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a few questions about TDMA... |
EastCoastStar
Joined: Dec 07, 2003
Posts: > 500
From: orlando fl US
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Heyy all.
Recently, I have heard more and more about TDMA (Time Division Multiple Access). I was on a site that was explaining it, but confused me a little. It still uses GSM somehow? and I saw something that said Cingular has GSM and TDMA. and CDMA and TDMA are somehow closley related also?
I'm sorry, but I got confused :-. can anyone clear a few things up about TDMA?
Is TDMA getting to be popular?!
[ This Message was edited by: EastCoastStar on 2005-11-28 16:46 ] |
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whizkidd
Joined: May 14, 2004
Posts: > 500
From: India
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TDMA (time division multiple access) i believe is used by the us military.. It basically allots a single frequency for multiple calls and data channels..
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niranjan007
Joined: Dec 12, 2004
Posts: 230
From: The garden city of India
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Its similar to multitasking on a pc. The same processor allots time slices for different tasks. In tdma, each phone is given a fraction of a second's time to transmit/receive on the common frequency. So number of calls that can be made simultaneously depends not on the number of available frequencies but on the processing power of the network. |
EastCoastStar
Joined: Dec 07, 2003
Posts: > 500
From: orlando fl US
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that makes sence. So its not for everyday use? (i mean, for everyday people). Has anyone actually used TDMA here? I doubt it... but just wanted to know how it is haha. Must be pretty good and stable.
thanks for the info!
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701
Joined: Nov 26, 2002
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From: Romania
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Hmmm,I just wrote that 2 years ago here somewhere.TDMA is the base technology for ALL mobile comunications. It's an analogical system. When Qualcomm invented the digital mobile comunications, thet split the comunications into bits on several channels at the same time but based ON existing TDMA technology. What CDMA brought was digital comunications meaning it's more stable and less susceptible of intercepting thus offering com security.CDMA was used by the US Military until the 70s when Qualcomm bought the rights to use it in civil markets. After that,in Europe they thought of having a standard comunications system so they've made GSM which is also digital and comparable to CDMA.I'll come back tomorrow with more info.
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mrao
Joined: Nov 11, 2004
Posts: > 500
From: Mumbai, India
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If im not mistaken, some japanese operators are already using the tdma standard.
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701
Joined: Nov 26, 2002
Posts: > 500
From: Romania
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Read this also:
http://en.wikipedia.org/wiki/TDMA
Time division multiple access (TDMA) is digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference by allocating unique time slots to each user within each channel. The TDMA digital transmission scheme multiplexes three signals over a single channel. The current TDMA standard for cellular divides a single channel into six time slots, with each signal using two slots, providing a 3 to 1 gain in capacity over advanced mobile-phone service (AMPS). Each caller is assigned a specific time slot for transmission.
The wireless industry began to explore converting the existing analog network to digital as a means of improving capacity back in the late 1980s. In 1989, the Cellular Telecommunications Industry Association (CTIA) chose TDMA over Motorola’s frequency division multiple access (FDMA) (today known as narrowband analog mobile-phone service [NAMPS]) narrowband standard as the technology of choice for existing 800 MHz cellular markets and for emerging 1.9-GHz markets. With the growing technology competition applied by Qualcomm in favor of code division multiple access (CDMA) and the realities of the European global system for mobile communications (GSM) standard, the CTIA decided to let carriers make their own technology selection.
The two major (competing) systems that split the RF are TDMA and CDMA. CDMA is a spread-spectrum technology that allows multiple frequencies to be used simultaneously. CDMA codes every digital packet it sends with a unique key. A CDMA receiver responds only to that key and can pick out and demodulate the associated signal.
Because of its adoption by the European standard GSM, the Japanese Digital Cellular (JDC), and North American Digital Cellular (NADC), TDMA and its variants are currently the technology of choice throughout the world. However, over the last few years, a debate has convulsed the wireless community over the respective merits of TDMA and CDMA.
The TDMA system is designed for use in a range of environments and situations, from hand portable use in a downtown office to a mobile user traveling at high speed on the freeway. The system also supports a variety of services for the end user, such as voice, data, fax, short message services, and broadcast messages. TDMA offers a flexible air interface, providing high performance with respect to capacity, coverage, and unlimited support of mobility and capability to handle different types of user needs.
Time Division Multiple Access (TDMA)
1. The Digital Advantage
All multiple access techniques depend on the adoption of digital technology. Digital technology is now the standard for the public telephone system where all analog calls are converted to digital form for transmission over the backbone. Digital has a number of advantages over analog transmission:
It economizes on bandwidth.
It allows easy integration with personal communication systems (PCS) devices. (redundant technology used in the USA and some parts of Asia only).
It maintains superior quality of voice transmission over long distances.
It is difficult to decode.
It can use lower average transmitter power.
It enables smaller and less expensive individual receivers and transmitters.
It offers voice privacy.
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[ This Message was edited by: 701 on 2005-11-30 06:45 ] |
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Posted: 2005-11-28 17:39
