What multiplexing schemes are used in GSM and for what purpose?
957609
GSM uses TDMA (time domain multiplex). I believe it can handle 8 conversations per frequency channel.
1091387
Yes, Why Don u jus search the web.\ntry this http://en.wikipedia.org/wiki/GSM
357712
modulation is simply affecting a frequency by altering its waveshape such as with a microphone. Multiplexing is dividing a frequency between 2 or more input signals...I.E. having 2 or more microphones riding on the same frequency but totally independant of each other. Phone lines are multiplexed to contain more than one phone conversation.
373020
They are both ways of putting information on a bigger pipe.\n\nFor modulation, you modulate a carrier frequency with a signal.\n\nMultiplexing involves taking multiple signals and placing them on the same baseband to carry them.\n\nThat isn't much of a similarity, though.  I guess the other one would be that you can have either digital or analog modulation and you can have either digital or analog (FDM) multiplexing.
297960
TDM, or time division multiplexing is a scheme to encode several analog signals through one communications channel.\n\nLet's say that you have three telephone conversations.  An encoder, known as a multiplexer, will combine the three by switching very rapidly through all three conversations.  This is called multiplexing.  \n\nLet's say that the multiplexing speed is 66kHz, which translates roughly to 15 microseconds to complete one multiplex cycle (one divided by 66kHz).  The first 5 microseconds, conversation 1 is switched onto the line, the second 5us, conversation 2 is switched onto the line, and the third 5us conversation 3 is switched onto the line.  The cycle then repeats itself over and over.\n\nIf you listened to the communications line, it would sound like you were listening to three conversations simultaneously, like they were blended together.\n\nNow, on the other end of the communications line, a decoder, called a demultiplexer sorts out the three conversations with a precise clock and a time base signal that is added in at the multiplexing process.  So it sorts out the three conversations and seperates them into the three original channels by doing the switching in the exact opposite of the multplexer by again making the switch every 5us.   \n\nVoila, time switching combines three phone conversations over one set of wires.\n\nIn cellular phones, there is a scheme known as TDMA, or time division, multiple access.  This is similar concept, but it coordinates multiple cell phone's transmitters to accomplish the same thing, but over radio instead of wires.
1160895
Any mobile operator that can support pcmcia GSM cards with UMTS or EDGE services. They are meant for laptops, high DSL speed and high band usage so the cost turns out cheaper for you.
225191
GSM-900 and GSM-1800\nGSM-900 and GSM-1800 are used in most of the world.\n\nGSM-900 uses 890 - 915 MHz to send information from the Mobile Station to the Base Transceiver Station (upstream) and 935 - 960 MHz for the other direction (downstream), providing 124 RF channels spaced at 200 kHz. Duplex spacing of 45 MHz is used. \nIn some countries the GSM-900 band has been extended to cover a larger frequency range. This 'extended GSM', E-GSM, uses frequency range 880 - 915 MHz (upstream) and 925 - 960 MHz (downlink), adding 50 traffic channels to the original GSM-900 band. The GSM specifications also describe 'railways GSM', R-GSM, which uses frequency range 876 - 915 MHz (uplink) and 921 - 960 MHz (downstream). R-GSM provides additional channels and specialized services for use by railway personnel.\n\nAll these variants are included in the GSM-900 specification.\n\nGSM-1800 uses 1710 - 1785 MHz to send information from the Mobile Station to the Base Transceiver Station (upstream) and 1805 - 1880 MHz for the other direction (downstream), providing 374 channels. Duplex spacing is 95 MHz. \nGSM-1800 is also called PCS in Hong Kong and the United Kingdom. Most of the GSM operators in India use the 900 Mhz band.\n\n\nGSM-850 and GSM-1900\nGSM-850 and GSM-1900 are used in the United States, Canada, and many other countries in the Americas. GSM-850 is also sometimes called GSM-800.\n\nGSM-850 uses 824 - 849 MHz to send information from the Mobile Station to the Base Transceiver Station (upstream) and 869 - 894 MHz for the other direction (downstream). \nGSM-1900 uses 1850 - 1910 MHz to send information from the Mobile Station to the Base Transceiver Station (upstream) and 1930 - 1990 MHz for the other direction (downstream). \nPCS is an acronym for Personal Communications Service, and merely represents the original name in North America for the 1900 MHz band. Cellular is the term used to describe the 850 MHz band, as the original analog cellular mobile communication system was allocated in this spectrum. Providers commonly operate in one or both frequency ranges.
594114
because regular phone lines cant handle 56k of data, they were only designed to handle voice. encoding it allows for higher data rates. for instance 16 level PAM encoding allows you to send a 56k data stream at the same rate as a 14k uncoded data stream (basically).
914718
3GP Converter.http://www.nurs.or.jp/~calcium/3gpp/. very good converter. English version is also available.
352935
I don't believe there is modulation within CDMA.  You are confusing yourself.\n\nCode division multiple access (CDMA) is a form of multiplexing (not a modulation scheme) and a method of multiple access that does not divide up the channel by time (as in TDMA), or frequency (as in FDMA), but instead encodes data with a special code associated with each channel and uses the constructive interference properties of the special codes to perform the multiplexing. CDMA also refers to digital cellular telephony systems that make use of this multiple access scheme, such as those pioneered by Qualcomm, or W-CDMA.
718103
First, about cellular generations. Having worked in the industry for a while, I have a narrower view what 1G, 2G, 3G, 4G, etc. mean. First 1G service was based on a TDM voice infrastructure -- built around class x switches and 64 kbps slots. It had data, but circuit switched over a 64Kpbs voice bearer.\n\nSecond, 2G service had the same switched TDM backbone, but added a true Data Bearer and a digital voice bearer. Data rates were still limited to the max 64kbps of a single time slot.\n\n2.5G added a packet bearer to the mix, still limited to 64kbps slots.\n\nThird generation (3G) changed the backbone slightly to allow a full T1 or E1 or J1 to be consumed by a data sub-scriber, but is still based on an ISDN style backbone. Sure you have packet switched data, but its carried over a traditional TDM backbone. There still a circuit voice backbone and while the data rates are high enough for VoIP, the latency of the data service is to great to base all of the "bearer services" on it, so you still have circuit voice, circuit data and packet data bearers.\n\nFinally, 4G systems will utilize a packet infrastructure rather than a traditional telephone architecture. Services will be horizontally layered on top of a proper low latency, QoS enabled packet switch (read IP) infrastructure. Gone will be the circuit voice and circuit data bearers.\n\nSo "G" has more to do with the infra-structure and less to do with the data rates. The data rates over the air are driven by the organization of the infrastructure and other than that have little to do with what generation they are.\n\nIn that sense, this NexTel trial is a 4G trial. BTW, I'm a participant in that trial. If folks are interested, I'll post some results that I might be able to share.\n- by NetGuy
677272
Xilisoft 3gp Converter is what u want.\n http://www.xilisoft.com\n\ni used it and i can definately say that it is a very good soft.
661515
yes it's possible. all you need is a Wireless GPRS/GSM Modem PC Card. best way you ask your mobile phone provider.\n\nhttp://www.newegg.com/Product/Product.asp?Item=N82E16875210101\nthere are also combined GPRS/Wifi cards available. Wifi means the 2.4GHz wireless IEEE 802.11b/g standard.
203395
cellular communications GSM and CDMA use different frequencies to operate\n\nGSM - 800 MHz, 850 Mhz, 900 Mhz, 1800 Mhz, 1900 MHz\nCDMA - dont recall but in the same set of freq's as GSM\n\nboth use a modified from of SS7 (Signaling System 7) to control the communications. and both are primarly for voice traffic\n\nThe range of a single cell site could be as high as tens of miles\n\nAll over the world you would need a license to set up a cellular tower\n\nWLAN on the other hand operates in the ISM Band\n\n802.11 b/g/n 2.4GHz\n802.11 a - 5.2 GHz\n\nthe WLAN is primarly used to transfer data, and the range of  typical WLAN installations with a single AP would be tens of feet. (although with the proper equipment one can do miles in point to point mode) The ISM band is also know as an amature band and almost all over the world you would not require any permission to set up equipment.\n\nHope this helps
62814
Mobiles are wireless and hence the protocol used for connection between server and ur cell phone is WAP(Wireless application protocol). Besides these ur cell phone must have GPRS technology for internet access. U cant download or transfer data on ur cell phone as u do on ur home pc in megabytes.
826878
All radio transmissions can be considered analog even the digital ones like FSK, PSk,QAM, since the carrier is sinsoidal which is analog, however the data are digital so they change the carrier characteristic in discrete way. in mobile systems such as GSM the type of modulation is GMSK (gausian minimum shift keying), which is a special type of FSK (frequency shift keying), in FSK the frequency of the carrier is alternating between two values, each frequency represents a logic state (digital), which can be processed by the mobile circuitry. again the FSK is an FM signal whith the message being digital (binary)
170016
You can use Xilisoft to conver RM File format to 3gp.\n\nIt has abelity to convert any media format to 3gp\n\nyou can download trial verson of the application from the below site