Jan 30thHow Phone will Travel
If a wireless phone tower only covers a few square miles, how is it, I can travel for miles and never drop my call with the person I am talking to?
This question is one that has been asked many times by new employees at my previous company.
The first thing I will need to explain to you are some basic wireless terms that will be used in this article.
1) BTS: Stands for Base Station Controller. It is a fancy name for a cell site
2) BSC: Base Station Controller. Controls all messaging back and forth to the BTS
3) MSC: Mobile Station Controller. This is the main switching computer that controls the BSC and all call traffic
4) CDMA/GSM or UMTS: These are different Digital Technologies used by wireless carriers
Now let’s start talking a little about how this all works.
First you will need to set up a call on your wireless phone. Once you are on that particular call you begin driving down the road. There is a slight difference in this process between GSM and CDMA. I will attempt to point them out as we go through this. As you are on the phone, your signal is constantly being monitored and evaluated, also each BTS on the BSC has a database that lists all the corresponding sites around it that a customer could possibly drive into the area of.
The next step there is a difference in how it works:
CDMA / UMTS: In CDMA and UMTS, your call is actually being processed but all the surrounding sites at the same time. The BSC monitors the signal quality on the call and as you drive, the levels will get better on one site over another and the BSC just process the call on the best quality site. As you drive on, your noise level changes, and the BSC will just process the call from the new site. This is called Soft Hand Off’s. As you drive on, this process is just repeated over and over with the sites going down the road based on the BSC database listing of the surrounding sites.
GSM: In GSM it works a little different. The calls are not actually processed over multiple sites at one time, because the phone in GSM is forced to retune to a different Freq every time you move from one site to another. So how it works, is it just monitors your signal level on all surrounding sites based on the BSC database. Then once your signal level is stronger on one of the neighbor sites than the one you currently are on, the phone receives a message from the BSC telling it to retune to the channel of the neighbor site and the phone retunes and the call hands off.
Because of these differences, if you listen closely, you may hear a small click or a word of audio may be muted because of the retuning of the phone. In CDMA, all sites actually operate on the same frequency and it performs a Soft Hand Off, so it is seamless to the customer and device.
The signal levels that these processes us to compare and performed at are also set by the carrier in their BSC database.
The number one reason for a consumer to drop their call is usually a neighbor cell site is not loaded properly in the BSC as a hand off candidate or that possibly the signal levels that are set in the database may need to be adjusted slightly. This process is not an exact art for all situations so drop calls will happen that cannot be explained.
Now let me explain quickly how this whole process works when you drive on a road where one area is on one wireless carrier system and the other area is on someone else’s wireless system. Because this requires two different carriers to be involved, many times your calls will just drop because the two carriers have not gone into an agreement among themselves, most of the times this is due to costs associated in putting the process in place.
If both carriers decide they want to put this in place, it is very similar to what already happens above. The difference is, that the BSC database also has to have information on the neighbor BTS’s. However, when it needs to get info of the neighbor’s site it has to communicate over a link that is put in place connecting the two companies. If the call actually reaches levels that it hands off the call, the neighbor has to take the audio for that call also and that requires some sophisticated signaling and trunking to be in place. Also due to the time it takes for all this messaging to take place between carriers, it is not uncommon for the calls to drop if the areas terrain is hilly or the customer drives too quickly through. The costs associated with this, is the main reason carriers do not put this in place. You will usually only see this in place if the area in question is on a major interstate or where there is enough traffic to justify not dropping the calls.
I hope this all made sense to you and if not feel free to drop me a note or comment and I will try to answer your questions for you.
Related articles
- What is 4G Wireless Technology (lifetraveler.net)
- Can U.S. Cell Phone Carriers Learn to Share? (pcmag.com)
- Travel With a Smartphone? 3 Things to Check Before You Buy (pcworld.com)
Jan 3rdWhy Don’t I Have Cell Phone Service
After more than 20 years as a Switch Engineer and part owner for a major wireless carrier, I still find the most common question I am asked even though I am retired is “Why Don’t I Have Cell Phone Service”. This is really not a very difficult question to answer once you have the understanding of how cell phones work and the different carriers you may have service through.
First let me explain that there are two major types of Digital Phones. One is CDMA which is the main service carriers like Verizon and Sprint use and then there’s GSM which is what AT&T and T-Mobile use. There are a few others but they are not as widely used in the industry at this time. These two digital technologies operate totally different from each other and are not compatible with each other. In other words at this time you cannot use a Verizon phone on a AT&T system and vice versa.
Now let’s say you are standing next to your friend and he has phone service and you do not. Most likely one of you has a CDMA phone and the other is a GSM phone. Let’s say Friend “A” is on AT&T and Friend “B” is on Verizon. Since these digital technologies are not compatible at this time then it would require both carriers to have a Cell Site system in the general area as to where you are. Keep in mind in a perfect world (Flat with no trees) a cell site will talk on average about 20 air miles. So you will both need to be within that distance to the cell tower. As we all know it’s not a perfect world so expect anywhere from 10 to 15 miles in Rural country and up to 5 miles in Urban. That is the basics of the causes. Now let me explain why there isn’t always a tower where people think there should be one.
Below I will be listing some numbers. These numbers are for reference only and will be adjusted by each carrier based on their business model. But the numbers I use are very close to what they may use.
First thing that will determine if a carrier places a cell tower in a general area is how much revenue they can generate and what is the total payback of the site. This means how many calls will be made and how many years it will take for the site to break even between build and maintenance costs and revenue. On most systems they shoot for a 24 to 48 month payback. They also look at things such as population and road traffic. They will need to see if they can get on average about 2000 customers in the area. Thus based on the population and the number of other carriers in the area this can become quite difficult in small populated areas. The Average cost for a cell site is about $750K. This includes everything from a tower to equipment and man power to get it up and running from scratch.
Let’s say a carrier can now justify a tower in a particular area. The next biggest hurdle they run into is local governments and the citizens themselves. Everyone wants Cell Phone service but no one wants a tower in the area where they can see it and take away from their view. Most people want their cake and eat it too. Also a lot of local Governments have instituted a ban on new towers and thus this makes it even more difficult. Then of course you have things like the FAA if you are near an Airport.
If for one of the above reasons a carrier cannot put a tower up where they would like. They now are forced to co-locate on another tower in the area. This is being done more and more but this also causes other issues. The higher on the tower you place the antenna’s the better coverage you can get. Thus, the first one or owner will usually get better coverage. If one carrier has to share a tower with another, this means that the first carrier will have an advantage over the other. Thus making it hard to get customers the service they want and expect. Also, if they are competing against each other, the one carrier that owns the tower can make the lease so high that it takes the second carrier beyond their justification for being in the area to begin with. In other words carrier “A” can make it too expensive to compete against carrier “B” in an area.
Now you see why one person can have phone service in an area and another doesn’t. This is why it’s important for the consumer to look at where they want their phone to work before they sign a contract with a carrier. Most places, if Carrier “A” isn’t there and Carrier “B” is, you may have a chance to roam but then Carrier “C” must be using the same digital technology that you have for it to work.
Related articles
- Troubleshooting Common Cell Phone Reception Issues in Buildings (mycricket.com)
- How Phone will Travel (lifetraveler.net)
- Can we count on cell networks in disasters? (cbsnews.com)
Dec 26thKeeping International Roaming Charges Down
One of the most expensive thing for International travelers or just people that are just going on a short vacation are the wireless roaming charges you will incur when outside your home country. There are many ways to try and keep International roaming charges to manageable levels but only if you pay attention to how you are going to use your wireless phone.
The first obstacle you will have when traveling with your wireless phone is the obstacle of just making sure it will even work at your traveling location. Until LTE becomes more of a deployed system worldwide there are only 2 basic types of digital technology that phones and wireless carriers use in their networks.
CDMA: This is the digital technology that carriers such as Verizon and Sprint chose to use in their home markets.
GSM/UMTS: This digital technology is used by AT&T and T-Mobile type carriers. These phones are easily identified because they use something called SIM cards that store all your phone information on them. The SIM card can be located behind the battery.
World Phones: This phone is a combination of these two digital technologies. They became popular a few years ago and have grown drastically especially among travels. This phone will actually work on both technologies. It will first prefer the home carrier type of digital technology and if it is not able to locate a compatible system it will fail over to the other.
The main issue when using CDMA or UMTS only phones is that in many countries and remote vacation islands you may only have one carrier operating there. When that is the case you phone may or may not work pending if the local technology is compatible with your phone. This is why the World phone has gained popularity over the years with travelers, as it eliminates the one major obstacle you could run into.
Now that you have arrived at your foreign location and you do have wireless service with the local carrier, it’s important to try and keep your costs down as international roaming fees can be very expensive. Always check with your phone carrier to get accurate costs before you travel. Some carriers will offer an international roaming feature for your phone. This is especially true for those that have world phones.
If you are using a world phone or a smart phone it should be WiFi capable and this will be the best method for you to keep the costs down. Almost every hotel and even some restaurants offer free WiFi to its guest. If this is the case where you are traveling, all you have to do is put it in WiFi mode and that will allow you to make a Voip call at no cost to you at all. If you travel a lot to a location that doesn’t offer free WiFi but does offer free data service in your hotel then take along with you a Wireless router and turn the hotels data connection in your room to a WiFi signal and that will allow your phone to lock on it for use. This last method is actually the one I use when traveling so I can keep in touch with my daughter back in the states for little to no costs.
Another way to save money when international is with your Text Messaging. This can also be very costly if you tend to do this instead of calling people or emailing. Most international areas charge you as much as 50 cents per text message you send. Your text messaging service you have at home, so many messages for a flat fee, doesn’t apply when roaming internationally. There are new App’s available for smart phones that allow you to send and receive text messages without actually using the text option on your phone. If you are again on a free Wifi system you can use this App and not pay the international roaming charges. The only downfall to this is that you must have some kind of Smart Phone that allows you to use the Apps.
In closing, let me say that there are many ways to keep your costs down when traveling internationally. You just need to do a little planning and thinking it through before you go there and receive your wireless bill from your visit upon your return home. There is one method that I have not listed here and this method is only usable by the person traveling on vacation. That method is to just plain turn your phone off and enjoy your vacation. If you are with the family, like you should be, there is no reason to need to call anyone anyway. Enjoy and Relax, you don’t get to travel internationally very often most likely. You are likely in a very nice location that you want to enjoy and savor the memories.
Dec 18thWhy Can’t I Use My Old Phone on My New Wireless Carrier?
First let me start off by saying that I do not write these articles about the Wireless Phone Business to defend the carriers and the way they operate. I would be the first to tell you that from my experience in the industry for many years running one of them, that it is a business like everything else an it’s all about maximizing rate of return on investment when it comes to customers and charges.
I get asked a lot from people when they learn who I am, as to why when they switch from one carrier to another they usually have to purchase a new phone? This is actually a very simple answer but I will need to explain in more detail how a phone or data device works for you to understand.
First thing you have to understand that until everyone goes to LTE technology, that there are basically two types of Digital systems made in the wireless industry.
1) The first is CDMA which is the technology used by such carriers such as Verizon and Sprint
2) The second is GSM/UMTS which is the technology used by Carriers such as AT&T and T-Mobile
The first reason you can’t move your phone is probably the most obvious to people, that is that if you are moving from one digital technology to another, the phone will not be designed to work on the other carriers technology.
The second reason is actually the most complicated to explain but I will try and list it all for you. This would be the case if you were moving from a CDMA carrier to a CDMA carrier or the same for GSM/UMTS Carriers.
It all comes down to the programming of the phone itself. There are so many parameters that go into the programming of a cellular phone to make it work the way customers are accustomed to. This includes things such as to how to do run applications like SMS, MMS, and WAP. Each one of the applications in the phone requires certain programming to match the carrier’s equipment. This includes things such as DNS server IP addresses, how often the phone scans for a stronger signal, the max size of a picture to be sent via MMS, and things along that line. These are all settings that are installed in the phone in what is called a PRI file.
Many of you may have heard of a PRL file, which is where the phone gets its roaming list from as to who the phone can roam on and who it cannot. But actually the more important file is called a PRI and that is what tells the phone how to operate in general. This has become even more complicated of a file since the introduction of data aps and the internet.
You will see all over the internet in forums about people unlocking or hacking a phone. 90% of the time this is just enough to allow you to change the phone number or the data address of the device, most of the time doesn’t unlock it enough to allow someone to change the entire PRI. Unlocking a phone usually just allows someone to use a tool called QPST or CDMA Toll that can go into the phone and change particular parameters that will allow you to make phone calls or surf but doesn’t actually allow you to change fields used for MMS and WAP and certain other applications.
To truly change the PRI for a particular vendor phone you have to have flashing software and tools. Almost every manufacturer of mobile devices has their own version of the QPST for doing that. To get that software you usually have to be a seller of that manufacturer or a carrier before it is totally shared with you.
As you can imagine a carrier is not going to have this software available at all sales stores you may go into to sign up for service. A company may only have 1 or 2 copies of this software and that is just for testing in there lab the different models of phones and how they operate in different scenarios.
Also not all phones are alike, some of the major carriers will actually put each phone model through extensive testing on their network to make sure it meets certain criteria. There are some models of phones that may drop more calls than others because of the way the antenna is built into the device. They won’t allow these models on their network because it just opens up the opportunity for customers to start calling and complaining about the service, when it’s actually the device they are using not the service. This is very expensive for most carriers to perform so you will find only the major carriers will have test labs..
Even with the emergence of LTE and the fact that all carriers will eventually go to LTE, This technology doesn’t support voice calls as the average consumer thinks of it. Voice calls will actually be made over a data application and in order to perform these functions there are even more detailed requirements that must be put into each phone based on the home carriers system. LTE does solve the problem of different digital technologies on different carriers but the other issues will still prevail.
So as you can see there are some technical reasons why a carrier will not let you bring a phone from one carrier to another carrier. It’s more about the phone itself and the programming of it than it is about the carrier wanting to sell you something new. I agree, it’s very frustrating as a customer to have to purchase a new phone if you are changing carriers. Again, you can hack them and unlock them to allow you to do the basics, but you still can’t expect a carrier to do that for you due to time and effort. Even the IPHONE when it is hacked into the only real data most people can get is via Wi-Fi and not 3G.
Related articles
- What is 4G Wireless Technology (lifetraveler.net)
- What is the best carrier in the US? (techradar.com)
- How Phone will Travel (lifetraveler.net)
