why only 900 MHz  , 1800 MHZ  and 1900 MHZ band are used in GSM?
147646
GSM frequency bands are liscensed and dedicated to GSM mobile services.  With that standardization, it is possible to roam world wide with a quad band phone and have services as long as there is a signal.  GSM is itself a global standard.\n\nNo standard frequencies would mean the inability to produce devices that are "world phones".
810317
The capacity of 802.11(a,b, or g) systems is limited by two main factors; 1) The capacity of the DHCP Server and router and 2) the available bandwidth of the radio interface.\n\nThe typical residential wireless router has a built-in DHCP server to automatically assign wireless (and wired) users an IP address.  Residential DHCP servers usually max out at 256 users.  Enterprise wireless networks use dedicated DHCP servers capable of handling 1000s of users.\n\nThe next limitation is the radio link.  As you know, 802.11g supports link rates up to 54 Mbs.  54 Mbs is achievable only under the best conditions, meaning no other access points or users on the same channel in the area to generate noise.  \n\nAs users are added, the maximum rate available to each user is lowered accordingly, until the number of users are generating more noise than usable signal and effectively jam the access point.\n\nAnother factor in radio capacity is called Near-Far affect.  This occurs when one user has acquired service at a great distance with no interference.  Then a second user, located much nearer to the access point, acquires service and the Near users strong signal over powers the Far users weak signal, effectively jamming the Far users and reducing the access point capacity.
946424
Because 10Mbps is maximum rate per subscriber advertised by your service provider. Its not guaranteed bit rate! Try UMTS HSDPA service from cingular if your are from US.
371821
its the number is ghz your wireless phone has....its interrupts the connection and slows or disconnects it. To fix this problem get a lower or higher GHZ...make sure its not 2.5
6797
Becuase your mobile provider has to pay for a freqency range to use and generally mobile phones are used to recieve more than send. Also if you compare the size of the transmitter/arial and battery in your mobile to a base station transmitter you will see there are also physical reasons why you can't transmit faster.\nFor more details you should look into exactly what system your mobile uses GSM is a very wide-ranging term. You should look up technologies such as code division multiple access and the general packet radio service as well as comparing 2,2.5 and 3g technologies.
692657
wireless application protocols (WAP), 3g, gprs etc... mostly using gigahertz frequencies under environmental health spectrum, around 3.5GHz.... these spectrum also covers radio waves and microwaves, some transmitted via satelites.
29417
General Packet Radio Service (GPRS) is a mobile data service available to users of GSM mobile phones. It is often described as "2.5G", that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused TDMA channels in the GSM network. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that is the only kind of network where GPRS is in use. GPRS is integrated into GSM standards releases starting with Release 97 and onwards. First it was standardised by ETSI but now that effort has been handed onto the 3GPP.
489817
Some where around 300 ghz. Go to www.hamlink/freq.list.html
998173
This is a web page of frequencies. Not sure if it is current.\n\nhttp://mywebpages.comcast.net/sidearm5/freq7.htm
598278
bandwidth, quality and selectivity all these come together when telecommunication comes into act. \nwhether we talk about gsm or cdma bandwidth plays a very important role. everything that is scarce needs very optimal use, and bandwidth is scarce resource today.\nevery country has its own spectrum allocation rules based upon the frequency spectrum allocated for each service by FCC (Federal Communication Commision).\nnow wen we talk bout optimal use of bandwidth specifically in gsm where we are using both TDM + FDM for channel allocation and this is the point (channel allocation) where where the quality comes into play.\nso quality and bandwidth relate with each other as to how efficiently each customer is allocated a channel so as there is no interference or cross talk and there is no call drop, the hand-off takes place successfully and the voice quality is good(atleast).\n\nthere is a Mean Opnion Score(MOS) which judgs the quality of service (QoS) of a service provider\n\n   MOS  --   Inference\n\n    5 -- Voice quality excellent and  no call drops\n    4 -- Voice quality good with very few call drops\n    3 -- Voice quality understandable with few call drops\n    2 -- Voice quality poor with little breaks and more call  drops\n    1 -- Voice quality very poor with many breaks and many call drops\n\nthis is how quality and bandwidth relate with each other when we have have to give best of the services with minimal usage of bandwidth.\n\nand about selectivity, i m not sure u r asking selectivity in which context...if u r asking selectivity of the service providers then it can be based upon the quality of service discussed earlier,\n\nand if u r asking bout the selectivity of which digital cellular system to go for going around the world....\nor u r asking bout to go for GSM or CDMA then obviously both gsm and cdma have their own advantages and disadvantages.\n\nu can mail me at ankit_in_iiitm@yahoo.co.in\n\nAnkit Arora\nB.E.( Electronics and Telecommunication) and MBA (Knowledge Management and IT Enabled Services )
101320
The electromagnetic waves used by cell phones are called radio waves. Waves are characterized by their frequency; that is, the number of times that the wave pattern repeats in a second (or some other time interval). For example, the radio waves that a type of cell phone called a GSM phone use are in frequency bands centered on 850 MHz, 900 MHz, 1800 MHZ and 1900 MHz. That is, the radio waves that a GSM cell phone using the 850 MHz band oscillate roughly 850 million times every second (the pattern repeats 850 million times every second). \n\nThe radio waves that travel back and forth from the cell phone tower to your cell phone are electromagnetic. Your voice signal on the cell phone is carried by modulating electromagnetic waves. No electromagnetic waves, no signal, and therefore, no cell phone.  Without electromagnetic waves, there would be no radio, no tv and no cell phones, and no cordless phones, and no wireless PCs etc etc.\n\nAll light is electromagnetic waves. All heat is electromagnetic waves. Electricity is actually an electromagnetic wave travelling in a wire (the electrons move much slower than this wave). So without electromagnetic waves, the universe would be a very different place.
40129
That's a big subject.  Analog or digital? U.S., Europe, Japan, Germany, Scandanavia, Germany, UK?  All use different systems.  Most use some form of spread spectrum technology, which makes them resistant to jamming.  A good reference is Peterson, Ziemer, and Borth, "Introduction to Spread Spectrum Communications", ISBN 0-02-431623-7.\n\nAlso, see http://en.wikipedia.org/wiki/Cell_phone_jammer\n\n\nFor U.S., "The FCC has fielded enough queries about the legality of cell phone jammers that it issued a notice last year. In it, the agency warns that jammers violate federal laws that broadly prohibit interfering with licensed radio spectrum. Owning, manufacturing, marketing, offering for sale or operating a cell phone jammer is punishable by an $11,000 fine and up to a year in prison for each offense, the notice states."\n\nFrom http://www.newhousenews.com/archive/story1a092200.html
905952
Commercial radio stations transmit signals using two types of schemes.....AM (Amplitude Modulation) and FM (Frequency Modulation).\n\nIn both types of schemes, the voice/music/audio is imposed upon what is known as the carrier wave. This carrier wave is generated at the radio station and has frequency within a certain portion of the range. For example FM radio stations typically have a range of 88 MegaHertz (Million Cycles Per Second) to 108 MegaHertz.\n\nSo, when your station changed from 93.9MegaHertz to 98.3MegaHertz, what they changed is the frequency of the carrier wave.\n\nThe music/voice/audio then is used to modulate (change) this frequency by a pre-determined amount.  Other radio stations are assigned carrier wave frequencies in such a way that two adjacent stations will not broadcast on top of each other.\n\nFor example, since your station now broadcasts on 98.3 MegaHertz frequency, the adjacent stations will be assigned frequencies of 98.5MegaHertz (above your station's frequency) and 98.1 MegaHertz (below your station's frequency).\n\nHope this helps.
1179292
Here is one link: \nhttp://nis.gsmfc.org/nis_factsheet.php?toc_id=140\n\nDo a search on the search bar below and find more. And put some effort urself into your homework :)
280870
In mobile telephony, third-generation protocols support much higher data rates, measured in Mbps, intended for applications other than voice. 3G networks trials started in Japan in 2001. 3G networks are expected to be starting in Europe and part of Asia/Pacific by 2002, and in the US later. 3G will support bandwidth-hungry applications such as full-motion video, video-conferencing and full Internet access. \n\nIn other word you have better surfing and coneectivity options.
586032
Depends what you want to use it for.\n\nGSM - Good for voice... not for data\nCDMA - Good for data... not so good for voice\nGPRS - Too slow for data\n\nTry 3G!!
277573
Uh, no software will make a standard computer without a special radio reception card of some type sensitive to "radio waves".  If you are referring to the Wi-Fi specification, Blue tooth or some other specification, there 'could' be a group of API calls or a Java collection that could allow the specification to work.  Otherwise you are stuck with assembly language or C programs written to take control of a specialized piece of hardware.  All in all, this isn't a real good answer, simply because the question doesn't give enough detail of what you are using and wanting to achieve.  Re state it with more detail and maybe someone can give you a better answer.