Understanding the Differences: CMDA vs TDMA in Cellphone Architectures

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In summary, the conversation discusses the differences between CDMA (code-division multiplexing) and TDMA (time-division multiplexing) in cellphone architectures. Sprint uses CDMA while everyone else, including the international GSM standard, uses TDMA. CDMA uses a pseudo-random sequence to encode the signal, while TDMA allocates different time intervals for each channel to transmit data. TDM becomes inefficient when traffic is intermittent, leading to the development of statistical time division multiplexing. The conversation also mentions a lengthy PDF that provides more information on CDMA and TDMA, and clarifies that Verizon also uses CDMA but it is not cross compatible with other networks.
  • #1
damgo
[SOLVED] CMDA vs TDMA

These are the two cellphone architectures... Sprint uses CDMA (code-division multiplexing) and everyone else uses TDMA (time-division), including the international GSM standard.

My question is, doesn anyone know what the technical difference between the two is? How do they stack up? Can you give any good refs/links? Thanks,

damgo
 
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  • #2
CDMA (Or "spread spectrum") A form of multiplexing where the transmitter encodes the signal using a pseudo-random sequence which the receiver also knows and can use to decode the received signal. Each different random sequence corresponds to a different communication channel.
Taken from; http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?code+division+multiplexing


TDM A type of multiplexing where two or more channels of information are transmitted over the same link by allocating a different time interval ("slot" or "slice") for the transmission of each channel. I.e. the channels take turns to use the link. Some kind of periodic synchronising signal or distinguishing identifier is usually required so that the receiver can tell which channel is which.

TDM becomes inefficient when traffic is intermittent because the time slot is still allocated even when the channel has no data to transmit. Statistical time division multiplexing was developed to overcome this problem.
Taken from; http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?time+division+multiplexing

Here is a rather lengthy PDF (over 100 pages) that has a few pages you might find interesting (In chapter two, I believe);

http://scholar.lib.vt.edu/theses/available/etd-05022000-15590055/unrestricted/CDM_FO_MEMS.pdf
 
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  • #3
i think verizon uses cdma too.

but that doesn't mean that there cross compatable bacause there not.
 

FAQ: Understanding the Differences: CMDA vs TDMA in Cellphone Architectures

What is the difference between CMDA and TDMA?

CDMA (Code Division Multiple Access) and TDMA (Time Division Multiple Access) are two different methods used in cellphone architectures to allow multiple users to share the same frequency spectrum. The main difference between the two is how they divide the frequency spectrum to allocate channels for different users.

Which one is better, CDMA or TDMA?

Both CDMA and TDMA have their own advantages and disadvantages. CDMA allows for a larger number of users to share the same frequency spectrum, while TDMA can provide better call quality and less interference. Ultimately, it depends on the specific needs and priorities of the network and its users.

How does CDMA work?

In CDMA, each user is assigned a unique code that is used to encode their data and transmit it over the same frequency spectrum. The receiver then uses this code to decode the data and reconstruct the original signal. This allows multiple users to transmit and receive data simultaneously without interference.

What is the difference between CDMA and CDMA2000?

CDMA2000 is an advanced version of CDMA that uses a different encoding and modulation technique to achieve higher data transfer rates and better call quality. It also allows for more efficient use of the frequency spectrum and supports more users compared to traditional CDMA.

Is CDMA or TDMA used in modern cellphones?

Both CDMA and TDMA have been used in cellphones in the past, but in modern cellphones, CDMA has largely been replaced by newer technologies such as LTE and 5G. However, some regions and carriers still use CDMA or TDMA for their networks, depending on their infrastructure and customer base.

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