How a Cell Phone Call Works

How A Cell Phone Call Works The Basics Cell phones are radio devices - they communicate by transmitting and receiving voice over an area. First a cell phone radios the nearest cell tower (or site). Next, a wire or fiberoptic line caries the call down to When you make a call or turn your phone on, your the wireless access point, connected to a multi-port phone sends a message via radio that's picked up by the tower's antennas. switch. Wireless Access 1 Point 3 Microwave (Wireless Backhaul) Wireless T1 or 13 (Wired Backhaul) Ассess Point The call (along with many others) gets routed to a The incoming call or data comes back from the back- backhaul – usually down to an underground wired T1 or T3 line, but sometimes back up the mast to a power- it then hits your phone (presuming your phone is still ful line-of-sight wireless microwave antenna (typically communicating with the same site). If you are moving, only used either when there isn't a ground connection, or when the ground connection is poor). haul and up through the switch to the antenna, where then there's a handoff-a new but more or less identi- cal cell site transmits the data to your phone, once your phone checks in. Nikola Tesla 1856-1943 Modern wireless technology owes a great deal to Nikola Tesla's experiments. Tesla researched ways to transmit power and energy wirelessly over long distances, receiving patents on wireless transceivers. His theories on wireless technology are still in use today. How Towers Work When you look at a cell tower, often there are multiple The platforms are triangular so the 360° coverage can triangular platforms going up the pole. These usually be split into 120° pie pieces, which can be subdivided belong to separate carriers. again into 40° slices for pinpointed coverage. Carrier A Carrier B 40° 120° The base station transmits at low power. A big advantage to low-power transmitters is that the transmissions of a base station (and the phones within its cell) do not make it very far outside that cell. This allows non-adjacent cells to reuse the same frequencies. The same frequencies can be reused extensively across a city. Non-adjacent cells sharing frequencies Cellular Frequencies A single cell in an analog cell-phone system uses one-seventh of the available duplex voice channels. That is, each cell (of the seven on a hexagonal grid) is using one-seventh of the available channels so it has a unique set of frequencies and there are no collisions. A cell-phone carrier typically gets 832 radio frequencies to use in a city. Each cell phone uses two frequencies per call (one for transmitting, and one for receiving) so there are typically 395 voice channels per carrier. The other 42 frequencies are used for control channels. Control Channels Voice Transmission Channels Voice Reception Channels Because cells use a fraction of the available frequencies (to avoid collisions), each cell has about 56 voice channels available. In other words, in any cell, 56 people can be talking on their cell phone at one time. Analog cellular systems are considered first-generation mobile technology, or 1G. With digital transmission methods (2G), the number of available channels increases. The most common way of increasing channels with 2G are: Frequency Division Multiple Access (which puts each call on a separate frequency) 45 MHz 824.04 893.7 MHz MHz Receiving Frequency Transmitting Frequency Time Division Multiple Access (which assigns each call a certain portion of time on a designated frequency) 893.7 824.04 MHz MHz 6.7 MS Receiving Frequency Transmitting Frequency Code Division Multiple Access (which gives a unique code to each call and spreads it over available frequencies) 1850 1990 MHz MHz Digital Decoding Digital Encoding 3G uses similar methods, such as CDMA2000 (based on 2G Code Division Multiple Access), WCDMA (UMTS) (Wideband Code Division Multiple Access), and TD-SCDMA (Time-division Synchronous Code-division Multiple Access). 3G networks also have potential transfer speeds of up to 3 Mbps (about 15 seconds to download a 3-minute MP3. For comparison, the fastest 2G phones can achieve up to 144Kbps (about 8 minutes to download a 3-minute song) 8 minutes Time for 3G Download to Complete Time for 2G Download to Complete Unlocked Phones A locked phone will only recognize a SIM card from a particular carrier. The lock is a software setting (one that can often be overridden with a code). If the cell phone is unlocked, it will recognize a SIM card from any carrier. Sources: Bright Hub, Cellphones.org. Gizmodo, HowStuffWorks, Test Freaks Information provided by cellphones.org How A Cell Phone Call Works The Basics Cell phones are radio devices - they communicate by transmitting and receiving voice over an area. First a cell phone radios the nearest cell tower (or site). Next, a wire or fiberoptic line caries the call down to When you make a call or turn your phone on, your the wireless access point, connected to a multi-port phone sends a message via radio that's picked up by the tower's antennas. switch. Wireless Access 1 Point 3 Microwave (Wireless Backhaul) Wireless T1 or 13 (Wired Backhaul) Ассess Point The call (along with many others) gets routed to a The incoming call or data comes back from the back- backhaul – usually down to an underground wired T1 or T3 line, but sometimes back up the mast to a power- it then hits your phone (presuming your phone is still ful line-of-sight wireless microwave antenna (typically communicating with the same site). If you are moving, only used either when there isn't a ground connection, or when the ground connection is poor). haul and up through the switch to the antenna, where then there's a handoff-a new but more or less identi- cal cell site transmits the data to your phone, once your phone checks in. Nikola Tesla 1856-1943 Modern wireless technology owes a great deal to Nikola Tesla's experiments. Tesla researched ways to transmit power and energy wirelessly over long distances, receiving patents on wireless transceivers. His theories on wireless technology are still in use today. How Towers Work When you look at a cell tower, often there are multiple The platforms are triangular so the 360° coverage can triangular platforms going up the pole. These usually be split into 120° pie pieces, which can be subdivided belong to separate carriers. again into 40° slices for pinpointed coverage. Carrier A Carrier B 40° 120° The base station transmits at low power. A big advantage to low-power transmitters is that the transmissions of a base station (and the phones within its cell) do not make it very far outside that cell. This allows non-adjacent cells to reuse the same frequencies. The same frequencies can be reused extensively across a city. Non-adjacent cells sharing frequencies Cellular Frequencies A single cell in an analog cell-phone system uses one-seventh of the available duplex voice channels. That is, each cell (of the seven on a hexagonal grid) is using one-seventh of the available channels so it has a unique set of frequencies and there are no collisions. A cell-phone carrier typically gets 832 radio frequencies to use in a city. Each cell phone uses two frequencies per call (one for transmitting, and one for receiving) so there are typically 395 voice channels per carrier. The other 42 frequencies are used for control channels. Control Channels Voice Transmission Channels Voice Reception Channels Because cells use a fraction of the available frequencies (to avoid collisions), each cell has about 56 voice channels available. In other words, in any cell, 56 people can be talking on their cell phone at one time. Analog cellular systems are considered first-generation mobile technology, or 1G. With digital transmission methods (2G), the number of available channels increases. The most common way of increasing channels with 2G are: Frequency Division Multiple Access (which puts each call on a separate frequency) 45 MHz 824.04 893.7 MHz MHz Receiving Frequency Transmitting Frequency Time Division Multiple Access (which assigns each call a certain portion of time on a designated frequency) 893.7 824.04 MHz MHz 6.7 MS Receiving Frequency Transmitting Frequency Code Division Multiple Access (which gives a unique code to each call and spreads it over available frequencies) 1850 1990 MHz MHz Digital Decoding Digital Encoding 3G uses similar methods, such as CDMA2000 (based on 2G Code Division Multiple Access), WCDMA (UMTS) (Wideband Code Division Multiple Access), and TD-SCDMA (Time-division Synchronous Code-division Multiple Access). 3G networks also have potential transfer speeds of up to 3 Mbps (about 15 seconds to download a 3-minute MP3. For comparison, the fastest 2G phones can achieve up to 144Kbps (about 8 minutes to download a 3-minute song) 8 minutes Time for 3G Download to Complete Time for 2G Download to Complete Unlocked Phones A locked phone will only recognize a SIM card from a particular carrier. The lock is a software setting (one that can often be overridden with a code). If the cell phone is unlocked, it will recognize a SIM card from any carrier. Sources: Bright Hub, Cellphones.org. Gizmodo, HowStuffWorks, Test Freaks Information provided by cellphones.org How A Cell Phone Call Works The Basics Cell phones are radio devices - they communicate by transmitting and receiving voice over an area. First a cell phone radios the nearest cell tower (or site). Next, a wire or fiberoptic line caries the call down to When you make a call or turn your phone on, your the wireless access point, connected to a multi-port phone sends a message via radio that's picked up by the tower's antennas. switch. Wireless Access 1 Point 3 Microwave (Wireless Backhaul) Wireless T1 or 13 (Wired Backhaul) Ассess Point The call (along with many others) gets routed to a The incoming call or data comes back from the back- backhaul – usually down to an underground wired T1 or T3 line, but sometimes back up the mast to a power- it then hits your phone (presuming your phone is still ful line-of-sight wireless microwave antenna (typically communicating with the same site). If you are moving, only used either when there isn't a ground connection, or when the ground connection is poor). haul and up through the switch to the antenna, where then there's a handoff-a new but more or less identi- cal cell site transmits the data to your phone, once your phone checks in. Nikola Tesla 1856-1943 Modern wireless technology owes a great deal to Nikola Tesla's experiments. Tesla researched ways to transmit power and energy wirelessly over long distances, receiving patents on wireless transceivers. His theories on wireless technology are still in use today. How Towers Work When you look at a cell tower, often there are multiple The platforms are triangular so the 360° coverage can triangular platforms going up the pole. These usually be split into 120° pie pieces, which can be subdivided belong to separate carriers. again into 40° slices for pinpointed coverage. Carrier A Carrier B 40° 120° The base station transmits at low power. A big advantage to low-power transmitters is that the transmissions of a base station (and the phones within its cell) do not make it very far outside that cell. This allows non-adjacent cells to reuse the same frequencies. The same frequencies can be reused extensively across a city. Non-adjacent cells sharing frequencies Cellular Frequencies A single cell in an analog cell-phone system uses one-seventh of the available duplex voice channels. That is, each cell (of the seven on a hexagonal grid) is using one-seventh of the available channels so it has a unique set of frequencies and there are no collisions. A cell-phone carrier typically gets 832 radio frequencies to use in a city. Each cell phone uses two frequencies per call (one for transmitting, and one for receiving) so there are typically 395 voice channels per carrier. The other 42 frequencies are used for control channels. Control Channels Voice Transmission Channels Voice Reception Channels Because cells use a fraction of the available frequencies (to avoid collisions), each cell has about 56 voice channels available. In other words, in any cell, 56 people can be talking on their cell phone at one time. Analog cellular systems are considered first-generation mobile technology, or 1G. With digital transmission methods (2G), the number of available channels increases. The most common way of increasing channels with 2G are: Frequency Division Multiple Access (which puts each call on a separate frequency) 45 MHz 824.04 893.7 MHz MHz Receiving Frequency Transmitting Frequency Time Division Multiple Access (which assigns each call a certain portion of time on a designated frequency) 893.7 824.04 MHz MHz 6.7 MS Receiving Frequency Transmitting Frequency Code Division Multiple Access (which gives a unique code to each call and spreads it over available frequencies) 1850 1990 MHz MHz Digital Decoding Digital Encoding 3G uses similar methods, such as CDMA2000 (based on 2G Code Division Multiple Access), WCDMA (UMTS) (Wideband Code Division Multiple Access), and TD-SCDMA (Time-division Synchronous Code-division Multiple Access). 3G networks also have potential transfer speeds of up to 3 Mbps (about 15 seconds to download a 3-minute MP3. For comparison, the fastest 2G phones can achieve up to 144Kbps (about 8 minutes to download a 3-minute song) 8 minutes Time for 3G Download to Complete Time for 2G Download to Complete Unlocked Phones A locked phone will only recognize a SIM card from a particular carrier. The lock is a software setting (one that can often be overridden with a code). If the cell phone is unlocked, it will recognize a SIM card from any carrier. Sources: Bright Hub, Cellphones.org. Gizmodo, HowStuffWorks, Test Freaks Information provided by cellphones.org