Mobile Phones... How Do They Work ? why dont they interfere with each other

[qwijibow 0]

Ive recentl become interesting in hobby radio gear.many modern communications decixes use multiple channels on one frequency band.for exampl, pmr446 uses FM 446Mhz but from this frequency their are 8 channels, each channel is seperated by 12Khz to make sure they dont interfere with each other.with 8 channels, and 3 miles range, having too many people all trying to use the same channel and all talking at once is a common problem.how do mobile phones get around this problem !?Mobile phones to the best of my knoledge use microwaves at approxamatly 2.5Ghz.but the mobile band range must be insanely wide to accamidate all the billions of mobiles phone around the world.do all mobiles hpones transmit on a diffferent frequency ???this seems unlikely, as it would mean phone companys would have to continually scan the band looking for new phones which have been powered on for the first time.it just doesnt seem to make sence... remember, im a radio newbie.so how does it all work ???manybe some super huge form of tone squelch ???

[Muddyboy 0]

I think, this is me thinking here.Each radio tower can use the same set of bands as long as they are far enough apart. So when you mobile phone connects to the tower it used one band, but on the other side of the earth another tower can use the same band as the first tower as they wont interfere.Thats why you cannot connect to towers when everyone is on the phones because there is no bands free

[thermoid 0]

Band is a frequency set. Each phone locks a different frequency after assignment from the tower. So limeited freq's limited options. Thank goodness digital phones are coming. They use the same tecnology as WLAN...And no thaey DO NOT use 2.4 GHz... with the power neede to reach towers we'd all be microwaving our brains. a triband uses 950, 1400, and 1800 MHz.

[Muddyboy 0]

Sweet, so i was close

Thank goodness digital phones are coming

O_o i thought the current mobile phones were digital. I know they used to be anolog, and then they changed. I might be wrong

[spinefan03 0]

Cell phones run off two types of networks CDMA (cingular) and PCS (sprint)CDMA or Code Division Multiple Access is basically the same as you explained, but after digitizing the signal, it spreads the signal over the entire frequency range in small chunks that are encoded and set up at different times. Each signal chunk also has a timestamp and therefore also implements the GPS system. Therefore many people can be using the same bandwidth at the same time.. CDMA runs at 800Mhz and 1900Mhz frequency bands.PCS or Personal Communications Services is almost like cellular but in a completly digital form, but an included feature is that paging, caller id, internet service, and other digital services are bundled in the same signal. PCS phones use a smaller area of coverage per cell tower and run between 1.85 and 1.99 GHz (1850 MHz to 1990 MHz)In my own oppinion, CDMA blows PCS away and that is why I have a Cingular cell service (Even though I just happen to be a phone tech for Sprint, the leading PCS provider)

[kap43 0]

Yeah, u are right about the PCS. I work for Nextel and I learned that Nextel phones use a system called IDEN, (which is most likely for the Direct Connect a.k.a walkie-talkie). Since PCS towers are limited in range, Sprint puts up about three towers for every 1 Nextel Iden Tower.Unfortunately, besides the DC, Sprint and Cingular have way better coverage out in the Western U.S. region than Nextel. How ironic that like u, I have a Sprint phone although I work for Nextel- LOL!

[Mahanon 0]

I thought that cell phones used different frequencies to keep them from interfearing from one another, I could be wrong. I use a Cingular phone and I get so much interferance from other phones it is rediculous I can't stand it GAHHH...

[OneStopReefShop 0]

Mahanon,I would think your interference is from a poorly constructed phone, or a phone that has some internal problems. If I was receiving that type of interference I would be into my Cell Phone's office immediately demanding some fix to this problem! It may be as easy as them transferring your current number over to a new phone that doesn't have this problem. I would however push the point that this is a problem caused by "THEIR PHONE" that I received, and as such a problem THEY need to take care of for me... FREE!!!Good luck!!!

[bigredrosen 0]

put simply and as short as possible:in terms of mobile (cell) phones, think of them like fingerprints...you wouldn't think there are so many different patterns for the same thing, but each one is pretty much different.

[andrwxsCOL 0]

The great idea of the cellular system is the division of the city in small cells or cells. This idea allows the reusability of frequencies through the city, with which thousands of people can use the telephones at the same time. In a typical system of analogous telephony of the United States, the company receives around 800 frequencies to use in each city. The company divides the city in cells. Each cell has a size of 26 kilometers square generally. The cells normally are designed like hexagonal (figures of six sides), in a great hexagonal grid.In order to see the graph it selects the option to ¨dowload work¨ of the superior menuEach cell has a station base that consists of a tower and a small building that the radio equipment contains .Each cell in an analogous system uses seventh of the voice channels available. That is, a cell, plus the six cells that surround it in a hexagonal adjustment, each one using seventh of the channels available so that each cell has a unique group of frequencies and there are no collisions:A cellular supplier on watch typically receives 832 radio frequency to use in a city. Each cellular telephone uses two frequencies by call, reason why typically there are 395 voice channels by signal carrier (the 42 remaining frequencies are used like control channels ). Therefore, each cell has around 56 voice channels available. In other words, in any cell, 56 people on their cellular telephones can speak at the same time. With the digital transmission, the number of channels available increases. For example digital system TDMA can carry the triple of calls in each cell, around 168 channels available simultaneously.The cellular telephones have inside transmitting of low power. Many cellular telephones have two intensities of signal: 0.6 watts and 3,0 watts (in comparison, most of the radii of 4 civil band they transmit to watts.) The central station also transmits to low power. The transmitters of low power have two advantages:The transmissions of the main base and the telephones in the same cell do not leave this one. Therefore, each cell can reuse same the 56 frequencies through the city. The consumption of energy of the cellular telephone, that works generally with batteries, is relatively low. A low energy means smaller batteries, which makes the cellular telephones possible. The cellular technology requires a great number of bases or stations in a city of any size. A big city can get to have hundreds of towers. Each city needs to have a central office which handles all the telephone connections to conventional telephones, and controls all the stations of the region.The cellular ones are electronicses with intricados designs, with parts in charge to process million calculations per second to compress and to decompress the voice flow.At the present time three technologies used exist commonly to transmit information in the networks: Multiple access by frequency division (FDMA, by its abbreviations in English) Multiple access by time division (TDMA, by its abbreviations in English) Multiple access by code division (CDMA, by its abbreviations in English) Although these technologies sound complicated, you you can have an idea of how they work examining each word of the names.The fundamental difference lies in the access method , which varies between:Frequency, used in technology FDMA Time, used in technology TDMA Unique codes, that are provided to each call in technology CDMA. The first part of the names of the three technologies (multiple Access), means that more of a user (multiple) it can use (to accesar) each cell.Next we will detail, without entering complicated technical details, how one of the three common technologies works each.Technology FDMA separates the phantom in different voice channels, when separating the bandwidth in pieces (frequencies) uniform. Technology FDMA mainly is used for the analogical transmission. This technology is not recommended for digital transmissions, even though is able to take digital information.Technology TDMA compresses the conversations (digital), and it only sends each one using the signal of radio by a third of time. The compression of the voice signal is possible because the digital information can be reduced of size to be binary information (and zeros). Due to this compression, technology TDMA has three times the capacity of an analogical system that uses the same number of channels.Technology CDMA is very different from technology TDMA. The CDMA, after digitizing the information, transmits it through all the bandwidth available. Several calls are superposed in the channel, and each one has a unique code of sequence. Using to technology CDMA, it is possible to compress between 8 and 10 digital calls so that these occupy the same space that would occupy a call in the analogical system.In theory, technologies TDMA and CDMA must to each other of being transparent (they do not have to be interfered with or to degrade the quality), nevertheless actually appear some smaller problems, like differences in the volume and quality, between both technologies.And, don't worry about how work a celular, is a little diffucult to understant, when I was doing this work to my college, I get confused, but it is nice when you understant.

[ASR1405241491 0]

Well... sometimes for some ackward reason they do interfere with eachother... I guess depending on the service you have... sometimes if you have a bad service it will do that... I sometimes hear other people's conversation on my old phone before... its just really fant and you could barely tell... but still... it does interfere if you have services like metro or the old cingular i think....I have nextel right now.. and sometimes when im too close to the satellite landline phones... it also take over the audio waves and transfer into the landline phones sometimes....Chin chin....