Why Does CDMA Utilize Entire Bandwidth for Multiple Users?

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Discussion Overview

The discussion centers around the utilization of bandwidth in CDMA (Code Division Multiple Access) compared to FDMA (Frequency Division Multiple Access). Participants explore the reasons why CDMA spreads each message over the entire bandwidth allotted rather than using distinct frequency ranges for multiple users, as seen in FDMA. The conversation touches on concepts of capacity, hardware implementation, and signal processing.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why CDMA uses the entire bandwidth for each user instead of assigning separate frequency ranges, suggesting a possible capacity restriction.
  • Another participant responds that implementing both FDMA and CDMA would require additional hardware, implying a trade-off in system complexity.
  • A subsequent reply posits that the increased number of users in a CDMA system could justify the hardware costs associated with its implementation.
  • One participant explains that CDMA allows the use of the entire bandwidth by mixing signals with unique codes, while FDMA allocates different frequencies to users, suggesting both methods effectively utilize available bandwidth but differ in approach.

Areas of Agreement / Disagreement

Participants express varying perspectives on the advantages and trade-offs of CDMA and FDMA. There is no consensus on the optimal approach, and the discussion remains unresolved regarding the implications of hardware requirements and user capacity.

Contextual Notes

Participants do not fully explore the mathematical complexities or practical engineering considerations that may influence the choice between CDMA and FDMA, leaving these aspects open for further discussion.

Who May Find This Useful

Individuals interested in telecommunications, signal processing, or those studying multiple access techniques may find this discussion relevant.

netizen
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Hi!

I've been reading up on FDMA and CDMA and wondering why is it that in CDMA, each message is spread over the entire bandwidth allotted instead of using a single range of frequencies (say, alloted to one user in FDMA), for several users (by assigning a unique code to each of them)?

Why is it that the entire bandwidth is utilised by all users instead of many ranges accomodating several users each? Is the restriction imposed by capacity?

This probably sounds very childish but I'm a greenhorn and would really appreciate some clarification. Thanks in advance...
 
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netizen said:
Why is it that the entire bandwidth is utilised by all users instead of many ranges accomodating several users each?
Because then you would have to implement all the hardware for both systems FDMA and CMDA.

Really they aren't all that different if you think of them in Fourier terms - but that gets a bit mathematically complex
 
Yeah I get that you would then have to implement hardware for both technologies. But won't it be compensated by the fact that the number of users can now be increased manifold?
 
CDMA let's you use the entire bandwidth (all frequenices) by mixing the signals from all the users with a code and then decoding them, FDMA let's you use the entire bandwidth by giving each user a different frequency.
They both fill the available bandwidth, so other than signal-noise and practical engineering considerations they are equivalent.
 

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