Bring phone device - byod verizon wireless, Bring your own phone or device, get a free sim card and get activated on the verizon wireless network in a few simple steps.. Sell samsung galaxy cell phone cash - buybackworld, Sell your samsung galaxy cell phone for cash if you just upgraded to a new phone or just want earn extra cash, you can sell your new or used samsung cell phone with. How find lost cell phone pcmag., Misplacing a cell phone can be traumatic, even if you aren't a drunken apple engineer with a prototype iphone at a german beer garden. These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace. If you are thinking about buying a cell phone, be sure to check out How Buying a Cell Phone Works to learn about everything you should know before making a purchase. One of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless.
Most newer digital cellular phones have some sort of entertainment programs on them, ranging from simple dice-throwing games to memory and logic puzzles. Cellular phones are more popular in European countries than they are in the United States -- more than 60 percent of Europeans own a cell phone, compared to about 40 percent of Americans. In the dark ages before cell phones, people who really needed mobile-communications ability installed radio telephones in their cars.
Because cell phones and base stations use low-power transmitters, the same frequencies can be reused in non-adjacent cells. Each cell has a base station that consists of a tower and a small building containing the radio equipment (more on base stations later).
Each cell phone uses two frequencies per call -- a duplex channel -- so there are typically 395 voice channels per carrier. The transmissions of a base station and the phones within its cell do not make it very far outside that cell.
The power consumption of the cell phone, which is normally battery-operated, is relatively low. In the next section, you'll find out what happens as you (and your cell phone) move from cell to cell.
While the ESN is considered a permanent part of the phone, both the MIN and SID codes are programmed into the phone when you purchase a service plan and have the phone activated. When you first power up the phone, it listens for an SID (see sidebar) on the control channel.
Along with the SID, the phone also transmits a registration request, and the MTSO keeps track of your phone's location in a database -- this way, the MTSO knows which cell you are in when it wants to ring your phone. The MTSO communicates with your phone over the control channel to tell it which frequencies to use, and once your phone and the tower switch on those frequencies, the call is connected.
As you move toward the edge of your cell, your cell's base station notes that your signal strength is diminishing.
If the SID on the control channel does not match the SID programmed into your phone, then the phone knows it is roaming. A good way to understand the sophistication of a cell phone is to compare it to a CB radio or a walkie-talkie. In duplex radio, the two transmitters use different frequencies, so both parties can talk at the same time.
On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people play with on a daily basis.
The microprocessor handles all of the housekeeping chores for the keyboard and display, deals with command and control signaling with the base station and also coordinates the rest of the functions on the board. The display has grown considerably in size as the number of features in cell phones have increased. Some phones store certain information, such as the SID and MIN codes, in internal Flash memory, while others use external cards that are similar to SmartMedia cards. Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. What is amazing is that all of that functionality -- which only 30 years ago would have filled an entire floor of an office building -- now fits into a package that sits comfortably in the palm of your hand! In 1983, the analog cell-phone standard called AMPS (Advanced Mobile Phone System) was approved by the FCC and first used in Chicago.
The transmit and receive frequencies of each voice channel are separated by 45 MHz to keep them from interfering with each other.
A version of AMPS known as Narrowband Advanced Mobile Phone Service (NAMPS) incorporates some digital technology to allow the system to carry about three times as many calls as the original version.
Digital cell phones use the same radio technology as analog phones, but they use it in a different way. Digital phones convert your voice into binary information (1s and 0s) and then compress it (see How Analog-Digital Recording Works for details on the conversion process). Many digital cellular systems rely on frequency-shift keying (FSK) to send data back and forth over AMPS.
Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one. FDMA separates the spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth.
TDMA is the access method used by the Electronics Industry Alliance and the Telecommunications Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136).
TDMA is also used as the access technology for Global System for Mobile communications (GSM). The GSM standard for digital cell phones was established in Europe in the mid-1980s -- long before digital cellular phones became commonplace in American culture. It is now possible to locate a person using a cellular phone down to a range of a few meters, anywhere on the globe.
3G (third-generation wireless) phones may look more like PDAs, with features such as video-conferencing, advanced personal calendar functions and multi-player gaming. Unfortunately, the 1900-MHz GSM phones used in the United States are not compatible with the international system. Personal Communications Services (PCS) is a wireless phone service very similar to cellular phone service, but with an emphasis on personal service and extended mobility.
While cellular was originally created for use in cars, PCS was designed from the ground up for greater user mobility.


Technically, cellular systems in the United States operate in the 824-MHz to 894-MHz frequency bands; PCS operates in the 1850-MHz to 1990-MHz bands. If you travel a lot, you will probably want to look for phones that offer dual band, dual mode or both. Generally, non-repairable internal corrosion of parts results if you get the phone wet or use wet hands to push the buttons. Here is how cloning occurs: When your phone makes a call, it transmits the ESN and MIN to the network at the beginning of the call.
A cell-phone tower is typically a steel pole or lattice structure that rises hundreds of feet into the air. This is a modern tower with three different cell-phone providers riding on the same structure. The box houses the radio transmitters and receivers that let the tower communicate with the phones.
If you look closely, you will see that the tower and all of the cables and equipment at the base of the tower are heavily grounded. One sure sign that multiple providers share this tower is the amazing five-way latch on the gate.
Cell-phone towers come in all shapes and sizes, but I do believe this one in Morrisville, NC, is one of the weirdest looking! Check out the links on the next page and How Buying a Cell Phone Works for lots more information and consumer tips! 7 ways find imei meid number mobile phone, How to find the imei or meid number on a mobile phone. Samsung galaxy s4 mini ebay, Find great deals on ebay for samsung galaxy s4 mini samsung galaxy s4 mini case.
Samsung galaxy s5 unlock code - unlocking company, Samsung galaxy s5 unlock code (all countries) unlock your cell phone for any carrier in the world! How find imei esn number cell phone, 7 responses “ find imei esn number cell phone”. Samsung galaxy s6 s6 edge settings support verizon, Learn common settings samsung galaxy s6 s6 edge. They are such great gadgets -- with a cell phone, you can talk to anyone on the planet from just about anywhere! The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi). In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously. Therefore, in the figure above, both of the purple cells can reuse the same 56 frequencies.
Low power means small batteries, and this is what has made handheld cellular phones possible. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel changing. If the SIDs match, the phone knows that the cell it is communicating with is part of its home system. 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 MTSO of the cell that you are roaming in contacts the MTSO of your home system, which then checks its database to confirm that the SID of the phone you are using is valid. A CB radio, because it has much higher power, can transmit about 5 miles (8 km) using a 5-watt transmitter. Modern digital cell phones can process millions of calculations per second in order to compress and decompress the voice stream. The ROM and Flash memory chips provide storage for the phone's operating system and customizable features, such as the phone directory.
As you can see in the picture above, the speaker is about the size of a dime and the microphone is no larger than the watch battery beside it. AMPS uses a range of frequencies between 824 megahertz (MHz) and 894 MHz for analog cell phones.
A pair of frequencies (one for transmit and one for receive) is used to create one channel. Each carrier has 395 voice channels, as well as 21 data channels to use for housekeeping activities like registration and paging.
Analog systems do not fully utilize the signal between the phone and the cellular network -- analog signals cannot be compressed and manipulated as easily as a true digital signal. This compression allows between three and 10 digital cell-phone calls to occupy the space of a single analog call.
FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone. To better understand FDMA, think of radio stations: Each station sends its signal at a different frequency within the available band.
Using TDMA, a narrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots. In covered areas, cell-phone users can buy one phone that will work anywhere where the standard is supported. In practice, high-power CDMA signals raise the noise floor for TDMA receivers, and high-power TDMA signals can cause overloading and jamming of CDMA receivers.
The term "PCS" is often used in place of "digital cellular," but true PCS means that other services like paging, caller ID and e-mail are bundled into the service. PCS has smaller cells and therefore requires a larger number of antennas to cover a geographic area.
And while it is based on TDMA, PCS has 200-kHz channel spacing and eight time slots instead of the typical 30-kHz channel spacing and three time slots found in digital cellular. Usually the phone will have a default option set, such as 1900-MHz TDMA, and will try to connect at that frequency with that technology first.
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What do all those confusing terms like PCS, GSM, CDMA and TDMA mean?Now, we will discuss the technology behind cell phones so that you can see how amazing they really are. This central antenna meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles (about 70 km).
In a typical analog cell-phone system in the United States, the cell-phone carrier receives about 800 frequencies to use across the city. For example, a TDMA-based digital system can carry three times as many calls as an analog system, so each cell has about 168 channels available (see this page for lots more information on TDMA, CDMA, GSM and other digital cell-phone techniques). If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. Your home system verifies your phone to the local MTSO, which then tracks your phone as you move through its cells.
That is, two people communicating on a CB radio use the same frequency, so only one person can talk at a time.
The analog-to-digital and digital-to-analog conversion chips translate the outgoing audio signal from analog to digital and the incoming signal from digital back to analog. The radio frequency (RF) and power section handles power management and recharging, and also deals with the hundreds of FM channels. The frequencies used in analog voice channels are typically 30 kHz wide -- 30 kHz was chosen as the standard size because it gives you voice quality comparable to a wired telephone. AMPS and NAMPS only operate in the 800-MHz band and do not offer many of the features common in digital cellular service, such as e-mail and Web browsing.
This is the reason why many cable companies are switching to digital -- so they can fit more channels within a given bandwidth. Clever modulation and encoding schemes are required to convert the analog information to digital, compress it and convert it back again while maintaining an acceptable level of voice quality. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space.
Think of GSM and IS-136 as two different operating systems that work on the same processor, like Windows and Linux both working on an Intel Pentium III.
To connect to the specific service providers in these different countries, GSM users simply switch subscriber identification module (SIM) cards. Multiple calls are overlaid on each other on the channel, with each assigned a unique sequence code.
For example, a dual-band TDMA phone could use TDMA services in either an 800-MHz or a 1900-MHz system. It's important that one of the modes is AMPS -- this gives you analog service if you are in an area that doesn't have digital support. It may mean that the phone supports two digital technologies, such as CDMA and TDMA, as well as analog. If the phone does get wet, be sure it is totally dry before you switch it on so you can try to avoid damaging internal parts. In case of trademark issues please contact the domain owner directly (contact information can be found in whois). It also meant that not many people could use radio telephones -- there just were not enough channels. Each carrier in each city also runs one central office called the Mobile Telephone Switching Office (MTSO). You can learn more about A-to-D and D-to-A conversion and its importance to digital audio in How Compact Discs Work.
While it is certainly capable of carrying digital information, FDMA is not considered to be an efficient method for digital transmission. Therefore, TDMA has three times the capacity of an analog system using the same number of channels. CDMA is a form of spread spectrum, which simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range. Because CDMA systems need to put an accurate time-stamp on each piece of a signal, it references the GPS system for this information. And if the phone supports more than one mode, it will try the digital mode(s) first, then switch to analog. But it can also mean that it supports one digital technology in two bands and also offers analog support.
This office handles all of the phone connections to the normal land-based phone system, and controls all of the base stations in the region. That means that you use one frequency for talking and a second, separate frequency for listening.
Someone using a cell phone can drive hundreds of miles and maintain a conversation the entire time because of the cellular approach.
The digital signal processor (DSP) is a highly customized processor designed to perform signal-manipulation calculations at high speed. GSM operates in the 900-MHz and 1800-MHz bands in Europe and Asia, and in the 1900-MHz (sometimes referred to as 1.9-GHz) band in the United States. They store all the connection data and identification numbers you need to access a particular wireless service provider. Between eight and 10 separate calls can be carried in the same channel space as one analog AMPS call. A popular version of the tri-mode type of phone for people who do a lot of international traveling has GSM service in the 900-MHz band for Europe and Asia and the 1900-MHz band for the United States, in addition to the analog service.
One of the carriers was normally the local-exchange carrier (LEC), a fancy way of saying the local phone company.
CDMA technology is the basis for Interim Standard 95 (IS-95) and operates in both the 800-MHz and 1900-MHz frequency bands. GSM is also the basis for Integrated Digital Enhanced Network (IDEN), a popular system introduced by Motorola and used by Nextel.




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