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Telecom Resources - CDMA |
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SS7,
GSM, CDMA, 3G, IN Information
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CDMA is a form of Direct Sequence Spread Spectrum communications. In general, Spread Spectrum communications is distinguished by three key elements:
1. The signal occupies a bandwidth much greater than that which is necessary to send the information. This results in many benefits, such as immunity to interference and jamming and multi-user access, which we’ll discuss later on.
2. The bandwidth is spread by means of a code which is independent of the data. The independence of the code distinguishes this from standard modulation schemes in which the data modulation will always spread the spectrum somewhat.
3. The receiver synchronizes to the code to recover the data. The use of an independent code and synchronous reception allows multiple users to access the same frequency band at the same time.
In order to protect the signal, the code used is pseudo-random. It appears random, but is actually deterministic, so that the receiver can reconstruct the code for synchronous detection. This pseudo-random code is also called pseudo-noise (PN).
Spread-spectrum radio communications, long a favorite technology of the military because it resists jamming and is hard for an enemy to intercept, is now on the verge of potentially explosive commercial development. The reason: spread-spectrum signals, which are distributed over a wide range of frequencies and then collected onto their original frequency at the receiver, are so inconspicuous as to be 'transparent.' Just as they are unlikely to be intercepted by a military opponent, so are they unlikely to interfere with other signals intended for business and consumer users -- even ones transmitted on the same frequencies. Such an advantage opens up crowded frequency spectra to vastly expanded use.
Cdma2000 specification was developed by the Third Generation Partnership Project 2 (3GPP2), a partnership consisting of five telecommunications standards bodies: ARIB and TTC in Japan, CWTS in China, TTA in Korea and TIA in North America. Cdma2000 has already been implemented to several networks as an evolutionary step from cdmaOne as cdma2000 provides full backward compatibility with IS-95B. Cdma2000 is not constrained to only the IMT-2000 band, but operators can also overlay acdma2000 1x system, which supports 144 kbps now and data rates up to 307 kbps in the future, on top of their existing cdmaOne network.
CDMA / Spread Spectrum Resources:
Introduction to CDMA
ABCs of Spread Sprectum
CDMA Technology
CDMA Basics
CDMA2000
IEC WCDMA
Overview of CDMA
CDMA vs TDMA
NEW ON THIS SITE:
MVNO: is a GSM phenomenon where an operator or company which does not own a licenced sprectrum and generally with own networking infrastructure. Instead MVNOs resell wireless services under their brand name, using a regular telecom operator's network with which they have a business arrangements. Usually they they buy minutes of use (MOU) from the licenced telecom operator and then resell minutes of usage to their customers of MVNO. Currently MVNOs are emerging in fast pace in European markets and beginning in USA also. Slowly MVNO phenomenon catching up in Asia and other parts of the world also.
READ MORE HERE
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