checking to see if any record was made of that call yet on his T Mobile account online. So far, nothing. Am I to believe that that international call was completely "free". Free meaning that he never paid a $9.99 monthly charge for the service nor was a per minute rate charged for the call. (?) If that's the case I'll leave AT&T (termination fee and all) and sign on with T Mobile. But I just need to confirm all the above as I'm learning as I go. Thanks! Please reply!

Steve Hanov

2009-09-11 08:50:33
Sorry, Allen!

Unfortunately I can't provide technical support for BlackBerry because I work for the company and it is forbidden to do this.


2010-01-09 02:06:22
Just reading over this info I believe I spotted an error. I believe Steve said is not possible to use UMA without signing up for an UMA plan with a carrier.

That's not quite correct. You can use UMA without signing up for an UMA plan.

We do it all the time at home. You just need to connect to your wireless network at home and you're good to go. No T-Mobile UMA plan required.


2010-02-20 22:23:56
@Barry: does it mean I can buy a T-mobile handset (or UMA enabled handset), put non T-mobile SIM and I will be able to use UMA feature?


2010-09-03 04:17:47

On Orange in the UK data works slightly differently.

When you connect through UMA on a wifi connection - although the data is passing through Orange, you are not charged or does not come off a data allowance. So you can use as much data as you want (depending on your wifi constraints!)

My only question is: I\'m off to the middle east soon. The hotel I\'m staying at has free wifi. Will UMA connect? Will Orange UK charge my calls any differently?



2010-09-25 23:05:48
I wonder if I can use my registered by T-Mobile SIM card from UMA cell phone, like Nokia 6086 with router WRTU54G-TM connected to internet to use regular phone for dialing out and receiving call. Is (discontinued for new customers) @Home service needed in this case?

Thank you for help. Please respond to bayconnection@gmail.com. Joseph


2010-10-07 21:15:40
Hey Steve,

Great post here on UMA thanks.

I'm familiar w/ T-mob USA and BB/UMA in general (my whole family on it for several years and love it). Now I'm in business from London with a partner based in Paris. I want to setup a company business mobile service plan with Orange UK who have exclusive UMA facilities in UK (and operate in four other countries of EU, including France). If both partner and I use BB/UMA handsets from Orange UK (on Orange UK biz calling plan w/ pooled call minutes, etc.) and we each have wi-fi connectivity in our respective offices in London/Paris, then if we connect on UMA in both London and Paris (or at least my partner on Wi-Fi/UMA and I use either Wi-Fi or UK 3GSM OTA service) will we be able to talk and make phone calls to each other and UK numbers (and international, I suppose) using the UK in-plan call minutes as if my partner was co-located in London? Of course he carries the UK phone number on his business mobile in Paris.

My experience with T-mob/USA would indicate yes but I notice the following clause in the Orange user agreement T&C's:

"UMA Phone for Business will not connect to (a) a public wifi hotspot or (b) to a livebox or other wireless router whilst roaming abroad (however the handset may be able to roam on available mobile networks)."

Does this make sense to you? A quick survey on Google would suggest that probably not but there's no definitive statement from anyone recently. If Orange UMA really doesn't work outside UK (or even my home/office Wi-Fi connection) then it would seem that Orange is pairing the phone UMA service to the 'home' router MAC address and verifying against it using HLR or something. Any way to get around this point?

BTW my partner is on Orange France broadband in Paris over a Livebox Wi-Fi router, and he would 'pair' it as such on the new service connect (not on the UK office Wi-Fi).

Many thanks again in advance for your advice/comments.





2010-12-17 00:49:06
How does the delivery and identification of web page version to a mobile client (cell phone) in UMA takes place i.e. over WiFi or GPRS/UMTS?

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