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When you turn your phone on, it listens for special frequencies (control channel) that the phone and tower (base station) use to talk to one another. Once the phone locates your nearest base station, that station sends a registration request, so the MTSO can keep track of which cell your phone is in. The MTSO stores all of this info in a database so it can locate your phone when it needs to ring it. When the phone can’t find the control channels it will display a “no service” message, because it knows it is out of range.
When you make a call your phone uses the control channels to tell the base station you want to dial out.
Once the base station gets the message that you want to make a call it uses the normal telephone line to send the message to the MTSO so it can find the recipients location in its database.
Once the MTSO has located the cell that the recipient is located in it transfers a message to that cells base station using regular telephone lines. This message tells the base station what frequencies to use for the voice call. The MTSO also tells the recipients phone to use those same frequencies. If you are calling a land line the MTSO acts as the switch station sending your call to the recipient using the regular phone lines.
After the base station receives the message from the MTSO it uses a unique set of frequencies to connect to your phone. This is called a voice channel and consists of two frequencies, one for listening and one for talking.
Once the base station and your phone switch to the designated unique frequencies then the call is connected and you are in a sense talking to your friend on a two-way radio.
Base Station – The base station communicates with your wireless device, where that signal is then sent to whoever you are calling. These sites are often called “cell towers”, however they are not always located on a tower, and sometimes are found on the roof of some buildings. There are also temporary set-ups called cells-on-wheels which provided signal in places without any by mounting a cell site to the top of a vehicle.
MTSO (Mobile Telephone Switching Office) – Is where phone calls are transferred to the appropriate mobile or landline. Each MTSO contains an MSC (Mobile Switching Center) which handles the transferring of the signal. It also has a database it uses to store the location of phones in its network.
Land Line – A phone that is hardwired to a phone jack. Can also be a direct line connecting to specific places, such as the airport to emergency services, so that connection is never lost. The signal is transmitted via metal wire or optical cable instead of radio waves.
SID – The SID or System Identification Code is a 15-bit number that is assigned to each of the carriers by the FCC to help the signal towers identify the device prior to accepting the signal.
Radio Frequency – All cellular phone networks worldwide use a portion of the radio frequency spectrum designated as ultra-high frequency, or “UHF”, for the transmission and reception of their signals. The ultra-high frequency band is also shared with television, Wi-Fi and Bluetooth transmission. The cellular frequencies are the sets of frequency ranges within the ultra-high frequency band that have been allocated for cellular phone use.
Land Based Telephone Line(wire) – The cellular base stations use a normal land based telephone system to route the calls from the cell site to the MTSO or Land line.
Registration Request – Along with the SID your phone sends a registration request to the MTSO. The registration request tells the switch office to store the phones location in its database so it can keep track of the phone as it moves from cell to cell.
Voice Frequency – The frequency used to transmit speech. The Voice Frequency band ranges from 300Hz to 3400Hz, with the average human male transmitting at 85-180Hz and female at 165-255Hz. This is made possible thanks to the harmonic series being present to create the impression of hearing the fundamental tone.
Cells – Each cell phone carrier is given a certain number of frequencies to use for its’ customers. There for to provide the best coverage, they split the city into about 7 cells with one “base station” at the center of each cell. The size of each cell averages between 5-10 square miles.
Hand Off – As you move toward the edge of your cell, your cell’s base station notes that your signal strength is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) sees your phone’s signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point. This hand off switches your phone to the new cell.
There are many factors that can cause your phone to loose signal, drop a call, or not even connect with the base station. Most have to do with what stands between your phone and the tower.
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Materials that weaken signal
The more obstacles that stand between you and the base station the more potential there is for a weakened or lost signal to the tower. If you are in a building, these obstacles include the materials used to build the structure. Even if you are outside the natural surroundings like trees, mountains, and even the weather can affect your signal strength.
Metal is often used in siding and other building materials. It is highly conductive and can weaken your cellular signal by absorbing or reflecting it.
Concrete and cinder block are some more building materials that absorb cellular frequencies weakening your signal. You may find when you go into certain buildings or stores you automatically lose signal. This is most likely do to the amount of concrete used to build the structure.
Sheet rock can also weaken your cell phone signal. However, it is not a highly conductive material, nor is it very thick, so it does not have as big of an impact as metal or concrete.
Do you find yourself loosing reception when you are in a crowded lecture hall? This is because people can also absorb or reflect cellular frequencies. Humans are 50%-65% water which is highly conductive.
The weather can also be a factor in cell signal. Fog and clouds can be a barrier for the radio frequencies. Not to mention if it’s raining the water is highly conductive and can absorb frequencies.
Plants, mountains and hills also affect cell signals. Plants contain water and dissolved ions, which conduct electricity. Mountains and hills often act as obstructing materials, breaking the contact between your cell phone and a cell tower, which results in a weaker signal.
Many cities don’t like the addition of cell sites so in an attempt to compromise some of the base stations are hidden by trees (real or fake) and other astatically pleasing elements. However, sometimes these things can also act as a barrier for the cellular frequencies to get past.
Materials that block signal
There are also materials and situations that can completely block signal to and from your cell phone.
Faraday Cage – The same concept as the aluminum foil, just on a much larger scale! Basically they lined the Pentagon in aluminum foil to keep out nosy eavesdroppers. In reality, it’s the faraday cage effect, used to block exterior signals from coming in, and from interior signals from going out, unless permitted.
Aluminum Foil – Contrary to popular belief, wrapping your phone in aluminum foil will not boost phone signal, instead it will work as a suppressor, smothering your phone signal, and hence why we all put on our aluminum foil hats when somebody brings up the NSA these days.
Salt Water – One reason you won’t get any signal underwater is because you’re under freaking water! Being in the salt water is going to kill your phone in five minutes flat anyways, but if you’re still curious as to why, it’s a mixture of the ions in salt and the conductivity of water that causes a complete loss of signal.
Tips to Boost your signal
Believe it or not holding your phone up high does help with the signal, even though only by a little bit. In some cases you might not notice a difference, but sometimes it does help because you are getting it closer to the height of the radio waves coming from the base station. So don’t be shy, stand on your chair and hold your phone high.
If you are in a highly reinforced structure, or if you are in an area with a large crowd of people, you may have to step outside, away from these obstacles, to get a better signal. Sometimes even going to an outside room or near a window will help.
If those options don’t work you might try a cellular repeater. A cellular repeater, or wireless cellular signal booster, a type of bi-directional amplifier (BDA), is a device used for boosting the cell phone reception to your local area by using a reception antenna, a signal amplifier and an internal rebroadcast antenna.
We here at RepairLabs have spent a considerable amount of time collecting the data and information to bring you this infographic, and just hope that you have enjoyed reading/viewing it as much as we have creating it for you.
Please feel free to share this amazingly informative infographic with your friends, co-workers, or pretty much anybody who has ever asked you why their phone dropped signal on them, that’s what it’s here for!
From your friends at RepairLabs, the most awesome device repair center in the nation, we bid you farewell, and hope your phone always has signal!
How it works
Brian, Marshall, Jeff Tyson and Jullia Layton. “How Cell Phones Work” 14 November 2000. HowStuffWorks.com
http://electronics.howstuffworks.com/cell-phone.htm 31 July 2013.
What blocks signal